2 * QEMU VNC display driver: SASL auth protocol
4 * Copyright (C) 2009 Red Hat, Inc
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
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10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
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
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25 #include "qemu/osdep.h"
26 #include "qapi/error.h"
29 /* Max amount of data we send/recv for SASL steps to prevent DOS */
30 #define SASL_DATA_MAX_LEN (1024 * 1024)
33 void vnc_sasl_client_cleanup(VncState *vs)
36 vs->sasl.runSSF = false;
37 vs->sasl.wantSSF = false;
38 vs->sasl.waitWriteSSF = 0;
39 vs->sasl.encodedLength = vs->sasl.encodedOffset = 0;
40 vs->sasl.encoded = NULL;
41 g_free(vs->sasl.username);
42 g_free(vs->sasl.mechlist);
43 vs->sasl.username = vs->sasl.mechlist = NULL;
44 sasl_dispose(&vs->sasl.conn);
50 long vnc_client_write_sasl(VncState *vs)
54 VNC_DEBUG("Write SASL: Pending output %p size %zd offset %zd "
55 "Encoded: %p size %d offset %d\n",
56 vs->output.buffer, vs->output.capacity, vs->output.offset,
57 vs->sasl.encoded, vs->sasl.encodedLength, vs->sasl.encodedOffset);
59 if (!vs->sasl.encoded) {
61 err = sasl_encode(vs->sasl.conn,
62 (char *)vs->output.buffer,
64 (const char **)&vs->sasl.encoded,
65 &vs->sasl.encodedLength);
67 return vnc_client_io_error(vs, -1, NULL);
69 vs->sasl.encodedOffset = 0;
72 ret = vnc_client_write_buf(vs,
73 vs->sasl.encoded + vs->sasl.encodedOffset,
74 vs->sasl.encodedLength - vs->sasl.encodedOffset);
78 vs->sasl.encodedOffset += ret;
79 if (vs->sasl.encodedOffset == vs->sasl.encodedLength) {
80 vs->output.offset = 0;
81 vs->sasl.encoded = NULL;
82 vs->sasl.encodedOffset = vs->sasl.encodedLength = 0;
85 /* Can't merge this block with one above, because
86 * someone might have written more unencrypted
87 * data in vs->output while we were processing
90 if (vs->output.offset == 0) {
92 g_source_remove(vs->ioc_tag);
94 vs->ioc_tag = qio_channel_add_watch(
95 vs->ioc, G_IO_IN, vnc_client_io, vs, NULL);
102 long vnc_client_read_sasl(VncState *vs)
105 uint8_t encoded[4096];
107 unsigned int decodedLen;
110 ret = vnc_client_read_buf(vs, encoded, sizeof(encoded));
114 err = sasl_decode(vs->sasl.conn,
115 (char *)encoded, ret,
116 &decoded, &decodedLen);
119 return vnc_client_io_error(vs, -1, NULL);
120 VNC_DEBUG("Read SASL Encoded %p size %ld Decoded %p size %d\n",
121 encoded, ret, decoded, decodedLen);
122 buffer_reserve(&vs->input, decodedLen);
123 buffer_append(&vs->input, decoded, decodedLen);
128 static int vnc_auth_sasl_check_access(VncState *vs)
134 err = sasl_getprop(vs->sasl.conn, SASL_USERNAME, &val);
135 if (err != SASL_OK) {
136 VNC_DEBUG("cannot query SASL username on connection %d (%s), denying access\n",
137 err, sasl_errstring(err, NULL, NULL));
141 VNC_DEBUG("no client username was found, denying access\n");
144 VNC_DEBUG("SASL client username %s\n", (const char *)val);
146 vs->sasl.username = g_strdup((const char*)val);
148 if (vs->vd->sasl.acl == NULL) {
149 VNC_DEBUG("no ACL activated, allowing access\n");
153 allow = qemu_acl_party_is_allowed(vs->vd->sasl.acl, vs->sasl.username);
155 VNC_DEBUG("SASL client %s %s by ACL\n", vs->sasl.username,
156 allow ? "allowed" : "denied");
157 return allow ? 0 : -1;
160 static int vnc_auth_sasl_check_ssf(VncState *vs)
165 if (!vs->sasl.wantSSF)
168 err = sasl_getprop(vs->sasl.conn, SASL_SSF, &val);
172 ssf = *(const int *)val;
173 VNC_DEBUG("negotiated an SSF of %d\n", ssf);
175 return 0; /* 56 is good for Kerberos */
177 /* Only setup for read initially, because we're about to send an RPC
178 * reply which must be in plain text. When the next incoming RPC
179 * arrives, we'll switch on writes too
181 * cf qemudClientReadSASL in qemud.c
185 /* We have a SSF that's good enough */
194 * u32 clientin-length
195 * u8-array clientin-string
199 * u32 serverout-length
200 * u8-array serverout-strin
204 static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len);
206 static int protocol_client_auth_sasl_step(VncState *vs, uint8_t *data, size_t len)
208 uint32_t datalen = len;
209 const char *serverout;
210 unsigned int serveroutlen;
212 char *clientdata = NULL;
214 /* NB, distinction of NULL vs "" is *critical* in SASL */
216 clientdata = (char*)data;
217 clientdata[datalen-1] = '\0'; /* Wire includes '\0', but make sure */
218 datalen--; /* Don't count NULL byte when passing to _start() */
221 VNC_DEBUG("Step using SASL Data %p (%d bytes)\n",
222 clientdata, datalen);
223 err = sasl_server_step(vs->sasl.conn,
228 if (err != SASL_OK &&
229 err != SASL_CONTINUE) {
230 VNC_DEBUG("sasl step failed %d (%s)\n",
231 err, sasl_errdetail(vs->sasl.conn));
232 sasl_dispose(&vs->sasl.conn);
233 vs->sasl.conn = NULL;
237 if (serveroutlen > SASL_DATA_MAX_LEN) {
238 VNC_DEBUG("sasl step reply data too long %d\n",
240 sasl_dispose(&vs->sasl.conn);
241 vs->sasl.conn = NULL;
245 VNC_DEBUG("SASL return data %d bytes, nil; %d\n",
246 serveroutlen, serverout ? 0 : 1);
249 vnc_write_u32(vs, serveroutlen + 1);
250 vnc_write(vs, serverout, serveroutlen + 1);
252 vnc_write_u32(vs, 0);
255 /* Whether auth is complete */
256 vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1);
258 if (err == SASL_CONTINUE) {
259 VNC_DEBUG("%s", "Authentication must continue\n");
260 /* Wait for step length */
261 vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4);
263 if (!vnc_auth_sasl_check_ssf(vs)) {
264 VNC_DEBUG("Authentication rejected for weak SSF %p\n", vs->ioc);
268 /* Check username whitelist ACL */
269 if (vnc_auth_sasl_check_access(vs) < 0) {
270 VNC_DEBUG("Authentication rejected for ACL %p\n", vs->ioc);
274 VNC_DEBUG("Authentication successful %p\n", vs->ioc);
275 vnc_write_u32(vs, 0); /* Accept auth */
277 * Delay writing in SSF encoded mode until pending output
281 vs->sasl.waitWriteSSF = vs->output.offset;
282 start_client_init(vs);
288 vnc_write_u32(vs, 1); /* Reject auth */
289 vnc_write_u32(vs, sizeof("Authentication failed"));
290 vnc_write(vs, "Authentication failed", sizeof("Authentication failed"));
292 vnc_client_error(vs);
296 vnc_client_error(vs);
300 static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len)
302 uint32_t steplen = read_u32(data, 0);
303 VNC_DEBUG("Got client step len %d\n", steplen);
304 if (steplen > SASL_DATA_MAX_LEN) {
305 VNC_DEBUG("Too much SASL data %d\n", steplen);
306 vnc_client_error(vs);
311 return protocol_client_auth_sasl_step(vs, NULL, 0);
313 vnc_read_when(vs, protocol_client_auth_sasl_step, steplen);
322 * u32 clientin-length
323 * u8-array clientin-string
327 * u32 serverout-length
328 * u8-array serverout-strin
332 #define SASL_DATA_MAX_LEN (1024 * 1024)
334 static int protocol_client_auth_sasl_start(VncState *vs, uint8_t *data, size_t len)
336 uint32_t datalen = len;
337 const char *serverout;
338 unsigned int serveroutlen;
340 char *clientdata = NULL;
342 /* NB, distinction of NULL vs "" is *critical* in SASL */
344 clientdata = (char*)data;
345 clientdata[datalen-1] = '\0'; /* Should be on wire, but make sure */
346 datalen--; /* Don't count NULL byte when passing to _start() */
349 VNC_DEBUG("Start SASL auth with mechanism %s. Data %p (%d bytes)\n",
350 vs->sasl.mechlist, clientdata, datalen);
351 err = sasl_server_start(vs->sasl.conn,
357 if (err != SASL_OK &&
358 err != SASL_CONTINUE) {
359 VNC_DEBUG("sasl start failed %d (%s)\n",
360 err, sasl_errdetail(vs->sasl.conn));
361 sasl_dispose(&vs->sasl.conn);
362 vs->sasl.conn = NULL;
365 if (serveroutlen > SASL_DATA_MAX_LEN) {
366 VNC_DEBUG("sasl start reply data too long %d\n",
368 sasl_dispose(&vs->sasl.conn);
369 vs->sasl.conn = NULL;
373 VNC_DEBUG("SASL return data %d bytes, nil; %d\n",
374 serveroutlen, serverout ? 0 : 1);
377 vnc_write_u32(vs, serveroutlen + 1);
378 vnc_write(vs, serverout, serveroutlen + 1);
380 vnc_write_u32(vs, 0);
383 /* Whether auth is complete */
384 vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1);
386 if (err == SASL_CONTINUE) {
387 VNC_DEBUG("%s", "Authentication must continue\n");
388 /* Wait for step length */
389 vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4);
391 if (!vnc_auth_sasl_check_ssf(vs)) {
392 VNC_DEBUG("Authentication rejected for weak SSF %p\n", vs->ioc);
396 /* Check username whitelist ACL */
397 if (vnc_auth_sasl_check_access(vs) < 0) {
398 VNC_DEBUG("Authentication rejected for ACL %p\n", vs->ioc);
402 VNC_DEBUG("Authentication successful %p\n", vs->ioc);
403 vnc_write_u32(vs, 0); /* Accept auth */
404 start_client_init(vs);
410 vnc_write_u32(vs, 1); /* Reject auth */
411 vnc_write_u32(vs, sizeof("Authentication failed"));
412 vnc_write(vs, "Authentication failed", sizeof("Authentication failed"));
414 vnc_client_error(vs);
418 vnc_client_error(vs);
422 static int protocol_client_auth_sasl_start_len(VncState *vs, uint8_t *data, size_t len)
424 uint32_t startlen = read_u32(data, 0);
425 VNC_DEBUG("Got client start len %d\n", startlen);
426 if (startlen > SASL_DATA_MAX_LEN) {
427 VNC_DEBUG("Too much SASL data %d\n", startlen);
428 vnc_client_error(vs);
433 return protocol_client_auth_sasl_start(vs, NULL, 0);
435 vnc_read_when(vs, protocol_client_auth_sasl_start, startlen);
439 static int protocol_client_auth_sasl_mechname(VncState *vs, uint8_t *data, size_t len)
441 char *mechname = g_strndup((const char *) data, len);
442 VNC_DEBUG("Got client mechname '%s' check against '%s'\n",
443 mechname, vs->sasl.mechlist);
445 if (strncmp(vs->sasl.mechlist, mechname, len) == 0) {
446 if (vs->sasl.mechlist[len] != '\0' &&
447 vs->sasl.mechlist[len] != ',') {
448 VNC_DEBUG("One %d", vs->sasl.mechlist[len]);
452 char *offset = strstr(vs->sasl.mechlist, mechname);
453 VNC_DEBUG("Two %p\n", offset);
457 VNC_DEBUG("Two '%s'\n", offset);
458 if (offset[-1] != ',' ||
459 (offset[len] != '\0'&&
460 offset[len] != ',')) {
465 g_free(vs->sasl.mechlist);
466 vs->sasl.mechlist = mechname;
468 VNC_DEBUG("Validated mechname '%s'\n", mechname);
469 vnc_read_when(vs, protocol_client_auth_sasl_start_len, 4);
473 vnc_client_error(vs);
478 static int protocol_client_auth_sasl_mechname_len(VncState *vs, uint8_t *data, size_t len)
480 uint32_t mechlen = read_u32(data, 0);
481 VNC_DEBUG("Got client mechname len %d\n", mechlen);
483 VNC_DEBUG("Too long SASL mechname data %d\n", mechlen);
484 vnc_client_error(vs);
488 VNC_DEBUG("Too short SASL mechname %d\n", mechlen);
489 vnc_client_error(vs);
492 vnc_read_when(vs, protocol_client_auth_sasl_mechname,mechlen);
497 vnc_socket_ip_addr_string(QIOChannelSocket *ioc,
505 addr = qio_channel_socket_get_local_address(ioc, errp);
507 addr = qio_channel_socket_get_remote_address(ioc, errp);
513 if (addr->type != SOCKET_ADDRESS_KIND_INET) {
514 error_setg(errp, "Not an inet socket type");
517 ret = g_strdup_printf("%s;%s", addr->u.inet.data->host,
518 addr->u.inet.data->port);
519 qapi_free_SocketAddress(addr);
523 void start_auth_sasl(VncState *vs)
525 const char *mechlist = NULL;
526 sasl_security_properties_t secprops;
528 char *localAddr, *remoteAddr;
531 VNC_DEBUG("Initialize SASL auth %p\n", vs->ioc);
533 /* Get local & remote client addresses in form IPADDR;PORT */
534 localAddr = vnc_socket_ip_addr_string(vs->sioc, true, NULL);
539 remoteAddr = vnc_socket_ip_addr_string(vs->sioc, false, NULL);
545 err = sasl_server_new("vnc",
546 NULL, /* FQDN - just delegates to gethostname */
547 NULL, /* User realm */
550 NULL, /* Callbacks, not needed */
555 localAddr = remoteAddr = NULL;
557 if (err != SASL_OK) {
558 VNC_DEBUG("sasl context setup failed %d (%s)",
559 err, sasl_errstring(err, NULL, NULL));
560 vs->sasl.conn = NULL;
564 /* Inform SASL that we've got an external SSF layer from TLS/x509 */
565 if (vs->auth == VNC_AUTH_VENCRYPT &&
566 vs->subauth == VNC_AUTH_VENCRYPT_X509SASL) {
567 Error *local_err = NULL;
571 keysize = qcrypto_tls_session_get_key_size(vs->tls,
574 VNC_DEBUG("cannot TLS get cipher size: %s\n",
575 error_get_pretty(local_err));
576 error_free(local_err);
577 sasl_dispose(&vs->sasl.conn);
578 vs->sasl.conn = NULL;
581 ssf = keysize * CHAR_BIT; /* tls key size is bytes, sasl wants bits */
583 err = sasl_setprop(vs->sasl.conn, SASL_SSF_EXTERNAL, &ssf);
584 if (err != SASL_OK) {
585 VNC_DEBUG("cannot set SASL external SSF %d (%s)\n",
586 err, sasl_errstring(err, NULL, NULL));
587 sasl_dispose(&vs->sasl.conn);
588 vs->sasl.conn = NULL;
592 vs->sasl.wantSSF = 1;
595 memset (&secprops, 0, sizeof secprops);
596 /* Inform SASL that we've got an external SSF layer from TLS.
598 * Disable SSF, if using TLS+x509+SASL only. TLS without x509
599 * is not sufficiently strong
601 if (vs->vd->is_unix ||
602 (vs->auth == VNC_AUTH_VENCRYPT &&
603 vs->subauth == VNC_AUTH_VENCRYPT_X509SASL)) {
604 /* If we've got TLS or UNIX domain sock, we don't care about SSF */
605 secprops.min_ssf = 0;
606 secprops.max_ssf = 0;
607 secprops.maxbufsize = 8192;
608 secprops.security_flags = 0;
610 /* Plain TCP, better get an SSF layer */
611 secprops.min_ssf = 56; /* Good enough to require kerberos */
612 secprops.max_ssf = 100000; /* Arbitrary big number */
613 secprops.maxbufsize = 8192;
614 /* Forbid any anonymous or trivially crackable auth */
615 secprops.security_flags =
616 SASL_SEC_NOANONYMOUS | SASL_SEC_NOPLAINTEXT;
619 err = sasl_setprop(vs->sasl.conn, SASL_SEC_PROPS, &secprops);
620 if (err != SASL_OK) {
621 VNC_DEBUG("cannot set SASL security props %d (%s)\n",
622 err, sasl_errstring(err, NULL, NULL));
623 sasl_dispose(&vs->sasl.conn);
624 vs->sasl.conn = NULL;
628 err = sasl_listmech(vs->sasl.conn,
629 NULL, /* Don't need to set user */
636 if (err != SASL_OK) {
637 VNC_DEBUG("cannot list SASL mechanisms %d (%s)\n",
638 err, sasl_errdetail(vs->sasl.conn));
639 sasl_dispose(&vs->sasl.conn);
640 vs->sasl.conn = NULL;
643 VNC_DEBUG("Available mechanisms for client: '%s'\n", mechlist);
645 vs->sasl.mechlist = g_strdup(mechlist);
646 mechlistlen = strlen(mechlist);
647 vnc_write_u32(vs, mechlistlen);
648 vnc_write(vs, mechlist, mechlistlen);
651 VNC_DEBUG("Wait for client mechname length\n");
652 vnc_read_when(vs, protocol_client_auth_sasl_mechname_len, 4);
657 vnc_client_error(vs);