crypto: chacha - move existing library code into lib/crypto

Currently, our generic ChaCha implementation consists of a permute
function in lib/chacha.c that operates on the 64-byte ChaCha state
directly [and which is always included into the core kernel since it
is used by the /dev/random driver], and the crypto API plumbing to
expose it as a skcipher.

In order to support in-kernel users that need the ChaCha streamcipher
but have no need [or tolerance] for going through the abstractions of
the crypto API, let's expose the streamcipher bits via a library API
as well, in a way that permits the implementation to be superseded by
an architecture specific one if provided.

So move the streamcipher code into a separate module in lib/crypto,
and expose the init() and crypt() routines to users of the library.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

2 files changed, 6 insertions, 55 deletions

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 9def945e9549..ae4495ae003f 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -1412,6 +1412,7 @@ config CRYPTO_SALSA20
 
 config CRYPTO_CHACHA20
 	tristate "ChaCha stream cipher algorithms"
+	select CRYPTO_LIB_CHACHA_GENERIC
 	select CRYPTO_SKCIPHER
 	help
 	  The ChaCha20, XChaCha20, and XChaCha12 stream cipher algorithms.
diff --git a/crypto/chacha_generic.c b/crypto/chacha_generic.c
index 085d8d219987..ebae6d9d9b32 100644
--- a/crypto/chacha_generic.c
+++ b/crypto/chacha_generic.c
@@ -8,29 +8,10 @@
 
 #include <asm/unaligned.h>
 #include <crypto/algapi.h>
-#include <crypto/chacha.h>
+#include <crypto/internal/chacha.h>
 #include <crypto/internal/skcipher.h>
 #include <linux/module.h>
 
-static void chacha_docrypt(u32 *state, u8 *dst, const u8 *src,
-			   unsigned int bytes, int nrounds)
-{
-	/* aligned to potentially speed up crypto_xor() */
-	u8 stream[CHACHA_BLOCK_SIZE] __aligned(sizeof(long));
-
-	while (bytes >= CHACHA_BLOCK_SIZE) {
-		chacha_block(state, stream, nrounds);
-		crypto_xor_cpy(dst, src, stream, CHACHA_BLOCK_SIZE);
-		bytes -= CHACHA_BLOCK_SIZE;
-		dst += CHACHA_BLOCK_SIZE;
-		src += CHACHA_BLOCK_SIZE;
-	}
-	if (bytes) {
-		chacha_block(state, stream, nrounds);
-		crypto_xor_cpy(dst, src, stream, bytes);
-	}
-}
-
 static int chacha_stream_xor(struct skcipher_request *req,
 			     const struct chacha_ctx *ctx, const u8 *iv)
 {
@@ -48,8 +29,8 @@ static int chacha_stream_xor(struct skcipher_request *req,
 		if (nbytes < walk.total)
 			nbytes = round_down(nbytes, CHACHA_BLOCK_SIZE);
 
-		chacha_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
-			       nbytes, ctx->nrounds);
+		chacha_crypt_generic(state, walk.dst.virt.addr,
+				     walk.src.virt.addr, nbytes, ctx->nrounds);
 		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
 	}
 
@@ -58,41 +39,10 @@ static int chacha_stream_xor(struct skcipher_request *req,
 
 void crypto_chacha_init(u32 *state, const struct chacha_ctx *ctx, const u8 *iv)
 {
-	state[0]  = 0x61707865; /* "expa" */
-	state[1]  = 0x3320646e; /* "nd 3" */
-	state[2]  = 0x79622d32; /* "2-by" */
-	state[3]  = 0x6b206574; /* "te k" */
-	state[4]  = ctx->key[0];
-	state[5]  = ctx->key[1];
-	state[6]  = ctx->key[2];
-	state[7]  = ctx->key[3];
-	state[8]  = ctx->key[4];
-	state[9]  = ctx->key[5];
-	state[10] = ctx->key[6];
-	state[11] = ctx->key[7];
-	state[12] = get_unaligned_le32(iv +  0);
-	state[13] = get_unaligned_le32(iv +  4);
-	state[14] = get_unaligned_le32(iv +  8);
-	state[15] = get_unaligned_le32(iv + 12);
+	chacha_init_generic(state, ctx->key, iv);
 }
 EXPORT_SYMBOL_GPL(crypto_chacha_init);
 
-static int chacha_setkey(struct crypto_skcipher *tfm, const u8 *key,
-			 unsigned int keysize, int nrounds)
-{
-	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
-	int i;
-
-	if (keysize != CHACHA_KEY_SIZE)
-		return -EINVAL;
-
-	for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
-		ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32));
-
-	ctx->nrounds = nrounds;
-	return 0;
-}
-
 int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
 			   unsigned int keysize)
 {
@@ -126,7 +76,7 @@ int crypto_xchacha_crypt(struct skcipher_request *req)
 
 	/* Compute the subkey given the original key and first 128 nonce bits */
 	crypto_chacha_init(state, ctx, req->iv);
-	hchacha_block(state, subctx.key, ctx->nrounds);
+	hchacha_block_generic(state, subctx.key, ctx->nrounds);
 	subctx.nrounds = ctx->nrounds;
 
 	/* Build the real IV */