1 /*
2 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
3 * Use is subject to license terms.
4 */
5 /*
6 * Copyright (c) 2002 Markus Friedl. All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28 #include "includes.h"
29 RCSID("$OpenBSD: ssh-keysign.c,v 1.7 2002/07/03 14:21:05 markus Exp $");
30
31 #pragma ident "%Z%%M% %I% %E% SMI"
32
33 #include <unistd.h>
34
35 #include <openssl/evp.h>
36 #include <openssl/rand.h>
37 #include <openssl/rsa.h>
38
39 #include "log.h"
40 #include "key.h"
41 #include "ssh.h"
42 #include "ssh2.h"
43 #include "misc.h"
44 #include "xmalloc.h"
45 #include "buffer.h"
46 #include "bufaux.h"
47 #include "authfile.h"
48 #include "msg.h"
49 #include "canohost.h"
50 #include "pathnames.h"
51 #include "readconf.h"
52
53 uid_t original_real_uid; /* XXX readconf.c needs this */
54
55 #ifdef HAVE___PROGNAME
56 extern char *__progname;
57 #else
58 #ifndef lint
59 char *__progname;
60 #endif /* lint */
61 #endif
62
63 static int
64 valid_request(struct passwd *pw, char *host, Key **ret, u_char *data,
65 u_int datalen)
66 {
67 Buffer b;
68 Key *key;
69 u_char *pkblob;
70 u_int blen, len;
71 char *pkalg, *p;
72 int pktype, fail;
73
74 fail = 0;
75
76 buffer_init(&b);
77 buffer_append(&b, data, datalen);
78
79 /* session id, currently limited to SHA1 (20 bytes) */
80 p = buffer_get_string(&b, &len);
81 if (len != 20)
82 fail++;
83 xfree(p);
84
85 if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST)
86 fail++;
87
88 /* server user */
89 buffer_skip_string(&b);
90
91 /* service */
92 p = buffer_get_string(&b, NULL);
93 if (strcmp("ssh-connection", p) != 0)
94 fail++;
95 xfree(p);
96
97 /* method */
98 p = buffer_get_string(&b, NULL);
99 if (strcmp("hostbased", p) != 0)
100 fail++;
101 xfree(p);
102
103 /* pubkey */
104 pkalg = buffer_get_string(&b, NULL);
105 pkblob = buffer_get_string(&b, &blen);
106
107 pktype = key_type_from_name(pkalg);
108 if (pktype == KEY_UNSPEC)
109 fail++;
110 else if ((key = key_from_blob(pkblob, blen)) == NULL)
111 fail++;
112 else if (key->type != pktype)
113 fail++;
114 xfree(pkalg);
115 xfree(pkblob);
116
117 /* client host name, handle trailing dot */
118 p = buffer_get_string(&b, &len);
119 debug2("valid_request: check expect chost %s got %s", host, p);
120 if (strlen(host) != len - 1)
121 fail++;
122 else if (p[len - 1] != '.')
123 fail++;
124 else if (strncasecmp(host, p, len - 1) != 0)
125 fail++;
126 xfree(p);
127
128 /* local user */
129 p = buffer_get_string(&b, NULL);
130
131 if (strcmp(pw->pw_name, p) != 0)
132 fail++;
133 xfree(p);
134
135 /* end of message */
136 if (buffer_len(&b) != 0)
137 fail++;
138
139 debug3("valid_request: fail %d", fail);
140
141 if (fail && key != NULL)
142 key_free(key);
143 else
144 *ret = key;
145
146 return (fail ? -1 : 0);
147 }
148
149 int
150 main(int argc, char **argv)
151 {
152 Buffer b;
153 Options options;
154 Key *keys[2], *key;
155 struct passwd *pw;
156 int key_fd[2], i, found, version = 2, fd;
157 u_char *signature, *data;
158 char *host;
159 u_int slen, dlen;
160 u_int32_t rnd[256];
161
162 /*
163 * Since these two open()s are all that's done here before
164 * dropping privileges with setreuid(), and since having been
165 * privileged protects ssh-keysign from core dumps and tracing,
166 * there's no need to use Least Privilege interfaces like
167 * setppriv(2).
168 */
169 key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);
170 key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);
171
172 (void) setreuid(getuid(), getuid());
173
174 (void) g11n_setlocale(LC_ALL, "");
175
176 init_rng();
177 seed_rng();
178 arc4random_stir();
179
180 #ifdef DEBUG_SSH_KEYSIGN
181 log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0);
182 #endif
183
184 /* verify that ssh-keysign is enabled by the admin */
185 original_real_uid = getuid(); /* XXX readconf.c needs this */
186 initialize_options(&options);
187 (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options);
188 fill_default_options(&options);
189 if (options.hostbased_authentication != 1)
190 fatal("Hostbased authentication not enabled in %s",
191 _PATH_HOST_CONFIG_FILE);
192
193 if (key_fd[0] == -1 && key_fd[1] == -1)
194 fatal("could not open any host key");
195
196 if ((pw = getpwuid(getuid())) == NULL)
197 fatal("getpwuid failed");
198 pw = pwcopy(pw);
199
200 SSLeay_add_all_algorithms();
201 for (i = 0; i < 256; i++)
202 rnd[i] = arc4random();
203 RAND_seed(rnd, sizeof(rnd));
204
205 found = 0;
206 for (i = 0; i < 2; i++) {
207 keys[i] = NULL;
208 if (key_fd[i] == -1)
209 continue;
210 keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC,
211 NULL, NULL);
212 (void) close(key_fd[i]);
213 if (keys[i] != NULL && keys[i]->type == KEY_RSA) {
214 if (RSA_blinding_on(keys[i]->rsa, NULL) != 1) {
215 error("RSA_blinding_on failed");
216 key_free(keys[i]);
217 keys[i] = NULL;
218 }
219 }
220 if (keys[i] != NULL)
221 found = 1;
222 }
223 if (!found)
224 fatal("no hostkey found");
225
226 buffer_init(&b);
227 if (ssh_msg_recv(STDIN_FILENO, &b) < 0)
228 fatal("ssh_msg_recv failed");
229 if (buffer_get_char(&b) != version)
230 fatal("bad version");
231 fd = buffer_get_int(&b);
232 if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO))
233 fatal("bad fd");
234 if ((host = get_local_name(fd)) == NULL)
235 fatal("cannot get sockname for fd");
236
237 data = buffer_get_string(&b, &dlen);
238 if (valid_request(pw, host, &key, data, dlen) < 0)
239 fatal("not a valid request");
240 xfree(host);
241
242 found = 0;
243 for (i = 0; i < 2; i++) {
244 if (keys[i] != NULL &&
245 key_equal(key, keys[i])) {
246 found = 1;
247 break;
248 }
249 }
250 if (!found)
251 fatal("no matching hostkey found");
252
253 if (key_sign(keys[i], &signature, &slen, data, dlen) != 0)
254 fatal("key_sign failed");
255 xfree(data);
256
257 /* send reply */
258 buffer_clear(&b);
259 buffer_put_string(&b, signature, slen);
260 ssh_msg_send(STDOUT_FILENO, version, &b);
261
262 return (0);
263 }