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authorMartin Willi <martin@strongswan.org>2015-06-01 13:43:56 +0200
committerHerbert Xu <herbert@gondor.apana.org.au>2015-06-04 15:04:49 +0800
commitc08d0e647305c3f8f640010a56c9e4bafb9488d3 (patch)
treef6d862fda8608a41677ec721f5dc280a1899a320 /crypto/chacha20_generic.c
parentfb43f69401fef8ed2f72d7ea4a25910a0f2138bc (diff)
downloadlinux-stericsson-c08d0e647305c3f8f640010a56c9e4bafb9488d3.tar.gz
crypto: chacha20 - Add a generic ChaCha20 stream cipher implementation
ChaCha20 is a high speed 256-bit key size stream cipher algorithm designed by Daniel J. Bernstein. It is further specified in RFC7539 for use in IETF protocols as a building block for the ChaCha20-Poly1305 AEAD. This is a portable C implementation without any architecture specific optimizations. It uses a 16-byte IV, which includes the 12-byte ChaCha20 nonce prepended by the initial block counter. Some algorithms require an explicit counter value, for example the mentioned AEAD construction. Signed-off-by: Martin Willi <martin@strongswan.org> Acked-by: Steffen Klassert <steffen.klassert@secunet.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'crypto/chacha20_generic.c')
-rw-r--r--crypto/chacha20_generic.c216
1 files changed, 216 insertions, 0 deletions
diff --git a/crypto/chacha20_generic.c b/crypto/chacha20_generic.c
new file mode 100644
index 000000000000..fa42e708aa96
--- /dev/null
+++ b/crypto/chacha20_generic.c
@@ -0,0 +1,216 @@
+/*
+ * ChaCha20 256-bit cipher algorithm, RFC7539
+ *
+ * Copyright (C) 2015 Martin Willi
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <crypto/algapi.h>
+#include <linux/crypto.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#define CHACHA20_NONCE_SIZE 16
+#define CHACHA20_KEY_SIZE 32
+#define CHACHA20_BLOCK_SIZE 64
+
+struct chacha20_ctx {
+ u32 key[8];
+};
+
+static inline u32 rotl32(u32 v, u8 n)
+{
+ return (v << n) | (v >> (sizeof(v) * 8 - n));
+}
+
+static inline u32 le32_to_cpuvp(const void *p)
+{
+ return le32_to_cpup(p);
+}
+
+static void chacha20_block(u32 *state, void *stream)
+{
+ u32 x[16], *out = stream;
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(x); i++)
+ x[i] = state[i];
+
+ for (i = 0; i < 20; i += 2) {
+ x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 16);
+ x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 16);
+ x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 16);
+ x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 16);
+
+ x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 12);
+ x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 12);
+ x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 12);
+ x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 12);
+
+ x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 8);
+ x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 8);
+ x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 8);
+ x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 8);
+
+ x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 7);
+ x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 7);
+ x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 7);
+ x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 7);
+
+ x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 16);
+ x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 16);
+ x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 16);
+ x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 16);
+
+ x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 12);
+ x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 12);
+ x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 12);
+ x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 12);
+
+ x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 8);
+ x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 8);
+ x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 8);
+ x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 8);
+
+ x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 7);
+ x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 7);
+ x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 7);
+ x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 7);
+ }
+
+ for (i = 0; i < ARRAY_SIZE(x); i++)
+ out[i] = cpu_to_le32(x[i] + state[i]);
+
+ state[12]++;
+}
+
+static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
+ unsigned int bytes)
+{
+ u8 stream[CHACHA20_BLOCK_SIZE];
+
+ 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;
+ }
+ if (bytes) {
+ chacha20_block(state, stream);
+ crypto_xor(dst, stream, bytes);
+ }
+}
+
+static void chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
+{
+ static const char constant[16] = "expand 32-byte k";
+
+ state[0] = le32_to_cpuvp(constant + 0);
+ state[1] = le32_to_cpuvp(constant + 4);
+ state[2] = le32_to_cpuvp(constant + 8);
+ state[3] = le32_to_cpuvp(constant + 12);
+ 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] = le32_to_cpuvp(iv + 0);
+ state[13] = le32_to_cpuvp(iv + 4);
+ state[14] = le32_to_cpuvp(iv + 8);
+ state[15] = le32_to_cpuvp(iv + 12);
+}
+
+static int chacha20_setkey(struct crypto_tfm *tfm, const u8 *key,
+ unsigned int keysize)
+{
+ struct chacha20_ctx *ctx = crypto_tfm_ctx(tfm);
+ int i;
+
+ if (keysize != CHACHA20_KEY_SIZE)
+ return -EINVAL;
+
+ for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
+ ctx->key[i] = le32_to_cpuvp(key + i * sizeof(u32));
+
+ return 0;
+}
+
+static int chacha20_crypt(struct blkcipher_desc *desc, struct scatterlist *dst,
+ struct scatterlist *src, unsigned int nbytes)
+{
+ struct blkcipher_walk walk;
+ u32 state[16];
+ int err;
+
+ blkcipher_walk_init(&walk, dst, src, nbytes);
+ err = blkcipher_walk_virt_block(desc, &walk, CHACHA20_BLOCK_SIZE);
+
+ chacha20_init(state, crypto_blkcipher_ctx(desc->tfm), walk.iv);
+
+ while (walk.nbytes >= CHACHA20_BLOCK_SIZE) {
+ chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
+ rounddown(walk.nbytes, CHACHA20_BLOCK_SIZE));
+ err = blkcipher_walk_done(desc, &walk,
+ walk.nbytes % CHACHA20_BLOCK_SIZE);
+ }
+
+ if (walk.nbytes) {
+ chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
+ walk.nbytes);
+ err = blkcipher_walk_done(desc, &walk, 0);
+ }
+
+ return err;
+}
+
+static struct crypto_alg alg = {
+ .cra_name = "chacha20",
+ .cra_driver_name = "chacha20-generic",
+ .cra_priority = 100,
+ .cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER,
+ .cra_blocksize = 1,
+ .cra_type = &crypto_blkcipher_type,
+ .cra_ctxsize = sizeof(struct chacha20_ctx),
+ .cra_alignmask = sizeof(u32) - 1,
+ .cra_module = THIS_MODULE,
+ .cra_u = {
+ .blkcipher = {
+ .min_keysize = CHACHA20_KEY_SIZE,
+ .max_keysize = CHACHA20_KEY_SIZE,
+ .ivsize = CHACHA20_NONCE_SIZE,
+ .geniv = "seqiv",
+ .setkey = chacha20_setkey,
+ .encrypt = chacha20_crypt,
+ .decrypt = chacha20_crypt,
+ },
+ },
+};
+
+static int __init chacha20_generic_mod_init(void)
+{
+ return crypto_register_alg(&alg);
+}
+
+static void __exit chacha20_generic_mod_fini(void)
+{
+ crypto_unregister_alg(&alg);
+}
+
+module_init(chacha20_generic_mod_init);
+module_exit(chacha20_generic_mod_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
+MODULE_DESCRIPTION("chacha20 cipher algorithm");
+MODULE_ALIAS_CRYPTO("chacha20");
+MODULE_ALIAS_CRYPTO("chacha20-generic");