1294336Sdes/* $OpenBSD: gss-serv.c,v 1.29 2015/05/22 03:50:02 djm Exp $ */ 2124208Sdes 3124208Sdes/* 4124208Sdes * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved. 5124208Sdes * 6124208Sdes * Redistribution and use in source and binary forms, with or without 7124208Sdes * modification, are permitted provided that the following conditions 8124208Sdes * are met: 9124208Sdes * 1. Redistributions of source code must retain the above copyright 10124208Sdes * notice, this list of conditions and the following disclaimer. 11124208Sdes * 2. Redistributions in binary form must reproduce the above copyright 12124208Sdes * notice, this list of conditions and the following disclaimer in the 13124208Sdes * documentation and/or other materials provided with the distribution. 14124208Sdes * 15124208Sdes * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR 16124208Sdes * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17124208Sdes * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18124208Sdes * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19124208Sdes * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20124208Sdes * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21124208Sdes * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22124208Sdes * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23124208Sdes * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24124208Sdes * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25124208Sdes */ 26124208Sdes 27124208Sdes#include "includes.h" 28124208Sdes 29124208Sdes#ifdef GSSAPI 30124208Sdes 31162852Sdes#include <sys/types.h> 32162852Sdes 33162852Sdes#include <stdarg.h> 34162852Sdes#include <string.h> 35162852Sdes#include <unistd.h> 36162852Sdes 37181111Sdes#include "openbsd-compat/sys-queue.h" 38162852Sdes#include "xmalloc.h" 39162852Sdes#include "buffer.h" 40162852Sdes#include "key.h" 41162852Sdes#include "hostfile.h" 42124208Sdes#include "auth.h" 43124208Sdes#include "log.h" 44124208Sdes#include "channels.h" 45124208Sdes#include "session.h" 46162852Sdes#include "misc.h" 47294336Sdes#include "servconf.h" 48124208Sdes 49124208Sdes#include "ssh-gss.h" 50124208Sdes 51294336Sdesextern ServerOptions options; 52294336Sdes 53124208Sdesstatic ssh_gssapi_client gssapi_client = 54124208Sdes { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER, 55255767Sdes GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL, NULL}}; 56124208Sdes 57124208Sdesssh_gssapi_mech gssapi_null_mech = 58124208Sdes { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL}; 59124208Sdes 60124208Sdes#ifdef KRB5 61124208Sdesextern ssh_gssapi_mech gssapi_kerberos_mech; 62124208Sdes#endif 63124208Sdes 64124208Sdesssh_gssapi_mech* supported_mechs[]= { 65124208Sdes#ifdef KRB5 66124208Sdes &gssapi_kerberos_mech, 67124208Sdes#endif 68124208Sdes &gssapi_null_mech, 69124208Sdes}; 70124208Sdes 71263712Sdes/* 72263712Sdes * ssh_gssapi_supported_oids() can cause sandbox violations, so prepare the 73263712Sdes * list of supported mechanisms before privsep is set up. 74263712Sdes */ 75263712Sdesstatic gss_OID_set supported_oids; 76181111Sdes 77263712Sdesvoid 78263712Sdesssh_gssapi_prepare_supported_oids(void) 79263712Sdes{ 80263712Sdes ssh_gssapi_supported_oids(&supported_oids); 81263712Sdes} 82263712Sdes 83263712SdesOM_uint32 84263712Sdesssh_gssapi_test_oid_supported(OM_uint32 *ms, gss_OID member, int *present) 85263712Sdes{ 86263712Sdes if (supported_oids == NULL) 87263712Sdes ssh_gssapi_prepare_supported_oids(); 88263712Sdes return gss_test_oid_set_member(ms, member, supported_oids, present); 89263712Sdes} 90263712Sdes 91181111Sdes/* 92181111Sdes * Acquire credentials for a server running on the current host. 93181111Sdes * Requires that the context structure contains a valid OID 94181111Sdes */ 95181111Sdes 96181111Sdes/* Returns a GSSAPI error code */ 97181111Sdes/* Privileged (called from ssh_gssapi_server_ctx) */ 98181111Sdesstatic OM_uint32 99181111Sdesssh_gssapi_acquire_cred(Gssctxt *ctx) 100181111Sdes{ 101181111Sdes OM_uint32 status; 102294328Sdes char lname[NI_MAXHOST]; 103181111Sdes gss_OID_set oidset; 104181111Sdes 105294336Sdes if (options.gss_strict_acceptor) { 106294336Sdes gss_create_empty_oid_set(&status, &oidset); 107294336Sdes gss_add_oid_set_member(&status, ctx->oid, &oidset); 108181111Sdes 109294336Sdes if (gethostname(lname, MAXHOSTNAMELEN)) { 110294336Sdes gss_release_oid_set(&status, &oidset); 111294336Sdes return (-1); 112294336Sdes } 113181111Sdes 114294336Sdes if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) { 115294336Sdes gss_release_oid_set(&status, &oidset); 116294336Sdes return (ctx->major); 117294336Sdes } 118294336Sdes 119294336Sdes if ((ctx->major = gss_acquire_cred(&ctx->minor, 120294336Sdes ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, 121294336Sdes NULL, NULL))) 122294336Sdes ssh_gssapi_error(ctx); 123294336Sdes 124181111Sdes gss_release_oid_set(&status, &oidset); 125181111Sdes return (ctx->major); 126294336Sdes } else { 127294336Sdes ctx->name = GSS_C_NO_NAME; 128294336Sdes ctx->creds = GSS_C_NO_CREDENTIAL; 129181111Sdes } 130294336Sdes return GSS_S_COMPLETE; 131181111Sdes} 132181111Sdes 133181111Sdes/* Privileged */ 134181111SdesOM_uint32 135181111Sdesssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid) 136181111Sdes{ 137181111Sdes if (*ctx) 138181111Sdes ssh_gssapi_delete_ctx(ctx); 139181111Sdes ssh_gssapi_build_ctx(ctx); 140181111Sdes ssh_gssapi_set_oid(*ctx, oid); 141181111Sdes return (ssh_gssapi_acquire_cred(*ctx)); 142181111Sdes} 143181111Sdes 144157016Sdes/* Unprivileged */ 145124208Sdesvoid 146124208Sdesssh_gssapi_supported_oids(gss_OID_set *oidset) 147124208Sdes{ 148124208Sdes int i = 0; 149124208Sdes OM_uint32 min_status; 150124208Sdes int present; 151124208Sdes gss_OID_set supported; 152124208Sdes 153124208Sdes gss_create_empty_oid_set(&min_status, oidset); 154124208Sdes gss_indicate_mechs(&min_status, &supported); 155124208Sdes 156124208Sdes while (supported_mechs[i]->name != NULL) { 157124208Sdes if (GSS_ERROR(gss_test_oid_set_member(&min_status, 158124208Sdes &supported_mechs[i]->oid, supported, &present))) 159124208Sdes present = 0; 160124208Sdes if (present) 161124208Sdes gss_add_oid_set_member(&min_status, 162124208Sdes &supported_mechs[i]->oid, oidset); 163124208Sdes i++; 164124208Sdes } 165162852Sdes 166162852Sdes gss_release_oid_set(&min_status, &supported); 167124208Sdes} 168124208Sdes 169124208Sdes 170124208Sdes/* Wrapper around accept_sec_context 171124208Sdes * Requires that the context contains: 172124208Sdes * oid 173124208Sdes * credentials (from ssh_gssapi_acquire_cred) 174124208Sdes */ 175157016Sdes/* Privileged */ 176124208SdesOM_uint32 177124208Sdesssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok, 178124208Sdes gss_buffer_desc *send_tok, OM_uint32 *flags) 179124208Sdes{ 180124208Sdes OM_uint32 status; 181124208Sdes gss_OID mech; 182124208Sdes 183124208Sdes ctx->major = gss_accept_sec_context(&ctx->minor, 184124208Sdes &ctx->context, ctx->creds, recv_tok, 185124208Sdes GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech, 186124208Sdes send_tok, flags, NULL, &ctx->client_creds); 187124208Sdes 188124208Sdes if (GSS_ERROR(ctx->major)) 189124208Sdes ssh_gssapi_error(ctx); 190124208Sdes 191124208Sdes if (ctx->client_creds) 192124208Sdes debug("Received some client credentials"); 193124208Sdes else 194124208Sdes debug("Got no client credentials"); 195124208Sdes 196124208Sdes status = ctx->major; 197124208Sdes 198124208Sdes /* Now, if we're complete and we have the right flags, then 199124208Sdes * we flag the user as also having been authenticated 200124208Sdes */ 201124208Sdes 202124208Sdes if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) && 203124208Sdes (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) { 204124208Sdes if (ssh_gssapi_getclient(ctx, &gssapi_client)) 205124208Sdes fatal("Couldn't convert client name"); 206124208Sdes } 207124208Sdes 208124208Sdes return (status); 209124208Sdes} 210124208Sdes 211124208Sdes/* 212124208Sdes * This parses an exported name, extracting the mechanism specific portion 213124208Sdes * to use for ACL checking. It verifies that the name belongs the mechanism 214124208Sdes * originally selected. 215124208Sdes */ 216124208Sdesstatic OM_uint32 217124208Sdesssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name) 218124208Sdes{ 219149749Sdes u_char *tok; 220124208Sdes OM_uint32 offset; 221124208Sdes OM_uint32 oidl; 222124208Sdes 223157016Sdes tok = ename->value; 224124208Sdes 225124208Sdes /* 226124208Sdes * Check that ename is long enough for all of the fixed length 227124208Sdes * header, and that the initial ID bytes are correct 228124208Sdes */ 229124208Sdes 230157016Sdes if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0) 231124208Sdes return GSS_S_FAILURE; 232124208Sdes 233124208Sdes /* 234124208Sdes * Extract the OID, and check it. Here GSSAPI breaks with tradition 235124208Sdes * and does use the OID type and length bytes. To confuse things 236124208Sdes * there are two lengths - the first including these, and the 237124208Sdes * second without. 238124208Sdes */ 239124208Sdes 240162852Sdes oidl = get_u16(tok+2); /* length including next two bytes */ 241124208Sdes oidl = oidl-2; /* turn it into the _real_ length of the variable OID */ 242124208Sdes 243124208Sdes /* 244124208Sdes * Check the BER encoding for correct type and length, that the 245124208Sdes * string is long enough and that the OID matches that in our context 246124208Sdes */ 247124208Sdes if (tok[4] != 0x06 || tok[5] != oidl || 248124208Sdes ename->length < oidl+6 || 249157016Sdes !ssh_gssapi_check_oid(ctx, tok+6, oidl)) 250124208Sdes return GSS_S_FAILURE; 251124208Sdes 252124208Sdes offset = oidl+6; 253124208Sdes 254124208Sdes if (ename->length < offset+4) 255124208Sdes return GSS_S_FAILURE; 256124208Sdes 257162852Sdes name->length = get_u32(tok+offset); 258124208Sdes offset += 4; 259124208Sdes 260226046Sdes if (UINT_MAX - offset < name->length) 261226046Sdes return GSS_S_FAILURE; 262124208Sdes if (ename->length < offset+name->length) 263124208Sdes return GSS_S_FAILURE; 264124208Sdes 265124208Sdes name->value = xmalloc(name->length+1); 266162852Sdes memcpy(name->value, tok+offset, name->length); 267124208Sdes ((char *)name->value)[name->length] = 0; 268124208Sdes 269124208Sdes return GSS_S_COMPLETE; 270124208Sdes} 271124208Sdes 272124208Sdes/* Extract the client details from a given context. This can only reliably 273124208Sdes * be called once for a context */ 274124208Sdes 275157016Sdes/* Privileged (called from accept_secure_ctx) */ 276124208SdesOM_uint32 277124208Sdesssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client) 278124208Sdes{ 279124208Sdes int i = 0; 280124208Sdes 281124208Sdes gss_buffer_desc ename; 282124208Sdes 283124208Sdes client->mech = NULL; 284124208Sdes 285124208Sdes while (supported_mechs[i]->name != NULL) { 286124208Sdes if (supported_mechs[i]->oid.length == ctx->oid->length && 287124208Sdes (memcmp(supported_mechs[i]->oid.elements, 288124208Sdes ctx->oid->elements, ctx->oid->length) == 0)) 289124208Sdes client->mech = supported_mechs[i]; 290124208Sdes i++; 291124208Sdes } 292124208Sdes 293124208Sdes if (client->mech == NULL) 294124208Sdes return GSS_S_FAILURE; 295124208Sdes 296124208Sdes if ((ctx->major = gss_display_name(&ctx->minor, ctx->client, 297124208Sdes &client->displayname, NULL))) { 298124208Sdes ssh_gssapi_error(ctx); 299124208Sdes return (ctx->major); 300124208Sdes } 301124208Sdes 302124208Sdes if ((ctx->major = gss_export_name(&ctx->minor, ctx->client, 303124208Sdes &ename))) { 304124208Sdes ssh_gssapi_error(ctx); 305124208Sdes return (ctx->major); 306124208Sdes } 307124208Sdes 308124208Sdes if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename, 309124208Sdes &client->exportedname))) { 310124208Sdes return (ctx->major); 311124208Sdes } 312124208Sdes 313124208Sdes /* We can't copy this structure, so we just move the pointer to it */ 314124208Sdes client->creds = ctx->client_creds; 315124208Sdes ctx->client_creds = GSS_C_NO_CREDENTIAL; 316124208Sdes return (ctx->major); 317124208Sdes} 318124208Sdes 319126274Sdes/* As user - called on fatal/exit */ 320124208Sdesvoid 321126274Sdesssh_gssapi_cleanup_creds(void) 322124208Sdes{ 323124208Sdes if (gssapi_client.store.filename != NULL) { 324124208Sdes /* Unlink probably isn't sufficient */ 325162852Sdes debug("removing gssapi cred file\"%s\"", 326162852Sdes gssapi_client.store.filename); 327124208Sdes unlink(gssapi_client.store.filename); 328124208Sdes } 329124208Sdes} 330124208Sdes 331124208Sdes/* As user */ 332124208Sdesvoid 333124208Sdesssh_gssapi_storecreds(void) 334124208Sdes{ 335124208Sdes if (gssapi_client.mech && gssapi_client.mech->storecreds) { 336124208Sdes (*gssapi_client.mech->storecreds)(&gssapi_client); 337124208Sdes } else 338124208Sdes debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism"); 339124208Sdes} 340124208Sdes 341124208Sdes/* This allows GSSAPI methods to do things to the childs environment based 342124208Sdes * on the passed authentication process and credentials. 343124208Sdes */ 344124208Sdes/* As user */ 345124208Sdesvoid 346124208Sdesssh_gssapi_do_child(char ***envp, u_int *envsizep) 347124208Sdes{ 348124208Sdes 349124208Sdes if (gssapi_client.store.envvar != NULL && 350124208Sdes gssapi_client.store.envval != NULL) { 351124208Sdes debug("Setting %s to %s", gssapi_client.store.envvar, 352157016Sdes gssapi_client.store.envval); 353124208Sdes child_set_env(envp, envsizep, gssapi_client.store.envvar, 354149749Sdes gssapi_client.store.envval); 355124208Sdes } 356124208Sdes} 357124208Sdes 358157016Sdes/* Privileged */ 359124208Sdesint 360124208Sdesssh_gssapi_userok(char *user) 361124208Sdes{ 362149749Sdes OM_uint32 lmin; 363149749Sdes 364124208Sdes if (gssapi_client.exportedname.length == 0 || 365124208Sdes gssapi_client.exportedname.value == NULL) { 366124208Sdes debug("No suitable client data"); 367124208Sdes return 0; 368124208Sdes } 369124208Sdes if (gssapi_client.mech && gssapi_client.mech->userok) 370149749Sdes if ((*gssapi_client.mech->userok)(&gssapi_client, user)) 371149749Sdes return 1; 372149749Sdes else { 373149749Sdes /* Destroy delegated credentials if userok fails */ 374149749Sdes gss_release_buffer(&lmin, &gssapi_client.displayname); 375149749Sdes gss_release_buffer(&lmin, &gssapi_client.exportedname); 376149749Sdes gss_release_cred(&lmin, &gssapi_client.creds); 377263712Sdes explicit_bzero(&gssapi_client, 378263712Sdes sizeof(ssh_gssapi_client)); 379149749Sdes return 0; 380149749Sdes } 381124208Sdes else 382124208Sdes debug("ssh_gssapi_userok: Unknown GSSAPI mechanism"); 383124208Sdes return (0); 384124208Sdes} 385124208Sdes 386157016Sdes/* Privileged */ 387126274SdesOM_uint32 388126274Sdesssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic) 389126274Sdes{ 390126274Sdes ctx->major = gss_verify_mic(&ctx->minor, ctx->context, 391126274Sdes gssbuf, gssmic, NULL); 392126274Sdes 393126274Sdes return (ctx->major); 394126274Sdes} 395126274Sdes 396124208Sdes#endif 397