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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_TASK;
114 sa.u.tsk = NULL;
115 sa.aad = &aad;
116 aad.op = op,
117 aad.fs.request = request;
118 aad.name = name;
119 aad.fs.target = target;
120 aad.fs.ouid = ouid;
121 aad.info = info;
122 aad.error = error;
123
124 if (likely(!sa.aad->error)) {
125 u32 mask = perms->audit;
126
127 if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
128 mask = 0xffff;
129
130 /* mask off perms that are not being force audited */
131 sa.aad->fs.request &= mask;
132
133 if (likely(!sa.aad->fs.request))
134 return 0;
135 type = AUDIT_APPARMOR_AUDIT;
136 } else {
137 /* only report permissions that were denied */
138 sa.aad->fs.request = sa.aad->fs.request & ~perms->allow;
139
140 if (sa.aad->fs.request & perms->kill)
141 type = AUDIT_APPARMOR_KILL;
142
143 /* quiet known rejects, assumes quiet and kill do not overlap */
144 if ((sa.aad->fs.request & perms->quiet) &&
145 AUDIT_MODE(profile) != AUDIT_NOQUIET &&
146 AUDIT_MODE(profile) != AUDIT_ALL)
147 sa.aad->fs.request &= ~perms->quiet;
148
149 if (!sa.aad->fs.request)
150 return COMPLAIN_MODE(profile) ? 0 : sa.aad->error;
151 }
152
153 sa.aad->fs.denied = sa.aad->fs.request & ~perms->allow;
154 return aa_audit(type, profile, gfp, &sa, file_audit_cb);
155}
156
157/**
158 * map_old_perms - map old file perms layout to the new layout
159 * @old: permission set in old mapping
160 *
161 * Returns: new permission mapping
162 */
163static u32 map_old_perms(u32 old)
164{
165 u32 new = old & 0xf;
166 if (old & MAY_READ)
167 new |= AA_MAY_META_READ;
168 if (old & MAY_WRITE)
169 new |= AA_MAY_META_WRITE | AA_MAY_CREATE | AA_MAY_DELETE |
170 AA_MAY_CHMOD | AA_MAY_CHOWN;
171 if (old & 0x10)
172 new |= AA_MAY_LINK;
173 /* the old mapping lock and link_subset flags where overlaid
174 * and use was determined by part of a pair that they were in
175 */
176 if (old & 0x20)
177 new |= AA_MAY_LOCK | AA_LINK_SUBSET;
178 if (old & 0x40) /* AA_EXEC_MMAP */
179 new |= AA_EXEC_MMAP;
180
181 return new;
182}
183
184/**
185 * compute_perms - convert dfa compressed perms to internal perms
186 * @dfa: dfa to compute perms for (NOT NULL)
187 * @state: state in dfa
188 * @cond: conditions to consider (NOT NULL)
189 *
190 * TODO: convert from dfa + state to permission entry, do computation conversion
191 * at load time.
192 *
193 * Returns: computed permission set
194 */
195static struct file_perms compute_perms(struct aa_dfa *dfa, unsigned int state,
196 struct path_cond *cond)
197{
198 struct file_perms perms;
199
200 /* FIXME: change over to new dfa format
201 * currently file perms are encoded in the dfa, new format
202 * splits the permissions from the dfa. This mapping can be
203 * done at profile load
204 */
205 perms.kill = 0;
206
207 if (uid_eq(current_fsuid(), cond->uid)) {
208 perms.allow = map_old_perms(dfa_user_allow(dfa, state));
209 perms.audit = map_old_perms(dfa_user_audit(dfa, state));
210 perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
211 perms.xindex = dfa_user_xindex(dfa, state);
212 } else {
213 perms.allow = map_old_perms(dfa_other_allow(dfa, state));
214 perms.audit = map_old_perms(dfa_other_audit(dfa, state));
215 perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
216 perms.xindex = dfa_other_xindex(dfa, state);
217 }
218 perms.allow |= AA_MAY_META_READ;
219
220 /* change_profile wasn't determined by ownership in old mapping */
221 if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
222 perms.allow |= AA_MAY_CHANGE_PROFILE;
223 if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
224 perms.allow |= AA_MAY_ONEXEC;
225
226 return perms;
227}
228
229/**
230 * aa_str_perms - find permission that match @name
231 * @dfa: to match against (MAYBE NULL)
232 * @state: state to start matching in
233 * @name: string to match against dfa (NOT NULL)
234 * @cond: conditions to consider for permission set computation (NOT NULL)
235 * @perms: Returns - the permissions found when matching @name
236 *
237 * Returns: the final state in @dfa when beginning @start and walking @name
238 */
239unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
240 const char *name, struct path_cond *cond,
241 struct file_perms *perms)
242{
243 unsigned int state;
244 if (!dfa) {
245 *perms = nullperms;
246 return DFA_NOMATCH;
247 }
248
249 state = aa_dfa_match(dfa, start, name);
250 *perms = compute_perms(dfa, state, cond);
251
252 return state;
253}
254
255/**
256 * is_deleted - test if a file has been completely unlinked
257 * @dentry: dentry of file to test for deletion (NOT NULL)
258 *
259 * Returns: %1 if deleted else %0
260 */
261static inline bool is_deleted(struct dentry *dentry)
262{
263 if (d_unlinked(dentry) && d_backing_inode(dentry)->i_nlink == 0)
264 return 1;
265 return 0;
266}
267
268/**
269 * aa_path_perm - do permissions check & audit for @path
270 * @op: operation being checked
271 * @profile: profile being enforced (NOT NULL)
272 * @path: path to check permissions of (NOT NULL)
273 * @flags: any additional path flags beyond what the profile specifies
274 * @request: requested permissions
275 * @cond: conditional info for this request (NOT NULL)
276 *
277 * Returns: %0 else error if access denied or other error
278 */
279int aa_path_perm(int op, struct aa_profile *profile, const struct path *path,
280 int flags, u32 request, struct path_cond *cond)
281{
282 char *buffer = NULL;
283 struct file_perms perms = {};
284 const char *name, *info = NULL;
285 int error;
286
287 flags |= profile->path_flags | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0);
288 error = aa_path_name(path, flags, &buffer, &name, &info);
289 if (error) {
290 if (error == -ENOENT && is_deleted(path->dentry)) {
291 /* Access to open files that are deleted are
292 * give a pass (implicit delegation)
293 */
294 error = 0;
295 info = NULL;
296 perms.allow = request;
297 }
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 const 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 d_backing_inode(old_dentry)->i_uid,
356 d_backing_inode(old_dentry)->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_path_name(&link, profile->path_flags, &buffer, &lname,
369 &info);
370 if (error)
371 goto audit;
372
373 /* buffer2 freed below, tname is pointer in buffer2 */
374 error = aa_path_name(&target, profile->path_flags, &buffer2, &tname,
375 &info);
376 if (error)
377 goto audit;
378
379 error = -EACCES;
380 /* aa_str_perms - handles the case of the dfa being NULL */
381 state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
382 &cond, &lperms);
383
384 if (!(lperms.allow & AA_MAY_LINK))
385 goto audit;
386
387 /* test to see if target can be paired with link */
388 state = aa_dfa_null_transition(profile->file.dfa, state);
389 aa_str_perms(profile->file.dfa, state, tname, &cond, &perms);
390
391 /* force audit/quiet masks for link are stored in the second entry
392 * in the link pair.
393 */
394 lperms.audit = perms.audit;
395 lperms.quiet = perms.quiet;
396 lperms.kill = perms.kill;
397
398 if (!(perms.allow & AA_MAY_LINK)) {
399 info = "target restricted";
400 goto audit;
401 }
402
403 /* done if link subset test is not required */
404 if (!(perms.allow & AA_LINK_SUBSET))
405 goto done_tests;
406
407 /* Do link perm subset test requiring allowed permission on link are a
408 * subset of the allowed permissions on target.
409 */
410 aa_str_perms(profile->file.dfa, profile->file.start, tname, &cond,
411 &perms);
412
413 /* AA_MAY_LINK is not considered in the subset test */
414 request = lperms.allow & ~AA_MAY_LINK;
415 lperms.allow &= perms.allow | AA_MAY_LINK;
416
417 request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
418 if (request & ~lperms.allow) {
419 goto audit;
420 } else if ((lperms.allow & MAY_EXEC) &&
421 !xindex_is_subset(lperms.xindex, perms.xindex)) {
422 lperms.allow &= ~MAY_EXEC;
423 request |= MAY_EXEC;
424 info = "link not subset of target";
425 goto audit;
426 }
427
428done_tests:
429 error = 0;
430
431audit:
432 error = aa_audit_file(profile, &lperms, GFP_KERNEL, OP_LINK, request,
433 lname, tname, cond.uid, info, error);
434 kfree(buffer);
435 kfree(buffer2);
436
437 return error;
438}
439
440/**
441 * aa_file_perm - do permission revalidation check & audit for @file
442 * @op: operation being checked
443 * @profile: profile being enforced (NOT NULL)
444 * @file: file to revalidate access permissions on (NOT NULL)
445 * @request: requested permissions
446 *
447 * Returns: %0 if access allowed else error
448 */
449int aa_file_perm(int op, struct aa_profile *profile, struct file *file,
450 u32 request)
451{
452 struct path_cond cond = {
453 .uid = file_inode(file)->i_uid,
454 .mode = file_inode(file)->i_mode
455 };
456
457 return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED,
458 request, &cond);
459}