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
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:
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
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
27
/* Max amount of data we send/recv for SASL steps to prevent DOS */
28
#define SASL_DATA_MAX_LEN (1024 * 1024)
31
void vnc_sasl_client_cleanup(VncState *vs)
34
vs->sasl.runSSF = vs->sasl.waitWriteSSF = vs->sasl.wantSSF = 0;
35
vs->sasl.encodedLength = vs->sasl.encodedOffset = 0;
36
vs->sasl.encoded = NULL;
37
free(vs->sasl.username);
38
free(vs->sasl.mechlist);
39
vs->sasl.username = vs->sasl.mechlist = NULL;
40
sasl_dispose(&vs->sasl.conn);
46
long vnc_client_write_sasl(VncState *vs)
50
VNC_DEBUG("Write SASL: Pending output %p size %d offset %d Encoded: %p size %d offset %d\n",
51
vs->output.buffer, vs->output.capacity, vs->output.offset,
52
vs->sasl.encoded, vs->sasl.encodedLength, vs->sasl.encodedOffset);
54
if (!vs->sasl.encoded) {
56
err = sasl_encode(vs->sasl.conn,
57
(char *)vs->output.buffer,
59
(const char **)&vs->sasl.encoded,
60
&vs->sasl.encodedLength);
62
return vnc_client_io_error(vs, -1, EIO);
64
vs->sasl.encodedOffset = 0;
67
ret = vnc_client_write_buf(vs,
68
vs->sasl.encoded + vs->sasl.encodedOffset,
69
vs->sasl.encodedLength - vs->sasl.encodedOffset);
73
vs->sasl.encodedOffset += ret;
74
if (vs->sasl.encodedOffset == vs->sasl.encodedLength) {
75
vs->output.offset = 0;
76
vs->sasl.encoded = NULL;
77
vs->sasl.encodedOffset = vs->sasl.encodedLength = 0;
80
/* Can't merge this block with one above, because
81
* someone might have written more unencrypted
82
* data in vs->output while we were processing
85
if (vs->output.offset == 0) {
86
qemu_set_fd_handler2(vs->csock, NULL, vnc_client_read, NULL, vs);
93
long vnc_client_read_sasl(VncState *vs)
96
uint8_t encoded[4096];
98
unsigned int decodedLen;
101
ret = vnc_client_read_buf(vs, encoded, sizeof(encoded));
105
err = sasl_decode(vs->sasl.conn,
106
(char *)encoded, ret,
107
&decoded, &decodedLen);
110
return vnc_client_io_error(vs, -1, -EIO);
111
VNC_DEBUG("Read SASL Encoded %p size %ld Decoded %p size %d\n",
112
encoded, ret, decoded, decodedLen);
113
buffer_reserve(&vs->input, decodedLen);
114
buffer_append(&vs->input, decoded, decodedLen);
119
static int vnc_auth_sasl_check_access(VncState *vs)
125
err = sasl_getprop(vs->sasl.conn, SASL_USERNAME, &val);
126
if (err != SASL_OK) {
127
VNC_DEBUG("cannot query SASL username on connection %d (%s), denying access\n",
128
err, sasl_errstring(err, NULL, NULL));
132
VNC_DEBUG("no client username was found, denying access\n");
135
VNC_DEBUG("SASL client username %s\n", (const char *)val);
137
vs->sasl.username = qemu_strdup((const char*)val);
139
if (vs->vd->sasl.acl == NULL) {
140
VNC_DEBUG("no ACL activated, allowing access\n");
144
allow = qemu_acl_party_is_allowed(vs->vd->sasl.acl, vs->sasl.username);
146
VNC_DEBUG("SASL client %s %s by ACL\n", vs->sasl.username,
147
allow ? "allowed" : "denied");
148
return allow ? 0 : -1;
151
static int vnc_auth_sasl_check_ssf(VncState *vs)
156
if (!vs->sasl.wantSSF)
159
err = sasl_getprop(vs->sasl.conn, SASL_SSF, &val);
163
ssf = *(const int *)val;
164
VNC_DEBUG("negotiated an SSF of %d\n", ssf);
166
return 0; /* 56 is good for Kerberos */
168
/* Only setup for read initially, because we're about to send an RPC
169
* reply which must be in plain text. When the next incoming RPC
170
* arrives, we'll switch on writes too
172
* cf qemudClientReadSASL in qemud.c
176
/* We have a SSF that's good enough */
185
* u32 clientin-length
186
* u8-array clientin-string
190
* u32 serverout-length
191
* u8-array serverout-strin
195
static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len);
197
static int protocol_client_auth_sasl_step(VncState *vs, uint8_t *data, size_t len)
199
uint32_t datalen = len;
200
const char *serverout;
201
unsigned int serveroutlen;
203
char *clientdata = NULL;
205
/* NB, distinction of NULL vs "" is *critical* in SASL */
207
clientdata = (char*)data;
208
clientdata[datalen-1] = '\0'; /* Wire includes '\0', but make sure */
209
datalen--; /* Don't count NULL byte when passing to _start() */
212
VNC_DEBUG("Step using SASL Data %p (%d bytes)\n",
213
clientdata, datalen);
214
err = sasl_server_step(vs->sasl.conn,
219
if (err != SASL_OK &&
220
err != SASL_CONTINUE) {
221
VNC_DEBUG("sasl step failed %d (%s)\n",
222
err, sasl_errdetail(vs->sasl.conn));
223
sasl_dispose(&vs->sasl.conn);
224
vs->sasl.conn = NULL;
228
if (serveroutlen > SASL_DATA_MAX_LEN) {
229
VNC_DEBUG("sasl step reply data too long %d\n",
231
sasl_dispose(&vs->sasl.conn);
232
vs->sasl.conn = NULL;
236
VNC_DEBUG("SASL return data %d bytes, nil; %d\n",
237
serveroutlen, serverout ? 0 : 1);
240
vnc_write_u32(vs, serveroutlen + 1);
241
vnc_write(vs, serverout, serveroutlen + 1);
243
vnc_write_u32(vs, 0);
246
/* Whether auth is complete */
247
vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1);
249
if (err == SASL_CONTINUE) {
250
VNC_DEBUG("%s", "Authentication must continue\n");
251
/* Wait for step length */
252
vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4);
254
if (!vnc_auth_sasl_check_ssf(vs)) {
255
VNC_DEBUG("Authentication rejected for weak SSF %d\n", vs->csock);
259
/* Check username whitelist ACL */
260
if (vnc_auth_sasl_check_access(vs) < 0) {
261
VNC_DEBUG("Authentication rejected for ACL %d\n", vs->csock);
265
VNC_DEBUG("Authentication successful %d\n", vs->csock);
266
vnc_write_u32(vs, 0); /* Accept auth */
268
* Delay writing in SSF encoded mode until pending output
272
vs->sasl.waitWriteSSF = vs->output.offset;
273
start_client_init(vs);
279
vnc_write_u32(vs, 1); /* Reject auth */
280
vnc_write_u32(vs, sizeof("Authentication failed"));
281
vnc_write(vs, "Authentication failed", sizeof("Authentication failed"));
283
vnc_client_error(vs);
287
vnc_client_error(vs);
291
static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len)
293
uint32_t steplen = read_u32(data, 0);
294
VNC_DEBUG("Got client step len %d\n", steplen);
295
if (steplen > SASL_DATA_MAX_LEN) {
296
VNC_DEBUG("Too much SASL data %d\n", steplen);
297
vnc_client_error(vs);
302
return protocol_client_auth_sasl_step(vs, NULL, 0);
304
vnc_read_when(vs, protocol_client_auth_sasl_step, steplen);
313
* u32 clientin-length
314
* u8-array clientin-string
318
* u32 serverout-length
319
* u8-array serverout-strin
323
#define SASL_DATA_MAX_LEN (1024 * 1024)
325
static int protocol_client_auth_sasl_start(VncState *vs, uint8_t *data, size_t len)
327
uint32_t datalen = len;
328
const char *serverout;
329
unsigned int serveroutlen;
331
char *clientdata = NULL;
333
/* NB, distinction of NULL vs "" is *critical* in SASL */
335
clientdata = (char*)data;
336
clientdata[datalen-1] = '\0'; /* Should be on wire, but make sure */
337
datalen--; /* Don't count NULL byte when passing to _start() */
340
VNC_DEBUG("Start SASL auth with mechanism %s. Data %p (%d bytes)\n",
341
vs->sasl.mechlist, clientdata, datalen);
342
err = sasl_server_start(vs->sasl.conn,
348
if (err != SASL_OK &&
349
err != SASL_CONTINUE) {
350
VNC_DEBUG("sasl start failed %d (%s)\n",
351
err, sasl_errdetail(vs->sasl.conn));
352
sasl_dispose(&vs->sasl.conn);
353
vs->sasl.conn = NULL;
356
if (serveroutlen > SASL_DATA_MAX_LEN) {
357
VNC_DEBUG("sasl start reply data too long %d\n",
359
sasl_dispose(&vs->sasl.conn);
360
vs->sasl.conn = NULL;
364
VNC_DEBUG("SASL return data %d bytes, nil; %d\n",
365
serveroutlen, serverout ? 0 : 1);
368
vnc_write_u32(vs, serveroutlen + 1);
369
vnc_write(vs, serverout, serveroutlen + 1);
371
vnc_write_u32(vs, 0);
374
/* Whether auth is complete */
375
vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1);
377
if (err == SASL_CONTINUE) {
378
VNC_DEBUG("%s", "Authentication must continue\n");
379
/* Wait for step length */
380
vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4);
382
if (!vnc_auth_sasl_check_ssf(vs)) {
383
VNC_DEBUG("Authentication rejected for weak SSF %d\n", vs->csock);
387
/* Check username whitelist ACL */
388
if (vnc_auth_sasl_check_access(vs) < 0) {
389
VNC_DEBUG("Authentication rejected for ACL %d\n", vs->csock);
393
VNC_DEBUG("Authentication successful %d\n", vs->csock);
394
vnc_write_u32(vs, 0); /* Accept auth */
395
start_client_init(vs);
401
vnc_write_u32(vs, 1); /* Reject auth */
402
vnc_write_u32(vs, sizeof("Authentication failed"));
403
vnc_write(vs, "Authentication failed", sizeof("Authentication failed"));
405
vnc_client_error(vs);
409
vnc_client_error(vs);
413
static int protocol_client_auth_sasl_start_len(VncState *vs, uint8_t *data, size_t len)
415
uint32_t startlen = read_u32(data, 0);
416
VNC_DEBUG("Got client start len %d\n", startlen);
417
if (startlen > SASL_DATA_MAX_LEN) {
418
VNC_DEBUG("Too much SASL data %d\n", startlen);
419
vnc_client_error(vs);
424
return protocol_client_auth_sasl_start(vs, NULL, 0);
426
vnc_read_when(vs, protocol_client_auth_sasl_start, startlen);
430
static int protocol_client_auth_sasl_mechname(VncState *vs, uint8_t *data, size_t len)
432
char *mechname = malloc(len + 1);
434
VNC_DEBUG("Out of memory reading mechname\n");
435
vnc_client_error(vs);
437
strncpy(mechname, (char*)data, len);
438
mechname[len] = '\0';
439
VNC_DEBUG("Got client mechname '%s' check against '%s'\n",
440
mechname, vs->sasl.mechlist);
442
if (strncmp(vs->sasl.mechlist, mechname, len) == 0) {
443
if (vs->sasl.mechlist[len] != '\0' &&
444
vs->sasl.mechlist[len] != ',') {
445
VNC_DEBUG("One %d", vs->sasl.mechlist[len]);
446
vnc_client_error(vs);
450
char *offset = strstr(vs->sasl.mechlist, mechname);
451
VNC_DEBUG("Two %p\n", offset);
453
vnc_client_error(vs);
456
VNC_DEBUG("Two '%s'\n", offset);
457
if (offset[-1] != ',' ||
458
(offset[len] != '\0'&&
459
offset[len] != ',')) {
460
vnc_client_error(vs);
465
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
static int protocol_client_auth_sasl_mechname_len(VncState *vs, uint8_t *data, size_t len)
475
uint32_t mechlen = read_u32(data, 0);
476
VNC_DEBUG("Got client mechname len %d\n", mechlen);
478
VNC_DEBUG("Too long SASL mechname data %d\n", mechlen);
479
vnc_client_error(vs);
483
VNC_DEBUG("Too short SASL mechname %d\n", mechlen);
484
vnc_client_error(vs);
487
vnc_read_when(vs, protocol_client_auth_sasl_mechname,mechlen);
491
#define USES_X509_AUTH(vs) \
492
((vs)->subauth == VNC_AUTH_VENCRYPT_X509NONE || \
493
(vs)->subauth == VNC_AUTH_VENCRYPT_X509VNC || \
494
(vs)->subauth == VNC_AUTH_VENCRYPT_X509PLAIN || \
495
(vs)->subauth == VNC_AUTH_VENCRYPT_X509SASL)
498
void start_auth_sasl(VncState *vs)
500
const char *mechlist = NULL;
501
sasl_security_properties_t secprops;
503
char *localAddr, *remoteAddr;
506
VNC_DEBUG("Initialize SASL auth %d\n", vs->csock);
508
/* Get local & remote client addresses in form IPADDR;PORT */
509
if (!(localAddr = vnc_socket_local_addr("%s;%s", vs->csock)))
512
if (!(remoteAddr = vnc_socket_remote_addr("%s;%s", vs->csock))) {
517
err = sasl_server_new("vnc",
518
NULL, /* FQDN - just delegates to gethostname */
519
NULL, /* User realm */
522
NULL, /* Callbacks, not needed */
527
localAddr = remoteAddr = NULL;
529
if (err != SASL_OK) {
530
VNC_DEBUG("sasl context setup failed %d (%s)",
531
err, sasl_errstring(err, NULL, NULL));
532
vs->sasl.conn = NULL;
536
#ifdef CONFIG_VNC_TLS
537
/* Inform SASL that we've got an external SSF layer from TLS/x509 */
538
if (vs->vd->auth == VNC_AUTH_VENCRYPT &&
539
vs->vd->subauth == VNC_AUTH_VENCRYPT_X509SASL) {
540
gnutls_cipher_algorithm_t cipher;
543
cipher = gnutls_cipher_get(vs->tls.session);
544
if (!(ssf = (sasl_ssf_t)gnutls_cipher_get_key_size(cipher))) {
545
VNC_DEBUG("%s", "cannot TLS get cipher size\n");
546
sasl_dispose(&vs->sasl.conn);
547
vs->sasl.conn = NULL;
550
ssf *= 8; /* tls key size is bytes, sasl wants bits */
552
err = sasl_setprop(vs->sasl.conn, SASL_SSF_EXTERNAL, &ssf);
553
if (err != SASL_OK) {
554
VNC_DEBUG("cannot set SASL external SSF %d (%s)\n",
555
err, sasl_errstring(err, NULL, NULL));
556
sasl_dispose(&vs->sasl.conn);
557
vs->sasl.conn = NULL;
561
#endif /* CONFIG_VNC_TLS */
562
vs->sasl.wantSSF = 1;
564
memset (&secprops, 0, sizeof secprops);
565
/* Inform SASL that we've got an external SSF layer from TLS */
566
if (strncmp(vs->vd->display, "unix:", 5) == 0
567
#ifdef CONFIG_VNC_TLS
568
/* Disable SSF, if using TLS+x509+SASL only. TLS without x509
569
is not sufficiently strong */
570
|| (vs->vd->auth == VNC_AUTH_VENCRYPT &&
571
vs->vd->subauth == VNC_AUTH_VENCRYPT_X509SASL)
572
#endif /* CONFIG_VNC_TLS */
574
/* If we've got TLS or UNIX domain sock, we don't care about SSF */
575
secprops.min_ssf = 0;
576
secprops.max_ssf = 0;
577
secprops.maxbufsize = 8192;
578
secprops.security_flags = 0;
580
/* Plain TCP, better get an SSF layer */
581
secprops.min_ssf = 56; /* Good enough to require kerberos */
582
secprops.max_ssf = 100000; /* Arbitrary big number */
583
secprops.maxbufsize = 8192;
584
/* Forbid any anonymous or trivially crackable auth */
585
secprops.security_flags =
586
SASL_SEC_NOANONYMOUS | SASL_SEC_NOPLAINTEXT;
589
err = sasl_setprop(vs->sasl.conn, SASL_SEC_PROPS, &secprops);
590
if (err != SASL_OK) {
591
VNC_DEBUG("cannot set SASL security props %d (%s)\n",
592
err, sasl_errstring(err, NULL, NULL));
593
sasl_dispose(&vs->sasl.conn);
594
vs->sasl.conn = NULL;
598
err = sasl_listmech(vs->sasl.conn,
599
NULL, /* Don't need to set user */
606
if (err != SASL_OK) {
607
VNC_DEBUG("cannot list SASL mechanisms %d (%s)\n",
608
err, sasl_errdetail(vs->sasl.conn));
609
sasl_dispose(&vs->sasl.conn);
610
vs->sasl.conn = NULL;
613
VNC_DEBUG("Available mechanisms for client: '%s'\n", mechlist);
615
if (!(vs->sasl.mechlist = strdup(mechlist))) {
616
VNC_DEBUG("Out of memory");
617
sasl_dispose(&vs->sasl.conn);
618
vs->sasl.conn = NULL;
621
mechlistlen = strlen(mechlist);
622
vnc_write_u32(vs, mechlistlen);
623
vnc_write(vs, mechlist, mechlistlen);
626
VNC_DEBUG("Wait for client mechname length\n");
627
vnc_read_when(vs, protocol_client_auth_sasl_mechname_len, 4);
632
vnc_client_error(vs);