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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 | // SPDX-License-Identifier: GPL-2.0-only /* * 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. * * "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". * * 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 <linux/kernel.h> #include <linux/module.h> static int ghash_init(struct shash_desc *desc) { struct ghash_desc_ctx *dctx = shash_desc_ctx(desc); memset(dctx, 0, sizeof(*dctx)); return 0; } 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) return -EINVAL; if (ctx->gf128) gf128mul_free_4k(ctx->gf128); 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; return 0; } static int ghash_update(struct shash_desc *desc, const u8 *src, unsigned int srclen) { struct ghash_desc_ctx *dctx = shash_desc_ctx(desc); struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm); u8 *dst = dctx->buffer; 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) { 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++; } return 0; } static void ghash_flush(struct ghash_ctx *ctx, struct ghash_desc_ctx *dctx) { u8 *dst = dctx->buffer; if (dctx->bytes) { u8 *tmp = dst + (GHASH_BLOCK_SIZE - dctx->bytes); while (dctx->bytes--) *tmp++ ^= 0; gf128mul_4k_lle((be128 *)dst, ctx->gf128); } dctx->bytes = 0; } static int ghash_final(struct shash_desc *desc, u8 *dst) { struct ghash_desc_ctx *dctx = shash_desc_ctx(desc); struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm); u8 *buf = dctx->buffer; ghash_flush(ctx, dctx); memcpy(dst, buf, GHASH_BLOCK_SIZE); return 0; } static void ghash_exit_tfm(struct crypto_tfm *tfm) { struct ghash_ctx *ctx = crypto_tfm_ctx(tfm); if (ctx->gf128) gf128mul_free_4k(ctx->gf128); } static struct shash_alg ghash_alg = { .digestsize = GHASH_DIGEST_SIZE, .init = ghash_init, .update = ghash_update, .final = ghash_final, .setkey = ghash_setkey, .descsize = sizeof(struct ghash_desc_ctx), .base = { .cra_name = "ghash", .cra_driver_name = "ghash-generic", .cra_priority = 100, .cra_blocksize = GHASH_BLOCK_SIZE, .cra_ctxsize = sizeof(struct ghash_ctx), .cra_module = THIS_MODULE, .cra_exit = ghash_exit_tfm, }, }; static int __init ghash_mod_init(void) { return crypto_register_shash(&ghash_alg); } static void __exit ghash_mod_exit(void) { crypto_unregister_shash(&ghash_alg); } subsys_initcall(ghash_mod_init); module_exit(ghash_mod_exit); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("GHASH hash function"); MODULE_ALIAS_CRYPTO("ghash"); MODULE_ALIAS_CRYPTO("ghash-generic"); |