1/*
2 * fs/nfs_common/nfsacl.c
3 *
4 *  Copyright (C) 2002-2003 Andreas Gruenbacher <agruen@suse.de>
5 */
6
7/*
8 * The Solaris nfsacl protocol represents some ACLs slightly differently
9 * than POSIX 1003.1e draft 17 does (and we do):
10 *
11 *  - Minimal ACLs always have an ACL_MASK entry, so they have
12 *    four instead of three entries.
13 *  - The ACL_MASK entry in such minimal ACLs always has the same
14 *    permissions as the ACL_GROUP_OBJ entry. (In extended ACLs
15 *    the ACL_MASK and ACL_GROUP_OBJ entries may differ.)
16 *  - The identifier fields of the ACL_USER_OBJ and ACL_GROUP_OBJ
17 *    entries contain the identifiers of the owner and owning group.
18 *    (In POSIX ACLs we always set them to ACL_UNDEFINED_ID).
19 *  - ACL entries in the kernel are kept sorted in ascending order
20 *    of (e_tag, e_id). Solaris ACLs are unsorted.
21 */
22
23#include <linux/module.h>
24#include <linux/fs.h>
25#include <linux/gfp.h>
26#include <linux/sunrpc/xdr.h>
27#include <linux/nfsacl.h>
28#include <linux/nfs3.h>
29#include <linux/sort.h>
30
31MODULE_LICENSE("GPL");
32
33struct nfsacl_encode_desc {
34	struct xdr_array2_desc desc;
35	unsigned int count;
36	struct posix_acl *acl;
37	int typeflag;
38	kuid_t uid;
39	kgid_t gid;
40};
41
42struct nfsacl_simple_acl {
43	struct posix_acl acl;
44	struct posix_acl_entry ace[4];
45};
46
47static int
48xdr_nfsace_encode(struct xdr_array2_desc *desc, void *elem)
49{
50	struct nfsacl_encode_desc *nfsacl_desc =
51		(struct nfsacl_encode_desc *) desc;
52	__be32 *p = elem;
53
54	struct posix_acl_entry *entry =
55		&nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
56
57	*p++ = htonl(entry->e_tag | nfsacl_desc->typeflag);
58	switch(entry->e_tag) {
59		case ACL_USER_OBJ:
60			*p++ = htonl(from_kuid(&init_user_ns, nfsacl_desc->uid));
61			break;
62		case ACL_GROUP_OBJ:
63			*p++ = htonl(from_kgid(&init_user_ns, nfsacl_desc->gid));
64			break;
65		case ACL_USER:
66			*p++ = htonl(from_kuid(&init_user_ns, entry->e_uid));
67			break;
68		case ACL_GROUP:
69			*p++ = htonl(from_kgid(&init_user_ns, entry->e_gid));
70			break;
71		default:  /* Solaris depends on that! */
72			*p++ = 0;
73			break;
74	}
75	*p++ = htonl(entry->e_perm & S_IRWXO);
76	return 0;
77}
78
79/**
80 * nfsacl_encode - Encode an NFSv3 ACL
81 *
82 * @buf: destination xdr_buf to contain XDR encoded ACL
83 * @base: byte offset in xdr_buf where XDR'd ACL begins
84 * @inode: inode of file whose ACL this is
85 * @acl: posix_acl to encode
86 * @encode_entries: whether to encode ACEs as well
87 * @typeflag: ACL type: NFS_ACL_DEFAULT or zero
88 *
89 * Returns size of encoded ACL in bytes or a negative errno value.
90 */
91int nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
92		  struct posix_acl *acl, int encode_entries, int typeflag)
93{
94	int entries = (acl && acl->a_count) ? max_t(int, acl->a_count, 4) : 0;
95	struct nfsacl_encode_desc nfsacl_desc = {
96		.desc = {
97			.elem_size = 12,
98			.array_len = encode_entries ? entries : 0,
99			.xcode = xdr_nfsace_encode,
100		},
101		.acl = acl,
102		.typeflag = typeflag,
103		.uid = inode->i_uid,
104		.gid = inode->i_gid,
105	};
106	struct nfsacl_simple_acl aclbuf;
107	int err;
108
109	if (entries > NFS_ACL_MAX_ENTRIES ||
110	    xdr_encode_word(buf, base, entries))
111		return -EINVAL;
112	if (encode_entries && acl && acl->a_count == 3) {
113		struct posix_acl *acl2 = &aclbuf.acl;
114
115		/* Avoid the use of posix_acl_alloc().  nfsacl_encode() is
116		 * invoked in contexts where a memory allocation failure is
117		 * fatal.  Fortunately this fake ACL is small enough to
118		 * construct on the stack. */
119		posix_acl_init(acl2, 4);
120
121		/* Insert entries in canonical order: other orders seem
122		 to confuse Solaris VxFS. */
123		acl2->a_entries[0] = acl->a_entries[0];  /* ACL_USER_OBJ */
124		acl2->a_entries[1] = acl->a_entries[1];  /* ACL_GROUP_OBJ */
125		acl2->a_entries[2] = acl->a_entries[1];  /* ACL_MASK */
126		acl2->a_entries[2].e_tag = ACL_MASK;
127		acl2->a_entries[3] = acl->a_entries[2];  /* ACL_OTHER */
128		nfsacl_desc.acl = acl2;
129	}
130	err = xdr_encode_array2(buf, base + 4, &nfsacl_desc.desc);
131	if (!err)
132		err = 8 + nfsacl_desc.desc.elem_size *
133			  nfsacl_desc.desc.array_len;
134	return err;
135}
136EXPORT_SYMBOL_GPL(nfsacl_encode);
137
138struct nfsacl_decode_desc {
139	struct xdr_array2_desc desc;
140	unsigned int count;
141	struct posix_acl *acl;
142};
143
144static int
145xdr_nfsace_decode(struct xdr_array2_desc *desc, void *elem)
146{
147	struct nfsacl_decode_desc *nfsacl_desc =
148		(struct nfsacl_decode_desc *) desc;
149	__be32 *p = elem;
150	struct posix_acl_entry *entry;
151	unsigned int id;
152
153	if (!nfsacl_desc->acl) {
154		if (desc->array_len > NFS_ACL_MAX_ENTRIES)
155			return -EINVAL;
156		nfsacl_desc->acl = posix_acl_alloc(desc->array_len, GFP_KERNEL);
157		if (!nfsacl_desc->acl)
158			return -ENOMEM;
159		nfsacl_desc->count = 0;
160	}
161
162	entry = &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
163	entry->e_tag = ntohl(*p++) & ~NFS_ACL_DEFAULT;
164	id = ntohl(*p++);
165	entry->e_perm = ntohl(*p++);
166
167	switch(entry->e_tag) {
168		case ACL_USER:
169			entry->e_uid = make_kuid(&init_user_ns, id);
170			if (!uid_valid(entry->e_uid))
171				return -EINVAL;
172			break;
173		case ACL_GROUP:
174			entry->e_gid = make_kgid(&init_user_ns, id);
175			if (!gid_valid(entry->e_gid))
176				return -EINVAL;
177			break;
178		case ACL_USER_OBJ:
179		case ACL_GROUP_OBJ:
180		case ACL_OTHER:
181			if (entry->e_perm & ~S_IRWXO)
182				return -EINVAL;
183			break;
184		case ACL_MASK:
185			/* Solaris sometimes sets additional bits in the mask */
186			entry->e_perm &= S_IRWXO;
187			break;
188		default:
189			return -EINVAL;
190	}
191
192	return 0;
193}
194
195static int
196cmp_acl_entry(const void *x, const void *y)
197{
198	const struct posix_acl_entry *a = x, *b = y;
199
200	if (a->e_tag != b->e_tag)
201		return a->e_tag - b->e_tag;
202	else if ((a->e_tag == ACL_USER) && uid_gt(a->e_uid, b->e_uid))
203		return 1;
204	else if ((a->e_tag == ACL_USER) && uid_lt(a->e_uid, b->e_uid))
205		return -1;
206	else if ((a->e_tag == ACL_GROUP) && gid_gt(a->e_gid, b->e_gid))
207		return 1;
208	else if ((a->e_tag == ACL_GROUP) && gid_lt(a->e_gid, b->e_gid))
209		return -1;
210	else
211		return 0;
212}
213
214/*
215 * Convert from a Solaris ACL to a POSIX 1003.1e draft 17 ACL.
216 */
217static int
218posix_acl_from_nfsacl(struct posix_acl *acl)
219{
220	struct posix_acl_entry *pa, *pe,
221	       *group_obj = NULL, *mask = NULL;
222
223	if (!acl)
224		return 0;
225
226	sort(acl->a_entries, acl->a_count, sizeof(struct posix_acl_entry),
227	     cmp_acl_entry, NULL);
228
229	/* Find the ACL_GROUP_OBJ and ACL_MASK entries. */
230	FOREACH_ACL_ENTRY(pa, acl, pe) {
231		switch(pa->e_tag) {
232			case ACL_USER_OBJ:
233				break;
234			case ACL_GROUP_OBJ:
235				group_obj = pa;
236				break;
237			case ACL_MASK:
238				mask = pa;
239				/* fall through */
240			case ACL_OTHER:
241				break;
242		}
243	}
244	if (acl->a_count == 4 && group_obj && mask &&
245	    mask->e_perm == group_obj->e_perm) {
246		/* remove bogus ACL_MASK entry */
247		memmove(mask, mask+1, (3 - (mask - acl->a_entries)) *
248				      sizeof(struct posix_acl_entry));
249		acl->a_count = 3;
250	}
251	return 0;
252}
253
254/**
255 * nfsacl_decode - Decode an NFSv3 ACL
256 *
257 * @buf: xdr_buf containing XDR'd ACL data to decode
258 * @base: byte offset in xdr_buf where XDR'd ACL begins
259 * @aclcnt: count of ACEs in decoded posix_acl
260 * @pacl: buffer in which to place decoded posix_acl
261 *
262 * Returns the length of the decoded ACL in bytes, or a negative errno value.
263 */
264int nfsacl_decode(struct xdr_buf *buf, unsigned int base, unsigned int *aclcnt,
265		  struct posix_acl **pacl)
266{
267	struct nfsacl_decode_desc nfsacl_desc = {
268		.desc = {
269			.elem_size = 12,
270			.xcode = pacl ? xdr_nfsace_decode : NULL,
271		},
272	};
273	u32 entries;
274	int err;
275
276	if (xdr_decode_word(buf, base, &entries) ||
277	    entries > NFS_ACL_MAX_ENTRIES)
278		return -EINVAL;
279	nfsacl_desc.desc.array_maxlen = entries;
280	err = xdr_decode_array2(buf, base + 4, &nfsacl_desc.desc);
281	if (err)
282		return err;
283	if (pacl) {
284		if (entries != nfsacl_desc.desc.array_len ||
285		    posix_acl_from_nfsacl(nfsacl_desc.acl) != 0) {
286			posix_acl_release(nfsacl_desc.acl);
287			return -EINVAL;
288		}
289		*pacl = nfsacl_desc.acl;
290	}
291	if (aclcnt)
292		*aclcnt = entries;
293	return 8 + nfsacl_desc.desc.elem_size *
294		   nfsacl_desc.desc.array_len;
295}
296EXPORT_SYMBOL_GPL(nfsacl_decode);
297