smack: implement logging V3

the following patch, add logging of Smack security decisions.
This is of course very useful to understand what your current smack policy does.
As suggested by Casey, it also now forbids labels with ', " or \

It introduces a '/smack/logging' switch :
0: no logging
1: log denied (default)
2: log accepted
3: log denied&accepted

Signed-off-by: Etienne Basset <etienne.basset@numericable.fr>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 66 insertions, 0 deletions

diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index e03a7e19c73..904af348328 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -41,6 +41,7 @@ enum smk_inos {
 	SMK_AMBIENT	= 7,	/* internet ambient label */
 	SMK_NETLBLADDR	= 8,	/* single label hosts */
 	SMK_ONLYCAP	= 9,	/* the only "capable" label */
+	SMK_LOGGING	= 10,	/* logging */
 };
 
 /*
@@ -1192,6 +1193,69 @@ static const struct file_operations smk_onlycap_ops = {
 };
 
 /**
+ * smk_read_logging - read() for /smack/logging
+ * @filp: file pointer, not actually used
+ * @buf: where to put the result
+ * @cn: maximum to send along
+ * @ppos: where to start
+ *
+ * Returns number of bytes read or error code, as appropriate
+ */
+static ssize_t smk_read_logging(struct file *filp, char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	char temp[32];
+	ssize_t rc;
+
+	if (*ppos != 0)
+		return 0;
+
+	sprintf(temp, "%d\n", log_policy);
+	rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
+	return rc;
+}
+
+/**
+ * smk_write_logging - write() for /smack/logging
+ * @file: file pointer, not actually used
+ * @buf: where to get the data from
+ * @count: bytes sent
+ * @ppos: where to start
+ *
+ * Returns number of bytes written or error code, as appropriate
+ */
+static ssize_t smk_write_logging(struct file *file, const char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	char temp[32];
+	int i;
+
+	if (!capable(CAP_MAC_ADMIN))
+		return -EPERM;
+
+	if (count >= sizeof(temp) || count == 0)
+		return -EINVAL;
+
+	if (copy_from_user(temp, buf, count) != 0)
+		return -EFAULT;
+
+	temp[count] = '\0';
+
+	if (sscanf(temp, "%d", &i) != 1)
+		return -EINVAL;
+	if (i < 0 || i > 3)
+		return -EINVAL;
+	log_policy = i;
+	return count;
+}
+
+
+
+static const struct file_operations smk_logging_ops = {
+	.read		= smk_read_logging,
+	.write		= smk_write_logging,
+};
+/**
  * smk_fill_super - fill the /smackfs superblock
  * @sb: the empty superblock
  * @data: unused
@@ -1221,6 +1285,8 @@ static int smk_fill_super(struct super_block *sb, void *data, int silent)
 			{"netlabel", &smk_netlbladdr_ops, S_IRUGO|S_IWUSR},
 		[SMK_ONLYCAP]	=
 			{"onlycap", &smk_onlycap_ops, S_IRUGO|S_IWUSR},
+		[SMK_LOGGING]	=
+			{"logging", &smk_logging_ops, S_IRUGO|S_IWUSR},
 		/* last one */ {""}
 	};