1 /* $OpenBSD: ssh-keysign.c,v 1.29 2006/08/03 03:34:42 deraadt Exp $ */
2 /*
3 * Copyright (c) 2002 Markus Friedl. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26 #include <sys/types.h>
27
28 #include <openssl/evp.h>
29 #include <openssl/rand.h>
30 #include <openssl/rsa.h>
31
32 #include <fcntl.h>
33 #include <paths.h>
34 #include <pwd.h>
35 #include <stdlib.h>
36 #include <string.h>
37 #include <unistd.h>
38
39 #include "xmalloc.h"
40 #include "log.h"
41 #include "key.h"
42 #include "ssh.h"
43 #include "ssh2.h"
44 #include "misc.h"
45 #include "buffer.h"
46 #include "authfile.h"
47 #include "msg.h"
48 #include "canohost.h"
49 #include "pathnames.h"
50 #include "readconf.h"
51 #include "uidswap.h"
52
53 __RCSID("$MirOS: src/usr.bin/ssh/ssh-keysign.c,v 1.7 2014/03/13 04:46:47 tg Exp $");
54
55 /* XXX readconf.c needs these */
56 uid_t original_real_uid;
57
58 static int
valid_request(struct passwd * pw,char * host,Key ** ret,u_char * data,u_int datalen)59 valid_request(struct passwd *pw, char *host, Key **ret, u_char *data,
60 u_int datalen)
61 {
62 Buffer b;
63 Key *key = NULL;
64 u_char *pkblob;
65 u_int blen, len;
66 char *pkalg, *p;
67 int pktype, fail;
68
69 fail = 0;
70
71 buffer_init(&b);
72 buffer_append(&b, data, datalen);
73
74 /* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */
75 p = buffer_get_string(&b, &len);
76 if (len != 20 && len != 32)
77 fail++;
78 xfree(p);
79
80 if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST)
81 fail++;
82
83 /* server user */
84 buffer_skip_string(&b);
85
86 /* service */
87 p = buffer_get_string(&b, NULL);
88 if (strcmp("ssh-connection", p) != 0)
89 fail++;
90 xfree(p);
91
92 /* method */
93 p = buffer_get_string(&b, NULL);
94 if (strcmp("hostbased", p) != 0)
95 fail++;
96 xfree(p);
97
98 /* pubkey */
99 pkalg = buffer_get_string(&b, NULL);
100 pkblob = buffer_get_string(&b, &blen);
101
102 pktype = key_type_from_name(pkalg);
103 if (pktype == KEY_UNSPEC)
104 fail++;
105 else if ((key = key_from_blob(pkblob, blen)) == NULL)
106 fail++;
107 else if (key->type != pktype)
108 fail++;
109 xfree(pkalg);
110 xfree(pkblob);
111
112 /* client host name, handle trailing dot */
113 p = buffer_get_string(&b, &len);
114 debug2("valid_request: check expect chost %s got %s", host, p);
115 if (strlen(host) != len - 1)
116 fail++;
117 else if (p[len - 1] != '.')
118 fail++;
119 else if (strncasecmp(host, p, len - 1) != 0)
120 fail++;
121 xfree(p);
122
123 /* local user */
124 p = buffer_get_string(&b, NULL);
125
126 if (strcmp(pw->pw_name, p) != 0)
127 fail++;
128 xfree(p);
129
130 /* end of message */
131 if (buffer_len(&b) != 0)
132 fail++;
133 buffer_free(&b);
134
135 debug3("valid_request: fail %d", fail);
136
137 if (fail && key != NULL)
138 key_free(key);
139 else
140 *ret = key;
141
142 return (fail ? -1 : 0);
143 }
144
145 int
main(void)146 main(void)
147 {
148 Buffer b;
149 Options options;
150 Key *keys[2], *key;
151 struct passwd *pw;
152 int key_fd[2], i, found, version = 2, fd;
153 u_char *signature, *data;
154 char *host;
155 u_int slen, dlen;
156
157 /* Ensure that stdin and stdout are connected */
158 if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2)
159 exit(1);
160 /* Leave /dev/null fd iff it is attached to stderr */
161 if (fd > 2)
162 close(fd);
163
164 key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);
165 key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);
166
167 original_real_uid = getuid(); /* XXX readconf.c needs this */
168 if ((pw = getpwuid(original_real_uid)) == NULL)
169 fatal("getpwuid failed");
170 pw = pwcopy(pw);
171
172 permanently_set_uid(pw);
173
174 #ifdef DEBUG_SSH_KEYSIGN
175 log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0);
176 #endif
177
178 /* verify that ssh-keysign is enabled by the admin */
179 initialize_options(&options);
180 (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0);
181 fill_default_options(&options, pw);
182 if (options.enable_ssh_keysign != 1)
183 fatal("ssh-keysign not enabled in %s",
184 _PATH_HOST_CONFIG_FILE);
185
186 if (key_fd[0] == -1 && key_fd[1] == -1)
187 fatal("could not open any host key");
188
189 SSLeay_add_all_algorithms();
190 (void)arc4random();
191
192 found = 0;
193 for (i = 0; i < 2; i++) {
194 keys[i] = NULL;
195 if (key_fd[i] == -1)
196 continue;
197 keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC,
198 NULL, NULL);
199 close(key_fd[i]);
200 if (keys[i] != NULL)
201 found = 1;
202 }
203 if (!found)
204 fatal("no hostkey found");
205
206 buffer_init(&b);
207 if (ssh_msg_recv(STDIN_FILENO, &b) < 0)
208 fatal("ssh_msg_recv failed");
209 if (buffer_get_char(&b) != version)
210 fatal("bad version");
211 fd = buffer_get_int(&b);
212 if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO))
213 fatal("bad fd");
214 if ((host = get_local_name(fd)) == NULL)
215 fatal("cannot get sockname for fd");
216
217 data = buffer_get_string(&b, &dlen);
218 if (valid_request(pw, host, &key, data, dlen) < 0)
219 fatal("not a valid request");
220 xfree(host);
221
222 found = 0;
223 for (i = 0; i < 2; i++) {
224 if (keys[i] != NULL &&
225 key_equal(key, keys[i])) {
226 found = 1;
227 break;
228 }
229 }
230 if (!found)
231 fatal("no matching hostkey found");
232
233 if (key_sign(keys[i], &signature, &slen, data, dlen) != 0)
234 fatal("key_sign failed");
235 xfree(data);
236
237 /* send reply */
238 buffer_clear(&b);
239 buffer_put_string(&b, signature, slen);
240 if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1)
241 fatal("ssh_msg_send failed");
242
243 return (0);
244 }
245