contents.c

   1 /*
   2  * Copyright (C) 2010 The Android Open Source Project
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *      http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <sys/stat.h>
  18 #include <string.h>
  19 #include <stdio.h>
  20
  21 #include <private/android_filesystem_capability.h>
  22
  23 #define XATTR_SELINUX_SUFFIX "selinux"
  24 #define XATTR_CAPS_SUFFIX "capability"
  25
  26 #include "ext4_utils.h"
  27 #include "allocate.h"
  28 #include "contents.h"
  29 #include "extent.h"
  30 #include "indirect.h"
  31
  32 static struct block_allocation* saved_allocation_head = NULL;
  33
  34 struct block_allocation* get_saved_allocation_chain() {
  35         return saved_allocation_head;
  36 }
  37
  38 static u32 dentry_size(u32 entries, struct dentry *dentries)
  39 {
  40         u32 len = 24;
  41         unsigned int i;
  42         unsigned int dentry_len;
  43
  44         for (i = 0; i < entries; i++) {
  45                 dentry_len = 8 + EXT4_ALIGN(strlen(dentries[i].filename), 4);
  46                 if (len % info.block_size + dentry_len > info.block_size)
  47                         len += info.block_size - (len % info.block_size);
  48                 len += dentry_len;
  49         }
  50
  51         return len;
  52 }
  53
  54 static struct ext4_dir_entry_2 *add_dentry(u8 *data, u32 *offset,
  55                 struct ext4_dir_entry_2 *prev, u32 inode, const char *name,
  56                 u8 file_type)
  57 {
  58         u8 name_len = strlen(name);
  59         u16 rec_len = 8 + EXT4_ALIGN(name_len, 4);
  60         struct ext4_dir_entry_2 *dentry;
  61
  62         u32 start_block = *offset / info.block_size;
  63         u32 end_block = (*offset + rec_len - 1) / info.block_size;
  64         if (start_block != end_block) {
  65                 /* Adding this dentry will cross a block boundary, so pad the previous
  66                    dentry to the block boundary */
  67                 if (!prev)
  68                         critical_error("no prev");
  69                 prev->rec_len += end_block * info.block_size - *offset;
  70                 *offset = end_block * info.block_size;
  71         }
  72
  73         dentry = (struct ext4_dir_entry_2 *)(data + *offset);
  74         dentry->inode = inode;
  75         dentry->rec_len = rec_len;
  76         dentry->name_len = name_len;
  77         dentry->file_type = file_type;
  78         memcpy(dentry->name, name, name_len);
  79
  80         *offset += rec_len;
  81         return dentry;
  82 }
  83
  84 /* Creates a directory structure for an array of directory entries, dentries,
  85    and stores the location of the structure in an inode.  The new inode's
  86    .. link is set to dir_inode_num.  Stores the location of the inode number
  87    of each directory entry into dentries[i].inode, to be filled in later
  88    when the inode for the entry is allocated.  Returns the inode number of the
  89    new directory */
  90 u32 make_directory(u32 dir_inode_num, u32 entries, struct dentry *dentries,
  91         u32 dirs)
  92 {
  93         struct ext4_inode *inode;
  94         u32 blocks;
  95         u32 len;
  96         u32 offset = 0;
  97         u32 inode_num;
  98         u8 *data;
  99         unsigned int i;
 100         struct ext4_dir_entry_2 *dentry;
 101
 102         blocks = DIV_ROUND_UP(dentry_size(entries, dentries), info.block_size);
 103         len = blocks * info.block_size;
 104
 105         if (dir_inode_num) {
 106                 inode_num = allocate_inode();
 107         } else {
 108                 dir_inode_num = EXT4_ROOT_INO;
 109                 inode_num = EXT4_ROOT_INO;
 110         }
 111
 112         if (inode_num == EXT4_ALLOCATE_FAILED) {
 113                 error("failed to allocate inode\n");
 114                 return EXT4_ALLOCATE_FAILED;
 115         }
 116
 117         add_directory(inode_num);
 118
 119         inode = get_inode(inode_num);
 120         if (inode == NULL) {
 121                 error("failed to get inode %u", inode_num);
 122                 return EXT4_ALLOCATE_FAILED;
 123         }
 124
 125         data = inode_allocate_data_extents(inode, len, len);
 126         if (data == NULL) {
 127                 error("failed to allocate %u extents", len);
 128                 return EXT4_ALLOCATE_FAILED;
 129         }
 130
 131         inode->i_mode = S_IFDIR;
 132         inode->i_links_count = dirs + 2;
 133         inode->i_flags |= aux_info.default_i_flags;
 134
 135         dentry = NULL;
 136
 137         dentry = add_dentry(data, &offset, NULL, inode_num, ".", EXT4_FT_DIR);
 138         if (!dentry) {
 139                 error("failed to add . directory");
 140                 return EXT4_ALLOCATE_FAILED;
 141         }
 142
 143         dentry = add_dentry(data, &offset, dentry, dir_inode_num, "..", EXT4_FT_DIR);
 144         if (!dentry) {
 145                 error("failed to add .. directory");
 146                 return EXT4_ALLOCATE_FAILED;
 147         }
 148
 149         for (i = 0; i < entries; i++) {
 150                 dentry = add_dentry(data, &offset, dentry, 0,
 151                                 dentries[i].filename, dentries[i].file_type);
 152                 if (offset > len || (offset == len && i != entries - 1))
 153                         critical_error("internal error: dentry for %s ends at %d, past %d\n",
 154                                 dentries[i].filename, offset, len);
 155                 dentries[i].inode = &dentry->inode;
 156                 if (!dentry) {
 157                         error("failed to add directory");
 158                         return EXT4_ALLOCATE_FAILED;
 159                 }
 160         }
 161
 162         /* pad the last dentry out to the end of the block */
 163         dentry->rec_len += len - offset;
 164
 165         return inode_num;
 166 }
 167
 168 /* Creates a file on disk.  Returns the inode number of the new file */
 169 u32 make_file(const char *filename, u64 len)
 170 {
 171         struct ext4_inode *inode;
 172         u32 inode_num;
 173
 174         inode_num = allocate_inode();
 175         if (inode_num == EXT4_ALLOCATE_FAILED) {
 176                 error("failed to allocate inode\n");
 177                 return EXT4_ALLOCATE_FAILED;
 178         }
 179
 180         inode = get_inode(inode_num);
 181         if (inode == NULL) {
 182                 error("failed to get inode %u", inode_num);
 183                 return EXT4_ALLOCATE_FAILED;
 184         }
 185
 186         if (len > 0) {
 187                 struct block_allocation* alloc = inode_allocate_file_extents(inode, len, filename);
 188                 if (alloc) {
 189                         alloc->filename = strdup(filename);
 190                         alloc->next = saved_allocation_head;
 191                         saved_allocation_head = alloc;
 192                 }
 193         }
 194
 195         inode->i_mode = S_IFREG;
 196         inode->i_links_count = 1;
 197         inode->i_flags |= aux_info.default_i_flags;
 198
 199         return inode_num;
 200 }
 201
 202 /* Creates a file on disk.  Returns the inode number of the new file */
 203 u32 make_link(const char *link)
 204 {
 205         struct ext4_inode *inode;
 206         u32 inode_num;
 207         u32 len = strlen(link);
 208
 209         inode_num = allocate_inode();
 210         if (inode_num == EXT4_ALLOCATE_FAILED) {
 211                 error("failed to allocate inode\n");
 212                 return EXT4_ALLOCATE_FAILED;
 213         }
 214
 215         inode = get_inode(inode_num);
 216         if (inode == NULL) {
 217                 error("failed to get inode %u", inode_num);
 218                 return EXT4_ALLOCATE_FAILED;
 219         }
 220
 221         inode->i_mode = S_IFLNK;
 222         inode->i_links_count = 1;
 223         inode->i_flags |= aux_info.default_i_flags;
 224         inode->i_size_lo = len;
 225
 226         if (len + 1 <= sizeof(inode->i_block)) {
 227                 /* Fast symlink */
 228                 memcpy((char*)inode->i_block, link, len);
 229         } else {
 230                 u8 *data = inode_allocate_data_indirect(inode, info.block_size, info.block_size);
 231                 memcpy(data, link, len);
 232                 inode->i_blocks_lo = info.block_size / 512;
 233         }
 234
 235         return inode_num;
 236 }
 237
 238 /* Creates a special file on disk.  Returns the inode number of the new file */
 239 u32 make_special(const char *path)
 240 {
 241         struct ext4_inode *inode;
 242         struct stat s;
 243         u32 inode_num;
 244
 245         if (stat(path, &s)) {
 246                 error("failed to stat file\n");
 247                 return EXT4_ALLOCATE_FAILED;
 248         }
 249
 250         inode_num = allocate_inode();
 251         if (inode_num == EXT4_ALLOCATE_FAILED) {
 252                 error("failed to allocate inode\n");
 253                 return EXT4_ALLOCATE_FAILED;
 254         }
 255
 256         inode = get_inode(inode_num);
 257         if (inode == NULL) {
 258                 error("failed to get inode %u", inode_num);
 259                 return EXT4_ALLOCATE_FAILED;
 260         }
 261
 262         inode->i_mode = s.st_mode & S_IFMT;
 263         inode->i_links_count = 1;
 264         inode->i_flags |= aux_info.default_i_flags;
 265
 266         ((u8 *)inode->i_block)[0] = major(s.st_rdev);
 267         ((u8 *)inode->i_block)[1] = minor(s.st_rdev);
 268
 269         return inode_num;
 270 }
 271
 272 int inode_set_permissions(u32 inode_num, u16 mode, u16 uid, u16 gid, u32 mtime)
 273 {
 274         struct ext4_inode *inode = get_inode(inode_num);
 275
 276         if (!inode)
 277                 return -1;
 278
 279         inode->i_mode |= mode;
 280         inode->i_uid = uid;
 281         inode->i_gid = gid;
 282         inode->i_mtime = mtime;
 283         inode->i_atime = mtime;
 284         inode->i_ctime = mtime;
 285
 286         return 0;
 287 }
 288
 289 /*
 290  * Returns the amount of free space available in the specified
 291  * xattr region
 292  */
 293 static size_t xattr_free_space(struct ext4_xattr_entry *entry, char *end)
 294 {
 295         while(!IS_LAST_ENTRY(entry) && (((char *) entry) < end)) {
 296                 end   -= EXT4_XATTR_SIZE(le32_to_cpu(entry->e_value_size));
 297                 entry  = EXT4_XATTR_NEXT(entry);
 298         }
 299
 300         if (((char *) entry) > end) {
 301                 error("unexpected read beyond end of xattr space");
 302                 return 0;
 303         }
 304
 305         return end - ((char *) entry);
 306 }
 307
 308 /*
 309  * Returns a pointer to the free space immediately after the
 310  * last xattr element
 311  */
 312 static struct ext4_xattr_entry* xattr_get_last(struct ext4_xattr_entry *entry)
 313 {
 314         for (; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry)) {
 315                 // skip entry
 316         }
 317         return entry;
 318 }
 319
 320 /*
 321  * assert that the elements in the ext4 xattr section are in sorted order
 322  *
 323  * The ext4 filesystem requires extended attributes to be sorted when
 324  * they're not stored in the inode. The kernel ext4 code uses the following
 325  * sorting algorithm:
 326  *
 327  * 1) First sort extended attributes by their name_index. For example,
 328  *    EXT4_XATTR_INDEX_USER (1) comes before EXT4_XATTR_INDEX_SECURITY (6).
 329  * 2) If the name_indexes are equal, then sorting is based on the length
 330  *    of the name. For example, XATTR_SELINUX_SUFFIX ("selinux") comes before
 331  *    XATTR_CAPS_SUFFIX ("capability") because "selinux" is shorter than "capability"
 332  * 3) If the name_index and name_length are equal, then memcmp() is used to determine
 333  *    which name comes first. For example, "selinux" would come before "yelinux".
 334  *
 335  * This method is intended to implement the sorting function defined in
 336  * the Linux kernel file fs/ext4/xattr.c function ext4_xattr_find_entry().
 337  */
 338 static void xattr_assert_sane(struct ext4_xattr_entry *entry)
 339 {
 340         for( ; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry)) {
 341                 struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(entry);
 342                 if (IS_LAST_ENTRY(next)) {
 343                         return;
 344                 }
 345
 346                 int cmp = next->e_name_index - entry->e_name_index;
 347                 if (cmp == 0)
 348                         cmp = next->e_name_len - entry->e_name_len;
 349                 if (cmp == 0)
 350                         cmp = memcmp(next->e_name, entry->e_name, next->e_name_len);
 351                 if (cmp < 0) {
 352                         error("BUG: extended attributes are not sorted\n");
 353                         return;
 354                 }
 355                 if (cmp == 0) {
 356                         error("BUG: duplicate extended attributes detected\n");
 357                         return;
 358                 }
 359         }
 360 }
 361
 362 #define NAME_HASH_SHIFT 5
 363 #define VALUE_HASH_SHIFT 16
 364
 365 static void ext4_xattr_hash_entry(struct ext4_xattr_header *header,
 366                 struct ext4_xattr_entry *entry)
 367 {
 368         u32 hash = 0;
 369         char *name = entry->e_name;
 370         int n;
 371
 372         for (n = 0; n < entry->e_name_len; n++) {
 373                 hash = (hash << NAME_HASH_SHIFT) ^
 374                         (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
 375                         *name++;
 376         }
 377
 378         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
 379                 u32 *value = (u32 *)((char *)header +
 380                         le16_to_cpu(entry->e_value_offs));
 381                 for (n = (le32_to_cpu(entry->e_value_size) +
 382                         EXT4_XATTR_ROUND) >> EXT4_XATTR_PAD_BITS; n; n--) {
 383                         hash = (hash << VALUE_HASH_SHIFT) ^
 384                                 (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
 385                                 le32_to_cpu(*value++);
 386                 }
 387         }
 388         entry->e_hash = cpu_to_le32(hash);
 389 }
 390
 391 #undef NAME_HASH_SHIFT
 392 #undef VALUE_HASH_SHIFT
 393
 394 static struct ext4_xattr_entry* xattr_addto_range(
 395                 void *block_start,
 396                 void *block_end,
 397                 struct ext4_xattr_entry *first,
 398                 int name_index,
 399                 const char *name,
 400                 const void *value,
 401                 size_t value_len)
 402 {
 403         size_t name_len = strlen(name);
 404         if (name_len > 255)
 405                 return NULL;
 406
 407         size_t available_size = xattr_free_space(first, block_end);
 408         size_t needed_size = EXT4_XATTR_LEN(name_len) + EXT4_XATTR_SIZE(value_len);
 409
 410         if (needed_size > available_size)
 411                 return NULL;
 412
 413         struct ext4_xattr_entry *new_entry = xattr_get_last(first);
 414         memset(new_entry, 0, EXT4_XATTR_LEN(name_len));
 415
 416         new_entry->e_name_len = name_len;
 417         new_entry->e_name_index = name_index;
 418         memcpy(new_entry->e_name, name, name_len);
 419         new_entry->e_value_block = 0;
 420         new_entry->e_value_size = cpu_to_le32(value_len);
 421
 422         char *val = (char *) new_entry + available_size - EXT4_XATTR_SIZE(value_len);
 423         size_t e_value_offs = val - (char *) block_start;
 424
 425         new_entry->e_value_offs = cpu_to_le16(e_value_offs);
 426         memset(val, 0, EXT4_XATTR_SIZE(value_len));
 427         memcpy(val, value, value_len);
 428
 429         xattr_assert_sane(first);
 430         return new_entry;
 431 }
 432
 433 static int xattr_addto_inode(struct ext4_inode *inode, int name_index,
 434                 const char *name, const void *value, size_t value_len)
 435 {
 436         struct ext4_xattr_ibody_header *hdr = (struct ext4_xattr_ibody_header *) (inode + 1);
 437         struct ext4_xattr_entry *first = (struct ext4_xattr_entry *) (hdr + 1);
 438         char *block_end = ((char *) inode) + info.inode_size;
 439
 440         struct ext4_xattr_entry *result =
 441                 xattr_addto_range(first, block_end, first, name_index, name, value, value_len);
 442
 443         if (result == NULL)
 444                 return -1;
 445
 446         hdr->h_magic = cpu_to_le32(EXT4_XATTR_MAGIC);
 447         inode->i_extra_isize = cpu_to_le16(sizeof(struct ext4_inode) - EXT4_GOOD_OLD_INODE_SIZE);
 448
 449         return 0;
 450 }
 451
 452 static int xattr_addto_block(struct ext4_inode *inode, int name_index,
 453                 const char *name, const void *value, size_t value_len)
 454 {
 455         struct ext4_xattr_header *header = get_xattr_block_for_inode(inode);
 456         if (!header)
 457                 return -1;
 458
 459         struct ext4_xattr_entry *first = (struct ext4_xattr_entry *) (header + 1);
 460         char *block_end = ((char *) header) + info.block_size;
 461
 462         struct ext4_xattr_entry *result =
 463                 xattr_addto_range(header, block_end, first, name_index, name, value, value_len);
 464
 465         if (result == NULL)
 466                 return -1;
 467
 468         ext4_xattr_hash_entry(header, result);
 469         return 0;
 470 }
 471
 472
 473 static int xattr_add(u32 inode_num, int name_index, const char *name,
 474                 const void *value, size_t value_len)
 475 {
 476         if (!value)
 477                 return 0;
 478
 479         struct ext4_inode *inode = get_inode(inode_num);
 480
 481         if (!inode)
 482                 return -1;
 483
 484         int result = xattr_addto_inode(inode, name_index, name, value, value_len);
 485         if (result != 0) {
 486                 result = xattr_addto_block(inode, name_index, name, value, value_len);
 487         }
 488         return result;
 489 }
 490
 491 int inode_set_capabilities(u32 inode_num, uint64_t capabilities) {
 492         if (capabilities == 0)
 493                 return 0;
 494
 495         struct vfs_cap_data cap_data;
 496         memset(&cap_data, 0, sizeof(cap_data));
 497
 498         cap_data.magic_etc = VFS_CAP_REVISION | VFS_CAP_FLAGS_EFFECTIVE;
 499         cap_data.data[0].permitted = (uint32_t) (capabilities & 0xffffffff);
 500         cap_data.data[0].inheritable = 0;
 501         cap_data.data[1].permitted = (uint32_t) (capabilities >> 32);
 502         cap_data.data[1].inheritable = 0;
 503
 504         return xattr_add(inode_num, EXT4_XATTR_INDEX_SECURITY,
 505                 XATTR_CAPS_SUFFIX, &cap_data, sizeof(cap_data));
 506 }