diff options
Diffstat (limited to 'crypto/chacha_generic.c')
| -rw-r--r-- | crypto/chacha_generic.c | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/crypto/chacha_generic.c b/crypto/chacha_generic.c new file mode 100644 index 000000000000..438f15a14054 --- /dev/null +++ b/crypto/chacha_generic.c @@ -0,0 +1,193 @@ +/* + * ChaCha20 (RFC7539) and XChaCha20 stream cipher algorithms + * + * Copyright (C) 2015 Martin Willi + * Copyright (C) 2018 Google LLC + * + * 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 <asm/unaligned.h> +#include <crypto/algapi.h> +#include <crypto/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)); + + if (dst != src) + memcpy(dst, src, bytes); + + 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) { + chacha_block(state, stream, nrounds); + crypto_xor(dst, stream, bytes); + } +} + +static int chacha_stream_xor(struct skcipher_request *req, + struct chacha_ctx *ctx, u8 *iv) +{ + struct skcipher_walk walk; + u32 state[16]; + int err; + + err = skcipher_walk_virt(&walk, req, false); + + crypto_chacha_init(state, ctx, iv); + + while (walk.nbytes > 0) { + unsigned int nbytes = walk.nbytes; + + if (nbytes < walk.total) + nbytes = round_down(nbytes, walk.stride); + + 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_chacha_init(u32 *state, struct chacha_ctx *ctx, 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); +} +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) +{ + return chacha_setkey(tfm, key, keysize, 20); +} +EXPORT_SYMBOL_GPL(crypto_chacha20_setkey); + +int crypto_chacha_crypt(struct skcipher_request *req) +{ + struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); + struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm); + + return chacha_stream_xor(req, ctx, req->iv); +} +EXPORT_SYMBOL_GPL(crypto_chacha_crypt); + +int crypto_xchacha_crypt(struct skcipher_request *req) +{ + struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); + 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_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 chacha_stream_xor(req, &subctx, real_iv); +} +EXPORT_SYMBOL_GPL(crypto_xchacha_crypt); + +static struct skcipher_alg algs[] = { + { + .base.cra_name = "chacha20", + .base.cra_driver_name = "chacha20-generic", + .base.cra_priority = 100, + .base.cra_blocksize = 1, + .base.cra_ctxsize = sizeof(struct chacha_ctx), + .base.cra_module = THIS_MODULE, + + .min_keysize = CHACHA_KEY_SIZE, + .max_keysize = CHACHA_KEY_SIZE, + .ivsize = CHACHA_IV_SIZE, + .chunksize = CHACHA_BLOCK_SIZE, + .setkey = crypto_chacha20_setkey, + .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 chacha_ctx), + .base.cra_module = THIS_MODULE, + + .min_keysize = CHACHA_KEY_SIZE, + .max_keysize = CHACHA_KEY_SIZE, + .ivsize = XCHACHA_IV_SIZE, + .chunksize = CHACHA_BLOCK_SIZE, + .setkey = crypto_chacha20_setkey, + .encrypt = crypto_xchacha_crypt, + .decrypt = crypto_xchacha_crypt, + } +}; + +static int __init chacha_generic_mod_init(void) +{ + return crypto_register_skciphers(algs, ARRAY_SIZE(algs)); +} + +static void __exit chacha_generic_mod_fini(void) +{ + crypto_unregister_skciphers(algs, ARRAY_SIZE(algs)); +} + +module_init(chacha_generic_mod_init); +module_exit(chacha_generic_mod_fini); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Martin Willi <martin@strongswan.org>"); +MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (generic)"); +MODULE_ALIAS_CRYPTO("chacha20"); +MODULE_ALIAS_CRYPTO("chacha20-generic"); +MODULE_ALIAS_CRYPTO("xchacha20"); +MODULE_ALIAS_CRYPTO("xchacha20-generic"); |