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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 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
176 new |= AA_MAY_META_READ;
177
178 return new;
179}
180
181/**
182 * compute_perms - convert dfa compressed perms to internal perms
183 * @dfa: dfa to compute perms for (NOT NULL)
184 * @state: state in dfa
185 * @cond: conditions to consider (NOT NULL)
186 *
187 * TODO: convert from dfa + state to permission entry, do computation conversion
188 * at load time.
189 *
190 * Returns: computed permission set
191 */
192static struct file_perms compute_perms(struct aa_dfa *dfa, unsigned int state,
193 struct path_cond *cond)
194{
195 struct file_perms perms;
196
197 /* FIXME: change over to new dfa format
198 * currently file perms are encoded in the dfa, new format
199 * splits the permissions from the dfa. This mapping can be
200 * done at profile load
201 */
202 perms.kill = 0;
203
204 if (current_fsuid() == cond->uid) {
205 perms.allow = map_old_perms(dfa_user_allow(dfa, state));
206 perms.audit = map_old_perms(dfa_user_audit(dfa, state));
207 perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
208 perms.xindex = dfa_user_xindex(dfa, state);
209 } else {
210 perms.allow = map_old_perms(dfa_other_allow(dfa, state));
211 perms.audit = map_old_perms(dfa_other_audit(dfa, state));
212 perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
213 perms.xindex = dfa_other_xindex(dfa, state);
214 }
215
216 /* change_profile wasn't determined by ownership in old mapping */
217 if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
218 perms.allow |= AA_MAY_CHANGE_PROFILE;
219
220 return perms;
221}
222
223/**
224 * aa_str_perms - find permission that match @name
225 * @dfa: to match against (MAYBE NULL)
226 * @state: state to start matching in
227 * @name: string to match against dfa (NOT NULL)
228 * @cond: conditions to consider for permission set computation (NOT NULL)
229 * @perms: Returns - the permissions found when matching @name
230 *
231 * Returns: the final state in @dfa when beginning @start and walking @name
232 */
233unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
234 const char *name, struct path_cond *cond,
235 struct file_perms *perms)
236{
237 unsigned int state;
238 if (!dfa) {
239 *perms = nullperms;
240 return DFA_NOMATCH;
241 }
242
243 state = aa_dfa_match(dfa, start, name);
244 *perms = compute_perms(dfa, state, cond);
245
246 return state;
247}
248
249/**
250 * is_deleted - test if a file has been completely unlinked
251 * @dentry: dentry of file to test for deletion (NOT NULL)
252 *
253 * Returns: %1 if deleted else %0
254 */
255static inline bool is_deleted(struct dentry *dentry)
256{
257 if (d_unlinked(dentry) && dentry->d_inode->i_nlink == 0)
258 return 1;
259 return 0;
260}
261
262/**
263 * aa_path_perm - do permissions check & audit for @path
264 * @op: operation being checked
265 * @profile: profile being enforced (NOT NULL)
266 * @path: path to check permissions of (NOT NULL)
267 * @flags: any additional path flags beyond what the profile specifies
268 * @request: requested permissions
269 * @cond: conditional info for this request (NOT NULL)
270 *
271 * Returns: %0 else error if access denied or other error
272 */
273int aa_path_perm(int op, struct aa_profile *profile, struct path *path,
274 int flags, u32 request, struct path_cond *cond)
275{
276 char *buffer = NULL;
277 struct file_perms perms = {};
278 const char *name, *info = NULL;
279 int error;
280
281 flags |= profile->path_flags | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0);
282 error = aa_get_name(path, flags, &buffer, &name);
283 if (error) {
284 if (error == -ENOENT && is_deleted(path->dentry)) {
285 /* Access to open files that are deleted are
286 * give a pass (implicit delegation)
287 */
288 error = 0;
289 perms.allow = request;
290 } else if (error == -ENOENT)
291 info = "Failed name lookup - deleted entry";
292 else if (error == -ESTALE)
293 info = "Failed name lookup - disconnected path";
294 else if (error == -ENAMETOOLONG)
295 info = "Failed name lookup - name too long";
296 else
297 info = "Failed name lookup";
298 } else {
299 aa_str_perms(profile->file.dfa, profile->file.start, name, cond,
300 &perms);
301 if (request & ~perms.allow)
302 error = -EACCES;
303 }
304 error = aa_audit_file(profile, &perms, GFP_KERNEL, op, request, name,
305 NULL, cond->uid, info, error);
306 kfree(buffer);
307
308 return error;
309}
310
311/**
312 * xindex_is_subset - helper for aa_path_link
313 * @link: link permission set
314 * @target: target permission set
315 *
316 * test target x permissions are equal OR a subset of link x permissions
317 * this is done as part of the subset test, where a hardlink must have
318 * a subset of permissions that the target has.
319 *
320 * Returns: %1 if subset else %0
321 */
322static inline bool xindex_is_subset(u32 link, u32 target)
323{
324 if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
325 ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
326 return 0;
327
328 return 1;
329}
330
331/**
332 * aa_path_link - Handle hard link permission check
333 * @profile: the profile being enforced (NOT NULL)
334 * @old_dentry: the target dentry (NOT NULL)
335 * @new_dir: directory the new link will be created in (NOT NULL)
336 * @new_dentry: the link being created (NOT NULL)
337 *
338 * Handle the permission test for a link & target pair. Permission
339 * is encoded as a pair where the link permission is determined
340 * first, and if allowed, the target is tested. The target test
341 * is done from the point of the link match (not start of DFA)
342 * making the target permission dependent on the link permission match.
343 *
344 * The subset test if required forces that permissions granted
345 * on link are a subset of the permission granted to target.
346 *
347 * Returns: %0 if allowed else error
348 */
349int aa_path_link(struct aa_profile *profile, struct dentry *old_dentry,
350 struct path *new_dir, struct dentry *new_dentry)
351{
352 struct path link = { new_dir->mnt, new_dentry };
353 struct path target = { new_dir->mnt, old_dentry };
354 struct path_cond cond = {
355 old_dentry->d_inode->i_uid,
356 old_dentry->d_inode->i_mode
357 };
358 char *buffer = NULL, *buffer2 = NULL;
359 const char *lname, *tname = NULL, *info = NULL;
360 struct file_perms lperms, perms;
361 u32 request = AA_MAY_LINK;
362 unsigned int state;
363 int error;
364
365 lperms = nullperms;
366
367 /* buffer freed below, lname is pointer in buffer */
368 error = aa_get_name(&link, profile->path_flags, &buffer, &lname);
369 if (error)
370 goto audit;
371
372 /* buffer2 freed below, tname is pointer in buffer2 */
373 error = aa_get_name(&target, profile->path_flags, &buffer2, &tname);
374 if (error)
375 goto audit;
376
377 error = -EACCES;
378 /* aa_str_perms - handles the case of the dfa being NULL */
379 state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
380 &cond, &lperms);
381
382 if (!(lperms.allow & AA_MAY_LINK))
383 goto audit;
384
385 /* test to see if target can be paired with link */
386 state = aa_dfa_null_transition(profile->file.dfa, state);
387 aa_str_perms(profile->file.dfa, state, tname, &cond, &perms);
388
389 /* force audit/quiet masks for link are stored in the second entry
390 * in the link pair.
391 */
392 lperms.audit = perms.audit;
393 lperms.quiet = perms.quiet;
394 lperms.kill = perms.kill;
395
396 if (!(perms.allow & AA_MAY_LINK)) {
397 info = "target restricted";
398 goto audit;
399 }
400
401 /* done if link subset test is not required */
402 if (!(perms.allow & AA_LINK_SUBSET))
403 goto done_tests;
404
405 /* Do link perm subset test requiring allowed permission on link are a
406 * subset of the allowed permissions on target.
407 */
408 aa_str_perms(profile->file.dfa, profile->file.start, tname, &cond,
409 &perms);
410
411 /* AA_MAY_LINK is not considered in the subset test */
412 request = lperms.allow & ~AA_MAY_LINK;
413 lperms.allow &= perms.allow | AA_MAY_LINK;
414
415 request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
416 if (request & ~lperms.allow) {
417 goto audit;
418 } else if ((lperms.allow & MAY_EXEC) &&
419 !xindex_is_subset(lperms.xindex, perms.xindex)) {
420 lperms.allow &= ~MAY_EXEC;
421 request |= MAY_EXEC;
422 info = "link not subset of target";
423 goto audit;
424 }
425
426done_tests:
427 error = 0;
428
429audit:
430 error = aa_audit_file(profile, &lperms, GFP_KERNEL, OP_LINK, request,
431 lname, tname, cond.uid, info, error);
432 kfree(buffer);
433 kfree(buffer2);
434
435 return error;
436}
437
438/**
439 * aa_file_perm - do permission revalidation check & audit for @file
440 * @op: operation being checked
441 * @profile: profile being enforced (NOT NULL)
442 * @file: file to revalidate access permissions on (NOT NULL)
443 * @request: requested permissions
444 *
445 * Returns: %0 if access allowed else error
446 */
447int aa_file_perm(int op, struct aa_profile *profile, struct file *file,
448 u32 request)
449{
450 struct path_cond cond = {
451 .uid = file->f_path.dentry->d_inode->i_uid,
452 .mode = file->f_path.dentry->d_inode->i_mode
453 };
454
455 return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED,
456 request, &cond);
457}
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) && 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 */
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 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
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}