1 /*
2 * SAE-PK password/modifier generator
3 * Copyright (c) 2020, The Linux Foundation
4 *
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
7 */
8
9 #include "utils/includes.h"
10
11 #include "utils/common.h"
12 #include "utils/base64.h"
13 #include "crypto/crypto.h"
14 #include "common/sae.h"
15
16
main(int argc,char * argv[])17 int main(int argc, char *argv[])
18 {
19 char *der = NULL;
20 size_t der_len;
21 struct crypto_ec_key *key = NULL;
22 struct wpabuf *pub = NULL;
23 u8 *data = NULL, *m;
24 size_t data_len;
25 char *b64 = NULL, *pw = NULL, *pos, *src;
26 int sec, j;
27 int ret = -1;
28 u8 hash[SAE_MAX_HASH_LEN];
29 char hash_hex[2 * SAE_MAX_HASH_LEN + 1];
30 u8 pw_base_bin[SAE_MAX_HASH_LEN];
31 u8 *dst;
32 int group;
33 size_t hash_len;
34 unsigned long long i, expected;
35 char m_hex[2 * SAE_PK_M_LEN + 1];
36 u32 sec_1b, val20;
37
38 wpa_debug_level = MSG_INFO;
39 if (os_program_init() < 0)
40 goto fail;
41
42 if (argc != 4) {
43 fprintf(stderr,
44 "usage: sae_pk_gen <DER ECPrivateKey file> <Sec:3|5> <SSID>\n");
45 goto fail;
46 }
47
48 sec = atoi(argv[2]);
49 if (sec != 3 && sec != 5) {
50 fprintf(stderr,
51 "Invalid Sec value (allowed values: 3 and 5)\n");
52 goto fail;
53 }
54 sec_1b = sec == 3;
55 expected = 1;
56 for (j = 0; j < sec; j++)
57 expected *= 256;
58
59 der = os_readfile(argv[1], &der_len);
60 if (!der) {
61 fprintf(stderr, "Could not read %s: %s\n",
62 argv[1], strerror(errno));
63 goto fail;
64 }
65
66 key = crypto_ec_key_parse_priv((u8 *) der, der_len);
67 if (!key) {
68 fprintf(stderr, "Could not parse ECPrivateKey\n");
69 goto fail;
70 }
71
72 pub = crypto_ec_key_get_subject_public_key(key);
73 if (!pub) {
74 fprintf(stderr, "Failed to build SubjectPublicKey\n");
75 goto fail;
76 }
77
78 group = crypto_ec_key_group(key);
79 switch (group) {
80 case 19:
81 hash_len = 32;
82 break;
83 case 20:
84 hash_len = 48;
85 break;
86 case 21:
87 hash_len = 64;
88 break;
89 default:
90 fprintf(stderr, "Unsupported private key group\n");
91 goto fail;
92 }
93
94 data_len = os_strlen(argv[3]) + SAE_PK_M_LEN + wpabuf_len(pub);
95 data = os_malloc(data_len);
96 if (!data) {
97 fprintf(stderr, "No memory for data buffer\n");
98 goto fail;
99 }
100 os_memcpy(data, argv[3], os_strlen(argv[3]));
101 m = data + os_strlen(argv[3]);
102 if (os_get_random(m, SAE_PK_M_LEN) < 0) {
103 fprintf(stderr, "Could not generate random Modifier M\n");
104 goto fail;
105 }
106 os_memcpy(m + SAE_PK_M_LEN, wpabuf_head(pub), wpabuf_len(pub));
107
108 fprintf(stderr, "Searching for a suitable Modifier M value\n");
109 for (i = 0;; i++) {
110 if (sae_hash(hash_len, data, data_len, hash) < 0) {
111 fprintf(stderr, "Hash failed\n");
112 goto fail;
113 }
114 if (hash[0] == 0 && hash[1] == 0) {
115 if ((hash[2] & 0xf0) == 0)
116 fprintf(stderr, "\r%3.2f%%",
117 100.0 * (double) i / (double) expected);
118 for (j = 2; j < sec; j++) {
119 if (hash[j])
120 break;
121 }
122 if (j == sec)
123 break;
124 }
125 inc_byte_array(m, SAE_PK_M_LEN);
126 }
127
128 if (wpa_snprintf_hex(m_hex, sizeof(m_hex), m, SAE_PK_M_LEN) < 0 ||
129 wpa_snprintf_hex(hash_hex, sizeof(hash_hex), hash, hash_len) < 0)
130 goto fail;
131 fprintf(stderr, "\nFound a valid hash in %llu iterations: %s\n",
132 i + 1, hash_hex);
133
134 b64 = base64_encode(der, der_len, NULL);
135 if (!b64)
136 goto fail;
137 src = pos = b64;
138 while (*src) {
139 if (*src != '\n')
140 *pos++ = *src;
141 src++;
142 }
143 *pos = '\0';
144
145 /* Skip 8*Sec bits and add Sec_1b as the every 20th bit starting with
146 * one. */
147 os_memset(pw_base_bin, 0, sizeof(pw_base_bin));
148 dst = pw_base_bin;
149 for (j = 0; j < 8 * (int) hash_len / 20; j++) {
150 val20 = sae_pk_get_be19(hash + sec);
151 val20 |= sec_1b << 19;
152 sae_pk_buf_shift_left_19(hash + sec, hash_len - sec);
153
154 if (j & 1) {
155 *dst |= (val20 >> 16) & 0x0f;
156 dst++;
157 *dst++ = (val20 >> 8) & 0xff;
158 *dst++ = val20 & 0xff;
159 } else {
160 *dst++ = (val20 >> 12) & 0xff;
161 *dst++ = (val20 >> 4) & 0xff;
162 *dst = (val20 << 4) & 0xf0;
163 }
164 }
165 if (wpa_snprintf_hex(hash_hex, sizeof(hash_hex),
166 pw_base_bin, hash_len - sec) >= 0)
167 fprintf(stderr, "PasswordBase binary data for base32: %s",
168 hash_hex);
169
170 pw = sae_pk_base32_encode(pw_base_bin, 20 * 3 - 5);
171 if (!pw)
172 goto fail;
173
174 printf("# SAE-PK password/M/private key for Sec=%d.\n", sec);
175 printf("sae_password=%s|pk=%s:%s\n", pw, m_hex, b64);
176 printf("# Longer passwords can be used for improved security at the cost of usability:\n");
177 for (j = 4; j <= ((int) hash_len * 8 + 5 - 8 * sec) / 19; j++) {
178 os_free(pw);
179 pw = sae_pk_base32_encode(pw_base_bin, 20 * j - 5);
180 if (pw)
181 printf("# %s\n", pw);
182 }
183
184 ret = 0;
185 fail:
186 os_free(der);
187 wpabuf_free(pub);
188 crypto_ec_key_deinit(key);
189 os_free(data);
190 os_free(b64);
191 os_free(pw);
192
193 os_program_deinit();
194
195 return ret;
196 }
197
