// SPDX-License-Identifier: GPL-2.0-or-later /* * ChaCha and XChaCha stream ciphers, including ChaCha20 (RFC7539) * * Copyright (C) 2015 Martin Willi * Copyright (C) 2018 Google LLC */ #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)); 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) { 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, CHACHA_BLOCK_SIZE); 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, 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); } 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_chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key, unsigned int keysize) { return chacha_setkey(tfm, key, keysize, 12); } EXPORT_SYMBOL_GPL(crypto_chacha12_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, }, { .base.cra_name = "xchacha12", .base.cra_driver_name = "xchacha12-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_chacha12_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)); } subsys_initcall(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"); MODULE_ALIAS_CRYPTO("xchacha12"); MODULE_ALIAS_CRYPTO("xchacha12-generic");