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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * GHASH: hash function for GCM (Galois/Counter Mode).
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>
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.
30 *
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)
35 */
36
37#include <crypto/algapi.h>
38#include <crypto/gf128mul.h>
39#include <crypto/ghash.h>
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
46static 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
55static int ghash_setkey(struct crypto_shash *tfm,
56 const u8 *key, unsigned int keylen)
57{
58 struct ghash_ctx *ctx = crypto_shash_ctx(tfm);
59 be128 k;
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);
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
74 if (!ctx->gf128)
75 return -ENOMEM;
76
77 return 0;
78}
79
80static 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
117static 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
133static 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
145static 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
152static 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,
163 .cra_blocksize = GHASH_BLOCK_SIZE,
164 .cra_ctxsize = sizeof(struct ghash_ctx),
165 .cra_module = THIS_MODULE,
166 .cra_exit = ghash_exit_tfm,
167 },
168};
169
170static int __init ghash_mod_init(void)
171{
172 return crypto_register_shash(&ghash_alg);
173}
174
175static void __exit ghash_mod_exit(void)
176{
177 crypto_unregister_shash(&ghash_alg);
178}
179
180subsys_initcall(ghash_mod_init);
181module_exit(ghash_mod_exit);
182
183MODULE_LICENSE("GPL");
184MODULE_DESCRIPTION("GHASH hash function");
185MODULE_ALIAS_CRYPTO("ghash");
186MODULE_ALIAS_CRYPTO("ghash-generic");
1/*
2 * GHASH: digest algorithm for GCM (Galois/Counter Mode).
3 *
4 * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi>
5 * Copyright (c) 2009 Intel Corp.
6 * Author: Huang Ying <ying.huang@intel.com>
7 *
8 * The algorithm implementation is copied from gcm.c.
9 *
10 * This program is free software; you can redistribute it and/or modify it
11 * under the terms of the GNU General Public License version 2 as published
12 * by the Free Software Foundation.
13 */
14
15#include <crypto/algapi.h>
16#include <crypto/gf128mul.h>
17#include <crypto/internal/hash.h>
18#include <linux/crypto.h>
19#include <linux/init.h>
20#include <linux/kernel.h>
21#include <linux/module.h>
22
23#define GHASH_BLOCK_SIZE 16
24#define GHASH_DIGEST_SIZE 16
25
26struct ghash_ctx {
27 struct gf128mul_4k *gf128;
28};
29
30struct ghash_desc_ctx {
31 u8 buffer[GHASH_BLOCK_SIZE];
32 u32 bytes;
33};
34
35static int ghash_init(struct shash_desc *desc)
36{
37 struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
38
39 memset(dctx, 0, sizeof(*dctx));
40
41 return 0;
42}
43
44static int ghash_setkey(struct crypto_shash *tfm,
45 const u8 *key, unsigned int keylen)
46{
47 struct ghash_ctx *ctx = crypto_shash_ctx(tfm);
48
49 if (keylen != GHASH_BLOCK_SIZE) {
50 crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
51 return -EINVAL;
52 }
53
54 if (ctx->gf128)
55 gf128mul_free_4k(ctx->gf128);
56 ctx->gf128 = gf128mul_init_4k_lle((be128 *)key);
57 if (!ctx->gf128)
58 return -ENOMEM;
59
60 return 0;
61}
62
63static int ghash_update(struct shash_desc *desc,
64 const u8 *src, unsigned int srclen)
65{
66 struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
67 struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
68 u8 *dst = dctx->buffer;
69
70 if (!ctx->gf128)
71 return -ENOKEY;
72
73 if (dctx->bytes) {
74 int n = min(srclen, dctx->bytes);
75 u8 *pos = dst + (GHASH_BLOCK_SIZE - dctx->bytes);
76
77 dctx->bytes -= n;
78 srclen -= n;
79
80 while (n--)
81 *pos++ ^= *src++;
82
83 if (!dctx->bytes)
84 gf128mul_4k_lle((be128 *)dst, ctx->gf128);
85 }
86
87 while (srclen >= GHASH_BLOCK_SIZE) {
88 crypto_xor(dst, src, GHASH_BLOCK_SIZE);
89 gf128mul_4k_lle((be128 *)dst, ctx->gf128);
90 src += GHASH_BLOCK_SIZE;
91 srclen -= GHASH_BLOCK_SIZE;
92 }
93
94 if (srclen) {
95 dctx->bytes = GHASH_BLOCK_SIZE - srclen;
96 while (srclen--)
97 *dst++ ^= *src++;
98 }
99
100 return 0;
101}
102
103static void ghash_flush(struct ghash_ctx *ctx, struct ghash_desc_ctx *dctx)
104{
105 u8 *dst = dctx->buffer;
106
107 if (dctx->bytes) {
108 u8 *tmp = dst + (GHASH_BLOCK_SIZE - dctx->bytes);
109
110 while (dctx->bytes--)
111 *tmp++ ^= 0;
112
113 gf128mul_4k_lle((be128 *)dst, ctx->gf128);
114 }
115
116 dctx->bytes = 0;
117}
118
119static int ghash_final(struct shash_desc *desc, u8 *dst)
120{
121 struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
122 struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
123 u8 *buf = dctx->buffer;
124
125 if (!ctx->gf128)
126 return -ENOKEY;
127
128 ghash_flush(ctx, dctx);
129 memcpy(dst, buf, GHASH_BLOCK_SIZE);
130
131 return 0;
132}
133
134static void ghash_exit_tfm(struct crypto_tfm *tfm)
135{
136 struct ghash_ctx *ctx = crypto_tfm_ctx(tfm);
137 if (ctx->gf128)
138 gf128mul_free_4k(ctx->gf128);
139}
140
141static struct shash_alg ghash_alg = {
142 .digestsize = GHASH_DIGEST_SIZE,
143 .init = ghash_init,
144 .update = ghash_update,
145 .final = ghash_final,
146 .setkey = ghash_setkey,
147 .descsize = sizeof(struct ghash_desc_ctx),
148 .base = {
149 .cra_name = "ghash",
150 .cra_driver_name = "ghash-generic",
151 .cra_priority = 100,
152 .cra_flags = CRYPTO_ALG_TYPE_SHASH,
153 .cra_blocksize = GHASH_BLOCK_SIZE,
154 .cra_ctxsize = sizeof(struct ghash_ctx),
155 .cra_module = THIS_MODULE,
156 .cra_list = LIST_HEAD_INIT(ghash_alg.base.cra_list),
157 .cra_exit = ghash_exit_tfm,
158 },
159};
160
161static int __init ghash_mod_init(void)
162{
163 return crypto_register_shash(&ghash_alg);
164}
165
166static void __exit ghash_mod_exit(void)
167{
168 crypto_unregister_shash(&ghash_alg);
169}
170
171module_init(ghash_mod_init);
172module_exit(ghash_mod_exit);
173
174MODULE_LICENSE("GPL");
175MODULE_DESCRIPTION("GHASH Message Digest Algorithm");
176MODULE_ALIAS("ghash");