1 | /* |
2 | * Copyright (C) 2011 Collabora Ltd. |
3 | * Copyright (C) 2018 Alexander Volkov <a.volkov@rusbitech.ru> |
4 | * |
5 | * This program is free software; you can redistribute it and/or modify |
6 | * it under the terms of the GNU Lesser General Public License as |
7 | * published by the Free Software Foundation; either version 2.1 of |
8 | * the License, or (at your option) any later version. |
9 | * |
10 | * This program is distributed in the hope that it will be useful, but |
11 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | * Lesser General Public License for more details. |
14 | * |
15 | * You should have received a copy of the GNU Lesser General Public |
16 | * License along with this program; if not, write to the Free Software |
17 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, |
18 | * MA 02110-1301 USA |
19 | * |
20 | * Author: Stef Walter <stefw@collabora.co.uk> |
21 | */ |
22 | |
23 | #include <gcrypt.h> |
24 | |
25 | static gcry_error_t gcry_hkdf(int algo, |
26 | const char *input, |
27 | size_t n_input, |
28 | const char *salt, |
29 | size_t n_salt, |
30 | const char *info, |
31 | size_t n_info, |
32 | char *output, |
33 | size_t n_output) |
34 | { |
35 | void *alloc = nullptr; |
36 | void *buffer = nullptr; |
37 | gcry_md_hd_t md1, md2; |
38 | unsigned int hash_len; |
39 | int i; |
40 | size_t step, n_buffer; |
41 | char *at; |
42 | gcry_error_t gcry; |
43 | |
44 | hash_len = gcry_md_get_algo_dlen(algo); |
45 | if (hash_len == 0) { |
46 | return GPG_ERR_UNSUPPORTED_ALGORITHM; |
47 | } |
48 | |
49 | if (n_output > 255 * hash_len) { |
50 | return GPG_ERR_TOO_LARGE; |
51 | } |
52 | |
53 | /* Buffer we need to for intermediate stuff */ |
54 | buffer = gcry_malloc_secure(n: hash_len); |
55 | if (!buffer) { |
56 | return GPG_ERR_ENOMEM; |
57 | } |
58 | n_buffer = 0; |
59 | |
60 | /* Salt defaults to hash_len zeros */ |
61 | if (!salt) { |
62 | alloc = gcry_calloc_secure(n: hash_len, m: 1); |
63 | if (!alloc) { |
64 | return GPG_ERR_ENOMEM; |
65 | } |
66 | salt = (const char *)alloc; |
67 | n_salt = hash_len; |
68 | } |
69 | |
70 | /* Step 1: Extract */ |
71 | gcry = gcry_md_open(h: &md1, algo, flags: GCRY_MD_FLAG_HMAC | GCRY_MD_FLAG_SECURE); |
72 | if (gcry != GPG_ERR_NO_ERROR) { |
73 | goto done; |
74 | } |
75 | gcry = gcry_md_setkey(hd: md1, key: salt, keylen: n_salt); |
76 | if (gcry != GPG_ERR_NO_ERROR) { |
77 | gcry_md_close(hd: md1); |
78 | goto done; |
79 | } |
80 | gcry_md_write(hd: md1, buffer: input, length: n_input); |
81 | |
82 | /* Step 2: Expand */ |
83 | gcry = gcry_md_open(h: &md2, algo, flags: GCRY_MD_FLAG_HMAC | GCRY_MD_FLAG_SECURE); |
84 | if (gcry != GPG_ERR_NO_ERROR) { |
85 | gcry_md_close(hd: md1); |
86 | goto done; |
87 | } |
88 | gcry = gcry_md_setkey(hd: md2, key: gcry_md_read(hd: md1, algo), keylen: hash_len); |
89 | if (gcry != GPG_ERR_NO_ERROR) { |
90 | gcry_md_close(hd: md2); |
91 | gcry_md_close(hd: md1); |
92 | goto done; |
93 | } |
94 | gcry_md_close(hd: md1); |
95 | |
96 | at = output; |
97 | for (i = 1; i < 256; ++i) { |
98 | gcry_md_reset(hd: md2); |
99 | gcry_md_write(hd: md2, buffer, length: n_buffer); |
100 | gcry_md_write(hd: md2, buffer: info, length: n_info); |
101 | gcry_md_putc(md2, i); |
102 | |
103 | n_buffer = hash_len; |
104 | memcpy(dest: buffer, src: gcry_md_read(hd: md2, algo), n: n_buffer); |
105 | |
106 | step = n_buffer < n_output ? n_buffer : n_output; |
107 | memcpy(dest: at, src: buffer, n: step); |
108 | n_output -= step; |
109 | at += step; |
110 | |
111 | if (!n_output) |
112 | break; |
113 | } |
114 | gcry_md_close(hd: md2); |
115 | |
116 | done: |
117 | gcry_free(a: alloc); |
118 | gcry_free(a: buffer); |
119 | return gcry; |
120 | } |
121 | |