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f5799ae1 | 1 | /* |
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" | |
996d5e62 | 25 | RCSID("$OpenBSD: ssh-keysign.c,v 1.18 2004/08/23 14:29:23 dtucker Exp $"); |
f5799ae1 | 26 | |
27 | #include <openssl/evp.h> | |
41b2f314 | 28 | #include <openssl/rand.h> |
29 | #include <openssl/rsa.h> | |
f5799ae1 | 30 | |
31 | #include "log.h" | |
32 | #include "key.h" | |
41b2f314 | 33 | #include "ssh.h" |
f5799ae1 | 34 | #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" | |
41b2f314 | 43 | #include "readconf.h" |
c9f39d2c | 44 | #include "uidswap.h" |
41b2f314 | 45 | |
0fff78ff | 46 | /* XXX readconf.c needs these */ |
47 | uid_t original_real_uid; | |
f5799ae1 | 48 | |
f5799ae1 | 49 | extern char *__progname; |
f5799ae1 | 50 | |
51 | static int | |
52 | valid_request(struct passwd *pw, char *host, Key **ret, u_char *data, | |
53 | u_int datalen) | |
54 | { | |
55 | Buffer b; | |
0fff78ff | 56 | Key *key = NULL; |
f5799ae1 | 57 | 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); | |
66 | ||
67 | /* 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 | ||
73 | 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] != '.') | |
111 | fail++; | |
112 | else if (strncasecmp(host, p, len - 1) != 0) | |
113 | fail++; | |
114 | 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++; | |
cdd66111 | 126 | buffer_free(&b); |
f5799ae1 | 127 | |
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 | ||
138 | int | |
139 | main(int argc, char **argv) | |
140 | { | |
141 | Buffer b; | |
41b2f314 | 142 | Options options; |
f5799ae1 | 143 | 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; | |
41b2f314 | 149 | u_int32_t rnd[256]; |
f5799ae1 | 150 | |
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 | ||
996d5e62 | 154 | original_real_uid = getuid(); /* XXX readconf.c needs this */ |
155 | if ((pw = getpwuid(original_real_uid)) == NULL) | |
c9f39d2c | 156 | fatal("getpwuid failed"); |
157 | pw = pwcopy(pw); | |
158 | ||
159 | permanently_set_uid(pw); | |
f5799ae1 | 160 | |
161 | init_rng(); | |
162 | seed_rng(); | |
163 | arc4random_stir(); | |
164 | ||
165 | #ifdef DEBUG_SSH_KEYSIGN | |
166 | log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); | |
167 | #endif | |
168 | ||
41b2f314 | 169 | /* verify that ssh-keysign is enabled by the admin */ |
41b2f314 | 170 | initialize_options(&options); |
c9f39d2c | 171 | (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0); |
41b2f314 | 172 | fill_default_options(&options); |
6a9b3198 | 173 | if (options.enable_ssh_keysign != 1) |
174 | fatal("ssh-keysign not enabled in %s", | |
41b2f314 | 175 | _PATH_HOST_CONFIG_FILE); |
176 | ||
f5799ae1 | 177 | if (key_fd[0] == -1 && key_fd[1] == -1) |
178 | fatal("could not open any host key"); | |
179 | ||
f5799ae1 | 180 | SSLeay_add_all_algorithms(); |
41b2f314 | 181 | for (i = 0; i < 256; i++) |
182 | rnd[i] = arc4random(); | |
183 | RAND_seed(rnd, sizeof(rnd)); | |
f5799ae1 | 184 | |
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); | |
41b2f314 | 200 | if (ssh_msg_recv(STDIN_FILENO, &b) < 0) |
201 | fatal("ssh_msg_recv failed"); | |
f5799ae1 | 202 | 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"); | |
209 | ||
210 | data = buffer_get_string(&b, &dlen); | |
211 | if (valid_request(pw, host, &key, data, dlen) < 0) | |
212 | fatal("not a valid request"); | |
f5799ae1 | 213 | 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"); | |
41b2f314 | 228 | xfree(data); |
f5799ae1 | 229 | |
230 | /* send reply */ | |
231 | buffer_clear(&b); | |
232 | buffer_put_string(&b, signature, slen); | |
cdd66111 | 233 | if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1) |
234 | fatal("ssh_msg_send failed"); | |
f5799ae1 | 235 | |
236 | return (0); | |
237 | } |