diff --git a/en_US.ISO8859-1/books/arch-handbook/mac/chapter.sgml b/en_US.ISO8859-1/books/arch-handbook/mac/chapter.sgml index dae0ee52be..b6f82c56df 100644 --- a/en_US.ISO8859-1/books/arch-handbook/mac/chapter.sgml +++ b/en_US.ISO8859-1/books/arch-handbook/mac/chapter.sgml @@ -1,5681 +1,5681 @@ Chris Costello TrustedBSD Project
chris@FreeBSD.org
 Robert Watson TrustedBSD Project
rwatson@FreeBSD.org
 Writing MAC Policies Synopsis MAC, or Mandatory Access Control, is a feature introduced by the TrustedBSD Project to supplement the existing standard DAC - (Discreationary Access Control) policies of BSD Unix systems. + (Discretionary Access Control) policies of BSD Unix systems. This chapter introduces the MAC policy framework and provides documentation for a sample MAC policy module. Introduction The TrustedBSD MAC framework provides a mechanism to allow the compile-time or run-time extension of the kernel access control model. New system policies may be implemented as kernel modules and linked to the kernel; if multiple policy modules are present, their results will be composed. While the framework is intended to support a variety of access control models, its design was derived from the requirements of a set of specific access control models required for the TrustedBSD and CBOSS Projects. This includes support for fixed and floating label Biba integrity policies, the MLS confidentiality policy, the Type Enforcement rule-based access control policy, and the ability to support layering of the NSA FLASK framework above the TrustedBSD MAC framework. This document describes the rough architecture of the framework, with the understanding that this is a work-in-progress and may change subtantially as requirements evolve. Kernel Architecture The TrustedBSD MAC framework provides the opportunity for policy modules to be augment system access control decisions. Policies are permitted the opportunity to restrict the set of rights available for processes at a variety of relevant points in the kernel. In addition, they are provided the opportunity to tag processes and various kernel objects with labels storing access control information. Policy modules may register interest in a subset of the total available events or objects, and are not required to implement events or objects that are not relevant to the policy. Multiple modules may be loaded at once, and the results of the modules are composed as necessary to build an over-all system policy. Policy modules may be implemented such that they can be loaded on-demand at run-time, or such that they may only be loaded early in the boot process. This permits policies requiring pervasive labeling of all objects to prevent improper use. Userland Architecture ... Entry Point Framework Four classes of entry points are offered to policies registered with the framework: entry points associated with the registration and management of policies, entry points denoting initialization, creation, destruction, and other life cycle events for kernel objects, events assocated with access control decisions that the policy module may influence, and calls associated with the management of labels on objects. In addition, a mac_syscall() entry point is provided so that policies may extend the kernel interface without registering new system calls. Policy module writers should be aware of the kernel locking strategy, as well as what object locks are available during which entry points. Writers should attempt to avoid deadlock scenarios by avoiding grabbing non-leaf locks inside of entry points, and also follow the locking protocol for object access and modification. In particular, writers should be aware that while necessary locks to access objects and their labels are generally held, sufficient locks to modify an object or its label may not be present for all entry points. Locking information for arguments is documented in the MAC framework entry point document. Policy entry points will pass a reference to the object label along with the object itself. This permits labeled policies to be unaware of the internals of the object yet still make decisions based on the label. The exception to this is the process credential, which is assumed to be understood by policies as a first class security object in the kernel. Policies that do not implement labels on kernel objects will be passed NULL pointers for label arguments to entry points. Policy Module Registration Modules may be declared using the MAC_POLICY_SET() macro, which names the policy, provides a reference to the MAC entry point vector, provides load-time flags determining how the policy framework should handle the policy, and optionally requests the allocation of label state by the framework: static struct mac_policy_op_entry mac_none_ops[] = { { MAC_DESTROY, (macop_t)mac_none_destroy }, { MAC_INIT, (macop_t)mac_none_init }, { MAC_INIT_BPFDESC, (macop_t)mac_none_init_bpfdesc }, /* ... */ { MAC_CHECK_VNODE_STAT, (macop_t)mac_none_check_vnode_stat }, { MAC_CHECK_VNODE_WRITE, (macop_t)mac_none_check_vnode_write }, { MAC_OP_LAST, NULL } }; The MAC policy entry point vector, mac_none_ops in this example, associates functions defined in the module with specific entry points. A complete listing of available entry points and their prototypes may be found in the MAC entry point reference section. Of specific interest during module registration are the MAC_DESTROY and MAC_INIT entry points. MAC_INIT will be invoked once a policy is successfully registered with the module framework but prior to any other entry points becoming active. This permits the policy to perform any policy-specific allocation and initialization, such as initialization of any data or locks. MAC_DESTROY will be invoked when a policy module is unloaded to permit releasing of any allocated memory and destruction of locks. Currently, these two entry points are invoked with the MAC policy list mutex held to prevent any other entry points from being invoked: this will be changed, but in the mean time, policies should be careful about what kernel primitives they invoke so as to avoid lock ordering or sleeping problems. The policy declaration's module name field exists so that the module may be uniquely identified for the purposes of module dependencies. An appropriate string should be selected. The full string name of the policy is displayed to the user via the kernel log during load and unload events, and also exported when providing status information to userland processes. The policy flags field permits the module to provide the framework with information about its loader-related capabilities. Currently, two flags are defined: MPC_LOADTIME_FLAG_UNLOADOK This flag indicates that the policy module may be unloaded. If this flag is not provided, then the policy framework will reject requests to unload the module. This flag might be used by modules that allocate label state and are unable to free that state at runtime. MPC_LOADTIME_FLAG_NOTLATE This flag indicates that the policy module must be loaded and initialized early in the boot process. If the flag is specified, attempts to register the module following boot will be rejected. The flag may be used by policies that require pervasive labeling of all system objects, and cannot handle objects that have not been properly initialized by the policy. <function>&mac.mpo;_init</function void &mac.mpo;_init struct mac_policy_conf *conf &mac.thead; conf MAC policy definition Policy load event. The policy list mutex is held, so caution should be applied. <function>&mac.mpo;_destroy</function> void &mac.mpo;_destroy struct mac_policy_conf *conf &mac.thead; conf MAC policy definition Policy load event. The policy list mutex is held, so caution should be applied. Label Events This class of entry points is used by the MAC framework to permit policies to maintain label information on kernel objects. For each labeled kernel object of interest to a MAC policy, entry points may be registered for relevant life cycle events. All objects implement initialization, creation, and destruction hooks. Some objects will also implement relabeling, allowing user processes to change the labels on objects. Some objects will also implement object-specific events, such as label events associated with IP reassembly. A typical labeled object will have the following life cycle of entry points: Label initialization o (object-specific wait) \ Label creation o \ Relabel events, o--<--. Various object-specific, | | Access control events ~-->--o \ Label destruction o Label initialization permits policies to allocate memory and set initial values for labels without context for the use of the object. The label slot allocated to a policy will be zero'd by default, so some policies may not need to perform initialization. Label creation occurs when the kernel structure is associated with an actual kernel object. For example, mbufs may be allocated and remain unused in a pool until they are required. mbuf allocation causes label initialization on the mbuf to take place, but mbuf creation occurs when the mbuf is associated with a datagram. Typically, context will be provided for a creation event, including the circumstances of the creation, and labels of other relevant objects in the creation process. For example, when an mbuf is created from a socket, the socket and its label will be presented to registered policies in addition to the new mbuf and its label. Memory allocation in creation events is discouraged, as it may occur in performance sensitive ports of the kernel; in addition, creation calls are not permitted to fail so a failure to allocate memory cannot be reported. Object specific events do not generally fall into the other broad classes of label events, but will generally provide an opportunity to modify or update the label on an object based on additional context. For example, the label on an IP fragment reassembly queue may be updated during the MAC_UPDATE_IPQ entry point as a result of the acceptance of an additional mbuf to that queue. Access control events are discussed in detail in the following section. Label destruction permits policies to release storage or state associated with a label during its association with an object so that the kernel data structures supporting the object may be reused or released. In addition to labels associated with specific kernel objects, an additional class of labels exists: temporary labels. These labels are used to store update information submitted by user processes. These labels are initialized and destroyed as with other label types, but the creation event is MAC_INTERNALIZE, which accepts a user label to be converted to an in-kernel representation. File System Object Labeling Event Operations <function>&mac.mpo;_create_devfs_device</function> void &mac.mpo;_create_devfs_device dev_t dev struct devfs_dirent *devfs_dirent struct label *label &mac.thead; dev Device corresponding with devfs_dirent devfs_dirent Devfs directory entry to be labeled. label Label for devfs_dirent to be filled in. Fill out the label on a devfs_dirent being created for the passed device. This call will be made when the device file system is mounted, regenerated, or a new device is made available. <function>&mac.mpo;_create_devfs_directory</function> void &mac.mpo;_create_devfs_directory char *dirname int dirnamelen struct devfs_dirent *devfs_dirent struct label *label &mac.thead; dirname Name of directory being created namelen Length of string dirname devfs_dirent Devfs directory entry for directory being created. Fill out the label on a devfs_dirent being created for the passed directory. This call will be made when the device file system is mounted, regenerated, or a new device requiring a specific directory hierarchy is made available. <function>&mac.mpo;_create_devfs_vnode</function> void &mac.mpo;_create_devfs_vnode struct devfs_dirent *devfs_dirent struct label *direntlabel struct vnode *vp struct label *vnodelabel &mac.thead; devfs_dirent Object; devfs directory entry direntlabel Policy label for devfs_dirent vp Object; file system object being labeled vnodelabel Policy label to be filled in for vp Fill out the label on the vnode being created for the passed devfs_dirent. This call will be made when a vnode is required to represent the specified devfs_dirent in a mounted devfs instance. <function>&mac.mpo;_vnode_create_from_vnode</function> void &mac.mpo;_vnode_create_from_vnode struct ucred *cred struct vnode *parent struct label *parentlabel struct vnode *child struct label *childlabel &mac.thead; cred Subject credential parent Parent vnode; the directory in which child is being created parentlabel Policy label for parent child New vnode childlabel Label to be filled in for child Fill out the label on the vnode being created in the passed vnode parent by the passed subject credential. This call will be made when a vnode is allocated during a vnode creation operation. For example, this call is made by multi-label file systems during the creation of a new file or directory. <function>&mac.mpo;_create_mount</function> void &mac.mpo;_create_mount struct ucred *cred struct mount *mp struct label *mnt struct label *fslabel &mac.thead; cred Subject credential mp Object; file system being mounted mntlabel Policy label to be filled in for mp fslabel Policy label for the file system mp mounts. Fill out the labels on the mount point being created by the passed subject credential. This call will be made when a new file system is mounted. <function>&mac.mpo;_create_root_mount</function> void &mac.mpo;_create_root_mount struct ucred *cred struct mount *mp struct label *mntlabel struct label *fslabel &mac.thead; See . Fill out the labels on the mount point being created by the passed subject credential. This call will be made when the root file system is mounted, after &mac.mpo;_create_mount;. <function>&mac.mpo;_vnode_relabel</function> void &mac.mpo;_vnode_relabel struct ucred *cred struct vnode *vp struct label *vnodelabel struct label *newlabel &mac.thead; cred Subject credential vp vnode to relabel vnodelabel Existing policy label for vp newlabel New, possibly partial label to replace vnodelabel Update the label on the passed vnode given the passed update vnode label and the passed subject credential. <function>&mac.mpo;_stdcreatevnode_ea</function> int &mac.mpo;_stdcreatevnode_ea struct vnode *vp struct label *vnodelabel &mac.thead; vp vnode to commit Locked on entry, locked on exit vnodelabel Label associated with vp This entry point is called when a vnode is to be committed to disk via the extended attribute service (see &man.extattr.9;). If committing to the disk is successful, a value of 0 should be returned; otherwise, an appropriate error code should be returned. The current implementation as of July 24, 2002 commits the data to disk from within the architecture. The implementation will be updated to be closer to the above documentation as development progresses. <function>&mac.mpo;_update_devfsdirent</function> void &mac.mpo;_update_devfsdirent struct devfs_dirent *devfs_dirent struct label *direntlabel struct vnode *vp struct label *vnodelabel &mac.thead; devfs_dirent Object; devfs directory entry direntlabel Policy label for devfs_dirent to be updated. vp Parent vnode Locked vnodelabel Policy label for vp Update the devfs_dirent label from the passed devfs vnode label. This call will be made when a devfs vnode has been successfully relabeled to commit the label change such that it lasts even if the vnode is recycled. It will also be made when when a symlink is created in devfs, following a call to mac_vnode_create_from_vnode to initialize the vnode label. <function>&mac.mpo;_update_procfsvnode</function> void &mac.mpo;_update_procfsvnode struct vnode *vp struct label *vnodelabel struct ucred *cred &mac.thead; vp Object; procfs vnode Locked vnodelabel Policy label to be filled in for vp cred Subject; credential for the process entry Immutable Update the procfs vnode label from the passed subject credential. This call will be made when an operation on a procfs vnode requires a fresh label on a process-derived vnode. <function>&mac.mpo;_update_vnode_from_extattr</function> int &mac.mpo;_update_vnode_from_extattr struct vnode *vp struct label *vnodelabel struct mount *mp struct label *fslabel &mac.thead; vp Object; vnode whose label is being updated Locked vnodelabel Policy label to refresh mp Mount point for vp fslabel Policy label for vp's file system. Update the vnode label by refreshing the label data from the extended attribute service for the vnode. The mount point fslabel is also made available so that the fslabel may be used as a labeling source if fallback is appropriate for the policy. This call is permitted to fail; if the call fails, the associated label refresh will also fail, causing the failure of the operation requiring the MAC check and vnode label refresh, permitting a fail closed policy if labeling data is not available. <function>&mac.mpo;_update_from_externalized</function> int &mac.mpo;_update_from_externalized struct vnode *vp struct label *vnodelabel struct mac *extmac &mac.thead; vp Object; vnode Locked vnodelabel Policy label for vp extmac Externalized MAC policy label Update the vnode label from the passed externalized label loaded from disk by the MAC framework. This call is permitted to fail; if the call fails, the associated label refresh will also fail, causing the failure of the operation requiring the MAC check and vnode label refresh, permitting a fail closed policy if labeling data is not available. This call will be obsoleted by the new extended attribute labeling interface. <function>&mac.mpo;_update_vnode_from_mount</function> void &mac.mpo;_update_vnode_from_mount struct vnode *vp struct label *vnodelabel struct mount *mp struct label *mountlabel &mac.thead; vp Object; vnode Locked vnodelabel Policy label for vp mp Mount point where vp resides fslabel Policy label for the file system where vp resides. Update the vnode label from the passed mount point label. This call is made when a single label file system vnode requires a label, or if the obsoleted MAC framework externalized extended attribute read fails. IPC Object Labeling Event Operations <function>&mac.mpo;_create_mbuf_from_socket</function> void &mac.mpo;_create_mbuf_from_socket struct socket *so struct label *socketlabel struct mbuf *m struct label *mbuflabel &mac.thead; socket Socket Socket locking WIP socketlabel Policy label for socket m Object; mbuf mbuflabel Policy label to fill in for m Set the label on a newly created mbuf header from the passed socket label. This call is made when a new datagram or messsage is generated by the socket and stored in the passed mbuf. <function>&mac.mpo;_create_socket</function> void &mac.mpo;_create_socket struct ucred *cred struct socket *so struct label *socketlabel &mac.thead; cred Subject credential Immutable so Object; socket to label socketlabel Label to fill in for so Set the label on a newly created socket from the passed subject credential. This call is made when a socket is created. <function>&mac.mpo;_create_socket_from_socket</function> void &mac.mpo;_create_socket_from_socket struct socket *oldsocket struct label *oldsocketlabel struct socket *newsocket struct label *newsocketlabel &mac.thead; oldsocket Object; parent socket; created from &man.listen.2; oldsocketlabel Label for oldsocket newsocket Object; child socket; incoming connection newsocketlabel Label to be filled in for newsocket Set the label on a newly created stream socket from the passed listen socket. This call may occur during &man.accept.2;, or prior to &man.accept.2;, depending on the protocol. <function>&mac.mpo;_socket_relabel</function> void &mac.mpo;_socket_relabel struct ucred *cred struct socket *so struct label *oldlabel struct label *newlabel &mac.thead; cred Subject credential Immutable so Object; socket oldlabel Current label for so newlabel Label update for so Update the label on a socket from the passed socket label update. <function>&mac.mpo;_set_socket_peer_from_mbuf</function> void &mac.mpo;_set_socket_peer_from_mbuf struct mbuf *mbuf struct label *mbuflabel struct label *oldlabel struct label *newlabel &mac.thead; mbuf First datagram received over socket mbuflabel Label for mbuf oldlabel Current label for the socket newlabel Policy label to be filled out for the socket Set the peer label on a stream socket from the passed mbuf label. This call will be made when the first datagram is received by the stream socket, with the exception of Unix domain sockets. <function>&mac.mpo;_set_socket_peer_from_socket</function> void &mac.mpo;_set_socket_peer_from_socket struct socket *oldsocket struct label *oldsocketlabel struct socket *newsocket struct label *newsocketpeerlabel &mac.thead; oldsocket Local socket oldsocketlabel Policy label for oldsocket newsocket Peer socket newsocketpeerlabel Policy label to fill in for newsocket Set the peer label on a stream UNIX domain socket from the passed remote socket endpoint. This call will be made when the socket pair is connected, and will be made for both endpoints. Network Object Labeling Event Operations <function>&mac.mpo;_create_bpfdesc</function> void &mac.mpo;_create_bpfdesc struct ucred *cred struct bpf_d *bpf_d struct label *bpflabel &mac.thead; cred Subject credential Immutable bpf_d Object; bpf descriptor bpf Policy label to be filled in for bpf_d Set the label on a newly created BPF descriptor from the passed subject credential. This call will be made when a BPF device node is opened by a process with the passed subject credential. <function>&mac.mpo;_create_ifnet</function> void &mac.mpo;_create_ifnet struct ifnet *ifnet struct label *ifnetlabel &mac.thead; ifnet Network interface ifnetlabel Policy label to fill in for ifnet Set the label on a newly created interface. This call may be made when a new physical interface becomes available to the system, or when a pseudo-interface is instantiated during the boot or as a result of a user action. <function>&mac.mpo;_create_ipq</function> void &mac.mpo;_create_ipq struct mbuf *fragment struct label *fragmentlabel struct ipq *ipq struct label *ipqlabel &mac.thead; fragment First received IP fragment fragmentlabel Policy label for fragment ipq IP reassembly queue to be labeled ipqlabel Policy label to be filled in for ipq Set the label on a newly created IP fragment reassembly queue from the mbuf header of the first received fragment. <function>&mac.mpo;_create_datagram_from_ipq</function> void &mac.mpo;_create_create_datagram_from_ipq struct ipq *ipq struct label *ipqlabel struct mbuf *datagram struct label *datagramlabel &mac.thead; ipq IP reassembly queue ipqlabel Policy label for ipq datagram Datagram to be labeled datagramlabel Policy label to be filled in for datagramlabel Set the label on a newly reassembled IP datagram from the IP fragment reassembly queue from which it was generated. <function>&mac.mpo;_create_fragment</function> void &mac.mpo;_create_fragment struct mbuf *datagram struct label *datagramlabel struct mbuf *fragment struct label *fragmentlabel &mac.thead; datagram Datagram datagramlabel Policy label for datagram fragment Fragment to be labeled fragmentlabel Policy label to be filled in for datagram Set the label on the mbuf header of a newly created IP fragment from the label on the mbuf header of the datagram it was generate from. <function>&mac.mpo;_create_mbuf_from_mbuf</function> void &mac.mpo;_create_mbuf_from_mbuf struct mbuf *oldmbuf struct label *oldmbuflabel struct mbuf *newmbuf struct label *newmbuflabel &mac.thead; oldmbuf Existing (source) mbuf oldmbuflabel Policy label for oldmbuf newmbuf New mbuf to be labeled newmbuflabel Policy label to be filled in for newmbuf Set the label on the mbuf header of a newly created datagram from the mbuf header of an existing datagram. This call may be made in a number of situations, including when an mbuf is re-allocated for alignment purposes. <function>&mac.mpo;_create_mbuf_linklayer</function> void &mac.mpo;_create_mbuf_linklayer struct ifnet *ifnet struct label *ifnetlabel struct mbuf *mbuf struct label *mbuflabel &mac.thead; ifnet Network interface ifnetlabel Policy label for ifnet mbuf mbuf header for new datagram mbuflabel Policy label to be filled in for mbuf Set the label on the mbuf header of a newly created datagram generated for the purposes of a link layer response for the passed interface. This call may be made in a number of situations, including for ARP or ND6 responses in the IPv4 and IPv6 stacks. <function>&mac.mpo;_create_mbuf_from_bpfdesc</function> void &mac.mpo;_create_mbuf_from_bpfdesc struct bpf_d *bpf_d struct label *bpflabel struct mbuf *mbuf struct label *mbuflabel &mac.thead; bpf_d BPF descriptor bpflabel Policy label for bpflabel mbuf New mbuf to be labeled mbuflabel Policy label to fill in for mbuf Set the label on the mbuf header of a newly created datagram generated using the passed BPF descriptor. This call is made when a write is performed to the BPF device associated with the passed BPF descriptor. <function>&mac.mpo;_create_mbuf_from_ifnet</function> void &mac.mpo;_create_mbuf_from_ifnet struct ifnet *ifnet struct label *ifnetlabel struct mbuf *mbuf struct label *mbuflabel &mac.thead; ifnet Network interface ifnetlabel Policy label for ifnetlabel mbuf mbuf header for new datagram mbuflabel Policy label to be filled in for mbuf Set the label on the mbuf header of a newly created datagram generated from the passed network interface. <function>&mac.mpo;_create_mbuf_multicast_encap</function> void &mac.mpo;_create_mbuf_multicast_encap struct mbuf *oldmbuf struct label *oldmbuflabel struct ifnet *ifnet struct label *ifnetlabel struct mbuf *newmbuf struct label *newmbuflabel &mac.thead; oldmbuf mbuf header for existing datagram oldmbuflabel Policy label for oldmbuf ifnet Network interface ifnetlabel Policy label for ifnet newmbuf mbuf header to be labeled for new datagram newmbuflabel Policy label to be filled in for newmbuf Set the label on the mbuf header of a newly created datagram generated from the existing passed datagram when it is processed by the passed multicast encapsulation interface. This call is made when an mbuf is to be delivered using the virtual interface. <function>&mac.mpo;_create_mbuf_netlayer</function> void &mac.mpo;_create_mbuf_netlayer struct mbuf *oldmbuf struct label *oldmbuflabel struct mbuf *newmbuf struct label *newmbuflabel &mac.thead; oldmbuf Received datagram oldmbuflabel Policy label for oldmbuf newmbuf Newly created datagram newmbuflabel Policy label for newmbuf Set the label on the mbuf header of a newly created datagram generated by the IP stack in response to an existing received datagram (oldmbuf). This call may be made in a number of situations, including when responding to ICMP request datagrams. <function>&mac.mpo;_fragment_match</function> int &mac.mpo;_fragment_match struct mbuf *fragment struct label *fragmentlabel struct ipq *ipq struct label *ipqlabel &mac.thead; fragment IP datagram fragment fragmentlabel Policy label for fragment ipq IP fragment reassembly queue ipqlabel Policy label for ipq Determine whether an mbuf header containing an IP datagram (fragment) fragment matches the label of the passed IP fragment reassembly queue (ipq). Return (1) for a successful match, or (0) for no match. This call is made when the IP stack attempts to find an existing fragment reassembly queue for a newly received fragment; if this fails, a new fragment reassembly queue may be instantiated for the fragment. Policies may use this entry point to prevent the reassembly of otherwise matching IP fragments if policy does not permit them to be reassembled based on the label or other information. <function>&mac.mpo;_ifnet_relabel</function> void &mac.mpo;_ifnet_relabel struct ucred *cred struct ifnet *ifnet struct label *ifnetlabel struct label *newlabel &mac.thead; cred Subject credential ifnet Object; Network interface ifnetlabel Policy label for ifnet newlabel Label update to apply to ifnet Update the label of network interface, ifnet, based on the passed update label, newlabel, and the passed subject credential, cred. <function>&mac.mpo;_update_ipq</function> void &mac.mpo;_update_ipq struct mbuf *fragment struct label *fragmentlabel struct ipq *ipq struct label *ipqlabel &mac.thead; mbuf IP fragment mbuflabel Policy label for mbuf ipq IP fragment reassembly queue ipqlabel Policy label to be updated for ipq Update the label on an IP fragment reassembly queue (ipq) based on the acceptance of the passed IP fragment mbuf header (mbuf). Process Labeling Event Operations <function>&mac.mpo;_create_cred</function> void &mac.mpo;_create_cred struct ucred *parent_cred struct ucred *child_cred &mac.thead; parent_cred Parent subject credential child_cred Child subject credential Set the label of a newly created subject credential from the passed subject credential. This call will be made when crcopy(9) is invoked on a newly created struct ucred. This call should not be confused with a process forking or creation event. <function>&mac.mpo;_execve_transition</function> void &mac.mpo;_execve_transition struct ucred *old struct ucred *new struct vnode *vp struct label *vnodelabel &mac.thead; old Existing subject credential Immutable new New subject credential to be labeled vp File to execute Locked vnodelabel Policy label for vp Update the label of a newly created subject credential (new) from the passed existing subject credential (old) based on a label transition caused by executing the passed vnode (vp). This call occurs when a process executes the passed vnode and one of the policies returns a success from the mpo_execve_will_transition entry point. Policies may choose to implement this call simply by invoking mpo_create_cred and passing the two subject credentials so as not to implement a transitioning event. Policies should not leave this entry point unimplemented if they implement mpo_create_cred, even if they do not implement mpo_execve_will_transition. <function>&mac.mpo;_execve_will_transition</function> int &mac.mpo;_execve_will_transition struct ucred *old struct vnode *vp struct label *vnodelabel &mac.thead; old Subject credential prior to &man.execve.2; Immutable vp File to execute vnodelabel Policy label for vp Determine whether the policy will want to perform a transition event as a result of the execution of the passed vnode by the passed subject credential. Return 1 if a transition is required, 0 if not. Even if a policy returns 0, it should behave correctly in the presence of an unexpected invocation of mpo_execve_transition, as that call may happen as a result of another policy requesting a transition. <function>&mac.mpo;_create_proc0</function> void &mac.mpo;_create_proc0 struct ucred *cred &mac.thead; cred Subject credential to be filled in Create the subject credential of process 0, the parent of all kernel processes. <function>&mac.mpo;_create_proc1</function> void &mac.mpo;_create_proc1 struct ucred *cred &mac.thead; cred Subject credential to be filled in Create the subject credential of process 1, the parent of all kernel processes. <function>&mac.mpo;_cred_relabel</function> void &mac.mpo;_cred_relabel struct ucred *cred struct label *newlabel &mac.thead; cred Subject credential newlabel Label update to apply to cred Update the label on a subject credential from the passed update label. Access Control Checks Access control entry points permit policy modules to influence access control decisions made by the kernel. Generally, although not always, arguments to an access control entry point will include one or more authorizing credentials, information (possibly including a label) for any other objects involved in the operation. An access control entry point may return 0 to permit the operation, and an &man.errno.2; error value. The results of invoking the entry point across various registered policy modules will be composed as follows: if all modules permit the operation to succeed, success will be returned. If one or modules returns a failure, a failure will be returned. If more than one module returns a failure, the errno value to return to the user will be selected using the following precedence, implemented by the error_select() function in kern_mac.c: Most precedence EDEADLK EINVAL ESRCH EACCES Least precedence EPERM If none of the error values returned by all modules are listed in the precedence chart then an arbitrarily selected value from the set will be returned. In general, the rules provide precedence to errors in the following order: kernel failures, invalid arguments, object not present, access not permitted, other. <function>&mac.mpo;_check_bpfdesc_receive</function> int &mac.mpo;_check_bpfdesc_receive struct bpf_d *bpf_d struct label *bpflabel struct ifnet *ifnet struct label *ifnetlabel &mac.thead; bpf_d Subject; BPF descriptor bpflabel Policy label for bpf_d ifnet Object; network interface ifnetlabel Policy label for ifnet Determine whether the MAC framework should permit datagrams from the passed interface to be delivered to the buffers of the passed BPF descriptor. Return (0) for success, or an errno value for failure Suggested failure: EACCES for label mismatches, EPERM for lack of privilege. <function>&mac.mpo;_check_socket_bind</function> int &mac.mpo;_check_socket_bind struct ucred *cred struct socket *socket struct label *socketlabel struct sockaddr *sockaddr &mac.thead; cred Subject credential socket Socket to be bound socketlabel Policy label for socket sockaddr Address of socket <function>&mac.mpo;_check_socket_connect</function> int &mac.mpo;_check_socket_connect struct ucred *cred struct socket *socket struct label *socketlabel struct sockaddr *sockaddr &mac.thead; cred Subject credential socket Socket to be connected socketlabel Policy label for socket sockaddr Address of socket Determine whether the subject credential (cred) can connect the passed socket (socket) to the passed socket address (sockaddr). Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches, EPERM for lack of privilege. <function>&mac.mpo;_check_cred_visible</function> int &mac.mpo;_check_cred_visible struct ucred *u1 struct ucred *u2 &mac.thead; u1 Subject credential u2 Object credential Determine whether the subject credential u1 can see other subjects with the passed subject credential u2. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches, EPERM for lack of privilege, or ESRCH to hide visibility. This call may be made in a number of situations, including inter-process status sysctls used by ps, and in procfs lookups. <function>&mac.mpo;_check_socket_visible</function> int &mac.mpo;_check_socket_visible struct ucred *cred struct socket *socket struct label *socketlabel &mac.thead; cred Subject credential socket Object; socket socketlabel Policy label for socket <function>&mac.mpo;_check_ifnet_relabel</function> int &mac.mpo;_check_ifnet_relabel struct ucred *cred struct ifnet *ifnet struct label *ifnetlabel struct label *newlabel &mac.thead; cred Subject credential ifnet Object; network interface ifnetlabel Existing policy label for ifnet newlabel Policy label update to later be applied to ifnet Determine whether the subject credential can relabel the passed network interface to the passed label update. <function>&mac.mpo;_check_socket_relabel</function> int &mac.mpo;_check_socket_relabel struct ucred *cred struct socket *socket struct label *socketlabel struct label *newlabel &mac.thead; cred Subject credential socket Object; socket socketlabel Existing policy label for socket newlabel Label update to later be applied to socketlabel Determine whether the subject credential can relabel the passed socket to the passed label update. <function>&mac.mpo;_check_cred_relabel</function> int &mac.mpo;_check_cred_relabel struct ucred *cred struct label *newlabel &mac.thead; cred Subject credential newlabel Label update to later be applied to cred Determine whether the subject credential can relabel itself to the passed label update. <function>&mac.mpo;_check_vnode_relabel</function> int &mac.mpo;_check_vnode_relabel struct ucred *cred struct vnode *vp struct label *vnodelabel struct label *newlabel &mac.thead; cred Subject credential Immutable vp Object; vnode Locked vnodelabel Existing policy label for vp newlabel Policy label update to later be applied to vp Determine whether the subject credential can relabel the passed vnode to the passed label update. <function>&mac.mpo;_check_mount_stat</function> int &mac.mpo;_check_mount_stat struct ucred *cred struct mount *mp struct label *mountlabel &mac.thead; cred Subject credential mp Object; file system mount mountlabel Policy label for mp Determine whether the subject credential can see the results of a statfs performed on the file system. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches or EPERM for lack of privilege. This call may be made in a number of situations, including during invocations of &man.statfs.2; and related calls, as well as to determine what file systems to exclude from listings of file systems, such as when &man.getfsstat.2; is invoked. <function>&mac.mpo;_check_proc_debug</function> int &mac.mpo;_check_proc_debug struct ucred *cred struct proc *proc &mac.thead; cred Subject credential Immutable proc Object; process Determine whether the subject credential can debug the passed process. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, EPERM for lack of privilege, or ESRCH to hide visibility of the target. This call may be made in a number of situations, including use of the &man.ptrace.2; and &man.ktrace.2; APIs, as well as for some types of procfs operations. <function>&mac.mpo;_check_vnode_access</function> int &mac.mpo;_check_vnode_access struct ucred *cred struct vnode *vp struct label *label int flags &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp flags &man.access.2; flags Determine how invocations of &man.access.2; and related calls by the subject credential should return when performed on the passed vnode using the passed access flags. This should generally be implemented using the same semantics used in &mac.mpo;_check_vnode_open. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_chdir</function> int &mac.mpo;_check_vnode_chdir struct ucred *cred struct vnode *dvp struct label *dlabel &mac.thead; cred Subject credential dvp Object; vnode to &man.chdir.2; into dlabel Policy label for dvp Determine whether the subject credential can change the process working directory to the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_create</function> int &mac.mpo;_check_vnode_create struct ucred *cred struct vnode *dvp struct label *dlabel struct componentname *cnp struct vattr *vap &mac.thead; cred Subject credential dvp Object; vnode dlabel Policy label for dvp cnp Component name for dvp vap vnode attributes for vap Determine whether the subject credential can create a vnode with the passed parent directory, passed name information, and passed attribute information. Return 0 for success, or an errno value for failure. Suggested failure: EACCES. for label mismatch, or EPERM for lack of privilege. This call may be made in a number of situations, including as a result of calls to &man.open.2; with O_CREAT, &man.mknod.2;, &man.mkfifo.2;, and others. <function>&mac.mpo;_check_vnode_delete</function> int &mac.mpo;_check_vnode_delete struct ucred *cred struct vnode *dvp struct label *dlabel struct vnode *vp void *label struct componentname *cnp &mac.thead; cred Subject credential dvp Parent directory vnode dlabel Policy label for dvp vp Object; vnode to delete label Policy label for vp cnp Component name for vp Determine whether the subject credential can delete a vnode from the passed parent directory and passed name information. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. This call may be made in a number of situations, including as a result of calls to &man.unlink.2; and &man.rmdir.2;. Policies implementing this entry point should also implement mpo_check_rename_to to authorize deletion of objects as a result of being the target of a rename. <function>&mac.mpo;_check_vnode_deleteacl</function> int &mac.mpo;_check_vnode_deleteacl struct ucred *cred struct vnode *vp struct label *label acl_type_t type &mac.thead; cred Subject credential Immutable vp Object; vnode Locked label Policy label for vp type ACL type Determine whether the subject credential can delete the ACL of passed type from the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_exec</function> int &mac.mpo;_check_vnode_exec struct ucred *cred struct vnode *vp struct label *label &mac.thead; cred Subject credential vp Object; vnode to execute label Policy label for vp Determine whether the subject credential can execute the passed vnode. Determination of execute privilege is made seperately from decisions about any transitioning event. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_getacl</function> int &mac.mpo;_check_vnode_getacl struct ucred *cred struct vnode *vp struct label *label acl_type_t type &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp type ACL type Determine whether the subject credentical can retrieve the ACL of passed type from the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_getextattr</function> int &mac.mpo;_check_vnode_getextattr struct ucred *cred struct vnode *vp struct label *label int attrnamespace const char *name struct uio *uio &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp attrnamespace Extended attribute namespace name Extended attribute name uio I/O structure pointer; see &man.uio.9; Determine whether the subject credential can retrieve the extended attribute with the passed namespace and name from the passed vnode. Policies implementing labeling using extended attributes may be interested in special handling of operations on those extended attributes. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_socket_listen</function> int &mac.mpo;_check_socket_listen struct ucred *cred struct socket *socket struct label *socketlabel &mac.thead; cred Subject credential socket Object; socket socketlabel Policy label for socket Determine whether the subject credential can listen on the passed socket. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_lookup</function> int &mac.mpo;_check_vnode_lookup struct ucred *cred struct vnode *dvp struct label *dlabel struct componentname *cnp &mac.thead; cred Subject credential dvp Object; vnode dlabel Policy label for dvp cnp Component name being looked up Determine whether the subject credential can perform a lookup in the passed directory vnode for the passed name. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_open</function> int &mac.mpo;_check_vnode_open struct ucred *cred struct vnode *vp struct label *label mode_t acc_mode &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp acc_mode &man.open.2; access mode Determine whether the subject credential can perform an open operation on the passed vnode with the passed access mode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_readdir</function> int &mac.mpo;_check_vnode_readdir struct ucred *cred struct vnode *dvp struct label *dlabel &mac.thead; cred Subject credential dvp Object; directory vnode dlabel Policy label for dvp Determine whether the subject credential can perform a readdir operation on the passed directory vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_readlink</function> int &mac.mpo;_check_vnode_readlink struct ucred *cred struct vnode *vp struct label *label &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp Determine whether the subject credential can perform a readlink operation on the passed symlink vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. This call may be made in a number of situations, including an explicit readlink call by the user process, or as a result of an implicit readlink during a name lookup by the process. <function>&mac.mpo;_check_rename_from_vnode</function> int &mac.mpo;_check_rename_from_vnode struct ucred *cred struct vnode *dvp struct label *dlabel struct vnode *vp struct label *label struct componentname *cnp &mac.thead; cred Subject credential dvp Directory vnode dlabel Policy label for dvp vp Object; vnode label Policy label for vp cnp Pathname Determine whether the subject credential can rename the passed vnode (vp) in the passed directory (dvp) using the passed name (cnp). This call will be made in combination with a follow-up call to mpo_check_rename_to_vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_rename_to_vnode</function> int &mac.mpo;_check_rename_to_vnode struct ucred *cred struct vnode *dvp struct label *dlabel struct vnode *vp struct label *label int samedir struct componentname *cnp &mac.thead; cred Subject credential dvp Directory vnode dlabel Policy label for dvp vp Object; vnode label Policy label for vp cnp Pathname Determine whether the subject credential can rename to the passed vnode (vp) and the passed directory (dvp) with the passed name (cnp). This call will be made in combination with an earlier call to mpo_check_rename_from_vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_revoke</function> int &mac.mpo;_check_vnode_revoke struct ucred *cred struct vnode *vp struct label *label &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp Determine whether the subject credential can revoke access to the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_setacl</function> int &mac.mpo;_check_vnode_setacl struct ucred *cred struct vnode *vp struct label *label acl_type_t type struct acl *acl &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp type ACL type acl ACL Determine whether the subject credential can set the passed ACL of passed type on the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_setextattr</function> int &mac.mpo;_check_vnode_setextattr struct ucred *cred struct vnode *vp struct label *label int attrnamespace const char *name struct uio *uio &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp attrnamespace Extended attribute namespace name Extended attribute name uio I/O structure pointer; see &man.uio.9; Determine whether the subject credentical can set the extended attribute of passed name and passed namespace on the passed vnode. Policies implementing security labels backed into extended attributes may want to provide additional protections for those attributes. Additionally, policies should avoid making decisions based on the data referenced from uio, as there is a potential race condition between this check and the actual operation. The uio may also be NULL if a delete operation is being performed. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_setflags</function> int &mac.mpo;_check_vnode_setflags struct ucred *cred struct vnode *vp struct label *label u_long flags &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp flags File flags; see &man.chflags.2; Determine whether the subject credential can set the passed flags on the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_setmode</function> int &mac.mpo;_check_vnode_setmode struct ucred *cred struct vnode *vp struct label *label mode_t mode &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp mode File mode; see &man.chmod.2; Determine whether the subject credential can set the pased mode on the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_setowner</function> int &mac.mpo;_check_vnode_setowner struct ucred *cred struct vnode *vp struct label *label uid_t uid gid_t gid &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp uid User ID gid Group ID Determine whether the subject credential can set the passed uid and passed gid as file uid and file gid on the passed vnode. The IDs may be set to (-1) to request no update. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_setutimes</function> int &mac.mpo;_check_vnode_setutimes struct ucred *cred struct vnode *vp struct label *label struct timespec atime struct timespec mtime &mac.thead; cred Subject credential vp Object; vp label Policy label for vp atime Access time; see &man.utimes.2; mtime Modification time; see &man.utimes.2; Determine whether the subject credential can set the passed access timestamps on the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_proc_sched</function> int &mac.mpo;_check_proc_sched struct ucred *ucred struct proc *proc &mac.thead; cred Subject credential proc Object; process Determine whether the subject credential can change the scheduling parameters of the passed process. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, EPERM for lack of privilege, or ESRCH to limit visibility. See &man.setpriority.2; for more information. <function>&mac.mpo;_check_proc_signal</function> int &mac.mpo;_check_proc_signal struct ucred *cred struct proc *proc int signal &mac.thead; cred Subject credential proc Object; process signal Signal; see &man.kill.2; Determine whether the subject credential can deliver the passed signal to the passed process. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, EPERM for lack of privilege, or ESRCH to limit visibility. <function>&mac.mpo;_check_vnode_stat</function> int &mac.mpo;_check_vnode_stat struct ucred *cred struct vnode *vp struct label *label &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp Determine whether the subject credential can stat the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. See &man.stat.2; for more information. <function>&mac.mpo;_check_ifnet_transmit</function> int &mac.mpo;_check_ifnet_transmit struct ucred *cred struct ifnet *ifnet struct label *ifnetlabel struct mbuf *mbuf struct label *mbuflabel &mac.thead; cred Subject credential ifnet Network interface ifnetlabel Policy label for ifnet mbuf Object; mbuf to be sent mbuflabel Policy label for mbuf Determine whether the network interface can transmit the passed mbuf. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_socket_receive</function> int &mac.mpo;_check_socket_receive struct ucred *cred struct ifnet *ifnet struct label *ifnetlabel struct mbuf *mbuf struct label *mbuflabel &mac.thead; cred Subject credential ifnet Network interface ifnetlabel Policy label for ifnet mbuf Object; mbuf to be received mbuflabel Policy label for mbuf Determine whether the socket may receive the datagram stored in the passed mbuf header. Return 0 for success, or an errno value for failure. Suggested failures: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_socket_visible</function> int &mac.mpo;_check_socket_visible struct ucred *cred struct socket *so struct label *socketlabel &mac.thead; cred Subject credential Immutable so Object; socket socketlabel Policy label for so Determine whether the subject credential cred can "see" the passed socket (socket) using system monitoring functions, such as those employed by &man.netstat.8; and &man.sockstat.1;. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches, EPERM for lack of privilege, or ESRCH to hide visibility. Label Management Calls Relabel events occur when a user process has requested that the label on an object be modified. A two-phase update occurs: first, an access control check will be performed to determine if the update is both valid and permitted, and then the update itself is performed via a seperate entry point. Relabel entry points typically accept the object, object label reference, and an update label submitted by the process. Memory allocation during relabel is discouraged, as relabel calls are not permitted to fail (failure should be reported earlier in the relabel check). <function>&mac.mpo;_init_bpfdesc</function> void &mac.mpo;_init_bpfdesc struct bpf_d *bpf_d struct label *label &mac.thead; bpf_d Object; bpf descriptor label New label to apply Initialize the label on a newly instantiated bpfdesc (BPF descriptor) <function>&mac.mpo;_init_devfsdirent</function> void &mac.mpo;_init_devfsdirent struct devfs_dirent *devfs_dirent struct label *label &mac.thead; devfs_dirent Object; devfs directory entry label New label to apply Initialize the label on a newly instantiated devfs entry. <function>&mac.mpo;_init_ifnet</function> void &mac.mpo;_init_ifnet struct ifnet *ifnet struct label *label &mac.thead; ifnet Object; network interface label New label to apply Initialize the label on a newly instantiated network interface. <function>&mac.mpo;_init_ipq</function> void &mac.mpo;_init_ipq struct ipq *ipq struct label *label &mac.thead; ipq Object; IP reassembly queue label New label to apply Initialize the label on a newly instantiated IP fragment reassembly queue. <function>&mac.mpo;_init_mbuf</function> void &mac.mpo;_init_mbuf struct mbuf *mbuf int how struct label *label &mac.thead; mbuf Object; mbuf how Blocking/non-blocking &man.malloc.9; see below label Policy label to initialize Initialize the label on a newly instantiated mbuf packet header (mbuf). The how field may be one of M_WAITOK and M_NOWAIT, and should be employed to avoid performing a blocking &man.malloc.9; during this initialization call. Mbuf allocation frequently occurs in performance sensitive environments, and the implementation should be careful to avoid blocking or long-lived operations. This entry point is permitted to fail resulting in the failure to allocate the mbuf header. <function>&mac.mpo;_init_mount</function> void &mac.mpo;_init_mount struct mount *mount struct label *mntlabel struct label *fslabel &mac.thead; mount Object; file system mount point mntlabel Policy label to be initialized for the mount itself fslabel Policy label to be initialized for the file system Initialize the labels on a newly instantiated mount point. <function>&mac.mpo;_init_socket</function> void &mac.mpo;_init_socket struct socket *socket struct label *label struct label *peerlabel &mac.thead; socket Object; socket label New label to apply to the socket peerlabel New label to apply to the socket's peer Initialize the labels on a newly instantiated socket. <function>&mac.mpo;_init_cred</function> void &mac.mpo;_init_cred struct ucred *cred struct label *label &mac.thead; cred Subject; user credetial label New label Initialize the labels on a newly instantiated subject. <function>&mac.mpo;_init_temp</function> void &mac.mpo;_init_temp struct label *label &mac.thead; label Temporary label Initialize a newly instantiated temporary label; temporary labels are frequently used to hold label update requests. <function>&mac.mpo;_init_vnode</function> void &mac.mpo;_init_vnode struct vnode *vp struct label *label &mac.thead; vp Object; file system object label New label to initialize Initialize the label on a newly instantiated vnode. <function>&mac.mpo;_destroy_bpfdesc</function> void &mac.mpo;_destroy_bpfdesc struct bpf_d *bpf_d struct label *label &mac.thead; bpf_d Object; bpf descriptor label Label being destroyed Destroy the label on a BPF descriptor. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed. <function>&mac.mpo;_destroy_devfsdirent</function> void &mac.mpo;_destroy_devfsdirent struct devfs_dirent *devfs_dirent struct label *label &mac.thead; devfs_dirent Object; devfs directory entry label Label being destroyed Destroy the label on a devfs entry. In this entry point, a policy module should free any internal storage asociated with label so that it may be destroyed. <function>&mac.mpo;_destroy_ifnet</function> void &mac.mpo;_destroy_ifnet struct ifnet *ifnet struct label *label &mac.thead; ifnet Object; network interface label Label being destroyed Destroy the label on a removed interface. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed. <function>&mac.mpo;_destroy_ipq</function> void &mac.mpo;_destroy_ipq struct ipq *ipq struct label *label &mac.thead; ipq Object; IP reassembly queue label Label being destroyed Destroy the label on an IP fragment queue. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed. <function>&mac.mpo;_destroy_mbuf</function> void &mac.mpo;_destroy_mbuf struct mbuf *mbuf struct label *label &mac.thead; mbuf Object; mbuf label Label being destroyed Destroy the label on an mbuf header. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed. <function>&mac.mpo;_destroy_mount</function> void &mac.mpo;_destroy_mount struct mount *mp struct label *mntlabel struct label *fslabel &mac.thead; mp Object; file system mount point mntlabel Mount point label being destroyed fslabel File system label being destroyed> Destroy the labels on a mount point. In this entry point, a policy module should free the internal storage associated with mntlabel and fslabel so that they may be destroyed. <function>&mac.mpo;_destroy_socket</function> void &mac.mpo;_destroy_socket struct socket *socket struct label *label struct label *peerlabel &mac.thead; socket Object; socket label Socket label being destroyed peerlabel Socket peer label being destroyed Destroy the labels on a socket. In this entry point, a policy module should free any internal storage associated with label and peerlabel so that they may be destroyed. <function>&mac.mpo;_destroy_cred</function> void &mac.mpo;_destroy_cred struct ucred *cred struct label *label &mac.thead; cred Subject; user credential label Label being destroyed Destroy the label on a credential. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed. <function>&mac.mpo;_destroy_temp</function> void &mac.mpo;_destroy_temp struct label *label &mac.thead; label Temporary label being destroyed Destroy a temporary label. In this entry point, a policy module should free any internal storage associated with the temporary label label so that it may be destroyed. <function>&mac.mpo;_destroy_vnode</function> void &mac.mpo;_destroy_vnode struct vnode *vp struct label *label &mac.thead; vp Object; file system object label Label being destroyed Destroy the label on a vnode. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed. <function>&mac.mpo;_externalize</function> void &mac.mpo;_externalize struct label *label struct mac *extmac &mac.thead; label Label to be externalized extmac MAC structure to be filled in Given an internalized subject or object label, fill out an externalized label. This call is permitted to fail. This call will be obsoleted by the new userland and extended attribute interfaces for the MAC framework. <function>&mac.mpo;_internalize</function> void &mac.mpo;_internalize struct label *label struct mac *extmac &mac.thead; label Label to be filled in extmac MAC structure to internalize Given an externalized subject or object label, likely from userland, internalize the label. The entry point implementation should handle incorrect or corrupted labels. This call is permitted to fail. This call will be obsoleted by the new userland and extended attribute interfaces for the MAC framework. Additional Framework API Calls The MAC_SYSCALL entry point provides a policy-multiplexed system call so that policies may provide additional services to user processes without registering specific system calls. The policy name provided during registration is used to demux calls from userland, and the arguments will be forwarded to this entry point. When implementing new services, security modules should be sure to invoke appropriate access control checks from the MAC framework as needed. For example, if a policy implements an augmented signal functionality, it should call the necessary signal access control checks to invoke the MAC framework and other registered policies. Userland APIs The userland API is still under development. Sample Policy Modules The mac_none policy provides sample prototypes and registration of all available policy entry points. The mac_seeotheruids policy provides a simple access control policy without the use of labeling, relying only on information already present in the kernel objects. The mac_biba policy provides a sample information flow based labeled access control policy, assigning labels to all kernel objects. System Integration ... Conclusion The TrustedBSD MAC framework permits kernel modules to augment the system security policy in a highly integrated manner. They may do this based on existing object properties, or based on label data that is maintained with the assistance of the MAC framework. The framework is sufficiently flexible to implement a variety of policy types, including information flow security policies such as MLS and Biba, as well as policies based on existing BSD credentials or file protections. Policy authors may wish to consult this documentation as well as existing security modules when implementing a new security service. diff --git a/en_US.ISO8859-1/books/developers-handbook/mac/chapter.sgml b/en_US.ISO8859-1/books/developers-handbook/mac/chapter.sgml index dae0ee52be..b6f82c56df 100644 --- a/en_US.ISO8859-1/books/developers-handbook/mac/chapter.sgml +++ b/en_US.ISO8859-1/books/developers-handbook/mac/chapter.sgml @@ -1,5681 +1,5681 @@ Chris Costello TrustedBSD Project
chris@FreeBSD.org
 Robert Watson TrustedBSD Project
rwatson@FreeBSD.org
 Writing MAC Policies Synopsis MAC, or Mandatory Access Control, is a feature introduced by the TrustedBSD Project to supplement the existing standard DAC - (Discreationary Access Control) policies of BSD Unix systems. + (Discretionary Access Control) policies of BSD Unix systems. This chapter introduces the MAC policy framework and provides documentation for a sample MAC policy module. Introduction The TrustedBSD MAC framework provides a mechanism to allow the compile-time or run-time extension of the kernel access control model. New system policies may be implemented as kernel modules and linked to the kernel; if multiple policy modules are present, their results will be composed. While the framework is intended to support a variety of access control models, its design was derived from the requirements of a set of specific access control models required for the TrustedBSD and CBOSS Projects. This includes support for fixed and floating label Biba integrity policies, the MLS confidentiality policy, the Type Enforcement rule-based access control policy, and the ability to support layering of the NSA FLASK framework above the TrustedBSD MAC framework. This document describes the rough architecture of the framework, with the understanding that this is a work-in-progress and may change subtantially as requirements evolve. Kernel Architecture The TrustedBSD MAC framework provides the opportunity for policy modules to be augment system access control decisions. Policies are permitted the opportunity to restrict the set of rights available for processes at a variety of relevant points in the kernel. In addition, they are provided the opportunity to tag processes and various kernel objects with labels storing access control information. Policy modules may register interest in a subset of the total available events or objects, and are not required to implement events or objects that are not relevant to the policy. Multiple modules may be loaded at once, and the results of the modules are composed as necessary to build an over-all system policy. Policy modules may be implemented such that they can be loaded on-demand at run-time, or such that they may only be loaded early in the boot process. This permits policies requiring pervasive labeling of all objects to prevent improper use. Userland Architecture ... Entry Point Framework Four classes of entry points are offered to policies registered with the framework: entry points associated with the registration and management of policies, entry points denoting initialization, creation, destruction, and other life cycle events for kernel objects, events assocated with access control decisions that the policy module may influence, and calls associated with the management of labels on objects. In addition, a mac_syscall() entry point is provided so that policies may extend the kernel interface without registering new system calls. Policy module writers should be aware of the kernel locking strategy, as well as what object locks are available during which entry points. Writers should attempt to avoid deadlock scenarios by avoiding grabbing non-leaf locks inside of entry points, and also follow the locking protocol for object access and modification. In particular, writers should be aware that while necessary locks to access objects and their labels are generally held, sufficient locks to modify an object or its label may not be present for all entry points. Locking information for arguments is documented in the MAC framework entry point document. Policy entry points will pass a reference to the object label along with the object itself. This permits labeled policies to be unaware of the internals of the object yet still make decisions based on the label. The exception to this is the process credential, which is assumed to be understood by policies as a first class security object in the kernel. Policies that do not implement labels on kernel objects will be passed NULL pointers for label arguments to entry points. Policy Module Registration Modules may be declared using the MAC_POLICY_SET() macro, which names the policy, provides a reference to the MAC entry point vector, provides load-time flags determining how the policy framework should handle the policy, and optionally requests the allocation of label state by the framework: static struct mac_policy_op_entry mac_none_ops[] = { { MAC_DESTROY, (macop_t)mac_none_destroy }, { MAC_INIT, (macop_t)mac_none_init }, { MAC_INIT_BPFDESC, (macop_t)mac_none_init_bpfdesc }, /* ... */ { MAC_CHECK_VNODE_STAT, (macop_t)mac_none_check_vnode_stat }, { MAC_CHECK_VNODE_WRITE, (macop_t)mac_none_check_vnode_write }, { MAC_OP_LAST, NULL } }; The MAC policy entry point vector, mac_none_ops in this example, associates functions defined in the module with specific entry points. A complete listing of available entry points and their prototypes may be found in the MAC entry point reference section. Of specific interest during module registration are the MAC_DESTROY and MAC_INIT entry points. MAC_INIT will be invoked once a policy is successfully registered with the module framework but prior to any other entry points becoming active. This permits the policy to perform any policy-specific allocation and initialization, such as initialization of any data or locks. MAC_DESTROY will be invoked when a policy module is unloaded to permit releasing of any allocated memory and destruction of locks. Currently, these two entry points are invoked with the MAC policy list mutex held to prevent any other entry points from being invoked: this will be changed, but in the mean time, policies should be careful about what kernel primitives they invoke so as to avoid lock ordering or sleeping problems. The policy declaration's module name field exists so that the module may be uniquely identified for the purposes of module dependencies. An appropriate string should be selected. The full string name of the policy is displayed to the user via the kernel log during load and unload events, and also exported when providing status information to userland processes. The policy flags field permits the module to provide the framework with information about its loader-related capabilities. Currently, two flags are defined: MPC_LOADTIME_FLAG_UNLOADOK This flag indicates that the policy module may be unloaded. If this flag is not provided, then the policy framework will reject requests to unload the module. This flag might be used by modules that allocate label state and are unable to free that state at runtime. MPC_LOADTIME_FLAG_NOTLATE This flag indicates that the policy module must be loaded and initialized early in the boot process. If the flag is specified, attempts to register the module following boot will be rejected. The flag may be used by policies that require pervasive labeling of all system objects, and cannot handle objects that have not been properly initialized by the policy. <function>&mac.mpo;_init</function void &mac.mpo;_init struct mac_policy_conf *conf &mac.thead; conf MAC policy definition Policy load event. The policy list mutex is held, so caution should be applied. <function>&mac.mpo;_destroy</function> void &mac.mpo;_destroy struct mac_policy_conf *conf &mac.thead; conf MAC policy definition Policy load event. The policy list mutex is held, so caution should be applied. Label Events This class of entry points is used by the MAC framework to permit policies to maintain label information on kernel objects. For each labeled kernel object of interest to a MAC policy, entry points may be registered for relevant life cycle events. All objects implement initialization, creation, and destruction hooks. Some objects will also implement relabeling, allowing user processes to change the labels on objects. Some objects will also implement object-specific events, such as label events associated with IP reassembly. A typical labeled object will have the following life cycle of entry points: Label initialization o (object-specific wait) \ Label creation o \ Relabel events, o--<--. Various object-specific, | | Access control events ~-->--o \ Label destruction o Label initialization permits policies to allocate memory and set initial values for labels without context for the use of the object. The label slot allocated to a policy will be zero'd by default, so some policies may not need to perform initialization. Label creation occurs when the kernel structure is associated with an actual kernel object. For example, mbufs may be allocated and remain unused in a pool until they are required. mbuf allocation causes label initialization on the mbuf to take place, but mbuf creation occurs when the mbuf is associated with a datagram. Typically, context will be provided for a creation event, including the circumstances of the creation, and labels of other relevant objects in the creation process. For example, when an mbuf is created from a socket, the socket and its label will be presented to registered policies in addition to the new mbuf and its label. Memory allocation in creation events is discouraged, as it may occur in performance sensitive ports of the kernel; in addition, creation calls are not permitted to fail so a failure to allocate memory cannot be reported. Object specific events do not generally fall into the other broad classes of label events, but will generally provide an opportunity to modify or update the label on an object based on additional context. For example, the label on an IP fragment reassembly queue may be updated during the MAC_UPDATE_IPQ entry point as a result of the acceptance of an additional mbuf to that queue. Access control events are discussed in detail in the following section. Label destruction permits policies to release storage or state associated with a label during its association with an object so that the kernel data structures supporting the object may be reused or released. In addition to labels associated with specific kernel objects, an additional class of labels exists: temporary labels. These labels are used to store update information submitted by user processes. These labels are initialized and destroyed as with other label types, but the creation event is MAC_INTERNALIZE, which accepts a user label to be converted to an in-kernel representation. File System Object Labeling Event Operations <function>&mac.mpo;_create_devfs_device</function> void &mac.mpo;_create_devfs_device dev_t dev struct devfs_dirent *devfs_dirent struct label *label &mac.thead; dev Device corresponding with devfs_dirent devfs_dirent Devfs directory entry to be labeled. label Label for devfs_dirent to be filled in. Fill out the label on a devfs_dirent being created for the passed device. This call will be made when the device file system is mounted, regenerated, or a new device is made available. <function>&mac.mpo;_create_devfs_directory</function> void &mac.mpo;_create_devfs_directory char *dirname int dirnamelen struct devfs_dirent *devfs_dirent struct label *label &mac.thead; dirname Name of directory being created namelen Length of string dirname devfs_dirent Devfs directory entry for directory being created. Fill out the label on a devfs_dirent being created for the passed directory. This call will be made when the device file system is mounted, regenerated, or a new device requiring a specific directory hierarchy is made available. <function>&mac.mpo;_create_devfs_vnode</function> void &mac.mpo;_create_devfs_vnode struct devfs_dirent *devfs_dirent struct label *direntlabel struct vnode *vp struct label *vnodelabel &mac.thead; devfs_dirent Object; devfs directory entry direntlabel Policy label for devfs_dirent vp Object; file system object being labeled vnodelabel Policy label to be filled in for vp Fill out the label on the vnode being created for the passed devfs_dirent. This call will be made when a vnode is required to represent the specified devfs_dirent in a mounted devfs instance. <function>&mac.mpo;_vnode_create_from_vnode</function> void &mac.mpo;_vnode_create_from_vnode struct ucred *cred struct vnode *parent struct label *parentlabel struct vnode *child struct label *childlabel &mac.thead; cred Subject credential parent Parent vnode; the directory in which child is being created parentlabel Policy label for parent child New vnode childlabel Label to be filled in for child Fill out the label on the vnode being created in the passed vnode parent by the passed subject credential. This call will be made when a vnode is allocated during a vnode creation operation. For example, this call is made by multi-label file systems during the creation of a new file or directory. <function>&mac.mpo;_create_mount</function> void &mac.mpo;_create_mount struct ucred *cred struct mount *mp struct label *mnt struct label *fslabel &mac.thead; cred Subject credential mp Object; file system being mounted mntlabel Policy label to be filled in for mp fslabel Policy label for the file system mp mounts. Fill out the labels on the mount point being created by the passed subject credential. This call will be made when a new file system is mounted. <function>&mac.mpo;_create_root_mount</function> void &mac.mpo;_create_root_mount struct ucred *cred struct mount *mp struct label *mntlabel struct label *fslabel &mac.thead; See . Fill out the labels on the mount point being created by the passed subject credential. This call will be made when the root file system is mounted, after &mac.mpo;_create_mount;. <function>&mac.mpo;_vnode_relabel</function> void &mac.mpo;_vnode_relabel struct ucred *cred struct vnode *vp struct label *vnodelabel struct label *newlabel &mac.thead; cred Subject credential vp vnode to relabel vnodelabel Existing policy label for vp newlabel New, possibly partial label to replace vnodelabel Update the label on the passed vnode given the passed update vnode label and the passed subject credential. <function>&mac.mpo;_stdcreatevnode_ea</function> int &mac.mpo;_stdcreatevnode_ea struct vnode *vp struct label *vnodelabel &mac.thead; vp vnode to commit Locked on entry, locked on exit vnodelabel Label associated with vp This entry point is called when a vnode is to be committed to disk via the extended attribute service (see &man.extattr.9;). If committing to the disk is successful, a value of 0 should be returned; otherwise, an appropriate error code should be returned. The current implementation as of July 24, 2002 commits the data to disk from within the architecture. The implementation will be updated to be closer to the above documentation as development progresses. <function>&mac.mpo;_update_devfsdirent</function> void &mac.mpo;_update_devfsdirent struct devfs_dirent *devfs_dirent struct label *direntlabel struct vnode *vp struct label *vnodelabel &mac.thead; devfs_dirent Object; devfs directory entry direntlabel Policy label for devfs_dirent to be updated. vp Parent vnode Locked vnodelabel Policy label for vp Update the devfs_dirent label from the passed devfs vnode label. This call will be made when a devfs vnode has been successfully relabeled to commit the label change such that it lasts even if the vnode is recycled. It will also be made when when a symlink is created in devfs, following a call to mac_vnode_create_from_vnode to initialize the vnode label. <function>&mac.mpo;_update_procfsvnode</function> void &mac.mpo;_update_procfsvnode struct vnode *vp struct label *vnodelabel struct ucred *cred &mac.thead; vp Object; procfs vnode Locked vnodelabel Policy label to be filled in for vp cred Subject; credential for the process entry Immutable Update the procfs vnode label from the passed subject credential. This call will be made when an operation on a procfs vnode requires a fresh label on a process-derived vnode. <function>&mac.mpo;_update_vnode_from_extattr</function> int &mac.mpo;_update_vnode_from_extattr struct vnode *vp struct label *vnodelabel struct mount *mp struct label *fslabel &mac.thead; vp Object; vnode whose label is being updated Locked vnodelabel Policy label to refresh mp Mount point for vp fslabel Policy label for vp's file system. Update the vnode label by refreshing the label data from the extended attribute service for the vnode. The mount point fslabel is also made available so that the fslabel may be used as a labeling source if fallback is appropriate for the policy. This call is permitted to fail; if the call fails, the associated label refresh will also fail, causing the failure of the operation requiring the MAC check and vnode label refresh, permitting a fail closed policy if labeling data is not available. <function>&mac.mpo;_update_from_externalized</function> int &mac.mpo;_update_from_externalized struct vnode *vp struct label *vnodelabel struct mac *extmac &mac.thead; vp Object; vnode Locked vnodelabel Policy label for vp extmac Externalized MAC policy label Update the vnode label from the passed externalized label loaded from disk by the MAC framework. This call is permitted to fail; if the call fails, the associated label refresh will also fail, causing the failure of the operation requiring the MAC check and vnode label refresh, permitting a fail closed policy if labeling data is not available. This call will be obsoleted by the new extended attribute labeling interface. <function>&mac.mpo;_update_vnode_from_mount</function> void &mac.mpo;_update_vnode_from_mount struct vnode *vp struct label *vnodelabel struct mount *mp struct label *mountlabel &mac.thead; vp Object; vnode Locked vnodelabel Policy label for vp mp Mount point where vp resides fslabel Policy label for the file system where vp resides. Update the vnode label from the passed mount point label. This call is made when a single label file system vnode requires a label, or if the obsoleted MAC framework externalized extended attribute read fails. IPC Object Labeling Event Operations <function>&mac.mpo;_create_mbuf_from_socket</function> void &mac.mpo;_create_mbuf_from_socket struct socket *so struct label *socketlabel struct mbuf *m struct label *mbuflabel &mac.thead; socket Socket Socket locking WIP socketlabel Policy label for socket m Object; mbuf mbuflabel Policy label to fill in for m Set the label on a newly created mbuf header from the passed socket label. This call is made when a new datagram or messsage is generated by the socket and stored in the passed mbuf. <function>&mac.mpo;_create_socket</function> void &mac.mpo;_create_socket struct ucred *cred struct socket *so struct label *socketlabel &mac.thead; cred Subject credential Immutable so Object; socket to label socketlabel Label to fill in for so Set the label on a newly created socket from the passed subject credential. This call is made when a socket is created. <function>&mac.mpo;_create_socket_from_socket</function> void &mac.mpo;_create_socket_from_socket struct socket *oldsocket struct label *oldsocketlabel struct socket *newsocket struct label *newsocketlabel &mac.thead; oldsocket Object; parent socket; created from &man.listen.2; oldsocketlabel Label for oldsocket newsocket Object; child socket; incoming connection newsocketlabel Label to be filled in for newsocket Set the label on a newly created stream socket from the passed listen socket. This call may occur during &man.accept.2;, or prior to &man.accept.2;, depending on the protocol. <function>&mac.mpo;_socket_relabel</function> void &mac.mpo;_socket_relabel struct ucred *cred struct socket *so struct label *oldlabel struct label *newlabel &mac.thead; cred Subject credential Immutable so Object; socket oldlabel Current label for so newlabel Label update for so Update the label on a socket from the passed socket label update. <function>&mac.mpo;_set_socket_peer_from_mbuf</function> void &mac.mpo;_set_socket_peer_from_mbuf struct mbuf *mbuf struct label *mbuflabel struct label *oldlabel struct label *newlabel &mac.thead; mbuf First datagram received over socket mbuflabel Label for mbuf oldlabel Current label for the socket newlabel Policy label to be filled out for the socket Set the peer label on a stream socket from the passed mbuf label. This call will be made when the first datagram is received by the stream socket, with the exception of Unix domain sockets. <function>&mac.mpo;_set_socket_peer_from_socket</function> void &mac.mpo;_set_socket_peer_from_socket struct socket *oldsocket struct label *oldsocketlabel struct socket *newsocket struct label *newsocketpeerlabel &mac.thead; oldsocket Local socket oldsocketlabel Policy label for oldsocket newsocket Peer socket newsocketpeerlabel Policy label to fill in for newsocket Set the peer label on a stream UNIX domain socket from the passed remote socket endpoint. This call will be made when the socket pair is connected, and will be made for both endpoints. Network Object Labeling Event Operations <function>&mac.mpo;_create_bpfdesc</function> void &mac.mpo;_create_bpfdesc struct ucred *cred struct bpf_d *bpf_d struct label *bpflabel &mac.thead; cred Subject credential Immutable bpf_d Object; bpf descriptor bpf Policy label to be filled in for bpf_d Set the label on a newly created BPF descriptor from the passed subject credential. This call will be made when a BPF device node is opened by a process with the passed subject credential. <function>&mac.mpo;_create_ifnet</function> void &mac.mpo;_create_ifnet struct ifnet *ifnet struct label *ifnetlabel &mac.thead; ifnet Network interface ifnetlabel Policy label to fill in for ifnet Set the label on a newly created interface. This call may be made when a new physical interface becomes available to the system, or when a pseudo-interface is instantiated during the boot or as a result of a user action. <function>&mac.mpo;_create_ipq</function> void &mac.mpo;_create_ipq struct mbuf *fragment struct label *fragmentlabel struct ipq *ipq struct label *ipqlabel &mac.thead; fragment First received IP fragment fragmentlabel Policy label for fragment ipq IP reassembly queue to be labeled ipqlabel Policy label to be filled in for ipq Set the label on a newly created IP fragment reassembly queue from the mbuf header of the first received fragment. <function>&mac.mpo;_create_datagram_from_ipq</function> void &mac.mpo;_create_create_datagram_from_ipq struct ipq *ipq struct label *ipqlabel struct mbuf *datagram struct label *datagramlabel &mac.thead; ipq IP reassembly queue ipqlabel Policy label for ipq datagram Datagram to be labeled datagramlabel Policy label to be filled in for datagramlabel Set the label on a newly reassembled IP datagram from the IP fragment reassembly queue from which it was generated. <function>&mac.mpo;_create_fragment</function> void &mac.mpo;_create_fragment struct mbuf *datagram struct label *datagramlabel struct mbuf *fragment struct label *fragmentlabel &mac.thead; datagram Datagram datagramlabel Policy label for datagram fragment Fragment to be labeled fragmentlabel Policy label to be filled in for datagram Set the label on the mbuf header of a newly created IP fragment from the label on the mbuf header of the datagram it was generate from. <function>&mac.mpo;_create_mbuf_from_mbuf</function> void &mac.mpo;_create_mbuf_from_mbuf struct mbuf *oldmbuf struct label *oldmbuflabel struct mbuf *newmbuf struct label *newmbuflabel &mac.thead; oldmbuf Existing (source) mbuf oldmbuflabel Policy label for oldmbuf newmbuf New mbuf to be labeled newmbuflabel Policy label to be filled in for newmbuf Set the label on the mbuf header of a newly created datagram from the mbuf header of an existing datagram. This call may be made in a number of situations, including when an mbuf is re-allocated for alignment purposes. <function>&mac.mpo;_create_mbuf_linklayer</function> void &mac.mpo;_create_mbuf_linklayer struct ifnet *ifnet struct label *ifnetlabel struct mbuf *mbuf struct label *mbuflabel &mac.thead; ifnet Network interface ifnetlabel Policy label for ifnet mbuf mbuf header for new datagram mbuflabel Policy label to be filled in for mbuf Set the label on the mbuf header of a newly created datagram generated for the purposes of a link layer response for the passed interface. This call may be made in a number of situations, including for ARP or ND6 responses in the IPv4 and IPv6 stacks. <function>&mac.mpo;_create_mbuf_from_bpfdesc</function> void &mac.mpo;_create_mbuf_from_bpfdesc struct bpf_d *bpf_d struct label *bpflabel struct mbuf *mbuf struct label *mbuflabel &mac.thead; bpf_d BPF descriptor bpflabel Policy label for bpflabel mbuf New mbuf to be labeled mbuflabel Policy label to fill in for mbuf Set the label on the mbuf header of a newly created datagram generated using the passed BPF descriptor. This call is made when a write is performed to the BPF device associated with the passed BPF descriptor. <function>&mac.mpo;_create_mbuf_from_ifnet</function> void &mac.mpo;_create_mbuf_from_ifnet struct ifnet *ifnet struct label *ifnetlabel struct mbuf *mbuf struct label *mbuflabel &mac.thead; ifnet Network interface ifnetlabel Policy label for ifnetlabel mbuf mbuf header for new datagram mbuflabel Policy label to be filled in for mbuf Set the label on the mbuf header of a newly created datagram generated from the passed network interface. <function>&mac.mpo;_create_mbuf_multicast_encap</function> void &mac.mpo;_create_mbuf_multicast_encap struct mbuf *oldmbuf struct label *oldmbuflabel struct ifnet *ifnet struct label *ifnetlabel struct mbuf *newmbuf struct label *newmbuflabel &mac.thead; oldmbuf mbuf header for existing datagram oldmbuflabel Policy label for oldmbuf ifnet Network interface ifnetlabel Policy label for ifnet newmbuf mbuf header to be labeled for new datagram newmbuflabel Policy label to be filled in for newmbuf Set the label on the mbuf header of a newly created datagram generated from the existing passed datagram when it is processed by the passed multicast encapsulation interface. This call is made when an mbuf is to be delivered using the virtual interface. <function>&mac.mpo;_create_mbuf_netlayer</function> void &mac.mpo;_create_mbuf_netlayer struct mbuf *oldmbuf struct label *oldmbuflabel struct mbuf *newmbuf struct label *newmbuflabel &mac.thead; oldmbuf Received datagram oldmbuflabel Policy label for oldmbuf newmbuf Newly created datagram newmbuflabel Policy label for newmbuf Set the label on the mbuf header of a newly created datagram generated by the IP stack in response to an existing received datagram (oldmbuf). This call may be made in a number of situations, including when responding to ICMP request datagrams. <function>&mac.mpo;_fragment_match</function> int &mac.mpo;_fragment_match struct mbuf *fragment struct label *fragmentlabel struct ipq *ipq struct label *ipqlabel &mac.thead; fragment IP datagram fragment fragmentlabel Policy label for fragment ipq IP fragment reassembly queue ipqlabel Policy label for ipq Determine whether an mbuf header containing an IP datagram (fragment) fragment matches the label of the passed IP fragment reassembly queue (ipq). Return (1) for a successful match, or (0) for no match. This call is made when the IP stack attempts to find an existing fragment reassembly queue for a newly received fragment; if this fails, a new fragment reassembly queue may be instantiated for the fragment. Policies may use this entry point to prevent the reassembly of otherwise matching IP fragments if policy does not permit them to be reassembled based on the label or other information. <function>&mac.mpo;_ifnet_relabel</function> void &mac.mpo;_ifnet_relabel struct ucred *cred struct ifnet *ifnet struct label *ifnetlabel struct label *newlabel &mac.thead; cred Subject credential ifnet Object; Network interface ifnetlabel Policy label for ifnet newlabel Label update to apply to ifnet Update the label of network interface, ifnet, based on the passed update label, newlabel, and the passed subject credential, cred. <function>&mac.mpo;_update_ipq</function> void &mac.mpo;_update_ipq struct mbuf *fragment struct label *fragmentlabel struct ipq *ipq struct label *ipqlabel &mac.thead; mbuf IP fragment mbuflabel Policy label for mbuf ipq IP fragment reassembly queue ipqlabel Policy label to be updated for ipq Update the label on an IP fragment reassembly queue (ipq) based on the acceptance of the passed IP fragment mbuf header (mbuf). Process Labeling Event Operations <function>&mac.mpo;_create_cred</function> void &mac.mpo;_create_cred struct ucred *parent_cred struct ucred *child_cred &mac.thead; parent_cred Parent subject credential child_cred Child subject credential Set the label of a newly created subject credential from the passed subject credential. This call will be made when crcopy(9) is invoked on a newly created struct ucred. This call should not be confused with a process forking or creation event. <function>&mac.mpo;_execve_transition</function> void &mac.mpo;_execve_transition struct ucred *old struct ucred *new struct vnode *vp struct label *vnodelabel &mac.thead; old Existing subject credential Immutable new New subject credential to be labeled vp File to execute Locked vnodelabel Policy label for vp Update the label of a newly created subject credential (new) from the passed existing subject credential (old) based on a label transition caused by executing the passed vnode (vp). This call occurs when a process executes the passed vnode and one of the policies returns a success from the mpo_execve_will_transition entry point. Policies may choose to implement this call simply by invoking mpo_create_cred and passing the two subject credentials so as not to implement a transitioning event. Policies should not leave this entry point unimplemented if they implement mpo_create_cred, even if they do not implement mpo_execve_will_transition. <function>&mac.mpo;_execve_will_transition</function> int &mac.mpo;_execve_will_transition struct ucred *old struct vnode *vp struct label *vnodelabel &mac.thead; old Subject credential prior to &man.execve.2; Immutable vp File to execute vnodelabel Policy label for vp Determine whether the policy will want to perform a transition event as a result of the execution of the passed vnode by the passed subject credential. Return 1 if a transition is required, 0 if not. Even if a policy returns 0, it should behave correctly in the presence of an unexpected invocation of mpo_execve_transition, as that call may happen as a result of another policy requesting a transition. <function>&mac.mpo;_create_proc0</function> void &mac.mpo;_create_proc0 struct ucred *cred &mac.thead; cred Subject credential to be filled in Create the subject credential of process 0, the parent of all kernel processes. <function>&mac.mpo;_create_proc1</function> void &mac.mpo;_create_proc1 struct ucred *cred &mac.thead; cred Subject credential to be filled in Create the subject credential of process 1, the parent of all kernel processes. <function>&mac.mpo;_cred_relabel</function> void &mac.mpo;_cred_relabel struct ucred *cred struct label *newlabel &mac.thead; cred Subject credential newlabel Label update to apply to cred Update the label on a subject credential from the passed update label. Access Control Checks Access control entry points permit policy modules to influence access control decisions made by the kernel. Generally, although not always, arguments to an access control entry point will include one or more authorizing credentials, information (possibly including a label) for any other objects involved in the operation. An access control entry point may return 0 to permit the operation, and an &man.errno.2; error value. The results of invoking the entry point across various registered policy modules will be composed as follows: if all modules permit the operation to succeed, success will be returned. If one or modules returns a failure, a failure will be returned. If more than one module returns a failure, the errno value to return to the user will be selected using the following precedence, implemented by the error_select() function in kern_mac.c: Most precedence EDEADLK EINVAL ESRCH EACCES Least precedence EPERM If none of the error values returned by all modules are listed in the precedence chart then an arbitrarily selected value from the set will be returned. In general, the rules provide precedence to errors in the following order: kernel failures, invalid arguments, object not present, access not permitted, other. <function>&mac.mpo;_check_bpfdesc_receive</function> int &mac.mpo;_check_bpfdesc_receive struct bpf_d *bpf_d struct label *bpflabel struct ifnet *ifnet struct label *ifnetlabel &mac.thead; bpf_d Subject; BPF descriptor bpflabel Policy label for bpf_d ifnet Object; network interface ifnetlabel Policy label for ifnet Determine whether the MAC framework should permit datagrams from the passed interface to be delivered to the buffers of the passed BPF descriptor. Return (0) for success, or an errno value for failure Suggested failure: EACCES for label mismatches, EPERM for lack of privilege. <function>&mac.mpo;_check_socket_bind</function> int &mac.mpo;_check_socket_bind struct ucred *cred struct socket *socket struct label *socketlabel struct sockaddr *sockaddr &mac.thead; cred Subject credential socket Socket to be bound socketlabel Policy label for socket sockaddr Address of socket <function>&mac.mpo;_check_socket_connect</function> int &mac.mpo;_check_socket_connect struct ucred *cred struct socket *socket struct label *socketlabel struct sockaddr *sockaddr &mac.thead; cred Subject credential socket Socket to be connected socketlabel Policy label for socket sockaddr Address of socket Determine whether the subject credential (cred) can connect the passed socket (socket) to the passed socket address (sockaddr). Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches, EPERM for lack of privilege. <function>&mac.mpo;_check_cred_visible</function> int &mac.mpo;_check_cred_visible struct ucred *u1 struct ucred *u2 &mac.thead; u1 Subject credential u2 Object credential Determine whether the subject credential u1 can see other subjects with the passed subject credential u2. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches, EPERM for lack of privilege, or ESRCH to hide visibility. This call may be made in a number of situations, including inter-process status sysctls used by ps, and in procfs lookups. <function>&mac.mpo;_check_socket_visible</function> int &mac.mpo;_check_socket_visible struct ucred *cred struct socket *socket struct label *socketlabel &mac.thead; cred Subject credential socket Object; socket socketlabel Policy label for socket <function>&mac.mpo;_check_ifnet_relabel</function> int &mac.mpo;_check_ifnet_relabel struct ucred *cred struct ifnet *ifnet struct label *ifnetlabel struct label *newlabel &mac.thead; cred Subject credential ifnet Object; network interface ifnetlabel Existing policy label for ifnet newlabel Policy label update to later be applied to ifnet Determine whether the subject credential can relabel the passed network interface to the passed label update. <function>&mac.mpo;_check_socket_relabel</function> int &mac.mpo;_check_socket_relabel struct ucred *cred struct socket *socket struct label *socketlabel struct label *newlabel &mac.thead; cred Subject credential socket Object; socket socketlabel Existing policy label for socket newlabel Label update to later be applied to socketlabel Determine whether the subject credential can relabel the passed socket to the passed label update. <function>&mac.mpo;_check_cred_relabel</function> int &mac.mpo;_check_cred_relabel struct ucred *cred struct label *newlabel &mac.thead; cred Subject credential newlabel Label update to later be applied to cred Determine whether the subject credential can relabel itself to the passed label update. <function>&mac.mpo;_check_vnode_relabel</function> int &mac.mpo;_check_vnode_relabel struct ucred *cred struct vnode *vp struct label *vnodelabel struct label *newlabel &mac.thead; cred Subject credential Immutable vp Object; vnode Locked vnodelabel Existing policy label for vp newlabel Policy label update to later be applied to vp Determine whether the subject credential can relabel the passed vnode to the passed label update. <function>&mac.mpo;_check_mount_stat</function> int &mac.mpo;_check_mount_stat struct ucred *cred struct mount *mp struct label *mountlabel &mac.thead; cred Subject credential mp Object; file system mount mountlabel Policy label for mp Determine whether the subject credential can see the results of a statfs performed on the file system. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches or EPERM for lack of privilege. This call may be made in a number of situations, including during invocations of &man.statfs.2; and related calls, as well as to determine what file systems to exclude from listings of file systems, such as when &man.getfsstat.2; is invoked. <function>&mac.mpo;_check_proc_debug</function> int &mac.mpo;_check_proc_debug struct ucred *cred struct proc *proc &mac.thead; cred Subject credential Immutable proc Object; process Determine whether the subject credential can debug the passed process. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, EPERM for lack of privilege, or ESRCH to hide visibility of the target. This call may be made in a number of situations, including use of the &man.ptrace.2; and &man.ktrace.2; APIs, as well as for some types of procfs operations. <function>&mac.mpo;_check_vnode_access</function> int &mac.mpo;_check_vnode_access struct ucred *cred struct vnode *vp struct label *label int flags &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp flags &man.access.2; flags Determine how invocations of &man.access.2; and related calls by the subject credential should return when performed on the passed vnode using the passed access flags. This should generally be implemented using the same semantics used in &mac.mpo;_check_vnode_open. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_chdir</function> int &mac.mpo;_check_vnode_chdir struct ucred *cred struct vnode *dvp struct label *dlabel &mac.thead; cred Subject credential dvp Object; vnode to &man.chdir.2; into dlabel Policy label for dvp Determine whether the subject credential can change the process working directory to the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_create</function> int &mac.mpo;_check_vnode_create struct ucred *cred struct vnode *dvp struct label *dlabel struct componentname *cnp struct vattr *vap &mac.thead; cred Subject credential dvp Object; vnode dlabel Policy label for dvp cnp Component name for dvp vap vnode attributes for vap Determine whether the subject credential can create a vnode with the passed parent directory, passed name information, and passed attribute information. Return 0 for success, or an errno value for failure. Suggested failure: EACCES. for label mismatch, or EPERM for lack of privilege. This call may be made in a number of situations, including as a result of calls to &man.open.2; with O_CREAT, &man.mknod.2;, &man.mkfifo.2;, and others. <function>&mac.mpo;_check_vnode_delete</function> int &mac.mpo;_check_vnode_delete struct ucred *cred struct vnode *dvp struct label *dlabel struct vnode *vp void *label struct componentname *cnp &mac.thead; cred Subject credential dvp Parent directory vnode dlabel Policy label for dvp vp Object; vnode to delete label Policy label for vp cnp Component name for vp Determine whether the subject credential can delete a vnode from the passed parent directory and passed name information. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. This call may be made in a number of situations, including as a result of calls to &man.unlink.2; and &man.rmdir.2;. Policies implementing this entry point should also implement mpo_check_rename_to to authorize deletion of objects as a result of being the target of a rename. <function>&mac.mpo;_check_vnode_deleteacl</function> int &mac.mpo;_check_vnode_deleteacl struct ucred *cred struct vnode *vp struct label *label acl_type_t type &mac.thead; cred Subject credential Immutable vp Object; vnode Locked label Policy label for vp type ACL type Determine whether the subject credential can delete the ACL of passed type from the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_exec</function> int &mac.mpo;_check_vnode_exec struct ucred *cred struct vnode *vp struct label *label &mac.thead; cred Subject credential vp Object; vnode to execute label Policy label for vp Determine whether the subject credential can execute the passed vnode. Determination of execute privilege is made seperately from decisions about any transitioning event. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_getacl</function> int &mac.mpo;_check_vnode_getacl struct ucred *cred struct vnode *vp struct label *label acl_type_t type &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp type ACL type Determine whether the subject credentical can retrieve the ACL of passed type from the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_getextattr</function> int &mac.mpo;_check_vnode_getextattr struct ucred *cred struct vnode *vp struct label *label int attrnamespace const char *name struct uio *uio &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp attrnamespace Extended attribute namespace name Extended attribute name uio I/O structure pointer; see &man.uio.9; Determine whether the subject credential can retrieve the extended attribute with the passed namespace and name from the passed vnode. Policies implementing labeling using extended attributes may be interested in special handling of operations on those extended attributes. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_socket_listen</function> int &mac.mpo;_check_socket_listen struct ucred *cred struct socket *socket struct label *socketlabel &mac.thead; cred Subject credential socket Object; socket socketlabel Policy label for socket Determine whether the subject credential can listen on the passed socket. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_lookup</function> int &mac.mpo;_check_vnode_lookup struct ucred *cred struct vnode *dvp struct label *dlabel struct componentname *cnp &mac.thead; cred Subject credential dvp Object; vnode dlabel Policy label for dvp cnp Component name being looked up Determine whether the subject credential can perform a lookup in the passed directory vnode for the passed name. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_open</function> int &mac.mpo;_check_vnode_open struct ucred *cred struct vnode *vp struct label *label mode_t acc_mode &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp acc_mode &man.open.2; access mode Determine whether the subject credential can perform an open operation on the passed vnode with the passed access mode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_readdir</function> int &mac.mpo;_check_vnode_readdir struct ucred *cred struct vnode *dvp struct label *dlabel &mac.thead; cred Subject credential dvp Object; directory vnode dlabel Policy label for dvp Determine whether the subject credential can perform a readdir operation on the passed directory vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_readlink</function> int &mac.mpo;_check_vnode_readlink struct ucred *cred struct vnode *vp struct label *label &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp Determine whether the subject credential can perform a readlink operation on the passed symlink vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. This call may be made in a number of situations, including an explicit readlink call by the user process, or as a result of an implicit readlink during a name lookup by the process. <function>&mac.mpo;_check_rename_from_vnode</function> int &mac.mpo;_check_rename_from_vnode struct ucred *cred struct vnode *dvp struct label *dlabel struct vnode *vp struct label *label struct componentname *cnp &mac.thead; cred Subject credential dvp Directory vnode dlabel Policy label for dvp vp Object; vnode label Policy label for vp cnp Pathname Determine whether the subject credential can rename the passed vnode (vp) in the passed directory (dvp) using the passed name (cnp). This call will be made in combination with a follow-up call to mpo_check_rename_to_vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_rename_to_vnode</function> int &mac.mpo;_check_rename_to_vnode struct ucred *cred struct vnode *dvp struct label *dlabel struct vnode *vp struct label *label int samedir struct componentname *cnp &mac.thead; cred Subject credential dvp Directory vnode dlabel Policy label for dvp vp Object; vnode label Policy label for vp cnp Pathname Determine whether the subject credential can rename to the passed vnode (vp) and the passed directory (dvp) with the passed name (cnp). This call will be made in combination with an earlier call to mpo_check_rename_from_vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_revoke</function> int &mac.mpo;_check_vnode_revoke struct ucred *cred struct vnode *vp struct label *label &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp Determine whether the subject credential can revoke access to the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_setacl</function> int &mac.mpo;_check_vnode_setacl struct ucred *cred struct vnode *vp struct label *label acl_type_t type struct acl *acl &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp type ACL type acl ACL Determine whether the subject credential can set the passed ACL of passed type on the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_setextattr</function> int &mac.mpo;_check_vnode_setextattr struct ucred *cred struct vnode *vp struct label *label int attrnamespace const char *name struct uio *uio &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp attrnamespace Extended attribute namespace name Extended attribute name uio I/O structure pointer; see &man.uio.9; Determine whether the subject credentical can set the extended attribute of passed name and passed namespace on the passed vnode. Policies implementing security labels backed into extended attributes may want to provide additional protections for those attributes. Additionally, policies should avoid making decisions based on the data referenced from uio, as there is a potential race condition between this check and the actual operation. The uio may also be NULL if a delete operation is being performed. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_setflags</function> int &mac.mpo;_check_vnode_setflags struct ucred *cred struct vnode *vp struct label *label u_long flags &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp flags File flags; see &man.chflags.2; Determine whether the subject credential can set the passed flags on the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_setmode</function> int &mac.mpo;_check_vnode_setmode struct ucred *cred struct vnode *vp struct label *label mode_t mode &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp mode File mode; see &man.chmod.2; Determine whether the subject credential can set the pased mode on the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_setowner</function> int &mac.mpo;_check_vnode_setowner struct ucred *cred struct vnode *vp struct label *label uid_t uid gid_t gid &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp uid User ID gid Group ID Determine whether the subject credential can set the passed uid and passed gid as file uid and file gid on the passed vnode. The IDs may be set to (-1) to request no update. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_vnode_setutimes</function> int &mac.mpo;_check_vnode_setutimes struct ucred *cred struct vnode *vp struct label *label struct timespec atime struct timespec mtime &mac.thead; cred Subject credential vp Object; vp label Policy label for vp atime Access time; see &man.utimes.2; mtime Modification time; see &man.utimes.2; Determine whether the subject credential can set the passed access timestamps on the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_proc_sched</function> int &mac.mpo;_check_proc_sched struct ucred *ucred struct proc *proc &mac.thead; cred Subject credential proc Object; process Determine whether the subject credential can change the scheduling parameters of the passed process. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, EPERM for lack of privilege, or ESRCH to limit visibility. See &man.setpriority.2; for more information. <function>&mac.mpo;_check_proc_signal</function> int &mac.mpo;_check_proc_signal struct ucred *cred struct proc *proc int signal &mac.thead; cred Subject credential proc Object; process signal Signal; see &man.kill.2; Determine whether the subject credential can deliver the passed signal to the passed process. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, EPERM for lack of privilege, or ESRCH to limit visibility. <function>&mac.mpo;_check_vnode_stat</function> int &mac.mpo;_check_vnode_stat struct ucred *cred struct vnode *vp struct label *label &mac.thead; cred Subject credential vp Object; vnode label Policy label for vp Determine whether the subject credential can stat the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. See &man.stat.2; for more information. <function>&mac.mpo;_check_ifnet_transmit</function> int &mac.mpo;_check_ifnet_transmit struct ucred *cred struct ifnet *ifnet struct label *ifnetlabel struct mbuf *mbuf struct label *mbuflabel &mac.thead; cred Subject credential ifnet Network interface ifnetlabel Policy label for ifnet mbuf Object; mbuf to be sent mbuflabel Policy label for mbuf Determine whether the network interface can transmit the passed mbuf. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_socket_receive</function> int &mac.mpo;_check_socket_receive struct ucred *cred struct ifnet *ifnet struct label *ifnetlabel struct mbuf *mbuf struct label *mbuflabel &mac.thead; cred Subject credential ifnet Network interface ifnetlabel Policy label for ifnet mbuf Object; mbuf to be received mbuflabel Policy label for mbuf Determine whether the socket may receive the datagram stored in the passed mbuf header. Return 0 for success, or an errno value for failure. Suggested failures: EACCES for label mismatch, or EPERM for lack of privilege. <function>&mac.mpo;_check_socket_visible</function> int &mac.mpo;_check_socket_visible struct ucred *cred struct socket *so struct label *socketlabel &mac.thead; cred Subject credential Immutable so Object; socket socketlabel Policy label for so Determine whether the subject credential cred can "see" the passed socket (socket) using system monitoring functions, such as those employed by &man.netstat.8; and &man.sockstat.1;. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches, EPERM for lack of privilege, or ESRCH to hide visibility. Label Management Calls Relabel events occur when a user process has requested that the label on an object be modified. A two-phase update occurs: first, an access control check will be performed to determine if the update is both valid and permitted, and then the update itself is performed via a seperate entry point. Relabel entry points typically accept the object, object label reference, and an update label submitted by the process. Memory allocation during relabel is discouraged, as relabel calls are not permitted to fail (failure should be reported earlier in the relabel check). <function>&mac.mpo;_init_bpfdesc</function> void &mac.mpo;_init_bpfdesc struct bpf_d *bpf_d struct label *label &mac.thead; bpf_d Object; bpf descriptor label New label to apply Initialize the label on a newly instantiated bpfdesc (BPF descriptor) <function>&mac.mpo;_init_devfsdirent</function> void &mac.mpo;_init_devfsdirent struct devfs_dirent *devfs_dirent struct label *label &mac.thead; devfs_dirent Object; devfs directory entry label New label to apply Initialize the label on a newly instantiated devfs entry. <function>&mac.mpo;_init_ifnet</function> void &mac.mpo;_init_ifnet struct ifnet *ifnet struct label *label &mac.thead; ifnet Object; network interface label New label to apply Initialize the label on a newly instantiated network interface. <function>&mac.mpo;_init_ipq</function> void &mac.mpo;_init_ipq struct ipq *ipq struct label *label &mac.thead; ipq Object; IP reassembly queue label New label to apply Initialize the label on a newly instantiated IP fragment reassembly queue. <function>&mac.mpo;_init_mbuf</function> void &mac.mpo;_init_mbuf struct mbuf *mbuf int how struct label *label &mac.thead; mbuf Object; mbuf how Blocking/non-blocking &man.malloc.9; see below label Policy label to initialize Initialize the label on a newly instantiated mbuf packet header (mbuf). The how field may be one of M_WAITOK and M_NOWAIT, and should be employed to avoid performing a blocking &man.malloc.9; during this initialization call. Mbuf allocation frequently occurs in performance sensitive environments, and the implementation should be careful to avoid blocking or long-lived operations. This entry point is permitted to fail resulting in the failure to allocate the mbuf header. <function>&mac.mpo;_init_mount</function> void &mac.mpo;_init_mount struct mount *mount struct label *mntlabel struct label *fslabel &mac.thead; mount Object; file system mount point mntlabel Policy label to be initialized for the mount itself fslabel Policy label to be initialized for the file system Initialize the labels on a newly instantiated mount point. <function>&mac.mpo;_init_socket</function> void &mac.mpo;_init_socket struct socket *socket struct label *label struct label *peerlabel &mac.thead; socket Object; socket label New label to apply to the socket peerlabel New label to apply to the socket's peer Initialize the labels on a newly instantiated socket. <function>&mac.mpo;_init_cred</function> void &mac.mpo;_init_cred struct ucred *cred struct label *label &mac.thead; cred Subject; user credetial label New label Initialize the labels on a newly instantiated subject. <function>&mac.mpo;_init_temp</function> void &mac.mpo;_init_temp struct label *label &mac.thead; label Temporary label Initialize a newly instantiated temporary label; temporary labels are frequently used to hold label update requests. <function>&mac.mpo;_init_vnode</function> void &mac.mpo;_init_vnode struct vnode *vp struct label *label &mac.thead; vp Object; file system object label New label to initialize Initialize the label on a newly instantiated vnode. <function>&mac.mpo;_destroy_bpfdesc</function> void &mac.mpo;_destroy_bpfdesc struct bpf_d *bpf_d struct label *label &mac.thead; bpf_d Object; bpf descriptor label Label being destroyed Destroy the label on a BPF descriptor. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed. <function>&mac.mpo;_destroy_devfsdirent</function> void &mac.mpo;_destroy_devfsdirent struct devfs_dirent *devfs_dirent struct label *label &mac.thead; devfs_dirent Object; devfs directory entry label Label being destroyed Destroy the label on a devfs entry. In this entry point, a policy module should free any internal storage asociated with label so that it may be destroyed. <function>&mac.mpo;_destroy_ifnet</function> void &mac.mpo;_destroy_ifnet struct ifnet *ifnet struct label *label &mac.thead; ifnet Object; network interface label Label being destroyed Destroy the label on a removed interface. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed. <function>&mac.mpo;_destroy_ipq</function> void &mac.mpo;_destroy_ipq struct ipq *ipq struct label *label &mac.thead; ipq Object; IP reassembly queue label Label being destroyed Destroy the label on an IP fragment queue. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed. <function>&mac.mpo;_destroy_mbuf</function> void &mac.mpo;_destroy_mbuf struct mbuf *mbuf struct label *label &mac.thead; mbuf Object; mbuf label Label being destroyed Destroy the label on an mbuf header. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed. <function>&mac.mpo;_destroy_mount</function> void &mac.mpo;_destroy_mount struct mount *mp struct label *mntlabel struct label *fslabel &mac.thead; mp Object; file system mount point mntlabel Mount point label being destroyed fslabel File system label being destroyed> Destroy the labels on a mount point. In this entry point, a policy module should free the internal storage associated with mntlabel and fslabel so that they may be destroyed. <function>&mac.mpo;_destroy_socket</function> void &mac.mpo;_destroy_socket struct socket *socket struct label *label struct label *peerlabel &mac.thead; socket Object; socket label Socket label being destroyed peerlabel Socket peer label being destroyed Destroy the labels on a socket. In this entry point, a policy module should free any internal storage associated with label and peerlabel so that they may be destroyed. <function>&mac.mpo;_destroy_cred</function> void &mac.mpo;_destroy_cred struct ucred *cred struct label *label &mac.thead; cred Subject; user credential label Label being destroyed Destroy the label on a credential. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed. <function>&mac.mpo;_destroy_temp</function> void &mac.mpo;_destroy_temp struct label *label &mac.thead; label Temporary label being destroyed Destroy a temporary label. In this entry point, a policy module should free any internal storage associated with the temporary label label so that it may be destroyed. <function>&mac.mpo;_destroy_vnode</function> void &mac.mpo;_destroy_vnode struct vnode *vp struct label *label &mac.thead; vp Object; file system object label Label being destroyed Destroy the label on a vnode. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed. <function>&mac.mpo;_externalize</function> void &mac.mpo;_externalize struct label *label struct mac *extmac &mac.thead; label Label to be externalized extmac MAC structure to be filled in Given an internalized subject or object label, fill out an externalized label. This call is permitted to fail. This call will be obsoleted by the new userland and extended attribute interfaces for the MAC framework. <function>&mac.mpo;_internalize</function> void &mac.mpo;_internalize struct label *label struct mac *extmac &mac.thead; label Label to be filled in extmac MAC structure to internalize Given an externalized subject or object label, likely from userland, internalize the label. The entry point implementation should handle incorrect or corrupted labels. This call is permitted to fail. This call will be obsoleted by the new userland and extended attribute interfaces for the MAC framework. Additional Framework API Calls The MAC_SYSCALL entry point provides a policy-multiplexed system call so that policies may provide additional services to user processes without registering specific system calls. The policy name provided during registration is used to demux calls from userland, and the arguments will be forwarded to this entry point. When implementing new services, security modules should be sure to invoke appropriate access control checks from the MAC framework as needed. For example, if a policy implements an augmented signal functionality, it should call the necessary signal access control checks to invoke the MAC framework and other registered policies. Userland APIs The userland API is still under development. Sample Policy Modules The mac_none policy provides sample prototypes and registration of all available policy entry points. The mac_seeotheruids policy provides a simple access control policy without the use of labeling, relying only on information already present in the kernel objects. The mac_biba policy provides a sample information flow based labeled access control policy, assigning labels to all kernel objects. System Integration ... Conclusion The TrustedBSD MAC framework permits kernel modules to augment the system security policy in a highly integrated manner. They may do this based on existing object properties, or based on label data that is maintained with the assistance of the MAC framework. The framework is sufficiently flexible to implement a variety of policy types, including information flow security policies such as MLS and Biba, as well as policies based on existing BSD credentials or file protections. Policy authors may wish to consult this documentation as well as existing security modules when implementing a new security service.