xref: /linux/security/apparmor/lib.c (revision 5c35a02c545a7bbe77f3a1ae337d9e29beed079b) 
1 /*
2  * AppArmor security module
3  *
4  * This file contains basic common functions used in AppArmor
5  *
6  * Copyright (C) 1998-2008 Novell/SUSE
7  * Copyright 2009-2010 Canonical Ltd.
8  *
9  * This program is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU General Public License as
11  * published by the Free Software Foundation, version 2 of the
12  * License.
13  */
14 
15 #include <linux/ctype.h>
16 #include <linux/mm.h>
17 #include <linux/slab.h>
18 #include <linux/string.h>
19 #include <linux/vmalloc.h>
20 
21 #include "include/audit.h"
22 #include "include/apparmor.h"
23 #include "include/lib.h"
24 #include "include/perms.h"
25 #include "include/policy.h"
26 
27 struct aa_perms nullperms;
28 struct aa_perms allperms = { .allow = ALL_PERMS_MASK,
29 			     .quiet = ALL_PERMS_MASK,
30 			     .hide = ALL_PERMS_MASK };
31 
32 /**
33  * aa_split_fqname - split a fqname into a profile and namespace name
34  * @fqname: a full qualified name in namespace profile format (NOT NULL)
35  * @ns_name: pointer to portion of the string containing the ns name (NOT NULL)
36  *
37  * Returns: profile name or NULL if one is not specified
38  *
39  * Split a namespace name from a profile name (see policy.c for naming
40  * description).  If a portion of the name is missing it returns NULL for
41  * that portion.
42  *
43  * NOTE: may modify the @fqname string.  The pointers returned point
44  *       into the @fqname string.
45  */
46 char *aa_split_fqname(char *fqname, char **ns_name)
47 {
48 	char *name = strim(fqname);
49 
50 	*ns_name = NULL;
51 	if (name[0] == ':') {
52 		char *split = strchr(&name[1], ':');
53 		*ns_name = skip_spaces(&name[1]);
54 		if (split) {
55 			/* overwrite ':' with \0 */
56 			*split++ = 0;
57 			if (strncmp(split, "//", 2) == 0)
58 				split += 2;
59 			name = skip_spaces(split);
60 		} else
61 			/* a ns name without a following profile is allowed */
62 			name = NULL;
63 	}
64 	if (name && *name == 0)
65 		name = NULL;
66 
67 	return name;
68 }
69 
70 /**
71  * skipn_spaces - Removes leading whitespace from @str.
72  * @str: The string to be stripped.
73  *
74  * Returns a pointer to the first non-whitespace character in @str.
75  * if all whitespace will return NULL
76  */
77 
78 const char *skipn_spaces(const char *str, size_t n)
79 {
80 	for (; n && isspace(*str); --n)
81 		++str;
82 	if (n)
83 		return (char *)str;
84 	return NULL;
85 }
86 
87 const char *aa_splitn_fqname(const char *fqname, size_t n, const char **ns_name,
88 			     size_t *ns_len)
89 {
90 	const char *end = fqname + n;
91 	const char *name = skipn_spaces(fqname, n);
92 
93 	if (!name)
94 		return NULL;
95 	*ns_name = NULL;
96 	*ns_len = 0;
97 	if (name[0] == ':') {
98 		char *split = strnchr(&name[1], end - &name[1], ':');
99 		*ns_name = skipn_spaces(&name[1], end - &name[1]);
100 		if (!*ns_name)
101 			return NULL;
102 		if (split) {
103 			*ns_len = split - *ns_name;
104 			if (*ns_len == 0)
105 				*ns_name = NULL;
106 			split++;
107 			if (end - split > 1 && strncmp(split, "//", 2) == 0)
108 				split += 2;
109 			name = skipn_spaces(split, end - split);
110 		} else {
111 			/* a ns name without a following profile is allowed */
112 			name = NULL;
113 			*ns_len = end - *ns_name;
114 		}
115 	}
116 	if (name && *name == 0)
117 		name = NULL;
118 
119 	return name;
120 }
121 
122 /**
123  * aa_info_message - log a none profile related status message
124  * @str: message to log
125  */
126 void aa_info_message(const char *str)
127 {
128 	if (audit_enabled) {
129 		DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_NONE, NULL);
130 
131 		aad(&sa)->info = str;
132 		aa_audit_msg(AUDIT_APPARMOR_STATUS, &sa, NULL);
133 	}
134 	printk(KERN_INFO "AppArmor: %s\n", str);
135 }
136 
137 __counted char *aa_str_alloc(int size, gfp_t gfp)
138 {
139 	struct counted_str *str;
140 
141 	str = kmalloc(sizeof(struct counted_str) + size, gfp);
142 	if (!str)
143 		return NULL;
144 
145 	kref_init(&str->count);
146 	return str->name;
147 }
148 
149 void aa_str_kref(struct kref *kref)
150 {
151 	kfree(container_of(kref, struct counted_str, count));
152 }
153 
154 
155 const char aa_file_perm_chrs[] = "xwracd         km l     ";
156 const char *aa_file_perm_names[] = {
157 	"exec",
158 	"write",
159 	"read",
160 	"append",
161 
162 	"create",
163 	"delete",
164 	"open",
165 	"rename",
166 
167 	"setattr",
168 	"getattr",
169 	"setcred",
170 	"getcred",
171 
172 	"chmod",
173 	"chown",
174 	"chgrp",
175 	"lock",
176 
177 	"mmap",
178 	"mprot",
179 	"link",
180 	"snapshot",
181 
182 	"unknown",
183 	"unknown",
184 	"unknown",
185 	"unknown",
186 
187 	"unknown",
188 	"unknown",
189 	"unknown",
190 	"unknown",
191 
192 	"stack",
193 	"change_onexec",
194 	"change_profile",
195 	"change_hat",
196 };
197 
198 /**
199  * aa_perm_mask_to_str - convert a perm mask to its short string
200  * @str: character buffer to store string in (at least 10 characters)
201  * @mask: permission mask to convert
202  */
203 void aa_perm_mask_to_str(char *str, const char *chrs, u32 mask)
204 {
205 	unsigned int i, perm = 1;
206 
207 	for (i = 0; i < 32; perm <<= 1, i++) {
208 		if (mask & perm)
209 			*str++ = chrs[i];
210 	}
211 	*str = '\0';
212 }
213 
214 void aa_audit_perm_names(struct audit_buffer *ab, const char * const *names,
215 			 u32 mask)
216 {
217 	const char *fmt = "%s";
218 	unsigned int i, perm = 1;
219 	bool prev = false;
220 
221 	for (i = 0; i < 32; perm <<= 1, i++) {
222 		if (mask & perm) {
223 			audit_log_format(ab, fmt, names[i]);
224 			if (!prev) {
225 				prev = true;
226 				fmt = " %s";
227 			}
228 		}
229 	}
230 }
231 
232 void aa_audit_perm_mask(struct audit_buffer *ab, u32 mask, const char *chrs,
233 			u32 chrsmask, const char * const *names, u32 namesmask)
234 {
235 	char str[33];
236 
237 	audit_log_format(ab, "\"");
238 	if ((mask & chrsmask) && chrs) {
239 		aa_perm_mask_to_str(str, chrs, mask & chrsmask);
240 		mask &= ~chrsmask;
241 		audit_log_format(ab, "%s", str);
242 		if (mask & namesmask)
243 			audit_log_format(ab, " ");
244 	}
245 	if ((mask & namesmask) && names)
246 		aa_audit_perm_names(ab, names, mask & namesmask);
247 	audit_log_format(ab, "\"");
248 }
249 
250 /**
251  * aa_audit_perms_cb - generic callback fn for auditing perms
252  * @ab: audit buffer (NOT NULL)
253  * @va: audit struct to audit values of (NOT NULL)
254  */
255 static void aa_audit_perms_cb(struct audit_buffer *ab, void *va)
256 {
257 	struct common_audit_data *sa = va;
258 
259 	if (aad(sa)->request) {
260 		audit_log_format(ab, " requested_mask=");
261 		aa_audit_perm_mask(ab, aad(sa)->request, aa_file_perm_chrs,
262 				   PERMS_CHRS_MASK, aa_file_perm_names,
263 				   PERMS_NAMES_MASK);
264 	}
265 	if (aad(sa)->denied) {
266 		audit_log_format(ab, "denied_mask=");
267 		aa_audit_perm_mask(ab, aad(sa)->denied, aa_file_perm_chrs,
268 				   PERMS_CHRS_MASK, aa_file_perm_names,
269 				   PERMS_NAMES_MASK);
270 	}
271 	audit_log_format(ab, " peer=");
272 	aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
273 				      FLAGS_NONE, GFP_ATOMIC);
274 }
275 
276 /**
277  * aa_apply_modes_to_perms - apply namespace and profile flags to perms
278  * @profile: that perms where computed from
279  * @perms: perms to apply mode modifiers to
280  *
281  * TODO: split into profile and ns based flags for when accumulating perms
282  */
283 void aa_apply_modes_to_perms(struct aa_profile *profile, struct aa_perms *perms)
284 {
285 	switch (AUDIT_MODE(profile)) {
286 	case AUDIT_ALL:
287 		perms->audit = ALL_PERMS_MASK;
288 		/* fall through */
289 	case AUDIT_NOQUIET:
290 		perms->quiet = 0;
291 		break;
292 	case AUDIT_QUIET:
293 		perms->audit = 0;
294 		/* fall through */
295 	case AUDIT_QUIET_DENIED:
296 		perms->quiet = ALL_PERMS_MASK;
297 		break;
298 	}
299 
300 	if (KILL_MODE(profile))
301 		perms->kill = ALL_PERMS_MASK;
302 	else if (COMPLAIN_MODE(profile))
303 		perms->complain = ALL_PERMS_MASK;
304 /*
305  *  TODO:
306  *	else if (PROMPT_MODE(profile))
307  *		perms->prompt = ALL_PERMS_MASK;
308  */
309 }
310 
311 static u32 map_other(u32 x)
312 {
313 	return ((x & 0x3) << 8) |	/* SETATTR/GETATTR */
314 		((x & 0x1c) << 18) |	/* ACCEPT/BIND/LISTEN */
315 		((x & 0x60) << 19);	/* SETOPT/GETOPT */
316 }
317 
318 void aa_compute_perms(struct aa_dfa *dfa, unsigned int state,
319 		      struct aa_perms *perms)
320 {
321 	*perms = (struct aa_perms) {
322 		.allow = dfa_user_allow(dfa, state),
323 		.audit = dfa_user_audit(dfa, state),
324 		.quiet = dfa_user_quiet(dfa, state),
325 	};
326 
327 	/* for v5 perm mapping in the policydb, the other set is used
328 	 * to extend the general perm set
329 	 */
330 	perms->allow |= map_other(dfa_other_allow(dfa, state));
331 	perms->audit |= map_other(dfa_other_audit(dfa, state));
332 	perms->quiet |= map_other(dfa_other_quiet(dfa, state));
333 //	perms->xindex = dfa_user_xindex(dfa, state);
334 }
335 
336 /**
337  * aa_perms_accum_raw - accumulate perms with out masking off overlapping perms
338  * @accum - perms struct to accumulate into
339  * @addend - perms struct to add to @accum
340  */
341 void aa_perms_accum_raw(struct aa_perms *accum, struct aa_perms *addend)
342 {
343 	accum->deny |= addend->deny;
344 	accum->allow &= addend->allow & ~addend->deny;
345 	accum->audit |= addend->audit & addend->allow;
346 	accum->quiet &= addend->quiet & ~addend->allow;
347 	accum->kill |= addend->kill & ~addend->allow;
348 	accum->stop |= addend->stop & ~addend->allow;
349 	accum->complain |= addend->complain & ~addend->allow & ~addend->deny;
350 	accum->cond |= addend->cond & ~addend->allow & ~addend->deny;
351 	accum->hide &= addend->hide & ~addend->allow;
352 	accum->prompt |= addend->prompt & ~addend->allow & ~addend->deny;
353 }
354 
355 /**
356  * aa_perms_accum - accumulate perms, masking off overlapping perms
357  * @accum - perms struct to accumulate into
358  * @addend - perms struct to add to @accum
359  */
360 void aa_perms_accum(struct aa_perms *accum, struct aa_perms *addend)
361 {
362 	accum->deny |= addend->deny;
363 	accum->allow &= addend->allow & ~accum->deny;
364 	accum->audit |= addend->audit & accum->allow;
365 	accum->quiet &= addend->quiet & ~accum->allow;
366 	accum->kill |= addend->kill & ~accum->allow;
367 	accum->stop |= addend->stop & ~accum->allow;
368 	accum->complain |= addend->complain & ~accum->allow & ~accum->deny;
369 	accum->cond |= addend->cond & ~accum->allow & ~accum->deny;
370 	accum->hide &= addend->hide & ~accum->allow;
371 	accum->prompt |= addend->prompt & ~accum->allow & ~accum->deny;
372 }
373 
374 void aa_profile_match_label(struct aa_profile *profile, struct aa_label *label,
375 			    int type, u32 request, struct aa_perms *perms)
376 {
377 	/* TODO: doesn't yet handle extended types */
378 	unsigned int state;
379 
380 	state = aa_dfa_next(profile->policy.dfa,
381 			    profile->policy.start[AA_CLASS_LABEL],
382 			    type);
383 	aa_label_match(profile, label, state, false, request, perms);
384 }
385 
386 
387 /* currently unused */
388 int aa_profile_label_perm(struct aa_profile *profile, struct aa_profile *target,
389 			  u32 request, int type, u32 *deny,
390 			  struct common_audit_data *sa)
391 {
392 	struct aa_perms perms;
393 
394 	aad(sa)->label = &profile->label;
395 	aad(sa)->peer = &target->label;
396 	aad(sa)->request = request;
397 
398 	aa_profile_match_label(profile, &target->label, type, request, &perms);
399 	aa_apply_modes_to_perms(profile, &perms);
400 	*deny |= request & perms.deny;
401 	return aa_check_perms(profile, &perms, request, sa, aa_audit_perms_cb);
402 }
403 
404 /**
405  * aa_check_perms - do audit mode selection based on perms set
406  * @profile: profile being checked
407  * @perms: perms computed for the request
408  * @request: requested perms
409  * @deny: Returns: explicit deny set
410  * @sa: initialized audit structure (MAY BE NULL if not auditing)
411  * @cb: callback fn for type specific fields (MAY BE NULL)
412  *
413  * Returns: 0 if permission else error code
414  *
415  * Note: profile audit modes need to be set before calling by setting the
416  *       perm masks appropriately.
417  *
418  *       If not auditing then complain mode is not enabled and the
419  *       error code will indicate whether there was an explicit deny
420  *	 with a positive value.
421  */
422 int aa_check_perms(struct aa_profile *profile, struct aa_perms *perms,
423 		   u32 request, struct common_audit_data *sa,
424 		   void (*cb)(struct audit_buffer *, void *))
425 {
426 	int type, error;
427 	u32 denied = request & (~perms->allow | perms->deny);
428 
429 	if (likely(!denied)) {
430 		/* mask off perms that are not being force audited */
431 		request &= perms->audit;
432 		if (!request || !sa)
433 			return 0;
434 
435 		type = AUDIT_APPARMOR_AUDIT;
436 		error = 0;
437 	} else {
438 		error = -EACCES;
439 
440 		if (denied & perms->kill)
441 			type = AUDIT_APPARMOR_KILL;
442 		else if (denied == (denied & perms->complain))
443 			type = AUDIT_APPARMOR_ALLOWED;
444 		else
445 			type = AUDIT_APPARMOR_DENIED;
446 
447 		if (denied == (denied & perms->hide))
448 			error = -ENOENT;
449 
450 		denied &= ~perms->quiet;
451 		if (!sa || !denied)
452 			return error;
453 	}
454 
455 	if (sa) {
456 		aad(sa)->label = &profile->label;
457 		aad(sa)->request = request;
458 		aad(sa)->denied = denied;
459 		aad(sa)->error = error;
460 		aa_audit_msg(type, sa, cb);
461 	}
462 
463 	if (type == AUDIT_APPARMOR_ALLOWED)
464 		error = 0;
465 
466 	return error;
467 }
468 
469 
470 /**
471  * aa_policy_init - initialize a policy structure
472  * @policy: policy to initialize  (NOT NULL)
473  * @prefix: prefix name if any is required.  (MAYBE NULL)
474  * @name: name of the policy, init will make a copy of it  (NOT NULL)
475  * @gfp: allocation mode
476  *
477  * Note: this fn creates a copy of strings passed in
478  *
479  * Returns: true if policy init successful
480  */
481 bool aa_policy_init(struct aa_policy *policy, const char *prefix,
482 		    const char *name, gfp_t gfp)
483 {
484 	char *hname;
485 
486 	/* freed by policy_free */
487 	if (prefix) {
488 		hname = aa_str_alloc(strlen(prefix) + strlen(name) + 3, gfp);
489 		if (hname)
490 			sprintf(hname, "%s//%s", prefix, name);
491 	} else {
492 		hname = aa_str_alloc(strlen(name) + 1, gfp);
493 		if (hname)
494 			strcpy(hname, name);
495 	}
496 	if (!hname)
497 		return false;
498 	policy->hname = hname;
499 	/* base.name is a substring of fqname */
500 	policy->name = basename(policy->hname);
501 	INIT_LIST_HEAD(&policy->list);
502 	INIT_LIST_HEAD(&policy->profiles);
503 
504 	return true;
505 }
506 
507 /**
508  * aa_policy_destroy - free the elements referenced by @policy
509  * @policy: policy that is to have its elements freed  (NOT NULL)
510  */
511 void aa_policy_destroy(struct aa_policy *policy)
512 {
513 	AA_BUG(on_list_rcu(&policy->profiles));
514 	AA_BUG(on_list_rcu(&policy->list));
515 
516 	/* don't free name as its a subset of hname */
517 	aa_put_str(policy->hname);
518 }
519