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1.1 root 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 "vnc.h"
26:
27: /* Max amount of data we send/recv for SASL steps to prevent DOS */
28: #define SASL_DATA_MAX_LEN (1024 * 1024)
29:
30:
31: void vnc_sasl_client_cleanup(VncState *vs)
32: {
33: if (vs->sasl.conn) {
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);
41: vs->sasl.conn = NULL;
42: }
43: }
44:
45:
46: long vnc_client_write_sasl(VncState *vs)
47: {
48: long ret;
49:
50: VNC_DEBUG("Write SASL: Pending output %p size %zd offset %zd "
51: "Encoded: %p size %d offset %d\n",
52: vs->output.buffer, vs->output.capacity, vs->output.offset,
53: vs->sasl.encoded, vs->sasl.encodedLength, vs->sasl.encodedOffset);
54:
55: if (!vs->sasl.encoded) {
56: int err;
57: err = sasl_encode(vs->sasl.conn,
58: (char *)vs->output.buffer,
59: vs->output.offset,
60: (const char **)&vs->sasl.encoded,
61: &vs->sasl.encodedLength);
62: if (err != SASL_OK)
63: return vnc_client_io_error(vs, -1, EIO);
64:
65: vs->sasl.encodedOffset = 0;
66: }
67:
68: ret = vnc_client_write_buf(vs,
69: vs->sasl.encoded + vs->sasl.encodedOffset,
70: vs->sasl.encodedLength - vs->sasl.encodedOffset);
71: if (!ret)
72: return 0;
73:
74: vs->sasl.encodedOffset += ret;
75: if (vs->sasl.encodedOffset == vs->sasl.encodedLength) {
76: vs->output.offset = 0;
77: vs->sasl.encoded = NULL;
78: vs->sasl.encodedOffset = vs->sasl.encodedLength = 0;
79: }
80:
81: /* Can't merge this block with one above, because
82: * someone might have written more unencrypted
83: * data in vs->output while we were processing
84: * SASL encoded output
85: */
86: if (vs->output.offset == 0) {
87: qemu_set_fd_handler2(vs->csock, NULL, vnc_client_read, NULL, vs);
88: }
89:
90: return ret;
91: }
92:
93:
94: long vnc_client_read_sasl(VncState *vs)
95: {
96: long ret;
97: uint8_t encoded[4096];
98: const char *decoded;
99: unsigned int decodedLen;
100: int err;
101:
102: ret = vnc_client_read_buf(vs, encoded, sizeof(encoded));
103: if (!ret)
104: return 0;
105:
106: err = sasl_decode(vs->sasl.conn,
107: (char *)encoded, ret,
108: &decoded, &decodedLen);
109:
110: if (err != SASL_OK)
111: return vnc_client_io_error(vs, -1, -EIO);
112: VNC_DEBUG("Read SASL Encoded %p size %ld Decoded %p size %d\n",
113: encoded, ret, decoded, decodedLen);
114: buffer_reserve(&vs->input, decodedLen);
115: buffer_append(&vs->input, decoded, decodedLen);
116: return decodedLen;
117: }
118:
119:
120: static int vnc_auth_sasl_check_access(VncState *vs)
121: {
122: const void *val;
123: int err;
124: int allow;
125:
126: err = sasl_getprop(vs->sasl.conn, SASL_USERNAME, &val);
127: if (err != SASL_OK) {
128: VNC_DEBUG("cannot query SASL username on connection %d (%s), denying access\n",
129: err, sasl_errstring(err, NULL, NULL));
130: return -1;
131: }
132: if (val == NULL) {
133: VNC_DEBUG("no client username was found, denying access\n");
134: return -1;
135: }
136: VNC_DEBUG("SASL client username %s\n", (const char *)val);
137:
138: vs->sasl.username = qemu_strdup((const char*)val);
139:
140: if (vs->vd->sasl.acl == NULL) {
141: VNC_DEBUG("no ACL activated, allowing access\n");
142: return 0;
143: }
144:
145: allow = qemu_acl_party_is_allowed(vs->vd->sasl.acl, vs->sasl.username);
146:
147: VNC_DEBUG("SASL client %s %s by ACL\n", vs->sasl.username,
148: allow ? "allowed" : "denied");
149: return allow ? 0 : -1;
150: }
151:
152: static int vnc_auth_sasl_check_ssf(VncState *vs)
153: {
154: const void *val;
155: int err, ssf;
156:
157: if (!vs->sasl.wantSSF)
158: return 1;
159:
160: err = sasl_getprop(vs->sasl.conn, SASL_SSF, &val);
161: if (err != SASL_OK)
162: return 0;
163:
164: ssf = *(const int *)val;
165: VNC_DEBUG("negotiated an SSF of %d\n", ssf);
166: if (ssf < 56)
167: return 0; /* 56 is good for Kerberos */
168:
169: /* Only setup for read initially, because we're about to send an RPC
170: * reply which must be in plain text. When the next incoming RPC
171: * arrives, we'll switch on writes too
172: *
173: * cf qemudClientReadSASL in qemud.c
174: */
175: vs->sasl.runSSF = 1;
176:
177: /* We have a SSF that's good enough */
178: return 1;
179: }
180:
181: /*
182: * Step Msg
183: *
184: * Input from client:
185: *
186: * u32 clientin-length
187: * u8-array clientin-string
188: *
189: * Output to client:
190: *
191: * u32 serverout-length
192: * u8-array serverout-strin
193: * u8 continue
194: */
195:
196: static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len);
197:
198: static int protocol_client_auth_sasl_step(VncState *vs, uint8_t *data, size_t len)
199: {
200: uint32_t datalen = len;
201: const char *serverout;
202: unsigned int serveroutlen;
203: int err;
204: char *clientdata = NULL;
205:
206: /* NB, distinction of NULL vs "" is *critical* in SASL */
207: if (datalen) {
208: clientdata = (char*)data;
209: clientdata[datalen-1] = '\0'; /* Wire includes '\0', but make sure */
210: datalen--; /* Don't count NULL byte when passing to _start() */
211: }
212:
213: VNC_DEBUG("Step using SASL Data %p (%d bytes)\n",
214: clientdata, datalen);
215: err = sasl_server_step(vs->sasl.conn,
216: clientdata,
217: datalen,
218: &serverout,
219: &serveroutlen);
220: if (err != SASL_OK &&
221: err != SASL_CONTINUE) {
222: VNC_DEBUG("sasl step failed %d (%s)\n",
223: err, sasl_errdetail(vs->sasl.conn));
224: sasl_dispose(&vs->sasl.conn);
225: vs->sasl.conn = NULL;
226: goto authabort;
227: }
228:
229: if (serveroutlen > SASL_DATA_MAX_LEN) {
230: VNC_DEBUG("sasl step reply data too long %d\n",
231: serveroutlen);
232: sasl_dispose(&vs->sasl.conn);
233: vs->sasl.conn = NULL;
234: goto authabort;
235: }
236:
237: VNC_DEBUG("SASL return data %d bytes, nil; %d\n",
238: serveroutlen, serverout ? 0 : 1);
239:
240: if (serveroutlen) {
241: vnc_write_u32(vs, serveroutlen + 1);
242: vnc_write(vs, serverout, serveroutlen + 1);
243: } else {
244: vnc_write_u32(vs, 0);
245: }
246:
247: /* Whether auth is complete */
248: vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1);
249:
250: if (err == SASL_CONTINUE) {
251: VNC_DEBUG("%s", "Authentication must continue\n");
252: /* Wait for step length */
253: vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4);
254: } else {
255: if (!vnc_auth_sasl_check_ssf(vs)) {
256: VNC_DEBUG("Authentication rejected for weak SSF %d\n", vs->csock);
257: goto authreject;
258: }
259:
260: /* Check username whitelist ACL */
261: if (vnc_auth_sasl_check_access(vs) < 0) {
262: VNC_DEBUG("Authentication rejected for ACL %d\n", vs->csock);
263: goto authreject;
264: }
265:
266: VNC_DEBUG("Authentication successful %d\n", vs->csock);
267: vnc_write_u32(vs, 0); /* Accept auth */
268: /*
269: * Delay writing in SSF encoded mode until pending output
270: * buffer is written
271: */
272: if (vs->sasl.runSSF)
273: vs->sasl.waitWriteSSF = vs->output.offset;
274: start_client_init(vs);
275: }
276:
277: return 0;
278:
279: authreject:
280: vnc_write_u32(vs, 1); /* Reject auth */
281: vnc_write_u32(vs, sizeof("Authentication failed"));
282: vnc_write(vs, "Authentication failed", sizeof("Authentication failed"));
283: vnc_flush(vs);
284: vnc_client_error(vs);
285: return -1;
286:
287: authabort:
288: vnc_client_error(vs);
289: return -1;
290: }
291:
292: static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len)
293: {
294: uint32_t steplen = read_u32(data, 0);
295: VNC_DEBUG("Got client step len %d\n", steplen);
296: if (steplen > SASL_DATA_MAX_LEN) {
297: VNC_DEBUG("Too much SASL data %d\n", steplen);
298: vnc_client_error(vs);
299: return -1;
300: }
301:
302: if (steplen == 0)
303: return protocol_client_auth_sasl_step(vs, NULL, 0);
304: else
305: vnc_read_when(vs, protocol_client_auth_sasl_step, steplen);
306: return 0;
307: }
308:
309: /*
310: * Start Msg
311: *
312: * Input from client:
313: *
314: * u32 clientin-length
315: * u8-array clientin-string
316: *
317: * Output to client:
318: *
319: * u32 serverout-length
320: * u8-array serverout-strin
321: * u8 continue
322: */
323:
324: #define SASL_DATA_MAX_LEN (1024 * 1024)
325:
326: static int protocol_client_auth_sasl_start(VncState *vs, uint8_t *data, size_t len)
327: {
328: uint32_t datalen = len;
329: const char *serverout;
330: unsigned int serveroutlen;
331: int err;
332: char *clientdata = NULL;
333:
334: /* NB, distinction of NULL vs "" is *critical* in SASL */
335: if (datalen) {
336: clientdata = (char*)data;
337: clientdata[datalen-1] = '\0'; /* Should be on wire, but make sure */
338: datalen--; /* Don't count NULL byte when passing to _start() */
339: }
340:
341: VNC_DEBUG("Start SASL auth with mechanism %s. Data %p (%d bytes)\n",
342: vs->sasl.mechlist, clientdata, datalen);
343: err = sasl_server_start(vs->sasl.conn,
344: vs->sasl.mechlist,
345: clientdata,
346: datalen,
347: &serverout,
348: &serveroutlen);
349: if (err != SASL_OK &&
350: err != SASL_CONTINUE) {
351: VNC_DEBUG("sasl start failed %d (%s)\n",
352: err, sasl_errdetail(vs->sasl.conn));
353: sasl_dispose(&vs->sasl.conn);
354: vs->sasl.conn = NULL;
355: goto authabort;
356: }
357: if (serveroutlen > SASL_DATA_MAX_LEN) {
358: VNC_DEBUG("sasl start reply data too long %d\n",
359: serveroutlen);
360: sasl_dispose(&vs->sasl.conn);
361: vs->sasl.conn = NULL;
362: goto authabort;
363: }
364:
365: VNC_DEBUG("SASL return data %d bytes, nil; %d\n",
366: serveroutlen, serverout ? 0 : 1);
367:
368: if (serveroutlen) {
369: vnc_write_u32(vs, serveroutlen + 1);
370: vnc_write(vs, serverout, serveroutlen + 1);
371: } else {
372: vnc_write_u32(vs, 0);
373: }
374:
375: /* Whether auth is complete */
376: vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1);
377:
378: if (err == SASL_CONTINUE) {
379: VNC_DEBUG("%s", "Authentication must continue\n");
380: /* Wait for step length */
381: vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4);
382: } else {
383: if (!vnc_auth_sasl_check_ssf(vs)) {
384: VNC_DEBUG("Authentication rejected for weak SSF %d\n", vs->csock);
385: goto authreject;
386: }
387:
388: /* Check username whitelist ACL */
389: if (vnc_auth_sasl_check_access(vs) < 0) {
390: VNC_DEBUG("Authentication rejected for ACL %d\n", vs->csock);
391: goto authreject;
392: }
393:
394: VNC_DEBUG("Authentication successful %d\n", vs->csock);
395: vnc_write_u32(vs, 0); /* Accept auth */
396: start_client_init(vs);
397: }
398:
399: return 0;
400:
401: authreject:
402: vnc_write_u32(vs, 1); /* Reject auth */
403: vnc_write_u32(vs, sizeof("Authentication failed"));
404: vnc_write(vs, "Authentication failed", sizeof("Authentication failed"));
405: vnc_flush(vs);
406: vnc_client_error(vs);
407: return -1;
408:
409: authabort:
410: vnc_client_error(vs);
411: return -1;
412: }
413:
414: static int protocol_client_auth_sasl_start_len(VncState *vs, uint8_t *data, size_t len)
415: {
416: uint32_t startlen = read_u32(data, 0);
417: VNC_DEBUG("Got client start len %d\n", startlen);
418: if (startlen > SASL_DATA_MAX_LEN) {
419: VNC_DEBUG("Too much SASL data %d\n", startlen);
420: vnc_client_error(vs);
421: return -1;
422: }
423:
424: if (startlen == 0)
425: return protocol_client_auth_sasl_start(vs, NULL, 0);
426:
427: vnc_read_when(vs, protocol_client_auth_sasl_start, startlen);
428: return 0;
429: }
430:
431: static int protocol_client_auth_sasl_mechname(VncState *vs, uint8_t *data, size_t len)
432: {
433: char *mechname = malloc(len + 1);
434: if (!mechname) {
435: VNC_DEBUG("Out of memory reading mechname\n");
436: vnc_client_error(vs);
437: }
438: strncpy(mechname, (char*)data, len);
439: mechname[len] = '\0';
440: VNC_DEBUG("Got client mechname '%s' check against '%s'\n",
441: mechname, vs->sasl.mechlist);
442:
443: if (strncmp(vs->sasl.mechlist, mechname, len) == 0) {
444: if (vs->sasl.mechlist[len] != '\0' &&
445: vs->sasl.mechlist[len] != ',') {
446: VNC_DEBUG("One %d", vs->sasl.mechlist[len]);
447: vnc_client_error(vs);
448: return -1;
449: }
450: } else {
451: char *offset = strstr(vs->sasl.mechlist, mechname);
452: VNC_DEBUG("Two %p\n", offset);
453: if (!offset) {
454: vnc_client_error(vs);
455: return -1;
456: }
457: VNC_DEBUG("Two '%s'\n", offset);
458: if (offset[-1] != ',' ||
459: (offset[len] != '\0'&&
460: offset[len] != ',')) {
461: vnc_client_error(vs);
462: return -1;
463: }
464: }
465:
466: free(vs->sasl.mechlist);
467: vs->sasl.mechlist = mechname;
468:
469: VNC_DEBUG("Validated mechname '%s'\n", mechname);
470: vnc_read_when(vs, protocol_client_auth_sasl_start_len, 4);
471: return 0;
472: }
473:
474: static int protocol_client_auth_sasl_mechname_len(VncState *vs, uint8_t *data, size_t len)
475: {
476: uint32_t mechlen = read_u32(data, 0);
477: VNC_DEBUG("Got client mechname len %d\n", mechlen);
478: if (mechlen > 100) {
479: VNC_DEBUG("Too long SASL mechname data %d\n", mechlen);
480: vnc_client_error(vs);
481: return -1;
482: }
483: if (mechlen < 1) {
484: VNC_DEBUG("Too short SASL mechname %d\n", mechlen);
485: vnc_client_error(vs);
486: return -1;
487: }
488: vnc_read_when(vs, protocol_client_auth_sasl_mechname,mechlen);
489: return 0;
490: }
491:
492: #define USES_X509_AUTH(vs) \
493: ((vs)->subauth == VNC_AUTH_VENCRYPT_X509NONE || \
494: (vs)->subauth == VNC_AUTH_VENCRYPT_X509VNC || \
495: (vs)->subauth == VNC_AUTH_VENCRYPT_X509PLAIN || \
496: (vs)->subauth == VNC_AUTH_VENCRYPT_X509SASL)
497:
498:
499: void start_auth_sasl(VncState *vs)
500: {
501: const char *mechlist = NULL;
502: sasl_security_properties_t secprops;
503: int err;
504: char *localAddr, *remoteAddr;
505: int mechlistlen;
506:
507: VNC_DEBUG("Initialize SASL auth %d\n", vs->csock);
508:
509: /* Get local & remote client addresses in form IPADDR;PORT */
510: if (!(localAddr = vnc_socket_local_addr("%s;%s", vs->csock)))
511: goto authabort;
512:
513: if (!(remoteAddr = vnc_socket_remote_addr("%s;%s", vs->csock))) {
514: free(localAddr);
515: goto authabort;
516: }
517:
518: err = sasl_server_new("vnc",
519: NULL, /* FQDN - just delegates to gethostname */
520: NULL, /* User realm */
521: localAddr,
522: remoteAddr,
523: NULL, /* Callbacks, not needed */
524: SASL_SUCCESS_DATA,
525: &vs->sasl.conn);
526: free(localAddr);
527: free(remoteAddr);
528: localAddr = remoteAddr = NULL;
529:
530: if (err != SASL_OK) {
531: VNC_DEBUG("sasl context setup failed %d (%s)",
532: err, sasl_errstring(err, NULL, NULL));
533: vs->sasl.conn = NULL;
534: goto authabort;
535: }
536:
537: #ifdef CONFIG_VNC_TLS
538: /* Inform SASL that we've got an external SSF layer from TLS/x509 */
539: if (vs->vd->auth == VNC_AUTH_VENCRYPT &&
540: vs->vd->subauth == VNC_AUTH_VENCRYPT_X509SASL) {
541: gnutls_cipher_algorithm_t cipher;
542: sasl_ssf_t ssf;
543:
544: cipher = gnutls_cipher_get(vs->tls.session);
545: if (!(ssf = (sasl_ssf_t)gnutls_cipher_get_key_size(cipher))) {
546: VNC_DEBUG("%s", "cannot TLS get cipher size\n");
547: sasl_dispose(&vs->sasl.conn);
548: vs->sasl.conn = NULL;
549: goto authabort;
550: }
551: ssf *= 8; /* tls key size is bytes, sasl wants bits */
552:
553: err = sasl_setprop(vs->sasl.conn, SASL_SSF_EXTERNAL, &ssf);
554: if (err != SASL_OK) {
555: VNC_DEBUG("cannot set SASL external SSF %d (%s)\n",
556: err, sasl_errstring(err, NULL, NULL));
557: sasl_dispose(&vs->sasl.conn);
558: vs->sasl.conn = NULL;
559: goto authabort;
560: }
561: } else
562: #endif /* CONFIG_VNC_TLS */
563: vs->sasl.wantSSF = 1;
564:
565: memset (&secprops, 0, sizeof secprops);
566: /* Inform SASL that we've got an external SSF layer from TLS */
567: if (strncmp(vs->vd->display, "unix:", 5) == 0
568: #ifdef CONFIG_VNC_TLS
569: /* Disable SSF, if using TLS+x509+SASL only. TLS without x509
570: is not sufficiently strong */
571: || (vs->vd->auth == VNC_AUTH_VENCRYPT &&
572: vs->vd->subauth == VNC_AUTH_VENCRYPT_X509SASL)
573: #endif /* CONFIG_VNC_TLS */
574: ) {
575: /* If we've got TLS or UNIX domain sock, we don't care about SSF */
576: secprops.min_ssf = 0;
577: secprops.max_ssf = 0;
578: secprops.maxbufsize = 8192;
579: secprops.security_flags = 0;
580: } else {
581: /* Plain TCP, better get an SSF layer */
582: secprops.min_ssf = 56; /* Good enough to require kerberos */
583: secprops.max_ssf = 100000; /* Arbitrary big number */
584: secprops.maxbufsize = 8192;
585: /* Forbid any anonymous or trivially crackable auth */
586: secprops.security_flags =
587: SASL_SEC_NOANONYMOUS | SASL_SEC_NOPLAINTEXT;
588: }
589:
590: err = sasl_setprop(vs->sasl.conn, SASL_SEC_PROPS, &secprops);
591: if (err != SASL_OK) {
592: VNC_DEBUG("cannot set SASL security props %d (%s)\n",
593: err, sasl_errstring(err, NULL, NULL));
594: sasl_dispose(&vs->sasl.conn);
595: vs->sasl.conn = NULL;
596: goto authabort;
597: }
598:
599: err = sasl_listmech(vs->sasl.conn,
600: NULL, /* Don't need to set user */
601: "", /* Prefix */
602: ",", /* Separator */
603: "", /* Suffix */
604: &mechlist,
605: NULL,
606: NULL);
607: if (err != SASL_OK) {
608: VNC_DEBUG("cannot list SASL mechanisms %d (%s)\n",
609: err, sasl_errdetail(vs->sasl.conn));
610: sasl_dispose(&vs->sasl.conn);
611: vs->sasl.conn = NULL;
612: goto authabort;
613: }
614: VNC_DEBUG("Available mechanisms for client: '%s'\n", mechlist);
615:
616: if (!(vs->sasl.mechlist = strdup(mechlist))) {
617: VNC_DEBUG("Out of memory");
618: sasl_dispose(&vs->sasl.conn);
619: vs->sasl.conn = NULL;
620: goto authabort;
621: }
622: mechlistlen = strlen(mechlist);
623: vnc_write_u32(vs, mechlistlen);
624: vnc_write(vs, mechlist, mechlistlen);
625: vnc_flush(vs);
626:
627: VNC_DEBUG("Wait for client mechname length\n");
628: vnc_read_when(vs, protocol_client_auth_sasl_mechname_len, 4);
629:
630: return;
631:
632: authabort:
633: vnc_client_error(vs);
634: return;
635: }
636:
637:
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