[BLOCK] dm-crypt: benbi IV, big endian narrow block count for LRW-32-AES
LRW-32-AES needs a certain IV. This IV should be provided dm-crypt.
The block cipher mode could, in principle generate the correct IV from
the plain IV, but I think that it is cleaner to supply the right IV
directly.
The sector -> narrow block calculation uses a shift for performance reasons.
This shift is computed in .ctr and stored in cc->iv_gen_private (as a void *).
Signed-off-by: Rik Snel <rsnel@cube.dyndns.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index ed2d4ef..6dbaeee 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -20,6 +20,7 @@
#include <asm/atomic.h>
#include <linux/scatterlist.h>
#include <asm/page.h>
+#include <asm/unaligned.h>
#include "dm.h"
@@ -113,6 +114,9 @@
* encrypted with the bulk cipher using a salt as key. The salt
* should be derived from the bulk cipher's key via hashing.
*
+ * benbi: the 64-bit "big-endian 'narrow block'-count", starting at 1
+ * (needed for LRW-32-AES and possible other narrow block modes)
+ *
* plumb: unimplemented, see:
* http://article.gmane.org/gmane.linux.kernel.device-mapper.dm-crypt/454
*/
@@ -209,6 +213,44 @@
return 0;
}
+static int crypt_iv_benbi_ctr(struct crypt_config *cc, struct dm_target *ti,
+ const char *opts)
+{
+ unsigned int bs = crypto_blkcipher_blocksize(cc->tfm);
+ int log = long_log2(bs);
+
+ /* we need to calculate how far we must shift the sector count
+ * to get the cipher block count, we use this shift in _gen */
+
+ if (1 << log != bs) {
+ ti->error = "cypher blocksize is not a power of 2";
+ return -EINVAL;
+ }
+
+ if (log > 9) {
+ ti->error = "cypher blocksize is > 512";
+ return -EINVAL;
+ }
+
+ cc->iv_gen_private = (void *)(9 - log);
+
+ return 0;
+}
+
+static void crypt_iv_benbi_dtr(struct crypt_config *cc)
+{
+ cc->iv_gen_private = NULL;
+}
+
+static int crypt_iv_benbi_gen(struct crypt_config *cc, u8 *iv, sector_t sector)
+{
+ memset(iv, 0, cc->iv_size - sizeof(u64)); /* rest is cleared below */
+ put_unaligned(cpu_to_be64(((u64)sector << (u32)cc->iv_gen_private) + 1),
+ (__be64 *)(iv + cc->iv_size - sizeof(u64)));
+
+ return 0;
+}
+
static struct crypt_iv_operations crypt_iv_plain_ops = {
.generator = crypt_iv_plain_gen
};
@@ -219,6 +261,11 @@
.generator = crypt_iv_essiv_gen
};
+static struct crypt_iv_operations crypt_iv_benbi_ops = {
+ .ctr = crypt_iv_benbi_ctr,
+ .dtr = crypt_iv_benbi_dtr,
+ .generator = crypt_iv_benbi_gen
+};
static int
crypt_convert_scatterlist(struct crypt_config *cc, struct scatterlist *out,
@@ -768,7 +815,7 @@
cc->tfm = tfm;
/*
- * Choose ivmode. Valid modes: "plain", "essiv:<esshash>".
+ * Choose ivmode. Valid modes: "plain", "essiv:<esshash>", "benbi".
* See comments at iv code
*/
@@ -778,6 +825,8 @@
cc->iv_gen_ops = &crypt_iv_plain_ops;
else if (strcmp(ivmode, "essiv") == 0)
cc->iv_gen_ops = &crypt_iv_essiv_ops;
+ else if (strcmp(ivmode, "benbi") == 0)
+ cc->iv_gen_ops = &crypt_iv_benbi_ops;
else {
ti->error = "Invalid IV mode";
goto bad2;