auth2-gss.c revision 1.24
1/* $OpenBSD: auth2-gss.c,v 1.24 2017/05/30 14:23:52 markus 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#ifdef GSSAPI 28 29#include <sys/types.h> 30 31#include "xmalloc.h" 32#include "key.h" 33#include "hostfile.h" 34#include "auth.h" 35#include "ssh2.h" 36#include "log.h" 37#include "dispatch.h" 38#include "buffer.h" 39#include "servconf.h" 40#include "packet.h" 41#include "ssh-gss.h" 42#include "monitor_wrap.h" 43 44extern ServerOptions options; 45 46static int input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh); 47static int input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh); 48static int input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh); 49static int input_gssapi_errtok(int, u_int32_t, struct ssh *); 50 51/* 52 * We only support those mechanisms that we know about (ie ones that we know 53 * how to check local user kuserok and the like) 54 */ 55static int 56userauth_gssapi(Authctxt *authctxt) 57{ 58 gss_OID_desc goid = {0, NULL}; 59 Gssctxt *ctxt = NULL; 60 int mechs; 61 int present; 62 OM_uint32 ms; 63 u_int len; 64 u_char *doid = NULL; 65 66 if (!authctxt->valid || authctxt->user == NULL) 67 return (0); 68 69 mechs = packet_get_int(); 70 if (mechs == 0) { 71 debug("Mechanism negotiation is not supported"); 72 return (0); 73 } 74 75 do { 76 mechs--; 77 78 free(doid); 79 80 present = 0; 81 doid = packet_get_string(&len); 82 83 if (len > 2 && doid[0] == SSH_GSS_OIDTYPE && 84 doid[1] == len - 2) { 85 goid.elements = doid + 2; 86 goid.length = len - 2; 87 ssh_gssapi_test_oid_supported(&ms, &goid, &present); 88 } else { 89 logit("Badly formed OID received"); 90 } 91 } while (mechs > 0 && !present); 92 93 if (!present) { 94 free(doid); 95 authctxt->server_caused_failure = 1; 96 return (0); 97 } 98 99 if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) { 100 if (ctxt != NULL) 101 ssh_gssapi_delete_ctx(&ctxt); 102 free(doid); 103 authctxt->server_caused_failure = 1; 104 return (0); 105 } 106 107 authctxt->methoddata = (void *)ctxt; 108 109 packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE); 110 111 /* Return the OID that we received */ 112 packet_put_string(doid, len); 113 114 packet_send(); 115 free(doid); 116 117 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); 118 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); 119 authctxt->postponed = 1; 120 121 return (0); 122} 123 124static int 125input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh) 126{ 127 Authctxt *authctxt = ssh->authctxt; 128 Gssctxt *gssctxt; 129 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 130 gss_buffer_desc recv_tok; 131 OM_uint32 maj_status, min_status, flags; 132 u_int len; 133 134 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 135 fatal("No authentication or GSSAPI context"); 136 137 gssctxt = authctxt->methoddata; 138 recv_tok.value = packet_get_string(&len); 139 recv_tok.length = len; /* u_int vs. size_t */ 140 141 packet_check_eom(); 142 143 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 144 &send_tok, &flags)); 145 146 free(recv_tok.value); 147 148 if (GSS_ERROR(maj_status)) { 149 if (send_tok.length != 0) { 150 packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK); 151 packet_put_string(send_tok.value, send_tok.length); 152 packet_send(); 153 } 154 authctxt->postponed = 0; 155 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 156 userauth_finish(authctxt, 0, "gssapi-with-mic", NULL); 157 } else { 158 if (send_tok.length != 0) { 159 packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN); 160 packet_put_string(send_tok.value, send_tok.length); 161 packet_send(); 162 } 163 if (maj_status == GSS_S_COMPLETE) { 164 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 165 if (flags & GSS_C_INTEG_FLAG) 166 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, 167 &input_gssapi_mic); 168 else 169 dispatch_set( 170 SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, 171 &input_gssapi_exchange_complete); 172 } 173 } 174 175 gss_release_buffer(&min_status, &send_tok); 176 return 0; 177} 178 179static int 180input_gssapi_errtok(int type, u_int32_t plen, struct ssh *ssh) 181{ 182 Authctxt *authctxt = ssh->authctxt; 183 Gssctxt *gssctxt; 184 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 185 gss_buffer_desc recv_tok; 186 OM_uint32 maj_status; 187 u_int len; 188 189 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 190 fatal("No authentication or GSSAPI context"); 191 192 gssctxt = authctxt->methoddata; 193 recv_tok.value = packet_get_string(&len); 194 recv_tok.length = len; 195 196 packet_check_eom(); 197 198 /* Push the error token into GSSAPI to see what it says */ 199 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 200 &send_tok, NULL)); 201 202 free(recv_tok.value); 203 204 /* We can't return anything to the client, even if we wanted to */ 205 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 206 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 207 208 /* The client will have already moved on to the next auth */ 209 210 gss_release_buffer(&maj_status, &send_tok); 211 return 0; 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 220static int 221input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh) 222{ 223 Authctxt *authctxt = ssh->authctxt; 224 int authenticated; 225 226 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 227 fatal("No authentication or GSSAPI context"); 228 229 /* 230 * We don't need to check the status, because we're only enabled in 231 * the dispatcher once the exchange is complete 232 */ 233 234 packet_check_eom(); 235 236 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 237 238 authctxt->postponed = 0; 239 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 240 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 241 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 242 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 243 userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL); 244 return 0; 245} 246 247static int 248input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh) 249{ 250 Authctxt *authctxt = ssh->authctxt; 251 Gssctxt *gssctxt; 252 int authenticated = 0; 253 Buffer b; 254 gss_buffer_desc mic, gssbuf; 255 u_int len; 256 257 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 258 fatal("No authentication or GSSAPI context"); 259 260 gssctxt = authctxt->methoddata; 261 262 mic.value = packet_get_string(&len); 263 mic.length = len; 264 265 ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, 266 "gssapi-with-mic"); 267 268 gssbuf.value = buffer_ptr(&b); 269 gssbuf.length = buffer_len(&b); 270 271 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) 272 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 273 else 274 logit("GSSAPI MIC check failed"); 275 276 buffer_free(&b); 277 free(mic.value); 278 279 authctxt->postponed = 0; 280 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 281 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 282 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 283 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 284 userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL); 285 return 0; 286} 287 288Authmethod method_gssapi = { 289 "gssapi-with-mic", 290 userauth_gssapi, 291 &options.gss_authentication 292}; 293#endif 294