UBUNTU: SAUCE: apparmor4.0.0 [24/90]: LSM stacking v39: Audit: Add record for multiple task security contexts

BugLink: http://bugs.launchpad.net/bugs/2028253

Create a new audit record AUDIT_MAC_TASK_CONTEXTS.
An example of the MAC_TASK_CONTEXTS (1420) record is:

    type=MAC_TASK_CONTEXTS[1420]
    msg=audit(1600880931.832:113)
    subj_apparmor=unconfined
    subj_smack=_

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

Acked-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
(cherry picked from commit 47750a2eb56fb2e1f9d2e055a3e70b393b10b528
https://git.launchpad.net/~apparmor-dev/ubuntu-kernel-next)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

include/linux/lsm_hooks.h

@@ -47,12 +47,14 @@ struct security_hook_heads {
  * 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
+ * @lsmblob: indicates the LSM has an entry in struct lsmblob
  *
  * Contains the information that identifies the LSM.
  */
 struct lsm_id {
 	const char	*name;
 	u64		id;
+	bool		lsmblob;
 };
 
 /*

include/linux/security.h

@@ -192,6 +192,7 @@ struct lsmblob {
 
 extern const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1];
 extern u32 lsm_active_cnt;
+extern u32 lsm_blob_cnt;
 extern const struct lsm_id *lsm_idlist[];
 
 /* These functions are in security/commoncap.c */

include/uapi/linux/audit.h

@@ -143,6 +143,7 @@
 #define AUDIT_MAC_UNLBL_STCDEL	1417	/* NetLabel: del a static label */
 #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_FIRST_KERN_ANOM_MSG   1700
 #define AUDIT_LAST_KERN_ANOM_MSG    1799

kernel/audit.c

@@ -54,6 +54,7 @@
 #include <net/netlink.h>
 #include <linux/skbuff.h>
 #include <linux/security.h>
+#include <linux/lsm_hooks.h>
 #include <linux/freezer.h>
 #include <linux/pid_namespace.h>
 #include <net/netns/generic.h>
@@ -2245,21 +2246,51 @@ int audit_log_task_context(struct audit_buffer *ab)
 {
 	struct lsmcontext ctx;
 	struct lsmblob blob;
+	bool space = false;
 	int error;
+	int i;
 
 	security_current_getlsmblob_subj(&blob);
 	if (!lsmblob_is_set(&blob))
 		return 0;
 
-	error = security_lsmblob_to_secctx(&blob, &ctx, LSM_ID_UNDEF);
-	if (error < 0) {
-		if (error != -EINVAL)
-			goto error_path;
+	if (lsm_blob_cnt < 2) {
+		error = security_lsmblob_to_secctx(&blob, &ctx, LSM_ID_UNDEF);
+		if (error < 0) {
+			if (error != -EINVAL)
+				goto error_path;
+			return 0;
+		}
+		audit_log_format(ab, " subj=%s", ctx.context);
+		security_release_secctx(&ctx);
 		return 0;
 	}
+	/* Multiple LSMs provide contexts. Include an aux record. */
+	audit_log_format(ab, " subj=?");
+	error = audit_buffer_aux_new(ab, AUDIT_MAC_TASK_CONTEXTS);
+	if (error)
+		goto error_path;
 
-	audit_log_format(ab, " subj=%s", ctx.context);
-	security_release_secctx(&ctx);
+	for (i = 0; i < lsm_active_cnt; i++) {
+		if (!lsm_idlist[i]->lsmblob)
+			continue;
+		error = security_lsmblob_to_secctx(&blob, &ctx,
+						   lsm_idlist[i]->id);
+		if (error < 0) {
+			if (error == -EOPNOTSUPP)
+				continue;
+			audit_log_format(ab, "%ssubj_%s=?", space ? " " : "",
+					 lsm_idlist[i]->name);
+			if (error != -EINVAL)
+				audit_panic("error in audit_log_task_context");
+		} else {
+			audit_log_format(ab, "%ssubj_%s=%s", space ? " " : "",
+					 lsm_idlist[i]->name, ctx.context);
+			security_release_secctx(&ctx);
+		}
+		space = true;
+	}
+	audit_buffer_aux_end(ab);
 	return 0;
 
 error_path:

security/apparmor/lsm.c

@@ -1426,6 +1426,7 @@ struct lsm_blob_sizes apparmor_blob_sizes __ro_after_init = {
 static const struct lsm_id apparmor_lsmid = {
 	.name = "apparmor",
 	.id = LSM_ID_APPARMOR,
+	.lsmblob = true,
 };
 
 static struct security_hook_list apparmor_hooks[] __ro_after_init = {

security/bpf/hooks.c

@@ -19,6 +19,7 @@ static struct security_hook_list bpf_lsm_hooks[] __ro_after_init = {
 static const struct lsm_id bpf_lsmid = {
 	.name = "bpf",
 	.id = LSM_ID_BPF,
+	.lsmblob = true,
 };
 
 static int __init bpf_lsm_init(void)

security/security.c

@@ -270,6 +270,7 @@ static void __init initialize_lsm(struct lsm_info *lsm)
  * Current index to use while initializing the lsm id list.
  */
 u32 lsm_active_cnt __ro_after_init;
+u32 lsm_blob_cnt __ro_after_init;
 const struct lsm_id *lsm_idlist[LSM_CONFIG_COUNT];
 
 /**
@@ -600,6 +601,8 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
 		if (lsm_active_cnt >= LSM_CONFIG_COUNT)
 			panic("%s Too many LSMs registered.\n", __func__);
 		lsm_idlist[lsm_active_cnt++] = lsmid;
+		if (lsmid->lsmblob)
+			lsm_blob_cnt++;
 	}
 
 	for (i = 0; i < count; i++) {

security/selinux/hooks.c

@@ -7148,6 +7148,7 @@ static int selinux_uring_cmd(struct io_uring_cmd *ioucmd)
 static const struct lsm_id selinux_lsmid = {
 	.name = "selinux",
 	.id = LSM_ID_SELINUX,
+	.lsmblob = true,
 };
 
 /*

security/smack/smack_lsm.c

@@ -5070,6 +5070,7 @@ struct lsm_blob_sizes smack_blob_sizes __ro_after_init = {
 static const struct lsm_id smack_lsmid = {
 	.name = "smack",
 	.id = LSM_ID_SMACK,
+	.lsmblob = true,
 };
 
 static struct security_hook_list smack_hooks[] __ro_after_init = {