/**
* 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"
/**
* 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;
size_t save_num_header_bytes_at_front =
crypt_stat->num_header_bytes_at_front;
crypt_stat->num_header_bytes_at_front =
ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
ecryptfs_write_header_metadata(page_virt + 20, crypt_stat, &written);
crypt_stat->num_header_bytes_at_front =
save_num_header_bytes_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);
size_t num_header_extents_at_front =
(crypt_stat->num_header_bytes_at_front
/ 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, 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->extent_size)
- crypt_stat->num_header_bytes_at_front);
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,
};
