blob: 041051c53c7265af12976ca20499ee9dde6211fd [file] [log] [blame]
Damien Millera1d03a52008-07-17 18:57:19 +10001/* $OpenBSD: auth2-hostbased.c,v 1.12 2008/07/17 08:51:07 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"
39#include "servconf.h"
40#include "compat.h"
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000041#include "key.h"
Damien Millerd7834352006-08-05 12:39:39 +100042#include "hostfile.h"
43#include "auth.h"
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000044#include "canohost.h"
Damien Millerd7834352006-08-05 12:39:39 +100045#ifdef GSSAPI
46#include "ssh-gss.h"
47#endif
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000048#include "monitor_wrap.h"
49#include "pathnames.h"
50
51/* import */
52extern ServerOptions options;
53extern u_char *session_id2;
Darren Tucker502d3842003-06-28 12:38:01 +100054extern u_int session_id2_len;
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000055
56static int
57userauth_hostbased(Authctxt *authctxt)
58{
59 Buffer b;
60 Key *key = NULL;
61 char *pkalg, *cuser, *chost, *service;
62 u_char *pkblob, *sig;
63 u_int alen, blen, slen;
64 int pktype;
65 int authenticated = 0;
66
67 if (!authctxt->valid) {
68 debug2("userauth_hostbased: disabled because of invalid user");
69 return 0;
70 }
71 pkalg = packet_get_string(&alen);
72 pkblob = packet_get_string(&blen);
73 chost = packet_get_string(NULL);
74 cuser = packet_get_string(NULL);
75 sig = packet_get_string(&slen);
76
77 debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d",
78 cuser, chost, pkalg, slen);
79#ifdef DEBUG_PK
80 debug("signature:");
81 buffer_init(&b);
82 buffer_append(&b, sig, slen);
83 buffer_dump(&b);
84 buffer_free(&b);
85#endif
86 pktype = key_type_from_name(pkalg);
87 if (pktype == KEY_UNSPEC) {
88 /* this is perfectly legal */
Damien Miller996acd22003-04-09 20:59:48 +100089 logit("userauth_hostbased: unsupported "
Ben Lindstrom855bf3a2002-06-06 20:27:55 +000090 "public key algorithm: %s", pkalg);
91 goto done;
92 }
93 key = key_from_blob(pkblob, blen);
94 if (key == NULL) {
95 error("userauth_hostbased: cannot decode key: %s", pkalg);
96 goto done;
97 }
98 if (key->type != pktype) {
99 error("userauth_hostbased: type mismatch for decoded key "
100 "(received %d, expected %d)", key->type, pktype);
101 goto done;
102 }
103 service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
104 authctxt->service;
105 buffer_init(&b);
106 buffer_put_string(&b, session_id2, session_id2_len);
107 /* reconstruct packet */
108 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
109 buffer_put_cstring(&b, authctxt->user);
110 buffer_put_cstring(&b, service);
111 buffer_put_cstring(&b, "hostbased");
112 buffer_put_string(&b, pkalg, alen);
113 buffer_put_string(&b, pkblob, blen);
114 buffer_put_cstring(&b, chost);
115 buffer_put_cstring(&b, cuser);
116#ifdef DEBUG_PK
117 buffer_dump(&b);
118#endif
119 /* test for allowed key and correct signature */
120 authenticated = 0;
121 if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
122 PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
123 buffer_len(&b))) == 1)
124 authenticated = 1;
125
Damien Millerfb1310e2004-01-21 11:02:50 +1100126 buffer_free(&b);
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000127done:
128 debug2("userauth_hostbased: authenticated %d", authenticated);
129 if (key != NULL)
130 key_free(key);
131 xfree(pkalg);
132 xfree(pkblob);
133 xfree(cuser);
134 xfree(chost);
135 xfree(sig);
136 return authenticated;
137}
138
139/* return 1 if given hostkey is allowed */
140int
141hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
142 Key *key)
143{
144 const char *resolvedname, *ipaddr, *lookup;
145 HostStatus host_status;
146 int len;
147
Damien Miller3a961dc2003-06-03 10:25:48 +1000148 resolvedname = get_canonical_hostname(options.use_dns);
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000149 ipaddr = get_remote_ipaddr();
150
151 debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s",
152 chost, resolvedname, ipaddr);
153
Damien Millera1d03a52008-07-17 18:57:19 +1000154 if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
155 debug2("stripping trailing dot from chost %s", chost);
156 chost[len - 1] = '\0';
157 }
158
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000159 if (options.hostbased_uses_name_from_packet_only) {
160 if (auth_rhosts2(pw, cuser, chost, chost) == 0)
161 return 0;
162 lookup = chost;
163 } else {
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000164 if (strcasecmp(resolvedname, chost) != 0)
Damien Miller996acd22003-04-09 20:59:48 +1000165 logit("userauth_hostbased mismatch: "
Ben Lindstrom855bf3a2002-06-06 20:27:55 +0000166 "client sends %s, but we resolve %s to %s",
167 chost, ipaddr, resolvedname);
168 if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0)
169 return 0;
170 lookup = resolvedname;
171 }
172 debug2("userauth_hostbased: access allowed by auth_rhosts2");
173
174 host_status = check_key_in_hostfiles(pw, key, lookup,
175 _PATH_SSH_SYSTEM_HOSTFILE,
176 options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
177
178 /* backward compat if no key has been found. */
179 if (host_status == HOST_NEW)
180 host_status = check_key_in_hostfiles(pw, key, lookup,
181 _PATH_SSH_SYSTEM_HOSTFILE2,
182 options.ignore_user_known_hosts ? NULL :
183 _PATH_SSH_USER_HOSTFILE2);
184
185 return (host_status == HOST_OK);
186}
187
188Authmethod method_hostbased = {
189 "hostbased",
190 userauth_hostbased,
191 &options.hostbased_authentication
192};