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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"
Damien Miller703ced52003-04-09 20:50:26 +100025RCSID("$OpenBSD: ssh-keysign.c,v 1.11 2003/04/02 14:36:26 markus 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"
44
45uid_t original_real_uid; /* XXX readconf.c needs this */
Ben Lindstrom1bad2562002-06-06 19:57:33 +000046
Ben Lindstrom35453522002-06-07 14:37:00 +000047#ifdef HAVE___PROGNAME
48extern char *__progname;
49#else
50char *__progname;
51#endif
52
Ben Lindstrom1bad2562002-06-06 19:57:33 +000053static int
54valid_request(struct passwd *pw, char *host, Key **ret, u_char *data,
55 u_int datalen)
56{
57 Buffer b;
Damien Miller703ced52003-04-09 20:50:26 +100058 Key *key = NULL;
Ben Lindstrom1bad2562002-06-06 19:57:33 +000059 u_char *pkblob;
60 u_int blen, len;
61 char *pkalg, *p;
62 int pktype, fail;
63
64 fail = 0;
65
66 buffer_init(&b);
67 buffer_append(&b, data, datalen);
Ben Lindstromcb72e4f2002-06-21 00:41:51 +000068
Ben Lindstroma2071572002-06-09 20:01:48 +000069 /* session id, currently limited to SHA1 (20 bytes) */
70 p = buffer_get_string(&b, &len);
71 if (len != 20)
72 fail++;
73 xfree(p);
74
Ben Lindstrom1bad2562002-06-06 19:57:33 +000075 if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST)
76 fail++;
77
78 /* server user */
79 buffer_skip_string(&b);
80
81 /* service */
82 p = buffer_get_string(&b, NULL);
83 if (strcmp("ssh-connection", p) != 0)
84 fail++;
85 xfree(p);
86
87 /* method */
88 p = buffer_get_string(&b, NULL);
89 if (strcmp("hostbased", p) != 0)
90 fail++;
91 xfree(p);
92
93 /* pubkey */
94 pkalg = buffer_get_string(&b, NULL);
95 pkblob = buffer_get_string(&b, &blen);
96
97 pktype = key_type_from_name(pkalg);
98 if (pktype == KEY_UNSPEC)
99 fail++;
100 else if ((key = key_from_blob(pkblob, blen)) == NULL)
101 fail++;
102 else if (key->type != pktype)
103 fail++;
104 xfree(pkalg);
105 xfree(pkblob);
106
107 /* client host name, handle trailing dot */
108 p = buffer_get_string(&b, &len);
109 debug2("valid_request: check expect chost %s got %s", host, p);
110 if (strlen(host) != len - 1)
111 fail++;
112 else if (p[len - 1] != '.')
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000113 fail++;
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000114 else if (strncasecmp(host, p, len - 1) != 0)
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000115 fail++;
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000116 xfree(p);
117
118 /* local user */
119 p = buffer_get_string(&b, NULL);
120
121 if (strcmp(pw->pw_name, p) != 0)
122 fail++;
123 xfree(p);
124
125 /* end of message */
126 if (buffer_len(&b) != 0)
127 fail++;
128
129 debug3("valid_request: fail %d", fail);
130
131 if (fail && key != NULL)
132 key_free(key);
133 else
134 *ret = key;
135
136 return (fail ? -1 : 0);
137}
138
139int
140main(int argc, char **argv)
141{
142 Buffer b;
Ben Lindstrom5d35a2f2002-07-04 00:19:40 +0000143 Options options;
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000144 Key *keys[2], *key;
145 struct passwd *pw;
146 int key_fd[2], i, found, version = 2, fd;
147 u_char *signature, *data;
148 char *host;
149 u_int slen, dlen;
Ben Lindstrom43ce2c82002-07-04 00:17:33 +0000150 u_int32_t rnd[256];
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000151
152 key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);
153 key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);
154
155 seteuid(getuid());
156 setuid(getuid());
157
Ben Lindstrom5a6abda2002-06-09 19:41:48 +0000158 init_rng();
159 seed_rng();
160 arc4random_stir();
Ben Lindstromdb41d232002-06-07 03:11:38 +0000161
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000162#ifdef DEBUG_SSH_KEYSIGN
163 log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0);
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000164#endif
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000165
Ben Lindstrom5d35a2f2002-07-04 00:19:40 +0000166 /* verify that ssh-keysign is enabled by the admin */
167 original_real_uid = getuid(); /* XXX readconf.c needs this */
168 initialize_options(&options);
169 (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options);
170 fill_default_options(&options);
Ben Lindstromb6df73b2002-11-09 15:52:31 +0000171 if (options.enable_ssh_keysign != 1)
172 fatal("ssh-keysign not enabled in %s",
Ben Lindstrom5d35a2f2002-07-04 00:19:40 +0000173 _PATH_HOST_CONFIG_FILE);
174
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000175 if (key_fd[0] == -1 && key_fd[1] == -1)
176 fatal("could not open any host key");
177
178 if ((pw = getpwuid(getuid())) == NULL)
179 fatal("getpwuid failed");
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000180 pw = pwcopy(pw);
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000181
182 SSLeay_add_all_algorithms();
Ben Lindstrom43ce2c82002-07-04 00:17:33 +0000183 for (i = 0; i < 256; i++)
184 rnd[i] = arc4random();
185 RAND_seed(rnd, sizeof(rnd));
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000186
187 found = 0;
188 for (i = 0; i < 2; i++) {
189 keys[i] = NULL;
190 if (key_fd[i] == -1)
191 continue;
192 keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC,
193 NULL, NULL);
194 close(key_fd[i]);
195 if (keys[i] != NULL)
196 found = 1;
197 }
198 if (!found)
199 fatal("no hostkey found");
200
201 buffer_init(&b);
Damien Miller901119b2002-10-04 11:10:04 +1000202 if (ssh_msg_recv(STDIN_FILENO, &b) < 0)
203 fatal("ssh_msg_recv failed");
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000204 if (buffer_get_char(&b) != version)
205 fatal("bad version");
206 fd = buffer_get_int(&b);
207 if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO))
208 fatal("bad fd");
209 if ((host = get_local_name(fd)) == NULL)
210 fatal("cannot get sockname for fd");
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000211
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000212 data = buffer_get_string(&b, &dlen);
213 if (valid_request(pw, host, &key, data, dlen) < 0)
214 fatal("not a valid request");
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000215 xfree(host);
216
217 found = 0;
218 for (i = 0; i < 2; i++) {
219 if (keys[i] != NULL &&
220 key_equal(key, keys[i])) {
221 found = 1;
222 break;
223 }
224 }
225 if (!found)
226 fatal("no matching hostkey found");
227
228 if (key_sign(keys[i], &signature, &slen, data, dlen) != 0)
229 fatal("key_sign failed");
Ben Lindstromfe275982002-06-27 00:25:07 +0000230 xfree(data);
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000231
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000232 /* send reply */
233 buffer_clear(&b);
234 buffer_put_string(&b, signature, slen);
Damien Miller901119b2002-10-04 11:10:04 +1000235 ssh_msg_send(STDOUT_FILENO, version, &b);
Ben Lindstrom1bad2562002-06-06 19:57:33 +0000236
237 return (0);
238}