/** * eCryptfs: Linux filesystem encryption layer * This is where eCryptfs coordinates the symmetric encryption and * decryption of the file data as it passes between the lower * encrypted file and the upper decrypted file. * * Copyright (C) 1997-2003 Erez Zadok * Copyright (C) 2001-2003 Stony Brook University * Copyright (C) 2004-2007 International Business Machines Corp. * Author(s): Michael A. Halcrow <mahalcro@us.ibm.com> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation; either version 2 of the * License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA * 02111-1307, USA. */ #include <linux/pagemap.h> #include <linux/writeback.h> #include <linux/page-flags.h> #include <linux/mount.h> #include <linux/file.h> #include <linux/scatterlist.h> #include <linux/slab.h> #include <linux/xattr.h> #include <asm/unaligned.h> #include "ecryptfs_kernel.h" /** * ecryptfs_get_locked_page * * Get one page from cache or lower f/s, return error otherwise. * * Returns locked and up-to-date page (if ok), with increased * refcnt. */ struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index) { struct page *page = read_mapping_page(inode->i_mapping, index, NULL); if (!IS_ERR(page)) lock_page(page); return page; } /** * ecryptfs_writepage * @page: Page that is locked before this call is made * * Returns zero on success; non-zero otherwise * * This is where we encrypt the data and pass the encrypted data to * the lower filesystem. In OpenPGP-compatible mode, we operate on * entire underlying packets. */ static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc) { int rc; rc = ecryptfs_encrypt_page(page); if (rc) { ecryptfs_printk(KERN_WARNING, "Error encrypting " "page (upper index [0x%.16lx])\n", page->index); ClearPageUptodate(page); goto out; } SetPageUptodate(page); out: unlock_page(page); return rc; } static void strip_xattr_flag(char *page_virt, struct ecryptfs_crypt_stat *crypt_stat) { if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { size_t written; crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR; ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat, &written); crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR; } } /** * Header Extent: * Octets 0-7: Unencrypted file size (big-endian) * Octets 8-15: eCryptfs special marker * Octets 16-19: Flags * Octet 16: File format version number (between 0 and 255) * Octets 17-18: Reserved * Octet 19: Bit 1 (lsb): Reserved * Bit 2: Encrypted? * Bits 3-8: Reserved * Octets 20-23: Header extent size (big-endian) * Octets 24-25: Number of header extents at front of file * (big-endian) * Octet 26: Begin RFC 2440 authentication token packet set */ /** * ecryptfs_copy_up_encrypted_with_header * @page: Sort of a ``virtual'' representation of the encrypted lower * file. The actual lower file does not have the metadata in * the header. This is locked. * @crypt_stat: The eCryptfs inode's cryptographic context * * The ``view'' is the version of the file that userspace winds up * seeing, with the header information inserted. */ static int ecryptfs_copy_up_encrypted_with_header(struct page *page, struct ecryptfs_crypt_stat *crypt_stat) { loff_t extent_num_in_page = 0; loff_t num_extents_per_page = (PAGE_SIZE / crypt_stat->extent_size); int rc = 0; while (extent_num_in_page < num_extents_per_page) { loff_t view_extent_num = ((((loff_t)page->index) * num_extents_per_page) + extent_num_in_page); size_t num_header_extents_at_front = (crypt_stat->metadata_size / crypt_stat->extent_size); if (view_extent_num < num_header_extents_at_front) { /* This is a header extent */ char *page_virt; page_virt = kmap_atomic(page); memset(page_virt, 0, PAGE_SIZE); /* TODO: Support more than one header extent */ if (view_extent_num == 0) { size_t written; rc = ecryptfs_read_xattr_region( page_virt, page->mapping->host); strip_xattr_flag(page_virt + 16, crypt_stat); ecryptfs_write_header_metadata(page_virt + 20, crypt_stat, &written); } kunmap_atomic(page_virt); flush_dcache_page(page); if (rc) { printk(KERN_ERR "%s: Error reading xattr " "region; rc = [%d]\n", __func__, rc); goto out; } } else { /* This is an encrypted data extent */ loff_t lower_offset = ((view_extent_num * crypt_stat->extent_size) - crypt_stat->metadata_size); rc = ecryptfs_read_lower_page_segment( page, (lower_offset >> PAGE_SHIFT), (lower_offset & ~PAGE_MASK), crypt_stat->extent_size, page->mapping->host); if (rc) { printk(KERN_ERR "%s: Error attempting to read " "extent at offset [%lld] in the lower " "file; rc = [%d]\n", __func__, lower_offset, rc); goto out; } } extent_num_in_page++; } out: return rc; } /** * ecryptfs_readpage * @file: An eCryptfs file * @page: Page from eCryptfs inode mapping into which to stick the read data * * Read in a page, decrypting if necessary. * * Returns zero on success; non-zero on error. */ static int ecryptfs_readpage(struct file *file, struct page *page) { struct ecryptfs_crypt_stat *crypt_stat = &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat; int rc = 0; if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { rc = ecryptfs_read_lower_page_segment(page, page->index, 0, PAGE_SIZE, page->mapping->host); } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { rc = ecryptfs_copy_up_encrypted_with_header(page, crypt_stat); if (rc) { printk(KERN_ERR "%s: Error attempting to copy " "the encrypted content from the lower " "file whilst inserting the metadata " "from the xattr into the header; rc = " "[%d]\n", __func__, rc); goto out; } } else { rc = ecryptfs_read_lower_page_segment( page, page->index, 0, PAGE_SIZE, page->mapping->host); if (rc) { printk(KERN_ERR "Error reading page; rc = " "[%d]\n", rc); goto out; } } } else { rc = ecryptfs_decrypt_page(page); if (rc) { ecryptfs_printk(KERN_ERR, "Error decrypting page; " "rc = [%d]\n", rc); goto out; } } out: if (rc) ClearPageUptodate(page); else SetPageUptodate(page); ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n", page->index); unlock_page(page); return rc; } /** * Called with lower inode mutex held. */ static int fill_zeros_to_end_of_page(struct page *page, unsigned int to) { struct inode *inode = page->mapping->host; int end_byte_in_page; if ((i_size_read(inode) / PAGE_SIZE) != page->index) goto out; end_byte_in_page = i_size_read(inode) % PAGE_SIZE; if (to > end_byte_in_page) end_byte_in_page = to; zero_user_segment(page, end_byte_in_page, PAGE_SIZE); out: return 0; } /** * ecryptfs_write_begin * @file: The eCryptfs file * @mapping: The eCryptfs object * @pos: The file offset at which to start writing * @len: Length of the write * @flags: Various flags * @pagep: Pointer to return the page * @fsdata: Pointer to return fs data (unused) * * This function must zero any hole we create * * Returns zero on success; non-zero otherwise */ static int ecryptfs_write_begin(struct file *file, struct address_space *mapping, loff_t pos, unsigned len, unsigned flags, struct page **pagep, void **fsdata) { pgoff_t index = pos >> PAGE_SHIFT; struct page *page; loff_t prev_page_end_size; int rc = 0; page = grab_cache_page_write_begin(mapping, index, flags); if (!page) return -ENOMEM; *pagep = page; prev_page_end_size = ((loff_t)index << PAGE_SHIFT); if (!PageUptodate(page)) { struct ecryptfs_crypt_stat *crypt_stat = &ecryptfs_inode_to_private(mapping->host)->crypt_stat; if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { rc = ecryptfs_read_lower_page_segment( page, index, 0, PAGE_SIZE, mapping->host); if (rc) { printk(KERN_ERR "%s: Error attempting to read " "lower page segment; rc = [%d]\n", __func__, rc); ClearPageUptodate(page); goto out; } else SetPageUptodate(page); } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { rc = ecryptfs_copy_up_encrypted_with_header( page, crypt_stat); if (rc) { printk(KERN_ERR "%s: Error attempting " "to copy the encrypted content " "from the lower file whilst " "inserting the metadata from " "the xattr into the header; rc " "= [%d]\n", __func__, rc); ClearPageUptodate(page); goto out; } SetPageUptodate(page); } else { rc = ecryptfs_read_lower_page_segment( page, index, 0, PAGE_SIZE, mapping->host); if (rc) { printk(KERN_ERR "%s: Error reading " "page; rc = [%d]\n", __func__, rc); ClearPageUptodate(page); goto out; } SetPageUptodate(page); } } else { if (prev_page_end_size >= i_size_read(page->mapping->host)) { zero_user(page, 0, PAGE_SIZE); SetPageUptodate(page); } else if (len < PAGE_SIZE) { rc = ecryptfs_decrypt_page(page); if (rc) { printk(KERN_ERR "%s: Error decrypting " "page at index [%ld]; " "rc = [%d]\n", __func__, page->index, rc); ClearPageUptodate(page); goto out; } SetPageUptodate(page); } } } /* If creating a page or more of holes, zero them out via truncate. * Note, this will increase i_size. */ if (index != 0) { if (prev_page_end_size > i_size_read(page->mapping->host)) { rc = ecryptfs_truncate(file->f_path.dentry, prev_page_end_size); if (rc) { printk(KERN_ERR "%s: Error on attempt to " "truncate to (higher) offset [%lld];" " rc = [%d]\n", __func__, prev_page_end_size, rc); goto out; } } } /* Writing to a new page, and creating a small hole from start * of page? Zero it out. */ if ((i_size_read(mapping->host) == prev_page_end_size) && (pos != 0)) zero_user(page, 0, PAGE_SIZE); out: if (unlikely(rc)) { unlock_page(page); put_page(page); *pagep = NULL; } return rc; } /** * ecryptfs_write_inode_size_to_header * * Writes the lower file size to the first 8 bytes of the header. * * Returns zero on success; non-zero on error. */ static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode) { char *file_size_virt; int rc; file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL); if (!file_size_virt) { rc = -ENOMEM; goto out; } put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt); rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0, sizeof(u64)); kfree(file_size_virt); if (rc < 0) printk(KERN_ERR "%s: Error writing file size to header; " "rc = [%d]\n", __func__, rc); else rc = 0; out: return rc; } struct kmem_cache *ecryptfs_xattr_cache; static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode) { ssize_t size; void *xattr_virt; struct dentry *lower_dentry = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry; struct inode *lower_inode = d_inode(lower_dentry); int rc; if (!(lower_inode->i_opflags & IOP_XATTR)) { printk(KERN_WARNING "No support for setting xattr in lower filesystem\n"); rc = -ENOSYS; goto out; } xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL); if (!xattr_virt) { rc = -ENOMEM; goto out; } inode_lock(lower_inode); size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME, xattr_virt, PAGE_SIZE); if (size < 0) size = 8; put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt); rc = __vfs_setxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME, xattr_virt, size, 0); inode_unlock(lower_inode); if (rc) printk(KERN_ERR "Error whilst attempting to write inode size " "to lower file xattr; rc = [%d]\n", rc); kmem_cache_free(ecryptfs_xattr_cache, xattr_virt); out: return rc; } int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode) { struct ecryptfs_crypt_stat *crypt_stat; crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)); if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode); else return ecryptfs_write_inode_size_to_header(ecryptfs_inode); } /** * ecryptfs_write_end * @file: The eCryptfs file object * @mapping: The eCryptfs object * @pos: The file position * @len: The length of the data (unused) * @copied: The amount of data copied * @page: The eCryptfs page * @fsdata: The fsdata (unused) */ static int ecryptfs_write_end(struct file *file, struct address_space *mapping, loff_t pos, unsigned len, unsigned copied, struct page *page, void *fsdata) { pgoff_t index = pos >> PAGE_SHIFT; unsigned from = pos & (PAGE_SIZE - 1); unsigned to = from + copied; struct inode *ecryptfs_inode = mapping->host; struct ecryptfs_crypt_stat *crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; int rc; ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page" "(page w/ index = [0x%.16lx], to = [%d])\n", index, to); if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) { rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0, to); if (!rc) { rc = copied; fsstack_copy_inode_size(ecryptfs_inode, ecryptfs_inode_to_lower(ecryptfs_inode)); } goto out; } if (!PageUptodate(page)) { if (copied < PAGE_SIZE) { rc = 0; goto out; } SetPageUptodate(page); } /* Fills in zeros if 'to' goes beyond inode size */ rc = fill_zeros_to_end_of_page(page, to); if (rc) { ecryptfs_printk(KERN_WARNING, "Error attempting to fill " "zeros in page with index = [0x%.16lx]\n", index); goto out; } rc = ecryptfs_encrypt_page(page); if (rc) { ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper " "index [0x%.16lx])\n", index); goto out; } if (pos + copied > i_size_read(ecryptfs_inode)) { i_size_write(ecryptfs_inode, pos + copied); ecryptfs_printk(KERN_DEBUG, "Expanded file size to " "[0x%.16llx]\n", (unsigned long long)i_size_read(ecryptfs_inode)); } rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode); if (rc) printk(KERN_ERR "Error writing inode size to metadata; " "rc = [%d]\n", rc); else rc = copied; out: unlock_page(page); put_page(page); return rc; } static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block) { int rc = 0; struct inode *inode; struct inode *lower_inode; inode = (struct inode *)mapping->host; lower_inode = ecryptfs_inode_to_lower(inode); if (lower_inode->i_mapping->a_ops->bmap) rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping, block); return rc; } const struct address_space_operations ecryptfs_aops = { .writepage = ecryptfs_writepage, .readpage = ecryptfs_readpage, .write_begin = ecryptfs_write_begin, .write_end = ecryptfs_write_end, .bmap = ecryptfs_bmap, };