vnc-auth-sasl.c (20838B)
1 /* 2 * QEMU VNC display driver: SASL auth protocol 3 * 4 * Copyright (C) 2009 Red Hat, Inc 5 * 6 * Permission is hereby granted, free of charge, to any person obtaining a copy 7 * of this software and associated documentation files (the "Software"), to deal 8 * in the Software without restriction, including without limitation the rights 9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 10 * copies of the Software, and to permit persons to whom the Software is 11 * furnished to do so, subject to the following conditions: 12 * 13 * The above copyright notice and this permission notice shall be included in 14 * all copies or substantial portions of the Software. 15 * 16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 22 * THE SOFTWARE. 23 */ 24 25 #include "qemu/osdep.h" 26 #include "qapi/error.h" 27 #include "authz/base.h" 28 #include "vnc.h" 29 #include "trace.h" 30 31 /* 32 * Apple has deprecated sasl.h functions in OS X 10.11. Therefore, 33 * files that use SASL API need to disable -Wdeprecated-declarations. 34 */ 35 #ifdef CONFIG_DARWIN 36 #pragma GCC diagnostic ignored "-Wdeprecated-declarations" 37 #endif 38 39 /* Max amount of data we send/recv for SASL steps to prevent DOS */ 40 #define SASL_DATA_MAX_LEN (1024 * 1024) 41 42 43 bool vnc_sasl_server_init(Error **errp) 44 { 45 int saslErr = sasl_server_init(NULL, "qemu"); 46 47 if (saslErr != SASL_OK) { 48 error_setg(errp, "Failed to initialize SASL auth: %s", 49 sasl_errstring(saslErr, NULL, NULL)); 50 return false; 51 } 52 return true; 53 } 54 55 void vnc_sasl_client_cleanup(VncState *vs) 56 { 57 if (vs->sasl.conn) { 58 vs->sasl.runSSF = false; 59 vs->sasl.wantSSF = false; 60 vs->sasl.waitWriteSSF = 0; 61 vs->sasl.encodedLength = vs->sasl.encodedOffset = 0; 62 vs->sasl.encoded = NULL; 63 g_free(vs->sasl.username); 64 g_free(vs->sasl.mechlist); 65 vs->sasl.username = vs->sasl.mechlist = NULL; 66 sasl_dispose(&vs->sasl.conn); 67 vs->sasl.conn = NULL; 68 } 69 } 70 71 72 size_t vnc_client_write_sasl(VncState *vs) 73 { 74 size_t ret; 75 76 VNC_DEBUG("Write SASL: Pending output %p size %zd offset %zd " 77 "Encoded: %p size %d offset %d\n", 78 vs->output.buffer, vs->output.capacity, vs->output.offset, 79 vs->sasl.encoded, vs->sasl.encodedLength, vs->sasl.encodedOffset); 80 81 if (!vs->sasl.encoded) { 82 int err; 83 err = sasl_encode(vs->sasl.conn, 84 (char *)vs->output.buffer, 85 vs->output.offset, 86 (const char **)&vs->sasl.encoded, 87 &vs->sasl.encodedLength); 88 if (err != SASL_OK) 89 return vnc_client_io_error(vs, -1, NULL); 90 91 vs->sasl.encodedRawLength = vs->output.offset; 92 vs->sasl.encodedOffset = 0; 93 } 94 95 ret = vnc_client_write_buf(vs, 96 vs->sasl.encoded + vs->sasl.encodedOffset, 97 vs->sasl.encodedLength - vs->sasl.encodedOffset); 98 if (!ret) 99 return 0; 100 101 vs->sasl.encodedOffset += ret; 102 if (vs->sasl.encodedOffset == vs->sasl.encodedLength) { 103 bool throttled = vs->force_update_offset != 0; 104 size_t offset; 105 if (vs->sasl.encodedRawLength >= vs->force_update_offset) { 106 vs->force_update_offset = 0; 107 } else { 108 vs->force_update_offset -= vs->sasl.encodedRawLength; 109 } 110 if (throttled && vs->force_update_offset == 0) { 111 trace_vnc_client_unthrottle_forced(vs, vs->ioc); 112 } 113 offset = vs->output.offset; 114 buffer_advance(&vs->output, vs->sasl.encodedRawLength); 115 if (offset >= vs->throttle_output_offset && 116 vs->output.offset < vs->throttle_output_offset) { 117 trace_vnc_client_unthrottle_incremental(vs, vs->ioc, 118 vs->output.offset); 119 } 120 vs->sasl.encoded = NULL; 121 vs->sasl.encodedOffset = vs->sasl.encodedLength = 0; 122 } 123 124 /* Can't merge this block with one above, because 125 * someone might have written more unencrypted 126 * data in vs->output while we were processing 127 * SASL encoded output 128 */ 129 if (vs->output.offset == 0) { 130 if (vs->ioc_tag) { 131 g_source_remove(vs->ioc_tag); 132 } 133 vs->ioc_tag = qio_channel_add_watch( 134 vs->ioc, G_IO_IN | G_IO_HUP | G_IO_ERR, 135 vnc_client_io, vs, NULL); 136 } 137 138 return ret; 139 } 140 141 142 size_t vnc_client_read_sasl(VncState *vs) 143 { 144 size_t ret; 145 uint8_t encoded[4096]; 146 const char *decoded; 147 unsigned int decodedLen; 148 int err; 149 150 ret = vnc_client_read_buf(vs, encoded, sizeof(encoded)); 151 if (!ret) 152 return 0; 153 154 err = sasl_decode(vs->sasl.conn, 155 (char *)encoded, ret, 156 &decoded, &decodedLen); 157 158 if (err != SASL_OK) 159 return vnc_client_io_error(vs, -1, NULL); 160 VNC_DEBUG("Read SASL Encoded %p size %ld Decoded %p size %d\n", 161 encoded, ret, decoded, decodedLen); 162 buffer_reserve(&vs->input, decodedLen); 163 buffer_append(&vs->input, decoded, decodedLen); 164 return decodedLen; 165 } 166 167 168 static int vnc_auth_sasl_check_access(VncState *vs) 169 { 170 const void *val; 171 int rv; 172 Error *err = NULL; 173 bool allow; 174 175 rv = sasl_getprop(vs->sasl.conn, SASL_USERNAME, &val); 176 if (rv != SASL_OK) { 177 trace_vnc_auth_fail(vs, vs->auth, "Cannot fetch SASL username", 178 sasl_errstring(rv, NULL, NULL)); 179 return -1; 180 } 181 if (val == NULL) { 182 trace_vnc_auth_fail(vs, vs->auth, "No SASL username set", ""); 183 return -1; 184 } 185 186 vs->sasl.username = g_strdup((const char*)val); 187 trace_vnc_auth_sasl_username(vs, vs->sasl.username); 188 189 if (vs->vd->sasl.authzid == NULL) { 190 trace_vnc_auth_sasl_acl(vs, 1); 191 return 0; 192 } 193 194 allow = qauthz_is_allowed_by_id(vs->vd->sasl.authzid, 195 vs->sasl.username, &err); 196 if (err) { 197 trace_vnc_auth_fail(vs, vs->auth, "Error from authz", 198 error_get_pretty(err)); 199 error_free(err); 200 return -1; 201 } 202 203 trace_vnc_auth_sasl_acl(vs, allow); 204 return allow ? 0 : -1; 205 } 206 207 static int vnc_auth_sasl_check_ssf(VncState *vs) 208 { 209 const void *val; 210 int err, ssf; 211 212 if (!vs->sasl.wantSSF) 213 return 1; 214 215 err = sasl_getprop(vs->sasl.conn, SASL_SSF, &val); 216 if (err != SASL_OK) 217 return 0; 218 219 ssf = *(const int *)val; 220 221 trace_vnc_auth_sasl_ssf(vs, ssf); 222 223 if (ssf < 56) 224 return 0; /* 56 is good for Kerberos */ 225 226 /* Only setup for read initially, because we're about to send an RPC 227 * reply which must be in plain text. When the next incoming RPC 228 * arrives, we'll switch on writes too 229 * 230 * cf qemudClientReadSASL in qemud.c 231 */ 232 vs->sasl.runSSF = 1; 233 234 /* We have a SSF that's good enough */ 235 return 1; 236 } 237 238 /* 239 * Step Msg 240 * 241 * Input from client: 242 * 243 * u32 clientin-length 244 * u8-array clientin-string 245 * 246 * Output to client: 247 * 248 * u32 serverout-length 249 * u8-array serverout-strin 250 * u8 continue 251 */ 252 253 static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len); 254 255 static int protocol_client_auth_sasl_step(VncState *vs, uint8_t *data, size_t len) 256 { 257 uint32_t datalen = len; 258 const char *serverout; 259 unsigned int serveroutlen; 260 int err; 261 char *clientdata = NULL; 262 263 /* NB, distinction of NULL vs "" is *critical* in SASL */ 264 if (datalen) { 265 clientdata = (char*)data; 266 clientdata[datalen-1] = '\0'; /* Wire includes '\0', but make sure */ 267 datalen--; /* Don't count NULL byte when passing to _start() */ 268 } 269 270 err = sasl_server_step(vs->sasl.conn, 271 clientdata, 272 datalen, 273 &serverout, 274 &serveroutlen); 275 trace_vnc_auth_sasl_step(vs, data, len, serverout, serveroutlen, err); 276 if (err != SASL_OK && 277 err != SASL_CONTINUE) { 278 trace_vnc_auth_fail(vs, vs->auth, "Cannot step SASL auth", 279 sasl_errdetail(vs->sasl.conn)); 280 sasl_dispose(&vs->sasl.conn); 281 vs->sasl.conn = NULL; 282 goto authabort; 283 } 284 285 if (serveroutlen > SASL_DATA_MAX_LEN) { 286 trace_vnc_auth_fail(vs, vs->auth, "SASL data too long", ""); 287 sasl_dispose(&vs->sasl.conn); 288 vs->sasl.conn = NULL; 289 goto authabort; 290 } 291 292 if (serveroutlen) { 293 vnc_write_u32(vs, serveroutlen + 1); 294 vnc_write(vs, serverout, serveroutlen + 1); 295 } else { 296 vnc_write_u32(vs, 0); 297 } 298 299 /* Whether auth is complete */ 300 vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1); 301 302 if (err == SASL_CONTINUE) { 303 /* Wait for step length */ 304 vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4); 305 } else { 306 if (!vnc_auth_sasl_check_ssf(vs)) { 307 trace_vnc_auth_fail(vs, vs->auth, "SASL SSF too weak", ""); 308 goto authreject; 309 } 310 311 /* Check the username access control list */ 312 if (vnc_auth_sasl_check_access(vs) < 0) { 313 goto authreject; 314 } 315 316 trace_vnc_auth_pass(vs, vs->auth); 317 vnc_write_u32(vs, 0); /* Accept auth */ 318 /* 319 * Delay writing in SSF encoded mode until pending output 320 * buffer is written 321 */ 322 if (vs->sasl.runSSF) 323 vs->sasl.waitWriteSSF = vs->output.offset; 324 start_client_init(vs); 325 } 326 327 return 0; 328 329 authreject: 330 vnc_write_u32(vs, 1); /* Reject auth */ 331 vnc_write_u32(vs, sizeof("Authentication failed")); 332 vnc_write(vs, "Authentication failed", sizeof("Authentication failed")); 333 vnc_flush(vs); 334 vnc_client_error(vs); 335 return -1; 336 337 authabort: 338 vnc_client_error(vs); 339 return -1; 340 } 341 342 static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len) 343 { 344 uint32_t steplen = read_u32(data, 0); 345 346 if (steplen > SASL_DATA_MAX_LEN) { 347 trace_vnc_auth_fail(vs, vs->auth, "SASL step len too large", ""); 348 vnc_client_error(vs); 349 return -1; 350 } 351 352 if (steplen == 0) 353 return protocol_client_auth_sasl_step(vs, NULL, 0); 354 else 355 vnc_read_when(vs, protocol_client_auth_sasl_step, steplen); 356 return 0; 357 } 358 359 /* 360 * Start Msg 361 * 362 * Input from client: 363 * 364 * u32 clientin-length 365 * u8-array clientin-string 366 * 367 * Output to client: 368 * 369 * u32 serverout-length 370 * u8-array serverout-strin 371 * u8 continue 372 */ 373 374 #define SASL_DATA_MAX_LEN (1024 * 1024) 375 376 static int protocol_client_auth_sasl_start(VncState *vs, uint8_t *data, size_t len) 377 { 378 uint32_t datalen = len; 379 const char *serverout; 380 unsigned int serveroutlen; 381 int err; 382 char *clientdata = NULL; 383 384 /* NB, distinction of NULL vs "" is *critical* in SASL */ 385 if (datalen) { 386 clientdata = (char*)data; 387 clientdata[datalen-1] = '\0'; /* Should be on wire, but make sure */ 388 datalen--; /* Don't count NULL byte when passing to _start() */ 389 } 390 391 err = sasl_server_start(vs->sasl.conn, 392 vs->sasl.mechlist, 393 clientdata, 394 datalen, 395 &serverout, 396 &serveroutlen); 397 trace_vnc_auth_sasl_start(vs, data, len, serverout, serveroutlen, err); 398 if (err != SASL_OK && 399 err != SASL_CONTINUE) { 400 trace_vnc_auth_fail(vs, vs->auth, "Cannot start SASL auth", 401 sasl_errdetail(vs->sasl.conn)); 402 sasl_dispose(&vs->sasl.conn); 403 vs->sasl.conn = NULL; 404 goto authabort; 405 } 406 if (serveroutlen > SASL_DATA_MAX_LEN) { 407 trace_vnc_auth_fail(vs, vs->auth, "SASL data too long", ""); 408 sasl_dispose(&vs->sasl.conn); 409 vs->sasl.conn = NULL; 410 goto authabort; 411 } 412 413 if (serveroutlen) { 414 vnc_write_u32(vs, serveroutlen + 1); 415 vnc_write(vs, serverout, serveroutlen + 1); 416 } else { 417 vnc_write_u32(vs, 0); 418 } 419 420 /* Whether auth is complete */ 421 vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1); 422 423 if (err == SASL_CONTINUE) { 424 /* Wait for step length */ 425 vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4); 426 } else { 427 if (!vnc_auth_sasl_check_ssf(vs)) { 428 trace_vnc_auth_fail(vs, vs->auth, "SASL SSF too weak", ""); 429 goto authreject; 430 } 431 432 /* Check the username access control list */ 433 if (vnc_auth_sasl_check_access(vs) < 0) { 434 goto authreject; 435 } 436 437 trace_vnc_auth_pass(vs, vs->auth); 438 vnc_write_u32(vs, 0); /* Accept auth */ 439 start_client_init(vs); 440 } 441 442 return 0; 443 444 authreject: 445 vnc_write_u32(vs, 1); /* Reject auth */ 446 vnc_write_u32(vs, sizeof("Authentication failed")); 447 vnc_write(vs, "Authentication failed", sizeof("Authentication failed")); 448 vnc_flush(vs); 449 vnc_client_error(vs); 450 return -1; 451 452 authabort: 453 vnc_client_error(vs); 454 return -1; 455 } 456 457 static int protocol_client_auth_sasl_start_len(VncState *vs, uint8_t *data, size_t len) 458 { 459 uint32_t startlen = read_u32(data, 0); 460 461 if (startlen > SASL_DATA_MAX_LEN) { 462 trace_vnc_auth_fail(vs, vs->auth, "SASL start len too large", ""); 463 vnc_client_error(vs); 464 return -1; 465 } 466 467 if (startlen == 0) 468 return protocol_client_auth_sasl_start(vs, NULL, 0); 469 470 vnc_read_when(vs, protocol_client_auth_sasl_start, startlen); 471 return 0; 472 } 473 474 static int protocol_client_auth_sasl_mechname(VncState *vs, uint8_t *data, size_t len) 475 { 476 char *mechname = g_strndup((const char *) data, len); 477 trace_vnc_auth_sasl_mech_choose(vs, mechname); 478 479 if (strncmp(vs->sasl.mechlist, mechname, len) == 0) { 480 if (vs->sasl.mechlist[len] != '\0' && 481 vs->sasl.mechlist[len] != ',') { 482 goto fail; 483 } 484 } else { 485 char *offset = strstr(vs->sasl.mechlist, mechname); 486 if (!offset) { 487 goto fail; 488 } 489 if (offset[-1] != ',' || 490 (offset[len] != '\0'&& 491 offset[len] != ',')) { 492 goto fail; 493 } 494 } 495 496 g_free(vs->sasl.mechlist); 497 vs->sasl.mechlist = mechname; 498 499 vnc_read_when(vs, protocol_client_auth_sasl_start_len, 4); 500 return 0; 501 502 fail: 503 trace_vnc_auth_fail(vs, vs->auth, "Unsupported mechname", mechname); 504 vnc_client_error(vs); 505 g_free(mechname); 506 return -1; 507 } 508 509 static int protocol_client_auth_sasl_mechname_len(VncState *vs, uint8_t *data, size_t len) 510 { 511 uint32_t mechlen = read_u32(data, 0); 512 513 if (mechlen > 100) { 514 trace_vnc_auth_fail(vs, vs->auth, "SASL mechname too long", ""); 515 vnc_client_error(vs); 516 return -1; 517 } 518 if (mechlen < 1) { 519 trace_vnc_auth_fail(vs, vs->auth, "SASL mechname too short", ""); 520 vnc_client_error(vs); 521 return -1; 522 } 523 vnc_read_when(vs, protocol_client_auth_sasl_mechname,mechlen); 524 return 0; 525 } 526 527 static char * 528 vnc_socket_ip_addr_string(QIOChannelSocket *ioc, 529 bool local, 530 Error **errp) 531 { 532 SocketAddress *addr; 533 char *ret; 534 535 if (local) { 536 addr = qio_channel_socket_get_local_address(ioc, errp); 537 } else { 538 addr = qio_channel_socket_get_remote_address(ioc, errp); 539 } 540 if (!addr) { 541 return NULL; 542 } 543 544 if (addr->type != SOCKET_ADDRESS_TYPE_INET) { 545 error_setg(errp, "Not an inet socket type"); 546 qapi_free_SocketAddress(addr); 547 return NULL; 548 } 549 ret = g_strdup_printf("%s;%s", addr->u.inet.host, addr->u.inet.port); 550 qapi_free_SocketAddress(addr); 551 return ret; 552 } 553 554 void start_auth_sasl(VncState *vs) 555 { 556 const char *mechlist = NULL; 557 sasl_security_properties_t secprops; 558 int err; 559 Error *local_err = NULL; 560 char *localAddr, *remoteAddr; 561 int mechlistlen; 562 563 /* Get local & remote client addresses in form IPADDR;PORT */ 564 localAddr = vnc_socket_ip_addr_string(vs->sioc, true, &local_err); 565 if (!localAddr) { 566 trace_vnc_auth_fail(vs, vs->auth, "Cannot format local IP", 567 error_get_pretty(local_err)); 568 goto authabort; 569 } 570 571 remoteAddr = vnc_socket_ip_addr_string(vs->sioc, false, &local_err); 572 if (!remoteAddr) { 573 trace_vnc_auth_fail(vs, vs->auth, "Cannot format remote IP", 574 error_get_pretty(local_err)); 575 g_free(localAddr); 576 goto authabort; 577 } 578 579 err = sasl_server_new("vnc", 580 NULL, /* FQDN - just delegates to gethostname */ 581 NULL, /* User realm */ 582 localAddr, 583 remoteAddr, 584 NULL, /* Callbacks, not needed */ 585 SASL_SUCCESS_DATA, 586 &vs->sasl.conn); 587 g_free(localAddr); 588 g_free(remoteAddr); 589 localAddr = remoteAddr = NULL; 590 591 if (err != SASL_OK) { 592 trace_vnc_auth_fail(vs, vs->auth, "SASL context setup failed", 593 sasl_errstring(err, NULL, NULL)); 594 vs->sasl.conn = NULL; 595 goto authabort; 596 } 597 598 /* Inform SASL that we've got an external SSF layer from TLS/x509 */ 599 if (vs->auth == VNC_AUTH_VENCRYPT && 600 vs->subauth == VNC_AUTH_VENCRYPT_X509SASL) { 601 int keysize; 602 sasl_ssf_t ssf; 603 604 keysize = qcrypto_tls_session_get_key_size(vs->tls, 605 &local_err); 606 if (keysize < 0) { 607 trace_vnc_auth_fail(vs, vs->auth, "cannot TLS get cipher size", 608 error_get_pretty(local_err)); 609 sasl_dispose(&vs->sasl.conn); 610 vs->sasl.conn = NULL; 611 goto authabort; 612 } 613 ssf = keysize * CHAR_BIT; /* tls key size is bytes, sasl wants bits */ 614 615 err = sasl_setprop(vs->sasl.conn, SASL_SSF_EXTERNAL, &ssf); 616 if (err != SASL_OK) { 617 trace_vnc_auth_fail(vs, vs->auth, "cannot set SASL external SSF", 618 sasl_errstring(err, NULL, NULL)); 619 sasl_dispose(&vs->sasl.conn); 620 vs->sasl.conn = NULL; 621 goto authabort; 622 } 623 } else { 624 vs->sasl.wantSSF = 1; 625 } 626 627 memset (&secprops, 0, sizeof secprops); 628 /* Inform SASL that we've got an external SSF layer from TLS. 629 * 630 * Disable SSF, if using TLS+x509+SASL only. TLS without x509 631 * is not sufficiently strong 632 */ 633 if (vs->vd->is_unix || 634 (vs->auth == VNC_AUTH_VENCRYPT && 635 vs->subauth == VNC_AUTH_VENCRYPT_X509SASL)) { 636 /* If we've got TLS or UNIX domain sock, we don't care about SSF */ 637 secprops.min_ssf = 0; 638 secprops.max_ssf = 0; 639 secprops.maxbufsize = 8192; 640 secprops.security_flags = 0; 641 } else { 642 /* Plain TCP, better get an SSF layer */ 643 secprops.min_ssf = 56; /* Good enough to require kerberos */ 644 secprops.max_ssf = 100000; /* Arbitrary big number */ 645 secprops.maxbufsize = 8192; 646 /* Forbid any anonymous or trivially crackable auth */ 647 secprops.security_flags = 648 SASL_SEC_NOANONYMOUS | SASL_SEC_NOPLAINTEXT; 649 } 650 651 err = sasl_setprop(vs->sasl.conn, SASL_SEC_PROPS, &secprops); 652 if (err != SASL_OK) { 653 trace_vnc_auth_fail(vs, vs->auth, "cannot set SASL security props", 654 sasl_errstring(err, NULL, NULL)); 655 sasl_dispose(&vs->sasl.conn); 656 vs->sasl.conn = NULL; 657 goto authabort; 658 } 659 660 err = sasl_listmech(vs->sasl.conn, 661 NULL, /* Don't need to set user */ 662 "", /* Prefix */ 663 ",", /* Separator */ 664 "", /* Suffix */ 665 &mechlist, 666 NULL, 667 NULL); 668 if (err != SASL_OK) { 669 trace_vnc_auth_fail(vs, vs->auth, "cannot list SASL mechanisms", 670 sasl_errdetail(vs->sasl.conn)); 671 sasl_dispose(&vs->sasl.conn); 672 vs->sasl.conn = NULL; 673 goto authabort; 674 } 675 trace_vnc_auth_sasl_mech_list(vs, mechlist); 676 677 vs->sasl.mechlist = g_strdup(mechlist); 678 mechlistlen = strlen(mechlist); 679 vnc_write_u32(vs, mechlistlen); 680 vnc_write(vs, mechlist, mechlistlen); 681 vnc_flush(vs); 682 683 vnc_read_when(vs, protocol_client_auth_sasl_mechname_len, 4); 684 685 return; 686 687 authabort: 688 error_free(local_err); 689 vnc_client_error(vs); 690 } 691 692