1 /* $NetBSD: gss-serv.c,v 1.18 2026/04/08 18:58:40 christos Exp $ */ 2 /* $OpenBSD: gss-serv.c,v 1.33 2025/09/29 21:30:15 dtucker 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: gss-serv.c,v 1.18 2026/04/08 18:58:40 christos Exp $"); 30 31 #include <sys/param.h> 32 #ifdef GSSAPI 33 34 #include <sys/types.h> 35 #include <sys/param.h> 36 #include <sys/queue.h> 37 38 #include <netdb.h> 39 #include <stdarg.h> 40 #include <string.h> 41 #include <unistd.h> 42 43 #include "xmalloc.h" 44 #include "sshkey.h" 45 #include "hostfile.h" 46 #include "auth.h" 47 #include "log.h" 48 #include "channels.h" 49 #include "session.h" 50 #include "misc.h" 51 #include "servconf.h" 52 53 #include "ssh-gss.h" 54 55 extern ServerOptions options; 56 57 static ssh_gssapi_client gssapi_client = 58 { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER, 59 GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL, NULL}}; 60 61 ssh_gssapi_mech gssapi_null_mech = 62 { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL}; 63 64 #ifdef KRB5 65 extern ssh_gssapi_mech gssapi_kerberos_mech; 66 #endif 67 68 ssh_gssapi_mech* supported_mechs[]= { 69 #ifdef KRB5 70 &gssapi_kerberos_mech, 71 #endif 72 &gssapi_null_mech, 73 }; 74 75 /* 76 * ssh_gssapi_supported_oids() can cause sandbox violations, so prepare the 77 * list of supported mechanisms before privsep is set up. 78 */ 79 static gss_OID_set supported_oids; 80 81 void 82 ssh_gssapi_prepare_supported_oids(void) 83 { 84 ssh_gssapi_supported_oids(&supported_oids); 85 } 86 87 OM_uint32 88 ssh_gssapi_test_oid_supported(OM_uint32 *ms, gss_OID member, int *present) 89 { 90 if (supported_oids == NULL) 91 ssh_gssapi_prepare_supported_oids(); 92 return gss_test_oid_set_member(ms, member, supported_oids, present); 93 } 94 95 /* 96 * Acquire credentials for a server running on the current host. 97 * Requires that the context structure contains a valid OID 98 */ 99 100 /* Returns a GSSAPI error code */ 101 /* Privileged (called from ssh_gssapi_server_ctx) */ 102 static OM_uint32 103 ssh_gssapi_acquire_cred(Gssctxt *ctx) 104 { 105 OM_uint32 status; 106 char lname[NI_MAXHOST]; 107 gss_OID_set oidset; 108 109 if (options.gss_strict_acceptor) { 110 gss_create_empty_oid_set(&status, &oidset); 111 gss_add_oid_set_member(&status, ctx->oid, &oidset); 112 113 if (gethostname(lname, sizeof(lname))) { 114 gss_release_oid_set(&status, &oidset); 115 return (-1); 116 } 117 118 if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) { 119 gss_release_oid_set(&status, &oidset); 120 return (ctx->major); 121 } 122 123 if ((ctx->major = gss_acquire_cred(&ctx->minor, 124 ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, 125 NULL, NULL))) 126 ssh_gssapi_error(ctx); 127 128 gss_release_oid_set(&status, &oidset); 129 return (ctx->major); 130 } else { 131 ctx->name = GSS_C_NO_NAME; 132 ctx->creds = GSS_C_NO_CREDENTIAL; 133 } 134 return GSS_S_COMPLETE; 135 } 136 137 /* Privileged */ 138 OM_uint32 139 ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid) 140 { 141 if (*ctx) 142 ssh_gssapi_delete_ctx(ctx); 143 ssh_gssapi_build_ctx(ctx); 144 ssh_gssapi_set_oid(*ctx, oid); 145 return (ssh_gssapi_acquire_cred(*ctx)); 146 } 147 148 /* Unprivileged */ 149 void 150 ssh_gssapi_supported_oids(gss_OID_set *oidset) 151 { 152 int i = 0; 153 OM_uint32 min_status; 154 int present; 155 gss_OID_set supported; 156 157 gss_create_empty_oid_set(&min_status, oidset); 158 gss_indicate_mechs(&min_status, &supported); 159 160 while (supported_mechs[i]->name != NULL) { 161 if (GSS_ERROR(gss_test_oid_set_member(&min_status, 162 &supported_mechs[i]->oid, supported, &present))) 163 present = 0; 164 if (present) 165 gss_add_oid_set_member(&min_status, 166 &supported_mechs[i]->oid, oidset); 167 i++; 168 } 169 170 gss_release_oid_set(&min_status, &supported); 171 } 172 173 174 /* Wrapper around accept_sec_context 175 * Requires that the context contains: 176 * oid 177 * credentials (from ssh_gssapi_acquire_cred) 178 */ 179 /* Privileged */ 180 OM_uint32 181 ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok, 182 gss_buffer_desc *send_tok, OM_uint32 *flags) 183 { 184 OM_uint32 status; 185 gss_OID mech; 186 187 ctx->major = gss_accept_sec_context(&ctx->minor, 188 &ctx->context, ctx->creds, recv_tok, 189 GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech, 190 send_tok, flags, NULL, &ctx->client_creds); 191 192 if (GSS_ERROR(ctx->major)) 193 ssh_gssapi_error(ctx); 194 195 if (ctx->client_creds) 196 debug("Received some client credentials"); 197 else 198 debug("Got no client credentials"); 199 200 status = ctx->major; 201 202 /* Now, if we're complete and we have the right flags, then 203 * we flag the user as also having been authenticated 204 */ 205 206 if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) && 207 (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) { 208 if (ssh_gssapi_getclient(ctx, &gssapi_client)) 209 fatal("Couldn't convert client name"); 210 } 211 212 return (status); 213 } 214 215 /* 216 * This parses an exported name, extracting the mechanism specific portion 217 * to use for ACL checking. It verifies that the name belongs the mechanism 218 * originally selected. 219 */ 220 static OM_uint32 221 ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name) 222 { 223 u_char *tok; 224 OM_uint32 offset; 225 OM_uint32 oidl; 226 227 tok = ename->value; 228 229 /* 230 * Check that ename is long enough for all of the fixed length 231 * header, and that the initial ID bytes are correct 232 */ 233 234 if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0) 235 return GSS_S_FAILURE; 236 237 /* 238 * Extract the OID, and check it. Here GSSAPI breaks with tradition 239 * and does use the OID type and length bytes. To confuse things 240 * there are two lengths - the first including these, and the 241 * second without. 242 */ 243 244 oidl = get_u16(tok+2); /* length including next two bytes */ 245 oidl = oidl-2; /* turn it into the _real_ length of the variable OID */ 246 247 /* 248 * Check the BER encoding for correct type and length, that the 249 * string is long enough and that the OID matches that in our context 250 */ 251 if (tok[4] != 0x06 || tok[5] != oidl || 252 ename->length < oidl+6 || 253 !ssh_gssapi_check_oid(ctx, tok+6, oidl)) 254 return GSS_S_FAILURE; 255 256 offset = oidl+6; 257 258 if (ename->length < offset+4) 259 return GSS_S_FAILURE; 260 261 name->length = get_u32(tok+offset); 262 offset += 4; 263 264 if (UINT_MAX - offset < name->length) 265 return GSS_S_FAILURE; 266 if (ename->length < offset+name->length) 267 return GSS_S_FAILURE; 268 269 name->value = xmalloc(name->length+1); 270 memcpy(name->value, tok+offset, name->length); 271 ((char *)name->value)[name->length] = 0; 272 273 return GSS_S_COMPLETE; 274 } 275 276 /* Extract the client details from a given context. This can only reliably 277 * be called once for a context */ 278 279 /* Privileged (called from accept_secure_ctx) */ 280 OM_uint32 281 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client) 282 { 283 int i = 0; 284 285 gss_buffer_desc ename; 286 287 client->mech = NULL; 288 289 while (supported_mechs[i]->name != NULL) { 290 if (supported_mechs[i]->oid.length == ctx->oid->length && 291 (memcmp(supported_mechs[i]->oid.elements, 292 ctx->oid->elements, ctx->oid->length) == 0)) 293 client->mech = supported_mechs[i]; 294 i++; 295 } 296 297 if (client->mech == NULL) 298 return GSS_S_FAILURE; 299 300 if ((ctx->major = gss_display_name(&ctx->minor, ctx->client, 301 &client->displayname, NULL))) { 302 ssh_gssapi_error(ctx); 303 return (ctx->major); 304 } 305 306 if ((ctx->major = gss_export_name(&ctx->minor, ctx->client, 307 &ename))) { 308 ssh_gssapi_error(ctx); 309 return (ctx->major); 310 } 311 312 if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename, 313 &client->exportedname))) { 314 return (ctx->major); 315 } 316 317 /* We can't copy this structure, so we just move the pointer to it */ 318 client->creds = ctx->client_creds; 319 ctx->client_creds = GSS_C_NO_CREDENTIAL; 320 return (ctx->major); 321 } 322 323 /* As user - called on fatal/exit */ 324 void 325 ssh_gssapi_cleanup_creds(void) 326 { 327 if (gssapi_client.store.filename != NULL) { 328 /* Unlink probably isn't sufficient */ 329 debug("removing gssapi cred file\"%s\"", 330 gssapi_client.store.filename); 331 unlink(gssapi_client.store.filename); 332 } 333 } 334 335 /* As user */ 336 void 337 ssh_gssapi_storecreds(void) 338 { 339 if (options.gss_deleg_creds == 0) { 340 debug_f("delegate credential is disabled, doing nothing"); 341 return; 342 } 343 344 if (gssapi_client.mech && gssapi_client.mech->storecreds) { 345 (*gssapi_client.mech->storecreds)(&gssapi_client); 346 } else 347 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism"); 348 } 349 350 /* This allows GSSAPI methods to do things to the child's environment based 351 * on the passed authentication process and credentials. 352 */ 353 /* As user */ 354 void 355 ssh_gssapi_do_child(char ***envp, u_int *envsizep) 356 { 357 358 if (gssapi_client.store.envvar != NULL && 359 gssapi_client.store.envval != NULL) { 360 debug("Setting %s to %s", gssapi_client.store.envvar, 361 gssapi_client.store.envval); 362 child_set_env(envp, envsizep, gssapi_client.store.envvar, 363 gssapi_client.store.envval); 364 } 365 } 366 367 /* Privileged */ 368 int 369 ssh_gssapi_userok(char *user) 370 { 371 OM_uint32 lmin; 372 373 if (gssapi_client.exportedname.length == 0 || 374 gssapi_client.exportedname.value == NULL) { 375 debug("No suitable client data"); 376 return 0; 377 } 378 if (gssapi_client.mech && gssapi_client.mech->userok) 379 if ((*gssapi_client.mech->userok)(&gssapi_client, user)) 380 return 1; 381 else { 382 /* Destroy delegated credentials if userok fails */ 383 gss_release_buffer(&lmin, &gssapi_client.displayname); 384 gss_release_buffer(&lmin, &gssapi_client.exportedname); 385 gss_release_cred(&lmin, &gssapi_client.creds); 386 explicit_bzero(&gssapi_client, 387 sizeof(ssh_gssapi_client)); 388 return 0; 389 } 390 else 391 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism"); 392 return (0); 393 } 394 395 /* Privileged */ 396 OM_uint32 397 ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic) 398 { 399 ctx->major = gss_verify_mic(&ctx->minor, ctx->context, 400 gssbuf, gssmic, NULL); 401 402 return (ctx->major); 403 } 404 405 /* Privileged */ 406 const char *ssh_gssapi_displayname(void) 407 { 408 if (gssapi_client.displayname.length == 0 || 409 gssapi_client.displayname.value == NULL) 410 return NULL; 411 return (char *)gssapi_client.displayname.value; 412 } 413 414 #endif 415
Indexes created Fri Jun 26 00:24:39 UTC 2026