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884dc78b | 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" | |
08822d99 | 25 | RCSID("$OpenBSD: ssh-keysign.c,v 1.19 2005/09/13 23:40:07 djm Exp $"); |
884dc78b | 26 | |
27 | #include <openssl/evp.h> | |
d03f4262 | 28 | #include <openssl/rand.h> |
29 | #include <openssl/rsa.h> | |
884dc78b | 30 | |
31 | #include "log.h" | |
32 | #include "key.h" | |
d03f4262 | 33 | #include "ssh.h" |
884dc78b | 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" | |
d03f4262 | 43 | #include "readconf.h" |
7e82606e | 44 | #include "uidswap.h" |
d03f4262 | 45 | |
7cac2b65 | 46 | /* XXX readconf.c needs these */ |
47 | uid_t original_real_uid; | |
884dc78b | 48 | |
884dc78b | 49 | extern char *__progname; |
884dc78b | 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; | |
7cac2b65 | 56 | Key *key = NULL; |
884dc78b | 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++; | |
540d72c3 | 126 | buffer_free(&b); |
884dc78b | 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; | |
d03f4262 | 142 | Options options; |
884dc78b | 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; | |
d03f4262 | 149 | u_int32_t rnd[256]; |
884dc78b | 150 | |
08822d99 | 151 | /* Ensure that stdin and stdout are connected */ |
152 | if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2) | |
153 | exit(1); | |
154 | /* Leave /dev/null fd iff it is attached to stderr */ | |
155 | if (fd > 2) | |
156 | close(fd); | |
157 | ||
884dc78b | 158 | key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); |
159 | key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); | |
160 | ||
dfddba3d | 161 | original_real_uid = getuid(); /* XXX readconf.c needs this */ |
162 | if ((pw = getpwuid(original_real_uid)) == NULL) | |
7e82606e | 163 | fatal("getpwuid failed"); |
164 | pw = pwcopy(pw); | |
165 | ||
166 | permanently_set_uid(pw); | |
884dc78b | 167 | |
168 | init_rng(); | |
169 | seed_rng(); | |
170 | arc4random_stir(); | |
171 | ||
172 | #ifdef DEBUG_SSH_KEYSIGN | |
173 | log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); | |
174 | #endif | |
175 | ||
d03f4262 | 176 | /* verify that ssh-keysign is enabled by the admin */ |
d03f4262 | 177 | initialize_options(&options); |
7e82606e | 178 | (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0); |
d03f4262 | 179 | fill_default_options(&options); |
bfe49944 | 180 | if (options.enable_ssh_keysign != 1) |
181 | fatal("ssh-keysign not enabled in %s", | |
d03f4262 | 182 | _PATH_HOST_CONFIG_FILE); |
183 | ||
884dc78b | 184 | if (key_fd[0] == -1 && key_fd[1] == -1) |
185 | fatal("could not open any host key"); | |
186 | ||
884dc78b | 187 | SSLeay_add_all_algorithms(); |
d03f4262 | 188 | for (i = 0; i < 256; i++) |
189 | rnd[i] = arc4random(); | |
190 | RAND_seed(rnd, sizeof(rnd)); | |
884dc78b | 191 | |
192 | found = 0; | |
193 | for (i = 0; i < 2; i++) { | |
194 | keys[i] = NULL; | |
195 | if (key_fd[i] == -1) | |
196 | continue; | |
197 | keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC, | |
198 | NULL, NULL); | |
199 | close(key_fd[i]); | |
200 | if (keys[i] != NULL) | |
201 | found = 1; | |
202 | } | |
203 | if (!found) | |
204 | fatal("no hostkey found"); | |
205 | ||
206 | buffer_init(&b); | |
d03f4262 | 207 | if (ssh_msg_recv(STDIN_FILENO, &b) < 0) |
208 | fatal("ssh_msg_recv failed"); | |
884dc78b | 209 | if (buffer_get_char(&b) != version) |
210 | fatal("bad version"); | |
211 | fd = buffer_get_int(&b); | |
212 | if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO)) | |
213 | fatal("bad fd"); | |
214 | if ((host = get_local_name(fd)) == NULL) | |
215 | fatal("cannot get sockname for fd"); | |
216 | ||
217 | data = buffer_get_string(&b, &dlen); | |
218 | if (valid_request(pw, host, &key, data, dlen) < 0) | |
219 | fatal("not a valid request"); | |
884dc78b | 220 | xfree(host); |
221 | ||
222 | found = 0; | |
223 | for (i = 0; i < 2; i++) { | |
224 | if (keys[i] != NULL && | |
225 | key_equal(key, keys[i])) { | |
226 | found = 1; | |
227 | break; | |
228 | } | |
229 | } | |
230 | if (!found) | |
231 | fatal("no matching hostkey found"); | |
232 | ||
233 | if (key_sign(keys[i], &signature, &slen, data, dlen) != 0) | |
234 | fatal("key_sign failed"); | |
d03f4262 | 235 | xfree(data); |
884dc78b | 236 | |
237 | /* send reply */ | |
238 | buffer_clear(&b); | |
239 | buffer_put_string(&b, signature, slen); | |
540d72c3 | 240 | if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1) |
241 | fatal("ssh_msg_send failed"); | |
884dc78b | 242 | |
243 | return (0); | |
244 | } |