[PATCH 01/10] capability: introduce new capable flag CAP_OPT_NOAUDIT_ONDENY

[Christian Göttsche]

Introduce a new capable flag, CAP_OPT_NOAUDIT_ONDENY, to not generate
an audit event if the requested capability is not granted.  This will be
used in a new capable_any() functionality to reduce the number of
necessary capable calls.

Handle the flag accordingly in AppArmor and SELinux.

CC: linux-block@xxxxxxxxxxxxxxx
Suggested-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
---
v5:
   rename flag to CAP_OPT_NOAUDIT_ONDENY, suggested by Serge:
     https://lore.kernel.org/all/20230606190013.GA640488@xxxxxxxxxxxxxxx/
---
 include/linux/security.h       |  2 ++
 security/apparmor/capability.c |  8 +++++---
 security/selinux/hooks.c       | 14 ++++++++------
 3 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/include/linux/security.h b/include/linux/security.h
index 41a8f667bdfa..c60cae78ff8b 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -70,6 +70,8 @@ struct lsm_ctx;
 #define CAP_OPT_NOAUDIT BIT(1)
 /* If capable is being called by a setid function */
 #define CAP_OPT_INSETID BIT(2)
+/* If capable should audit the security request for authorized requests only */
+#define CAP_OPT_NOAUDIT_ONDENY BIT(3)
 
 /* LSM Agnostic defines for security_sb_set_mnt_opts() flags */
 #define SECURITY_LSM_NATIVE_LABELS	1
diff --git a/security/apparmor/capability.c b/security/apparmor/capability.c
index 9934df16c843..08c9c9a0fc19 100644
--- a/security/apparmor/capability.c
+++ b/security/apparmor/capability.c
@@ -108,7 +108,8 @@ static int audit_caps(struct apparmor_audit_data *ad, struct aa_profile *profile
  * profile_capable - test if profile allows use of capability @cap
  * @profile: profile being enforced    (NOT NULL, NOT unconfined)
  * @cap: capability to test if allowed
- * @opts: CAP_OPT_NOAUDIT bit determines whether audit record is generated
+ * @opts: CAP_OPT_NOAUDIT/CAP_OPT_NOAUDIT_ONDENY bit determines whether audit
+ *	record is generated
  * @ad: audit data (MAY BE NULL indicating no auditing)
  *
  * Returns: 0 if allowed else -EPERM
@@ -126,7 +127,7 @@ static int profile_capable(struct aa_profile *profile, int cap,
 	else
 		error = -EPERM;
 
-	if (opts & CAP_OPT_NOAUDIT) {
+	if ((opts & CAP_OPT_NOAUDIT) || ((opts & CAP_OPT_NOAUDIT_ONDENY) && error)) {
 		if (!COMPLAIN_MODE(profile))
 			return error;
 		/* audit the cap request in complain mode but note that it
@@ -143,7 +144,8 @@ static int profile_capable(struct aa_profile *profile, int cap,
  * @subj_cred: cred we are testing capability against
  * @label: label being tested for capability (NOT NULL)
  * @cap: capability to be tested
- * @opts: CAP_OPT_NOAUDIT bit determines whether audit record is generated
+ * @opts: CAP_OPT_NOAUDIT/CAP_OPT_NOAUDIT_ONDENY bit determines whether audit
+ *	record is generated
  *
  * Look up capability in profile capability set.
  *
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3448454c82d0..1a2c7c1a89be 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1624,7 +1624,7 @@ static int cred_has_capability(const struct cred *cred,
 	u16 sclass;
 	u32 sid = cred_sid(cred);
 	u32 av = CAP_TO_MASK(cap);
-	int rc;
+	int rc, rc2;
 
 	ad.type = LSM_AUDIT_DATA_CAP;
 	ad.u.cap = cap;
@@ -1643,11 +1643,13 @@ static int cred_has_capability(const struct cred *cred,
 	}
 
 	rc = avc_has_perm_noaudit(sid, sid, sclass, av, 0, &avd);
-	if (!(opts & CAP_OPT_NOAUDIT)) {
-		int rc2 = avc_audit(sid, sid, sclass, av, &avd, rc, &ad);
-		if (rc2)
-			return rc2;
-	}
+	if ((opts & CAP_OPT_NOAUDIT) || ((opts & CAP_OPT_NOAUDIT_ONDENY) && rc))
+		return rc;
+
+	rc2 = avc_audit(sid, sid, sclass, av, &avd, rc, &ad);
+	if (rc2)
+		return rc2;
+
 	return rc;
 }
 
-- 
2.43.0