[PATCH v2 6/6] Audit: Add record for multiple object contexts

Casey Schaufler
2025-03-07T18:38:55Z

Create a new audit record AUDIT_MAC_OBJ_CONTEXTS.
An example of the MAC_OBJ_CONTEXTS (1424) record is:

type=MAC_OBJ_CONTEXTS[1424]
msg=audit(1601152467.009:1050):
obj_selinux=unconfined_u:object_r:user_home_t:s0

When an audit event includes a AUDIT_MAC_OBJ_CONTEXTS record
the "obj=" field in other records in the event will be "obj=?".
An AUDIT_MAC_OBJ_CONTEXTS record is supplied when the system has
multiple security modules that may make access decisions based
on an object security context.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
include/linux/audit.h | 7 ++++-
include/linux/lsm_hooks.h | 3 +++
include/linux/security.h | 1 +
include/uapi/linux/audit.h | 1 +
kernel/audit.c | 53 +++++++++++++++++++++++++++++++++++++-
kernel/auditsc.c | 45 ++++++++------------------------
security/security.c | 3 +++
security/selinux/hooks.c | 1 +
security/smack/smack_lsm.c | 1 +
9 files changed, 79 insertions(+), 36 deletions(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index ee3e2ce70c45..0b17acf459f2 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -186,8 +186,10 @@ extern void audit_log_path_denied(int type,
const char *operation);
extern void audit_log_lost(const char *message);

+extern int audit_log_object_context(struct audit_buffer *ab,
+ struct lsm_prop *prop);
extern int audit_log_subject_context(struct audit_buffer *ab,
- struct lsm_prop *blob);
+ struct lsm_prop *prop);
extern int audit_log_task_context(struct audit_buffer *ab);
extern void audit_log_task_info(struct audit_buffer *ab);

@@ -248,6 +250,9 @@ static inline void audit_log_key(struct audit_buffer *ab, char *key)
{ }
static inline void audit_log_path_denied(int type, const char *operation)
{ }
+static inline void audit_log_object_context(struct audit_buffer *ab,
+ struct lsm_prop *prop)
+{ }
static inline int audit_log_subject_context(struct audit_buffer *ab,
struct lsm_prop *prop)
{
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index e4d303ab1f20..464bd8ef4045 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -75,6 +75,8 @@ struct lsm_static_calls_table {
* struct lsm_id - Identify a Linux Security Module.
* @lsm: name of the LSM, must be approved by the LSM maintainers
* @id: LSM ID number from uapi/linux/lsm.h
+ * @subjctx: true if LSM supports a subject context
+ * @objctx: true if LSM supports an object context
*
* Contains the information that identifies the LSM.
*/
@@ -82,6 +84,7 @@ struct lsm_id {
const char *name;
u64 id;
bool subjctx;
+ bool objctx;
};

/*
diff --git a/include/linux/security.h b/include/linux/security.h
index 79a9bf4a7cdd..7c1a6d99e148 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -169,6 +169,7 @@ struct lsm_prop {
extern const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1];
extern u32 lsm_active_cnt;
extern u32 lsm_subjctx_cnt;
+extern u32 lsm_objctx_cnt;
extern const struct lsm_id *lsm_idlist[];

/* These functions are in security/commoncap.c */
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 5ebb5d80363d..8ca58144bcc6 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -147,6 +147,7 @@
#define AUDIT_IPE_CONFIG_CHANGE 1421 /* IPE config change */
#define AUDIT_IPE_POLICY_LOAD 1422 /* IPE policy load */
#define AUDIT_MAC_TASK_CONTEXTS 1423 /* Multiple LSM task contexts */
+#define AUDIT_MAC_OBJ_CONTEXTS 1424 /* Multiple LSM objext contexts */

#define AUDIT_FIRST_KERN_ANOM_MSG 1700
#define AUDIT_LAST_KERN_ANOM_MSG 1799
diff --git a/kernel/audit.c b/kernel/audit.c
index f0c1f0c0b250..054776f29327 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1116,7 +1116,6 @@ static int is_audit_feature_set(int i)
return af.features & AUDIT_FEATURE_TO_MASK(i);
}

-
static int audit_get_feature(struct sk_buff *skb)
{
u32 seq;
@@ -2302,6 +2301,58 @@ int audit_log_task_context(struct audit_buffer *ab)
}
EXPORT_SYMBOL(audit_log_task_context);

+int audit_log_object_context(struct audit_buffer *ab, struct lsm_prop *prop)
+{
+ int i;
+ int rc;
+ int error = 0;
+ char *space = "";
+ struct lsm_context context;
+
+ if (lsm_objctx_cnt < 2) {
+ error = security_lsmprop_to_secctx(prop, &context,
+ LSM_ID_UNDEF);
+ if (error < 0) {
+ if (error != -EINVAL)
+ goto error_path;
+ return error;
+ }
+ audit_log_format(ab, " obj=%s", context.context);
+ security_release_secctx(&context);
+ return 0;
+ }
+ audit_log_format(ab, " obj=?");
+ error = audit_buffer_aux_new(ab, AUDIT_MAC_OBJ_CONTEXTS);
+ if (error)
+ goto error_path;
+
+ for (i = 0; i < lsm_active_cnt; i++) {
+ if (!lsm_idlist[i]->objctx)
+ continue;
+ rc = security_lsmprop_to_secctx(prop, &context,
+ lsm_idlist[i]->id);
+ if (rc < 0) {
+ audit_log_format(ab, "%sobj_%s=?", space,
+ lsm_idlist[i]->name);
+ if (rc != -EINVAL)
+ audit_panic("error in audit_log_object_context");
+ error = rc;
+ } else {
+ audit_log_format(ab, "%sobj_%s=%s", space,
+ lsm_idlist[i]->name, context.context);
+ security_release_secctx(&context);
+ }
+ space = " ";
+ }
+
+ audit_buffer_aux_end(ab);
+ return error;
+
+error_path:
+ audit_panic("error in audit_log_object_context");
+ return error;
+}
+
void audit_log_d_path_exe(struct audit_buffer *ab,
struct mm_struct *mm)
{
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index d98ce7097a2d..82470862ea81 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1098,7 +1098,6 @@ static int audit_log_pid_context(struct audit_context *context, pid_t pid,
char *comm)
{
struct audit_buffer *ab;
- struct lsm_context ctx;
int rc = 0;

ab = audit_log_start(context, GFP_KERNEL, AUDIT_OBJ_PID);
@@ -1108,15 +1107,9 @@ static int audit_log_pid_context(struct audit_context *context, pid_t pid,
audit_log_format(ab, "opid=%d oauid=%d ouid=%d oses=%d", pid,
from_kuid(&init_user_ns, auid),
from_kuid(&init_user_ns, uid), sessionid);
- if (lsmprop_is_set(prop)) {
- if (security_lsmprop_to_secctx(prop, &ctx, LSM_ID_UNDEF) < 0) {
- audit_log_format(ab, " obj=(none)");
- rc = 1;
- } else {
- audit_log_format(ab, " obj=%s", ctx.context);
- security_release_secctx(&ctx);
- }
- }
+ if (lsmprop_is_set(prop) && audit_log_object_context(ab, prop))
+ rc = 1;
+
audit_log_format(ab, " ocomm=");
audit_log_untrustedstring(ab, comm);
audit_log_end(ab);
@@ -1392,16 +1385,8 @@ static void show_special(struct audit_context *context, int *call_panic)
from_kgid(&init_user_ns, context->ipc.gid),
context->ipc.mode);
if (lsmprop_is_set(&context->ipc.oprop)) {
- struct lsm_context lsmctx;
-
- if (security_lsmprop_to_secctx(&context->ipc.oprop,
- &lsmctx,
- LSM_ID_UNDEF) < 0) {
+ if (audit_log_object_context(ab, &context->ipc.oprop))
*call_panic = 1;
- } else {
- audit_log_format(ab, " obj=%s", lsmctx.context);
- security_release_secctx(&lsmctx);
- }
}
if (context->ipc.has_perm) {
audit_log_end(ab);
@@ -1558,18 +1543,9 @@ static void audit_log_name(struct audit_context *context, struct audit_names *n,
from_kgid(&init_user_ns, n->gid),
MAJOR(n->rdev),
MINOR(n->rdev));
- if (lsmprop_is_set(&n->oprop)) {
- struct lsm_context ctx;
-
- if (security_lsmprop_to_secctx(&n->oprop, &ctx,
- LSM_ID_UNDEF) < 0) {
- if (call_panic)
- *call_panic = 2;
- } else {
- audit_log_format(ab, " obj=%s", ctx.context);
- security_release_secctx(&ctx);
- }
- }
+ if (lsmprop_is_set(&n->oprop) &&
+ audit_log_object_context(ab, &n->oprop))
+ *call_panic = 2;

/* log the audit_names record type */
switch (n->type) {
@@ -1780,15 +1756,16 @@ static void audit_log_exit(void)
axs->target_sessionid[i],
&axs->target_ref[i],
axs->target_comm[i]))
- call_panic = 1;
+ call_panic = 1;
}

if (context->target_pid &&
audit_log_pid_context(context, context->target_pid,
context->target_auid, context->target_uid,
context->target_sessionid,
- &context->target_ref, context->target_comm))
- call_panic = 1;
+ &context->target_ref,
+ context->target_comm))
+ call_panic = 1;

if (context->pwd.dentry && context->pwd.mnt) {
ab = audit_log_start(context, GFP_KERNEL, AUDIT_CWD);
diff --git a/security/security.c b/security/security.c
index 8450cc5f82d5..ed48457f8f24 100644
--- a/security/security.c
+++ b/security/security.c
@@ -321,6 +321,7 @@ static void __init initialize_lsm(struct lsm_info *lsm)
*/
u32 lsm_active_cnt __ro_after_init;
u32 lsm_subjctx_cnt __ro_after_init;
+u32 lsm_objctx_cnt __ro_after_init;
const struct lsm_id *lsm_idlist[MAX_LSM_COUNT];

/* Populate ordered LSMs list from comma-separated LSM name list. */
@@ -629,6 +630,8 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
lsm_idlist[lsm_active_cnt++] = lsmid;
if (lsmid->subjctx)
lsm_subjctx_cnt++;
+ if (lsmid->objctx)
+ lsm_objctx_cnt++;
}

for (i = 0; i < count; i++) {
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 1e2e1545eb2e..10b13cd589c5 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -7143,6 +7143,7 @@ static const struct lsm_id selinux_lsmid = {
.name = "selinux",
.id = LSM_ID_SELINUX,
.subjctx = true,
+ .objctx = true,
};

/*
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 75bd62fe1513..1b42ac32d815 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -5058,6 +5058,7 @@ static const struct lsm_id smack_lsmid = {
.name = "smack",
.id = LSM_ID_SMACK,
.subjctx = true,
+ .objctx = true,
};

static struct security_hook_list smack_hooks[] __ro_after_init = {
--
2.47.0