11ca1b917SEric Biggers /* 21ca1b917SEric Biggers * ChaCha20 (RFC7539) and XChaCha20 stream cipher algorithms 31ca1b917SEric Biggers * 41ca1b917SEric Biggers * Copyright (C) 2015 Martin Willi 51ca1b917SEric Biggers * Copyright (C) 2018 Google LLC 61ca1b917SEric Biggers * 71ca1b917SEric Biggers * This program is free software; you can redistribute it and/or modify 81ca1b917SEric Biggers * it under the terms of the GNU General Public License as published by 91ca1b917SEric Biggers * the Free Software Foundation; either version 2 of the License, or 101ca1b917SEric Biggers * (at your option) any later version. 111ca1b917SEric Biggers */ 121ca1b917SEric Biggers 131ca1b917SEric Biggers #include <asm/unaligned.h> 141ca1b917SEric Biggers #include <crypto/algapi.h> 151ca1b917SEric Biggers #include <crypto/chacha.h> 161ca1b917SEric Biggers #include <crypto/internal/skcipher.h> 171ca1b917SEric Biggers #include <linux/module.h> 181ca1b917SEric Biggers 191ca1b917SEric Biggers static void chacha_docrypt(u32 *state, u8 *dst, const u8 *src, 201ca1b917SEric Biggers unsigned int bytes, int nrounds) 211ca1b917SEric Biggers { 221ca1b917SEric Biggers /* aligned to potentially speed up crypto_xor() */ 231ca1b917SEric Biggers u8 stream[CHACHA_BLOCK_SIZE] __aligned(sizeof(long)); 241ca1b917SEric Biggers 251ca1b917SEric Biggers if (dst != src) 261ca1b917SEric Biggers memcpy(dst, src, bytes); 271ca1b917SEric Biggers 281ca1b917SEric Biggers while (bytes >= CHACHA_BLOCK_SIZE) { 291ca1b917SEric Biggers chacha_block(state, stream, nrounds); 301ca1b917SEric Biggers crypto_xor(dst, stream, CHACHA_BLOCK_SIZE); 311ca1b917SEric Biggers bytes -= CHACHA_BLOCK_SIZE; 321ca1b917SEric Biggers dst += CHACHA_BLOCK_SIZE; 331ca1b917SEric Biggers } 341ca1b917SEric Biggers if (bytes) { 351ca1b917SEric Biggers chacha_block(state, stream, nrounds); 361ca1b917SEric Biggers crypto_xor(dst, stream, bytes); 371ca1b917SEric Biggers } 381ca1b917SEric Biggers } 391ca1b917SEric Biggers 401ca1b917SEric Biggers static int chacha_stream_xor(struct skcipher_request *req, 411ca1b917SEric Biggers struct chacha_ctx *ctx, u8 *iv) 421ca1b917SEric Biggers { 431ca1b917SEric Biggers struct skcipher_walk walk; 441ca1b917SEric Biggers u32 state[16]; 451ca1b917SEric Biggers int err; 461ca1b917SEric Biggers 471ca1b917SEric Biggers err = skcipher_walk_virt(&walk, req, false); 481ca1b917SEric Biggers 491ca1b917SEric Biggers crypto_chacha_init(state, ctx, iv); 501ca1b917SEric Biggers 511ca1b917SEric Biggers while (walk.nbytes > 0) { 521ca1b917SEric Biggers unsigned int nbytes = walk.nbytes; 531ca1b917SEric Biggers 541ca1b917SEric Biggers if (nbytes < walk.total) 551ca1b917SEric Biggers nbytes = round_down(nbytes, walk.stride); 561ca1b917SEric Biggers 571ca1b917SEric Biggers chacha_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr, 581ca1b917SEric Biggers nbytes, ctx->nrounds); 591ca1b917SEric Biggers err = skcipher_walk_done(&walk, walk.nbytes - nbytes); 601ca1b917SEric Biggers } 611ca1b917SEric Biggers 621ca1b917SEric Biggers return err; 631ca1b917SEric Biggers } 641ca1b917SEric Biggers 651ca1b917SEric Biggers void crypto_chacha_init(u32 *state, struct chacha_ctx *ctx, u8 *iv) 661ca1b917SEric Biggers { 671ca1b917SEric Biggers state[0] = 0x61707865; /* "expa" */ 681ca1b917SEric Biggers state[1] = 0x3320646e; /* "nd 3" */ 691ca1b917SEric Biggers state[2] = 0x79622d32; /* "2-by" */ 701ca1b917SEric Biggers state[3] = 0x6b206574; /* "te k" */ 711ca1b917SEric Biggers state[4] = ctx->key[0]; 721ca1b917SEric Biggers state[5] = ctx->key[1]; 731ca1b917SEric Biggers state[6] = ctx->key[2]; 741ca1b917SEric Biggers state[7] = ctx->key[3]; 751ca1b917SEric Biggers state[8] = ctx->key[4]; 761ca1b917SEric Biggers state[9] = ctx->key[5]; 771ca1b917SEric Biggers state[10] = ctx->key[6]; 781ca1b917SEric Biggers state[11] = ctx->key[7]; 791ca1b917SEric Biggers state[12] = get_unaligned_le32(iv + 0); 801ca1b917SEric Biggers state[13] = get_unaligned_le32(iv + 4); 811ca1b917SEric Biggers state[14] = get_unaligned_le32(iv + 8); 821ca1b917SEric Biggers state[15] = get_unaligned_le32(iv + 12); 831ca1b917SEric Biggers } 841ca1b917SEric Biggers EXPORT_SYMBOL_GPL(crypto_chacha_init); 851ca1b917SEric Biggers 861ca1b917SEric Biggers static int chacha_setkey(struct crypto_skcipher *tfm, const u8 *key, 871ca1b917SEric Biggers unsigned int keysize, int nrounds) 881ca1b917SEric Biggers { 891ca1b917SEric Biggers struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm); 901ca1b917SEric Biggers int i; 911ca1b917SEric Biggers 921ca1b917SEric Biggers if (keysize != CHACHA_KEY_SIZE) 931ca1b917SEric Biggers return -EINVAL; 941ca1b917SEric Biggers 951ca1b917SEric Biggers for (i = 0; i < ARRAY_SIZE(ctx->key); i++) 961ca1b917SEric Biggers ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32)); 971ca1b917SEric Biggers 981ca1b917SEric Biggers ctx->nrounds = nrounds; 991ca1b917SEric Biggers return 0; 1001ca1b917SEric Biggers } 1011ca1b917SEric Biggers 1021ca1b917SEric Biggers int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key, 1031ca1b917SEric Biggers unsigned int keysize) 1041ca1b917SEric Biggers { 1051ca1b917SEric Biggers return chacha_setkey(tfm, key, keysize, 20); 1061ca1b917SEric Biggers } 1071ca1b917SEric Biggers EXPORT_SYMBOL_GPL(crypto_chacha20_setkey); 1081ca1b917SEric Biggers 1091ca1b917SEric Biggers int crypto_chacha_crypt(struct skcipher_request *req) 1101ca1b917SEric Biggers { 1111ca1b917SEric Biggers struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); 1121ca1b917SEric Biggers struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm); 1131ca1b917SEric Biggers 1141ca1b917SEric Biggers return chacha_stream_xor(req, ctx, req->iv); 1151ca1b917SEric Biggers } 1161ca1b917SEric Biggers EXPORT_SYMBOL_GPL(crypto_chacha_crypt); 1171ca1b917SEric Biggers 1181ca1b917SEric Biggers int crypto_xchacha_crypt(struct skcipher_request *req) 1191ca1b917SEric Biggers { 1201ca1b917SEric Biggers struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); 1211ca1b917SEric Biggers struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm); 1221ca1b917SEric Biggers struct chacha_ctx subctx; 1231ca1b917SEric Biggers u32 state[16]; 1241ca1b917SEric Biggers u8 real_iv[16]; 1251ca1b917SEric Biggers 1261ca1b917SEric Biggers /* Compute the subkey given the original key and first 128 nonce bits */ 1271ca1b917SEric Biggers crypto_chacha_init(state, ctx, req->iv); 1281ca1b917SEric Biggers hchacha_block(state, subctx.key, ctx->nrounds); 1291ca1b917SEric Biggers subctx.nrounds = ctx->nrounds; 1301ca1b917SEric Biggers 1311ca1b917SEric Biggers /* Build the real IV */ 1321ca1b917SEric Biggers memcpy(&real_iv[0], req->iv + 24, 8); /* stream position */ 1331ca1b917SEric Biggers memcpy(&real_iv[8], req->iv + 16, 8); /* remaining 64 nonce bits */ 1341ca1b917SEric Biggers 1351ca1b917SEric Biggers /* Generate the stream and XOR it with the data */ 1361ca1b917SEric Biggers return chacha_stream_xor(req, &subctx, real_iv); 1371ca1b917SEric Biggers } 1381ca1b917SEric Biggers EXPORT_SYMBOL_GPL(crypto_xchacha_crypt); 1391ca1b917SEric Biggers 1401ca1b917SEric Biggers static struct skcipher_alg algs[] = { 1411ca1b917SEric Biggers { 1421ca1b917SEric Biggers .base.cra_name = "chacha20", 1431ca1b917SEric Biggers .base.cra_driver_name = "chacha20-generic", 1441ca1b917SEric Biggers .base.cra_priority = 100, 1451ca1b917SEric Biggers .base.cra_blocksize = 1, 1461ca1b917SEric Biggers .base.cra_ctxsize = sizeof(struct chacha_ctx), 1471ca1b917SEric Biggers .base.cra_module = THIS_MODULE, 1481ca1b917SEric Biggers 1491ca1b917SEric Biggers .min_keysize = CHACHA_KEY_SIZE, 1501ca1b917SEric Biggers .max_keysize = CHACHA_KEY_SIZE, 1511ca1b917SEric Biggers .ivsize = CHACHA_IV_SIZE, 1521ca1b917SEric Biggers .chunksize = CHACHA_BLOCK_SIZE, 1531ca1b917SEric Biggers .setkey = crypto_chacha20_setkey, 1541ca1b917SEric Biggers .encrypt = crypto_chacha_crypt, 1551ca1b917SEric Biggers .decrypt = crypto_chacha_crypt, 1561ca1b917SEric Biggers }, { 1571ca1b917SEric Biggers .base.cra_name = "xchacha20", 1581ca1b917SEric Biggers .base.cra_driver_name = "xchacha20-generic", 1591ca1b917SEric Biggers .base.cra_priority = 100, 1601ca1b917SEric Biggers .base.cra_blocksize = 1, 1611ca1b917SEric Biggers .base.cra_ctxsize = sizeof(struct chacha_ctx), 1621ca1b917SEric Biggers .base.cra_module = THIS_MODULE, 1631ca1b917SEric Biggers 1641ca1b917SEric Biggers .min_keysize = CHACHA_KEY_SIZE, 1651ca1b917SEric Biggers .max_keysize = CHACHA_KEY_SIZE, 1661ca1b917SEric Biggers .ivsize = XCHACHA_IV_SIZE, 1671ca1b917SEric Biggers .chunksize = CHACHA_BLOCK_SIZE, 1681ca1b917SEric Biggers .setkey = crypto_chacha20_setkey, 1691ca1b917SEric Biggers .encrypt = crypto_xchacha_crypt, 1701ca1b917SEric Biggers .decrypt = crypto_xchacha_crypt, 1711ca1b917SEric Biggers } 1721ca1b917SEric Biggers }; 1731ca1b917SEric Biggers 1741ca1b917SEric Biggers static int __init chacha_generic_mod_init(void) 1751ca1b917SEric Biggers { 1761ca1b917SEric Biggers return crypto_register_skciphers(algs, ARRAY_SIZE(algs)); 1771ca1b917SEric Biggers } 1781ca1b917SEric Biggers 1791ca1b917SEric Biggers static void __exit chacha_generic_mod_fini(void) 1801ca1b917SEric Biggers { 1811ca1b917SEric Biggers crypto_unregister_skciphers(algs, ARRAY_SIZE(algs)); 1821ca1b917SEric Biggers } 1831ca1b917SEric Biggers 1841ca1b917SEric Biggers module_init(chacha_generic_mod_init); 1851ca1b917SEric Biggers module_exit(chacha_generic_mod_fini); 1861ca1b917SEric Biggers 1871ca1b917SEric Biggers MODULE_LICENSE("GPL"); 1881ca1b917SEric Biggers MODULE_AUTHOR("Martin Willi <martin@strongswan.org>"); 1891ca1b917SEric Biggers MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (generic)"); 1901ca1b917SEric Biggers MODULE_ALIAS_CRYPTO("chacha20"); 1911ca1b917SEric Biggers MODULE_ALIAS_CRYPTO("chacha20-generic"); 1921ca1b917SEric Biggers MODULE_ALIAS_CRYPTO("xchacha20"); 1931ca1b917SEric Biggers MODULE_ALIAS_CRYPTO("xchacha20-generic"); 194