linux-kernel - [PATCH] Smack: getting the Smack security context of keys

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Date:	Tue, 17 Feb 2015 15:41:22 +0100
From:	José Bollo <jose.bollo@...n.eurogiciel.org>
To:	Casey Schaufler <casey@...aufler-ca.com>,
	James Morris <james.l.morris@...cle.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH] Smack: getting the Smack security context of keys

With this commit, the LSM Smack implements the LSM
side part of the system call keyctl with the action
code KEYCTL_GET_SECURITY.

It is now possible to get the context of, for example,
the user session key using the command "keyctl security @s".

Signed-off-by: José Bollo <jose.bollo@...n.eurogiciel.org>
---
 security/smack/smack_lsm.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index fa64740..c1ff996 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3208,6 +3208,35 @@ static int smack_key_permission(key_ref_t
key_ref,
        return smk_access(tsp, keyp->security,
                                 MAY_READWRITE, &ad);
 }
+
+/*
+ * smack_key_getsecurity - Smack label tagging the key
+ * @key points to the key to be queried
+ * @_buffer points to a pointer that should be set to point to the
+ * resulting string (if no label or an error occurs).
+ * Return the length of the string (including terminating NUL) or -ve
if
+ * an error.
+ * May also return 0 (and a NULL buffer pointer) if there is no label.
+ */
+static int smack_key_getsecurity(struct key *key, char **_buffer)
+{
+       int length;
+       char *copy;
+
+       if (key->security == NULL) {
+               *_buffer = NULL;
+               return 0;
+       }
+
+       length = (int)strlen(key->security) + 1;
+       copy = kmalloc((size_t)length, GFP_KERNEL);
+       if (copy == NULL)
+               return -ENOMEM;
+
+       memcpy(copy, key->security, (size_t)length);
+       *_buffer = copy;
+       return length;
+}
 #endif /* CONFIG_KEYS */
 
 /*
@@ -3514,6 +3543,7 @@ struct security_operations smack_ops = {
        .key_alloc =                    smack_key_alloc,
        .key_free =                     smack_key_free,
        .key_permission =               smack_key_permission,
+       .key_getsecurity =              smack_key_getsecurity,
 #endif /* CONFIG_KEYS */
 
  /* Audit hooks */
-- 
2.1.2


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