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
22 struct 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 */
audit_file_mask(struct audit_buffer * ab,u32 mask)30 static 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 */
file_audit_cb(struct audit_buffer * ab,void * va)65 static 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 */
aa_audit_file(struct aa_profile * profile,struct file_perms * perms,gfp_t gfp,int op,u32 request,const char * name,const char * target,kuid_t ouid,const char * info,int error)106 int 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 */
map_old_perms(u32 old)162 static 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 */
compute_perms(struct aa_dfa * dfa,unsigned int state,struct path_cond * cond)194 static 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 */
aa_str_perms(struct aa_dfa * dfa,unsigned int start,const char * name,struct path_cond * cond,struct file_perms * perms)238 unsigned 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 */
is_deleted(struct dentry * dentry)260 static inline bool is_deleted(struct dentry *dentry)
261 {
262 if (d_unlinked(dentry) && dentry->d_inode->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 */
aa_path_perm(int op,struct aa_profile * profile,struct path * path,int flags,u32 request,struct path_cond * cond)278 int 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 */
xindex_is_subset(u32 link,u32 target)321 static 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 */
aa_path_link(struct aa_profile * profile,struct dentry * old_dentry,struct path * new_dir,struct dentry * new_dentry)348 int 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 old_dentry->d_inode->i_uid,
355 old_dentry->d_inode->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
427 done_tests:
428 error = 0;
429
430 audit:
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 */
aa_file_perm(int op,struct aa_profile * profile,struct file * file,u32 request)448 int 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