1 /* $OpenBSD: gss-serv.c,v 1.23 2011/08/01 19:18:15 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 #include "includes.h" 28 29 #ifdef GSSAPI 30 31 #include <sys/types.h> 32 #include <sys/param.h> 33 34 #include <stdarg.h> 35 #include <string.h> 36 #include <unistd.h> 37 38 #include "openbsd-compat/sys-queue.h" 39 #include "xmalloc.h" 40 #include "buffer.h" 41 #include "key.h" 42 #include "hostfile.h" 43 #include "auth.h" 44 #include "log.h" 45 #include "channels.h" 46 #include "session.h" 47 #include "misc.h" 48 49 #include "ssh-gss.h" 50 51 static ssh_gssapi_client gssapi_client = 52 { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER, 53 GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}}; 54 55 ssh_gssapi_mech gssapi_null_mech = 56 { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL}; 57 58 #ifdef KRB5 59 extern ssh_gssapi_mech gssapi_kerberos_mech; 60 #endif 61 62 ssh_gssapi_mech* supported_mechs[]= { 63 #ifdef KRB5 64 &gssapi_kerberos_mech, 65 #endif 66 &gssapi_null_mech, 67 }; 68 69 70 /* 71 * Acquire credentials for a server running on the current host. 72 * Requires that the context structure contains a valid OID 73 */ 74 75 /* Returns a GSSAPI error code */ 76 /* Privileged (called from ssh_gssapi_server_ctx) */ 77 static OM_uint32 78 ssh_gssapi_acquire_cred(Gssctxt *ctx) 79 { 80 OM_uint32 status; 81 char lname[MAXHOSTNAMELEN]; 82 gss_OID_set oidset; 83 84 gss_create_empty_oid_set(&status, &oidset); 85 gss_add_oid_set_member(&status, ctx->oid, &oidset); 86 87 if (gethostname(lname, MAXHOSTNAMELEN)) { 88 gss_release_oid_set(&status, &oidset); 89 return (-1); 90 } 91 92 if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) { 93 gss_release_oid_set(&status, &oidset); 94 return (ctx->major); 95 } 96 97 if ((ctx->major = gss_acquire_cred(&ctx->minor, 98 ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, NULL, NULL))) 99 ssh_gssapi_error(ctx); 100 101 gss_release_oid_set(&status, &oidset); 102 return (ctx->major); 103 } 104 105 /* Privileged */ 106 OM_uint32 107 ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid) 108 { 109 if (*ctx) 110 ssh_gssapi_delete_ctx(ctx); 111 ssh_gssapi_build_ctx(ctx); 112 ssh_gssapi_set_oid(*ctx, oid); 113 return (ssh_gssapi_acquire_cred(*ctx)); 114 } 115 116 /* Unprivileged */ 117 void 118 ssh_gssapi_supported_oids(gss_OID_set *oidset) 119 { 120 int i = 0; 121 OM_uint32 min_status; 122 int present; 123 gss_OID_set supported; 124 125 gss_create_empty_oid_set(&min_status, oidset); 126 gss_indicate_mechs(&min_status, &supported); 127 128 while (supported_mechs[i]->name != NULL) { 129 if (GSS_ERROR(gss_test_oid_set_member(&min_status, 130 &supported_mechs[i]->oid, supported, &present))) 131 present = 0; 132 if (present) 133 gss_add_oid_set_member(&min_status, 134 &supported_mechs[i]->oid, oidset); 135 i++; 136 } 137 138 gss_release_oid_set(&min_status, &supported); 139 } 140 141 142 /* Wrapper around accept_sec_context 143 * Requires that the context contains: 144 * oid 145 * credentials (from ssh_gssapi_acquire_cred) 146 */ 147 /* Privileged */ 148 OM_uint32 149 ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok, 150 gss_buffer_desc *send_tok, OM_uint32 *flags) 151 { 152 OM_uint32 status; 153 gss_OID mech; 154 155 ctx->major = gss_accept_sec_context(&ctx->minor, 156 &ctx->context, ctx->creds, recv_tok, 157 GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech, 158 send_tok, flags, NULL, &ctx->client_creds); 159 160 if (GSS_ERROR(ctx->major)) 161 ssh_gssapi_error(ctx); 162 163 if (ctx->client_creds) 164 debug("Received some client credentials"); 165 else 166 debug("Got no client credentials"); 167 168 status = ctx->major; 169 170 /* Now, if we're complete and we have the right flags, then 171 * we flag the user as also having been authenticated 172 */ 173 174 if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) && 175 (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) { 176 if (ssh_gssapi_getclient(ctx, &gssapi_client)) 177 fatal("Couldn't convert client name"); 178 } 179 180 return (status); 181 } 182 183 /* 184 * This parses an exported name, extracting the mechanism specific portion 185 * to use for ACL checking. It verifies that the name belongs the mechanism 186 * originally selected. 187 */ 188 static OM_uint32 189 ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name) 190 { 191 u_char *tok; 192 OM_uint32 offset; 193 OM_uint32 oidl; 194 195 tok = ename->value; 196 197 /* 198 * Check that ename is long enough for all of the fixed length 199 * header, and that the initial ID bytes are correct 200 */ 201 202 if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0) 203 return GSS_S_FAILURE; 204 205 /* 206 * Extract the OID, and check it. Here GSSAPI breaks with tradition 207 * and does use the OID type and length bytes. To confuse things 208 * there are two lengths - the first including these, and the 209 * second without. 210 */ 211 212 oidl = get_u16(tok+2); /* length including next two bytes */ 213 oidl = oidl-2; /* turn it into the _real_ length of the variable OID */ 214 215 /* 216 * Check the BER encoding for correct type and length, that the 217 * string is long enough and that the OID matches that in our context 218 */ 219 if (tok[4] != 0x06 || tok[5] != oidl || 220 ename->length < oidl+6 || 221 !ssh_gssapi_check_oid(ctx, tok+6, oidl)) 222 return GSS_S_FAILURE; 223 224 offset = oidl+6; 225 226 if (ename->length < offset+4) 227 return GSS_S_FAILURE; 228 229 name->length = get_u32(tok+offset); 230 offset += 4; 231 232 if (UINT_MAX - offset < name->length) 233 return GSS_S_FAILURE; 234 if (ename->length < offset+name->length) 235 return GSS_S_FAILURE; 236 237 name->value = xmalloc(name->length+1); 238 memcpy(name->value, tok+offset, name->length); 239 ((char *)name->value)[name->length] = 0; 240 241 return GSS_S_COMPLETE; 242 } 243 244 /* Extract the client details from a given context. This can only reliably 245 * be called once for a context */ 246 247 /* Privileged (called from accept_secure_ctx) */ 248 OM_uint32 249 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client) 250 { 251 int i = 0; 252 253 gss_buffer_desc ename; 254 255 client->mech = NULL; 256 257 while (supported_mechs[i]->name != NULL) { 258 if (supported_mechs[i]->oid.length == ctx->oid->length && 259 (memcmp(supported_mechs[i]->oid.elements, 260 ctx->oid->elements, ctx->oid->length) == 0)) 261 client->mech = supported_mechs[i]; 262 i++; 263 } 264 265 if (client->mech == NULL) 266 return GSS_S_FAILURE; 267 268 if ((ctx->major = gss_display_name(&ctx->minor, ctx->client, 269 &client->displayname, NULL))) { 270 ssh_gssapi_error(ctx); 271 return (ctx->major); 272 } 273 274 if ((ctx->major = gss_export_name(&ctx->minor, ctx->client, 275 &ename))) { 276 ssh_gssapi_error(ctx); 277 return (ctx->major); 278 } 279 280 if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename, 281 &client->exportedname))) { 282 return (ctx->major); 283 } 284 285 /* We can't copy this structure, so we just move the pointer to it */ 286 client->creds = ctx->client_creds; 287 ctx->client_creds = GSS_C_NO_CREDENTIAL; 288 return (ctx->major); 289 } 290 291 /* As user - called on fatal/exit */ 292 void 293 ssh_gssapi_cleanup_creds(void) 294 { 295 if (gssapi_client.store.filename != NULL) { 296 /* Unlink probably isn't sufficient */ 297 debug("removing gssapi cred file\"%s\"", 298 gssapi_client.store.filename); 299 unlink(gssapi_client.store.filename); 300 } 301 } 302 303 /* As user */ 304 void 305 ssh_gssapi_storecreds(void) 306 { 307 if (gssapi_client.mech && gssapi_client.mech->storecreds) { 308 (*gssapi_client.mech->storecreds)(&gssapi_client); 309 } else 310 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism"); 311 } 312 313 /* This allows GSSAPI methods to do things to the childs environment based 314 * on the passed authentication process and credentials. 315 */ 316 /* As user */ 317 void 318 ssh_gssapi_do_child(char ***envp, u_int *envsizep) 319 { 320 321 if (gssapi_client.store.envvar != NULL && 322 gssapi_client.store.envval != NULL) { 323 debug("Setting %s to %s", gssapi_client.store.envvar, 324 gssapi_client.store.envval); 325 child_set_env(envp, envsizep, gssapi_client.store.envvar, 326 gssapi_client.store.envval); 327 } 328 } 329 330 /* Privileged */ 331 int 332 ssh_gssapi_userok(char *user) 333 { 334 OM_uint32 lmin; 335 336 if (gssapi_client.exportedname.length == 0 || 337 gssapi_client.exportedname.value == NULL) { 338 debug("No suitable client data"); 339 return 0; 340 } 341 if (gssapi_client.mech && gssapi_client.mech->userok) 342 if ((*gssapi_client.mech->userok)(&gssapi_client, user)) 343 return 1; 344 else { 345 /* Destroy delegated credentials if userok fails */ 346 gss_release_buffer(&lmin, &gssapi_client.displayname); 347 gss_release_buffer(&lmin, &gssapi_client.exportedname); 348 gss_release_cred(&lmin, &gssapi_client.creds); 349 memset(&gssapi_client, 0, sizeof(ssh_gssapi_client)); 350 return 0; 351 } 352 else 353 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism"); 354 return (0); 355 } 356 357 /* Privileged */ 358 OM_uint32 359 ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic) 360 { 361 ctx->major = gss_verify_mic(&ctx->minor, ctx->context, 362 gssbuf, gssmic, NULL); 363 364 return (ctx->major); 365 } 366 367 #endif 368