// SPDX-License-Identifier: GPL-2.0-or-later
/*
* 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 <[email protected]>
*/
#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 <linux/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
* @wbc: Write-back control structure
*
* 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_local_page(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_local(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_read_folio
* @file: An eCryptfs file
* @folio: Folio from eCryptfs inode mapping into which to stick the read data
*
* Read in a folio, decrypting if necessary.
*
* Returns zero on success; non-zero on error.
*/
static int ecryptfs_read_folio(struct file *file, struct folio *folio)
{
struct page *page = &folio->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 folio *folio, unsigned int to)
{
struct inode *inode = folio->mapping->host;
int end_byte_in_page;
if ((i_size_read(inode) / PAGE_SIZE) != folio->index)
goto out;
end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
if (to > end_byte_in_page)
end_byte_in_page = to;
folio_zero_segment(folio, 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
* @foliop: Pointer to return the folio
* @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,
struct folio **foliop, void **fsdata)
{
pgoff_t index = pos >> PAGE_SHIFT;
struct folio *folio;
loff_t prev_page_end_size;
int rc = 0;
folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
mapping_gfp_mask(mapping));
if (IS_ERR(folio))
return PTR_ERR(folio);
*foliop = folio;
prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
if (!folio_test_uptodate(folio)) {
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(
&folio->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);
folio_clear_uptodate(folio);
goto out;
} else
folio_mark_uptodate(folio);
} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
rc = ecryptfs_copy_up_encrypted_with_header(
&folio->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);
folio_clear_uptodate(folio);
goto out;
}
folio_mark_uptodate(folio);
} else {
rc = ecryptfs_read_lower_page_segment(
&folio->page, index, 0, PAGE_SIZE,
mapping->host);
if (rc) {
printk(KERN_ERR "%s: Error reading "
"page; rc = [%d]\n",
__func__, rc);
folio_clear_uptodate(folio);
goto out;
}
folio_mark_uptodate(folio);
}
} else {
if (prev_page_end_size
>= i_size_read(mapping->host)) {
folio_zero_range(folio, 0, PAGE_SIZE);
folio_mark_uptodate(folio);
} else if (len < PAGE_SIZE) {
rc = ecryptfs_decrypt_page(&folio->page);
if (rc) {
printk(KERN_ERR "%s: Error decrypting "
"page at index [%ld]; "
"rc = [%d]\n",
__func__, folio->index, rc);
folio_clear_uptodate(folio);
goto out;
}
folio_mark_uptodate(folio);
}
}
}
/* 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(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))
folio_zero_range(folio, 0, PAGE_SIZE);
out:
if (unlikely(rc)) {
folio_unlock(folio);
folio_put(folio);
}
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(&nop_mnt_idmap, 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
* @folio: The eCryptfs folio
* @fsdata: The fsdata (unused)
*/
static int ecryptfs_write_end(struct file *file,
struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
struct folio *folio, 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,
&folio->page, 0, to);
if (!rc) {
rc = copied;
fsstack_copy_inode_size(ecryptfs_inode,
ecryptfs_inode_to_lower(ecryptfs_inode));
}
goto out;
}
if (!folio_test_uptodate(folio)) {
if (copied < PAGE_SIZE) {
rc = 0;
goto out;
}
folio_mark_uptodate(folio);
}
/* Fills in zeros if 'to' goes beyond inode size */
rc = fill_zeros_to_end_of_page(folio, 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(&folio->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:
folio_unlock(folio);
folio_put(folio);
return rc;
}
static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
{
struct inode *lower_inode = ecryptfs_inode_to_lower(mapping->host);
int ret = bmap(lower_inode, &block);
if (ret)
return 0;
return block;
}
#include <linux/buffer_head.h>
const struct address_space_operations ecryptfs_aops = {
/*
* XXX: This is pretty broken for multiple reasons: ecryptfs does not
* actually use buffer_heads, and ecryptfs will crash without
* CONFIG_BLOCK. But it matches the behavior before the default for
* address_space_operations without the ->dirty_folio method was
* cleaned up, so this is the best we can do without maintainer
* feedback.
*/
#ifdef CONFIG_BLOCK
.dirty_folio = block_dirty_folio,
.invalidate_folio = block_invalidate_folio,
#endif
.writepage = ecryptfs_writepage,
.read_folio = ecryptfs_read_folio,
.write_begin = ecryptfs_write_begin,
.write_end = ecryptfs_write_end,
.bmap = ecryptfs_bmap,
};
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