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diff --git a/sys/kern/kern_shutdown.c b/sys/kern/kern_shutdown.c
--- a/sys/kern/kern_shutdown.c
+++ b/sys/kern/kern_shutdown.c
@@ -129,18 +129,18 @@
int debugger_on_panic = 1;
#endif
SYSCTL_INT(_debug, OID_AUTO, debugger_on_panic,
- CTLFLAG_RWTUN | CTLFLAG_SECURE,
- &debugger_on_panic, 0, "Run debugger on kernel panic");
+ CTLFLAG_RWTUN, &debugger_on_panic, 0,
+ "Run debugger on kernel panic");
static bool debugger_on_recursive_panic = false;
SYSCTL_BOOL(_debug, OID_AUTO, debugger_on_recursive_panic,
- CTLFLAG_RWTUN | CTLFLAG_SECURE,
- &debugger_on_recursive_panic, 0, "Run debugger on recursive kernel panic");
+ CTLFLAG_RWTUN, &debugger_on_recursive_panic, 0,
+ "Run debugger on recursive kernel panic");
int debugger_on_trap = 0;
SYSCTL_INT(_debug, OID_AUTO, debugger_on_trap,
- CTLFLAG_RWTUN | CTLFLAG_SECURE,
- &debugger_on_trap, 0, "Run debugger on kernel trap before panic");
+ CTLFLAG_RWTUN, &debugger_on_trap, 0,
+ "Run debugger on kernel trap before panic");
#ifdef KDB_TRACE
static int trace_on_panic = 1;
diff --git a/sys/kern/subr_kdb.c b/sys/kern/subr_kdb.c
--- a/sys/kern/subr_kdb.c
+++ b/sys/kern/subr_kdb.c
@@ -77,6 +77,7 @@
static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER;
static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER;
+static int kdb_enter_securelevel = 0;
KDB_BACKEND(null, NULL, NULL, NULL, NULL);
@@ -103,7 +104,7 @@
"currently selected KDB backend");
SYSCTL_PROC(_debug_kdb, OID_AUTO, enter,
- CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
+ CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
kdb_sysctl_enter, "I",
"set to enter the debugger");
@@ -133,13 +134,18 @@
"set to cause a stack overflow");
SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger,
- CTLFLAG_RWTUN | CTLFLAG_SECURE,
+ CTLFLAG_RWTUN,
&kdb_break_to_debugger, 0, "Enable break to debugger");
SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger,
- CTLFLAG_RWTUN | CTLFLAG_SECURE,
+ CTLFLAG_RWTUN,
&kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger");
+SYSCTL_INT(_debug_kdb, OID_AUTO, enter_securelevel,
+ CTLFLAG_RWTUN | CTLFLAG_SECURE,
+ &kdb_enter_securelevel, 0,
+ "maximum securelevel to enter a KDB backend");
+
/*
* Flag to indicate to debuggers why the debugger was entered.
*/
@@ -489,6 +495,34 @@
return (EINVAL);
}
+static bool
+kdb_backend_permitted(struct kdb_dbbe *be, struct ucred *cred)
+{
+ int error;
+
+ error = securelevel_gt(cred, kdb_enter_securelevel);
+#ifdef MAC
+ /*
+ * Give MAC a chance to weigh in on the policy: if the securelevel is
+ * not raised, then MAC may veto the backend, otherwise MAC may
+ * explicitly grant access.
+ */
+ if (error == 0) {
+ error = mac_kdb_check_backend(be);
+ if (error != 0) {
+ printf("MAC prevented execution of KDB backend: %s\n",
+ be->dbbe_name);
+ return (false);
+ }
+ } else if (mac_kdb_grant_backend(be) == 0) {
+ error = 0;
+ }
+#endif
+ if (error != 0)
+ printf("refusing to enter KDB with elevated securelevel\n");
+ return (error == 0);
+}
+
/*
* Enter the currently selected debugger. If a message has been provided,
* it is printed first. If the debugger does not support the enter method,
@@ -734,9 +768,7 @@
for (;;) {
#ifdef MAC
- if (mac_kdb_check_backend(be) != 0) {
- printf("MAC prevented execution of KDB backend: %s\n",
- be->dbbe_name);
+ if (!kdb_backend_permitted(be, curthread->td_ucred)) {
/* Unhandled breakpoint traps are fatal. */
handled = 1;
break;
diff --git a/sys/security/mac/mac_framework.h b/sys/security/mac/mac_framework.h
--- a/sys/security/mac/mac_framework.h
+++ b/sys/security/mac/mac_framework.h
@@ -214,6 +214,7 @@
void mac_ipq_update(struct mbuf *m, struct ipq *q);
int mac_kdb_check_backend(struct kdb_dbbe *be);
+int mac_kdb_grant_backend(struct kdb_dbbe *be);
int mac_kenv_check_dump(struct ucred *cred);
int mac_kenv_check_get(struct ucred *cred, char *name);
diff --git a/sys/security/mac/mac_kdb.c b/sys/security/mac/mac_kdb.c
--- a/sys/security/mac/mac_kdb.c
+++ b/sys/security/mac/mac_kdb.c
@@ -39,6 +39,15 @@
#include <security/mac/mac_internal.h>
#include <security/mac/mac_policy.h>
+int
+mac_kdb_grant_backend(struct kdb_dbbe *be)
+{
+ int error = 0;
+
+ MAC_POLICY_GRANT_NOSLEEP(kdb_check_backend, be);
+ return (error);
+}
+
int
mac_kdb_check_backend(struct kdb_dbbe *be)
{

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