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39c00dc2 | 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" | |
a75f5360 | 25 | RCSID("$OpenBSD: ssh-keysign.c,v 1.20 2006/02/08 12:15:27 stevesk Exp $"); |
26 | ||
27 | #include <paths.h> | |
39c00dc2 | 28 | |
29 | #include <openssl/evp.h> | |
261189cc | 30 | #include <openssl/rand.h> |
31 | #include <openssl/rsa.h> | |
39c00dc2 | 32 | |
33 | #include "log.h" | |
34 | #include "key.h" | |
60cd0a97 | 35 | #include "ssh.h" |
39c00dc2 | 36 | #include "ssh2.h" |
37 | #include "misc.h" | |
38 | #include "xmalloc.h" | |
39 | #include "buffer.h" | |
40 | #include "bufaux.h" | |
41 | #include "authfile.h" | |
42 | #include "msg.h" | |
43 | #include "canohost.h" | |
44 | #include "pathnames.h" | |
60cd0a97 | 45 | #include "readconf.h" |
6213295d | 46 | #include "uidswap.h" |
60cd0a97 | 47 | |
f811e52a | 48 | /* XXX readconf.c needs these */ |
49 | uid_t original_real_uid; | |
39c00dc2 | 50 | |
95d5ebf7 | 51 | extern char *__progname; |
95d5ebf7 | 52 | |
39c00dc2 | 53 | static int |
54 | valid_request(struct passwd *pw, char *host, Key **ret, u_char *data, | |
55 | u_int datalen) | |
56 | { | |
57 | Buffer b; | |
16f1b5ca | 58 | Key *key = NULL; |
39c00dc2 | 59 | 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); | |
7203d6bb | 68 | |
1f143cf2 | 69 | /* 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 | ||
39c00dc2 | 75 | 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] != '.') | |
7203d6bb | 113 | fail++; |
39c00dc2 | 114 | else if (strncasecmp(host, p, len - 1) != 0) |
7203d6bb | 115 | fail++; |
39c00dc2 | 116 | 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++; | |
43f7a4b8 | 128 | buffer_free(&b); |
39c00dc2 | 129 | |
130 | debug3("valid_request: fail %d", fail); | |
131 | ||
132 | if (fail && key != NULL) | |
133 | key_free(key); | |
134 | else | |
135 | *ret = key; | |
136 | ||
137 | return (fail ? -1 : 0); | |
138 | } | |
139 | ||
140 | int | |
141 | main(int argc, char **argv) | |
142 | { | |
143 | Buffer b; | |
60cd0a97 | 144 | Options options; |
39c00dc2 | 145 | Key *keys[2], *key; |
146 | struct passwd *pw; | |
147 | int key_fd[2], i, found, version = 2, fd; | |
148 | u_char *signature, *data; | |
149 | char *host; | |
150 | u_int slen, dlen; | |
261189cc | 151 | u_int32_t rnd[256]; |
39c00dc2 | 152 | |
fd6168c1 | 153 | /* Ensure that stdin and stdout are connected */ |
154 | if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2) | |
155 | exit(1); | |
156 | /* Leave /dev/null fd iff it is attached to stderr */ | |
157 | if (fd > 2) | |
158 | close(fd); | |
159 | ||
39c00dc2 | 160 | key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); |
161 | key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); | |
162 | ||
baab9e74 | 163 | original_real_uid = getuid(); /* XXX readconf.c needs this */ |
164 | if ((pw = getpwuid(original_real_uid)) == NULL) | |
6213295d | 165 | fatal("getpwuid failed"); |
166 | pw = pwcopy(pw); | |
167 | ||
168 | permanently_set_uid(pw); | |
39c00dc2 | 169 | |
875ec275 | 170 | init_rng(); |
171 | seed_rng(); | |
172 | arc4random_stir(); | |
04eb391d | 173 | |
39c00dc2 | 174 | #ifdef DEBUG_SSH_KEYSIGN |
175 | log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); | |
7203d6bb | 176 | #endif |
39c00dc2 | 177 | |
60cd0a97 | 178 | /* verify that ssh-keysign is enabled by the admin */ |
60cd0a97 | 179 | initialize_options(&options); |
9f6cab4b | 180 | (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0); |
60cd0a97 | 181 | fill_default_options(&options); |
cc46e2ee | 182 | if (options.enable_ssh_keysign != 1) |
183 | fatal("ssh-keysign not enabled in %s", | |
60cd0a97 | 184 | _PATH_HOST_CONFIG_FILE); |
185 | ||
39c00dc2 | 186 | if (key_fd[0] == -1 && key_fd[1] == -1) |
187 | fatal("could not open any host key"); | |
188 | ||
39c00dc2 | 189 | SSLeay_add_all_algorithms(); |
261189cc | 190 | for (i = 0; i < 256; i++) |
191 | rnd[i] = arc4random(); | |
192 | RAND_seed(rnd, sizeof(rnd)); | |
39c00dc2 | 193 | |
194 | found = 0; | |
195 | for (i = 0; i < 2; i++) { | |
196 | keys[i] = NULL; | |
197 | if (key_fd[i] == -1) | |
198 | continue; | |
199 | keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC, | |
200 | NULL, NULL); | |
201 | close(key_fd[i]); | |
202 | if (keys[i] != NULL) | |
203 | found = 1; | |
204 | } | |
205 | if (!found) | |
206 | fatal("no hostkey found"); | |
207 | ||
208 | buffer_init(&b); | |
e987fdbe | 209 | if (ssh_msg_recv(STDIN_FILENO, &b) < 0) |
210 | fatal("ssh_msg_recv failed"); | |
39c00dc2 | 211 | if (buffer_get_char(&b) != version) |
212 | fatal("bad version"); | |
213 | fd = buffer_get_int(&b); | |
214 | if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO)) | |
215 | fatal("bad fd"); | |
216 | if ((host = get_local_name(fd)) == NULL) | |
217 | fatal("cannot get sockname for fd"); | |
7203d6bb | 218 | |
39c00dc2 | 219 | data = buffer_get_string(&b, &dlen); |
220 | if (valid_request(pw, host, &key, data, dlen) < 0) | |
221 | fatal("not a valid request"); | |
39c00dc2 | 222 | xfree(host); |
223 | ||
224 | found = 0; | |
225 | for (i = 0; i < 2; i++) { | |
226 | if (keys[i] != NULL && | |
227 | key_equal(key, keys[i])) { | |
228 | found = 1; | |
229 | break; | |
230 | } | |
231 | } | |
232 | if (!found) | |
233 | fatal("no matching hostkey found"); | |
234 | ||
235 | if (key_sign(keys[i], &signature, &slen, data, dlen) != 0) | |
236 | fatal("key_sign failed"); | |
20e79e98 | 237 | xfree(data); |
7203d6bb | 238 | |
39c00dc2 | 239 | /* send reply */ |
240 | buffer_clear(&b); | |
241 | buffer_put_string(&b, signature, slen); | |
d3cbe6f8 | 242 | if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1) |
243 | fatal("ssh_msg_send failed"); | |
39c00dc2 | 244 | |
245 | return (0); | |
246 | } |