1 /* $OpenBSD: auth2-gss.c,v 1.15 2006/08/03 03:34:41 deraadt Exp $ */ 2 3 /* 4 * Copyright (c) 2001-2003 Simon Wilkinson. 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 <sys/types.h> 28 29 #include "xmalloc.h" 30 #include "key.h" 31 #include "hostfile.h" 32 #include "auth.h" 33 #include "ssh2.h" 34 #include "log.h" 35 #include "dispatch.h" 36 #include "buffer.h" 37 #include "servconf.h" 38 #include "packet.h" 39 #include "ssh-gss.h" 40 #include "monitor_wrap.h" 41 42 extern ServerOptions options; 43 44 static void input_gssapi_token(int type, u_int32_t plen, void *ctxt); 45 static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt); 46 static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt); 47 static void input_gssapi_errtok(int, u_int32_t, void *); 48 49 /* 50 * We only support those mechanisms that we know about (ie ones that we know 51 * how to check local user kuserok and the like) 52 */ 53 static int 54 userauth_gssapi(Authctxt *authctxt) 55 { 56 gss_OID_desc goid = {0, NULL}; 57 Gssctxt *ctxt = NULL; 58 int mechs; 59 gss_OID_set supported; 60 int present; 61 OM_uint32 ms; 62 u_int len; 63 u_char *doid = NULL; 64 65 if (!authctxt->valid || authctxt->user == NULL) 66 return (0); 67 68 mechs = packet_get_int(); 69 if (mechs == 0) { 70 debug("Mechanism negotiation is not supported"); 71 return (0); 72 } 73 74 ssh_gssapi_supported_oids(&supported); 75 do { 76 mechs--; 77 78 if (doid) 79 xfree(doid); 80 81 present = 0; 82 doid = packet_get_string(&len); 83 84 if (len > 2 && doid[0] == SSH_GSS_OIDTYPE && 85 doid[1] == len - 2) { 86 goid.elements = doid + 2; 87 goid.length = len - 2; 88 gss_test_oid_set_member(&ms, &goid, supported, 89 &present); 90 } else { 91 logit("Badly formed OID received"); 92 } 93 } while (mechs > 0 && !present); 94 95 gss_release_oid_set(&ms, &supported); 96 97 if (!present) { 98 xfree(doid); 99 return (0); 100 } 101 102 if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) { 103 if (ctxt != NULL) 104 ssh_gssapi_delete_ctx(&ctxt); 105 xfree(doid); 106 return (0); 107 } 108 109 authctxt->methoddata = (void *)ctxt; 110 111 packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE); 112 113 /* Return the OID that we received */ 114 packet_put_string(doid, len); 115 116 packet_send(); 117 xfree(doid); 118 119 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); 120 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); 121 authctxt->postponed = 1; 122 123 return (0); 124 } 125 126 static void 127 input_gssapi_token(int type, u_int32_t plen, void *ctxt) 128 { 129 Authctxt *authctxt = ctxt; 130 Gssctxt *gssctxt; 131 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 132 gss_buffer_desc recv_tok; 133 OM_uint32 maj_status, min_status, flags; 134 u_int len; 135 136 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 137 fatal("No authentication or GSSAPI context"); 138 139 gssctxt = authctxt->methoddata; 140 recv_tok.value = packet_get_string(&len); 141 recv_tok.length = len; /* u_int vs. size_t */ 142 143 packet_check_eom(); 144 145 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 146 &send_tok, &flags)); 147 148 xfree(recv_tok.value); 149 150 if (GSS_ERROR(maj_status)) { 151 if (send_tok.length != 0) { 152 packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK); 153 packet_put_string(send_tok.value, send_tok.length); 154 packet_send(); 155 } 156 authctxt->postponed = 0; 157 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 158 userauth_finish(authctxt, 0, "gssapi-with-mic"); 159 } else { 160 if (send_tok.length != 0) { 161 packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN); 162 packet_put_string(send_tok.value, send_tok.length); 163 packet_send(); 164 } 165 if (maj_status == GSS_S_COMPLETE) { 166 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 167 if (flags & GSS_C_INTEG_FLAG) 168 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, 169 &input_gssapi_mic); 170 else 171 dispatch_set( 172 SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, 173 &input_gssapi_exchange_complete); 174 } 175 } 176 177 gss_release_buffer(&min_status, &send_tok); 178 } 179 180 static void 181 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt) 182 { 183 Authctxt *authctxt = ctxt; 184 Gssctxt *gssctxt; 185 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 186 gss_buffer_desc recv_tok; 187 OM_uint32 maj_status; 188 u_int len; 189 190 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 191 fatal("No authentication or GSSAPI context"); 192 193 gssctxt = authctxt->methoddata; 194 recv_tok.value = packet_get_string(&len); 195 recv_tok.length = len; 196 197 packet_check_eom(); 198 199 /* Push the error token into GSSAPI to see what it says */ 200 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 201 &send_tok, NULL)); 202 203 xfree(recv_tok.value); 204 205 /* We can't return anything to the client, even if we wanted to */ 206 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 207 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 208 209 /* The client will have already moved on to the next auth */ 210 211 gss_release_buffer(&maj_status, &send_tok); 212 } 213 214 /* 215 * This is called when the client thinks we've completed authentication. 216 * It should only be enabled in the dispatch handler by the function above, 217 * which only enables it once the GSSAPI exchange is complete. 218 */ 219 220 static void 221 input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt) 222 { 223 Authctxt *authctxt = ctxt; 224 Gssctxt *gssctxt; 225 int authenticated; 226 227 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 228 fatal("No authentication or GSSAPI context"); 229 230 gssctxt = authctxt->methoddata; 231 232 /* 233 * We don't need to check the status, because we're only enabled in 234 * the dispatcher once the exchange is complete 235 */ 236 237 packet_check_eom(); 238 239 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 240 241 authctxt->postponed = 0; 242 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 243 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 244 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 245 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 246 userauth_finish(authctxt, authenticated, "gssapi-with-mic"); 247 } 248 249 static void 250 input_gssapi_mic(int type, u_int32_t plen, void *ctxt) 251 { 252 Authctxt *authctxt = ctxt; 253 Gssctxt *gssctxt; 254 int authenticated = 0; 255 Buffer b; 256 gss_buffer_desc mic, gssbuf; 257 u_int len; 258 259 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 260 fatal("No authentication or GSSAPI context"); 261 262 gssctxt = authctxt->methoddata; 263 264 mic.value = packet_get_string(&len); 265 mic.length = len; 266 267 ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, 268 "gssapi-with-mic"); 269 270 gssbuf.value = buffer_ptr(&b); 271 gssbuf.length = buffer_len(&b); 272 273 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) 274 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 275 else 276 logit("GSSAPI MIC check failed"); 277 278 buffer_free(&b); 279 xfree(mic.value); 280 281 authctxt->postponed = 0; 282 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 283 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 284 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 285 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 286 userauth_finish(authctxt, authenticated, "gssapi-with-mic"); 287 } 288 289 Authmethod method_gssapi = { 290 "gssapi-with-mic", 291 userauth_gssapi, 292 &options.gss_authentication 293 }; 294