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djm@openbsd.org95767262016-03-07 19:02:43 +00001/* $OpenBSD: auth2-hostbased.c,v 1.26 2016/03/07 19:02:43 djm Exp $ */
Ben Lindstrom855bf3a2002-06-06 20:27:55 +00002/*
3 * Copyright (c) 2000 Markus Friedl. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
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.
13 *
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.
24 */
25
26#include "includes.h"
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000027
Damien Miller9f2abc42006-07-10 20:53:08 +100028#include <sys/types.h>
29
30#include <pwd.h>
Damien Millere3476ed2006-07-24 14:13:33 +100031#include <string.h>
Damien Millerd7834352006-08-05 12:39:39 +100032#include <stdarg.h>
Damien Miller9f2abc42006-07-10 20:53:08 +100033
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000034#include "xmalloc.h"
Damien Millerd7834352006-08-05 12:39:39 +100035#include "ssh2.h"
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000036#include "packet.h"
37#include "buffer.h"
38#include "log.h"
Damien Miller7acefbb2014-07-18 14:11:24 +100039#include "misc.h"
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000040#include "servconf.h"
41#include "compat.h"
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000042#include "key.h"
Damien Millerd7834352006-08-05 12:39:39 +100043#include "hostfile.h"
44#include "auth.h"
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000045#include "canohost.h"
Damien Millerd7834352006-08-05 12:39:39 +100046#ifdef GSSAPI
47#include "ssh-gss.h"
48#endif
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000049#include "monitor_wrap.h"
50#include "pathnames.h"
djm@openbsd.org1f729f02015-01-13 07:39:19 +000051#include "match.h"
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000052
53/* import */
54extern ServerOptions options;
55extern u_char *session_id2;
Darren Tucker502d3842003-06-28 12:38:01 +100056extern u_int session_id2_len;
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000057
58static int
59userauth_hostbased(Authctxt *authctxt)
60{
61 Buffer b;
62 Key *key = NULL;
63 char *pkalg, *cuser, *chost, *service;
64 u_char *pkblob, *sig;
65 u_int alen, blen, slen;
66 int pktype;
67 int authenticated = 0;
68
69 if (!authctxt->valid) {
70 debug2("userauth_hostbased: disabled because of invalid user");
71 return 0;
72 }
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);
78
79 debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d",
80 cuser, chost, pkalg, slen);
81#ifdef DEBUG_PK
82 debug("signature:");
83 buffer_init(&b);
84 buffer_append(&b, sig, slen);
85 buffer_dump(&b);
86 buffer_free(&b);
87#endif
88 pktype = key_type_from_name(pkalg);
89 if (pktype == KEY_UNSPEC) {
90 /* this is perfectly legal */
Damien Miller996acd22003-04-09 20:59:48 +100091 logit("userauth_hostbased: unsupported "
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000092 "public key algorithm: %s", pkalg);
93 goto done;
94 }
95 key = key_from_blob(pkblob, blen);
96 if (key == NULL) {
97 error("userauth_hostbased: cannot decode key: %s", pkalg);
98 goto done;
99 }
100 if (key->type != pktype) {
101 error("userauth_hostbased: type mismatch for decoded key "
102 "(received %d, expected %d)", key->type, pktype);
103 goto done;
104 }
Damien Miller324541e2013-12-31 12:25:40 +1100105 if (key_type_plain(key->type) == KEY_RSA &&
106 (datafellows & SSH_BUG_RSASIGMD5) != 0) {
107 error("Refusing RSA key because peer uses unsafe "
108 "signature format");
109 goto done;
110 }
djm@openbsd.org1f729f02015-01-13 07:39:19 +0000111 if (match_pattern_list(sshkey_ssh_name(key),
djm@openbsd.orge661a862015-05-04 06:10:48 +0000112 options.hostbased_key_types, 0) != 1) {
djm@openbsd.org1f729f02015-01-13 07:39:19 +0000113 logit("%s: key type %s not in HostbasedAcceptedKeyTypes",
114 __func__, sshkey_type(key));
115 goto done;
116 }
117
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000118 service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
119 authctxt->service;
120 buffer_init(&b);
121 buffer_put_string(&b, session_id2, session_id2_len);
122 /* reconstruct packet */
123 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
124 buffer_put_cstring(&b, authctxt->user);
125 buffer_put_cstring(&b, service);
126 buffer_put_cstring(&b, "hostbased");
127 buffer_put_string(&b, pkalg, alen);
128 buffer_put_string(&b, pkblob, blen);
129 buffer_put_cstring(&b, chost);
130 buffer_put_cstring(&b, cuser);
131#ifdef DEBUG_PK
132 buffer_dump(&b);
133#endif
Damien Miller20bdcd72013-07-18 16:10:09 +1000134
135 pubkey_auth_info(authctxt, key,
136 "client user \"%.100s\", client host \"%.100s\"", cuser, chost);
137
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000138 /* test for allowed key and correct signature */
139 authenticated = 0;
140 if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
141 PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
142 buffer_len(&b))) == 1)
143 authenticated = 1;
144
Damien Millerfb1310e2004-01-21 11:02:50 +1100145 buffer_free(&b);
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000146done:
147 debug2("userauth_hostbased: authenticated %d", authenticated);
148 if (key != NULL)
149 key_free(key);
Darren Tuckera627d422013-06-02 07:31:17 +1000150 free(pkalg);
151 free(pkblob);
152 free(cuser);
153 free(chost);
154 free(sig);
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000155 return authenticated;
156}
157
158/* return 1 if given hostkey is allowed */
159int
160hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
161 Key *key)
162{
djm@openbsd.org95767262016-03-07 19:02:43 +0000163 struct ssh *ssh = active_state; /* XXX */
Damien Millerc1583312010-08-05 13:04:50 +1000164 const char *resolvedname, *ipaddr, *lookup, *reason;
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000165 HostStatus host_status;
166 int len;
Damien Millerc1583312010-08-05 13:04:50 +1000167 char *fp;
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000168
Damien Miller1aed65e2010-03-04 21:53:35 +1100169 if (auth_key_is_revoked(key))
170 return 0;
171
djm@openbsd.org95767262016-03-07 19:02:43 +0000172 resolvedname = auth_get_canonical_hostname(ssh, options.use_dns);
173 ipaddr = ssh_remote_ipaddr(ssh);
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000174
djm@openbsd.org5191df92014-12-23 22:42:48 +0000175 debug2("%s: chost %s resolvedname %s ipaddr %s", __func__,
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000176 chost, resolvedname, ipaddr);
177
Damien Millera1d03a52008-07-17 18:57:19 +1000178 if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
179 debug2("stripping trailing dot from chost %s", chost);
180 chost[len - 1] = '\0';
181 }
182
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000183 if (options.hostbased_uses_name_from_packet_only) {
djm@openbsd.org5191df92014-12-23 22:42:48 +0000184 if (auth_rhosts2(pw, cuser, chost, chost) == 0) {
185 debug2("%s: auth_rhosts2 refused "
186 "user \"%.100s\" host \"%.100s\" (from packet)",
187 __func__, cuser, chost);
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000188 return 0;
djm@openbsd.org5191df92014-12-23 22:42:48 +0000189 }
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000190 lookup = chost;
191 } else {
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000192 if (strcasecmp(resolvedname, chost) != 0)
Damien Miller996acd22003-04-09 20:59:48 +1000193 logit("userauth_hostbased mismatch: "
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000194 "client sends %s, but we resolve %s to %s",
195 chost, ipaddr, resolvedname);
djm@openbsd.org5191df92014-12-23 22:42:48 +0000196 if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) {
197 debug2("%s: auth_rhosts2 refused "
198 "user \"%.100s\" host \"%.100s\" addr \"%.100s\"",
199 __func__, cuser, resolvedname, ipaddr);
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000200 return 0;
djm@openbsd.org5191df92014-12-23 22:42:48 +0000201 }
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000202 lookup = resolvedname;
203 }
djm@openbsd.org5191df92014-12-23 22:42:48 +0000204 debug2("%s: access allowed by auth_rhosts2", __func__);
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000205
Damien Millerc1583312010-08-05 13:04:50 +1000206 if (key_is_cert(key) &&
207 key_cert_check_authority(key, 1, 0, lookup, &reason)) {
208 error("%s", reason);
209 auth_debug_add("%s", reason);
210 return 0;
211 }
212
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000213 host_status = check_key_in_hostfiles(pw, key, lookup,
214 _PATH_SSH_SYSTEM_HOSTFILE,
215 options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
216
217 /* backward compat if no key has been found. */
Damien Millerc1583312010-08-05 13:04:50 +1000218 if (host_status == HOST_NEW) {
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000219 host_status = check_key_in_hostfiles(pw, key, lookup,
220 _PATH_SSH_SYSTEM_HOSTFILE2,
221 options.ignore_user_known_hosts ? NULL :
222 _PATH_SSH_USER_HOSTFILE2);
Damien Millerc1583312010-08-05 13:04:50 +1000223 }
224
225 if (host_status == HOST_OK) {
226 if (key_is_cert(key)) {
djm@openbsd.org9ce86c92015-01-28 22:36:00 +0000227 if ((fp = sshkey_fingerprint(key->cert->signature_key,
228 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
229 fatal("%s: sshkey_fingerprint fail", __func__);
Damien Millerc1583312010-08-05 13:04:50 +1000230 verbose("Accepted certificate ID \"%s\" signed by "
231 "%s CA %s from %s@%s", key->cert->key_id,
232 key_type(key->cert->signature_key), fp,
233 cuser, lookup);
234 } else {
djm@openbsd.org9ce86c92015-01-28 22:36:00 +0000235 if ((fp = sshkey_fingerprint(key,
236 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
237 fatal("%s: sshkey_fingerprint fail", __func__);
Damien Millerc1583312010-08-05 13:04:50 +1000238 verbose("Accepted %s public key %s from %s@%s",
239 key_type(key), fp, cuser, lookup);
240 }
Darren Tuckera627d422013-06-02 07:31:17 +1000241 free(fp);
Damien Millerc1583312010-08-05 13:04:50 +1000242 }
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000243
244 return (host_status == HOST_OK);
245}
246
247Authmethod method_hostbased = {
248 "hostbased",
249 userauth_hostbased,
250 &options.hostbased_authentication
251};