1 /* $NetBSD: wg-keygen.c,v 1.1 2020/08/20 21:28:02 riastradh Exp $ */
2
3 /*
4 * Copyright (C) Ryota Ozaki <ozaki.ryota@gmail.com>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the project nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #include <sys/cdefs.h>
33 __RCSID("$NetBSD: wg-keygen.c,v 1.1 2020/08/20 21:28:02 riastradh Exp $");
34
35 #include <stdio.h>
36 #include <stdlib.h>
37 #include <err.h>
38 #include <resolv.h>
39 #include <string.h>
40
41 #define KEY_LEN 32
42 #define KEY_BASE64_LEN 44
43
44 __dead static void
usage(void)45 usage(void)
46 {
47 const char *progname = getprogname();
48
49 fprintf(stderr, "Usage:\n");
50 fprintf(stderr, "\t%s : Generate a private key\n", progname);
51 fprintf(stderr, "\t%s --pub : Generate a public key from a private key via stdin\n", progname);
52 fprintf(stderr, "\t%s --psk : Generate a pre-shared key\n", progname);
53
54 exit(EXIT_FAILURE);
55 }
56
57 /* Mimic crypto/external/bsd/openssh/dist/kexc25519.c */
58 #define CURVE25519_SIZE 32
59 extern int crypto_scalarmult_curve25519(uint8_t [CURVE25519_SIZE],
60 const uint8_t [CURVE25519_SIZE], const uint8_t [CURVE25519_SIZE]);
61
62 static void
gen_pubkey(uint8_t key[CURVE25519_SIZE],uint8_t pubkey[CURVE25519_SIZE])63 gen_pubkey(uint8_t key[CURVE25519_SIZE], uint8_t pubkey[CURVE25519_SIZE])
64 {
65 static const uint8_t basepoint[CURVE25519_SIZE] = {9};
66
67 crypto_scalarmult_curve25519(pubkey, key, basepoint);
68 }
69
70 static void
normalize_key(uint8_t key[KEY_LEN])71 normalize_key(uint8_t key[KEY_LEN])
72 {
73
74 /* Mimic the official implementation, wg */
75 key[0] &= 248;
76 key[31] &= 127;
77 key[31] |= 64;
78 }
79
80 static char *
base64(uint8_t key[KEY_LEN])81 base64(uint8_t key[KEY_LEN])
82 {
83 static char key_b64[KEY_BASE64_LEN + 1];
84 int error;
85
86 error = b64_ntop(key, KEY_LEN, key_b64, KEY_BASE64_LEN + 1);
87 if (error == -1)
88 errx(EXIT_FAILURE, "b64_ntop failed");
89 key_b64[KEY_BASE64_LEN] = '\0'; /* just in case */
90
91 return key_b64;
92 }
93
94 int
main(int argc,char * argv[])95 main(int argc, char *argv[])
96 {
97 uint8_t key[KEY_LEN];
98
99 if (!(argc == 1 || argc == 2))
100 usage();
101
102 if (argc == 1) {
103 arc4random_buf(key, KEY_LEN);
104 normalize_key(key);
105 printf("%s\n", base64(key));
106 return 0;
107 }
108
109 if (strcmp(argv[1], "--psk") == 0) {
110 arc4random_buf(key, KEY_LEN);
111 printf("%s\n", base64(key));
112 return 0;
113 }
114
115 if (strcmp(argv[1], "--pub") == 0) {
116 char key_b64[KEY_BASE64_LEN + 1];
117 int ret;
118 char *retc;
119 uint8_t pubkey[KEY_LEN];
120
121 retc = fgets(key_b64, KEY_BASE64_LEN + 1, stdin);
122 if (retc == NULL)
123 err(EXIT_FAILURE, "fgets");
124 key_b64[KEY_BASE64_LEN] = '\0';
125 if (strlen(key_b64) != KEY_BASE64_LEN)
126 errx(EXIT_FAILURE, "Invalid length of a private key");
127 ret = b64_pton(key_b64, key, KEY_LEN);
128 if (ret == -1)
129 errx(EXIT_FAILURE, "b64_pton failed");
130 gen_pubkey(key, pubkey);
131 printf("%s\n", base64(pubkey));
132 return 0;
133 }
134
135 usage();
136 }
137