/** * 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/crypto.h> #include <linux/scatterlist.h> #include "ecryptfs_kernel.h" struct kmem_cache *ecryptfs_lower_page_cache; /** * 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 file *file, loff_t index) { struct dentry *dentry; struct inode *inode; struct address_space *mapping; struct page *page; dentry = file->f_path.dentry; inode = dentry->d_inode; mapping = inode->i_mapping; page = read_mapping_page(mapping, index, (void *)file); 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 */ 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%.16x])\n", page->index); ClearPageUptodate(page); goto out; } SetPageUptodate(page); unlock_page(page); out: return rc; } /** * 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 */ static void set_header_info(char *page_virt, struct ecryptfs_crypt_stat *crypt_stat) { size_t written; int save_num_header_extents_at_front = crypt_stat->num_header_extents_at_front; crypt_stat->num_header_extents_at_front = 1; ecryptfs_write_header_metadata(page_virt + 20, crypt_stat, &written); crypt_stat->num_header_extents_at_front = save_num_header_extents_at_front; } /** * 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_CACHE_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); if (view_extent_num < crypt_stat->num_header_extents_at_front) { /* This is a header extent */ char *page_virt; page_virt = kmap_atomic(page, KM_USER0); memset(page_virt, 0, PAGE_CACHE_SIZE); /* TODO: Support more than one header extent */ if (view_extent_num == 0) { rc = ecryptfs_read_xattr_region( page_virt, page->mapping->host); set_header_info(page_virt, crypt_stat); } kunmap_atomic(page_virt, KM_USER0); flush_dcache_page(page); if (rc) { printk(KERN_ERR "%s: Error reading xattr " "region; rc = [%d]\n", __FUNCTION__, rc); goto out; } } else { /* This is an encrypted data extent */ loff_t lower_offset = ((view_extent_num - crypt_stat->num_header_extents_at_front) * crypt_stat->extent_size); rc = ecryptfs_read_lower_page_segment( page, (lower_offset >> PAGE_CACHE_SHIFT), (lower_offset & ~PAGE_CACHE_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", __FUNCTION__, 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(file->f_path.dentry->d_inode)->crypt_stat; int rc = 0; if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED) || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) { ecryptfs_printk(KERN_DEBUG, "Passing through unencrypted page\n"); rc = ecryptfs_read_lower_page_segment(page, page->index, 0, PAGE_CACHE_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", __FUNCTION__, rc); goto out; } } else { rc = ecryptfs_read_lower_page_segment( page, page->index, 0, PAGE_CACHE_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%.16x]\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_CACHE_SIZE) != page->index) goto out; end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE; if (to > end_byte_in_page) end_byte_in_page = to; zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE); out: return 0; } /* This function must zero any hole we create */ static int ecryptfs_prepare_write(struct file *file, struct page *page, unsigned from, unsigned to) { int rc = 0; loff_t prev_page_end_size; if (!PageUptodate(page)) { rc = ecryptfs_read_lower_page_segment(page, page->index, 0, PAGE_CACHE_SIZE, page->mapping->host); if (rc) { printk(KERN_ERR "%s: Error attemping to read lower " "page segment; rc = [%d]\n", __FUNCTION__, rc); ClearPageUptodate(page); goto out; } else SetPageUptodate(page); } prev_page_end_size = ((loff_t)page->index << PAGE_CACHE_SHIFT); /* * If creating a page or more of holes, zero them out via truncate. * Note, this will increase i_size. */ if (page->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 "Error on attempt to " "truncate to (higher) offset [%lld];" " rc = [%d]\n", 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(page->mapping->host) == prev_page_end_size) && (from != 0)) { zero_user(page, 0, PAGE_CACHE_SIZE); } out: 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) { u64 file_size; char *file_size_virt; int rc; file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL); if (!file_size_virt) { rc = -ENOMEM; goto out; } file_size = (u64)i_size_read(ecryptfs_inode); file_size = cpu_to_be64(file_size); memcpy(file_size_virt, &file_size, sizeof(u64)); rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0, sizeof(u64)); kfree(file_size_virt); if (rc) printk(KERN_ERR "%s: Error writing file size to header; " "rc = [%d]\n", __FUNCTION__, rc); 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_dentry; struct inode *lower_inode = lower_dentry->d_inode; u64 file_size; int rc; if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) { 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) { printk(KERN_ERR "Out of memory whilst attempting to write " "inode size to xattr\n"); rc = -ENOMEM; goto out; } mutex_lock(&lower_inode->i_mutex); size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME, xattr_virt, PAGE_CACHE_SIZE); if (size < 0) size = 8; file_size = (u64)i_size_read(ecryptfs_inode); file_size = cpu_to_be64(file_size); memcpy(xattr_virt, &file_size, sizeof(u64)); rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME, xattr_virt, size, 0); mutex_unlock(&lower_inode->i_mutex); 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; 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_commit_write * @file: The eCryptfs file object * @page: The eCryptfs page * @from: Ignored (we rotate the page IV on each write) * @to: Ignored * * 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_commit_write(struct file *file, struct page *page, unsigned from, unsigned to) { loff_t pos; struct inode *ecryptfs_inode = page->mapping->host; struct ecryptfs_crypt_stat *crypt_stat = &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat; int rc; if (crypt_stat->flags & ECRYPTFS_NEW_FILE) { ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in " "crypt_stat at memory location [%p]\n", crypt_stat); crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE); } else ecryptfs_printk(KERN_DEBUG, "Not a new file\n"); ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page" "(page w/ index = [0x%.16x], to = [%d])\n", page->index, to); /* 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%.16x]\n", page->index); goto out; } rc = ecryptfs_encrypt_page(page); if (rc) { ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper " "index [0x%.16x])\n", page->index); goto out; } pos = (((loff_t)page->index) << PAGE_CACHE_SHIFT) + to; if (pos > i_size_read(ecryptfs_inode)) { i_size_write(ecryptfs_inode, pos); ecryptfs_printk(KERN_DEBUG, "Expanded file size to " "[0x%.16x]\n", 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); out: 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; } struct address_space_operations ecryptfs_aops = { .writepage = ecryptfs_writepage, .readpage = ecryptfs_readpage, .prepare_write = ecryptfs_prepare_write, .commit_write = ecryptfs_commit_write, .bmap = ecryptfs_bmap, };