[PATCH v33 27/29] Audit: Add record for multiple object security contexts

[Casey Schaufler <casey@schaufler-ca.com>]

Create a new audit record AUDIT_MAC_OBJ_CONTEXTS.
An example of the MAC_OBJ_CONTEXTS (1421) record is:

    type=MAC_OBJ_CONTEXTS[1421]
    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      |  5 +++
 include/uapi/linux/audit.h |  1 +
 kernel/audit.c             | 47 +++++++++++++++++++++++
 kernel/auditsc.c           | 79 ++++++++++++--------------------------
 4 files changed, 77 insertions(+), 55 deletions(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 14849d5f84b4..1b05eb2dbe77 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -191,6 +191,8 @@ extern void		    audit_log_path_denied(int type,
 						  const char *operation);
 extern void		    audit_log_lost(const char *message);
 
+extern void audit_log_object_context(struct audit_buffer *ab,
+				     struct lsmblob *blob);
 extern int audit_log_task_context(struct audit_buffer *ab);
 extern void audit_log_task_info(struct audit_buffer *ab);
 
@@ -251,6 +253,9 @@ 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 lsmblob *blob)
+{ }
 static inline int audit_log_task_context(struct audit_buffer *ab)
 {
 	return 0;
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index af0aaccfaf57..d25d76b29e3c 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -144,6 +144,7 @@
 #define AUDIT_MAC_CALIPSO_ADD	1418	/* NetLabel: add CALIPSO DOI entry */
 #define AUDIT_MAC_CALIPSO_DEL	1419	/* NetLabel: del CALIPSO DOI entry */
 #define AUDIT_MAC_TASK_CONTEXTS	1420	/* Multiple LSM task contexts */
+#define AUDIT_MAC_OBJ_CONTEXTS	1421	/* 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 ad825af203cf..ac92e7fc5aa6 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -2202,6 +2202,53 @@ static void audit_buffer_aux_end(struct audit_buffer *ab)
 	ab->skb = skb_peek(&ab->skb_list);
 }
 
+void audit_log_object_context(struct audit_buffer *ab, struct lsmblob *blob)
+{
+	int i;
+	int error;
+	struct lsmcontext context;
+
+	if (!lsm_multiple_contexts()) {
+		error = security_secid_to_secctx(blob, &context, LSMBLOB_FIRST);
+		if (error) {
+			if (error != -EINVAL)
+				goto error_path;
+			return;
+		}
+		audit_log_format(ab, " obj=%s", context.context);
+		security_release_secctx(&context);
+	} else {
+		audit_log_format(ab, " obj=?");
+		error = audit_buffer_aux_new(ab, AUDIT_MAC_OBJ_CONTEXTS);
+		if (error)
+			goto error_path;
+
+		for (i = 0; i < LSMBLOB_ENTRIES; i++) {
+			if (blob->secid[i] == 0)
+				continue;
+			error = security_secid_to_secctx(blob, &context, i);
+			if (error) {
+				if (error != -EINVAL)
+					audit_panic("error in audit_log_object_context");
+				audit_log_format(ab, "%sobj_%s=?",
+						 i ? " " : "",
+						 lsm_slot_to_name(i));
+			} else {
+				audit_log_format(ab, "%sobj_%s=%s",
+						 i ? " " : "",
+						 lsm_slot_to_name(i),
+						 context.context);
+				security_release_secctx(&context);
+			}
+		}
+
+		audit_buffer_aux_end(ab);
+	}
+	return;
+
+error_path:
+	audit_panic("error in audit_log_object_context");
+}
 
 int audit_log_task_context(struct audit_buffer *ab)
 {
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 7848e7351cf9..923e4e3a5697 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1114,36 +1114,25 @@ static inline void audit_free_context(struct audit_context *context)
 	kfree(context);
 }
 
-static int audit_log_pid_context(struct audit_context *context, pid_t pid,
-				 kuid_t auid, kuid_t uid,
-				 unsigned int sessionid,
-				 struct lsmblob *blob, char *comm)
+static void audit_log_pid_context(struct audit_context *context, pid_t pid,
+				  kuid_t auid, kuid_t uid,
+				  unsigned int sessionid,
+				  struct lsmblob *blob, char *comm)
 {
 	struct audit_buffer *ab;
-	struct lsmcontext lsmctx;
-	int rc = 0;
 
 	ab = audit_log_start(context, GFP_KERNEL, AUDIT_OBJ_PID);
 	if (!ab)
-		return rc;
+		return;
 
 	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 (lsmblob_is_set(blob)) {
-		if (security_secid_to_secctx(blob, &lsmctx, LSMBLOB_FIRST)) {
-			audit_log_format(ab, " obj=(none)");
-			rc = 1;
-		} else {
-			audit_log_format(ab, " obj=%s", lsmctx.context);
-			security_release_secctx(&lsmctx);
-		}
-	}
+	if (lsmblob_is_set(blob))
+		audit_log_object_context(ab, blob);
 	audit_log_format(ab, " ocomm=");
 	audit_log_untrustedstring(ab, comm);
 	audit_log_end(ab);
-
-	return rc;
 }
 
 static void audit_log_execve_info(struct audit_context *context,
@@ -1373,18 +1362,10 @@ static void show_special(struct audit_context *context, int *call_panic)
 				 from_kgid(&init_user_ns, context->ipc.gid),
 				 context->ipc.mode);
 		if (osid) {
-			struct lsmcontext lsmcxt;
 			struct lsmblob blob;
 
 			lsmblob_init(&blob, osid);
-			if (security_secid_to_secctx(&blob, &lsmcxt,
-						     LSMBLOB_FIRST)) {
-				audit_log_format(ab, " osid=%u", osid);
-				*call_panic = 1;
-			} else {
-				audit_log_format(ab, " obj=%s", lsmcxt.context);
-				security_release_secctx(&lsmcxt);
-			}
+			audit_log_object_context(ab, &blob);
 		}
 		if (context->ipc.has_perm) {
 			audit_log_end(ab);
@@ -1536,19 +1517,8 @@ 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 (lsmblob_is_set(&n->lsmblob)) {
-		struct lsmcontext lsmctx;
-
-		if (security_secid_to_secctx(&n->lsmblob, &lsmctx,
-					     LSMBLOB_FIRST)) {
-			audit_log_format(ab, " osid=?");
-			if (call_panic)
-				*call_panic = 2;
-		} else {
-			audit_log_format(ab, " obj=%s", lsmctx.context);
-			security_release_secctx(&lsmctx);
-		}
-	}
+	if (lsmblob_is_set(&n->lsmblob))
+		audit_log_object_context(ab, &n->lsmblob);
 
 	/* log the audit_names record type */
 	switch (n->type) {
@@ -1753,21 +1723,20 @@ static void audit_log_exit(void)
 		struct audit_aux_data_pids *axs = (void *)aux;
 
 		for (i = 0; i < axs->pid_count; i++)
-			if (audit_log_pid_context(context, axs->target_pid[i],
-						  axs->target_auid[i],
-						  axs->target_uid[i],
-						  axs->target_sessionid[i],
-						  &axs->target_lsm[i],
-						  axs->target_comm[i]))
-				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_lsm, context->target_comm))
-			call_panic = 1;
+			audit_log_pid_context(context, axs->target_pid[i],
+					      axs->target_auid[i],
+					      axs->target_uid[i],
+					      axs->target_sessionid[i],
+					      &axs->target_lsm[i],
+					      axs->target_comm[i]);
+	}
+
+	if (context->target_pid)
+		audit_log_pid_context(context, context->target_pid,
+				      context->target_auid, context->target_uid,
+				      context->target_sessionid,
+				      &context->target_lsm,
+				      context->target_comm);
 
 	if (context->pwd.dentry && context->pwd.mnt) {
 		ab = audit_log_start(context, GFP_KERNEL, AUDIT_CWD);
-- 
2.31.1