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_exit		= ghash_exit_tfm,
157	},
158};
159
160static int __init ghash_mod_init(void)
161{
162	return crypto_register_shash(&ghash_alg);
163}
164
165static void __exit ghash_mod_exit(void)
166{
167	crypto_unregister_shash(&ghash_alg);
168}
169
170module_init(ghash_mod_init);
171module_exit(ghash_mod_exit);
172
173MODULE_LICENSE("GPL");
174MODULE_DESCRIPTION("GHASH Message Digest Algorithm");
175MODULE_ALIAS_CRYPTO("ghash");
176MODULE_ALIAS_CRYPTO("ghash-generic");
177