1 /* $OpenBSD: auth2-hostbased.c,v 1.11 2006/08/03 03:34:41 deraadt Exp $ */ 2 /* 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" 27 28 #include <sys/types.h> 29 30 #include <pwd.h> 31 #include <string.h> 32 #include <stdarg.h> 33 34 #include "xmalloc.h" 35 #include "ssh2.h" 36 #include "packet.h" 37 #include "buffer.h" 38 #include "log.h" 39 #include "servconf.h" 40 #include "compat.h" 41 #include "key.h" 42 #include "hostfile.h" 43 #include "auth.h" 44 #include "canohost.h" 45 #ifdef GSSAPI 46 #include "ssh-gss.h" 47 #endif 48 #include "monitor_wrap.h" 49 #include "pathnames.h" 50 51 /* import */ 52 extern ServerOptions options; 53 extern u_char *session_id2; 54 extern u_int session_id2_len; 55 56 static int 57 userauth_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 */ 89 logit("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 (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; 125 126 buffer_free(&b); 127 done: 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 */ 140 int 141 hostbased_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; 147 148 resolvedname = get_canonical_hostname(options.use_dns); 149 ipaddr = get_remote_ipaddr(); 150 151 debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s", 152 chost, resolvedname, ipaddr); 153 154 if (options.hostbased_uses_name_from_packet_only) { 155 if (auth_rhosts2(pw, cuser, chost, chost) == 0) 156 return 0; 157 lookup = chost; 158 } else { 159 if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') { 160 debug2("stripping trailing dot from chost %s", chost); 161 chost[len - 1] = '\0'; 162 } 163 if (strcasecmp(resolvedname, chost) != 0) 164 logit("userauth_hostbased mismatch: " 165 "client sends %s, but we resolve %s to %s", 166 chost, ipaddr, resolvedname); 167 if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) 168 return 0; 169 lookup = resolvedname; 170 } 171 debug2("userauth_hostbased: access allowed by auth_rhosts2"); 172 173 host_status = check_key_in_hostfiles(pw, key, lookup, 174 _PATH_SSH_SYSTEM_HOSTFILE, 175 options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE); 176 177 /* backward compat if no key has been found. */ 178 if (host_status == HOST_NEW) 179 host_status = check_key_in_hostfiles(pw, key, lookup, 180 _PATH_SSH_SYSTEM_HOSTFILE2, 181 options.ignore_user_known_hosts ? NULL : 182 _PATH_SSH_USER_HOSTFILE2); 183 184 return (host_status == HOST_OK); 185 } 186 187 Authmethod method_hostbased = { 188 "hostbased", 189 userauth_hostbased, 190 &options.hostbased_authentication 191 }; 192