crypto: skcipher - Copy iv from desc even for 0-len walks

Some ciphers actually support encrypting zero length plaintexts. For example, many AEAD modes support this. The resulting ciphertext for those winds up being only the authentication tag, which is a result of the key, the iv, the additional data, and the fact that the plaintext had zero length. The blkcipher constructors won't copy the IV to the right place, however, when using a zero length input, resulting in some significant problems when ciphers call their initialization routines, only to find that the ->iv parameter is uninitialized. One such example of this would be using chacha20poly1305 with a zero length input, which then calls chacha20, which calls the key setup routine, which eventually OOPSes due to the uninitialized ->iv member. Signed-off-by: Jason A. Donenfeld <[email protected]> Cc: <[email protected]> Signed-off-by: Herbert Xu <[email protected]>
kyagi · Dec 9, 2015 · 70d906b · 70d906b
1 parent 7996094
commit 70d906b
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Showing 2 changed files with 2 additions and 2 deletions.
diff --git a/crypto/ablkcipher.c b/crypto/ablkcipher.c
@@ -277,12 +277,12 @@ static int ablkcipher_walk_first(struct ablkcipher_request *req,
 	if (WARN_ON_ONCE(in_irq()))
 		return -EDEADLK;
 
+	walk->iv = req->info;
 	walk->nbytes = walk->total;
 	if (unlikely(!walk->total))
 		return 0;
 
 	walk->iv_buffer = NULL;
-	walk->iv = req->info;
 	if (unlikely(((unsigned long)walk->iv & alignmask))) {
 		int err = ablkcipher_copy_iv(walk, tfm, alignmask);
 

diff --git a/crypto/blkcipher.c b/crypto/blkcipher.c
@@ -326,12 +326,12 @@ static int blkcipher_walk_first(struct blkcipher_desc *desc,
 	if (WARN_ON_ONCE(in_irq()))
 		return -EDEADLK;
 
+	walk->iv = desc->info;
 	walk->nbytes = walk->total;
 	if (unlikely(!walk->total))
 		return 0;
 
 	walk->buffer = NULL;
-	walk->iv = desc->info;
 	if (unlikely(((unsigned long)walk->iv & walk->alignmask))) {
 		int err = blkcipher_copy_iv(walk);
 		if (err)