1 /** 2 * eCryptfs: Linux filesystem encryption layer 3 * 4 * Copyright (C) 2007 International Business Machines Corp. 5 * Author(s): Michael A. Halcrow <mahalcro@us.ibm.com> 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License as 9 * published by the Free Software Foundation; either version 2 of the 10 * License, or (at your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, but 13 * WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License 18 * along with this program; if not, write to the Free Software 19 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 20 * 02111-1307, USA. 21 */ 22 23 #include <linux/fs.h> 24 #include <linux/pagemap.h> 25 #include "ecryptfs_kernel.h" 26 27 /** 28 * ecryptfs_write_lower 29 * @ecryptfs_inode: The eCryptfs inode 30 * @data: Data to write 31 * @offset: Byte offset in the lower file to which to write the data 32 * @size: Number of bytes from @data to write at @offset in the lower 33 * file 34 * 35 * Write data to the lower file. 36 * 37 * Returns zero on success; non-zero on error 38 */ 39 int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data, 40 loff_t offset, size_t size) 41 { 42 struct ecryptfs_inode_info *inode_info; 43 ssize_t octets_written; 44 mm_segment_t fs_save; 45 int rc = 0; 46 47 inode_info = ecryptfs_inode_to_private(ecryptfs_inode); 48 mutex_lock(&inode_info->lower_file_mutex); 49 BUG_ON(!inode_info->lower_file); 50 inode_info->lower_file->f_pos = offset; 51 fs_save = get_fs(); 52 set_fs(get_ds()); 53 octets_written = vfs_write(inode_info->lower_file, data, size, 54 &inode_info->lower_file->f_pos); 55 set_fs(fs_save); 56 if (octets_written < 0) { 57 printk(KERN_ERR "%s: octets_written = [%td]; " 58 "expected [%td]\n", __FUNCTION__, octets_written, size); 59 rc = -EINVAL; 60 } 61 mutex_unlock(&inode_info->lower_file_mutex); 62 mark_inode_dirty_sync(ecryptfs_inode); 63 return rc; 64 } 65 66 /** 67 * ecryptfs_write_lower_page_segment 68 * @ecryptfs_inode: The eCryptfs inode 69 * @page_for_lower: The page containing the data to be written to the 70 * lower file 71 * @offset_in_page: The offset in the @page_for_lower from which to 72 * start writing the data 73 * @size: The amount of data from @page_for_lower to write to the 74 * lower file 75 * 76 * Determines the byte offset in the file for the given page and 77 * offset within the page, maps the page, and makes the call to write 78 * the contents of @page_for_lower to the lower inode. 79 * 80 * Returns zero on success; non-zero otherwise 81 */ 82 int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode, 83 struct page *page_for_lower, 84 size_t offset_in_page, size_t size) 85 { 86 char *virt; 87 loff_t offset; 88 int rc; 89 90 offset = ((((off_t)page_for_lower->index) << PAGE_CACHE_SHIFT) 91 + offset_in_page); 92 virt = kmap(page_for_lower); 93 rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size); 94 kunmap(page_for_lower); 95 return rc; 96 } 97 98 /** 99 * ecryptfs_write 100 * @ecryptfs_file: The eCryptfs file into which to write 101 * @data: Virtual address where data to write is located 102 * @offset: Offset in the eCryptfs file at which to begin writing the 103 * data from @data 104 * @size: The number of bytes to write from @data 105 * 106 * Write an arbitrary amount of data to an arbitrary location in the 107 * eCryptfs inode page cache. This is done on a page-by-page, and then 108 * by an extent-by-extent, basis; individual extents are encrypted and 109 * written to the lower page cache (via VFS writes). This function 110 * takes care of all the address translation to locations in the lower 111 * filesystem; it also handles truncate events, writing out zeros 112 * where necessary. 113 * 114 * Returns zero on success; non-zero otherwise 115 */ 116 int ecryptfs_write(struct file *ecryptfs_file, char *data, loff_t offset, 117 size_t size) 118 { 119 struct page *ecryptfs_page; 120 char *ecryptfs_page_virt; 121 loff_t ecryptfs_file_size = 122 i_size_read(ecryptfs_file->f_dentry->d_inode); 123 loff_t data_offset = 0; 124 loff_t pos; 125 int rc = 0; 126 127 if (offset > ecryptfs_file_size) 128 pos = ecryptfs_file_size; 129 else 130 pos = offset; 131 while (pos < (offset + size)) { 132 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT); 133 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK); 134 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page); 135 size_t total_remaining_bytes = ((offset + size) - pos); 136 137 if (num_bytes > total_remaining_bytes) 138 num_bytes = total_remaining_bytes; 139 if (pos < offset) { 140 size_t total_remaining_zeros = (offset - pos); 141 142 if (num_bytes > total_remaining_zeros) 143 num_bytes = total_remaining_zeros; 144 } 145 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file, 146 ecryptfs_page_idx); 147 if (IS_ERR(ecryptfs_page)) { 148 rc = PTR_ERR(ecryptfs_page); 149 printk(KERN_ERR "%s: Error getting page at " 150 "index [%ld] from eCryptfs inode " 151 "mapping; rc = [%d]\n", __FUNCTION__, 152 ecryptfs_page_idx, rc); 153 goto out; 154 } 155 if (start_offset_in_page) { 156 /* Read in the page from the lower 157 * into the eCryptfs inode page cache, 158 * decrypting */ 159 rc = ecryptfs_decrypt_page(ecryptfs_page); 160 if (rc) { 161 printk(KERN_ERR "%s: Error decrypting " 162 "page; rc = [%d]\n", 163 __FUNCTION__, rc); 164 ClearPageUptodate(ecryptfs_page); 165 page_cache_release(ecryptfs_page); 166 goto out; 167 } 168 } 169 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0); 170 if (pos >= offset) { 171 memcpy(((char *)ecryptfs_page_virt 172 + start_offset_in_page), 173 (data + data_offset), num_bytes); 174 data_offset += num_bytes; 175 } else { 176 /* We are extending past the previous end of the file. 177 * Fill in zero values up to the start of where we 178 * will be writing data. */ 179 memset(((char *)ecryptfs_page_virt 180 + start_offset_in_page), 0, num_bytes); 181 } 182 kunmap_atomic(ecryptfs_page_virt, KM_USER0); 183 flush_dcache_page(ecryptfs_page); 184 SetPageUptodate(ecryptfs_page); 185 unlock_page(ecryptfs_page); 186 rc = ecryptfs_encrypt_page(ecryptfs_page); 187 page_cache_release(ecryptfs_page); 188 if (rc) { 189 printk(KERN_ERR "%s: Error encrypting " 190 "page; rc = [%d]\n", __FUNCTION__, rc); 191 goto out; 192 } 193 pos += num_bytes; 194 } 195 if ((offset + size) > ecryptfs_file_size) { 196 i_size_write(ecryptfs_file->f_dentry->d_inode, (offset + size)); 197 rc = ecryptfs_write_inode_size_to_metadata( 198 ecryptfs_file->f_dentry->d_inode); 199 if (rc) { 200 printk(KERN_ERR "Problem with " 201 "ecryptfs_write_inode_size_to_metadata; " 202 "rc = [%d]\n", rc); 203 goto out; 204 } 205 } 206 out: 207 return rc; 208 } 209 210 /** 211 * ecryptfs_read_lower 212 * @data: The read data is stored here by this function 213 * @offset: Byte offset in the lower file from which to read the data 214 * @size: Number of bytes to read from @offset of the lower file and 215 * store into @data 216 * @ecryptfs_inode: The eCryptfs inode 217 * 218 * Read @size bytes of data at byte offset @offset from the lower 219 * inode into memory location @data. 220 * 221 * Returns zero on success; non-zero on error 222 */ 223 int ecryptfs_read_lower(char *data, loff_t offset, size_t size, 224 struct inode *ecryptfs_inode) 225 { 226 struct ecryptfs_inode_info *inode_info = 227 ecryptfs_inode_to_private(ecryptfs_inode); 228 ssize_t octets_read; 229 mm_segment_t fs_save; 230 int rc = 0; 231 232 mutex_lock(&inode_info->lower_file_mutex); 233 BUG_ON(!inode_info->lower_file); 234 inode_info->lower_file->f_pos = offset; 235 fs_save = get_fs(); 236 set_fs(get_ds()); 237 octets_read = vfs_read(inode_info->lower_file, data, size, 238 &inode_info->lower_file->f_pos); 239 set_fs(fs_save); 240 if (octets_read < 0) { 241 printk(KERN_ERR "%s: octets_read = [%td]; " 242 "expected [%td]\n", __FUNCTION__, octets_read, size); 243 rc = -EINVAL; 244 } 245 mutex_unlock(&inode_info->lower_file_mutex); 246 return rc; 247 } 248 249 /** 250 * ecryptfs_read_lower_page_segment 251 * @page_for_ecryptfs: The page into which data for eCryptfs will be 252 * written 253 * @offset_in_page: Offset in @page_for_ecryptfs from which to start 254 * writing 255 * @size: The number of bytes to write into @page_for_ecryptfs 256 * @ecryptfs_inode: The eCryptfs inode 257 * 258 * Determines the byte offset in the file for the given page and 259 * offset within the page, maps the page, and makes the call to read 260 * the contents of @page_for_ecryptfs from the lower inode. 261 * 262 * Returns zero on success; non-zero otherwise 263 */ 264 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs, 265 pgoff_t page_index, 266 size_t offset_in_page, size_t size, 267 struct inode *ecryptfs_inode) 268 { 269 char *virt; 270 loff_t offset; 271 int rc; 272 273 offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page); 274 virt = kmap(page_for_ecryptfs); 275 rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode); 276 kunmap(page_for_ecryptfs); 277 flush_dcache_page(page_for_ecryptfs); 278 return rc; 279 } 280 281 /** 282 * ecryptfs_read 283 * @data: The virtual address into which to write the data read (and 284 * possibly decrypted) from the lower file 285 * @offset: The offset in the decrypted view of the file from which to 286 * read into @data 287 * @size: The number of bytes to read into @data 288 * @ecryptfs_file: The eCryptfs file from which to read 289 * 290 * Read an arbitrary amount of data from an arbitrary location in the 291 * eCryptfs page cache. This is done on an extent-by-extent basis; 292 * individual extents are decrypted and read from the lower page 293 * cache (via VFS reads). This function takes care of all the 294 * address translation to locations in the lower filesystem. 295 * 296 * Returns zero on success; non-zero otherwise 297 */ 298 int ecryptfs_read(char *data, loff_t offset, size_t size, 299 struct file *ecryptfs_file) 300 { 301 struct page *ecryptfs_page; 302 char *ecryptfs_page_virt; 303 loff_t ecryptfs_file_size = 304 i_size_read(ecryptfs_file->f_dentry->d_inode); 305 loff_t data_offset = 0; 306 loff_t pos; 307 int rc = 0; 308 309 if ((offset + size) > ecryptfs_file_size) { 310 rc = -EINVAL; 311 printk(KERN_ERR "%s: Attempt to read data past the end of the " 312 "file; offset = [%lld]; size = [%td]; " 313 "ecryptfs_file_size = [%lld]\n", 314 __FUNCTION__, offset, size, ecryptfs_file_size); 315 goto out; 316 } 317 pos = offset; 318 while (pos < (offset + size)) { 319 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT); 320 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK); 321 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page); 322 size_t total_remaining_bytes = ((offset + size) - pos); 323 324 if (num_bytes > total_remaining_bytes) 325 num_bytes = total_remaining_bytes; 326 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file, 327 ecryptfs_page_idx); 328 if (IS_ERR(ecryptfs_page)) { 329 rc = PTR_ERR(ecryptfs_page); 330 printk(KERN_ERR "%s: Error getting page at " 331 "index [%ld] from eCryptfs inode " 332 "mapping; rc = [%d]\n", __FUNCTION__, 333 ecryptfs_page_idx, rc); 334 goto out; 335 } 336 rc = ecryptfs_decrypt_page(ecryptfs_page); 337 if (rc) { 338 printk(KERN_ERR "%s: Error decrypting " 339 "page; rc = [%d]\n", __FUNCTION__, rc); 340 ClearPageUptodate(ecryptfs_page); 341 page_cache_release(ecryptfs_page); 342 goto out; 343 } 344 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0); 345 memcpy((data + data_offset), 346 ((char *)ecryptfs_page_virt + start_offset_in_page), 347 num_bytes); 348 kunmap_atomic(ecryptfs_page_virt, KM_USER0); 349 flush_dcache_page(ecryptfs_page); 350 SetPageUptodate(ecryptfs_page); 351 unlock_page(ecryptfs_page); 352 page_cache_release(ecryptfs_page); 353 pos += num_bytes; 354 data_offset += num_bytes; 355 } 356 out: 357 return rc; 358 } 359