1 /* $OpenBSD: gss-serv.c,v 1.28 2015/01/20 23:14:00 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 #include <sys/queue.h> 29 30 #ifdef GSSAPI 31 32 #include <string.h> 33 34 #include "xmalloc.h" 35 #include "buffer.h" 36 #include "key.h" 37 #include "hostfile.h" 38 #include "auth.h" 39 #include "log.h" 40 #include "channels.h" 41 #include "session.h" 42 #include "misc.h" 43 44 #include "ssh-gss.h" 45 46 static ssh_gssapi_client gssapi_client = 47 { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER, 48 GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL, NULL}}; 49 50 ssh_gssapi_mech gssapi_null_mech = 51 { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL}; 52 53 #ifdef KRB5 54 extern ssh_gssapi_mech gssapi_kerberos_mech; 55 #endif 56 57 ssh_gssapi_mech* supported_mechs[]= { 58 #ifdef KRB5 59 &gssapi_kerberos_mech, 60 #endif 61 &gssapi_null_mech, 62 }; 63 64 /* 65 * ssh_gssapi_supported_oids() can cause sandbox violations, so prepare the 66 * list of supported mechanisms before privsep is set up. 67 */ 68 static gss_OID_set supported_oids; 69 70 void 71 ssh_gssapi_prepare_supported_oids(void) 72 { 73 ssh_gssapi_supported_oids(&supported_oids); 74 } 75 76 OM_uint32 77 ssh_gssapi_test_oid_supported(OM_uint32 *ms, gss_OID member, int *present) 78 { 79 if (supported_oids == NULL) 80 ssh_gssapi_prepare_supported_oids(); 81 return gss_test_oid_set_member(ms, member, supported_oids, present); 82 } 83 84 /* 85 * Acquire credentials for a server running on the current host. 86 * Requires that the context structure contains a valid OID 87 */ 88 89 /* Returns a GSSAPI error code */ 90 /* Privileged (called from ssh_gssapi_server_ctx) */ 91 static OM_uint32 92 ssh_gssapi_acquire_cred(Gssctxt *ctx) 93 { 94 OM_uint32 status; 95 char lname[NI_MAXHOST]; 96 gss_OID_set oidset; 97 98 gss_create_empty_oid_set(&status, &oidset); 99 gss_add_oid_set_member(&status, ctx->oid, &oidset); 100 101 if (gethostname(lname, sizeof(lname))) { 102 gss_release_oid_set(&status, &oidset); 103 return (-1); 104 } 105 106 if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) { 107 gss_release_oid_set(&status, &oidset); 108 return (ctx->major); 109 } 110 111 if ((ctx->major = gss_acquire_cred(&ctx->minor, 112 ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, NULL, NULL))) 113 ssh_gssapi_error(ctx); 114 115 gss_release_oid_set(&status, &oidset); 116 return (ctx->major); 117 } 118 119 /* Privileged */ 120 OM_uint32 121 ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid) 122 { 123 if (*ctx) 124 ssh_gssapi_delete_ctx(ctx); 125 ssh_gssapi_build_ctx(ctx); 126 ssh_gssapi_set_oid(*ctx, oid); 127 return (ssh_gssapi_acquire_cred(*ctx)); 128 } 129 130 /* Unprivileged */ 131 void 132 ssh_gssapi_supported_oids(gss_OID_set *oidset) 133 { 134 int i = 0; 135 OM_uint32 min_status; 136 int present; 137 gss_OID_set supported; 138 139 gss_create_empty_oid_set(&min_status, oidset); 140 gss_indicate_mechs(&min_status, &supported); 141 142 while (supported_mechs[i]->name != NULL) { 143 if (GSS_ERROR(gss_test_oid_set_member(&min_status, 144 &supported_mechs[i]->oid, supported, &present))) 145 present = 0; 146 if (present) 147 gss_add_oid_set_member(&min_status, 148 &supported_mechs[i]->oid, oidset); 149 i++; 150 } 151 152 gss_release_oid_set(&min_status, &supported); 153 } 154 155 156 /* Wrapper around accept_sec_context 157 * Requires that the context contains: 158 * oid 159 * credentials (from ssh_gssapi_acquire_cred) 160 */ 161 /* Privileged */ 162 OM_uint32 163 ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok, 164 gss_buffer_desc *send_tok, OM_uint32 *flags) 165 { 166 OM_uint32 status; 167 gss_OID mech; 168 169 ctx->major = gss_accept_sec_context(&ctx->minor, 170 &ctx->context, ctx->creds, recv_tok, 171 GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech, 172 send_tok, flags, NULL, &ctx->client_creds); 173 174 if (GSS_ERROR(ctx->major)) 175 ssh_gssapi_error(ctx); 176 177 if (ctx->client_creds) 178 debug("Received some client credentials"); 179 else 180 debug("Got no client credentials"); 181 182 status = ctx->major; 183 184 /* Now, if we're complete and we have the right flags, then 185 * we flag the user as also having been authenticated 186 */ 187 188 if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) && 189 (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) { 190 if (ssh_gssapi_getclient(ctx, &gssapi_client)) 191 fatal("Couldn't convert client name"); 192 } 193 194 return (status); 195 } 196 197 /* 198 * This parses an exported name, extracting the mechanism specific portion 199 * to use for ACL checking. It verifies that the name belongs the mechanism 200 * originally selected. 201 */ 202 static OM_uint32 203 ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name) 204 { 205 u_char *tok; 206 OM_uint32 offset; 207 OM_uint32 oidl; 208 209 tok = ename->value; 210 211 /* 212 * Check that ename is long enough for all of the fixed length 213 * header, and that the initial ID bytes are correct 214 */ 215 216 if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0) 217 return GSS_S_FAILURE; 218 219 /* 220 * Extract the OID, and check it. Here GSSAPI breaks with tradition 221 * and does use the OID type and length bytes. To confuse things 222 * there are two lengths - the first including these, and the 223 * second without. 224 */ 225 226 oidl = get_u16(tok+2); /* length including next two bytes */ 227 oidl = oidl-2; /* turn it into the _real_ length of the variable OID */ 228 229 /* 230 * Check the BER encoding for correct type and length, that the 231 * string is long enough and that the OID matches that in our context 232 */ 233 if (tok[4] != 0x06 || tok[5] != oidl || 234 ename->length < oidl+6 || 235 !ssh_gssapi_check_oid(ctx, tok+6, oidl)) 236 return GSS_S_FAILURE; 237 238 offset = oidl+6; 239 240 if (ename->length < offset+4) 241 return GSS_S_FAILURE; 242 243 name->length = get_u32(tok+offset); 244 offset += 4; 245 246 if (UINT_MAX - offset < name->length) 247 return GSS_S_FAILURE; 248 if (ename->length < offset+name->length) 249 return GSS_S_FAILURE; 250 251 name->value = xmalloc(name->length+1); 252 memcpy(name->value, tok+offset, name->length); 253 ((char *)name->value)[name->length] = 0; 254 255 return GSS_S_COMPLETE; 256 } 257 258 /* Extract the client details from a given context. This can only reliably 259 * be called once for a context */ 260 261 /* Privileged (called from accept_secure_ctx) */ 262 OM_uint32 263 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client) 264 { 265 int i = 0; 266 267 gss_buffer_desc ename; 268 269 client->mech = NULL; 270 271 while (supported_mechs[i]->name != NULL) { 272 if (supported_mechs[i]->oid.length == ctx->oid->length && 273 (memcmp(supported_mechs[i]->oid.elements, 274 ctx->oid->elements, ctx->oid->length) == 0)) 275 client->mech = supported_mechs[i]; 276 i++; 277 } 278 279 if (client->mech == NULL) 280 return GSS_S_FAILURE; 281 282 if ((ctx->major = gss_display_name(&ctx->minor, ctx->client, 283 &client->displayname, NULL))) { 284 ssh_gssapi_error(ctx); 285 return (ctx->major); 286 } 287 288 if ((ctx->major = gss_export_name(&ctx->minor, ctx->client, 289 &ename))) { 290 ssh_gssapi_error(ctx); 291 return (ctx->major); 292 } 293 294 if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename, 295 &client->exportedname))) { 296 return (ctx->major); 297 } 298 299 /* We can't copy this structure, so we just move the pointer to it */ 300 client->creds = ctx->client_creds; 301 ctx->client_creds = GSS_C_NO_CREDENTIAL; 302 return (ctx->major); 303 } 304 305 /* As user - called on fatal/exit */ 306 void 307 ssh_gssapi_cleanup_creds(void) 308 { 309 if (gssapi_client.store.filename != NULL) { 310 /* Unlink probably isn't sufficient */ 311 debug("removing gssapi cred file\"%s\"", 312 gssapi_client.store.filename); 313 unlink(gssapi_client.store.filename); 314 } 315 } 316 317 /* As user */ 318 void 319 ssh_gssapi_storecreds(void) 320 { 321 if (gssapi_client.mech && gssapi_client.mech->storecreds) { 322 (*gssapi_client.mech->storecreds)(&gssapi_client); 323 } else 324 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism"); 325 } 326 327 /* This allows GSSAPI methods to do things to the childs environment based 328 * on the passed authentication process and credentials. 329 */ 330 /* As user */ 331 void 332 ssh_gssapi_do_child(char ***envp, u_int *envsizep) 333 { 334 335 if (gssapi_client.store.envvar != NULL && 336 gssapi_client.store.envval != NULL) { 337 debug("Setting %s to %s", gssapi_client.store.envvar, 338 gssapi_client.store.envval); 339 child_set_env(envp, envsizep, gssapi_client.store.envvar, 340 gssapi_client.store.envval); 341 } 342 } 343 344 /* Privileged */ 345 int 346 ssh_gssapi_userok(char *user) 347 { 348 OM_uint32 lmin; 349 350 if (gssapi_client.exportedname.length == 0 || 351 gssapi_client.exportedname.value == NULL) { 352 debug("No suitable client data"); 353 return 0; 354 } 355 if (gssapi_client.mech && gssapi_client.mech->userok) 356 if ((*gssapi_client.mech->userok)(&gssapi_client, user)) 357 return 1; 358 else { 359 /* Destroy delegated credentials if userok fails */ 360 gss_release_buffer(&lmin, &gssapi_client.displayname); 361 gss_release_buffer(&lmin, &gssapi_client.exportedname); 362 gss_release_cred(&lmin, &gssapi_client.creds); 363 explicit_bzero(&gssapi_client, 364 sizeof(ssh_gssapi_client)); 365 return 0; 366 } 367 else 368 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism"); 369 return (0); 370 } 371 372 /* Privileged */ 373 OM_uint32 374 ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic) 375 { 376 ctx->major = gss_verify_mic(&ctx->minor, ctx->context, 377 gssbuf, gssmic, NULL); 378 379 return (ctx->major); 380 } 381 382 #endif 383