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 
31 MODULE_LICENSE("GPL");
32 
33 struct 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 
42 struct nfsacl_simple_acl {
43 	struct posix_acl acl;
44 	struct posix_acl_entry ace[4];
45 };
46 
47 static int
xdr_nfsace_encode(struct xdr_array2_desc * desc,void * elem)48 xdr_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  */
nfsacl_encode(struct xdr_buf * buf,unsigned int base,struct inode * inode,struct posix_acl * acl,int encode_entries,int typeflag)91 int 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 }
136 EXPORT_SYMBOL_GPL(nfsacl_encode);
137 
138 struct nfsacl_decode_desc {
139 	struct xdr_array2_desc desc;
140 	unsigned int count;
141 	struct posix_acl *acl;
142 };
143 
144 static int
xdr_nfsace_decode(struct xdr_array2_desc * desc,void * elem)145 xdr_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 
195 static int
cmp_acl_entry(const void * x,const void * y)196 cmp_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  */
217 static int
posix_acl_from_nfsacl(struct posix_acl * acl)218 posix_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  */
nfsacl_decode(struct xdr_buf * buf,unsigned int base,unsigned int * aclcnt,struct posix_acl ** pacl)264 int 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 }
296 EXPORT_SYMBOL_GPL(nfsacl_decode);
297