linux-kernel - [RFC PATCH 10/17] selinux: Implement the watch

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Message-ID: <158375632431.334846.18088471578251578185.stgit@warthog.procyon.org.uk>
Date:   Mon, 09 Mar 2020 12:18:44 +0000
From:   David Howells <dhowells@...hat.com>
To:     torvalds@...ux-foundation.org, viro@...iv.linux.org.uk
Cc:     Stephen Smalley <sds@...ho.nsa.gov>, dhowells@...hat.com,
        dhowells@...hat.com, casey@...aufler-ca.com, sds@...ho.nsa.gov,
        nicolas.dichtel@...nd.com, raven@...maw.net, christian@...uner.io,
        andres@...razel.de, jlayton@...hat.com, dray@...hat.com,
        kzak@...hat.com, keyrings@...r.kernel.org,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 10/17] selinux: Implement the watch_key security hook [ver
 #4]

Implement the watch_key security hook to make sure that a key grants the
caller View permission in order to set a watch on a key.

For the moment, the watch_devices security hook is left unimplemented as
it's not obvious what the object should be since the queue is global and
didn't previously exist.

Signed-off-by: David Howells <dhowells@...hat.com>
Acked-by: Stephen Smalley <sds@...ho.nsa.gov>
---

 security/selinux/hooks.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 4b6991e178d3..95be16d3f47a 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6563,6 +6563,17 @@ static int selinux_key_getsecurity(struct key *key, char **_buffer)
 	*_buffer = context;
 	return rc;
 }
+
+#ifdef CONFIG_KEY_NOTIFICATIONS
+static int selinux_watch_key(struct key *key)
+{
+	struct key_security_struct *ksec = key->security;
+	u32 sid = current_sid();
+
+	return avc_has_perm(&selinux_state,
+			    sid, ksec->sid, SECCLASS_KEY, KEY_NEED_VIEW, NULL);
+}
+#endif
 #endif
 
 #ifdef CONFIG_SECURITY_INFINIBAND
@@ -7078,6 +7089,9 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(key_free, selinux_key_free),
 	LSM_HOOK_INIT(key_permission, selinux_key_permission),
 	LSM_HOOK_INIT(key_getsecurity, selinux_key_getsecurity),
+#ifdef CONFIG_KEY_NOTIFICATIONS
+	LSM_HOOK_INIT(watch_key, selinux_watch_key),
+#endif
 #endif
 
 #ifdef CONFIG_AUDIT