1/* $OpenBSD: hmac.c,v 1.14 2020/02/26 13:40:09 jsg Exp $ */
2/*
3 * Copyright (c) 2014 Markus Friedl.  All rights reserved.
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17#include "includes.h"
18__RCSID("$NetBSD: hmac.c,v 1.8 2020/05/28 17:05:49 christos Exp $");
19
20#include <sys/types.h>
21#include <string.h>
22#include <stdlib.h>
23
24#include "sshbuf.h"
25#include "digest.h"
26#include "hmac.h"
27
28struct ssh_hmac_ctx {
29	int			 alg;
30	struct ssh_digest_ctx	*ictx;
31	struct ssh_digest_ctx	*octx;
32	struct ssh_digest_ctx	*digest;
33	u_char			*buf;
34	size_t			 buf_len;
35};
36
37size_t
38ssh_hmac_bytes(int alg)
39{
40	return ssh_digest_bytes(alg);
41}
42
43struct ssh_hmac_ctx *
44ssh_hmac_start(int alg)
45{
46	struct ssh_hmac_ctx	*ret;
47
48	if ((ret = calloc(1, sizeof(*ret))) == NULL)
49		return NULL;
50	ret->alg = alg;
51	if ((ret->ictx = ssh_digest_start(alg)) == NULL ||
52	    (ret->octx = ssh_digest_start(alg)) == NULL ||
53	    (ret->digest = ssh_digest_start(alg)) == NULL)
54		goto fail;
55	ret->buf_len = ssh_digest_blocksize(ret->ictx);
56	if ((ret->buf = calloc(1, ret->buf_len)) == NULL)
57		goto fail;
58	return ret;
59fail:
60	ssh_hmac_free(ret);
61	return NULL;
62}
63
64int
65ssh_hmac_init(struct ssh_hmac_ctx *ctx, const void *key, size_t klen)
66{
67	size_t i;
68
69	/* reset ictx and octx if no is key given */
70	if (key != NULL) {
71		/* truncate long keys */
72		if (klen <= ctx->buf_len)
73			memcpy(ctx->buf, key, klen);
74		else if (ssh_digest_memory(ctx->alg, key, klen, ctx->buf,
75		    ctx->buf_len) < 0)
76			return -1;
77		for (i = 0; i < ctx->buf_len; i++)
78			ctx->buf[i] ^= 0x36;
79		if (ssh_digest_update(ctx->ictx, ctx->buf, ctx->buf_len) < 0)
80			return -1;
81		for (i = 0; i < ctx->buf_len; i++)
82			ctx->buf[i] ^= 0x36 ^ 0x5c;
83		if (ssh_digest_update(ctx->octx, ctx->buf, ctx->buf_len) < 0)
84			return -1;
85		explicit_bzero(ctx->buf, ctx->buf_len);
86	}
87	/* start with ictx */
88	if (ssh_digest_copy_state(ctx->ictx, ctx->digest) < 0)
89		return -1;
90	return 0;
91}
92
93int
94ssh_hmac_update(struct ssh_hmac_ctx *ctx, const void *m, size_t mlen)
95{
96	return ssh_digest_update(ctx->digest, m, mlen);
97}
98
99int
100ssh_hmac_update_buffer(struct ssh_hmac_ctx *ctx, const struct sshbuf *b)
101{
102	return ssh_digest_update_buffer(ctx->digest, b);
103}
104
105int
106ssh_hmac_final(struct ssh_hmac_ctx *ctx, u_char *d, size_t dlen)
107{
108	size_t len;
109
110	len = ssh_digest_bytes(ctx->alg);
111	if (dlen < len ||
112	    ssh_digest_final(ctx->digest, ctx->buf, len))
113		return -1;
114	/* switch to octx */
115	if (ssh_digest_copy_state(ctx->octx, ctx->digest) < 0 ||
116	    ssh_digest_update(ctx->digest, ctx->buf, len) < 0 ||
117	    ssh_digest_final(ctx->digest, d, dlen) < 0)
118		return -1;
119	return 0;
120}
121
122void
123ssh_hmac_free(struct ssh_hmac_ctx *ctx)
124{
125	if (ctx != NULL) {
126		ssh_digest_free(ctx->ictx);
127		ssh_digest_free(ctx->octx);
128		ssh_digest_free(ctx->digest);
129		if (ctx->buf) {
130			explicit_bzero(ctx->buf, ctx->buf_len);
131			free(ctx->buf);
132		}
133		freezero(ctx, sizeof(*ctx));
134	}
135}
136
137#ifdef TEST
138
139/* cc -DTEST hmac.c digest.c buffer.c cleanup.c fatal.c log.c xmalloc.c -lcrypto */
140static void
141hmac_test(void *key, size_t klen, void *m, size_t mlen, u_char *e, size_t elen)
142{
143	struct ssh_hmac_ctx	*ctx;
144	size_t			 i;
145	u_char			 digest[16];
146
147	if ((ctx = ssh_hmac_start(SSH_DIGEST_MD5)) == NULL)
148		printf("ssh_hmac_start failed");
149	if (ssh_hmac_init(ctx, key, klen) < 0 ||
150	    ssh_hmac_update(ctx, m, mlen) < 0 ||
151	    ssh_hmac_final(ctx, digest, sizeof(digest)) < 0)
152		printf("ssh_hmac_xxx failed");
153	ssh_hmac_free(ctx);
154
155	if (memcmp(e, digest, elen)) {
156		for (i = 0; i < elen; i++)
157			printf("[%zu] %2.2x %2.2x\n", i, e[i], digest[i]);
158		printf("mismatch\n");
159	} else
160		printf("ok\n");
161}
162
163int
164main(int argc, char **argv)
165{
166	/* try test vectors from RFC 2104 */
167
168	u_char key1[16] = {
169	    0xb, 0xb, 0xb, 0xb, 0xb, 0xb, 0xb, 0xb,
170	    0xb, 0xb, 0xb, 0xb, 0xb, 0xb, 0xb, 0xb };
171	u_char *data1 = "Hi There";
172	u_char dig1[16] = {
173	    0x92, 0x94, 0x72, 0x7a, 0x36, 0x38, 0xbb, 0x1c,
174	    0x13, 0xf4, 0x8e, 0xf8, 0x15, 0x8b, 0xfc, 0x9d };
175
176	u_char *key2 = "Jefe";
177	u_char *data2 = "what do ya want for nothing?";
178	u_char dig2[16] = {
179	    0x75, 0x0c, 0x78, 0x3e, 0x6a, 0xb0, 0xb5, 0x03,
180	    0xea, 0xa8, 0x6e, 0x31, 0x0a, 0x5d, 0xb7, 0x38 };
181
182	u_char key3[16];
183	u_char data3[50];
184	u_char dig3[16] = {
185	    0x56, 0xbe, 0x34, 0x52, 0x1d, 0x14, 0x4c, 0x88,
186	    0xdb, 0xb8, 0xc7, 0x33, 0xf0, 0xe8, 0xb3, 0xf6 };
187	memset(key3, 0xaa, sizeof(key3));
188	memset(data3, 0xdd, sizeof(data3));
189
190	hmac_test(key1, sizeof(key1), data1, strlen(data1), dig1, sizeof(dig1));
191	hmac_test(key2, strlen(key2), data2, strlen(data2), dig2, sizeof(dig2));
192	hmac_test(key3, sizeof(key3), data3, sizeof(data3), dig3, sizeof(dig3));
193
194	return 0;
195}
196
197#endif
198