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From: David Howells <dhowells@redhat.com>
To: torvalds@linux-foundation.org, viro@zeniv.linux.org.uk
Cc: Casey Schaufler <casey@schaufler-ca.com>,
	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
Subject: [PATCH 11/17] smack: Implement the watch_key and post_notification hooks [ver #5]
Date: Wed, 18 Mar 2020 15:04:55 +0000	[thread overview]
Message-ID: <158454389492.2863966.1081946626597156477.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <158454378820.2863966.10496767254293183123.stgit@warthog.procyon.org.uk>

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

Also implement the post_notification security hook to make sure that the
notification source is granted Write permission by the watch queue.

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: Casey Schaufler <casey@schaufler-ca.com>
---

 include/linux/lsm_audit.h  |    1 +
 security/smack/smack_lsm.c |   83 +++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 83 insertions(+), 1 deletion(-)

diff --git a/include/linux/lsm_audit.h b/include/linux/lsm_audit.h
index 99d629fd9944..28f23b341c1c 100644
--- a/include/linux/lsm_audit.h
+++ b/include/linux/lsm_audit.h
@@ -75,6 +75,7 @@ struct common_audit_data {
 #define LSM_AUDIT_DATA_IBPKEY	13
 #define LSM_AUDIT_DATA_IBENDPORT 14
 #define LSM_AUDIT_DATA_LOCKDOWN 15
+#define LSM_AUDIT_DATA_NOTIFICATION 16
 	union 	{
 		struct path path;
 		struct dentry *dentry;
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 8c61d175e195..2862fc383473 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -41,6 +41,7 @@
 #include <linux/parser.h>
 #include <linux/fs_context.h>
 #include <linux/fs_parser.h>
+#include <linux/watch_queue.h>
 #include "smack.h"
 
 #define TRANS_TRUE	"TRUE"
@@ -4265,7 +4266,7 @@ static int smack_key_permission(key_ref_t key_ref,
 	if (tkp == NULL)
 		return -EACCES;
 
-	if (smack_privileged_cred(CAP_MAC_OVERRIDE, cred))
+	if (smack_privileged(CAP_MAC_OVERRIDE))
 		return 0;
 
 #ifdef CONFIG_AUDIT
@@ -4311,8 +4312,81 @@ static int smack_key_getsecurity(struct key *key, char **_buffer)
 	return length;
 }
 
+
+#ifdef CONFIG_KEY_NOTIFICATIONS
+/**
+ * smack_watch_key - Smack access to watch a key for notifications.
+ * @key: The key to be watched
+ *
+ * Return 0 if the @watch->cred has permission to read from the key object and
+ * an error otherwise.
+ */
+static int smack_watch_key(struct key *key)
+{
+	struct smk_audit_info ad;
+	struct smack_known *tkp = smk_of_current();
+	int rc;
+
+	if (key == NULL)
+		return -EINVAL;
+	/*
+	 * If the key hasn't been initialized give it access so that
+	 * it may do so.
+	 */
+	if (key->security == NULL)
+		return 0;
+	/*
+	 * This should not occur
+	 */
+	if (tkp == NULL)
+		return -EACCES;
+
+	if (smack_privileged_cred(CAP_MAC_OVERRIDE, current_cred()))
+		return 0;
+
+#ifdef CONFIG_AUDIT
+	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_KEY);
+	ad.a.u.key_struct.key = key->serial;
+	ad.a.u.key_struct.key_desc = key->description;
+#endif
+	rc = smk_access(tkp, key->security, MAY_READ, &ad);
+	rc = smk_bu_note("key watch", tkp, key->security, MAY_READ, rc);
+	return rc;
+}
+#endif /* CONFIG_KEY_NOTIFICATIONS */
 #endif /* CONFIG_KEYS */
 
+#ifdef CONFIG_WATCH_QUEUE
+/**
+ * smack_post_notification - Smack access to post a notification to a queue
+ * @w_cred: The credentials of the watcher.
+ * @cred: The credentials of the event source (may be NULL).
+ * @n: The notification message to be posted.
+ */
+static int smack_post_notification(const struct cred *w_cred,
+				   const struct cred *cred,
+				   struct watch_notification *n)
+{
+	struct smk_audit_info ad;
+	struct smack_known *subj, *obj;
+	int rc;
+
+	/* Always let maintenance notifications through. */
+	if (n->type == WATCH_TYPE_META)
+		return 0;
+
+	if (!cred)
+		return 0;
+	subj = smk_of_task(smack_cred(cred));
+	obj = smk_of_task(smack_cred(w_cred));
+
+	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_NOTIFICATION);
+	rc = smk_access(subj, obj, MAY_WRITE, &ad);
+	rc = smk_bu_note("notification", subj, obj, MAY_WRITE, rc);
+	return rc;
+}
+#endif /* CONFIG_WATCH_QUEUE */
+
 /*
  * Smack Audit hooks
  *
@@ -4701,8 +4775,15 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(key_free, smack_key_free),
 	LSM_HOOK_INIT(key_permission, smack_key_permission),
 	LSM_HOOK_INIT(key_getsecurity, smack_key_getsecurity),
+#ifdef CONFIG_KEY_NOTIFICATIONS
+	LSM_HOOK_INIT(watch_key, smack_watch_key),
+#endif
 #endif /* CONFIG_KEYS */
 
+#ifdef CONFIG_WATCH_QUEUE
+	LSM_HOOK_INIT(post_notification, smack_post_notification),
+#endif
+
  /* Audit hooks */
 #ifdef CONFIG_AUDIT
 	LSM_HOOK_INIT(audit_rule_init, smack_audit_rule_init),



  parent reply	other threads:[~2020-03-18 15:05 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-18 15:03 [PATCH 00/17] pipe: Keyrings, mount and superblock notifications " David Howells
2020-03-18 15:03 ` [PATCH 01/17] uapi: General notification queue definitions " David Howells
2020-03-18 15:03 ` [PATCH 02/17] security: Add hooks to rule on setting a watch " David Howells
2020-03-18 18:56   ` James Morris
2020-03-18 15:03 ` [PATCH 03/17] security: Add a hook for the point of notification insertion " David Howells
2020-03-18 18:57   ` James Morris
2020-03-18 15:03 ` [PATCH 04/17] pipe: Add O_NOTIFICATION_PIPE " David Howells
2020-03-18 15:03 ` [PATCH 05/17] pipe: Add general notification queue support " David Howells
2020-03-18 15:04 ` [PATCH 06/17] watch_queue: Add a key/keyring notification facility " David Howells
2020-03-18 19:04   ` James Morris
2020-03-18 15:04 ` [PATCH 07/17] Add sample notification program " David Howells
2020-03-18 15:04 ` [PATCH 08/17] pipe: Allow buffers to be marked read-whole-or-error for notifications " David Howells
2020-03-18 15:04 ` [PATCH 09/17] pipe: Add notification lossage handling " David Howells
2020-03-18 15:04 ` [PATCH 10/17] selinux: Implement the watch_key security hook " David Howells
2020-03-18 19:06   ` James Morris
2020-03-18 15:04 ` David Howells [this message]
2020-03-18 15:05 ` [PATCH 12/17] watch_queue: Add security hooks to rule on setting mount and sb watches " David Howells
2020-03-18 19:07   ` James Morris
2020-03-18 15:05 ` [PATCH 13/17] watch_queue: Implement mount topology and attribute change notifications " David Howells
2020-04-02 15:19   ` Miklos Szeredi
2020-06-14  3:07     ` Ian Kent
2020-06-15  8:44       ` Miklos Szeredi
2020-07-23 10:48   ` David Howells
2020-08-03  9:29     ` Miklos Szeredi
2020-08-04 11:38       ` Ian Kent
2020-08-04 13:19         ` Miklos Szeredi
2020-08-05  1:53           ` Ian Kent
2020-08-05  7:43             ` Miklos Szeredi
2020-08-05 11:36               ` Ian Kent
2020-08-05 11:56                 ` Miklos Szeredi
2020-07-24 10:19   ` David Howells
2020-07-24 10:44     ` Ian Kent
2020-07-24 11:36     ` David Howells
2020-08-03 10:02       ` Miklos Szeredi
2020-08-03 10:08       ` David Howells
2020-08-03 10:18       ` David Howells
2020-08-03 11:17         ` Miklos Szeredi
2020-08-03 11:49         ` David Howells
2020-08-03 12:01           ` Ian Kent
2020-08-03 12:31           ` David Howells
2020-08-03 14:30             ` Ian Kent
2020-03-18 15:05 ` [PATCH 14/17] watch_queue: sample: Display mount tree " David Howells
2020-03-18 15:05 ` [PATCH 15/17] watch_queue: Introduce a non-repeating system-unique superblock ID " David Howells
2020-03-18 15:05 ` [PATCH 16/17] watch_queue: Add superblock notifications " David Howells
2020-03-18 15:05 ` [PATCH 17/17] watch_queue: sample: Display " David Howells

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