crypto: chacha20-generic - refactor to allow varying number of rounds

In preparation for adding XChaCha12 support, rename/refactor
chacha20-generic to support different numbers of rounds.  The
justification for needing XChaCha12 support is explained in more detail
in the patch "crypto: chacha - add XChaCha12 support".

The only difference between ChaCha{8,12,20} are the number of rounds
itself; all other parts of the algorithm are the same.  Therefore,
remove the "20" from all definitions, structures, functions, files, etc.
that will be shared by all ChaCha versions.

Also make ->setkey() store the round count in the chacha_ctx (previously
chacha20_ctx).  The generic code then passes the round count through to
chacha_block().  There will be a ->setkey() function for each explicitly
allowed round count; the encrypt/decrypt functions will be the same.  I
decided not to do it the opposite way (same ->setkey() function for all
round counts, with different encrypt/decrypt functions) because that
would have required more boilerplate code in architecture-specific
implementations of ChaCha and XChaCha.

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

3 files changed, 65 insertions, 57 deletions

diff --git a/crypto/Makefile b/crypto/Makefile
index abbd86fdbad2..102e8525814f 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -117,7 +117,7 @@ obj-$(CONFIG_CRYPTO_KHAZAD) += khazad.o
 obj-$(CONFIG_CRYPTO_ANUBIS) += anubis.o
 obj-$(CONFIG_CRYPTO_SEED) += seed.o
 obj-$(CONFIG_CRYPTO_SALSA20) += salsa20_generic.o
-obj-$(CONFIG_CRYPTO_CHACHA20) += chacha20_generic.o
+obj-$(CONFIG_CRYPTO_CHACHA20) += chacha_generic.o
 obj-$(CONFIG_CRYPTO_POLY1305) += poly1305_generic.o
 obj-$(CONFIG_CRYPTO_DEFLATE) += deflate.o
 obj-$(CONFIG_CRYPTO_MICHAEL_MIC) += michael_mic.o
diff --git a/crypto/chacha20poly1305.c b/crypto/chacha20poly1305.c
index f9dd5453046a..fef11446ab1b 100644
--- a/crypto/chacha20poly1305.c
+++ b/crypto/chacha20poly1305.c
@@ -13,7 +13,7 @@
 #include <crypto/internal/hash.h>
 #include <crypto/internal/skcipher.h>
 #include <crypto/scatterwalk.h>
-#include <crypto/chacha20.h>
+#include <crypto/chacha.h>
 #include <crypto/poly1305.h>
 #include <linux/err.h>
 #include <linux/init.h>
@@ -49,7 +49,7 @@ struct poly_req {
 };
 
 struct chacha_req {
-	u8 iv[CHACHA20_IV_SIZE];
+	u8 iv[CHACHA_IV_SIZE];
 	struct scatterlist src[1];
 	struct skcipher_request req; /* must be last member */
 };
@@ -89,7 +89,7 @@ static void chacha_iv(u8 *iv, struct aead_request *req, u32 icb)
 	memcpy(iv, &leicb, sizeof(leicb));
 	memcpy(iv + sizeof(leicb), ctx->salt, ctx->saltlen);
 	memcpy(iv + sizeof(leicb) + ctx->saltlen, req->iv,
-	       CHACHA20_IV_SIZE - sizeof(leicb) - ctx->saltlen);
+	       CHACHA_IV_SIZE - sizeof(leicb) - ctx->saltlen);
 }
 
 static int poly_verify_tag(struct aead_request *req)
@@ -492,7 +492,7 @@ static int chachapoly_setkey(struct crypto_aead *aead, const u8 *key,
 	struct chachapoly_ctx *ctx = crypto_aead_ctx(aead);
 	int err;
 
-	if (keylen != ctx->saltlen + CHACHA20_KEY_SIZE)
+	if (keylen != ctx->saltlen + CHACHA_KEY_SIZE)
 		return -EINVAL;
 
 	keylen -= ctx->saltlen;
@@ -637,7 +637,7 @@ static int chachapoly_create(struct crypto_template *tmpl, struct rtattr **tb,
 
 	err = -EINVAL;
 	/* Need 16-byte IV size, including Initial Block Counter value */
-	if (crypto_skcipher_alg_ivsize(chacha) != CHACHA20_IV_SIZE)
+	if (crypto_skcipher_alg_ivsize(chacha) != CHACHA_IV_SIZE)
 		goto out_drop_chacha;
 	/* Not a stream cipher? */
 	if (chacha->base.cra_blocksize != 1)
diff --git a/crypto/chacha20_generic.c b/crypto/chacha_generic.c
index 4305b1b62b16..438f15a14054 100644
--- a/crypto/chacha20_generic.c
+++ b/crypto/chacha_generic.c
@@ -12,33 +12,33 @@
 
 #include <asm/unaligned.h>
 #include <crypto/algapi.h>
-#include <crypto/chacha20.h>
+#include <crypto/chacha.h>
 #include <crypto/internal/skcipher.h>
 #include <linux/module.h>
 
-static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
-			     unsigned int bytes)
+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[CHACHA20_BLOCK_SIZE] __aligned(sizeof(long));
+	u8 stream[CHACHA_BLOCK_SIZE] __aligned(sizeof(long));
 
 	if (dst != src)
 		memcpy(dst, src, bytes);
 
-	while (bytes >= CHACHA20_BLOCK_SIZE) {
-		chacha20_block(state, stream);
-		crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE);
-		bytes -= CHACHA20_BLOCK_SIZE;
-		dst += CHACHA20_BLOCK_SIZE;
+	while (bytes >= CHACHA_BLOCK_SIZE) {
+		chacha_block(state, stream, nrounds);
+		crypto_xor(dst, stream, CHACHA_BLOCK_SIZE);
+		bytes -= CHACHA_BLOCK_SIZE;
+		dst += CHACHA_BLOCK_SIZE;
 	}
 	if (bytes) {
-		chacha20_block(state, stream);
+		chacha_block(state, stream, nrounds);
 		crypto_xor(dst, stream, bytes);
 	}
 }
 
-static int chacha20_stream_xor(struct skcipher_request *req,
-			       struct chacha20_ctx *ctx, u8 *iv)
+static int chacha_stream_xor(struct skcipher_request *req,
+			     struct chacha_ctx *ctx, u8 *iv)
 {
 	struct skcipher_walk walk;
 	u32 state[16];
@@ -46,7 +46,7 @@ static int chacha20_stream_xor(struct skcipher_request *req,
 
 	err = skcipher_walk_virt(&walk, req, false);
 
-	crypto_chacha20_init(state, ctx, iv);
+	crypto_chacha_init(state, ctx, iv);
 
 	while (walk.nbytes > 0) {
 		unsigned int nbytes = walk.nbytes;
@@ -54,15 +54,15 @@ static int chacha20_stream_xor(struct skcipher_request *req,
 		if (nbytes < walk.total)
 			nbytes = round_down(nbytes, walk.stride);
 
-		chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
-				 nbytes);
+		chacha_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
+			       nbytes, ctx->nrounds);
 		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
 	}
 
 	return err;
 }
 
-void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
+void crypto_chacha_init(u32 *state, struct chacha_ctx *ctx, u8 *iv)
 {
 	state[0]  = 0x61707865; /* "expa" */
 	state[1]  = 0x3320646e; /* "nd 3" */
@@ -81,53 +81,61 @@ void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
 	state[14] = get_unaligned_le32(iv +  8);
 	state[15] = get_unaligned_le32(iv + 12);
 }
-EXPORT_SYMBOL_GPL(crypto_chacha20_init);
+EXPORT_SYMBOL_GPL(crypto_chacha_init);
 
-int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
-			   unsigned int keysize)
+static int chacha_setkey(struct crypto_skcipher *tfm, const u8 *key,
+			 unsigned int keysize, int nrounds)
 {
-	struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
+	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
 	int i;
 
-	if (keysize != CHACHA20_KEY_SIZE)
+	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)
+{
+	return chacha_setkey(tfm, key, keysize, 20);
+}
 EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
 
-int crypto_chacha20_crypt(struct skcipher_request *req)
+int crypto_chacha_crypt(struct skcipher_request *req)
 {
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
-	struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
+	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
 
-	return chacha20_stream_xor(req, ctx, req->iv);
+	return chacha_stream_xor(req, ctx, req->iv);
 }
-EXPORT_SYMBOL_GPL(crypto_chacha20_crypt);
+EXPORT_SYMBOL_GPL(crypto_chacha_crypt);
 
-int crypto_xchacha20_crypt(struct skcipher_request *req)
+int crypto_xchacha_crypt(struct skcipher_request *req)
 {
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
-	struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
-	struct chacha20_ctx subctx;
+	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
+	struct chacha_ctx subctx;
 	u32 state[16];
 	u8 real_iv[16];
 
 	/* Compute the subkey given the original key and first 128 nonce bits */
-	crypto_chacha20_init(state, ctx, req->iv);
-	hchacha20_block(state, subctx.key);
+	crypto_chacha_init(state, ctx, req->iv);
+	hchacha_block(state, subctx.key, ctx->nrounds);
+	subctx.nrounds = ctx->nrounds;
 
 	/* Build the real IV */
 	memcpy(&real_iv[0], req->iv + 24, 8); /* stream position */
 	memcpy(&real_iv[8], req->iv + 16, 8); /* remaining 64 nonce bits */
 
 	/* Generate the stream and XOR it with the data */
-	return chacha20_stream_xor(req, &subctx, real_iv);
+	return chacha_stream_xor(req, &subctx, real_iv);
 }
-EXPORT_SYMBOL_GPL(crypto_xchacha20_crypt);
+EXPORT_SYMBOL_GPL(crypto_xchacha_crypt);
 
 static struct skcipher_alg algs[] = {
 	{
@@ -135,50 +143,50 @@ static struct skcipher_alg algs[] = {
 		.base.cra_driver_name	= "chacha20-generic",
 		.base.cra_priority	= 100,
 		.base.cra_blocksize	= 1,
-		.base.cra_ctxsize	= sizeof(struct chacha20_ctx),
+		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
 		.base.cra_module	= THIS_MODULE,
 
-		.min_keysize		= CHACHA20_KEY_SIZE,
-		.max_keysize		= CHACHA20_KEY_SIZE,
-		.ivsize			= CHACHA20_IV_SIZE,
-		.chunksize		= CHACHA20_BLOCK_SIZE,
+		.min_keysize		= CHACHA_KEY_SIZE,
+		.max_keysize		= CHACHA_KEY_SIZE,
+		.ivsize			= CHACHA_IV_SIZE,
+		.chunksize		= CHACHA_BLOCK_SIZE,
 		.setkey			= crypto_chacha20_setkey,
-		.encrypt		= crypto_chacha20_crypt,
-		.decrypt		= crypto_chacha20_crypt,
+		.encrypt		= crypto_chacha_crypt,
+		.decrypt		= crypto_chacha_crypt,
 	}, {
 		.base.cra_name		= "xchacha20",
 		.base.cra_driver_name	= "xchacha20-generic",
 		.base.cra_priority	= 100,
 		.base.cra_blocksize	= 1,
-		.base.cra_ctxsize	= sizeof(struct chacha20_ctx),
+		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
 		.base.cra_module	= THIS_MODULE,
 
-		.min_keysize		= CHACHA20_KEY_SIZE,
-		.max_keysize		= CHACHA20_KEY_SIZE,
-		.ivsize			= XCHACHA20_IV_SIZE,
-		.chunksize		= CHACHA20_BLOCK_SIZE,
+		.min_keysize		= CHACHA_KEY_SIZE,
+		.max_keysize		= CHACHA_KEY_SIZE,
+		.ivsize			= XCHACHA_IV_SIZE,
+		.chunksize		= CHACHA_BLOCK_SIZE,
 		.setkey			= crypto_chacha20_setkey,
-		.encrypt		= crypto_xchacha20_crypt,
-		.decrypt		= crypto_xchacha20_crypt,
+		.encrypt		= crypto_xchacha_crypt,
+		.decrypt		= crypto_xchacha_crypt,
 	}
 };
 
-static int __init chacha20_generic_mod_init(void)
+static int __init chacha_generic_mod_init(void)
 {
 	return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
 }
 
-static void __exit chacha20_generic_mod_fini(void)
+static void __exit chacha_generic_mod_fini(void)
 {
 	crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
 }
 
-module_init(chacha20_generic_mod_init);
-module_exit(chacha20_generic_mod_fini);
+module_init(chacha_generic_mod_init);
+module_exit(chacha_generic_mod_fini);
 
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
-MODULE_DESCRIPTION("ChaCha20 and XChaCha20 stream ciphers (generic)");
+MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (generic)");
 MODULE_ALIAS_CRYPTO("chacha20");
 MODULE_ALIAS_CRYPTO("chacha20-generic");
 MODULE_ALIAS_CRYPTO("xchacha20");