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b1842393 | 1 | /* $OpenBSD: ssh-keysign.c,v 1.24 2006/07/06 16:03:53 stevesk Exp $ */ |
39c00dc2 | 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 | #include "includes.h" | |
a75f5360 | 26 | |
b5b88c19 | 27 | #ifdef HAVE_PATHS_H |
a75f5360 | 28 | #include <paths.h> |
b5b88c19 | 29 | #endif |
b1842393 | 30 | #include <pwd.h> |
39c00dc2 | 31 | |
32 | #include <openssl/evp.h> | |
261189cc | 33 | #include <openssl/rand.h> |
34 | #include <openssl/rsa.h> | |
39c00dc2 | 35 | |
36 | #include "log.h" | |
37 | #include "key.h" | |
60cd0a97 | 38 | #include "ssh.h" |
39c00dc2 | 39 | #include "ssh2.h" |
40 | #include "misc.h" | |
41 | #include "xmalloc.h" | |
42 | #include "buffer.h" | |
43 | #include "bufaux.h" | |
44 | #include "authfile.h" | |
45 | #include "msg.h" | |
46 | #include "canohost.h" | |
47 | #include "pathnames.h" | |
60cd0a97 | 48 | #include "readconf.h" |
6213295d | 49 | #include "uidswap.h" |
60cd0a97 | 50 | |
f811e52a | 51 | /* XXX readconf.c needs these */ |
52 | uid_t original_real_uid; | |
39c00dc2 | 53 | |
95d5ebf7 | 54 | extern char *__progname; |
95d5ebf7 | 55 | |
39c00dc2 | 56 | static int |
57 | valid_request(struct passwd *pw, char *host, Key **ret, u_char *data, | |
58 | u_int datalen) | |
59 | { | |
60 | Buffer b; | |
16f1b5ca | 61 | Key *key = NULL; |
39c00dc2 | 62 | u_char *pkblob; |
63 | u_int blen, len; | |
64 | char *pkalg, *p; | |
65 | int pktype, fail; | |
66 | ||
67 | fail = 0; | |
68 | ||
69 | buffer_init(&b); | |
70 | buffer_append(&b, data, datalen); | |
7203d6bb | 71 | |
5fe9ca7d | 72 | /* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */ |
1f143cf2 | 73 | p = buffer_get_string(&b, &len); |
5fe9ca7d | 74 | if (len != 20 && len != 32) |
1f143cf2 | 75 | fail++; |
76 | xfree(p); | |
77 | ||
39c00dc2 | 78 | if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST) |
79 | fail++; | |
80 | ||
81 | /* server user */ | |
82 | buffer_skip_string(&b); | |
83 | ||
84 | /* service */ | |
85 | p = buffer_get_string(&b, NULL); | |
86 | if (strcmp("ssh-connection", p) != 0) | |
87 | fail++; | |
88 | xfree(p); | |
89 | ||
90 | /* method */ | |
91 | p = buffer_get_string(&b, NULL); | |
92 | if (strcmp("hostbased", p) != 0) | |
93 | fail++; | |
94 | xfree(p); | |
95 | ||
96 | /* pubkey */ | |
97 | pkalg = buffer_get_string(&b, NULL); | |
98 | pkblob = buffer_get_string(&b, &blen); | |
99 | ||
100 | pktype = key_type_from_name(pkalg); | |
101 | if (pktype == KEY_UNSPEC) | |
102 | fail++; | |
103 | else if ((key = key_from_blob(pkblob, blen)) == NULL) | |
104 | fail++; | |
105 | else if (key->type != pktype) | |
106 | fail++; | |
107 | xfree(pkalg); | |
108 | xfree(pkblob); | |
109 | ||
110 | /* client host name, handle trailing dot */ | |
111 | p = buffer_get_string(&b, &len); | |
112 | debug2("valid_request: check expect chost %s got %s", host, p); | |
113 | if (strlen(host) != len - 1) | |
114 | fail++; | |
115 | else if (p[len - 1] != '.') | |
7203d6bb | 116 | fail++; |
39c00dc2 | 117 | else if (strncasecmp(host, p, len - 1) != 0) |
7203d6bb | 118 | fail++; |
39c00dc2 | 119 | xfree(p); |
120 | ||
121 | /* local user */ | |
122 | p = buffer_get_string(&b, NULL); | |
123 | ||
124 | if (strcmp(pw->pw_name, p) != 0) | |
125 | fail++; | |
126 | xfree(p); | |
127 | ||
128 | /* end of message */ | |
129 | if (buffer_len(&b) != 0) | |
130 | fail++; | |
43f7a4b8 | 131 | buffer_free(&b); |
39c00dc2 | 132 | |
133 | debug3("valid_request: fail %d", fail); | |
134 | ||
135 | if (fail && key != NULL) | |
136 | key_free(key); | |
137 | else | |
138 | *ret = key; | |
139 | ||
140 | return (fail ? -1 : 0); | |
141 | } | |
142 | ||
143 | int | |
144 | main(int argc, char **argv) | |
145 | { | |
146 | Buffer b; | |
60cd0a97 | 147 | Options options; |
39c00dc2 | 148 | Key *keys[2], *key; |
149 | struct passwd *pw; | |
150 | int key_fd[2], i, found, version = 2, fd; | |
151 | u_char *signature, *data; | |
152 | char *host; | |
153 | u_int slen, dlen; | |
261189cc | 154 | u_int32_t rnd[256]; |
39c00dc2 | 155 | |
fd6168c1 | 156 | /* Ensure that stdin and stdout are connected */ |
157 | if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2) | |
158 | exit(1); | |
159 | /* Leave /dev/null fd iff it is attached to stderr */ | |
160 | if (fd > 2) | |
161 | close(fd); | |
162 | ||
39c00dc2 | 163 | key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); |
164 | key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); | |
165 | ||
baab9e74 | 166 | original_real_uid = getuid(); /* XXX readconf.c needs this */ |
167 | if ((pw = getpwuid(original_real_uid)) == NULL) | |
6213295d | 168 | fatal("getpwuid failed"); |
169 | pw = pwcopy(pw); | |
170 | ||
171 | permanently_set_uid(pw); | |
39c00dc2 | 172 | |
875ec275 | 173 | init_rng(); |
174 | seed_rng(); | |
175 | arc4random_stir(); | |
04eb391d | 176 | |
39c00dc2 | 177 | #ifdef DEBUG_SSH_KEYSIGN |
178 | log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); | |
7203d6bb | 179 | #endif |
39c00dc2 | 180 | |
60cd0a97 | 181 | /* verify that ssh-keysign is enabled by the admin */ |
60cd0a97 | 182 | initialize_options(&options); |
9f6cab4b | 183 | (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0); |
60cd0a97 | 184 | fill_default_options(&options); |
cc46e2ee | 185 | if (options.enable_ssh_keysign != 1) |
186 | fatal("ssh-keysign not enabled in %s", | |
60cd0a97 | 187 | _PATH_HOST_CONFIG_FILE); |
188 | ||
39c00dc2 | 189 | if (key_fd[0] == -1 && key_fd[1] == -1) |
190 | fatal("could not open any host key"); | |
191 | ||
39c00dc2 | 192 | SSLeay_add_all_algorithms(); |
261189cc | 193 | for (i = 0; i < 256; i++) |
194 | rnd[i] = arc4random(); | |
195 | RAND_seed(rnd, sizeof(rnd)); | |
39c00dc2 | 196 | |
197 | found = 0; | |
198 | for (i = 0; i < 2; i++) { | |
199 | keys[i] = NULL; | |
200 | if (key_fd[i] == -1) | |
201 | continue; | |
202 | keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC, | |
203 | NULL, NULL); | |
204 | close(key_fd[i]); | |
205 | if (keys[i] != NULL) | |
206 | found = 1; | |
207 | } | |
208 | if (!found) | |
209 | fatal("no hostkey found"); | |
210 | ||
211 | buffer_init(&b); | |
e987fdbe | 212 | if (ssh_msg_recv(STDIN_FILENO, &b) < 0) |
213 | fatal("ssh_msg_recv failed"); | |
39c00dc2 | 214 | if (buffer_get_char(&b) != version) |
215 | fatal("bad version"); | |
216 | fd = buffer_get_int(&b); | |
217 | if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO)) | |
218 | fatal("bad fd"); | |
219 | if ((host = get_local_name(fd)) == NULL) | |
220 | fatal("cannot get sockname for fd"); | |
7203d6bb | 221 | |
39c00dc2 | 222 | data = buffer_get_string(&b, &dlen); |
223 | if (valid_request(pw, host, &key, data, dlen) < 0) | |
224 | fatal("not a valid request"); | |
39c00dc2 | 225 | xfree(host); |
226 | ||
227 | found = 0; | |
228 | for (i = 0; i < 2; i++) { | |
229 | if (keys[i] != NULL && | |
230 | key_equal(key, keys[i])) { | |
231 | found = 1; | |
232 | break; | |
233 | } | |
234 | } | |
235 | if (!found) | |
236 | fatal("no matching hostkey found"); | |
237 | ||
238 | if (key_sign(keys[i], &signature, &slen, data, dlen) != 0) | |
239 | fatal("key_sign failed"); | |
20e79e98 | 240 | xfree(data); |
7203d6bb | 241 | |
39c00dc2 | 242 | /* send reply */ |
243 | buffer_clear(&b); | |
244 | buffer_put_string(&b, signature, slen); | |
d3cbe6f8 | 245 | if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1) |
246 | fatal("ssh_msg_send failed"); | |
39c00dc2 | 247 | |
248 | return (0); | |
249 | } |