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head/sys/security/mac_veriexec_parser/mac_veriexec_parser.c

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/*-
* Copyright (c) 2019 Stormshield.
* Copyright (c) 2019 Semihalf.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/ctype.h>
#include <sys/eventhandler.h>
#include <sys/fcntl.h>
#include <sys/lock.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/vnode.h>
#include <crypto/sha2/sha256.h>
#include <crypto/sha2/sha384.h>
#include <crypto/sha2/sha512.h>
#include <security/mac_veriexec/mac_veriexec.h>
#include <security/mac_veriexec/mac_veriexec_internal.h>
/* The following are based on sbin/veriexec */
struct fingerprint_type {
const char *fp_type;
int fp_size;
};
struct fp_flag {
const char *flag_name;
int flag;
};
static const struct fingerprint_type fp_table[] = {
{"sha256=", SHA256_DIGEST_LENGTH},
#if MAXFINGERPRINTLEN >= SHA384_DIGEST_LENGTH
{"sha384=", SHA384_DIGEST_LENGTH},
#endif
#if MAXFINGERPRINTLEN >= SHA512_DIGEST_LENGTH
{"sha512=", SHA512_DIGEST_LENGTH},
#endif
{NULL, 0}
};
static const struct fp_flag flags_table[] = {
{"indirect", VERIEXEC_INDIRECT},
{"no_ptrace", VERIEXEC_NOTRACE},
{"trusted", VERIEXEC_TRUSTED},
{"no_fips", VERIEXEC_NOFIPS},
{NULL, 0}
};
extern struct mtx ve_mutex;
static unsigned char hexchar_to_byte(unsigned char c);
static int hexstring_to_bin(unsigned char *buf);
static int get_flags(const char *entry);
static int get_fp(const char *entry, char **type,
unsigned char **digest, int *flags);
static int verify_digest(const char *data, size_t len,
const unsigned char *expected_hash);
static int open_file(const char *path, struct nameidata *nid);
static char *read_manifest(char *path, unsigned char *digest);
static int parse_entry(char *entry, char *prefix);
static int parse_manifest(char *path, unsigned char *hash, char *prefix);
static unsigned char
hexchar_to_byte(unsigned char c)
{
if (isdigit(c))
return (c - '0');
return (isupper(c) ? c - 'A' + 10 : c - 'a' + 10);
}
static int
hexstring_to_bin(unsigned char *buf)
{
size_t i, len;
unsigned char byte;
len = strlen(buf);
for (i = 0; i < len / 2; i++) {
if (!isxdigit(buf[2 * i]) || !isxdigit(buf[2 * i + 1]))
return (EINVAL);
byte = hexchar_to_byte(buf[2 * i]) << 4;
byte += hexchar_to_byte(buf[2 * i + 1]);
buf[i] = byte;
}
return (0);
}
static int
get_flags(const char *entry)
{
int i;
int result = 0;
for (i = 0; flags_table[i].flag_name != NULL; i++)
if (strstr(entry, flags_table[i].flag_name) != NULL)
result |= flags_table[i].flag;
return (result);
}
/*
* Parse a single line of manifest looking for a digest and its type.
* We expect it to be in form of "path shaX=hash".
* The line will be split into path, hash type and hash value.
*/
static int
get_fp(const char *entry, char **type, unsigned char **digest, int *flags)
{
char *delimiter;
char *local_digest;
char *fp_type;
char *prev_fp_type;
size_t min_len;
int i;
delimiter = NULL;
fp_type = NULL;
prev_fp_type = NULL;
for (i = 0; fp_table[i].fp_type != NULL; i++) {
fp_type = strstr(entry, fp_table[i].fp_type);
/* Look for the last "shaX=hash" in line */
while (fp_type != NULL) {
prev_fp_type = fp_type;
fp_type++;
fp_type = strstr(fp_type, fp_table[i].fp_type);
}
fp_type = prev_fp_type;
if (fp_type != NULL) {
if (fp_type == entry || fp_type[-1] != ' ')
return (EINVAL);
/*
* The entry should contain at least
* fp_type and digest in hexadecimal form.
*/
min_len = strlen(fp_table[i].fp_type) +
2 * fp_table[i].fp_size;
if (strnlen(fp_type, min_len) < min_len)
return (EINVAL);
local_digest = &fp_type[strlen(fp_table[i].fp_type)];
delimiter = &local_digest[2 * fp_table[i].fp_size];
/*
* Make sure that digest is followed by
* some kind of delimiter.
*/
if (*delimiter != '\n' &&
*delimiter != '\0' &&
*delimiter != ' ')
return (EINVAL);
/*
* Does the entry contain flags we need to parse?
*/
if (*delimiter == ' ' && flags != NULL)
*flags = get_flags(delimiter);
/*
* Split entry into three parts:
* path, fp_type and digest.
*/
local_digest[-1] = '\0';
*delimiter = '\0';
fp_type[-1] = '\0';
break;
}
}
if (fp_type == NULL)
return (EINVAL);
if (type != NULL)
*type = fp_type;
if (digest != NULL)
*digest = local_digest;
return (0);
}
/*
* Currently we verify manifest using sha256.
* In future another env with hash type could be introduced.
*/
static int
verify_digest(const char *data, size_t len, const unsigned char *expected_hash)
{
SHA256_CTX ctx;
unsigned char hash[SHA256_DIGEST_LENGTH];
SHA256_Init(&ctx);
SHA256_Update(&ctx, data, len);
SHA256_Final(hash, &ctx);
return (memcmp(expected_hash, hash, SHA256_DIGEST_LENGTH));
}
static int
open_file(const char *path, struct nameidata *nid)
{
int flags, rc;
flags = FREAD;
pwd_ensure_dirs();
NDINIT(nid, LOOKUP, 0, UIO_SYSSPACE, path, curthread);
rc = vn_open(nid, &flags, 0, NULL);
NDFREE(nid, NDF_ONLY_PNBUF);
if (rc != 0)
return (rc);
return (0);
}
/*
* Read the manifest from location specified in path and verify its digest.
*/
static char*
read_manifest(char *path, unsigned char *digest)
{
struct nameidata nid;
struct vattr va;
char *data;
ssize_t bytes_read, resid;
int rc;
data = NULL;
bytes_read = 0;
rc = open_file(path, &nid);
if (rc != 0)
goto fail;
rc = VOP_GETATTR(nid.ni_vp, &va, curthread->td_ucred);
if (rc != 0)
goto fail;
data = (char *)malloc(va.va_size + 1, M_VERIEXEC, M_WAITOK);
while (bytes_read < va.va_size) {
rc = vn_rdwr(
UIO_READ, nid.ni_vp, data,
va.va_size - bytes_read, bytes_read,
UIO_SYSSPACE, IO_NODELOCKED,
curthread->td_ucred, NOCRED, &resid, curthread);
if (rc != 0)
goto fail;
bytes_read = va.va_size - resid;
}
data[bytes_read] = '\0';
VOP_UNLOCK(nid.ni_vp, 0);
(void)vn_close(nid.ni_vp, FREAD, curthread->td_ucred, curthread);
/*
* If digest is wrong someone might be trying to fool us.
*/
if (verify_digest(data, va.va_size, digest))
panic("Manifest hash doesn't match expected value!");
return (data);
fail:
if (data != NULL)
free(data, M_VERIEXEC);
return (NULL);
}
/*
* Process single line.
* First split it into path, digest_type and digest.
* Then try to open the file and insert its fingerprint into metadata store.
*/
static int
parse_entry(char *entry, char *prefix)
{
struct nameidata nid;
struct vattr va;
char path[MAXPATHLEN];
char *fp_type;
unsigned char *digest;
int rc, is_exec, flags;
fp_type = NULL;
digest = NULL;
flags = 0;
rc = get_fp(entry, &fp_type, &digest, &flags);
if (rc != 0)
return (rc);
rc = hexstring_to_bin(digest);
if (rc != 0)
return (rc);
if (strnlen(entry, MAXPATHLEN) == MAXPATHLEN)
return (EINVAL);
/* If the path is not absolute prepend it with a prefix */
if (prefix != NULL && entry[0] != '/') {
rc = snprintf(path, MAXPATHLEN, "%s/%s",
prefix, entry);
if (rc < 0)
return (-rc);
} else {
strcpy(path, entry);
}
rc = open_file(path, &nid);
NDFREE(&nid, NDF_ONLY_PNBUF);
if (rc != 0)
return (rc);
rc = VOP_GETATTR(nid.ni_vp, &va, curthread->td_ucred);
if (rc != 0)
goto out;
is_exec = (va.va_mode & VEXEC);
mtx_lock(&ve_mutex);
rc = mac_veriexec_metadata_add_file(
is_exec == 0,
va.va_fsid, va.va_fileid, va.va_gen,
digest, flags, fp_type, 1);
mtx_unlock(&ve_mutex);
out:
VOP_UNLOCK(nid.ni_vp, 0);
vn_close(nid.ni_vp, FREAD, curthread->td_ucred, curthread);
return (rc);
}
/*
* Look for manifest in env that have beed passed by loader.
* This routine should be called right after the rootfs is mounted.
*/
static int
parse_manifest(char *path, unsigned char *hash, char *prefix)
{
char *data;
char *entry;
char *next_entry;
int rc, success_count;
data = NULL;
success_count = 0;
rc = 0;
data = read_manifest(path, hash);
if (data == NULL) {
rc = EIO;
goto out;
}
entry = data;
while (entry != NULL) {
next_entry = strchr(entry, '\n');
if (next_entry != NULL) {
*next_entry = '\0';
next_entry++;
}
if (entry[0] == '\n' || entry[0] == '\0') {
entry = next_entry;
continue;
}
if ((rc = parse_entry(entry, prefix)))
printf("mac_veriexec_parser: Warning: Failed to parse"
" entry with rc:%d, entry:\"%s\"\n", rc, entry);
else
success_count++;
entry = next_entry;
}
rc = 0;
out:
if (data != NULL)
free(data, M_VERIEXEC);
if (success_count == 0)
rc = EINVAL;
return (rc);
}
static void
parse_manifest_event(void *dummy)
{
char *manifest_path;
char *manifest_prefix;
unsigned char *manifest_hash;
int rc;
/* If the envs are not set fail silently */
manifest_path = kern_getenv("veriexec.manifest_path");
if (manifest_path == NULL)
return;
manifest_hash = kern_getenv("veriexec.manifest_hash");
if (manifest_hash == NULL) {
freeenv(manifest_path);
return;
}
manifest_prefix = kern_getenv("veriexec.manifest_prefix");
if (strlen(manifest_hash) != 2 * SHA256_DIGEST_LENGTH)
panic("veriexec.manifest_hash has incorrect size");
rc = hexstring_to_bin(manifest_hash);
if (rc != 0)
panic("mac_veriexec: veriexec.loader.manifest_hash"
" doesn't contain a hash in hexadecimal form");
rc = parse_manifest(manifest_path, manifest_hash, manifest_prefix);
if (rc != 0)
panic("mac_veriexec: Failed to parse manifest err=%d", rc);
mtx_lock(&ve_mutex);
mac_veriexec_set_state(
VERIEXEC_STATE_LOADED | VERIEXEC_STATE_ACTIVE |
VERIEXEC_STATE_LOCKED | VERIEXEC_STATE_ENFORCE);
mtx_unlock(&ve_mutex);
freeenv(manifest_path);
freeenv(manifest_hash);
if (manifest_prefix != NULL)
freeenv(manifest_prefix);
}
EVENTHANDLER_DEFINE(mountroot, parse_manifest_event, NULL, 0);