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 (dctx->bytes) {
71		int n = min(srclen, dctx->bytes);
72		u8 *pos = dst + (GHASH_BLOCK_SIZE - dctx->bytes);
73
74		dctx->bytes -= n;
75		srclen -= n;
76
77		while (n--)
78			*pos++ ^= *src++;
79
80		if (!dctx->bytes)
81			gf128mul_4k_lle((be128 *)dst, ctx->gf128);
82	}
83
84	while (srclen >= GHASH_BLOCK_SIZE) {
85		crypto_xor(dst, src, GHASH_BLOCK_SIZE);
86		gf128mul_4k_lle((be128 *)dst, ctx->gf128);
87		src += GHASH_BLOCK_SIZE;
88		srclen -= GHASH_BLOCK_SIZE;
89	}
90
91	if (srclen) {
92		dctx->bytes = GHASH_BLOCK_SIZE - srclen;
93		while (srclen--)
94			*dst++ ^= *src++;
95	}
96
97	return 0;
98}
99
100static void ghash_flush(struct ghash_ctx *ctx, struct ghash_desc_ctx *dctx)
101{
102	u8 *dst = dctx->buffer;
103
104	if (dctx->bytes) {
105		u8 *tmp = dst + (GHASH_BLOCK_SIZE - dctx->bytes);
106
107		while (dctx->bytes--)
108			*tmp++ ^= 0;
109
110		gf128mul_4k_lle((be128 *)dst, ctx->gf128);
111	}
112
113	dctx->bytes = 0;
114}
115
116static int ghash_final(struct shash_desc *desc, u8 *dst)
117{
118	struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
119	struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
120	u8 *buf = dctx->buffer;
121
122	ghash_flush(ctx, dctx);
123	memcpy(dst, buf, GHASH_BLOCK_SIZE);
124
125	return 0;
126}
127
128static void ghash_exit_tfm(struct crypto_tfm *tfm)
129{
130	struct ghash_ctx *ctx = crypto_tfm_ctx(tfm);
131	if (ctx->gf128)
132		gf128mul_free_4k(ctx->gf128);
133}
134
135static struct shash_alg ghash_alg = {
136	.digestsize	= GHASH_DIGEST_SIZE,
137	.init		= ghash_init,
138	.update		= ghash_update,
139	.final		= ghash_final,
140	.setkey		= ghash_setkey,
141	.descsize	= sizeof(struct ghash_desc_ctx),
142	.base		= {
143		.cra_name		= "ghash",
144		.cra_driver_name	= "ghash-generic",
145		.cra_priority		= 100,
146		.cra_flags		= CRYPTO_ALG_TYPE_SHASH,
147		.cra_blocksize		= GHASH_BLOCK_SIZE,
148		.cra_ctxsize		= sizeof(struct ghash_ctx),
149		.cra_module		= THIS_MODULE,
150		.cra_list		= LIST_HEAD_INIT(ghash_alg.base.cra_list),
151		.cra_exit		= ghash_exit_tfm,
152	},
153};
154
155static int __init ghash_mod_init(void)
156{
157	return crypto_register_shash(&ghash_alg);
158}
159
160static void __exit ghash_mod_exit(void)
161{
162	crypto_unregister_shash(&ghash_alg);
163}
164
165module_init(ghash_mod_init);
166module_exit(ghash_mod_exit);
167
168MODULE_LICENSE("GPL");
169MODULE_DESCRIPTION("GHASH Message Digest Algorithm");
170MODULE_ALIAS("ghash");
171