1/*
2 * linux/fs/posix_acl.c
3 *
4 *  Copyright (C) 2002 by Andreas Gruenbacher <a.gruenbacher@computer.org>
5 *
6 *  Fixes from William Schumacher incorporated on 15 March 2001.
7 *     (Reported by Charles Bertsch, <CBertsch@microtest.com>).
8 */
9
10/*
11 *  This file contains generic functions for manipulating
12 *  POSIX 1003.1e draft standard 17 ACLs.
13 */
14
15#include <linux/kernel.h>
16#include <linux/slab.h>
17#include <asm/atomic.h>
18#include <linux/fs.h>
19#include <linux/sched.h>
20#include <linux/posix_acl.h>
21#include <linux/module.h>
22
23#include <linux/errno.h>
24
25EXPORT_SYMBOL(posix_acl_alloc);
26EXPORT_SYMBOL(posix_acl_clone);
27EXPORT_SYMBOL(posix_acl_valid);
28EXPORT_SYMBOL(posix_acl_equiv_mode);
29EXPORT_SYMBOL(posix_acl_from_mode);
30EXPORT_SYMBOL(posix_acl_create_masq);
31EXPORT_SYMBOL(posix_acl_chmod_masq);
32EXPORT_SYMBOL(posix_acl_permission);
33
34/*
35 * Allocate a new ACL with the specified number of entries.
36 */
37struct posix_acl *
38posix_acl_alloc(int count, gfp_t flags)
39{
40	const size_t size = sizeof(struct posix_acl) +
41	                    count * sizeof(struct posix_acl_entry);
42	struct posix_acl *acl = kmalloc(size, flags);
43	if (acl) {
44		atomic_set(&acl->a_refcount, 1);
45		acl->a_count = count;
46	}
47	return acl;
48}
49
50/*
51 * Clone an ACL.
52 */
53struct posix_acl *
54posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
55{
56	struct posix_acl *clone = NULL;
57
58	if (acl) {
59		int size = sizeof(struct posix_acl) + acl->a_count *
60		           sizeof(struct posix_acl_entry);
61		clone = kmemdup(acl, size, flags);
62		if (clone)
63			atomic_set(&clone->a_refcount, 1);
64	}
65	return clone;
66}
67
68/*
69 * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
70 */
71int
72posix_acl_valid(const struct posix_acl *acl)
73{
74	const struct posix_acl_entry *pa, *pe;
75	int state = ACL_USER_OBJ;
76	unsigned int id = 0;  /* keep gcc happy */
77	int needs_mask = 0;
78
79	FOREACH_ACL_ENTRY(pa, acl, pe) {
80		if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
81			return -EINVAL;
82		switch (pa->e_tag) {
83			case ACL_USER_OBJ:
84				if (state == ACL_USER_OBJ) {
85					id = 0;
86					state = ACL_USER;
87					break;
88				}
89				return -EINVAL;
90
91			case ACL_USER:
92				if (state != ACL_USER)
93					return -EINVAL;
94				if (pa->e_id == ACL_UNDEFINED_ID ||
95				    pa->e_id < id)
96					return -EINVAL;
97				id = pa->e_id + 1;
98				needs_mask = 1;
99				break;
100
101			case ACL_GROUP_OBJ:
102				if (state == ACL_USER) {
103					id = 0;
104					state = ACL_GROUP;
105					break;
106				}
107				return -EINVAL;
108
109			case ACL_GROUP:
110				if (state != ACL_GROUP)
111					return -EINVAL;
112				if (pa->e_id == ACL_UNDEFINED_ID ||
113				    pa->e_id < id)
114					return -EINVAL;
115				id = pa->e_id + 1;
116				needs_mask = 1;
117				break;
118
119			case ACL_MASK:
120				if (state != ACL_GROUP)
121					return -EINVAL;
122				state = ACL_OTHER;
123				break;
124
125			case ACL_OTHER:
126				if (state == ACL_OTHER ||
127				    (state == ACL_GROUP && !needs_mask)) {
128					state = 0;
129					break;
130				}
131				return -EINVAL;
132
133			default:
134				return -EINVAL;
135		}
136	}
137	if (state == 0)
138		return 0;
139	return -EINVAL;
140}
141
142/*
143 * Returns 0 if the acl can be exactly represented in the traditional
144 * file mode permission bits, or else 1. Returns -E... on error.
145 */
146int
147posix_acl_equiv_mode(const struct posix_acl *acl, mode_t *mode_p)
148{
149	const struct posix_acl_entry *pa, *pe;
150	mode_t mode = 0;
151	int not_equiv = 0;
152
153	FOREACH_ACL_ENTRY(pa, acl, pe) {
154		switch (pa->e_tag) {
155			case ACL_USER_OBJ:
156				mode |= (pa->e_perm & S_IRWXO) << 6;
157				break;
158			case ACL_GROUP_OBJ:
159				mode |= (pa->e_perm & S_IRWXO) << 3;
160				break;
161			case ACL_OTHER:
162				mode |= pa->e_perm & S_IRWXO;
163				break;
164			case ACL_MASK:
165				mode = (mode & ~S_IRWXG) |
166				       ((pa->e_perm & S_IRWXO) << 3);
167				not_equiv = 1;
168				break;
169			case ACL_USER:
170			case ACL_GROUP:
171				not_equiv = 1;
172				break;
173			default:
174				return -EINVAL;
175		}
176	}
177        if (mode_p)
178                *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
179        return not_equiv;
180}
181
182/*
183 * Create an ACL representing the file mode permission bits of an inode.
184 */
185struct posix_acl *
186posix_acl_from_mode(mode_t mode, gfp_t flags)
187{
188	struct posix_acl *acl = posix_acl_alloc(3, flags);
189	if (!acl)
190		return ERR_PTR(-ENOMEM);
191
192	acl->a_entries[0].e_tag  = ACL_USER_OBJ;
193	acl->a_entries[0].e_id   = ACL_UNDEFINED_ID;
194	acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
195
196	acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
197	acl->a_entries[1].e_id   = ACL_UNDEFINED_ID;
198	acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
199
200	acl->a_entries[2].e_tag  = ACL_OTHER;
201	acl->a_entries[2].e_id   = ACL_UNDEFINED_ID;
202	acl->a_entries[2].e_perm = (mode & S_IRWXO);
203	return acl;
204}
205
206/*
207 * Return 0 if current is granted want access to the inode
208 * by the acl. Returns -E... otherwise.
209 */
210int
211posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
212{
213	const struct posix_acl_entry *pa, *pe, *mask_obj;
214	int found = 0;
215
216	FOREACH_ACL_ENTRY(pa, acl, pe) {
217                switch(pa->e_tag) {
218                        case ACL_USER_OBJ:
219				/* (May have been checked already) */
220				if (inode->i_uid == current_fsuid())
221                                        goto check_perm;
222                                break;
223                        case ACL_USER:
224				if (pa->e_id == current_fsuid())
225                                        goto mask;
226				break;
227                        case ACL_GROUP_OBJ:
228                                if (in_group_p(inode->i_gid)) {
229					found = 1;
230					if ((pa->e_perm & want) == want)
231						goto mask;
232                                }
233				break;
234                        case ACL_GROUP:
235                                if (in_group_p(pa->e_id)) {
236					found = 1;
237					if ((pa->e_perm & want) == want)
238						goto mask;
239                                }
240                                break;
241                        case ACL_MASK:
242                                break;
243                        case ACL_OTHER:
244				if (found)
245					return -EACCES;
246				else
247					goto check_perm;
248			default:
249				return -EIO;
250                }
251        }
252	return -EIO;
253
254mask:
255	for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
256		if (mask_obj->e_tag == ACL_MASK) {
257			if ((pa->e_perm & mask_obj->e_perm & want) == want)
258				return 0;
259			return -EACCES;
260		}
261	}
262
263check_perm:
264	if ((pa->e_perm & want) == want)
265		return 0;
266	return -EACCES;
267}
268
269/*
270 * Modify acl when creating a new inode. The caller must ensure the acl is
271 * only referenced once.
272 *
273 * mode_p initially must contain the mode parameter to the open() / creat()
274 * system calls. All permissions that are not granted by the acl are removed.
275 * The permissions in the acl are changed to reflect the mode_p parameter.
276 */
277int
278posix_acl_create_masq(struct posix_acl *acl, mode_t *mode_p)
279{
280	struct posix_acl_entry *pa, *pe;
281	struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
282	mode_t mode = *mode_p;
283	int not_equiv = 0;
284
285	/* assert(atomic_read(acl->a_refcount) == 1); */
286
287	FOREACH_ACL_ENTRY(pa, acl, pe) {
288                switch(pa->e_tag) {
289                        case ACL_USER_OBJ:
290				pa->e_perm &= (mode >> 6) | ~S_IRWXO;
291				mode &= (pa->e_perm << 6) | ~S_IRWXU;
292				break;
293
294			case ACL_USER:
295			case ACL_GROUP:
296				not_equiv = 1;
297				break;
298
299                        case ACL_GROUP_OBJ:
300				group_obj = pa;
301                                break;
302
303                        case ACL_OTHER:
304				pa->e_perm &= mode | ~S_IRWXO;
305				mode &= pa->e_perm | ~S_IRWXO;
306                                break;
307
308                        case ACL_MASK:
309				mask_obj = pa;
310				not_equiv = 1;
311                                break;
312
313			default:
314				return -EIO;
315                }
316        }
317
318	if (mask_obj) {
319		mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
320		mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
321	} else {
322		if (!group_obj)
323			return -EIO;
324		group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
325		mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
326	}
327
328	*mode_p = (*mode_p & ~S_IRWXUGO) | mode;
329        return not_equiv;
330}
331
332/*
333 * Modify the ACL for the chmod syscall.
334 */
335int
336posix_acl_chmod_masq(struct posix_acl *acl, mode_t mode)
337{
338	struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
339	struct posix_acl_entry *pa, *pe;
340
341	/* assert(atomic_read(acl->a_refcount) == 1); */
342
343	FOREACH_ACL_ENTRY(pa, acl, pe) {
344		switch(pa->e_tag) {
345			case ACL_USER_OBJ:
346				pa->e_perm = (mode & S_IRWXU) >> 6;
347				break;
348
349			case ACL_USER:
350			case ACL_GROUP:
351				break;
352
353			case ACL_GROUP_OBJ:
354				group_obj = pa;
355				break;
356
357			case ACL_MASK:
358				mask_obj = pa;
359				break;
360
361			case ACL_OTHER:
362				pa->e_perm = (mode & S_IRWXO);
363				break;
364
365			default:
366				return -EIO;
367		}
368	}
369
370	if (mask_obj) {
371		mask_obj->e_perm = (mode & S_IRWXG) >> 3;
372	} else {
373		if (!group_obj)
374			return -EIO;
375		group_obj->e_perm = (mode & S_IRWXG) >> 3;
376	}
377
378	return 0;
379}
380