[PATCH v30 26/28] Audit: Add record for multiple object security contexts

Casey Schaufler
2021-11-24T02:12:38Z

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

type=UNKNOWN[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=?".
A 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 | 61 ++++++++++++++++++++++++++++++++++++++
kernel/auditsc.c | 37 ++++-------------------
4 files changed, 72 insertions(+), 32 deletions(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 943584128399..8381afb4f49e 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -192,6 +192,8 @@ extern void audit_log_path_denied(int type,
extern void audit_log_lost(const char *message);

extern int audit_log_task_context(struct audit_buffer *ab);
+extern void audit_log_object_context(struct audit_buffer *ab,
+ struct lsmblob *blob);
extern void audit_log_task_info(struct audit_buffer *ab);

extern int audit_update_lsm_rules(void);
@@ -255,6 +257,9 @@ static inline int audit_log_task_context(struct audit_buffer *ab)
{
return 0;
}
+static inline void audit_log_object_context(struct audit_buffer *ab,
+ struct lsmblob *blob);
+{ }
static inline void audit_log_task_info(struct audit_buffer *ab)
{ }

diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 86ad3da4f0d4..116566d0fc03 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 6c93545a14f3..55fdcc2c88e4 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -199,6 +199,7 @@ struct audit_context_entry {
int type; /* Audit record type */
union {
struct lsmblob mac_task_context;
+ struct lsmblob mac_obj_context;
};
};

@@ -2190,6 +2191,44 @@ int audit_log_task_context(struct audit_buffer *ab)
}
EXPORT_SYMBOL(audit_log_task_context);

+void audit_log_object_context(struct audit_buffer *ab, struct lsmblob *blob)
+{
+ struct audit_context_entry *ace;
+ struct lsmcontext context;
+ int error;
+
+ 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);
+ return;
+ }
+ /*
+ * If there is more than one security module that has a
+ * object "context" it's necessary to put the object data
+ * into a separate record to maintain compatibility.
+ */
+ audit_log_format(ab, " obj=?");
+ ace = kzalloc(sizeof(*ace), GFP_KERNEL);
+ if (ace) {
+ INIT_LIST_HEAD(&ace->list);
+ ace->type = AUDIT_MAC_OBJ_CONTEXTS;
+ ace->mac_obj_context = *blob;
+ list_add(&ace->list, &ab->aux_records);
+ return;
+ }
+ error = -ENOMEM;
+
+error_path:
+ audit_panic("error in audit_log_object_context");
+}
+EXPORT_SYMBOL(audit_log_object_context);
+
void audit_log_d_path_exe(struct audit_buffer *ab,
struct mm_struct *mm)
{
@@ -2497,6 +2536,28 @@ void audit_log_end(struct audit_buffer *ab)
}
}
break;
+ case AUDIT_MAC_OBJ_CONTEXTS:
+ for (i = 0; i < LSMBLOB_ENTRIES; i++) {
+ if (entry->mac_obj_context.secid[i] == 0)
+ continue;
+ rc = security_secid_to_secctx(
+ &entry->mac_obj_context,
+ &lcontext, i);
+ if (rc) {
+ if (rc != -EINVAL)
+ audit_panic("error in audit_log_end");
+ audit_log_format(mab, "%sobj_%s=\"?\"",
+ i ? " " : "",
+ lsm_slot_to_name(i));
+ } else {
+ audit_log_format(mab, "%sobj_%s=\"%s\"",
+ i ? " " : "",
+ lsm_slot_to_name(i),
+ lcontext.context);
+ security_release_secctx(&lcontext);
+ }
+ }
+ break;
default:
audit_panic("Unknown type in audit_log_end");
break;
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index c128f7e73e89..dc8531a79174 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1111,7 +1111,6 @@ static int audit_log_pid_context(struct audit_context *context, pid_t pid,
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);
@@ -1121,15 +1120,8 @@ 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 (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);
@@ -1364,18 +1356,10 @@ 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);
@@ -1527,19 +1511,8 @@ 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) {