1 /* $NetBSD: auth2-hostbased.c,v 1.2 2009/06/07 22:38:46 christos Exp $ */ 2 /* $OpenBSD: auth2-hostbased.c,v 1.12 2008/07/17 08:51:07 djm Exp $ */ 3 /* 4 * Copyright (c) 2000 Markus Friedl. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 __RCSID("$NetBSD: auth2-hostbased.c,v 1.2 2009/06/07 22:38:46 christos Exp $"); 29 #include <sys/types.h> 30 31 #include <pwd.h> 32 #include <string.h> 33 #include <stdarg.h> 34 35 #include "xmalloc.h" 36 #include "ssh2.h" 37 #include "packet.h" 38 #include "buffer.h" 39 #include "log.h" 40 #include "servconf.h" 41 #include "compat.h" 42 #include "key.h" 43 #include "hostfile.h" 44 #include "auth.h" 45 #include "canohost.h" 46 #ifdef GSSAPI 47 #include "ssh-gss.h" 48 #endif 49 #include "monitor_wrap.h" 50 #include "pathnames.h" 51 52 /* import */ 53 extern ServerOptions options; 54 extern u_char *session_id2; 55 extern u_int session_id2_len; 56 57 static int 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->valid) { 69 debug2("userauth_hostbased: disabled because of invalid user"); 70 return 0; 71 } 72 pkalg = packet_get_string(&alen); 73 pkblob = packet_get_string(&blen); 74 chost = packet_get_string(NULL); 75 cuser = packet_get_string(NULL); 76 sig = packet_get_string(&slen); 77 78 debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d", 79 cuser, chost, pkalg, slen); 80 #ifdef DEBUG_PK 81 debug("signature:"); 82 buffer_init(&b); 83 buffer_append(&b, sig, slen); 84 buffer_dump(&b); 85 buffer_free(&b); 86 #endif 87 pktype = key_type_from_name(pkalg); 88 if (pktype == KEY_UNSPEC) { 89 /* this is perfectly legal */ 90 logit("userauth_hostbased: unsupported " 91 "public key algorithm: %s", pkalg); 92 goto done; 93 } 94 key = key_from_blob(pkblob, blen); 95 if (key == NULL) { 96 error("userauth_hostbased: cannot decode key: %s", pkalg); 97 goto done; 98 } 99 if (key->type != pktype) { 100 error("userauth_hostbased: type mismatch for decoded key " 101 "(received %d, expected %d)", key->type, pktype); 102 goto done; 103 } 104 service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" : 105 authctxt->service; 106 buffer_init(&b); 107 buffer_put_string(&b, session_id2, session_id2_len); 108 /* reconstruct packet */ 109 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); 110 buffer_put_cstring(&b, authctxt->user); 111 buffer_put_cstring(&b, service); 112 buffer_put_cstring(&b, "hostbased"); 113 buffer_put_string(&b, pkalg, alen); 114 buffer_put_string(&b, pkblob, blen); 115 buffer_put_cstring(&b, chost); 116 buffer_put_cstring(&b, cuser); 117 #ifdef DEBUG_PK 118 buffer_dump(&b); 119 #endif 120 /* test for allowed key and correct signature */ 121 authenticated = 0; 122 if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) && 123 PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b), 124 buffer_len(&b))) == 1) 125 authenticated = 1; 126 127 buffer_free(&b); 128 done: 129 debug2("userauth_hostbased: authenticated %d", authenticated); 130 if (key != NULL) 131 key_free(key); 132 xfree(pkalg); 133 xfree(pkblob); 134 xfree(cuser); 135 xfree(chost); 136 xfree(sig); 137 return authenticated; 138 } 139 140 /* return 1 if given hostkey is allowed */ 141 int 142 hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost, 143 Key *key) 144 { 145 const char *resolvedname, *ipaddr, *lookup; 146 HostStatus host_status; 147 int len; 148 149 resolvedname = get_canonical_hostname(options.use_dns); 150 ipaddr = get_remote_ipaddr(); 151 152 debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s", 153 chost, resolvedname, ipaddr); 154 155 if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') { 156 debug2("stripping trailing dot from chost %s", chost); 157 chost[len - 1] = '\0'; 158 } 159 160 if (options.hostbased_uses_name_from_packet_only) { 161 if (auth_rhosts2(pw, cuser, chost, chost) == 0) 162 return 0; 163 lookup = chost; 164 } else { 165 if (strcasecmp(resolvedname, chost) != 0) 166 logit("userauth_hostbased mismatch: " 167 "client sends %s, but we resolve %s to %s", 168 chost, ipaddr, resolvedname); 169 if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) 170 return 0; 171 lookup = resolvedname; 172 } 173 debug2("userauth_hostbased: access allowed by auth_rhosts2"); 174 175 host_status = check_key_in_hostfiles(pw, key, lookup, 176 _PATH_SSH_SYSTEM_HOSTFILE, 177 options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE); 178 179 /* backward compat if no key has been found. */ 180 if (host_status == HOST_NEW) 181 host_status = check_key_in_hostfiles(pw, key, lookup, 182 _PATH_SSH_SYSTEM_HOSTFILE2, 183 options.ignore_user_known_hosts ? NULL : 184 _PATH_SSH_USER_HOSTFILE2); 185 186 return (host_status == HOST_OK); 187 } 188 189 Authmethod method_hostbased = { 190 "hostbased", 191 userauth_hostbased, 192 &options.hostbased_authentication 193 }; 194