crypto: arc4 - Add internal state

The arc4 algorithm has always had internal state.  It's been buggy
from day one in that the state has been stored in the shared tfm
object.  That means two users sharing the same tfm will end up
affecting each other's output, or worse, they may end up with the
same output.

Fix this by declaring an internal state and storing the state there
instead of within the tfm context.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/arc4.c

@@ -14,6 +14,8 @@
 #include <linux/module.h>
 #include <linux/sched.h>
 
+#define ARC4_ALIGN __alignof__(struct arc4_ctx)
+
 static int crypto_arc4_setkey(struct crypto_lskcipher *tfm, const u8 *in_key,
 			      unsigned int key_len)
 {
@@ -23,10 +25,15 @@ static int crypto_arc4_setkey(struct crypto_lskcipher *tfm, const u8 *in_key,
 }
 
 static int crypto_arc4_crypt(struct crypto_lskcipher *tfm, const u8 *src,
-			     u8 *dst, unsigned nbytes, u8 *iv, u32 flags)
+			     u8 *dst, unsigned nbytes, u8 *siv, u32 flags)
 {
 	struct arc4_ctx *ctx = crypto_lskcipher_ctx(tfm);
 
+	if (!(flags & CRYPTO_LSKCIPHER_FLAG_CONT))
+		memcpy(siv, ctx, sizeof(*ctx));
+
+	ctx = (struct arc4_ctx *)siv;
+
 	arc4_crypt(ctx, dst, src, nbytes);
 	return 0;
 }
@@ -45,9 +52,11 @@ static struct lskcipher_alg arc4_alg = {
 	.co.base.cra_priority		=	100,
 	.co.base.cra_blocksize		=	ARC4_BLOCK_SIZE,
 	.co.base.cra_ctxsize		=	sizeof(struct arc4_ctx),
+	.co.base.cra_alignmask		=	ARC4_ALIGN - 1,
 	.co.base.cra_module		=	THIS_MODULE,
 	.co.min_keysize			=	ARC4_MIN_KEY_SIZE,
 	.co.max_keysize			=	ARC4_MAX_KEY_SIZE,
+	.co.statesize			=	sizeof(struct arc4_ctx),
 	.setkey				=	crypto_arc4_setkey,
 	.encrypt			=	crypto_arc4_crypt,
 	.decrypt			=	crypto_arc4_crypt,