1/*
2 * AppArmor security module
3 *
4 * This file contains AppArmor mediation of files
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 "include/apparmor.h"
16#include "include/audit.h"
17#include "include/file.h"
18#include "include/match.h"
19#include "include/path.h"
20#include "include/policy.h"
21
22struct file_perms nullperms;
23
24
25/**
26 * audit_file_mask - convert mask to permission string
27 * @buffer: buffer to write string to (NOT NULL)
28 * @mask: permission mask to convert
29 */
30static void audit_file_mask(struct audit_buffer *ab, u32 mask)
31{
32	char str[10];
33
34	char *m = str;
35
36	if (mask & AA_EXEC_MMAP)
37		*m++ = 'm';
38	if (mask & (MAY_READ | AA_MAY_META_READ))
39		*m++ = 'r';
40	if (mask & (MAY_WRITE | AA_MAY_META_WRITE | AA_MAY_CHMOD |
41		    AA_MAY_CHOWN))
42		*m++ = 'w';
43	else if (mask & MAY_APPEND)
44		*m++ = 'a';
45	if (mask & AA_MAY_CREATE)
46		*m++ = 'c';
47	if (mask & AA_MAY_DELETE)
48		*m++ = 'd';
49	if (mask & AA_MAY_LINK)
50		*m++ = 'l';
51	if (mask & AA_MAY_LOCK)
52		*m++ = 'k';
53	if (mask & MAY_EXEC)
54		*m++ = 'x';
55	*m = '\0';
56
57	audit_log_string(ab, str);
58}
59
60/**
61 * file_audit_cb - call back for file specific audit fields
62 * @ab: audit_buffer  (NOT NULL)
63 * @va: audit struct to audit values of  (NOT NULL)
64 */
65static void file_audit_cb(struct audit_buffer *ab, void *va)
66{
67	struct common_audit_data *sa = va;
68	kuid_t fsuid = current_fsuid();
69
70	if (sa->aad->fs.request & AA_AUDIT_FILE_MASK) {
71		audit_log_format(ab, " requested_mask=");
72		audit_file_mask(ab, sa->aad->fs.request);
73	}
74	if (sa->aad->fs.denied & AA_AUDIT_FILE_MASK) {
75		audit_log_format(ab, " denied_mask=");
76		audit_file_mask(ab, sa->aad->fs.denied);
77	}
78	if (sa->aad->fs.request & AA_AUDIT_FILE_MASK) {
79		audit_log_format(ab, " fsuid=%d",
80				 from_kuid(&init_user_ns, fsuid));
81		audit_log_format(ab, " ouid=%d",
82				 from_kuid(&init_user_ns, sa->aad->fs.ouid));
83	}
84
85	if (sa->aad->fs.target) {
86		audit_log_format(ab, " target=");
87		audit_log_untrustedstring(ab, sa->aad->fs.target);
88	}
89}
90
91/**
92 * aa_audit_file - handle the auditing of file operations
93 * @profile: the profile being enforced  (NOT NULL)
94 * @perms: the permissions computed for the request (NOT NULL)
95 * @gfp: allocation flags
96 * @op: operation being mediated
97 * @request: permissions requested
98 * @name: name of object being mediated (MAYBE NULL)
99 * @target: name of target (MAYBE NULL)
100 * @ouid: object uid
101 * @info: extra information message (MAYBE NULL)
102 * @error: 0 if operation allowed else failure error code
103 *
104 * Returns: %0 or error on failure
105 */
106int aa_audit_file(struct aa_profile *profile, struct file_perms *perms,
107		  gfp_t gfp, int op, u32 request, const char *name,
108		  const char *target, kuid_t ouid, const char *info, int error)
109{
110	int type = AUDIT_APPARMOR_AUTO;
111	struct common_audit_data sa;
112	struct apparmor_audit_data aad = {0,};
113	sa.type = LSM_AUDIT_DATA_NONE;
114	sa.aad = &aad;
115	aad.op = op,
116	aad.fs.request = request;
117	aad.name = name;
118	aad.fs.target = target;
119	aad.fs.ouid = ouid;
120	aad.info = info;
121	aad.error = error;
122
123	if (likely(!sa.aad->error)) {
124		u32 mask = perms->audit;
125
126		if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
127			mask = 0xffff;
128
129		/* mask off perms that are not being force audited */
130		sa.aad->fs.request &= mask;
131
132		if (likely(!sa.aad->fs.request))
133			return 0;
134		type = AUDIT_APPARMOR_AUDIT;
135	} else {
136		/* only report permissions that were denied */
137		sa.aad->fs.request = sa.aad->fs.request & ~perms->allow;
138
139		if (sa.aad->fs.request & perms->kill)
140			type = AUDIT_APPARMOR_KILL;
141
142		/* quiet known rejects, assumes quiet and kill do not overlap */
143		if ((sa.aad->fs.request & perms->quiet) &&
144		    AUDIT_MODE(profile) != AUDIT_NOQUIET &&
145		    AUDIT_MODE(profile) != AUDIT_ALL)
146			sa.aad->fs.request &= ~perms->quiet;
147
148		if (!sa.aad->fs.request)
149			return COMPLAIN_MODE(profile) ? 0 : sa.aad->error;
150	}
151
152	sa.aad->fs.denied = sa.aad->fs.request & ~perms->allow;
153	return aa_audit(type, profile, gfp, &sa, file_audit_cb);
154}
155
156/**
157 * map_old_perms - map old file perms layout to the new layout
158 * @old: permission set in old mapping
159 *
160 * Returns: new permission mapping
161 */
162static u32 map_old_perms(u32 old)
163{
164	u32 new = old & 0xf;
165	if (old & MAY_READ)
166		new |= AA_MAY_META_READ;
167	if (old & MAY_WRITE)
168		new |= AA_MAY_META_WRITE | AA_MAY_CREATE | AA_MAY_DELETE |
169			AA_MAY_CHMOD | AA_MAY_CHOWN;
170	if (old & 0x10)
171		new |= AA_MAY_LINK;
172	/* the old mapping lock and link_subset flags where overlaid
173	 * and use was determined by part of a pair that they were in
174	 */
175	if (old & 0x20)
176		new |= AA_MAY_LOCK | AA_LINK_SUBSET;
177	if (old & 0x40)	/* AA_EXEC_MMAP */
178		new |= AA_EXEC_MMAP;
179
180	return new;
181}
182
183/**
184 * compute_perms - convert dfa compressed perms to internal perms
185 * @dfa: dfa to compute perms for   (NOT NULL)
186 * @state: state in dfa
187 * @cond:  conditions to consider  (NOT NULL)
188 *
189 * TODO: convert from dfa + state to permission entry, do computation conversion
190 *       at load time.
191 *
192 * Returns: computed permission set
193 */
194static struct file_perms compute_perms(struct aa_dfa *dfa, unsigned int state,
195				       struct path_cond *cond)
196{
197	struct file_perms perms;
198
199	/* FIXME: change over to new dfa format
200	 * currently file perms are encoded in the dfa, new format
201	 * splits the permissions from the dfa.  This mapping can be
202	 * done at profile load
203	 */
204	perms.kill = 0;
205
206	if (uid_eq(current_fsuid(), cond->uid)) {
207		perms.allow = map_old_perms(dfa_user_allow(dfa, state));
208		perms.audit = map_old_perms(dfa_user_audit(dfa, state));
209		perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
210		perms.xindex = dfa_user_xindex(dfa, state);
211	} else {
212		perms.allow = map_old_perms(dfa_other_allow(dfa, state));
213		perms.audit = map_old_perms(dfa_other_audit(dfa, state));
214		perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
215		perms.xindex = dfa_other_xindex(dfa, state);
216	}
217	perms.allow |= AA_MAY_META_READ;
218
219	/* change_profile wasn't determined by ownership in old mapping */
220	if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
221		perms.allow |= AA_MAY_CHANGE_PROFILE;
222	if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
223		perms.allow |= AA_MAY_ONEXEC;
224
225	return perms;
226}
227
228/**
229 * aa_str_perms - find permission that match @name
230 * @dfa: to match against  (MAYBE NULL)
231 * @state: state to start matching in
232 * @name: string to match against dfa  (NOT NULL)
233 * @cond: conditions to consider for permission set computation  (NOT NULL)
234 * @perms: Returns - the permissions found when matching @name
235 *
236 * Returns: the final state in @dfa when beginning @start and walking @name
237 */
238unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
239			  const char *name, struct path_cond *cond,
240			  struct file_perms *perms)
241{
242	unsigned int state;
243	if (!dfa) {
244		*perms = nullperms;
245		return DFA_NOMATCH;
246	}
247
248	state = aa_dfa_match(dfa, start, name);
249	*perms = compute_perms(dfa, state, cond);
250
251	return state;
252}
253
254/**
255 * is_deleted - test if a file has been completely unlinked
256 * @dentry: dentry of file to test for deletion  (NOT NULL)
257 *
258 * Returns: %1 if deleted else %0
259 */
260static inline bool is_deleted(struct dentry *dentry)
261{
262	if (d_unlinked(dentry) && d_backing_inode(dentry)->i_nlink == 0)
263		return 1;
264	return 0;
265}
266
267/**
268 * aa_path_perm - do permissions check & audit for @path
269 * @op: operation being checked
270 * @profile: profile being enforced  (NOT NULL)
271 * @path: path to check permissions of  (NOT NULL)
272 * @flags: any additional path flags beyond what the profile specifies
273 * @request: requested permissions
274 * @cond: conditional info for this request  (NOT NULL)
275 *
276 * Returns: %0 else error if access denied or other error
277 */
278int aa_path_perm(int op, struct aa_profile *profile, struct path *path,
279		 int flags, u32 request, struct path_cond *cond)
280{
281	char *buffer = NULL;
282	struct file_perms perms = {};
283	const char *name, *info = NULL;
284	int error;
285
286	flags |= profile->path_flags | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0);
287	error = aa_path_name(path, flags, &buffer, &name, &info);
288	if (error) {
289		if (error == -ENOENT && is_deleted(path->dentry)) {
290			/* Access to open files that are deleted are
291			 * give a pass (implicit delegation)
292			 */
293			error = 0;
294			info = NULL;
295			perms.allow = request;
296		}
297	} else {
298		aa_str_perms(profile->file.dfa, profile->file.start, name, cond,
299			     &perms);
300		if (request & ~perms.allow)
301			error = -EACCES;
302	}
303	error = aa_audit_file(profile, &perms, GFP_KERNEL, op, request, name,
304			      NULL, cond->uid, info, error);
305	kfree(buffer);
306
307	return error;
308}
309
310/**
311 * xindex_is_subset - helper for aa_path_link
312 * @link: link permission set
313 * @target: target permission set
314 *
315 * test target x permissions are equal OR a subset of link x permissions
316 * this is done as part of the subset test, where a hardlink must have
317 * a subset of permissions that the target has.
318 *
319 * Returns: %1 if subset else %0
320 */
321static inline bool xindex_is_subset(u32 link, u32 target)
322{
323	if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
324	    ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
325		return 0;
326
327	return 1;
328}
329
330/**
331 * aa_path_link - Handle hard link permission check
332 * @profile: the profile being enforced  (NOT NULL)
333 * @old_dentry: the target dentry  (NOT NULL)
334 * @new_dir: directory the new link will be created in  (NOT NULL)
335 * @new_dentry: the link being created  (NOT NULL)
336 *
337 * Handle the permission test for a link & target pair.  Permission
338 * is encoded as a pair where the link permission is determined
339 * first, and if allowed, the target is tested.  The target test
340 * is done from the point of the link match (not start of DFA)
341 * making the target permission dependent on the link permission match.
342 *
343 * The subset test if required forces that permissions granted
344 * on link are a subset of the permission granted to target.
345 *
346 * Returns: %0 if allowed else error
347 */
348int aa_path_link(struct aa_profile *profile, struct dentry *old_dentry,
349		 struct path *new_dir, struct dentry *new_dentry)
350{
351	struct path link = { new_dir->mnt, new_dentry };
352	struct path target = { new_dir->mnt, old_dentry };
353	struct path_cond cond = {
354		d_backing_inode(old_dentry)->i_uid,
355		d_backing_inode(old_dentry)->i_mode
356	};
357	char *buffer = NULL, *buffer2 = NULL;
358	const char *lname, *tname = NULL, *info = NULL;
359	struct file_perms lperms, perms;
360	u32 request = AA_MAY_LINK;
361	unsigned int state;
362	int error;
363
364	lperms = nullperms;
365
366	/* buffer freed below, lname is pointer in buffer */
367	error = aa_path_name(&link, profile->path_flags, &buffer, &lname,
368			     &info);
369	if (error)
370		goto audit;
371
372	/* buffer2 freed below, tname is pointer in buffer2 */
373	error = aa_path_name(&target, profile->path_flags, &buffer2, &tname,
374			     &info);
375	if (error)
376		goto audit;
377
378	error = -EACCES;
379	/* aa_str_perms - handles the case of the dfa being NULL */
380	state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
381			     &cond, &lperms);
382
383	if (!(lperms.allow & AA_MAY_LINK))
384		goto audit;
385
386	/* test to see if target can be paired with link */
387	state = aa_dfa_null_transition(profile->file.dfa, state);
388	aa_str_perms(profile->file.dfa, state, tname, &cond, &perms);
389
390	/* force audit/quiet masks for link are stored in the second entry
391	 * in the link pair.
392	 */
393	lperms.audit = perms.audit;
394	lperms.quiet = perms.quiet;
395	lperms.kill = perms.kill;
396
397	if (!(perms.allow & AA_MAY_LINK)) {
398		info = "target restricted";
399		goto audit;
400	}
401
402	/* done if link subset test is not required */
403	if (!(perms.allow & AA_LINK_SUBSET))
404		goto done_tests;
405
406	/* Do link perm subset test requiring allowed permission on link are a
407	 * subset of the allowed permissions on target.
408	 */
409	aa_str_perms(profile->file.dfa, profile->file.start, tname, &cond,
410		     &perms);
411
412	/* AA_MAY_LINK is not considered in the subset test */
413	request = lperms.allow & ~AA_MAY_LINK;
414	lperms.allow &= perms.allow | AA_MAY_LINK;
415
416	request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
417	if (request & ~lperms.allow) {
418		goto audit;
419	} else if ((lperms.allow & MAY_EXEC) &&
420		   !xindex_is_subset(lperms.xindex, perms.xindex)) {
421		lperms.allow &= ~MAY_EXEC;
422		request |= MAY_EXEC;
423		info = "link not subset of target";
424		goto audit;
425	}
426
427done_tests:
428	error = 0;
429
430audit:
431	error = aa_audit_file(profile, &lperms, GFP_KERNEL, OP_LINK, request,
432			      lname, tname, cond.uid, info, error);
433	kfree(buffer);
434	kfree(buffer2);
435
436	return error;
437}
438
439/**
440 * aa_file_perm - do permission revalidation check & audit for @file
441 * @op: operation being checked
442 * @profile: profile being enforced   (NOT NULL)
443 * @file: file to revalidate access permissions on  (NOT NULL)
444 * @request: requested permissions
445 *
446 * Returns: %0 if access allowed else error
447 */
448int aa_file_perm(int op, struct aa_profile *profile, struct file *file,
449		 u32 request)
450{
451	struct path_cond cond = {
452		.uid = file_inode(file)->i_uid,
453		.mode = file_inode(file)->i_mode
454	};
455
456	return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED,
457			    request, &cond);
458}
459