1 /*
2 * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25 #include "inner.h"
26
27 const unsigned char br_hkdf_no_salt = 0;
28
29 /* see bearssl_kdf.h */
30 void
br_hkdf_init(br_hkdf_context * hc,const br_hash_class * digest_vtable,const void * salt,size_t salt_len)31 br_hkdf_init(br_hkdf_context *hc, const br_hash_class *digest_vtable,
32 const void *salt, size_t salt_len)
33 {
34 br_hmac_key_context kc;
35 unsigned char tmp[64];
36
37 if (salt == BR_HKDF_NO_SALT) {
38 salt = tmp;
39 salt_len = br_digest_size(digest_vtable);
40 memset(tmp, 0, salt_len);
41 }
42 br_hmac_key_init(&kc, digest_vtable, salt, salt_len);
43 br_hmac_init(&hc->u.hmac_ctx, &kc, 0);
44 hc->dig_len = br_hmac_size(&hc->u.hmac_ctx);
45 }
46
47 /* see bearssl_kdf.h */
48 void
br_hkdf_inject(br_hkdf_context * hc,const void * ikm,size_t ikm_len)49 br_hkdf_inject(br_hkdf_context *hc, const void *ikm, size_t ikm_len)
50 {
51 br_hmac_update(&hc->u.hmac_ctx, ikm, ikm_len);
52 }
53
54 /* see bearssl_kdf.h */
55 void
br_hkdf_flip(br_hkdf_context * hc)56 br_hkdf_flip(br_hkdf_context *hc)
57 {
58 unsigned char tmp[64];
59
60 br_hmac_out(&hc->u.hmac_ctx, tmp);
61 br_hmac_key_init(&hc->u.prk_ctx,
62 br_hmac_get_digest(&hc->u.hmac_ctx), tmp, hc->dig_len);
63 hc->ptr = hc->dig_len;
64 hc->chunk_num = 0;
65 }
66
67 /* see bearssl_kdf.h */
68 size_t
br_hkdf_produce(br_hkdf_context * hc,const void * info,size_t info_len,void * out,size_t out_len)69 br_hkdf_produce(br_hkdf_context *hc,
70 const void *info, size_t info_len, void *out, size_t out_len)
71 {
72 size_t tlen;
73
74 tlen = 0;
75 while (out_len > 0) {
76 size_t clen;
77
78 if (hc->ptr == hc->dig_len) {
79 br_hmac_context hmac_ctx;
80 unsigned char x;
81
82 hc->chunk_num ++;
83 if (hc->chunk_num == 256) {
84 return tlen;
85 }
86 x = hc->chunk_num;
87 br_hmac_init(&hmac_ctx, &hc->u.prk_ctx, 0);
88 if (x != 1) {
89 br_hmac_update(&hmac_ctx, hc->buf, hc->dig_len);
90 }
91 br_hmac_update(&hmac_ctx, info, info_len);
92 br_hmac_update(&hmac_ctx, &x, 1);
93 br_hmac_out(&hmac_ctx, hc->buf);
94 hc->ptr = 0;
95 }
96 clen = hc->dig_len - hc->ptr;
97 if (clen > out_len) {
98 clen = out_len;
99 }
100 memcpy(out, hc->buf + hc->ptr, clen);
101 out = (unsigned char *)out + clen;
102 out_len -= clen;
103 hc->ptr += clen;
104 tlen += clen;
105 }
106 return tlen;
107 }
108