1 /* $NetBSD: auth2-gss.c,v 1.14 2020/02/27 00:24:40 christos Exp $ */ 2 /* $OpenBSD: auth2-gss.c,v 1.29 2018/07/31 03:10:27 djm Exp $ */ 3 4 /* 5 * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #include "includes.h" 29 __RCSID("$NetBSD: auth2-gss.c,v 1.14 2020/02/27 00:24:40 christos Exp $"); 30 31 #ifdef GSSAPI 32 33 #include <sys/types.h> 34 #include <stdarg.h> 35 36 #include "xmalloc.h" 37 #include "sshkey.h" 38 #include "hostfile.h" 39 #include "auth.h" 40 #include "ssh2.h" 41 #include "log.h" 42 #include "misc.h" 43 #include "dispatch.h" 44 #include "sshbuf.h" 45 #include "ssherr.h" 46 #include "servconf.h" 47 #include "packet.h" 48 #include "ssh-gss.h" 49 #include "monitor_wrap.h" 50 51 extern ServerOptions options; 52 53 static int input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh); 54 static int input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh); 55 static int input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh); 56 static int input_gssapi_errtok(int, u_int32_t, struct ssh *); 57 58 /* 59 * We only support those mechanisms that we know about (ie ones that we know 60 * how to check local user kuserok and the like) 61 */ 62 static int 63 userauth_gssapi(struct ssh *ssh) 64 { 65 Authctxt *authctxt = ssh->authctxt; 66 gss_OID_desc goid = {0, NULL}; 67 Gssctxt *ctxt = NULL; 68 int r, present; 69 u_int mechs; 70 OM_uint32 ms; 71 size_t len; 72 u_char *doid = NULL; 73 74 if ((r = sshpkt_get_u32(ssh, &mechs)) != 0) 75 fatal("%s: %s", __func__, ssh_err(r)); 76 77 if (mechs == 0) { 78 debug("Mechanism negotiation is not supported"); 79 return (0); 80 } 81 82 do { 83 mechs--; 84 85 free(doid); 86 87 present = 0; 88 if ((r = sshpkt_get_string(ssh, &doid, &len)) != 0) 89 fatal("%s: %s", __func__, ssh_err(r)); 90 91 if (len > 2 && doid[0] == SSH_GSS_OIDTYPE && 92 doid[1] == len - 2) { 93 goid.elements = doid + 2; 94 goid.length = len - 2; 95 ssh_gssapi_test_oid_supported(&ms, &goid, &present); 96 } else { 97 logit("Badly formed OID received"); 98 } 99 } while (mechs > 0 && !present); 100 101 if (!present) { 102 free(doid); 103 authctxt->server_caused_failure = 1; 104 return (0); 105 } 106 107 if (!authctxt->valid || authctxt->user == NULL) { 108 debug2("%s: disabled because of invalid user", __func__); 109 free(doid); 110 return (0); 111 } 112 113 if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) { 114 if (ctxt != NULL) 115 ssh_gssapi_delete_ctx(&ctxt); 116 free(doid); 117 authctxt->server_caused_failure = 1; 118 return (0); 119 } 120 121 authctxt->methoddata = (void *)ctxt; 122 123 /* Return the OID that we received */ 124 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_GSSAPI_RESPONSE)) != 0 || 125 (r = sshpkt_put_string(ssh, doid, len)) != 0 || 126 (r = sshpkt_send(ssh)) != 0) 127 fatal("%s: %s", __func__, ssh_err(r)); 128 129 free(doid); 130 131 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); 132 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); 133 authctxt->postponed = 1; 134 135 return (0); 136 } 137 138 static int 139 input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh) 140 { 141 Authctxt *authctxt = ssh->authctxt; 142 Gssctxt *gssctxt; 143 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 144 gss_buffer_desc recv_tok; 145 OM_uint32 maj_status, min_status, flags; 146 u_char *p; 147 size_t len; 148 int r; 149 150 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 151 fatal("No authentication or GSSAPI context"); 152 153 gssctxt = authctxt->methoddata; 154 if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 || 155 (r = sshpkt_get_end(ssh)) != 0) 156 fatal("%s: %s", __func__, ssh_err(r)); 157 158 recv_tok.value = p; 159 recv_tok.length = len; 160 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 161 &send_tok, &flags)); 162 163 free(p); 164 165 if (GSS_ERROR(maj_status)) { 166 if (send_tok.length != 0) { 167 if ((r = sshpkt_start(ssh, 168 SSH2_MSG_USERAUTH_GSSAPI_ERRTOK)) != 0 || 169 (r = sshpkt_put_string(ssh, send_tok.value, 170 send_tok.length)) != 0 || 171 (r = sshpkt_send(ssh)) != 0) 172 fatal("%s: %s", __func__, ssh_err(r)); 173 } 174 authctxt->postponed = 0; 175 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 176 userauth_finish(ssh, 0, "gssapi-with-mic", NULL); 177 } else { 178 if (send_tok.length != 0) { 179 if ((r = sshpkt_start(ssh, 180 SSH2_MSG_USERAUTH_GSSAPI_TOKEN)) != 0 || 181 (r = sshpkt_put_string(ssh, send_tok.value, 182 send_tok.length)) != 0 || 183 (r = sshpkt_send(ssh)) != 0) 184 fatal("%s: %s", __func__, ssh_err(r)); 185 } 186 if (maj_status == GSS_S_COMPLETE) { 187 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 188 if (flags & GSS_C_INTEG_FLAG) 189 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, 190 &input_gssapi_mic); 191 else 192 ssh_dispatch_set(ssh, 193 SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, 194 &input_gssapi_exchange_complete); 195 } 196 } 197 198 gss_release_buffer(&min_status, &send_tok); 199 return 0; 200 } 201 202 static int 203 input_gssapi_errtok(int type, u_int32_t plen, struct ssh *ssh) 204 { 205 Authctxt *authctxt = ssh->authctxt; 206 Gssctxt *gssctxt; 207 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 208 gss_buffer_desc recv_tok; 209 OM_uint32 maj_status; 210 int r; 211 u_char *p; 212 size_t len; 213 214 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 215 fatal("No authentication or GSSAPI context"); 216 217 gssctxt = authctxt->methoddata; 218 if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 || 219 (r = sshpkt_get_end(ssh)) != 0) 220 fatal("%s: %s", __func__, ssh_err(r)); 221 recv_tok.value = p; 222 recv_tok.length = len; 223 224 /* Push the error token into GSSAPI to see what it says */ 225 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 226 &send_tok, NULL)); 227 228 free(recv_tok.value); 229 230 /* We can't return anything to the client, even if we wanted to */ 231 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 232 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 233 234 /* The client will have already moved on to the next auth */ 235 236 gss_release_buffer(&maj_status, &send_tok); 237 return 0; 238 } 239 240 /* 241 * This is called when the client thinks we've completed authentication. 242 * It should only be enabled in the dispatch handler by the function above, 243 * which only enables it once the GSSAPI exchange is complete. 244 */ 245 246 static int 247 input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh) 248 { 249 Authctxt *authctxt = ssh->authctxt; 250 int r, authenticated; 251 const char *displayname; 252 253 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 254 fatal("No authentication or GSSAPI context"); 255 256 /* 257 * We don't need to check the status, because we're only enabled in 258 * the dispatcher once the exchange is complete 259 */ 260 261 if ((r = sshpkt_get_end(ssh)) != 0) 262 fatal("%s: %s", __func__, ssh_err(r)); 263 264 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 265 266 if ((!use_privsep || mm_is_monitor()) && 267 (displayname = ssh_gssapi_displayname()) != NULL) 268 auth2_record_info(authctxt, "%s", displayname); 269 270 authctxt->postponed = 0; 271 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 272 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 273 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 274 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 275 userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL); 276 return 0; 277 } 278 279 static int 280 input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh) 281 { 282 Authctxt *authctxt = ssh->authctxt; 283 Gssctxt *gssctxt; 284 int r, authenticated = 0; 285 struct sshbuf *b; 286 gss_buffer_desc mic, gssbuf; 287 const char *displayname; 288 u_char *p; 289 size_t len; 290 291 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 292 fatal("No authentication or GSSAPI context"); 293 294 gssctxt = authctxt->methoddata; 295 296 if ((r = sshpkt_get_string(ssh, &p, &len)) != 0) 297 fatal("%s: %s", __func__, ssh_err(r)); 298 if ((b = sshbuf_new()) == NULL) 299 fatal("%s: sshbuf_new failed", __func__); 300 mic.value = p; 301 mic.length = len; 302 ssh_gssapi_buildmic(b, authctxt->user, authctxt->service, 303 "gssapi-with-mic"); 304 305 if ((gssbuf.value = sshbuf_mutable_ptr(b)) == NULL) 306 fatal("%s: sshbuf_mutable_ptr failed", __func__); 307 gssbuf.length = sshbuf_len(b); 308 309 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) 310 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 311 else 312 logit("GSSAPI MIC check failed"); 313 314 sshbuf_free(b); 315 free(mic.value); 316 317 if ((!use_privsep || mm_is_monitor()) && 318 (displayname = ssh_gssapi_displayname()) != NULL) 319 auth2_record_info(authctxt, "%s", displayname); 320 321 authctxt->postponed = 0; 322 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 323 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 324 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 325 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 326 userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL); 327 return 0; 328 } 329 330 Authmethod method_gssapi = { 331 "gssapi-with-mic", 332 userauth_gssapi, 333 &options.gss_authentication 334 }; 335 #endif 336