1 /* $OpenBSD: auth2-pubkey.c,v 1.15 2006/08/03 03:34:41 deraadt Exp $ */
3 * Copyright (c) 2000 Markus Friedl. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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.
28 #include <sys/types.h>
47 #include "pathnames.h"
49 #include "auth-options.h"
54 #include "monitor_wrap.h"
58 extern ServerOptions options;
59 extern u_char *session_id2;
60 extern u_int session_id2_len;
63 userauth_pubkey(Authctxt *authctxt)
69 u_int alen, blen, slen;
71 int authenticated = 0;
73 if (!authctxt->valid) {
74 debug2("userauth_pubkey: disabled because of invalid user");
77 have_sig = packet_get_char();
78 if (datafellows & SSH_BUG_PKAUTH) {
79 debug2("userauth_pubkey: SSH_BUG_PKAUTH");
80 /* no explicit pkalg given */
81 pkblob = packet_get_string(&blen);
83 buffer_append(&b, pkblob, blen);
84 /* so we have to extract the pkalg from the pkblob */
85 pkalg = buffer_get_string(&b, &alen);
88 pkalg = packet_get_string(&alen);
89 pkblob = packet_get_string(&blen);
91 pktype = key_type_from_name(pkalg);
92 if (pktype == KEY_UNSPEC) {
93 /* this is perfectly legal */
94 logit("userauth_pubkey: unsupported public key algorithm: %s",
98 key = key_from_blob(pkblob, blen);
100 error("userauth_pubkey: cannot decode key: %s", pkalg);
103 if (key->type != pktype) {
104 error("userauth_pubkey: type mismatch for decoded key "
105 "(received %d, expected %d)", key->type, pktype);
109 sig = packet_get_string(&slen);
112 if (datafellows & SSH_OLD_SESSIONID) {
113 buffer_append(&b, session_id2, session_id2_len);
115 buffer_put_string(&b, session_id2, session_id2_len);
117 /* reconstruct packet */
118 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
119 buffer_put_cstring(&b, authctxt->user);
120 buffer_put_cstring(&b,
121 datafellows & SSH_BUG_PKSERVICE ?
124 if (datafellows & SSH_BUG_PKAUTH) {
125 buffer_put_char(&b, have_sig);
127 buffer_put_cstring(&b, "publickey");
128 buffer_put_char(&b, have_sig);
129 buffer_put_cstring(&b, pkalg);
131 buffer_put_string(&b, pkblob, blen);
135 /* test for correct signature */
137 if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
138 PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
139 buffer_len(&b))) == 1)
144 debug("test whether pkalg/pkblob are acceptable");
147 /* XXX fake reply and always send PK_OK ? */
149 * XXX this allows testing whether a user is allowed
150 * to login: if you happen to have a valid pubkey this
151 * message is sent. the message is NEVER sent at all
152 * if a user is not allowed to login. is this an
155 if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
156 packet_start(SSH2_MSG_USERAUTH_PK_OK);
157 packet_put_string(pkalg, alen);
158 packet_put_string(pkblob, blen);
161 authctxt->postponed = 1;
164 if (authenticated != 1)
165 auth_clear_options();
167 debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
173 if (check_nt_auth(0, authctxt->pw) == 0)
176 return authenticated;
179 /* return 1 if user allows given key */
181 user_key_allowed2(struct passwd *pw, Key *key, char *file)
183 char line[SSH_MAX_PUBKEY_BYTES];
191 /* Temporarily use the user's uid. */
192 temporarily_use_uid(pw);
194 debug("trying public key file %s", file);
196 /* Fail quietly if file does not exist */
197 if (stat(file, &st) < 0) {
198 /* Restore the privileged uid. */
202 /* Open the file containing the authorized keys. */
203 f = fopen(file, "r");
205 /* Restore the privileged uid. */
209 if (options.strict_modes &&
210 secure_filename(f, file, pw, line, sizeof(line)) != 0) {
212 logit("Authentication refused: %s", line);
218 found = key_new(key->type);
220 while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
221 char *cp, *key_options = NULL;
223 /* Skip leading whitespace, empty and comment lines. */
224 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
226 if (!*cp || *cp == '\n' || *cp == '#')
229 if (key_read(found, &cp) != 1) {
230 /* no key? check if there are options for this key */
232 debug2("user_key_allowed: check options: '%s'", cp);
234 for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
235 if (*cp == '\\' && cp[1] == '"')
236 cp++; /* Skip both */
240 /* Skip remaining whitespace. */
241 for (; *cp == ' ' || *cp == '\t'; cp++)
243 if (key_read(found, &cp) != 1) {
244 debug2("user_key_allowed: advance: '%s'", cp);
245 /* still no key? advance to next line*/
249 if (key_equal(found, key) &&
250 auth_parse_options(pw, key_options, file, linenum) == 1) {
252 debug("matching key found: file %s, line %lu",
254 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
255 verbose("Found matching %s key: %s",
256 key_type(found), fp);
265 debug2("key not found");
269 /* check whether given key is in .ssh/authorized_keys* */
271 user_key_allowed(struct passwd *pw, Key *key)
277 if (blacklisted_key(key)) {
278 fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
279 if (options.permit_blacklisted_keys)
280 logit("Public key %s blacklisted (see "
281 "ssh-vulnkey(1)); continuing anyway", fp);
283 logit("Public key %s blacklisted (see "
284 "ssh-vulnkey(1))", fp);
286 if (!options.permit_blacklisted_keys)
290 file = authorized_keys_file(pw);
291 success = user_key_allowed2(pw, key, file);
296 /* try suffix "2" for backward compat, too */
297 file = authorized_keys_file2(pw);
298 success = user_key_allowed2(pw, key, file);
303 Authmethod method_pubkey = {
306 &options.pubkey_authentication