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5fe9ca7d | 1 | /* $OpenBSD: ssh-keysign.c,v 1.23 2006/04/02 08:34:52 dtucker 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 |
39c00dc2 | 30 | |
31 | #include <openssl/evp.h> | |
261189cc | 32 | #include <openssl/rand.h> |
33 | #include <openssl/rsa.h> | |
39c00dc2 | 34 | |
35 | #include "log.h" | |
36 | #include "key.h" | |
60cd0a97 | 37 | #include "ssh.h" |
39c00dc2 | 38 | #include "ssh2.h" |
39 | #include "misc.h" | |
40 | #include "xmalloc.h" | |
41 | #include "buffer.h" | |
42 | #include "bufaux.h" | |
43 | #include "authfile.h" | |
44 | #include "msg.h" | |
45 | #include "canohost.h" | |
46 | #include "pathnames.h" | |
60cd0a97 | 47 | #include "readconf.h" |
6213295d | 48 | #include "uidswap.h" |
60cd0a97 | 49 | |
f811e52a | 50 | /* XXX readconf.c needs these */ |
51 | uid_t original_real_uid; | |
39c00dc2 | 52 | |
95d5ebf7 | 53 | extern char *__progname; |
95d5ebf7 | 54 | |
39c00dc2 | 55 | static int |
56 | valid_request(struct passwd *pw, char *host, Key **ret, u_char *data, | |
57 | u_int datalen) | |
58 | { | |
59 | Buffer b; | |
16f1b5ca | 60 | Key *key = NULL; |
39c00dc2 | 61 | u_char *pkblob; |
62 | u_int blen, len; | |
63 | char *pkalg, *p; | |
64 | int pktype, fail; | |
65 | ||
66 | fail = 0; | |
67 | ||
68 | buffer_init(&b); | |
69 | buffer_append(&b, data, datalen); | |
7203d6bb | 70 | |
5fe9ca7d | 71 | /* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */ |
1f143cf2 | 72 | p = buffer_get_string(&b, &len); |
5fe9ca7d | 73 | if (len != 20 && len != 32) |
1f143cf2 | 74 | fail++; |
75 | xfree(p); | |
76 | ||
39c00dc2 | 77 | if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST) |
78 | fail++; | |
79 | ||
80 | /* server user */ | |
81 | buffer_skip_string(&b); | |
82 | ||
83 | /* service */ | |
84 | p = buffer_get_string(&b, NULL); | |
85 | if (strcmp("ssh-connection", p) != 0) | |
86 | fail++; | |
87 | xfree(p); | |
88 | ||
89 | /* method */ | |
90 | p = buffer_get_string(&b, NULL); | |
91 | if (strcmp("hostbased", p) != 0) | |
92 | fail++; | |
93 | xfree(p); | |
94 | ||
95 | /* pubkey */ | |
96 | pkalg = buffer_get_string(&b, NULL); | |
97 | pkblob = buffer_get_string(&b, &blen); | |
98 | ||
99 | pktype = key_type_from_name(pkalg); | |
100 | if (pktype == KEY_UNSPEC) | |
101 | fail++; | |
102 | else if ((key = key_from_blob(pkblob, blen)) == NULL) | |
103 | fail++; | |
104 | else if (key->type != pktype) | |
105 | fail++; | |
106 | xfree(pkalg); | |
107 | xfree(pkblob); | |
108 | ||
109 | /* client host name, handle trailing dot */ | |
110 | p = buffer_get_string(&b, &len); | |
111 | debug2("valid_request: check expect chost %s got %s", host, p); | |
112 | if (strlen(host) != len - 1) | |
113 | fail++; | |
114 | else if (p[len - 1] != '.') | |
7203d6bb | 115 | fail++; |
39c00dc2 | 116 | else if (strncasecmp(host, p, len - 1) != 0) |
7203d6bb | 117 | fail++; |
39c00dc2 | 118 | xfree(p); |
119 | ||
120 | /* local user */ | |
121 | p = buffer_get_string(&b, NULL); | |
122 | ||
123 | if (strcmp(pw->pw_name, p) != 0) | |
124 | fail++; | |
125 | xfree(p); | |
126 | ||
127 | /* end of message */ | |
128 | if (buffer_len(&b) != 0) | |
129 | fail++; | |
43f7a4b8 | 130 | buffer_free(&b); |
39c00dc2 | 131 | |
132 | debug3("valid_request: fail %d", fail); | |
133 | ||
134 | if (fail && key != NULL) | |
135 | key_free(key); | |
136 | else | |
137 | *ret = key; | |
138 | ||
139 | return (fail ? -1 : 0); | |
140 | } | |
141 | ||
142 | int | |
143 | main(int argc, char **argv) | |
144 | { | |
145 | Buffer b; | |
60cd0a97 | 146 | Options options; |
39c00dc2 | 147 | Key *keys[2], *key; |
148 | struct passwd *pw; | |
149 | int key_fd[2], i, found, version = 2, fd; | |
150 | u_char *signature, *data; | |
151 | char *host; | |
152 | u_int slen, dlen; | |
261189cc | 153 | u_int32_t rnd[256]; |
39c00dc2 | 154 | |
fd6168c1 | 155 | /* Ensure that stdin and stdout are connected */ |
156 | if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2) | |
157 | exit(1); | |
158 | /* Leave /dev/null fd iff it is attached to stderr */ | |
159 | if (fd > 2) | |
160 | close(fd); | |
161 | ||
39c00dc2 | 162 | key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); |
163 | key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); | |
164 | ||
baab9e74 | 165 | original_real_uid = getuid(); /* XXX readconf.c needs this */ |
166 | if ((pw = getpwuid(original_real_uid)) == NULL) | |
6213295d | 167 | fatal("getpwuid failed"); |
168 | pw = pwcopy(pw); | |
169 | ||
170 | permanently_set_uid(pw); | |
39c00dc2 | 171 | |
875ec275 | 172 | init_rng(); |
173 | seed_rng(); | |
174 | arc4random_stir(); | |
04eb391d | 175 | |
39c00dc2 | 176 | #ifdef DEBUG_SSH_KEYSIGN |
177 | log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); | |
7203d6bb | 178 | #endif |
39c00dc2 | 179 | |
60cd0a97 | 180 | /* verify that ssh-keysign is enabled by the admin */ |
60cd0a97 | 181 | initialize_options(&options); |
9f6cab4b | 182 | (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0); |
60cd0a97 | 183 | fill_default_options(&options); |
cc46e2ee | 184 | if (options.enable_ssh_keysign != 1) |
185 | fatal("ssh-keysign not enabled in %s", | |
60cd0a97 | 186 | _PATH_HOST_CONFIG_FILE); |
187 | ||
39c00dc2 | 188 | if (key_fd[0] == -1 && key_fd[1] == -1) |
189 | fatal("could not open any host key"); | |
190 | ||
39c00dc2 | 191 | SSLeay_add_all_algorithms(); |
261189cc | 192 | for (i = 0; i < 256; i++) |
193 | rnd[i] = arc4random(); | |
194 | RAND_seed(rnd, sizeof(rnd)); | |
39c00dc2 | 195 | |
196 | found = 0; | |
197 | for (i = 0; i < 2; i++) { | |
198 | keys[i] = NULL; | |
199 | if (key_fd[i] == -1) | |
200 | continue; | |
201 | keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC, | |
202 | NULL, NULL); | |
203 | close(key_fd[i]); | |
204 | if (keys[i] != NULL) | |
205 | found = 1; | |
206 | } | |
207 | if (!found) | |
208 | fatal("no hostkey found"); | |
209 | ||
210 | buffer_init(&b); | |
e987fdbe | 211 | if (ssh_msg_recv(STDIN_FILENO, &b) < 0) |
212 | fatal("ssh_msg_recv failed"); | |
39c00dc2 | 213 | if (buffer_get_char(&b) != version) |
214 | fatal("bad version"); | |
215 | fd = buffer_get_int(&b); | |
216 | if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO)) | |
217 | fatal("bad fd"); | |
218 | if ((host = get_local_name(fd)) == NULL) | |
219 | fatal("cannot get sockname for fd"); | |
7203d6bb | 220 | |
39c00dc2 | 221 | data = buffer_get_string(&b, &dlen); |
222 | if (valid_request(pw, host, &key, data, dlen) < 0) | |
223 | fatal("not a valid request"); | |
39c00dc2 | 224 | xfree(host); |
225 | ||
226 | found = 0; | |
227 | for (i = 0; i < 2; i++) { | |
228 | if (keys[i] != NULL && | |
229 | key_equal(key, keys[i])) { | |
230 | found = 1; | |
231 | break; | |
232 | } | |
233 | } | |
234 | if (!found) | |
235 | fatal("no matching hostkey found"); | |
236 | ||
237 | if (key_sign(keys[i], &signature, &slen, data, dlen) != 0) | |
238 | fatal("key_sign failed"); | |
20e79e98 | 239 | xfree(data); |
7203d6bb | 240 | |
39c00dc2 | 241 | /* send reply */ |
242 | buffer_clear(&b); | |
243 | buffer_put_string(&b, signature, slen); | |
d3cbe6f8 | 244 | if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1) |
245 | fatal("ssh_msg_send failed"); | |
39c00dc2 | 246 | |
247 | return (0); | |
248 | } |