linux-kernel - [PATCH v4 1/9] capability: introduce new capable flag NODENYAUDIT

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Message-Id: <20230511142535.732324-1-cgzones@googlemail.com>
Date:   Thu, 11 May 2023 16:25:24 +0200
From:   Christian Göttsche <cgzones@...glemail.com>
To:     selinux@...r.kernel.org
Cc:     Paul Moore <paul@...l-moore.com>,
        John Johansen <john.johansen@...onical.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Christian Brauner <brauner@...nel.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Dave Chinner <dchinner@...hat.com>,
        Nathan Lynch <nathanl@...ux.ibm.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Roberto Sassu <roberto.sassu@...wei.com>,
        Micah Morton <mortonm@...omium.org>,
        Frederick Lawler <fred@...udflare.com>,
        Günther Noack <gnoack3000@...il.com>,
        linux-kernel@...r.kernel.org, apparmor@...ts.ubuntu.com,
        linux-security-module@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH v4 1/9] capability: introduce new capable flag NODENYAUDIT

Introduce a new capable flag, CAP_OPT_NODENYAUDIT, 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.

Suggested-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
---
 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 e2734e9e44d5..629c775ec297 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -67,6 +67,8 @@ struct watch_notification;
 #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_NODENYAUDIT 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 326a51838ef2..98120dd62ca7 100644
--- a/security/apparmor/capability.c
+++ b/security/apparmor/capability.c
@@ -108,7 +108,8 @@ static int audit_caps(struct common_audit_data *sa, 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_NODENYAUDIT bit determines whether audit
+ *	record is generated
  * @sa: 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_NODENYAUDIT) && error)) {
 		if (!COMPLAIN_MODE(profile))
 			return error;
 		/* audit the cap request in complain mode but note that it
@@ -142,7 +143,8 @@ static int profile_capable(struct aa_profile *profile, int cap,
  * aa_capable - test permission to use capability
  * @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_NODENYAUDIT 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 79b4890e9936..0730edf2f5f1 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1571,7 +1571,7 @@ 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;
@@ -1590,11 +1590,13 @@ 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_NODENYAUDIT) && rc))
+		return rc;
+
+	rc2 = avc_audit(sid, sid, sclass, av, &avd, rc, &ad);
+	if (rc2)
+		return rc2;
+
 	return rc;
 }
 
-- 
2.40.1