418 строки
12 KiB
C
418 строки
12 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* Ioctl to enable verity on a file
|
|
*
|
|
* Copyright 2019 Google LLC
|
|
*/
|
|
|
|
#include "fsverity_private.h"
|
|
|
|
#include <crypto/hash.h>
|
|
#include <linux/backing-dev.h>
|
|
#include <linux/mount.h>
|
|
#include <linux/pagemap.h>
|
|
#include <linux/sched/signal.h>
|
|
#include <linux/uaccess.h>
|
|
|
|
/*
|
|
* Read a file data page for Merkle tree construction. Do aggressive readahead,
|
|
* since we're sequentially reading the entire file.
|
|
*/
|
|
static struct page *read_file_data_page(struct file *file, pgoff_t index,
|
|
struct file_ra_state *ra,
|
|
unsigned long remaining_pages)
|
|
{
|
|
DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, index);
|
|
struct folio *folio;
|
|
|
|
folio = __filemap_get_folio(ractl.mapping, index, FGP_ACCESSED, 0);
|
|
if (!folio || !folio_test_uptodate(folio)) {
|
|
if (folio)
|
|
folio_put(folio);
|
|
else
|
|
page_cache_sync_ra(&ractl, remaining_pages);
|
|
folio = read_cache_folio(ractl.mapping, index, NULL, file);
|
|
if (IS_ERR(folio))
|
|
return &folio->page;
|
|
}
|
|
if (folio_test_readahead(folio))
|
|
page_cache_async_ra(&ractl, folio, remaining_pages);
|
|
return folio_file_page(folio, index);
|
|
}
|
|
|
|
static int build_merkle_tree_level(struct file *filp, unsigned int level,
|
|
u64 num_blocks_to_hash,
|
|
const struct merkle_tree_params *params,
|
|
u8 *pending_hashes,
|
|
struct ahash_request *req)
|
|
{
|
|
struct inode *inode = file_inode(filp);
|
|
const struct fsverity_operations *vops = inode->i_sb->s_vop;
|
|
struct file_ra_state ra = { 0 };
|
|
unsigned int pending_size = 0;
|
|
u64 dst_block_num;
|
|
u64 i;
|
|
int err;
|
|
|
|
if (WARN_ON(params->block_size != PAGE_SIZE)) /* checked earlier too */
|
|
return -EINVAL;
|
|
|
|
if (level < params->num_levels) {
|
|
dst_block_num = params->level_start[level];
|
|
} else {
|
|
if (WARN_ON(num_blocks_to_hash != 1))
|
|
return -EINVAL;
|
|
dst_block_num = 0; /* unused */
|
|
}
|
|
|
|
file_ra_state_init(&ra, filp->f_mapping);
|
|
|
|
for (i = 0; i < num_blocks_to_hash; i++) {
|
|
struct page *src_page;
|
|
|
|
if ((pgoff_t)i % 10000 == 0 || i + 1 == num_blocks_to_hash)
|
|
pr_debug("Hashing block %llu of %llu for level %u\n",
|
|
i + 1, num_blocks_to_hash, level);
|
|
|
|
if (level == 0) {
|
|
/* Leaf: hashing a data block */
|
|
src_page = read_file_data_page(filp, i, &ra,
|
|
num_blocks_to_hash - i);
|
|
if (IS_ERR(src_page)) {
|
|
err = PTR_ERR(src_page);
|
|
fsverity_err(inode,
|
|
"Error %d reading data page %llu",
|
|
err, i);
|
|
return err;
|
|
}
|
|
} else {
|
|
unsigned long num_ra_pages =
|
|
min_t(unsigned long, num_blocks_to_hash - i,
|
|
inode->i_sb->s_bdi->io_pages);
|
|
|
|
/* Non-leaf: hashing hash block from level below */
|
|
src_page = vops->read_merkle_tree_page(inode,
|
|
params->level_start[level - 1] + i,
|
|
num_ra_pages);
|
|
if (IS_ERR(src_page)) {
|
|
err = PTR_ERR(src_page);
|
|
fsverity_err(inode,
|
|
"Error %d reading Merkle tree page %llu",
|
|
err, params->level_start[level - 1] + i);
|
|
return err;
|
|
}
|
|
}
|
|
|
|
err = fsverity_hash_page(params, inode, req, src_page,
|
|
&pending_hashes[pending_size]);
|
|
put_page(src_page);
|
|
if (err)
|
|
return err;
|
|
pending_size += params->digest_size;
|
|
|
|
if (level == params->num_levels) /* Root hash? */
|
|
return 0;
|
|
|
|
if (pending_size + params->digest_size > params->block_size ||
|
|
i + 1 == num_blocks_to_hash) {
|
|
/* Flush the pending hash block */
|
|
memset(&pending_hashes[pending_size], 0,
|
|
params->block_size - pending_size);
|
|
err = vops->write_merkle_tree_block(inode,
|
|
pending_hashes,
|
|
dst_block_num,
|
|
params->log_blocksize);
|
|
if (err) {
|
|
fsverity_err(inode,
|
|
"Error %d writing Merkle tree block %llu",
|
|
err, dst_block_num);
|
|
return err;
|
|
}
|
|
dst_block_num++;
|
|
pending_size = 0;
|
|
}
|
|
|
|
if (fatal_signal_pending(current))
|
|
return -EINTR;
|
|
cond_resched();
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Build the Merkle tree for the given file using the given parameters, and
|
|
* return the root hash in @root_hash.
|
|
*
|
|
* The tree is written to a filesystem-specific location as determined by the
|
|
* ->write_merkle_tree_block() method. However, the blocks that comprise the
|
|
* tree are the same for all filesystems.
|
|
*/
|
|
static int build_merkle_tree(struct file *filp,
|
|
const struct merkle_tree_params *params,
|
|
u8 *root_hash)
|
|
{
|
|
struct inode *inode = file_inode(filp);
|
|
u8 *pending_hashes;
|
|
struct ahash_request *req;
|
|
u64 blocks;
|
|
unsigned int level;
|
|
int err = -ENOMEM;
|
|
|
|
if (inode->i_size == 0) {
|
|
/* Empty file is a special case; root hash is all 0's */
|
|
memset(root_hash, 0, params->digest_size);
|
|
return 0;
|
|
}
|
|
|
|
/* This allocation never fails, since it's mempool-backed. */
|
|
req = fsverity_alloc_hash_request(params->hash_alg, GFP_KERNEL);
|
|
|
|
pending_hashes = kmalloc(params->block_size, GFP_KERNEL);
|
|
if (!pending_hashes)
|
|
goto out;
|
|
|
|
/*
|
|
* Build each level of the Merkle tree, starting at the leaf level
|
|
* (level 0) and ascending to the root node (level 'num_levels - 1').
|
|
* Then at the end (level 'num_levels'), calculate the root hash.
|
|
*/
|
|
blocks = ((u64)inode->i_size + params->block_size - 1) >>
|
|
params->log_blocksize;
|
|
for (level = 0; level <= params->num_levels; level++) {
|
|
err = build_merkle_tree_level(filp, level, blocks, params,
|
|
pending_hashes, req);
|
|
if (err)
|
|
goto out;
|
|
blocks = (blocks + params->hashes_per_block - 1) >>
|
|
params->log_arity;
|
|
}
|
|
memcpy(root_hash, pending_hashes, params->digest_size);
|
|
err = 0;
|
|
out:
|
|
kfree(pending_hashes);
|
|
fsverity_free_hash_request(params->hash_alg, req);
|
|
return err;
|
|
}
|
|
|
|
static int enable_verity(struct file *filp,
|
|
const struct fsverity_enable_arg *arg)
|
|
{
|
|
struct inode *inode = file_inode(filp);
|
|
const struct fsverity_operations *vops = inode->i_sb->s_vop;
|
|
struct merkle_tree_params params = { };
|
|
struct fsverity_descriptor *desc;
|
|
size_t desc_size = struct_size(desc, signature, arg->sig_size);
|
|
struct fsverity_info *vi;
|
|
int err;
|
|
|
|
/* Start initializing the fsverity_descriptor */
|
|
desc = kzalloc(desc_size, GFP_KERNEL);
|
|
if (!desc)
|
|
return -ENOMEM;
|
|
desc->version = 1;
|
|
desc->hash_algorithm = arg->hash_algorithm;
|
|
desc->log_blocksize = ilog2(arg->block_size);
|
|
|
|
/* Get the salt if the user provided one */
|
|
if (arg->salt_size &&
|
|
copy_from_user(desc->salt, u64_to_user_ptr(arg->salt_ptr),
|
|
arg->salt_size)) {
|
|
err = -EFAULT;
|
|
goto out;
|
|
}
|
|
desc->salt_size = arg->salt_size;
|
|
|
|
/* Get the signature if the user provided one */
|
|
if (arg->sig_size &&
|
|
copy_from_user(desc->signature, u64_to_user_ptr(arg->sig_ptr),
|
|
arg->sig_size)) {
|
|
err = -EFAULT;
|
|
goto out;
|
|
}
|
|
desc->sig_size = cpu_to_le32(arg->sig_size);
|
|
|
|
desc->data_size = cpu_to_le64(inode->i_size);
|
|
|
|
/* Prepare the Merkle tree parameters */
|
|
err = fsverity_init_merkle_tree_params(¶ms, inode,
|
|
arg->hash_algorithm,
|
|
desc->log_blocksize,
|
|
desc->salt, desc->salt_size);
|
|
if (err)
|
|
goto out;
|
|
|
|
/*
|
|
* Start enabling verity on this file, serialized by the inode lock.
|
|
* Fail if verity is already enabled or is already being enabled.
|
|
*/
|
|
inode_lock(inode);
|
|
if (IS_VERITY(inode))
|
|
err = -EEXIST;
|
|
else
|
|
err = vops->begin_enable_verity(filp);
|
|
inode_unlock(inode);
|
|
if (err)
|
|
goto out;
|
|
|
|
/*
|
|
* Build the Merkle tree. Don't hold the inode lock during this, since
|
|
* on huge files this may take a very long time and we don't want to
|
|
* force unrelated syscalls like chown() to block forever. We don't
|
|
* need the inode lock here because deny_write_access() already prevents
|
|
* the file from being written to or truncated, and we still serialize
|
|
* ->begin_enable_verity() and ->end_enable_verity() using the inode
|
|
* lock and only allow one process to be here at a time on a given file.
|
|
*/
|
|
pr_debug("Building Merkle tree...\n");
|
|
BUILD_BUG_ON(sizeof(desc->root_hash) < FS_VERITY_MAX_DIGEST_SIZE);
|
|
err = build_merkle_tree(filp, ¶ms, desc->root_hash);
|
|
if (err) {
|
|
fsverity_err(inode, "Error %d building Merkle tree", err);
|
|
goto rollback;
|
|
}
|
|
pr_debug("Done building Merkle tree. Root hash is %s:%*phN\n",
|
|
params.hash_alg->name, params.digest_size, desc->root_hash);
|
|
|
|
/*
|
|
* Create the fsverity_info. Don't bother trying to save work by
|
|
* reusing the merkle_tree_params from above. Instead, just create the
|
|
* fsverity_info from the fsverity_descriptor as if it were just loaded
|
|
* from disk. This is simpler, and it serves as an extra check that the
|
|
* metadata we're writing is valid before actually enabling verity.
|
|
*/
|
|
vi = fsverity_create_info(inode, desc);
|
|
if (IS_ERR(vi)) {
|
|
err = PTR_ERR(vi);
|
|
goto rollback;
|
|
}
|
|
|
|
if (arg->sig_size)
|
|
pr_debug("Storing a %u-byte PKCS#7 signature alongside the file\n",
|
|
arg->sig_size);
|
|
|
|
/*
|
|
* Tell the filesystem to finish enabling verity on the file.
|
|
* Serialized with ->begin_enable_verity() by the inode lock.
|
|
*/
|
|
inode_lock(inode);
|
|
err = vops->end_enable_verity(filp, desc, desc_size, params.tree_size);
|
|
inode_unlock(inode);
|
|
if (err) {
|
|
fsverity_err(inode, "%ps() failed with err %d",
|
|
vops->end_enable_verity, err);
|
|
fsverity_free_info(vi);
|
|
} else if (WARN_ON(!IS_VERITY(inode))) {
|
|
err = -EINVAL;
|
|
fsverity_free_info(vi);
|
|
} else {
|
|
/* Successfully enabled verity */
|
|
|
|
/*
|
|
* Readers can start using ->i_verity_info immediately, so it
|
|
* can't be rolled back once set. So don't set it until just
|
|
* after the filesystem has successfully enabled verity.
|
|
*/
|
|
fsverity_set_info(inode, vi);
|
|
}
|
|
out:
|
|
kfree(params.hashstate);
|
|
kfree(desc);
|
|
return err;
|
|
|
|
rollback:
|
|
inode_lock(inode);
|
|
(void)vops->end_enable_verity(filp, NULL, 0, params.tree_size);
|
|
inode_unlock(inode);
|
|
goto out;
|
|
}
|
|
|
|
/**
|
|
* fsverity_ioctl_enable() - enable verity on a file
|
|
* @filp: file to enable verity on
|
|
* @uarg: user pointer to fsverity_enable_arg
|
|
*
|
|
* Enable fs-verity on a file. See the "FS_IOC_ENABLE_VERITY" section of
|
|
* Documentation/filesystems/fsverity.rst for the documentation.
|
|
*
|
|
* Return: 0 on success, -errno on failure
|
|
*/
|
|
int fsverity_ioctl_enable(struct file *filp, const void __user *uarg)
|
|
{
|
|
struct inode *inode = file_inode(filp);
|
|
struct fsverity_enable_arg arg;
|
|
int err;
|
|
|
|
if (copy_from_user(&arg, uarg, sizeof(arg)))
|
|
return -EFAULT;
|
|
|
|
if (arg.version != 1)
|
|
return -EINVAL;
|
|
|
|
if (arg.__reserved1 ||
|
|
memchr_inv(arg.__reserved2, 0, sizeof(arg.__reserved2)))
|
|
return -EINVAL;
|
|
|
|
if (arg.block_size != PAGE_SIZE)
|
|
return -EINVAL;
|
|
|
|
if (arg.salt_size > sizeof_field(struct fsverity_descriptor, salt))
|
|
return -EMSGSIZE;
|
|
|
|
if (arg.sig_size > FS_VERITY_MAX_SIGNATURE_SIZE)
|
|
return -EMSGSIZE;
|
|
|
|
/*
|
|
* Require a regular file with write access. But the actual fd must
|
|
* still be readonly so that we can lock out all writers. This is
|
|
* needed to guarantee that no writable fds exist to the file once it
|
|
* has verity enabled, and to stabilize the data being hashed.
|
|
*/
|
|
|
|
err = file_permission(filp, MAY_WRITE);
|
|
if (err)
|
|
return err;
|
|
|
|
if (IS_APPEND(inode))
|
|
return -EPERM;
|
|
|
|
if (S_ISDIR(inode->i_mode))
|
|
return -EISDIR;
|
|
|
|
if (!S_ISREG(inode->i_mode))
|
|
return -EINVAL;
|
|
|
|
err = mnt_want_write_file(filp);
|
|
if (err) /* -EROFS */
|
|
return err;
|
|
|
|
err = deny_write_access(filp);
|
|
if (err) /* -ETXTBSY */
|
|
goto out_drop_write;
|
|
|
|
err = enable_verity(filp, &arg);
|
|
if (err)
|
|
goto out_allow_write_access;
|
|
|
|
/*
|
|
* Some pages of the file may have been evicted from pagecache after
|
|
* being used in the Merkle tree construction, then read into pagecache
|
|
* again by another process reading from the file concurrently. Since
|
|
* these pages didn't undergo verification against the file digest which
|
|
* fs-verity now claims to be enforcing, we have to wipe the pagecache
|
|
* to ensure that all future reads are verified.
|
|
*/
|
|
filemap_write_and_wait(inode->i_mapping);
|
|
invalidate_inode_pages2(inode->i_mapping);
|
|
|
|
/*
|
|
* allow_write_access() is needed to pair with deny_write_access().
|
|
* Regardless, the filesystem won't allow writing to verity files.
|
|
*/
|
|
out_allow_write_access:
|
|
allow_write_access(filp);
|
|
out_drop_write:
|
|
mnt_drop_write_file(filp);
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL_GPL(fsverity_ioctl_enable);
|