auth2-hostbased.c revision 1.4.4.1
1 /* $NetBSD: auth2-hostbased.c,v 1.4.4.1 2017/08/15 05:27:51 snj Exp $ */ 2 /* $OpenBSD: auth2-hostbased.c,v 1.26 2016/03/07 19:02:43 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 1.4.4.1 2017/08/15 05:27:51 snj 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 "misc.h" 41 #include "servconf.h" 42 #include "compat.h" 43 #include "key.h" 44 #include "hostfile.h" 45 #include "auth.h" 46 #include "canohost.h" 47 #ifdef GSSAPI 48 #include "ssh-gss.h" 49 #endif 50 #include "monitor_wrap.h" 51 #include "pathnames.h" 52 #include "match.h" 53 54 /* import */ 55 extern ServerOptions options; 56 extern u_char *session_id2; 57 extern u_int session_id2_len; 58 59 static int 60 userauth_hostbased(Authctxt *authctxt) 61 { 62 Buffer b; 63 Key *key = NULL; 64 char *pkalg, *cuser, *chost, *service; 65 u_char *pkblob, *sig; 66 u_int alen, blen, slen; 67 int pktype; 68 int authenticated = 0; 69 70 if (!authctxt->valid) { 71 debug2("userauth_hostbased: disabled because of invalid user"); 72 return 0; 73 } 74 pkalg = packet_get_string(&alen); 75 pkblob = packet_get_string(&blen); 76 chost = packet_get_string(NULL); 77 cuser = packet_get_string(NULL); 78 sig = packet_get_string(&slen); 79 80 debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d", 81 cuser, chost, pkalg, slen); 82 #ifdef DEBUG_PK 83 debug("signature:"); 84 buffer_init(&b); 85 buffer_append(&b, sig, slen); 86 buffer_dump(&b); 87 buffer_free(&b); 88 #endif 89 pktype = key_type_from_name(pkalg); 90 if (pktype == KEY_UNSPEC) { 91 /* this is perfectly legal */ 92 logit("userauth_hostbased: unsupported " 93 "public key algorithm: %s", pkalg); 94 goto done; 95 } 96 key = key_from_blob(pkblob, blen); 97 if (key == NULL) { 98 error("userauth_hostbased: cannot decode key: %s", pkalg); 99 goto done; 100 } 101 if (key->type != pktype) { 102 error("userauth_hostbased: type mismatch for decoded key " 103 "(received %d, expected %d)", key->type, pktype); 104 goto done; 105 } 106 if (key_type_plain(key->type) == KEY_RSA && 107 (datafellows & SSH_BUG_RSASIGMD5) != 0) { 108 error("Refusing RSA key because peer uses unsafe " 109 "signature format"); 110 goto done; 111 } 112 if (match_pattern_list(sshkey_ssh_name(key), 113 options.hostbased_key_types, 0) != 1) { 114 logit("%s: key type %s not in HostbasedAcceptedKeyTypes", 115 __func__, sshkey_type(key)); 116 goto done; 117 } 118 119 service = datafellows & SSH_BUG_HBSERVICE ? __UNCONST("ssh-userauth") : 120 authctxt->service; 121 buffer_init(&b); 122 buffer_put_string(&b, session_id2, session_id2_len); 123 /* reconstruct packet */ 124 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); 125 buffer_put_cstring(&b, authctxt->user); 126 buffer_put_cstring(&b, service); 127 buffer_put_cstring(&b, "hostbased"); 128 buffer_put_string(&b, pkalg, alen); 129 buffer_put_string(&b, pkblob, blen); 130 buffer_put_cstring(&b, chost); 131 buffer_put_cstring(&b, cuser); 132 #ifdef DEBUG_PK 133 buffer_dump(&b); 134 #endif 135 136 pubkey_auth_info(authctxt, key, 137 "client user \"%.100s\", client host \"%.100s\"", cuser, chost); 138 139 /* test for allowed key and correct signature */ 140 authenticated = 0; 141 if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) && 142 PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b), 143 buffer_len(&b))) == 1) 144 authenticated = 1; 145 146 buffer_free(&b); 147 done: 148 debug2("userauth_hostbased: authenticated %d", authenticated); 149 if (key != NULL) 150 key_free(key); 151 free(pkalg); 152 free(pkblob); 153 free(cuser); 154 free(chost); 155 free(sig); 156 return authenticated; 157 } 158 159 /* return 1 if given hostkey is allowed */ 160 int 161 hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost, 162 Key *key) 163 { 164 struct ssh *ssh = active_state; /* XXX */ 165 const char *resolvedname, *ipaddr, *lookup, *reason; 166 HostStatus host_status; 167 int len; 168 char *fp; 169 170 if (auth_key_is_revoked(key)) 171 return 0; 172 173 resolvedname = auth_get_canonical_hostname(ssh, options.use_dns); 174 ipaddr = ssh_remote_ipaddr(ssh); 175 176 debug2("%s: chost %s resolvedname %s ipaddr %s", __func__, 177 chost, resolvedname, ipaddr); 178 179 if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') { 180 debug2("stripping trailing dot from chost %s", chost); 181 chost[len - 1] = '\0'; 182 } 183 184 if (options.hostbased_uses_name_from_packet_only) { 185 if (auth_rhosts2(pw, cuser, chost, chost) == 0) { 186 debug2("%s: auth_rhosts2 refused " 187 "user \"%.100s\" host \"%.100s\" (from packet)", 188 __func__, cuser, chost); 189 return 0; 190 } 191 lookup = chost; 192 } else { 193 if (strcasecmp(resolvedname, chost) != 0) 194 logit("userauth_hostbased mismatch: " 195 "client sends %s, but we resolve %s to %s", 196 chost, ipaddr, resolvedname); 197 if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) { 198 debug2("%s: auth_rhosts2 refused " 199 "user \"%.100s\" host \"%.100s\" addr \"%.100s\"", 200 __func__, cuser, resolvedname, ipaddr); 201 return 0; 202 } 203 lookup = resolvedname; 204 } 205 debug2("%s: access allowed by auth_rhosts2", __func__); 206 207 if (key_is_cert(key) && 208 key_cert_check_authority(key, 1, 0, lookup, &reason)) { 209 error("%s", reason); 210 auth_debug_add("%s", reason); 211 return 0; 212 } 213 214 host_status = check_key_in_hostfiles(pw, key, lookup, 215 _PATH_SSH_SYSTEM_HOSTFILE, 216 options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE); 217 218 /* backward compat if no key has been found. */ 219 if (host_status == HOST_NEW) { 220 host_status = check_key_in_hostfiles(pw, key, lookup, 221 _PATH_SSH_SYSTEM_HOSTFILE2, 222 options.ignore_user_known_hosts ? NULL : 223 _PATH_SSH_USER_HOSTFILE2); 224 } 225 226 if (host_status == HOST_OK) { 227 if (key_is_cert(key)) { 228 if ((fp = sshkey_fingerprint(key->cert->signature_key, 229 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 230 fatal("%s: sshkey_fingerprint fail", __func__); 231 verbose("Accepted certificate ID \"%s\" signed by " 232 "%s CA %s from %s@%s", key->cert->key_id, 233 key_type(key->cert->signature_key), fp, 234 cuser, lookup); 235 } else { 236 if ((fp = sshkey_fingerprint(key, 237 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 238 fatal("%s: sshkey_fingerprint fail", __func__); 239 verbose("Accepted %s public key %s from %s@%s", 240 key_type(key), fp, cuser, lookup); 241 } 242 free(fp); 243 } 244 245 return (host_status == HOST_OK); 246 } 247 248 Authmethod method_hostbased = { 249 "hostbased", 250 userauth_hostbased, 251 &options.hostbased_authentication 252 }; 253
Indexes created Sun Sep 20 00:26:38 UTC 2026