summaryrefslogtreecommitdiff
path: root/source3/smbd/sec_ctx.c
blob: 8da1db41f43d09f8333e437907b990521522073d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
/* 
   Unix SMB/CIFS implementation.
   uid/user handling
   Copyright (C) Tim Potter 2000

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "smbd/smbd.h"
#include "smbd/globals.h"
#include "libcli/security/security_token.h"
#include "auth.h"

extern struct current_user current_user;

/****************************************************************************
 Are two UNIX tokens equal ?
****************************************************************************/

bool unix_token_equal(const struct security_unix_token *t1, const struct security_unix_token *t2)
{
	if (t1->uid != t2->uid || t1->gid != t2->gid ||
			t1->ngroups != t2->ngroups) {
		return false;
	}
	if (memcmp(t1->groups, t2->groups,
			t1->ngroups*sizeof(gid_t)) != 0) {
		return false;
	}
	return true;
}

/****************************************************************************
 Become the specified uid.
****************************************************************************/

static bool become_uid(uid_t uid)
{
	/* Check for dodgy uid values */

	if (uid == (uid_t)-1 || 
	    ((sizeof(uid_t) == 2) && (uid == (uid_t)65535))) {
		if (!become_uid_done) {
			DEBUG(1,("WARNING: using uid %d is a security risk\n",
				 (int)uid));
			become_uid_done = true;
		}
	}

	/* Set effective user id */

	set_effective_uid(uid);

	DO_PROFILE_INC(uid_changes);
	return True;
}

/****************************************************************************
 Become the specified gid.
****************************************************************************/

static bool become_gid(gid_t gid)
{
	/* Check for dodgy gid values */

	if (gid == (gid_t)-1 || ((sizeof(gid_t) == 2) && 
				 (gid == (gid_t)65535))) {
		if (!become_gid_done) {
			DEBUG(1,("WARNING: using gid %d is a security risk\n",
				 (int)gid));  
			become_gid_done = true;
		}
	}

	/* Set effective group id */

	set_effective_gid(gid);
	return True;
}

/****************************************************************************
 Become the specified uid and gid.
****************************************************************************/

static bool become_id(uid_t uid, gid_t gid)
{
	return become_gid(gid) && become_uid(uid);
}

/****************************************************************************
 Drop back to root privileges in order to change to another user.
****************************************************************************/

static void gain_root(void)
{
	if (non_root_mode()) {
		return;
	}

	if (geteuid() != 0) {
		set_effective_uid(0);

		if (geteuid() != 0) {
			DEBUG(0,
			      ("Warning: You appear to have a trapdoor "
			       "uid system\n"));
		}
	}

	if (getegid() != 0) {
		set_effective_gid(0);

		if (getegid() != 0) {
			DEBUG(0,
			      ("Warning: You appear to have a trapdoor "
			       "gid system\n"));
		}
	}
}

/****************************************************************************
 Get the list of current groups.
****************************************************************************/

static int get_current_groups(gid_t gid, uint32_t *p_ngroups, gid_t **p_groups)
{
	int i;
	gid_t grp;
	int ngroups;
	gid_t *groups = NULL;

	(*p_ngroups) = 0;
	(*p_groups) = NULL;

	/* this looks a little strange, but is needed to cope with
	   systems that put the current egid in the group list
	   returned from getgroups() (tridge) */
	save_re_gid();
	set_effective_gid(gid);
	setgid(gid);

	ngroups = sys_getgroups(0,&grp);
	if (ngroups <= 0) {
		goto fail;
	}

	if((groups = SMB_MALLOC_ARRAY(gid_t, ngroups+1)) == NULL) {
		DEBUG(0,("setup_groups malloc fail !\n"));
		goto fail;
	}

	if ((ngroups = sys_getgroups(ngroups,groups)) == -1) {
		goto fail;
	}

	restore_re_gid();

	(*p_ngroups) = ngroups;
	(*p_groups) = groups;

	DEBUG( 4, ( "get_current_groups: user is in %u groups: ", ngroups));
	for (i = 0; i < ngroups; i++ ) {
		DEBUG( 4, ( "%s%d", (i ? ", " : ""), (int)groups[i] ) );
	}
	DEBUG( 4, ( "\n" ) );

	return ngroups;

fail:
	SAFE_FREE(groups);
	restore_re_gid();
	return -1;
}

/****************************************************************************
 Create a new security context on the stack.  It is the same as the old
 one.  User changes are done using the set_sec_ctx() function.
****************************************************************************/

bool push_sec_ctx(void)
{
	struct sec_ctx *ctx_p;

	/* Check we don't overflow our stack */

	if (sec_ctx_stack_ndx == MAX_SEC_CTX_DEPTH) {
		DEBUG(0, ("Security context stack overflow!\n"));
		smb_panic("Security context stack overflow!");
	}

	/* Store previous user context */

	sec_ctx_stack_ndx++;

	ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];

	ctx_p->ut.uid = geteuid();
	ctx_p->ut.gid = getegid();

 	DEBUG(4, ("push_sec_ctx(%u, %u) : sec_ctx_stack_ndx = %d\n", 
 		  (unsigned int)ctx_p->ut.uid, (unsigned int)ctx_p->ut.gid, sec_ctx_stack_ndx ));

	ctx_p->token = dup_nt_token(NULL,
				    sec_ctx_stack[sec_ctx_stack_ndx-1].token);

	ctx_p->ut.ngroups = sys_getgroups(0, NULL);

	if (ctx_p->ut.ngroups != 0) {
		if (!(ctx_p->ut.groups = SMB_MALLOC_ARRAY(gid_t, ctx_p->ut.ngroups))) {
			DEBUG(0, ("Out of memory in push_sec_ctx()\n"));
			TALLOC_FREE(ctx_p->token);
			return False;
		}

		sys_getgroups(ctx_p->ut.ngroups, ctx_p->ut.groups);
	} else {
		ctx_p->ut.groups = NULL;
	}

	return True;
}

/****************************************************************************
 Change UNIX security context. Calls panic if not successful so no return value.
****************************************************************************/

#ifndef HAVE_DARWIN_INITGROUPS

/* Normal credential switch path. */

static void set_unix_security_ctx(uid_t uid, gid_t gid, int ngroups, gid_t *groups)
{
	/* Start context switch */
	gain_root();
#ifdef HAVE_SETGROUPS
	if (sys_setgroups(gid, ngroups, groups) != 0 && !non_root_mode()) {
		smb_panic("sys_setgroups failed");
	}
#endif
	become_id(uid, gid);
	/* end context switch */
}

#else /* HAVE_DARWIN_INITGROUPS */

/* The Darwin groups implementation is a little unusual. The list of
* groups in the kernel credential is not exhaustive, but more like
* a cache. The full group list is held in userspace and checked
* dynamically.
*
* This is an optional mechanism, and setgroups(2) opts out
* of it. That is, if you call setgroups, then the list of groups you
* set are the only groups that are ever checked. This is not what we
* want. We want to opt in to the dynamic resolution mechanism, so we
* need to specify the uid of the user whose group list (cache) we are
* setting.
*
* The Darwin rules are:
*  1. Thou shalt setegid, initgroups and seteuid IN THAT ORDER
*  2. Thou shalt not pass more that NGROUPS_MAX to initgroups
*  3. Thou shalt leave the first entry in the groups list well alone
*/

#include <sys/syscall.h>

static void set_unix_security_ctx(uid_t uid, gid_t gid, int ngroups, gid_t *groups)
{
	int max = groups_max();

	/* Start context switch */
	gain_root();

	become_gid(gid);


	if (syscall(SYS_initgroups, (ngroups > max) ? max : ngroups,
			groups, uid) == -1 && !non_root_mode()) {
		DEBUG(0, ("WARNING: failed to set group list "
			"(%d groups) for UID %ld: %s\n",
			ngroups, uid, strerror(errno)));
		smb_panic("sys_setgroups failed");
	}

	become_uid(uid);
	/* end context switch */
}

#endif /* HAVE_DARWIN_INITGROUPS */

/****************************************************************************
 Set the current security context to a given user.
****************************************************************************/

void set_sec_ctx(uid_t uid, gid_t gid, int ngroups, gid_t *groups, struct security_token *token)
{
	struct sec_ctx *ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];

	/* Set the security context */

	DEBUG(4, ("setting sec ctx (%u, %u) - sec_ctx_stack_ndx = %d\n", 
		(unsigned int)uid, (unsigned int)gid, sec_ctx_stack_ndx));

	security_token_debug(DBGC_CLASS, 5, token);
	debug_unix_user_token(DBGC_CLASS, 5, uid, gid, ngroups, groups);

	/* Change uid, gid and supplementary group list. */
	set_unix_security_ctx(uid, gid, ngroups, groups);

	ctx_p->ut.ngroups = ngroups;

	SAFE_FREE(ctx_p->ut.groups);
	if (token && (token == ctx_p->token)) {
		smb_panic("DUPLICATE_TOKEN");
	}

	TALLOC_FREE(ctx_p->token);

	if (ngroups) {
		ctx_p->ut.groups = (gid_t *)memdup(groups,
						   sizeof(gid_t) * ngroups);
		if (!ctx_p->ut.groups) {
			smb_panic("memdup failed");
		}
	} else {
		ctx_p->ut.groups = NULL;
	}

	if (token) {
		ctx_p->token = dup_nt_token(NULL, token);
		if (!ctx_p->token) {
			smb_panic("dup_nt_token failed");
		}
	} else {
		ctx_p->token = NULL;
	}

	ctx_p->ut.uid = uid;
	ctx_p->ut.gid = gid;

	/* Update current_user stuff */

	current_user.ut.uid = uid;
	current_user.ut.gid = gid;
	current_user.ut.ngroups = ngroups;
	current_user.ut.groups = groups;
	current_user.nt_user_token = ctx_p->token;
}

/****************************************************************************
 Become root context.
****************************************************************************/

void set_root_sec_ctx(void)
{
	/* May need to worry about supplementary groups at some stage */

	set_sec_ctx(0, 0, 0, NULL, NULL);
}

/****************************************************************************
 Pop a security context from the stack.
****************************************************************************/

bool pop_sec_ctx(void)
{
	struct sec_ctx *ctx_p;
	struct sec_ctx *prev_ctx_p;

	/* Check for stack underflow */

	if (sec_ctx_stack_ndx == 0) {
		DEBUG(0, ("Security context stack underflow!\n"));
		smb_panic("Security context stack underflow!");
	}

	ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];

	/* Clear previous user info */

	ctx_p->ut.uid = (uid_t)-1;
	ctx_p->ut.gid = (gid_t)-1;

	SAFE_FREE(ctx_p->ut.groups);
	ctx_p->ut.ngroups = 0;

	TALLOC_FREE(ctx_p->token);

	/* Pop back previous user */

	sec_ctx_stack_ndx--;

	prev_ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];

	/* Change uid, gid and supplementary group list. */
	set_unix_security_ctx(prev_ctx_p->ut.uid,
			prev_ctx_p->ut.gid,
			prev_ctx_p->ut.ngroups,
			prev_ctx_p->ut.groups);

	/* Update current_user stuff */

	current_user.ut.uid = prev_ctx_p->ut.uid;
	current_user.ut.gid = prev_ctx_p->ut.gid;
	current_user.ut.ngroups = prev_ctx_p->ut.ngroups;
	current_user.ut.groups = prev_ctx_p->ut.groups;
	current_user.nt_user_token = prev_ctx_p->token;

	DEBUG(4, ("pop_sec_ctx (%u, %u) - sec_ctx_stack_ndx = %d\n", 
		(unsigned int)geteuid(), (unsigned int)getegid(), sec_ctx_stack_ndx));

	return True;
}

/* Initialise the security context system */

void init_sec_ctx(void)
{
	int i;
	struct sec_ctx *ctx_p;

	/* Initialise security context stack */

	memset(sec_ctx_stack, 0, sizeof(struct sec_ctx) * MAX_SEC_CTX_DEPTH);

	for (i = 0; i < MAX_SEC_CTX_DEPTH; i++) {
		sec_ctx_stack[i].ut.uid = (uid_t)-1;
		sec_ctx_stack[i].ut.gid = (gid_t)-1;
	}

	/* Initialise first level of stack.  It is the current context */
	ctx_p = &sec_ctx_stack[0];

	ctx_p->ut.uid = geteuid();
	ctx_p->ut.gid = getegid();

	get_current_groups(ctx_p->ut.gid, &ctx_p->ut.ngroups, &ctx_p->ut.groups);

	ctx_p->token = NULL; /* Maps to guest user. */

	/* Initialise current_user global */

	current_user.ut.uid = ctx_p->ut.uid;
	current_user.ut.gid = ctx_p->ut.gid;
	current_user.ut.ngroups = ctx_p->ut.ngroups;
	current_user.ut.groups = ctx_p->ut.groups;

	/* The conn and vuid are usually taken care of by other modules.
	   We initialise them here. */

	current_user.conn = NULL;
	current_user.vuid = UID_FIELD_INVALID;
	current_user.nt_user_token = NULL;
}