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Subject: [PATCH 10/17] selinux: Implement the watch_key security hook [ver #5]
From:   David Howells <dhowells@redhat.com>
To:     torvalds@linux-foundation.org, viro@zeniv.linux.org.uk
Cc:     Stephen Smalley <sds@tycho.nsa.gov>, dhowells@redhat.com,
        casey@schaufler-ca.com, sds@tycho.nsa.gov,
        nicolas.dichtel@6wind.com, raven@themaw.net, christian@brauner.io,
        andres@anarazel.de, jlayton@redhat.com, dray@redhat.com,
        kzak@redhat.com, keyrings@vger.kernel.org,
        linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Wed, 18 Mar 2020 15:04:46 +0000
Message-ID: <158454388633.2863966.17799427202351674141.stgit@warthog.procyon.org.uk>
In-Reply-To: <158454378820.2863966.10496767254293183123.stgit@warthog.procyon.org.uk>
References: <158454378820.2863966.10496767254293183123.stgit@warthog.procyon.org.uk>
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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@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.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 1659b59fb5d7..2c19ac4d7894 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