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d2912cb1 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
2cdc6899 | 2 | /* |
8dfa20fc | 3 | * GHASH: hash function for GCM (Galois/Counter Mode). |
2cdc6899 HY |
4 | * |
5 | * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi> | |
6 | * Copyright (c) 2009 Intel Corp. | |
7 | * Author: Huang Ying <ying.huang@intel.com> | |
8dfa20fc EB |
8 | */ |
9 | ||
10 | /* | |
11 | * GHASH is a keyed hash function used in GCM authentication tag generation. | |
12 | * | |
13 | * The original GCM paper [1] presents GHASH as a function GHASH(H, A, C) which | |
14 | * takes a 16-byte hash key H, additional authenticated data A, and a ciphertext | |
15 | * C. It formats A and C into a single byte string X, interprets X as a | |
16 | * polynomial over GF(2^128), and evaluates this polynomial at the point H. | |
17 | * | |
18 | * However, the NIST standard for GCM [2] presents GHASH as GHASH(H, X) where X | |
19 | * is the already-formatted byte string containing both A and C. | |
20 | * | |
21 | * "ghash" in the Linux crypto API uses the 'X' (pre-formatted) convention, | |
22 | * since the API supports only a single data stream per hash. Thus, the | |
23 | * formatting of 'A' and 'C' is done in the "gcm" template, not in "ghash". | |
24 | * | |
25 | * The reason "ghash" is separate from "gcm" is to allow "gcm" to use an | |
26 | * accelerated "ghash" when a standalone accelerated "gcm(aes)" is unavailable. | |
27 | * It is generally inappropriate to use "ghash" for other purposes, since it is | |
28 | * an "ε-almost-XOR-universal hash function", not a cryptographic hash function. | |
29 | * It can only be used securely in crypto modes specially designed to use it. | |
2cdc6899 | 30 | * |
8dfa20fc EB |
31 | * [1] The Galois/Counter Mode of Operation (GCM) |
32 | * (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.694.695&rep=rep1&type=pdf) | |
33 | * [2] Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC | |
34 | * (https://csrc.nist.gov/publications/detail/sp/800-38d/final) | |
2cdc6899 HY |
35 | */ |
36 | ||
37 | #include <crypto/algapi.h> | |
38 | #include <crypto/gf128mul.h> | |
a397ba82 | 39 | #include <crypto/ghash.h> |
2cdc6899 HY |
40 | #include <crypto/internal/hash.h> |
41 | #include <linux/crypto.h> | |
42 | #include <linux/init.h> | |
43 | #include <linux/kernel.h> | |
44 | #include <linux/module.h> | |
45 | ||
2cdc6899 HY |
46 | static int ghash_init(struct shash_desc *desc) |
47 | { | |
48 | struct ghash_desc_ctx *dctx = shash_desc_ctx(desc); | |
49 | ||
50 | memset(dctx, 0, sizeof(*dctx)); | |
51 | ||
52 | return 0; | |
53 | } | |
54 | ||
55 | static int ghash_setkey(struct crypto_shash *tfm, | |
56 | const u8 *key, unsigned int keylen) | |
57 | { | |
58 | struct ghash_ctx *ctx = crypto_shash_ctx(tfm); | |
5c6bc4df | 59 | be128 k; |
2cdc6899 HY |
60 | |
61 | if (keylen != GHASH_BLOCK_SIZE) { | |
62 | crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN); | |
63 | return -EINVAL; | |
64 | } | |
65 | ||
66 | if (ctx->gf128) | |
67 | gf128mul_free_4k(ctx->gf128); | |
5c6bc4df EB |
68 | |
69 | BUILD_BUG_ON(sizeof(k) != GHASH_BLOCK_SIZE); | |
70 | memcpy(&k, key, GHASH_BLOCK_SIZE); /* avoid violating alignment rules */ | |
71 | ctx->gf128 = gf128mul_init_4k_lle(&k); | |
72 | memzero_explicit(&k, GHASH_BLOCK_SIZE); | |
73 | ||
2cdc6899 HY |
74 | if (!ctx->gf128) |
75 | return -ENOMEM; | |
76 | ||
77 | return 0; | |
78 | } | |
79 | ||
80 | static int ghash_update(struct shash_desc *desc, | |
81 | const u8 *src, unsigned int srclen) | |
82 | { | |
83 | struct ghash_desc_ctx *dctx = shash_desc_ctx(desc); | |
84 | struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm); | |
85 | u8 *dst = dctx->buffer; | |
86 | ||
87 | if (dctx->bytes) { | |
88 | int n = min(srclen, dctx->bytes); | |
89 | u8 *pos = dst + (GHASH_BLOCK_SIZE - dctx->bytes); | |
90 | ||
91 | dctx->bytes -= n; | |
92 | srclen -= n; | |
93 | ||
94 | while (n--) | |
95 | *pos++ ^= *src++; | |
96 | ||
97 | if (!dctx->bytes) | |
98 | gf128mul_4k_lle((be128 *)dst, ctx->gf128); | |
99 | } | |
100 | ||
101 | while (srclen >= GHASH_BLOCK_SIZE) { | |
102 | crypto_xor(dst, src, GHASH_BLOCK_SIZE); | |
103 | gf128mul_4k_lle((be128 *)dst, ctx->gf128); | |
104 | src += GHASH_BLOCK_SIZE; | |
105 | srclen -= GHASH_BLOCK_SIZE; | |
106 | } | |
107 | ||
108 | if (srclen) { | |
109 | dctx->bytes = GHASH_BLOCK_SIZE - srclen; | |
110 | while (srclen--) | |
111 | *dst++ ^= *src++; | |
112 | } | |
113 | ||
114 | return 0; | |
115 | } | |
116 | ||
117 | static void ghash_flush(struct ghash_ctx *ctx, struct ghash_desc_ctx *dctx) | |
118 | { | |
119 | u8 *dst = dctx->buffer; | |
120 | ||
121 | if (dctx->bytes) { | |
122 | u8 *tmp = dst + (GHASH_BLOCK_SIZE - dctx->bytes); | |
123 | ||
124 | while (dctx->bytes--) | |
125 | *tmp++ ^= 0; | |
126 | ||
127 | gf128mul_4k_lle((be128 *)dst, ctx->gf128); | |
128 | } | |
129 | ||
130 | dctx->bytes = 0; | |
131 | } | |
132 | ||
133 | static int ghash_final(struct shash_desc *desc, u8 *dst) | |
134 | { | |
135 | struct ghash_desc_ctx *dctx = shash_desc_ctx(desc); | |
136 | struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm); | |
137 | u8 *buf = dctx->buffer; | |
138 | ||
139 | ghash_flush(ctx, dctx); | |
140 | memcpy(dst, buf, GHASH_BLOCK_SIZE); | |
141 | ||
142 | return 0; | |
143 | } | |
144 | ||
145 | static void ghash_exit_tfm(struct crypto_tfm *tfm) | |
146 | { | |
147 | struct ghash_ctx *ctx = crypto_tfm_ctx(tfm); | |
148 | if (ctx->gf128) | |
149 | gf128mul_free_4k(ctx->gf128); | |
150 | } | |
151 | ||
152 | static struct shash_alg ghash_alg = { | |
153 | .digestsize = GHASH_DIGEST_SIZE, | |
154 | .init = ghash_init, | |
155 | .update = ghash_update, | |
156 | .final = ghash_final, | |
157 | .setkey = ghash_setkey, | |
158 | .descsize = sizeof(struct ghash_desc_ctx), | |
159 | .base = { | |
160 | .cra_name = "ghash", | |
161 | .cra_driver_name = "ghash-generic", | |
162 | .cra_priority = 100, | |
2cdc6899 HY |
163 | .cra_blocksize = GHASH_BLOCK_SIZE, |
164 | .cra_ctxsize = sizeof(struct ghash_ctx), | |
165 | .cra_module = THIS_MODULE, | |
2cdc6899 HY |
166 | .cra_exit = ghash_exit_tfm, |
167 | }, | |
168 | }; | |
169 | ||
170 | static int __init ghash_mod_init(void) | |
171 | { | |
172 | return crypto_register_shash(&ghash_alg); | |
173 | } | |
174 | ||
175 | static void __exit ghash_mod_exit(void) | |
176 | { | |
177 | crypto_unregister_shash(&ghash_alg); | |
178 | } | |
179 | ||
c4741b23 | 180 | subsys_initcall(ghash_mod_init); |
2cdc6899 HY |
181 | module_exit(ghash_mod_exit); |
182 | ||
183 | MODULE_LICENSE("GPL"); | |
8dfa20fc | 184 | MODULE_DESCRIPTION("GHASH hash function"); |
5d26a105 | 185 | MODULE_ALIAS_CRYPTO("ghash"); |
3e14dcf7 | 186 | MODULE_ALIAS_CRYPTO("ghash-generic"); |