summaryrefslogtreecommitdiffstats
path: root/security/smack/smack_access.c
blob: 58564195bb09c4f895efc04c811f02a28218f593 (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
/*
 * Copyright (C) 2007 Casey Schaufler <casey@schaufler-ca.com>
 *
 *      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, version 2.
 *
 * Author:
 *      Casey Schaufler <casey@schaufler-ca.com>
 *
 */

#include <linux/types.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include "smack.h"

struct smack_known smack_known_huh = {
	.smk_known	= "?",
	.smk_secid	= 2,
	.smk_cipso	= NULL,
};

struct smack_known smack_known_hat = {
	.smk_known	= "^",
	.smk_secid	= 3,
	.smk_cipso	= NULL,
};

struct smack_known smack_known_star = {
	.smk_known	= "*",
	.smk_secid	= 4,
	.smk_cipso	= NULL,
};

struct smack_known smack_known_floor = {
	.smk_known	= "_",
	.smk_secid	= 5,
	.smk_cipso	= NULL,
};

struct smack_known smack_known_invalid = {
	.smk_known	= "",
	.smk_secid	= 6,
	.smk_cipso	= NULL,
};

struct smack_known smack_known_web = {
	.smk_known	= "@",
	.smk_secid	= 7,
	.smk_cipso	= NULL,
};

LIST_HEAD(smack_known_list);

/*
 * The initial value needs to be bigger than any of the
 * known values above.
 */
static u32 smack_next_secid = 10;

/**
 * smk_access - determine if a subject has a specific access to an object
 * @subject_label: a pointer to the subject's Smack label
 * @object_label: a pointer to the object's Smack label
 * @request: the access requested, in "MAY" format
 *
 * This function looks up the subject/object pair in the
 * access rule list and returns 0 if the access is permitted,
 * non zero otherwise.
 *
 * Even though Smack labels are usually shared on smack_list
 * labels that come in off the network can't be imported
 * and added to the list for locking reasons.
 *
 * Therefore, it is necessary to check the contents of the labels,
 * not just the pointer values. Of course, in most cases the labels
 * will be on the list, so checking the pointers may be a worthwhile
 * optimization.
 */
int smk_access(char *subject_label, char *object_label, int request)
{
	u32 may = MAY_NOT;
	struct smack_rule *srp;

	/*
	 * Hardcoded comparisons.
	 *
	 * A star subject can't access any object.
	 */
	if (subject_label == smack_known_star.smk_known ||
	    strcmp(subject_label, smack_known_star.smk_known) == 0)
		return -EACCES;
	/*
	 * An internet object can be accessed by any subject.
	 * Tasks cannot be assigned the internet label.
	 * An internet subject can access any object.
	 */
	if (object_label == smack_known_web.smk_known ||
	    subject_label == smack_known_web.smk_known ||
	    strcmp(object_label, smack_known_web.smk_known) == 0 ||
	    strcmp(subject_label, smack_known_web.smk_known) == 0)
		return 0;
	/*
	 * A star object can be accessed by any subject.
	 */
	if (object_label == smack_known_star.smk_known ||
	    strcmp(object_label, smack_known_star.smk_known) == 0)
		return 0;
	/*
	 * An object can be accessed in any way by a subject
	 * with the same label.
	 */
	if (subject_label == object_label ||
	    strcmp(subject_label, object_label) == 0)
		return 0;
	/*
	 * A hat subject can read any object.
	 * A floor object can be read by any subject.
	 */
	if ((request & MAY_ANYREAD) == request) {
		if (object_label == smack_known_floor.smk_known ||
		    strcmp(object_label, smack_known_floor.smk_known) == 0)
			return 0;
		if (subject_label == smack_known_hat.smk_known ||
		    strcmp(subject_label, smack_known_hat.smk_known) == 0)
			return 0;
	}
	/*
	 * Beyond here an explicit relationship is required.
	 * If the requested access is contained in the available
	 * access (e.g. read is included in readwrite) it's
	 * good.
	 */
	rcu_read_lock();
	list_for_each_entry_rcu(srp, &smack_rule_list, list) {
		if (srp->smk_subject == subject_label ||
		    strcmp(srp->smk_subject, subject_label) == 0) {
			if (srp->smk_object == object_label ||
			    strcmp(srp->smk_object, object_label) == 0) {
				may = srp->smk_access;
				break;
			}
		}
	}
	rcu_read_unlock();
	/*
	 * This is a bit map operation.
	 */
	if ((request & may) == request)
		return 0;

	return -EACCES;
}

/**
 * smk_curacc - determine if current has a specific access to an object
 * @obj_label: a pointer to the object's Smack label
 * @mode: the access requested, in "MAY" format
 *
 * This function checks the current subject label/object label pair
 * in the access rule list and returns 0 if the access is permitted,
 * non zero otherwise. It allows that current may have the capability
 * to override the rules.
 */
int smk_curacc(char *obj_label, u32 mode)
{
	int rc;

	rc = smk_access(current_security(), obj_label, mode);
	if (rc == 0)
		return 0;

	/*
	 * Return if a specific label has been designated as the
	 * only one that gets privilege and current does not
	 * have that label.
	 */
	if (smack_onlycap != NULL && smack_onlycap != current->cred->security)
		return rc;

	if (capable(CAP_MAC_OVERRIDE))
		return 0;

	return rc;
}

static DEFINE_MUTEX(smack_known_lock);

/**
 * smk_import_entry - import a label, return the list entry
 * @string: a text string that might be a Smack label
 * @len: the maximum size, or zero if it is NULL terminated.
 *
 * Returns a pointer to the entry in the label list that
 * matches the passed string, adding it if necessary.
 */
struct smack_known *smk_import_entry(const char *string, int len)
{
	struct smack_known *skp;
	char smack[SMK_LABELLEN];
	int found;
	int i;

	if (len <= 0 || len > SMK_MAXLEN)
		len = SMK_MAXLEN;

	for (i = 0, found = 0; i < SMK_LABELLEN; i++) {
		if (found)
			smack[i] = '\0';
		else if (i >= len || string[i] > '~' || string[i] <= ' ' ||
			 string[i] == '/') {
			smack[i] = '\0';
			found = 1;
		} else
			smack[i] = string[i];
	}

	if (smack[0] == '\0')
		return NULL;

	mutex_lock(&smack_known_lock);

	found = 0;
	list_for_each_entry_rcu(skp, &smack_known_list, list) {
		if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0) {
			found = 1;
			break;
		}
	}

	if (found == 0) {
		skp = kzalloc(sizeof(struct smack_known), GFP_KERNEL);
		if (skp != NULL) {
			strncpy(skp->smk_known, smack, SMK_MAXLEN);
			skp->smk_secid = smack_next_secid++;
			skp->smk_cipso = NULL;
			spin_lock_init(&skp->smk_cipsolock);
			/*
			 * Make sure that the entry is actually
			 * filled before putting it on the list.
			 */
			list_add_rcu(&skp->list, &smack_known_list);
		}
	}

	mutex_unlock(&smack_known_lock);

	return skp;
}

/**
 * smk_import - import a smack label
 * @string: a text string that might be a Smack label
 * @len: the maximum size, or zero if it is NULL terminated.
 *
 * Returns a pointer to the label in the label list that
 * matches the passed string, adding it if necessary.
 */
char *smk_import(const char *string, int len)
{
	struct smack_known *skp;

	skp = smk_import_entry(string, len);
	if (skp == NULL)
		return NULL;
	return skp->smk_known;
}

/**
 * smack_from_secid - find the Smack label associated with a secid
 * @secid: an integer that might be associated with a Smack label
 *
 * Returns a pointer to the appropraite Smack label if there is one,
 * otherwise a pointer to the invalid Smack label.
 */
char *smack_from_secid(const u32 secid)
{
	struct smack_known *skp;

	rcu_read_lock();
	list_for_each_entry_rcu(skp, &smack_known_list, list) {
		if (skp->smk_secid == secid) {
			rcu_read_unlock();
			return skp->smk_known;
		}
	}

	/*
	 * If we got this far someone asked for the translation
	 * of a secid that is not on the list.
	 */
	rcu_read_unlock();
	return smack_known_invalid.smk_known;
}

/**
 * smack_to_secid - find the secid associated with a Smack label
 * @smack: the Smack label
 *
 * Returns the appropriate secid if there is one,
 * otherwise 0
 */
u32 smack_to_secid(const char *smack)
{
	struct smack_known *skp;

	rcu_read_lock();
	list_for_each_entry_rcu(skp, &smack_known_list, list) {
		if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0) {
			rcu_read_unlock();
			return skp->smk_secid;
		}
	}
	rcu_read_unlock();
	return 0;
}

/**
 * smack_from_cipso - find the Smack label associated with a CIPSO option
 * @level: Bell & LaPadula level from the network
 * @cp: Bell & LaPadula categories from the network
 * @result: where to put the Smack value
 *
 * This is a simple lookup in the label table.
 *
 * This is an odd duck as far as smack handling goes in that
 * it sends back a copy of the smack label rather than a pointer
 * to the master list. This is done because it is possible for
 * a foreign host to send a smack label that is new to this
 * machine and hence not on the list. That would not be an
 * issue except that adding an entry to the master list can't
 * be done at that point.
 */
void smack_from_cipso(u32 level, char *cp, char *result)
{
	struct smack_known *kp;
	char *final = NULL;

	rcu_read_lock();
	list_for_each_entry(kp, &smack_known_list, list) {
		if (kp->smk_cipso == NULL)
			continue;

		spin_lock_bh(&kp->smk_cipsolock);

		if (kp->smk_cipso->smk_level == level &&
		    memcmp(kp->smk_cipso->smk_catset, cp, SMK_LABELLEN) == 0)
			final = kp->smk_known;

		spin_unlock_bh(&kp->smk_cipsolock);
	}
	rcu_read_unlock();
	if (final == NULL)
		final = smack_known_huh.smk_known;
	strncpy(result, final, SMK_MAXLEN);
	return;
}

/**
 * smack_to_cipso - find the CIPSO option to go with a Smack label
 * @smack: a pointer to the smack label in question
 * @cp: where to put the result
 *
 * Returns zero if a value is available, non-zero otherwise.
 */
int smack_to_cipso(const char *smack, struct smack_cipso *cp)
{
	struct smack_known *kp;
	int found = 0;

	rcu_read_lock();
	list_for_each_entry_rcu(kp, &smack_known_list, list) {
		if (kp->smk_known == smack ||
		    strcmp(kp->smk_known, smack) == 0) {
			found = 1;
			break;
		}
	}
	rcu_read_unlock();

	if (found == 0 || kp->smk_cipso == NULL)
		return -ENOENT;

	memcpy(cp, kp->smk_cipso, sizeof(struct smack_cipso));
	return 0;
}