eCryptfs: check for eCryptfs cipher support at mount

The issue occurs when eCryptfs is mounted with a cipher supported by
the crypto subsystem but not by eCryptfs. The mount succeeds and an
error does not occur until a write. This change checks for eCryptfs
cipher support at mount time.

Resolves Launchpad issue #338914, reported by Tyler Hicks in 03/2009.
https://bugs.launchpad.net/ecryptfs/+bug/338914

Signed-off-by: Tim Sally <tsally@atomicpeace.com>
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index df217dc9f1d9..923f6aa09cb3 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -279,6 +279,7 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options,
         char *fnek_src;
         char *cipher_key_bytes_src;
         char *fn_cipher_key_bytes_src;
+        u8 cipher_code;
 
         *check_ruid = 0;
 
@@ -420,6 +421,18 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options,
             && !fn_cipher_key_bytes_set)
                 mount_crypt_stat->global_default_fn_cipher_key_bytes =
                         mount_crypt_stat->global_default_cipher_key_size;
+
+        cipher_code = ecryptfs_code_for_cipher_string(
+                mount_crypt_stat->global_default_cipher_name,
+                mount_crypt_stat->global_default_cipher_key_size);
+        if (!cipher_code) {
+                ecryptfs_printk(KERN_ERR,
+                                "eCryptfs doesn't support cipher: %s",
+                                mount_crypt_stat->global_default_cipher_name);
+                rc = -EINVAL;
+                goto out;
+        }
+
         mutex_lock(&key_tfm_list_mutex);
         if (!ecryptfs_tfm_exists(mount_crypt_stat->global_default_cipher_name,
                                  NULL)) {