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Hash: SHA1
This patch removes the hardcoding of CBC mode in eCryptfs and adds a
mount option allowing one to specify the desired mode of operation.
Currently this defaults to cbc, but should would with any plain block
cipher mode supported by the kernel. We've been testing with ecb to
ensure we've found any implicit assumptions about cbc.
Future work will involve supporting AEAD modes (GCM) and adding in
integrity checking code.
As this is our first kernel patch, we'd like feedback on what we've
done right and what we've done wrong, not only in code, but also
anything related to the patch submission itself.
Signed-off-by: William Morrison <camocrazed@xxxxxxxxx>
- ---
diff -uprN -X ecryptfs_base/Documentation/dontdiff ecryptfs_base/fs/ecryptfs/crypto.c ecryptfs/fs/ecryptfs/crypto.c
- --- ecryptfs_base/fs/ecryptfs/crypto.c 2013-06-03 07:49:51.734430193 -0400
+++ ecryptfs/fs/ecryptfs/crypto.c 2013-05-23 17:51:37.814355879 -0400
@@ -743,7 +743,8 @@ int ecryptfs_init_crypt_ctx(struct ecryp
}
mutex_lock(&crypt_stat->cs_tfm_mutex);
rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
- - crypt_stat->cipher, "cbc");
+ crypt_stat->cipher,
+ crypt_stat->cipher_mode);
if (rc)
goto out_unlock;
crypt_stat->tfm = crypto_alloc_blkcipher(full_alg_name, 0,
@@ -753,8 +754,9 @@ int ecryptfs_init_crypt_ctx(struct ecryp
rc = PTR_ERR(crypt_stat->tfm);
crypt_stat->tfm = NULL;
ecryptfs_printk(KERN_ERR, "cryptfs: init_crypt_ctx(): "
- - "Error initializing cipher [%s]\n",
- - crypt_stat->cipher);
+ "Error initializing cipher [%s] and mode [%s]\n",
+ crypt_stat->cipher,
+ crypt_stat->cipher_mode);
goto out_unlock;
}
crypto_blkcipher_set_flags(crypt_stat->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
@@ -916,6 +918,7 @@ static void ecryptfs_set_default_crypt_s
mount_crypt_stat);
ecryptfs_set_default_sizes(crypt_stat);
strcpy(crypt_stat->cipher, ECRYPTFS_DEFAULT_CIPHER);
+ strcpy(crypt_stat->cipher_mode, ECRYPTFS_DEFAULT_CIPHER_MODE);
crypt_stat->key_size = ECRYPTFS_DEFAULT_KEY_BYTES;
crypt_stat->flags &= ~(ECRYPTFS_KEY_VALID);
crypt_stat->file_version = ECRYPTFS_FILE_VERSION;
@@ -949,6 +952,7 @@ int ecryptfs_new_file_context(struct ino
&ecryptfs_superblock_to_private(
ecryptfs_inode->i_sb)->mount_crypt_stat;
int cipher_name_len;
+ int cipher_mode_name_len;
int rc = 0;
ecryptfs_set_default_crypt_stat_vals(crypt_stat, mount_crypt_stat);
@@ -968,6 +972,12 @@ int ecryptfs_new_file_context(struct ino
mount_crypt_stat->global_default_cipher_name,
cipher_name_len);
crypt_stat->cipher[cipher_name_len] = '\0';
+ cipher_mode_name_len =
+ strlen(mount_crypt_stat->global_default_cipher_mode_name);
+ memcpy(crypt_stat->cipher_mode,
+ mount_crypt_stat->global_default_cipher_mode_name,
+ cipher_mode_name_len);
+ crypt_stat->cipher_mode[cipher_mode_name_len] = '\0';
crypt_stat->key_size =
mount_crypt_stat->global_default_cipher_key_size;
ecryptfs_generate_new_key(crypt_stat);
diff -uprN -X ecryptfs_base/Documentation/dontdiff ecryptfs_base/fs/ecryptfs/ecryptfs_kernel.h ecryptfs/fs/ecryptfs/ecryptfs_kernel.h
- --- ecryptfs_base/fs/ecryptfs/ecryptfs_kernel.h 2013-06-03 07:49:51.734430193 -0400
+++ ecryptfs/fs/ecryptfs/ecryptfs_kernel.h 2013-05-23 17:51:37.814355879 -0400
@@ -124,6 +124,7 @@ ecryptfs_get_key_payload_data(struct key
#define ECRYPTFS_MAX_KEYSET_SIZE 1024
#define ECRYPTFS_MAX_CIPHER_NAME_SIZE 32
+#define ECRYPTFS_MAX_CIPHER_MODE_NAME_SIZE 32
#define ECRYPTFS_MAX_NUM_ENC_KEYS 64
#define ECRYPTFS_MAX_IV_BYTES 16 /* 128 bits */
#define ECRYPTFS_SALT_BYTES 2
@@ -133,6 +134,7 @@ ecryptfs_get_key_payload_data(struct key
#define ECRYPTFS_SIZE_AND_MARKER_BYTES (ECRYPTFS_FILE_SIZE_BYTES \
+ MAGIC_ECRYPTFS_MARKER_SIZE_BYTES)
#define ECRYPTFS_DEFAULT_CIPHER "aes"
+#define ECRYPTFS_DEFAULT_CIPHER_MODE "cbc"
#define ECRYPTFS_DEFAULT_KEY_BYTES 16
#define ECRYPTFS_DEFAULT_HASH "md5"
#define ECRYPTFS_TAG_70_DIGEST ECRYPTFS_DEFAULT_HASH
@@ -237,6 +239,7 @@ struct ecryptfs_crypt_stat {
struct crypto_hash *hash_tfm; /* Crypto context for generating
* the initialization vectors */
unsigned char cipher[ECRYPTFS_MAX_CIPHER_NAME_SIZE];
+ unsigned char cipher_mode[ECRYPTFS_MAX_CIPHER_MODE_NAME_SIZE];
unsigned char key[ECRYPTFS_MAX_KEY_BYTES];
unsigned char root_iv[ECRYPTFS_MAX_IV_BYTES];
struct list_head keysig_list;
@@ -338,6 +341,8 @@ struct ecryptfs_mount_crypt_stat {
size_t global_default_fn_cipher_key_bytes;
unsigned char global_default_cipher_name[ECRYPTFS_MAX_CIPHER_NAME_SIZE
+ 1];
+ unsigned char global_default_cipher_mode_name[
+ ECRYPTFS_MAX_CIPHER_MODE_NAME_SIZE + 1];
unsigned char global_default_fn_cipher_name[
ECRYPTFS_MAX_CIPHER_NAME_SIZE + 1];
char global_default_fnek_sig[ECRYPTFS_SIG_SIZE_HEX + 1];
diff -uprN -X ecryptfs_base/Documentation/dontdiff ecryptfs_base/fs/ecryptfs/keystore.c ecryptfs/fs/ecryptfs/keystore.c
- --- ecryptfs_base/fs/ecryptfs/keystore.c 2013-06-03 07:49:51.734430193 -0400
+++ ecryptfs/fs/ecryptfs/keystore.c 2013-06-03 10:45:56.142519966 -0400
@@ -1467,6 +1467,9 @@ parse_tag_3_packet(struct ecryptfs_crypt
crypt_stat->key_size =
(*new_auth_tok)->session_key.encrypted_key_size;
}
+ strncpy(crypt_stat->cipher_mode,
+ crypt_stat->mount_crypt_stat->global_default_cipher_mode_name,
+ ECRYPTFS_MAX_CIPHER_MODE_NAME_SIZE);
rc = ecryptfs_init_crypt_ctx(crypt_stat);
if (rc)
goto out_free;
diff -uprN -X ecryptfs_base/Documentation/dontdiff ecryptfs_base/fs/ecryptfs/main.c ecryptfs/fs/ecryptfs/main.c
- --- ecryptfs_base/fs/ecryptfs/main.c 2013-06-03 07:49:51.734430193 -0400
+++ ecryptfs/fs/ecryptfs/main.c 2013-06-03 10:54:26.570524304 -0400
@@ -171,6 +171,7 @@ void ecryptfs_put_lower_file(struct inod
enum { ecryptfs_opt_sig, ecryptfs_opt_ecryptfs_sig,
ecryptfs_opt_cipher, ecryptfs_opt_ecryptfs_cipher,
+ ecryptfs_opt_cipher_mode, ecryptfs_opt_ecryptfs_cipher_mode,
ecryptfs_opt_ecryptfs_key_bytes,
ecryptfs_opt_passthrough, ecryptfs_opt_xattr_metadata,
ecryptfs_opt_encrypted_view, ecryptfs_opt_fnek_sig,
@@ -183,7 +184,9 @@ static const match_table_t tokens = {
{ecryptfs_opt_sig, "sig=%s"},
{ecryptfs_opt_ecryptfs_sig, "ecryptfs_sig=%s"},
{ecryptfs_opt_cipher, "cipher=%s"},
+ {ecryptfs_opt_cipher_mode, "cipher_mode=%s"},
{ecryptfs_opt_ecryptfs_cipher, "ecryptfs_cipher=%s"},
+ {ecryptfs_opt_ecryptfs_cipher_mode, "ecryptfs_cipher_mode=%s"},
{ecryptfs_opt_ecryptfs_key_bytes, "ecryptfs_key_bytes=%u"},
{ecryptfs_opt_passthrough, "ecryptfs_passthrough"},
{ecryptfs_opt_xattr_metadata, "ecryptfs_xattr_metadata"},
@@ -258,10 +261,13 @@ static void ecryptfs_init_mount_crypt_st
static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options,
uid_t *check_ruid)
{
+ const char *mode_white_list[] = {"cbc", "ecb", "gcm"};
char *p;
+ int i = 0;
int rc = 0;
int sig_set = 0;
int cipher_name_set = 0;
+ int cipher_mode_name_set = 0;
int fn_cipher_name_set = 0;
int cipher_key_bytes;
int cipher_key_bytes_set = 0;
@@ -274,6 +280,8 @@ static int ecryptfs_parse_options(struct
char *sig_src;
char *cipher_name_dst;
char *cipher_name_src;
+ char *cipher_mode_name_dst;
+ char *cipher_mode_name_src;
char *fn_cipher_name_dst;
char *fn_cipher_name_src;
char *fnek_dst;
@@ -317,6 +325,18 @@ static int ecryptfs_parse_options(struct
cipher_name_dst[ECRYPTFS_MAX_CIPHER_NAME_SIZE] = '\0';
cipher_name_set = 1;
break;
+ case ecryptfs_opt_cipher_mode:
+ case ecryptfs_opt_ecryptfs_cipher_mode:
+ cipher_mode_name_src = args[0].from;
+ cipher_mode_name_dst =
+ mount_crypt_stat->
+ global_default_cipher_mode_name;
+ strncpy(cipher_mode_name_dst, cipher_mode_name_src,
+ ECRYPTFS_MAX_CIPHER_MODE_NAME_SIZE);
+ cipher_mode_name_dst[
+ ECRYPTFS_MAX_CIPHER_MODE_NAME_SIZE] = '\0';
+ cipher_mode_name_set = 1;
+ break;
case ecryptfs_opt_ecryptfs_key_bytes:
cipher_key_bytes_src = args[0].from;
cipher_key_bytes =
@@ -412,6 +432,14 @@ static int ecryptfs_parse_options(struct
strcpy(mount_crypt_stat->global_default_cipher_name,
ECRYPTFS_DEFAULT_CIPHER);
}
+ if (!cipher_mode_name_set) {
+ int cipher_mode_name_len = strlen(ECRYPTFS_DEFAULT_CIPHER_MODE);
+
+ BUG_ON(cipher_mode_name_len >=
+ ECRYPTFS_MAX_CIPHER_MODE_NAME_SIZE);
+ strcpy(mount_crypt_stat->global_default_cipher_mode_name,
+ ECRYPTFS_DEFAULT_CIPHER_MODE);
+ }
if ((mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)
&& !fn_cipher_name_set)
strcpy(mount_crypt_stat->global_default_fn_cipher_name,
@@ -434,6 +462,22 @@ static int ecryptfs_parse_options(struct
goto out;
}
+ rc = -EINVAL;
+ for (i = 0; i < ARRAY_SIZE(mode_white_list); i++) {
+ if (strcmp(mount_crypt_stat->global_default_cipher_mode_name,
+ mode_white_list[i]) == 0) {
+ rc = 0;
+ break;
+ }
+ }
+ if (rc) {
+ ecryptfs_printk(KERN_ERR,
+ "eCryptfs doesn't support cipher mode: %s",
+ mount_crypt_stat->
+ global_default_cipher_mode_name);
+ goto out;
+ }
+
mutex_lock(&key_tfm_list_mutex);
if (!ecryptfs_tfm_exists(mount_crypt_stat->global_default_cipher_name,
NULL)) {
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