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as well, in a way that permits the implementation to be superseded by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, 113 insertions, 17 deletions

diff --git a/include/crypto/chacha.h b/include/crypto/chacha.h
index d1e723c6a37d..5c662f8fecac 100644
--- a/include/crypto/chacha.h
+++ b/include/crypto/chacha.h
@@ -15,9 +15,8 @@
 #ifndef _CRYPTO_CHACHA_H
 #define _CRYPTO_CHACHA_H
 
-#include <crypto/skcipher.h>
+#include <asm/unaligned.h>
 #include <linux/types.h>
-#include <linux/crypto.h>
 
 /* 32-bit stream position, then 96-bit nonce (RFC7539 convention) */
 #define CHACHA_IV_SIZE		16
@@ -29,26 +28,70 @@
 /* 192-bit nonce, then 64-bit stream position */
 #define XCHACHA_IV_SIZE		32
 
-struct chacha_ctx {
-	u32 key[8];
-	int nrounds;
-};
-
-void chacha_block(u32 *state, u8 *stream, int nrounds);
+void chacha_block_generic(u32 *state, u8 *stream, int nrounds);
 static inline void chacha20_block(u32 *state, u8 *stream)
 {
-	chacha_block(state, stream, 20);
+	chacha_block_generic(state, stream, 20);
 }
-void hchacha_block(const u32 *in, u32 *out, int nrounds);
 
-void crypto_chacha_init(u32 *state, const struct chacha_ctx *ctx, const u8 *iv);
+void hchacha_block_arch(const u32 *state, u32 *out, int nrounds);
+void hchacha_block_generic(const u32 *state, u32 *out, int nrounds);
+
+static inline void hchacha_block(const u32 *state, u32 *out, int nrounds)
+{
+	if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
+		hchacha_block_arch(state, out, nrounds);
+	else
+		hchacha_block_generic(state, out, nrounds);
+}
 
-int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
-			   unsigned int keysize);
-int crypto_chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key,
-			   unsigned int keysize);
+void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv);
+static inline void chacha_init_generic(u32 *state, const u32 *key, const u8 *iv)
+{
+	state[0]  = 0x61707865; /* "expa" */
+	state[1]  = 0x3320646e; /* "nd 3" */
+	state[2]  = 0x79622d32; /* "2-by" */
+	state[3]  = 0x6b206574; /* "te k" */
+	state[4]  = key[0];
+	state[5]  = key[1];
+	state[6]  = key[2];
+	state[7]  = key[3];
+	state[8]  = key[4];
+	state[9]  = key[5];
+	state[10] = key[6];
+	state[11] = 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);
+}
 
-int crypto_chacha_crypt(struct skcipher_request *req);
-int crypto_xchacha_crypt(struct skcipher_request *req);
+static inline void chacha_init(u32 *state, const u32 *key, const u8 *iv)
+{
+	if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
+		chacha_init_arch(state, key, iv);
+	else
+		chacha_init_generic(state, key, iv);
+}
+
+void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src,
+		       unsigned int bytes, int nrounds);
+void chacha_crypt_generic(u32 *state, u8 *dst, const u8 *src,
+			  unsigned int bytes, int nrounds);
+
+static inline void chacha_crypt(u32 *state, u8 *dst, const u8 *src,
+				unsigned int bytes, int nrounds)
+{
+	if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
+		chacha_crypt_arch(state, dst, src, bytes, nrounds);
+	else
+		chacha_crypt_generic(state, dst, src, bytes, nrounds);
+}
+
+static inline void chacha20_crypt(u32 *state, u8 *dst, const u8 *src,
+				  unsigned int bytes)
+{
+	chacha_crypt(state, dst, src, bytes, 20);
+}
 
 #endif /* _CRYPTO_CHACHA_H */
diff --git a/include/crypto/internal/chacha.h b/include/crypto/internal/chacha.h
new file mode 100644
index 000000000000..c0e40b245431
--- /dev/null
+++ b/include/crypto/internal/chacha.h
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _CRYPTO_INTERNAL_CHACHA_H
+#define _CRYPTO_INTERNAL_CHACHA_H
+
+#include <crypto/chacha.h>
+#include <crypto/internal/skcipher.h>
+#include <linux/crypto.h>
+
+struct chacha_ctx {
+	u32 key[8];
+	int nrounds;
+};
+
+void crypto_chacha_init(u32 *state, const struct chacha_ctx *ctx, const u8 *iv);
+
+static inline 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;
+}
+
+static inline int chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
+				  unsigned int keysize)
+{
+	return chacha_setkey(tfm, key, keysize, 20);
+}
+
+static int inline chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key,
+				  unsigned int keysize)
+{
+	return chacha_setkey(tfm, key, keysize, 12);
+}
+
+int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
+			   unsigned int keysize);
+int crypto_chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key,
+			   unsigned int keysize);
+
+int crypto_chacha_crypt(struct skcipher_request *req);
+int crypto_xchacha_crypt(struct skcipher_request *req);
+
+#endif /* _CRYPTO_CHACHA_H */