1 /* $OpenBSD: auth2-gss.c,v 1.12 2005/10/13 22:24:31 stevesk 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 "includes.h" 28 29 #ifdef GSSAPI 30 31 #include "auth.h" 32 #include "ssh2.h" 33 #include "xmalloc.h" 34 #include "log.h" 35 #include "dispatch.h" 36 #include "servconf.h" 37 #include "packet.h" 38 #include "monitor_wrap.h" 39 40 #include "ssh-gss.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 xfree(doid); 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 xfree(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 } 123 124 static void 125 input_gssapi_token(int type, u_int32_t plen, void *ctxt) 126 { 127 Authctxt *authctxt = ctxt; 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 xfree(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"); 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 } 177 178 static void 179 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt) 180 { 181 Authctxt *authctxt = ctxt; 182 Gssctxt *gssctxt; 183 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 184 gss_buffer_desc recv_tok; 185 OM_uint32 maj_status; 186 u_int len; 187 188 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 189 fatal("No authentication or GSSAPI context"); 190 191 gssctxt = authctxt->methoddata; 192 recv_tok.value = packet_get_string(&len); 193 recv_tok.length = len; 194 195 packet_check_eom(); 196 197 /* Push the error token into GSSAPI to see what it says */ 198 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 199 &send_tok, NULL)); 200 201 xfree(recv_tok.value); 202 203 /* We can't return anything to the client, even if we wanted to */ 204 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 205 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 206 207 /* The client will have already moved on to the next auth */ 208 209 gss_release_buffer(&maj_status, &send_tok); 210 } 211 212 /* 213 * This is called when the client thinks we've completed authentication. 214 * It should only be enabled in the dispatch handler by the function above, 215 * which only enables it once the GSSAPI exchange is complete. 216 */ 217 218 static void 219 input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt) 220 { 221 Authctxt *authctxt = ctxt; 222 Gssctxt *gssctxt; 223 int authenticated; 224 225 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 226 fatal("No authentication or GSSAPI context"); 227 228 gssctxt = authctxt->methoddata; 229 230 /* 231 * We don't need to check the status, because we're only enabled in 232 * the dispatcher once the exchange is complete 233 */ 234 235 packet_check_eom(); 236 237 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 238 239 authctxt->postponed = 0; 240 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 241 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 242 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 243 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 244 userauth_finish(authctxt, authenticated, "gssapi-with-mic"); 245 } 246 247 static void 248 input_gssapi_mic(int type, u_int32_t plen, void *ctxt) 249 { 250 Authctxt *authctxt = ctxt; 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 xfree(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"); 285 } 286 287 Authmethod method_gssapi = { 288 "gssapi-with-mic", 289 userauth_gssapi, 290 &options.gss_authentication 291 }; 292 293 #endif /* GSSAPI */ 294