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Ben Lindstrom1bad2562002-06-06 19:57:33 +00001/*
2 * Copyright (c) 2002 Markus Friedl. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24#include "includes.h"
Darren Tucker34620d62004-08-29 16:32:59 +100025RCSID("$OpenBSD: ssh-keysign.c,v 1.18 2004/08/23 14:29:23 dtucker Exp $");
Ben Lindstrom1bad2562002-06-06 19:57:33 +000026
27#include <openssl/evp.h>
Ben Lindstrom43ce2c82002-07-04 00:17:33 +000028#include <openssl/rand.h>
29#include <openssl/rsa.h>
Ben Lindstrom1bad2562002-06-06 19:57:33 +000030
31#include "log.h"
32#include "key.h"
Ben Lindstrom5d35a2f2002-07-04 00:19:40 +000033#include "ssh.h"
Ben Lindstrom1bad2562002-06-06 19:57:33 +000034#include "ssh2.h"
35#include "misc.h"
36#include "xmalloc.h"
37#include "buffer.h"
38#include "bufaux.h"
39#include "authfile.h"
40#include "msg.h"
41#include "canohost.h"
42#include "pathnames.h"
Ben Lindstrom5d35a2f2002-07-04 00:19:40 +000043#include "readconf.h"
Darren Tucker25f60a72004-08-15 17:23:34 +100044#include "uidswap.h"
Ben Lindstrom5d35a2f2002-07-04 00:19:40 +000045
Damien Miller20a8f972003-05-18 20:50:30 +100046/* XXX readconf.c needs these */
47uid_t original_real_uid;
Ben Lindstrom1bad2562002-06-06 19:57:33 +000048
Ben Lindstrom35453522002-06-07 14:37:00 +000049extern char *__progname;
Ben Lindstrom35453522002-06-07 14:37:00 +000050
Ben Lindstrom1bad2562002-06-06 19:57:33 +000051static int
52valid_request(struct passwd *pw, char *host, Key **ret, u_char *data,
53 u_int datalen)
54{
55 Buffer b;
Damien Miller703ced52003-04-09 20:50:26 +100056 Key *key = NULL;
Ben Lindstrom1bad2562002-06-06 19:57:33 +000057 u_char *pkblob;
58 u_int blen, len;
59 char *pkalg, *p;
60 int pktype, fail;
61
62 fail = 0;
63
64 buffer_init(&b);
65 buffer_append(&b, data, datalen);
Ben Lindstromcb72e4f2002-06-21 00:41:51 +000066
Ben Lindstroma2071572002-06-09 20:01:48 +000067 /* session id, currently limited to SHA1 (20 bytes) */
68 p = buffer_get_string(&b, &len);
69 if (len != 20)
70 fail++;
71 xfree(p);
72
Ben Lindstrom1bad2562002-06-06 19:57:33 +000073 if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST)
74 fail++;
75
76 /* server user */
77 buffer_skip_string(&b);
78
79 /* service */
80 p = buffer_get_string(&b, NULL);
81 if (strcmp("ssh-connection", p) != 0)
82 fail++;
83 xfree(p);
84
85 /* method */
86 p = buffer_get_string(&b, NULL);
87 if (strcmp("hostbased", p) != 0)
88 fail++;
89 xfree(p);
90
91 /* pubkey */
92 pkalg = buffer_get_string(&b, NULL);
93 pkblob = buffer_get_string(&b, &blen);
94
95 pktype = key_type_from_name(pkalg);
96 if (pktype == KEY_UNSPEC)
97 fail++;
98 else if ((key = key_from_blob(pkblob, blen)) == NULL)
99 fail++;
100 else if (key->type != pktype)
101 fail++;
102 xfree(pkalg);
103 xfree(pkblob);
104
105 /* client host name, handle trailing dot */
106 p = buffer_get_string(&b, &len);
107 debug2("valid_request: check expect chost %s got %s", host, p);
108 if (strlen(host) != len - 1)
109 fail++;
110 else if (p[len - 1] != '.')
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000111 fail++;
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000112 else if (strncasecmp(host, p, len - 1) != 0)
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000113 fail++;
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000114 xfree(p);
115
116 /* local user */
117 p = buffer_get_string(&b, NULL);
118
119 if (strcmp(pw->pw_name, p) != 0)
120 fail++;
121 xfree(p);
122
123 /* end of message */
124 if (buffer_len(&b) != 0)
125 fail++;
Damien Millerfb1310e2004-01-21 11:02:50 +1100126 buffer_free(&b);
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000127
128 debug3("valid_request: fail %d", fail);
129
130 if (fail && key != NULL)
131 key_free(key);
132 else
133 *ret = key;
134
135 return (fail ? -1 : 0);
136}
137
138int
139main(int argc, char **argv)
140{
141 Buffer b;
Ben Lindstrom5d35a2f2002-07-04 00:19:40 +0000142 Options options;
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000143 Key *keys[2], *key;
144 struct passwd *pw;
145 int key_fd[2], i, found, version = 2, fd;
146 u_char *signature, *data;
147 char *host;
148 u_int slen, dlen;
Ben Lindstrom43ce2c82002-07-04 00:17:33 +0000149 u_int32_t rnd[256];
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000150
151 key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);
152 key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);
153
Darren Tucker34620d62004-08-29 16:32:59 +1000154 original_real_uid = getuid(); /* XXX readconf.c needs this */
155 if ((pw = getpwuid(original_real_uid)) == NULL)
Darren Tucker25f60a72004-08-15 17:23:34 +1000156 fatal("getpwuid failed");
157 pw = pwcopy(pw);
158
159 permanently_set_uid(pw);
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000160
Ben Lindstrom5a6abda2002-06-09 19:41:48 +0000161 init_rng();
162 seed_rng();
163 arc4random_stir();
Ben Lindstromdb41d232002-06-07 03:11:38 +0000164
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000165#ifdef DEBUG_SSH_KEYSIGN
166 log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0);
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000167#endif
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000168
Ben Lindstrom5d35a2f2002-07-04 00:19:40 +0000169 /* verify that ssh-keysign is enabled by the admin */
Ben Lindstrom5d35a2f2002-07-04 00:19:40 +0000170 initialize_options(&options);
Damien Miller57a44762004-04-20 20:11:57 +1000171 (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0);
Ben Lindstrom5d35a2f2002-07-04 00:19:40 +0000172 fill_default_options(&options);
Ben Lindstromb6df73b2002-11-09 15:52:31 +0000173 if (options.enable_ssh_keysign != 1)
174 fatal("ssh-keysign not enabled in %s",
Ben Lindstrom5d35a2f2002-07-04 00:19:40 +0000175 _PATH_HOST_CONFIG_FILE);
176
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000177 if (key_fd[0] == -1 && key_fd[1] == -1)
178 fatal("could not open any host key");
179
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000180 SSLeay_add_all_algorithms();
Ben Lindstrom43ce2c82002-07-04 00:17:33 +0000181 for (i = 0; i < 256; i++)
182 rnd[i] = arc4random();
183 RAND_seed(rnd, sizeof(rnd));
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000184
185 found = 0;
186 for (i = 0; i < 2; i++) {
187 keys[i] = NULL;
188 if (key_fd[i] == -1)
189 continue;
190 keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC,
191 NULL, NULL);
192 close(key_fd[i]);
193 if (keys[i] != NULL)
194 found = 1;
195 }
196 if (!found)
197 fatal("no hostkey found");
198
199 buffer_init(&b);
Damien Miller901119b2002-10-04 11:10:04 +1000200 if (ssh_msg_recv(STDIN_FILENO, &b) < 0)
201 fatal("ssh_msg_recv failed");
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000202 if (buffer_get_char(&b) != version)
203 fatal("bad version");
204 fd = buffer_get_int(&b);
205 if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO))
206 fatal("bad fd");
207 if ((host = get_local_name(fd)) == NULL)
208 fatal("cannot get sockname for fd");
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000209
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000210 data = buffer_get_string(&b, &dlen);
211 if (valid_request(pw, host, &key, data, dlen) < 0)
212 fatal("not a valid request");
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000213 xfree(host);
214
215 found = 0;
216 for (i = 0; i < 2; i++) {
217 if (keys[i] != NULL &&
218 key_equal(key, keys[i])) {
219 found = 1;
220 break;
221 }
222 }
223 if (!found)
224 fatal("no matching hostkey found");
225
226 if (key_sign(keys[i], &signature, &slen, data, dlen) != 0)
227 fatal("key_sign failed");
Ben Lindstromfe275982002-06-27 00:25:07 +0000228 xfree(data);
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000229
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000230 /* send reply */
231 buffer_clear(&b);
232 buffer_put_string(&b, signature, slen);
Damien Miller51bf11f2003-11-17 21:20:47 +1100233 if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1)
234 fatal("ssh_msg_send failed");
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000235
236 return (0);
237}