blob: 5d176f2530c9820873d57c082ff787c5eca38de5 [file] [log] [blame]
John Johansen6380bd82010-07-29 14:48:04 -07001/*
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 uid_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", fsuid);
80 audit_log_format(ab, " ouid=%d", sa->aad.fs.ouid);
81 }
82
83 if (sa->aad.fs.target) {
84 audit_log_format(ab, " target=");
85 audit_log_untrustedstring(ab, sa->aad.fs.target);
86 }
87}
88
89/**
90 * aa_audit_file - handle the auditing of file operations
91 * @profile: the profile being enforced (NOT NULL)
92 * @perms: the permissions computed for the request (NOT NULL)
93 * @gfp: allocation flags
94 * @op: operation being mediated
95 * @request: permissions requested
96 * @name: name of object being mediated (MAYBE NULL)
97 * @target: name of target (MAYBE NULL)
98 * @ouid: object uid
99 * @info: extra information message (MAYBE NULL)
100 * @error: 0 if operation allowed else failure error code
101 *
102 * Returns: %0 or error on failure
103 */
104int aa_audit_file(struct aa_profile *profile, struct file_perms *perms,
105 gfp_t gfp, int op, u32 request, const char *name,
106 const char *target, uid_t ouid, const char *info, int error)
107{
108 int type = AUDIT_APPARMOR_AUTO;
109 struct common_audit_data sa;
110 COMMON_AUDIT_DATA_INIT(&sa, NONE);
111 sa.aad.op = op,
112 sa.aad.fs.request = request;
113 sa.aad.name = name;
114 sa.aad.fs.target = target;
115 sa.aad.fs.ouid = ouid;
116 sa.aad.info = info;
117 sa.aad.error = error;
118
119 if (likely(!sa.aad.error)) {
120 u32 mask = perms->audit;
121
122 if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
123 mask = 0xffff;
124
125 /* mask off perms that are not being force audited */
126 sa.aad.fs.request &= mask;
127
128 if (likely(!sa.aad.fs.request))
129 return 0;
130 type = AUDIT_APPARMOR_AUDIT;
131 } else {
132 /* only report permissions that were denied */
133 sa.aad.fs.request = sa.aad.fs.request & ~perms->allow;
134
135 if (sa.aad.fs.request & perms->kill)
136 type = AUDIT_APPARMOR_KILL;
137
138 /* quiet known rejects, assumes quiet and kill do not overlap */
139 if ((sa.aad.fs.request & perms->quiet) &&
140 AUDIT_MODE(profile) != AUDIT_NOQUIET &&
141 AUDIT_MODE(profile) != AUDIT_ALL)
142 sa.aad.fs.request &= ~perms->quiet;
143
144 if (!sa.aad.fs.request)
145 return COMPLAIN_MODE(profile) ? 0 : sa.aad.error;
146 }
147
148 sa.aad.fs.denied = sa.aad.fs.request & ~perms->allow;
149 return aa_audit(type, profile, gfp, &sa, file_audit_cb);
150}
151
152/**
153 * map_old_perms - map old file perms layout to the new layout
154 * @old: permission set in old mapping
155 *
156 * Returns: new permission mapping
157 */
158static u32 map_old_perms(u32 old)
159{
160 u32 new = old & 0xf;
161 if (old & MAY_READ)
162 new |= AA_MAY_META_READ;
163 if (old & MAY_WRITE)
164 new |= AA_MAY_META_WRITE | AA_MAY_CREATE | AA_MAY_DELETE |
165 AA_MAY_CHMOD | AA_MAY_CHOWN;
166 if (old & 0x10)
167 new |= AA_MAY_LINK;
168 /* the old mapping lock and link_subset flags where overlaid
169 * and use was determined by part of a pair that they were in
170 */
171 if (old & 0x20)
172 new |= AA_MAY_LOCK | AA_LINK_SUBSET;
173 if (old & 0x40) /* AA_EXEC_MMAP */
174 new |= AA_EXEC_MMAP;
175
John Johansen6380bd82010-07-29 14:48:04 -0700176 return new;
177}
178
179/**
180 * compute_perms - convert dfa compressed perms to internal perms
181 * @dfa: dfa to compute perms for (NOT NULL)
182 * @state: state in dfa
183 * @cond: conditions to consider (NOT NULL)
184 *
185 * TODO: convert from dfa + state to permission entry, do computation conversion
186 * at load time.
187 *
188 * Returns: computed permission set
189 */
190static struct file_perms compute_perms(struct aa_dfa *dfa, unsigned int state,
191 struct path_cond *cond)
192{
193 struct file_perms perms;
194
195 /* FIXME: change over to new dfa format
196 * currently file perms are encoded in the dfa, new format
197 * splits the permissions from the dfa. This mapping can be
198 * done at profile load
199 */
200 perms.kill = 0;
201
202 if (current_fsuid() == cond->uid) {
203 perms.allow = map_old_perms(dfa_user_allow(dfa, state));
204 perms.audit = map_old_perms(dfa_user_audit(dfa, state));
205 perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
206 perms.xindex = dfa_user_xindex(dfa, state);
207 } else {
208 perms.allow = map_old_perms(dfa_other_allow(dfa, state));
209 perms.audit = map_old_perms(dfa_other_audit(dfa, state));
210 perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
211 perms.xindex = dfa_other_xindex(dfa, state);
212 }
John Johansen38305a42012-02-22 00:42:08 -0800213 perms.allow |= AA_MAY_META_READ;
John Johansen6380bd82010-07-29 14:48:04 -0700214
215 /* change_profile wasn't determined by ownership in old mapping */
216 if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
217 perms.allow |= AA_MAY_CHANGE_PROFILE;
John Johansen0421ea92012-03-27 04:14:33 -0700218 if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
219 perms.allow |= AA_MAY_ONEXEC;
John Johansen6380bd82010-07-29 14:48:04 -0700220
221 return perms;
222}
223
224/**
225 * aa_str_perms - find permission that match @name
226 * @dfa: to match against (MAYBE NULL)
227 * @state: state to start matching in
228 * @name: string to match against dfa (NOT NULL)
229 * @cond: conditions to consider for permission set computation (NOT NULL)
230 * @perms: Returns - the permissions found when matching @name
231 *
232 * Returns: the final state in @dfa when beginning @start and walking @name
233 */
234unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
235 const char *name, struct path_cond *cond,
236 struct file_perms *perms)
237{
238 unsigned int state;
239 if (!dfa) {
240 *perms = nullperms;
241 return DFA_NOMATCH;
242 }
243
244 state = aa_dfa_match(dfa, start, name);
245 *perms = compute_perms(dfa, state, cond);
246
247 return state;
248}
249
250/**
251 * is_deleted - test if a file has been completely unlinked
252 * @dentry: dentry of file to test for deletion (NOT NULL)
253 *
254 * Returns: %1 if deleted else %0
255 */
256static inline bool is_deleted(struct dentry *dentry)
257{
258 if (d_unlinked(dentry) && dentry->d_inode->i_nlink == 0)
259 return 1;
260 return 0;
261}
262
263/**
264 * aa_path_perm - do permissions check & audit for @path
265 * @op: operation being checked
266 * @profile: profile being enforced (NOT NULL)
267 * @path: path to check permissions of (NOT NULL)
268 * @flags: any additional path flags beyond what the profile specifies
269 * @request: requested permissions
270 * @cond: conditional info for this request (NOT NULL)
271 *
272 * Returns: %0 else error if access denied or other error
273 */
274int aa_path_perm(int op, struct aa_profile *profile, struct path *path,
275 int flags, u32 request, struct path_cond *cond)
276{
277 char *buffer = NULL;
278 struct file_perms perms = {};
279 const char *name, *info = NULL;
280 int error;
281
282 flags |= profile->path_flags | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0);
John Johansen57fa1e12012-02-16 06:20:33 -0800283 error = aa_path_name(path, flags, &buffer, &name, &info);
John Johansen6380bd82010-07-29 14:48:04 -0700284 if (error) {
285 if (error == -ENOENT && is_deleted(path->dentry)) {
286 /* Access to open files that are deleted are
287 * give a pass (implicit delegation)
288 */
289 error = 0;
John Johansen57fa1e12012-02-16 06:20:33 -0800290 info = NULL;
John Johansen6380bd82010-07-29 14:48:04 -0700291 perms.allow = request;
John Johansen57fa1e12012-02-16 06:20:33 -0800292 }
John Johansen6380bd82010-07-29 14:48:04 -0700293 } else {
294 aa_str_perms(profile->file.dfa, profile->file.start, name, cond,
295 &perms);
296 if (request & ~perms.allow)
297 error = -EACCES;
298 }
299 error = aa_audit_file(profile, &perms, GFP_KERNEL, op, request, name,
300 NULL, cond->uid, info, error);
301 kfree(buffer);
302
303 return error;
304}
305
306/**
307 * xindex_is_subset - helper for aa_path_link
308 * @link: link permission set
309 * @target: target permission set
310 *
311 * test target x permissions are equal OR a subset of link x permissions
312 * this is done as part of the subset test, where a hardlink must have
313 * a subset of permissions that the target has.
314 *
315 * Returns: %1 if subset else %0
316 */
317static inline bool xindex_is_subset(u32 link, u32 target)
318{
319 if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
320 ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
321 return 0;
322
323 return 1;
324}
325
326/**
327 * aa_path_link - Handle hard link permission check
328 * @profile: the profile being enforced (NOT NULL)
329 * @old_dentry: the target dentry (NOT NULL)
330 * @new_dir: directory the new link will be created in (NOT NULL)
331 * @new_dentry: the link being created (NOT NULL)
332 *
333 * Handle the permission test for a link & target pair. Permission
334 * is encoded as a pair where the link permission is determined
335 * first, and if allowed, the target is tested. The target test
336 * is done from the point of the link match (not start of DFA)
337 * making the target permission dependent on the link permission match.
338 *
339 * The subset test if required forces that permissions granted
340 * on link are a subset of the permission granted to target.
341 *
342 * Returns: %0 if allowed else error
343 */
344int aa_path_link(struct aa_profile *profile, struct dentry *old_dentry,
345 struct path *new_dir, struct dentry *new_dentry)
346{
347 struct path link = { new_dir->mnt, new_dentry };
348 struct path target = { new_dir->mnt, old_dentry };
349 struct path_cond cond = {
350 old_dentry->d_inode->i_uid,
351 old_dentry->d_inode->i_mode
352 };
353 char *buffer = NULL, *buffer2 = NULL;
354 const char *lname, *tname = NULL, *info = NULL;
355 struct file_perms lperms, perms;
356 u32 request = AA_MAY_LINK;
357 unsigned int state;
358 int error;
359
360 lperms = nullperms;
361
362 /* buffer freed below, lname is pointer in buffer */
John Johansen57fa1e12012-02-16 06:20:33 -0800363 error = aa_path_name(&link, profile->path_flags, &buffer, &lname,
364 &info);
John Johansen6380bd82010-07-29 14:48:04 -0700365 if (error)
366 goto audit;
367
368 /* buffer2 freed below, tname is pointer in buffer2 */
John Johansen57fa1e12012-02-16 06:20:33 -0800369 error = aa_path_name(&target, profile->path_flags, &buffer2, &tname,
370 &info);
John Johansen6380bd82010-07-29 14:48:04 -0700371 if (error)
372 goto audit;
373
374 error = -EACCES;
375 /* aa_str_perms - handles the case of the dfa being NULL */
376 state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
377 &cond, &lperms);
378
379 if (!(lperms.allow & AA_MAY_LINK))
380 goto audit;
381
382 /* test to see if target can be paired with link */
383 state = aa_dfa_null_transition(profile->file.dfa, state);
384 aa_str_perms(profile->file.dfa, state, tname, &cond, &perms);
385
386 /* force audit/quiet masks for link are stored in the second entry
387 * in the link pair.
388 */
389 lperms.audit = perms.audit;
390 lperms.quiet = perms.quiet;
391 lperms.kill = perms.kill;
392
393 if (!(perms.allow & AA_MAY_LINK)) {
394 info = "target restricted";
395 goto audit;
396 }
397
398 /* done if link subset test is not required */
399 if (!(perms.allow & AA_LINK_SUBSET))
400 goto done_tests;
401
402 /* Do link perm subset test requiring allowed permission on link are a
403 * subset of the allowed permissions on target.
404 */
405 aa_str_perms(profile->file.dfa, profile->file.start, tname, &cond,
406 &perms);
407
408 /* AA_MAY_LINK is not considered in the subset test */
409 request = lperms.allow & ~AA_MAY_LINK;
410 lperms.allow &= perms.allow | AA_MAY_LINK;
411
412 request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
413 if (request & ~lperms.allow) {
414 goto audit;
415 } else if ((lperms.allow & MAY_EXEC) &&
416 !xindex_is_subset(lperms.xindex, perms.xindex)) {
417 lperms.allow &= ~MAY_EXEC;
418 request |= MAY_EXEC;
419 info = "link not subset of target";
420 goto audit;
421 }
422
423done_tests:
424 error = 0;
425
426audit:
427 error = aa_audit_file(profile, &lperms, GFP_KERNEL, OP_LINK, request,
428 lname, tname, cond.uid, info, error);
429 kfree(buffer);
430 kfree(buffer2);
431
432 return error;
433}
434
435/**
436 * aa_file_perm - do permission revalidation check & audit for @file
437 * @op: operation being checked
438 * @profile: profile being enforced (NOT NULL)
439 * @file: file to revalidate access permissions on (NOT NULL)
440 * @request: requested permissions
441 *
442 * Returns: %0 if access allowed else error
443 */
444int aa_file_perm(int op, struct aa_profile *profile, struct file *file,
445 u32 request)
446{
447 struct path_cond cond = {
448 .uid = file->f_path.dentry->d_inode->i_uid,
449 .mode = file->f_path.dentry->d_inode->i_mode
450 };
451
452 return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED,
453 request, &cond);
454}