1 /* $OpenBSD: auth2-hostbased.c,v 1.18 2014/07/15 15:54:14 millert 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>
50 #include "monitor_wrap.h"
51 #include "pathnames.h"
54 extern ServerOptions options;
55 extern u_char *session_id2;
56 extern u_int session_id2_len;
59 userauth_hostbased(Authctxt *authctxt)
63 char *pkalg, *cuser, *chost, *service;
65 u_int alen, blen, slen;
67 int authenticated = 0;
69 if (!authctxt->valid) {
70 debug2("userauth_hostbased: disabled because of invalid user");
73 pkalg = packet_get_string(&alen);
74 pkblob = packet_get_string(&blen);
75 chost = packet_get_string(NULL);
76 cuser = packet_get_string(NULL);
77 sig = packet_get_string(&slen);
79 debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d",
80 cuser, chost, pkalg, slen);
84 buffer_append(&b, sig, slen);
88 pktype = key_type_from_name(pkalg);
89 if (pktype == KEY_UNSPEC) {
90 /* this is perfectly legal */
91 logit("userauth_hostbased: unsupported "
92 "public key algorithm: %s", pkalg);
95 key = key_from_blob(pkblob, blen);
97 error("userauth_hostbased: cannot decode key: %s", pkalg);
100 if (key->type != pktype) {
101 error("userauth_hostbased: type mismatch for decoded key "
102 "(received %d, expected %d)", key->type, pktype);
105 if (key_type_plain(key->type) == KEY_RSA &&
106 (datafellows & SSH_BUG_RSASIGMD5) != 0) {
107 error("Refusing RSA key because peer uses unsafe "
111 service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
114 buffer_put_string(&b, session_id2, session_id2_len);
115 /* reconstruct packet */
116 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
117 buffer_put_cstring(&b, authctxt->user);
118 buffer_put_cstring(&b, service);
119 buffer_put_cstring(&b, "hostbased");
120 buffer_put_string(&b, pkalg, alen);
121 buffer_put_string(&b, pkblob, blen);
122 buffer_put_cstring(&b, chost);
123 buffer_put_cstring(&b, cuser);
128 pubkey_auth_info(authctxt, key,
129 "client user \"%.100s\", client host \"%.100s\"", cuser, chost);
131 /* test for allowed key and correct signature */
133 if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
134 PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
135 buffer_len(&b))) == 1)
140 debug2("userauth_hostbased: authenticated %d", authenticated);
148 return authenticated;
151 /* return 1 if given hostkey is allowed */
153 hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
156 const char *resolvedname, *ipaddr, *lookup, *reason;
157 HostStatus host_status;
161 if (auth_key_is_revoked(key))
164 if (blacklisted_key(key)) {
165 fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
166 if (options.permit_blacklisted_keys)
167 logit("Public key %s blacklisted (see "
168 "ssh-vulnkey(1)); continuing anyway", fp);
170 logit("Public key %s blacklisted (see "
171 "ssh-vulnkey(1))", fp);
173 if (!options.permit_blacklisted_keys)
177 resolvedname = get_canonical_hostname(options.use_dns);
178 ipaddr = get_remote_ipaddr();
180 debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s",
181 chost, resolvedname, ipaddr);
183 if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
184 debug2("stripping trailing dot from chost %s", chost);
185 chost[len - 1] = '\0';
188 if (options.hostbased_uses_name_from_packet_only) {
189 if (auth_rhosts2(pw, cuser, chost, chost) == 0)
193 if (strcasecmp(resolvedname, chost) != 0)
194 logit("userauth_hostbased mismatch: "
195 "client sends %s, but we resolve %s to %s",
196 chost, ipaddr, resolvedname);
197 if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0)
199 lookup = resolvedname;
201 debug2("userauth_hostbased: access allowed by auth_rhosts2");
203 if (key_is_cert(key) &&
204 key_cert_check_authority(key, 1, 0, lookup, &reason)) {
206 auth_debug_add("%s", reason);
210 host_status = check_key_in_hostfiles(pw, key, lookup,
211 _PATH_SSH_SYSTEM_HOSTFILE,
212 options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
214 /* backward compat if no key has been found. */
215 if (host_status == HOST_NEW) {
216 host_status = check_key_in_hostfiles(pw, key, lookup,
217 _PATH_SSH_SYSTEM_HOSTFILE2,
218 options.ignore_user_known_hosts ? NULL :
219 _PATH_SSH_USER_HOSTFILE2);
222 if (host_status == HOST_OK) {
223 if (key_is_cert(key)) {
224 fp = key_fingerprint(key->cert->signature_key,
225 SSH_FP_MD5, SSH_FP_HEX);
226 verbose("Accepted certificate ID \"%s\" signed by "
227 "%s CA %s from %s@%s", key->cert->key_id,
228 key_type(key->cert->signature_key), fp,
231 fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
232 verbose("Accepted %s public key %s from %s@%s",
233 key_type(key), fp, cuser, lookup);
238 return (host_status == HOST_OK);
241 Authmethod method_hostbased = {
244 &options.hostbased_authentication