1 /* 2 * Copyright (c) 2000 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 /* 25 * Copyright 2007 Sun Microsystems, Inc. All rights reserved. 26 * Use is subject to license terms. 27 */ 28 29 #include "includes.h" 30 RCSID("$OpenBSD: auth2-hostbased.c,v 1.2 2002/05/31 11:35:15 markus Exp $"); 31 32 #pragma ident "%Z%%M% %I% %E% SMI" 33 34 #include "ssh2.h" 35 #include "xmalloc.h" 36 #include "packet.h" 37 #include "buffer.h" 38 #include "log.h" 39 #include "servconf.h" 40 #include "compat.h" 41 #include "bufaux.h" 42 #include "auth.h" 43 44 #ifdef USE_PAM 45 #include "auth-pam.h" 46 #endif /* USE_PAM */ 47 48 #include "key.h" 49 #include "canohost.h" 50 #include "pathnames.h" 51 52 /* import */ 53 extern ServerOptions options; 54 extern u_char *session_id2; 55 extern int session_id2_len; 56 57 static void 58 userauth_hostbased(Authctxt *authctxt) 59 { 60 Buffer b; 61 Key *key = NULL; 62 char *pkalg, *cuser, *chost, *service; 63 u_char *pkblob, *sig; 64 u_int alen, blen, slen; 65 int pktype; 66 int authenticated = 0; 67 68 if (!authctxt || !authctxt->method) 69 fatal("%s: missing context", __func__); 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 */ 89 log("userauth_hostbased: unsupported " 90 "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 (hostbased_key_allowed(authctxt->pw, cuser, chost, key) && 122 key_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1) 123 authenticated = 1; 124 125 buffer_clear(&b); 126 done: 127 /* 128 * XXX TODO: Add config options for specifying users for whom 129 * this userauth is insufficient and what userauths 130 * may continue. 131 * 132 * NOTE: do_pam_non_initial_userauth() does this for 133 * users with expired passwords. 134 */ 135 #ifdef USE_PAM 136 if (authenticated) { 137 authctxt->cuser = cuser; 138 if (!do_pam_non_initial_userauth(authctxt)) 139 authenticated = 0; 140 /* Make sure nobody else will use this pointer since we are 141 * going to free that string. */ 142 authctxt->cuser = NULL; 143 } 144 #endif /* USE_PAM */ 145 146 if (authenticated) 147 authctxt->method->authenticated = 1; 148 149 debug2("userauth_hostbased: authenticated %d", authenticated); 150 if (key != NULL) 151 key_free(key); 152 xfree(pkalg); 153 xfree(pkblob); 154 xfree(cuser); 155 xfree(chost); 156 xfree(sig); 157 return; 158 } 159 160 /* return 1 if given hostkey is allowed */ 161 int 162 hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost, 163 Key *key) 164 { 165 const char *resolvedname, *ipaddr, *lookup; 166 HostStatus host_status; 167 int len; 168 169 resolvedname = get_canonical_hostname(options.verify_reverse_mapping); 170 ipaddr = get_remote_ipaddr(); 171 172 debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s", 173 chost, resolvedname, ipaddr); 174 175 if (pw == NULL) 176 return 0; 177 178 if (options.hostbased_uses_name_from_packet_only) { 179 if (auth_rhosts2(pw, cuser, chost, chost) == 0) 180 return 0; 181 lookup = chost; 182 } else { 183 if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') { 184 debug2("stripping trailing dot from chost %s", chost); 185 chost[len - 1] = '\0'; 186 } 187 if (strcasecmp(resolvedname, chost) != 0) 188 log("userauth_hostbased mismatch: " 189 "client sends %s, but we resolve %s to %s", 190 chost, ipaddr, resolvedname); 191 if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) 192 return 0; 193 lookup = resolvedname; 194 } 195 debug2("userauth_hostbased: access allowed by auth_rhosts2"); 196 197 host_status = check_key_in_hostfiles(pw, key, lookup, 198 _PATH_SSH_SYSTEM_HOSTFILE, 199 options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE); 200 201 /* backward compat if no key has been found. */ 202 if (host_status == HOST_NEW) 203 host_status = check_key_in_hostfiles(pw, key, lookup, 204 _PATH_SSH_SYSTEM_HOSTFILE2, 205 options.ignore_user_known_hosts ? NULL : 206 _PATH_SSH_USER_HOSTFILE2); 207 208 return (host_status == HOST_OK); 209 } 210 211 Authmethod method_hostbased = { 212 "hostbased", 213 &options.hostbased_authentication, 214 userauth_hostbased, 215 NULL, /* no abandon function */ 216 NULL, NULL, /* method data and hist data */ 217 0, /* is not initial userauth */ 218 0, 0, 0, /* counters */ 219 0, 0, 0, 0, 0, 0 /* state */ 220 }; 221