auth2-hostbased.c revision 126274
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#include "includes.h" 26RCSID("$OpenBSD: auth2-hostbased.c,v 1.6 2004/01/19 21:25:15 markus Exp $"); 27 28#include "ssh2.h" 29#include "xmalloc.h" 30#include "packet.h" 31#include "buffer.h" 32#include "log.h" 33#include "servconf.h" 34#include "compat.h" 35#include "bufaux.h" 36#include "auth.h" 37#include "key.h" 38#include "canohost.h" 39#include "monitor_wrap.h" 40#include "pathnames.h" 41 42/* import */ 43extern ServerOptions options; 44extern u_char *session_id2; 45extern u_int session_id2_len; 46 47static int 48userauth_hostbased(Authctxt *authctxt) 49{ 50 Buffer b; 51 Key *key = NULL; 52 char *pkalg, *cuser, *chost, *service; 53 u_char *pkblob, *sig; 54 u_int alen, blen, slen; 55 int pktype; 56 int authenticated = 0; 57 58 if (!authctxt->valid) { 59 debug2("userauth_hostbased: disabled because of invalid user"); 60 return 0; 61 } 62 pkalg = packet_get_string(&alen); 63 pkblob = packet_get_string(&blen); 64 chost = packet_get_string(NULL); 65 cuser = packet_get_string(NULL); 66 sig = packet_get_string(&slen); 67 68 debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d", 69 cuser, chost, pkalg, slen); 70#ifdef DEBUG_PK 71 debug("signature:"); 72 buffer_init(&b); 73 buffer_append(&b, sig, slen); 74 buffer_dump(&b); 75 buffer_free(&b); 76#endif 77 pktype = key_type_from_name(pkalg); 78 if (pktype == KEY_UNSPEC) { 79 /* this is perfectly legal */ 80 logit("userauth_hostbased: unsupported " 81 "public key algorithm: %s", pkalg); 82 goto done; 83 } 84 key = key_from_blob(pkblob, blen); 85 if (key == NULL) { 86 error("userauth_hostbased: cannot decode key: %s", pkalg); 87 goto done; 88 } 89 if (key->type != pktype) { 90 error("userauth_hostbased: type mismatch for decoded key " 91 "(received %d, expected %d)", key->type, pktype); 92 goto done; 93 } 94 service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" : 95 authctxt->service; 96 buffer_init(&b); 97 buffer_put_string(&b, session_id2, session_id2_len); 98 /* reconstruct packet */ 99 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); 100 buffer_put_cstring(&b, authctxt->user); 101 buffer_put_cstring(&b, service); 102 buffer_put_cstring(&b, "hostbased"); 103 buffer_put_string(&b, pkalg, alen); 104 buffer_put_string(&b, pkblob, blen); 105 buffer_put_cstring(&b, chost); 106 buffer_put_cstring(&b, cuser); 107#ifdef DEBUG_PK 108 buffer_dump(&b); 109#endif 110 /* test for allowed key and correct signature */ 111 authenticated = 0; 112 if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) && 113 PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b), 114 buffer_len(&b))) == 1) 115 authenticated = 1; 116 117 buffer_free(&b); 118done: 119 debug2("userauth_hostbased: authenticated %d", authenticated); 120 if (key != NULL) 121 key_free(key); 122 xfree(pkalg); 123 xfree(pkblob); 124 xfree(cuser); 125 xfree(chost); 126 xfree(sig); 127 return authenticated; 128} 129 130/* return 1 if given hostkey is allowed */ 131int 132hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost, 133 Key *key) 134{ 135 const char *resolvedname, *ipaddr, *lookup; 136 HostStatus host_status; 137 int len; 138 139 resolvedname = get_canonical_hostname(options.use_dns); 140 ipaddr = get_remote_ipaddr(); 141 142 debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s", 143 chost, resolvedname, ipaddr); 144 145 if (options.hostbased_uses_name_from_packet_only) { 146 if (auth_rhosts2(pw, cuser, chost, chost) == 0) 147 return 0; 148 lookup = chost; 149 } else { 150 if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') { 151 debug2("stripping trailing dot from chost %s", chost); 152 chost[len - 1] = '\0'; 153 } 154 if (strcasecmp(resolvedname, chost) != 0) 155 logit("userauth_hostbased mismatch: " 156 "client sends %s, but we resolve %s to %s", 157 chost, ipaddr, resolvedname); 158 if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) 159 return 0; 160 lookup = resolvedname; 161 } 162 debug2("userauth_hostbased: access allowed by auth_rhosts2"); 163 164 host_status = check_key_in_hostfiles(pw, key, lookup, 165 _PATH_SSH_SYSTEM_HOSTFILE, 166 options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE); 167 168 /* backward compat if no key has been found. */ 169 if (host_status == HOST_NEW) 170 host_status = check_key_in_hostfiles(pw, key, lookup, 171 _PATH_SSH_SYSTEM_HOSTFILE2, 172 options.ignore_user_known_hosts ? NULL : 173 _PATH_SSH_USER_HOSTFILE2); 174 175 return (host_status == HOST_OK); 176} 177 178Authmethod method_hostbased = { 179 "hostbased", 180 userauth_hostbased, 181 &options.hostbased_authentication 182}; 183