Re: [PATCH v33 27/29] Audit: Add record for multiple object security contexts
From: Casey Schaufler
Date: Tue Mar 15 2022 - 20:23:31 EST
On 3/15/2022 4:47 PM, Paul Moore wrote:
On Thu, Mar 10, 2022 at 7:01 PM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote:
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@xxxxxxxxxxxxxxxx>
---
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/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");
+}
The comment from patch 26/29 regarding the audit_panic() placement
also applies to audit_log_object_context().
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);
While we lose the "osid=X" in case of failure, the secid/SID is a
private kernel value meaning it was always of questionable value.
I could come up with a change to audit_log_object_context() that
would put out an osid= in the single security module case. I would
prefer not to if that would be acceptable.
--
paul-moore.com