1/*
2 * Poly1305 authenticator algorithm, RFC7539
3 *
4 * Copyright (C) 2015 Martin Willi
5 *
6 * Based on public domain code by Andrew Moon and Daniel J. Bernstein.
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 */
13
14#include <crypto/algapi.h>
15#include <crypto/internal/hash.h>
16#include <crypto/internal/poly1305.h>
17#include <linux/crypto.h>
18#include <linux/kernel.h>
19#include <linux/module.h>
20#include <asm/unaligned.h>
21
22static int crypto_poly1305_init(struct shash_desc *desc)
23{
24	struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);
25
26	poly1305_core_init(&dctx->h);
27	dctx->buflen = 0;
28	dctx->rset = 0;
29	dctx->sset = false;
30
31	return 0;
32}
33
34static unsigned int crypto_poly1305_setdesckey(struct poly1305_desc_ctx *dctx,
35					       const u8 *src, unsigned int srclen)
36{
37	if (!dctx->sset) {
38		if (!dctx->rset && srclen >= POLY1305_BLOCK_SIZE) {
39			poly1305_core_setkey(&dctx->core_r, src);
40			src += POLY1305_BLOCK_SIZE;
41			srclen -= POLY1305_BLOCK_SIZE;
42			dctx->rset = 2;
43		}
44		if (srclen >= POLY1305_BLOCK_SIZE) {
45			dctx->s[0] = get_unaligned_le32(src +  0);
46			dctx->s[1] = get_unaligned_le32(src +  4);
47			dctx->s[2] = get_unaligned_le32(src +  8);
48			dctx->s[3] = get_unaligned_le32(src + 12);
49			src += POLY1305_BLOCK_SIZE;
50			srclen -= POLY1305_BLOCK_SIZE;
51			dctx->sset = true;
52		}
53	}
54	return srclen;
55}
56
57static void poly1305_blocks(struct poly1305_desc_ctx *dctx, const u8 *src,
58			    unsigned int srclen)
59{
60	unsigned int datalen;
61
62	if (unlikely(!dctx->sset)) {
63		datalen = crypto_poly1305_setdesckey(dctx, src, srclen);
64		src += srclen - datalen;
65		srclen = datalen;
66	}
67
68	poly1305_core_blocks(&dctx->h, &dctx->core_r, src,
69			     srclen / POLY1305_BLOCK_SIZE, 1);
70}
71
72static int crypto_poly1305_update(struct shash_desc *desc,
73				  const u8 *src, unsigned int srclen)
74{
75	struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);
76	unsigned int bytes;
77
78	if (unlikely(dctx->buflen)) {
79		bytes = min(srclen, POLY1305_BLOCK_SIZE - dctx->buflen);
80		memcpy(dctx->buf + dctx->buflen, src, bytes);
81		src += bytes;
82		srclen -= bytes;
83		dctx->buflen += bytes;
84
85		if (dctx->buflen == POLY1305_BLOCK_SIZE) {
86			poly1305_blocks(dctx, dctx->buf,
87					POLY1305_BLOCK_SIZE);
88			dctx->buflen = 0;
89		}
90	}
91
92	if (likely(srclen >= POLY1305_BLOCK_SIZE)) {
93		poly1305_blocks(dctx, src, srclen);
94		src += srclen - (srclen % POLY1305_BLOCK_SIZE);
95		srclen %= POLY1305_BLOCK_SIZE;
96	}
97
98	if (unlikely(srclen)) {
99		dctx->buflen = srclen;
100		memcpy(dctx->buf, src, srclen);
101	}
102
103	return 0;
104}
105
106static int crypto_poly1305_final(struct shash_desc *desc, u8 *dst)
107{
108	struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);
109
110	if (unlikely(!dctx->sset))
111		return -ENOKEY;
112
113	poly1305_final_generic(dctx, dst);
114	return 0;
115}
116
117static struct shash_alg poly1305_alg = {
118	.digestsize	= POLY1305_DIGEST_SIZE,
119	.init		= crypto_poly1305_init,
120	.update		= crypto_poly1305_update,
121	.final		= crypto_poly1305_final,
122	.descsize	= sizeof(struct poly1305_desc_ctx),
123	.base		= {
124		.cra_name		= "poly1305",
125		.cra_driver_name	= "poly1305-generic",
126		.cra_priority		= 100,
127		.cra_blocksize		= POLY1305_BLOCK_SIZE,
128		.cra_module		= THIS_MODULE,
129	},
130};
131
132static int __init poly1305_mod_init(void)
133{
134	return crypto_register_shash(&poly1305_alg);
135}
136
137static void __exit poly1305_mod_exit(void)
138{
139	crypto_unregister_shash(&poly1305_alg);
140}
141
142subsys_initcall(poly1305_mod_init);
143module_exit(poly1305_mod_exit);
144
145MODULE_LICENSE("GPL");
146MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
147MODULE_DESCRIPTION("Poly1305 authenticator");
148MODULE_ALIAS_CRYPTO("poly1305");
149MODULE_ALIAS_CRYPTO("poly1305-generic");
150