source: branches/samba-3.5.x/client/cifs.upcall.c

Last change on this file was 414, checked in by Herwig Bauernfeind, 15 years ago

Samba 3.5.0: Initial import
File size: 16.1 KB
Line 
1/*
2* CIFS user-space helper.
3* Copyright (C) Igor Mammedov (niallain@gmail.com) 2007
4* Copyright (C) Jeff Layton (jlayton@redhat.com) 2009
5*
6* Used by /sbin/request-key for handling
7* cifs upcall for kerberos authorization of access to share and
8* cifs upcall for DFS srver name resolving (IPv4/IPv6 aware).
9* You should have keyutils installed and add something like the
10* following lines to /etc/request-key.conf file:
11
12create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
13create dns_resolver * * /usr/local/sbin/cifs.upcall %k
14
15* This program is free software; you can redistribute it and/or modify
16* it under the terms of the GNU General Public License as published by
17* the Free Software Foundation; either version 2 of the License, or
18* (at your option) any later version.
19* This program is distributed in the hope that it will be useful,
20* but WITHOUT ANY WARRANTY; without even the implied warranty of
21* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22* GNU General Public License for more details.
23* You should have received a copy of the GNU General Public License
24* along with this program; if not, write to the Free Software
25* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
26*/
27
28#include "includes.h"
29#include "../libcli/auth/spnego.h"
30#include "smb_krb5.h"
31#include <keyutils.h>
32#include <getopt.h>
33
34#include "cifs_spnego.h"
35
36#define CIFS_DEFAULT_KRB5_DIR "/tmp"
37#define CIFS_DEFAULT_KRB5_PREFIX "krb5cc_"
38
39#define MAX_CCNAME_LEN PATH_MAX + 5
40
41const char *CIFSSPNEGO_VERSION = "1.3";
42static const char *prog = "cifs.upcall";
43typedef enum _sectype {
44 NONE = 0,
45 KRB5,
46 MS_KRB5
47} sectype_t;
48
49/* does the ccache have a valid TGT? */
50static time_t
51get_tgt_time(const char *ccname) {
52 krb5_context context;
53 krb5_ccache ccache;
54 krb5_cc_cursor cur;
55 krb5_creds creds;
56 krb5_principal principal;
57 time_t credtime = 0;
58 char *realm = NULL;
59 TALLOC_CTX *mem_ctx;
60
61 if (krb5_init_context(&context)) {
62 syslog(LOG_DEBUG, "%s: unable to init krb5 context", __func__);
63 return 0;
64 }
65
66 if (krb5_cc_resolve(context, ccname, &ccache)) {
67 syslog(LOG_DEBUG, "%s: unable to resolve krb5 cache", __func__);
68 goto err_cache;
69 }
70
71 if (krb5_cc_set_flags(context, ccache, 0)) {
72 syslog(LOG_DEBUG, "%s: unable to set flags", __func__);
73 goto err_cache;
74 }
75
76 if (krb5_cc_get_principal(context, ccache, &principal)) {
77 syslog(LOG_DEBUG, "%s: unable to get principal", __func__);
78 goto err_princ;
79 }
80
81 if (krb5_cc_start_seq_get(context, ccache, &cur)) {
82 syslog(LOG_DEBUG, "%s: unable to seq start", __func__);
83 goto err_ccstart;
84 }
85
86 if ((realm = smb_krb5_principal_get_realm(context, principal)) == NULL) {
87 syslog(LOG_DEBUG, "%s: unable to get realm", __func__);
88 goto err_ccstart;
89 }
90
91 mem_ctx = talloc_init("cifs.upcall");
92 while (!credtime && !krb5_cc_next_cred(context, ccache, &cur, &creds)) {
93 char *name;
94 if (smb_krb5_unparse_name(mem_ctx, context, creds.server, &name)) {
95 syslog(LOG_DEBUG, "%s: unable to unparse name", __func__);
96 goto err_endseq;
97 }
98 if (krb5_realm_compare(context, creds.server, principal) &&
99 strnequal(name, KRB5_TGS_NAME, KRB5_TGS_NAME_SIZE) &&
100 strnequal(name+KRB5_TGS_NAME_SIZE+1, realm, strlen(realm)) &&
101 creds.times.endtime > time(NULL))
102 credtime = creds.times.endtime;
103 krb5_free_cred_contents(context, &creds);
104 TALLOC_FREE(name);
105 }
106err_endseq:
107 TALLOC_FREE(mem_ctx);
108 krb5_cc_end_seq_get(context, ccache, &cur);
109err_ccstart:
110 krb5_free_principal(context, principal);
111err_princ:
112#if defined(KRB5_TC_OPENCLOSE)
113 krb5_cc_set_flags(context, ccache, KRB5_TC_OPENCLOSE);
114#endif
115 krb5_cc_close(context, ccache);
116err_cache:
117 krb5_free_context(context);
118 return credtime;
119}
120
121static int
122krb5cc_filter(const struct dirent *dirent)
123{
124 if (strstr(dirent->d_name, CIFS_DEFAULT_KRB5_PREFIX))
125 return 1;
126 else
127 return 0;
128}
129
130/* search for a credcache that looks like a likely candidate */
131static char *
132find_krb5_cc(const char *dirname, uid_t uid)
133{
134 struct dirent **namelist;
135 struct stat sbuf;
136 char ccname[MAX_CCNAME_LEN], *credpath, *best_cache = NULL;
137 int i, n;
138 time_t cred_time, best_time = 0;
139
140 n = scandir(dirname, &namelist, krb5cc_filter, NULL);
141 if (n < 0) {
142 syslog(LOG_DEBUG, "%s: scandir error on directory '%s': %s",
143 __func__, dirname, strerror(errno));
144 return NULL;
145 }
146
147 for (i = 0; i < n; i++) {
148 snprintf(ccname, sizeof(ccname), "FILE:%s/%s", dirname,
149 namelist[i]->d_name);
150 credpath = ccname + 5;
151 syslog(LOG_DEBUG, "%s: considering %s", __func__, credpath);
152
153 if (lstat(credpath, &sbuf)) {
154 syslog(LOG_DEBUG, "%s: stat error on '%s': %s",
155 __func__, credpath, strerror(errno));
156 free(namelist[i]);
157 continue;
158 }
159 if (sbuf.st_uid != uid) {
160 syslog(LOG_DEBUG, "%s: %s is owned by %u, not %u",
161 __func__, credpath, sbuf.st_uid, uid);
162 free(namelist[i]);
163 continue;
164 }
165 if (!S_ISREG(sbuf.st_mode)) {
166 syslog(LOG_DEBUG, "%s: %s is not a regular file",
167 __func__, credpath);
168 free(namelist[i]);
169 continue;
170 }
171 if (!(cred_time = get_tgt_time(ccname))) {
172 syslog(LOG_DEBUG, "%s: %s is not a valid credcache.",
173 __func__, ccname);
174 free(namelist[i]);
175 continue;
176 }
177
178 if (cred_time <= best_time) {
179 syslog(LOG_DEBUG, "%s: %s expires sooner than current "
180 "best.", __func__, ccname);
181 free(namelist[i]);
182 continue;
183 }
184
185 syslog(LOG_DEBUG, "%s: %s is valid ccache", __func__, ccname);
186 free(best_cache);
187 best_cache = SMB_STRNDUP(ccname, MAX_CCNAME_LEN);
188 best_time = cred_time;
189 free(namelist[i]);
190 }
191 free(namelist);
192
193 return best_cache;
194}
195
196/*
197 * Prepares AP-REQ data for mechToken and gets session key
198 * Uses credentials from cache. It will not ask for password
199 * you should receive credentials for yuor name manually using
200 * kinit or whatever you wish.
201 *
202 * in:
203 * oid - string with OID/ Could be OID_KERBEROS5
204 * or OID_KERBEROS5_OLD
205 * principal - Service name.
206 * Could be "cifs/FQDN" for KRB5 OID
207 * or for MS_KRB5 OID style server principal
208 * like "pdc$@YOUR.REALM.NAME"
209 *
210 * out:
211 * secblob - pointer for spnego wrapped AP-REQ data to be stored
212 * sess_key- pointer for SessionKey data to be stored
213 *
214 * ret: 0 - success, others - failure
215 */
216static int
217handle_krb5_mech(const char *oid, const char *principal, DATA_BLOB *secblob,
218 DATA_BLOB *sess_key, const char *ccname)
219{
220 int retval;
221 DATA_BLOB tkt, tkt_wrapped;
222
223 syslog(LOG_DEBUG, "%s: getting service ticket for %s", __func__,
224 principal);
225
226 /* get a kerberos ticket for the service and extract the session key */
227 retval = cli_krb5_get_ticket(principal, 0, &tkt, sess_key, 0, ccname,
228 NULL, NULL);
229
230 if (retval) {
231 syslog(LOG_DEBUG, "%s: failed to obtain service ticket (%d)",
232 __func__, retval);
233 return retval;
234 }
235
236 syslog(LOG_DEBUG, "%s: obtained service ticket", __func__);
237
238 /* wrap that up in a nice GSS-API wrapping */
239 tkt_wrapped = spnego_gen_krb5_wrap(tkt, TOK_ID_KRB_AP_REQ);
240
241 /* and wrap that in a shiny SPNEGO wrapper */
242 *secblob = gen_negTokenInit(oid, tkt_wrapped);
243
244 data_blob_free(&tkt_wrapped);
245 data_blob_free(&tkt);
246 return retval;
247}
248
249#define DKD_HAVE_HOSTNAME 0x1
250#define DKD_HAVE_VERSION 0x2
251#define DKD_HAVE_SEC 0x4
252#define DKD_HAVE_IP 0x8
253#define DKD_HAVE_UID 0x10
254#define DKD_HAVE_PID 0x20
255#define DKD_MUSTHAVE_SET (DKD_HAVE_HOSTNAME|DKD_HAVE_VERSION|DKD_HAVE_SEC)
256
257struct decoded_args {
258 int ver;
259 char *hostname;
260 char *ip;
261 uid_t uid;
262 pid_t pid;
263 sectype_t sec;
264};
265
266static unsigned int
267decode_key_description(const char *desc, struct decoded_args *arg)
268{
269 int len;
270 int retval = 0;
271 char *pos;
272 const char *tkn = desc;
273
274 do {
275 pos = index(tkn, ';');
276 if (strncmp(tkn, "host=", 5) == 0) {
277
278 if (pos == NULL)
279 len = strlen(tkn);
280 else
281 len = pos - tkn;
282
283 len -= 4;
284 SAFE_FREE(arg->hostname);
285 arg->hostname = SMB_XMALLOC_ARRAY(char, len);
286 strlcpy(arg->hostname, tkn + 5, len);
287 retval |= DKD_HAVE_HOSTNAME;
288 } else if (!strncmp(tkn, "ip4=", 4) ||
289 !strncmp(tkn, "ip6=", 4)) {
290 if (pos == NULL)
291 len = strlen(tkn);
292 else
293 len = pos - tkn;
294
295 len -= 3;
296 SAFE_FREE(arg->ip);
297 arg->ip = SMB_XMALLOC_ARRAY(char, len);
298 strlcpy(arg->ip, tkn + 4, len);
299 retval |= DKD_HAVE_IP;
300 } else if (strncmp(tkn, "pid=", 4) == 0) {
301 errno = 0;
302 arg->pid = strtol(tkn + 4, NULL, 0);
303 if (errno != 0) {
304 syslog(LOG_ERR, "Invalid pid format: %s",
305 strerror(errno));
306 return 1;
307 } else {
308 retval |= DKD_HAVE_PID;
309 }
310 } else if (strncmp(tkn, "sec=", 4) == 0) {
311 if (strncmp(tkn + 4, "krb5", 4) == 0) {
312 retval |= DKD_HAVE_SEC;
313 arg->sec = KRB5;
314 } else if (strncmp(tkn + 4, "mskrb5", 6) == 0) {
315 retval |= DKD_HAVE_SEC;
316 arg->sec = MS_KRB5;
317 }
318 } else if (strncmp(tkn, "uid=", 4) == 0) {
319 errno = 0;
320 arg->uid = strtol(tkn + 4, NULL, 16);
321 if (errno != 0) {
322 syslog(LOG_ERR, "Invalid uid format: %s",
323 strerror(errno));
324 return 1;
325 } else {
326 retval |= DKD_HAVE_UID;
327 }
328 } else if (strncmp(tkn, "ver=", 4) == 0) { /* if version */
329 errno = 0;
330 arg->ver = strtol(tkn + 4, NULL, 16);
331 if (errno != 0) {
332 syslog(LOG_ERR, "Invalid version format: %s",
333 strerror(errno));
334 return 1;
335 } else {
336 retval |= DKD_HAVE_VERSION;
337 }
338 }
339 if (pos == NULL)
340 break;
341 tkn = pos + 1;
342 } while (tkn);
343 return retval;
344}
345
346static int
347cifs_resolver(const key_serial_t key, const char *key_descr)
348{
349 int c;
350 struct addrinfo *addr;
351 char ip[INET6_ADDRSTRLEN];
352 void *p;
353 const char *keyend = key_descr;
354 /* skip next 4 ';' delimiters to get to description */
355 for (c = 1; c <= 4; c++) {
356 keyend = index(keyend+1, ';');
357 if (!keyend) {
358 syslog(LOG_ERR, "invalid key description: %s",
359 key_descr);
360 return 1;
361 }
362 }
363 keyend++;
364
365 /* resolve name to ip */
366 c = getaddrinfo(keyend, NULL, NULL, &addr);
367 if (c) {
368 syslog(LOG_ERR, "unable to resolve hostname: %s [%s]",
369 keyend, gai_strerror(c));
370 return 1;
371 }
372
373 /* conver ip to string form */
374 if (addr->ai_family == AF_INET)
375 p = &(((struct sockaddr_in *)addr->ai_addr)->sin_addr);
376 else
377 p = &(((struct sockaddr_in6 *)addr->ai_addr)->sin6_addr);
378
379 if (!inet_ntop(addr->ai_family, p, ip, sizeof(ip))) {
380 syslog(LOG_ERR, "%s: inet_ntop: %s", __func__, strerror(errno));
381 freeaddrinfo(addr);
382 return 1;
383 }
384
385 /* setup key */
386 c = keyctl_instantiate(key, ip, strlen(ip)+1, 0);
387 if (c == -1) {
388 syslog(LOG_ERR, "%s: keyctl_instantiate: %s", __func__,
389 strerror(errno));
390 freeaddrinfo(addr);
391 return 1;
392 }
393
394 freeaddrinfo(addr);
395 return 0;
396}
397
398/*
399 * Older kernels sent IPv6 addresses without colons. Well, at least
400 * they're fixed-length strings. Convert these addresses to have colon
401 * delimiters to make getaddrinfo happy.
402 */
403static void
404convert_inet6_addr(const char *from, char *to)
405{
406 int i = 1;
407
408 while (*from) {
409 *to++ = *from++;
410 if (!(i++ % 4) && *from)
411 *to++ = ':';
412 }
413 *to = 0;
414}
415
416static int
417ip_to_fqdn(const char *addrstr, char *host, size_t hostlen)
418{
419 int rc;
420 struct addrinfo hints = { .ai_flags = AI_NUMERICHOST };
421 struct addrinfo *res;
422 const char *ipaddr = addrstr;
423 char converted[INET6_ADDRSTRLEN + 1];
424
425 if ((strlen(ipaddr) > INET_ADDRSTRLEN) && !strchr(ipaddr, ':')) {
426 convert_inet6_addr(ipaddr, converted);
427 ipaddr = converted;
428 }
429
430 rc = getaddrinfo(ipaddr, NULL, &hints, &res);
431 if (rc) {
432 syslog(LOG_DEBUG, "%s: failed to resolve %s to "
433 "ipaddr: %s", __func__, ipaddr,
434 rc == EAI_SYSTEM ? strerror(errno) : gai_strerror(rc));
435 return rc;
436 }
437
438 rc = getnameinfo(res->ai_addr, res->ai_addrlen, host, hostlen,
439 NULL, 0, NI_NAMEREQD);
440 freeaddrinfo(res);
441 if (rc) {
442 syslog(LOG_DEBUG, "%s: failed to resolve %s to fqdn: %s",
443 __func__, ipaddr,
444 rc == EAI_SYSTEM ? strerror(errno) : gai_strerror(rc));
445 return rc;
446 }
447
448 syslog(LOG_DEBUG, "%s: resolved %s to %s", __func__, ipaddr, host);
449 return 0;
450}
451
452static void
453usage(void)
454{
455 syslog(LOG_INFO, "Usage: %s [-t] [-v] key_serial", prog);
456 fprintf(stderr, "Usage: %s [-t] [-v] key_serial\n", prog);
457}
458
459const struct option long_options[] = {
460 { "trust-dns", 0, NULL, 't' },
461 { "version", 0, NULL, 'v' },
462 { NULL, 0, NULL, 0 }
463};
464
465int main(const int argc, char *const argv[])
466{
467 struct cifs_spnego_msg *keydata = NULL;
468 DATA_BLOB secblob = data_blob_null;
469 DATA_BLOB sess_key = data_blob_null;
470 key_serial_t key = 0;
471 size_t datalen;
472 unsigned int have;
473 long rc = 1;
474 int c, try_dns = 0;
475 char *buf, *princ = NULL, *ccname = NULL;
476 char hostbuf[NI_MAXHOST], *host;
477 struct decoded_args arg = { };
478 const char *oid;
479
480 hostbuf[0] = '\0';
481
482 openlog(prog, 0, LOG_DAEMON);
483
484 while ((c = getopt_long(argc, argv, "ctv", long_options, NULL)) != -1) {
485 switch (c) {
486 case 'c':
487 /* legacy option -- skip it */
488 break;
489 case 't':
490 try_dns++;
491 break;
492 case 'v':
493 printf("version: %s\n", CIFSSPNEGO_VERSION);
494 goto out;
495 default:
496 syslog(LOG_ERR, "unknown option: %c", c);
497 goto out;
498 }
499 }
500
501 /* is there a key? */
502 if (argc <= optind) {
503 usage();
504 goto out;
505 }
506
507 /* get key and keyring values */
508 errno = 0;
509 key = strtol(argv[optind], NULL, 10);
510 if (errno != 0) {
511 key = 0;
512 syslog(LOG_ERR, "Invalid key format: %s", strerror(errno));
513 goto out;
514 }
515
516 rc = keyctl_describe_alloc(key, &buf);
517 if (rc == -1) {
518 syslog(LOG_ERR, "keyctl_describe_alloc failed: %s",
519 strerror(errno));
520 rc = 1;
521 goto out;
522 }
523
524 syslog(LOG_DEBUG, "key description: %s", buf);
525
526 if ((strncmp(buf, "cifs.resolver", sizeof("cifs.resolver")-1) == 0) ||
527 (strncmp(buf, "dns_resolver", sizeof("dns_resolver")-1) == 0)) {
528 rc = cifs_resolver(key, buf);
529 goto out;
530 }
531
532 have = decode_key_description(buf, &arg);
533 SAFE_FREE(buf);
534 if ((have & DKD_MUSTHAVE_SET) != DKD_MUSTHAVE_SET) {
535 syslog(LOG_ERR, "unable to get necessary params from key "
536 "description (0x%x)", have);
537 rc = 1;
538 goto out;
539 }
540
541 if (arg.ver > CIFS_SPNEGO_UPCALL_VERSION) {
542 syslog(LOG_ERR, "incompatible kernel upcall version: 0x%x",
543 arg.ver);
544 rc = 1;
545 goto out;
546 }
547
548 if (have & DKD_HAVE_UID) {
549 rc = setuid(arg.uid);
550 if (rc == -1) {
551 syslog(LOG_ERR, "setuid: %s", strerror(errno));
552 goto out;
553 }
554
555 ccname = find_krb5_cc(CIFS_DEFAULT_KRB5_DIR, arg.uid);
556 }
557
558 host = arg.hostname;
559
560 // do mech specific authorization
561 switch (arg.sec) {
562 case MS_KRB5:
563 case KRB5:
564retry_new_hostname:
565 /* for "cifs/" service name + terminating 0 */
566 datalen = strlen(host) + 5 + 1;
567 princ = SMB_XMALLOC_ARRAY(char, datalen);
568 if (!princ) {
569 rc = -ENOMEM;
570 break;
571 }
572
573 if (arg.sec == MS_KRB5)
574 oid = OID_KERBEROS5_OLD;
575 else
576 oid = OID_KERBEROS5;
577
578 /*
579 * try getting a cifs/ principal first and then fall back to
580 * getting a host/ principal if that doesn't work.
581 */
582 strlcpy(princ, "cifs/", datalen);
583 strlcpy(princ + 5, host, datalen - 5);
584 rc = handle_krb5_mech(oid, princ, &secblob, &sess_key, ccname);
585 if (!rc)
586 break;
587
588 memcpy(princ, "host/", 5);
589 rc = handle_krb5_mech(oid, princ, &secblob, &sess_key, ccname);
590 if (!rc)
591 break;
592
593 if (!try_dns || !(have & DKD_HAVE_IP))
594 break;
595
596 rc = ip_to_fqdn(arg.ip, hostbuf, sizeof(hostbuf));
597 if (rc)
598 break;
599
600 SAFE_FREE(princ);
601 try_dns = 0;
602 host = hostbuf;
603 goto retry_new_hostname;
604 default:
605 syslog(LOG_ERR, "sectype: %d is not implemented", arg.sec);
606 rc = 1;
607 break;
608 }
609
610 SAFE_FREE(princ);
611
612 if (rc)
613 goto out;
614
615 /* pack SecurityBLob and SessionKey into downcall packet */
616 datalen =
617 sizeof(struct cifs_spnego_msg) + secblob.length + sess_key.length;
618 keydata = (struct cifs_spnego_msg*)SMB_XMALLOC_ARRAY(char, datalen);
619 if (!keydata) {
620 rc = 1;
621 goto out;
622 }
623 keydata->version = arg.ver;
624 keydata->flags = 0;
625 keydata->sesskey_len = sess_key.length;
626 keydata->secblob_len = secblob.length;
627 memcpy(&(keydata->data), sess_key.data, sess_key.length);
628 memcpy(&(keydata->data) + keydata->sesskey_len,
629 secblob.data, secblob.length);
630
631 /* setup key */
632 rc = keyctl_instantiate(key, keydata, datalen, 0);
633 if (rc == -1) {
634 syslog(LOG_ERR, "keyctl_instantiate: %s", strerror(errno));
635 goto out;
636 }
637
638 /* BB: maybe we need use timeout for key: for example no more then
639 * ticket lifietime? */
640 /* keyctl_set_timeout( key, 60); */
641out:
642 /*
643 * on error, negatively instantiate the key ourselves so that we can
644 * make sure the kernel doesn't hang it off of a searchable keyring
645 * and interfere with the next attempt to instantiate the key.
646 */
647 if (rc != 0 && key == 0)
648 keyctl_negate(key, 1, KEY_REQKEY_DEFL_DEFAULT);
649 data_blob_free(&secblob);
650 data_blob_free(&sess_key);
651 SAFE_FREE(ccname);
652 SAFE_FREE(arg.hostname);
653 SAFE_FREE(arg.ip);
654 SAFE_FREE(keydata);
655 return rc;
656}
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