diff options
Diffstat (limited to 'crypto/ghash-generic.c')
| -rw-r--r-- | crypto/ghash-generic.c | 125 |
1 files changed, 56 insertions, 69 deletions
diff --git a/crypto/ghash-generic.c b/crypto/ghash-generic.c index 9d3f0c69a86f..e5803c249c12 100644 --- a/crypto/ghash-generic.c +++ b/crypto/ghash-generic.c @@ -1,36 +1,47 @@ +// SPDX-License-Identifier: GPL-2.0-only /* - * GHASH: digest algorithm for GCM (Galois/Counter Mode). + * GHASH: hash function for GCM (Galois/Counter Mode). * * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi> * Copyright (c) 2009 Intel Corp. * Author: Huang Ying <ying.huang@intel.com> + */ + +/* + * GHASH is a keyed hash function used in GCM authentication tag generation. + * + * The original GCM paper [1] presents GHASH as a function GHASH(H, A, C) which + * takes a 16-byte hash key H, additional authenticated data A, and a ciphertext + * C. It formats A and C into a single byte string X, interprets X as a + * polynomial over GF(2^128), and evaluates this polynomial at the point H. + * + * However, the NIST standard for GCM [2] presents GHASH as GHASH(H, X) where X + * is the already-formatted byte string containing both A and C. * - * The algorithm implementation is copied from gcm.c. + * "ghash" in the Linux crypto API uses the 'X' (pre-formatted) convention, + * since the API supports only a single data stream per hash. Thus, the + * formatting of 'A' and 'C' is done in the "gcm" template, not in "ghash". * - * This program is free software; you can redistribute it and/or modify it - * under the terms of the GNU General Public License version 2 as published - * by the Free Software Foundation. + * The reason "ghash" is separate from "gcm" is to allow "gcm" to use an + * accelerated "ghash" when a standalone accelerated "gcm(aes)" is unavailable. + * It is generally inappropriate to use "ghash" for other purposes, since it is + * an "ε-almost-XOR-universal hash function", not a cryptographic hash function. + * It can only be used securely in crypto modes specially designed to use it. + * + * [1] The Galois/Counter Mode of Operation (GCM) + * (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.694.695&rep=rep1&type=pdf) + * [2] Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC + * (https://csrc.nist.gov/publications/detail/sp/800-38d/final) */ -#include <crypto/algapi.h> #include <crypto/gf128mul.h> +#include <crypto/ghash.h> #include <crypto/internal/hash.h> -#include <linux/crypto.h> -#include <linux/init.h> +#include <crypto/utils.h> +#include <linux/err.h> #include <linux/kernel.h> #include <linux/module.h> - -#define GHASH_BLOCK_SIZE 16 -#define GHASH_DIGEST_SIZE 16 - -struct ghash_ctx { - struct gf128mul_4k *gf128; -}; - -struct ghash_desc_ctx { - u8 buffer[GHASH_BLOCK_SIZE]; - u32 bytes; -}; +#include <linux/string.h> static int ghash_init(struct shash_desc *desc) { @@ -45,15 +56,19 @@ static int ghash_setkey(struct crypto_shash *tfm, const u8 *key, unsigned int keylen) { struct ghash_ctx *ctx = crypto_shash_ctx(tfm); + be128 k; - if (keylen != GHASH_BLOCK_SIZE) { - crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN); + if (keylen != GHASH_BLOCK_SIZE) return -EINVAL; - } if (ctx->gf128) gf128mul_free_4k(ctx->gf128); - ctx->gf128 = gf128mul_init_4k_lle((be128 *)key); + + BUILD_BUG_ON(sizeof(k) != GHASH_BLOCK_SIZE); + memcpy(&k, key, GHASH_BLOCK_SIZE); /* avoid violating alignment rules */ + ctx->gf128 = gf128mul_init_4k_lle(&k); + memzero_explicit(&k, GHASH_BLOCK_SIZE); + if (!ctx->gf128) return -ENOMEM; @@ -67,65 +82,36 @@ static int ghash_update(struct shash_desc *desc, struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm); u8 *dst = dctx->buffer; - if (!ctx->gf128) - return -ENOKEY; - - if (dctx->bytes) { - int n = min(srclen, dctx->bytes); - u8 *pos = dst + (GHASH_BLOCK_SIZE - dctx->bytes); - - dctx->bytes -= n; - srclen -= n; - - while (n--) - *pos++ ^= *src++; - - if (!dctx->bytes) - gf128mul_4k_lle((be128 *)dst, ctx->gf128); - } - - while (srclen >= GHASH_BLOCK_SIZE) { + do { crypto_xor(dst, src, GHASH_BLOCK_SIZE); gf128mul_4k_lle((be128 *)dst, ctx->gf128); src += GHASH_BLOCK_SIZE; srclen -= GHASH_BLOCK_SIZE; - } - - if (srclen) { - dctx->bytes = GHASH_BLOCK_SIZE - srclen; - while (srclen--) - *dst++ ^= *src++; - } + } while (srclen >= GHASH_BLOCK_SIZE); - return 0; + return srclen; } -static void ghash_flush(struct ghash_ctx *ctx, struct ghash_desc_ctx *dctx) +static void ghash_flush(struct shash_desc *desc, const u8 *src, + unsigned int len) { + struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm); + struct ghash_desc_ctx *dctx = shash_desc_ctx(desc); u8 *dst = dctx->buffer; - if (dctx->bytes) { - u8 *tmp = dst + (GHASH_BLOCK_SIZE - dctx->bytes); - - while (dctx->bytes--) - *tmp++ ^= 0; - + if (len) { + crypto_xor(dst, src, len); gf128mul_4k_lle((be128 *)dst, ctx->gf128); } - - dctx->bytes = 0; } -static int ghash_final(struct shash_desc *desc, u8 *dst) +static int ghash_finup(struct shash_desc *desc, const u8 *src, + unsigned int len, u8 *dst) { struct ghash_desc_ctx *dctx = shash_desc_ctx(desc); - struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm); u8 *buf = dctx->buffer; - if (!ctx->gf128) - return -ENOKEY; - - ghash_flush(ctx, dctx); + ghash_flush(desc, src, len); memcpy(dst, buf, GHASH_BLOCK_SIZE); return 0; @@ -142,14 +128,14 @@ static struct shash_alg ghash_alg = { .digestsize = GHASH_DIGEST_SIZE, .init = ghash_init, .update = ghash_update, - .final = ghash_final, + .finup = ghash_finup, .setkey = ghash_setkey, .descsize = sizeof(struct ghash_desc_ctx), .base = { .cra_name = "ghash", .cra_driver_name = "ghash-generic", .cra_priority = 100, - .cra_flags = CRYPTO_ALG_TYPE_SHASH, + .cra_flags = CRYPTO_AHASH_ALG_BLOCK_ONLY, .cra_blocksize = GHASH_BLOCK_SIZE, .cra_ctxsize = sizeof(struct ghash_ctx), .cra_module = THIS_MODULE, @@ -171,5 +157,6 @@ module_init(ghash_mod_init); module_exit(ghash_mod_exit); MODULE_LICENSE("GPL"); -MODULE_DESCRIPTION("GHASH Message Digest Algorithm"); -MODULE_ALIAS("ghash"); +MODULE_DESCRIPTION("GHASH hash function"); +MODULE_ALIAS_CRYPTO("ghash"); +MODULE_ALIAS_CRYPTO("ghash-generic"); |