Commit 76435548 authored by John Johansen's avatar John Johansen Committed by Tyler Hicks
Browse files

Ecryptfs: Add mount option to check uid of device being mounted = expect uid 



Close a TOCTOU race for mounts done via ecryptfs-mount-private.  The mount
source (device) can be raced when the ownership test is done in userspace.
Provide Ecryptfs a means to force the uid check at mount time.

Signed-off-by: default avatarJohn Johansen <john.johansen@canonical.com>
Cc: <stable@kernel.org>
Signed-off-by: default avatarTyler Hicks <tyhicks@linux.vnet.ibm.com>
parent 99b373ff

fs/ecryptfs/main.c

+21 −2
Original line number Diff line number Diff line
@@ -175,6 +175,7 @@ enum { ecryptfs_opt_sig, ecryptfs_opt_ecryptfs_sig, 
       ecryptfs_opt_encrypted_view, ecryptfs_opt_fnek_sig,

       ecryptfs_opt_fn_cipher, ecryptfs_opt_fn_cipher_key_bytes,

       ecryptfs_opt_unlink_sigs, ecryptfs_opt_mount_auth_tok_only,

       ecryptfs_opt_check_dev_ruid,

       ecryptfs_opt_err };



static const match_table_t tokens = {
@@ -191,6 +192,7 @@ static const match_table_t tokens = { 
	{ecryptfs_opt_fn_cipher_key_bytes, "ecryptfs_fn_key_bytes=%u"},

	{ecryptfs_opt_unlink_sigs, "ecryptfs_unlink_sigs"},

	{ecryptfs_opt_mount_auth_tok_only, "ecryptfs_mount_auth_tok_only"},

	{ecryptfs_opt_check_dev_ruid, "ecryptfs_check_dev_ruid"},

	{ecryptfs_opt_err, NULL}

};
@@ -236,6 +238,7 @@ static void ecryptfs_init_mount_crypt_stat( 
 * ecryptfs_parse_options

 * @sb: The ecryptfs super block

 * @options: The options passed to the kernel

 * @check_ruid: set to 1 if device uid should be checked against the ruid

 *

 * Parse mount options:

 * debug=N 	   - ecryptfs_verbosity level for debug output
@@ -251,7 +254,8 @@ static void ecryptfs_init_mount_crypt_stat( 
 *

 * Returns zero on success; non-zero on error

 */

static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options)

static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options,

				  uid_t *check_ruid)

{

	char *p;

	int rc = 0;
@@ -276,6 +280,8 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options) 
	char *cipher_key_bytes_src;

	char *fn_cipher_key_bytes_src;



	*check_ruid = 0;



	if (!options) {

		rc = -EINVAL;

		goto out;
@@ -380,6 +386,9 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options) 
			mount_crypt_stat->flags |=

				ECRYPTFS_GLOBAL_MOUNT_AUTH_TOK_ONLY;

			break;

		case ecryptfs_opt_check_dev_ruid:

			*check_ruid = 1;

			break;

		case ecryptfs_opt_err:

		default:

			printk(KERN_WARNING
@@ -475,6 +484,7 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags 
	const char *err = "Getting sb failed";

	struct inode *inode;

	struct path path;

	uid_t check_ruid;

	int rc;



	sbi = kmem_cache_zalloc(ecryptfs_sb_info_cache, GFP_KERNEL);
@@ -483,7 +493,7 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags 
		goto out;

	}



	rc = ecryptfs_parse_options(sbi, raw_data);

	rc = ecryptfs_parse_options(sbi, raw_data, &check_ruid);

	if (rc) {

		err = "Error parsing options";

		goto out;
@@ -521,6 +531,15 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags 
			"known incompatibilities\n");

		goto out_free;

	}



	if (check_ruid && path.dentry->d_inode->i_uid != current_uid()) {

		rc = -EPERM;

		printk(KERN_ERR "Mount of device (uid: %d) not owned by "

		       "requested user (uid: %d)\n",

		       path.dentry->d_inode->i_uid, current_uid());

		goto out_free;

	}



	ecryptfs_set_superblock_lower(s, path.dentry->d_sb);

	s->s_maxbytes = path.dentry->d_sb->s_maxbytes;

	s->s_blocksize = path.dentry->d_sb->s_blocksize;

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