/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
extern "C" {
#include <squashfs_utils.h>
#include <ext4_sb.h>
}
#if defined(__linux__)
#include <linux/fs.h>
#elif defined(__APPLE__)
#include <sys/disk.h>
#define BLKGETSIZE64 DKIOCGETBLOCKCOUNT
#define fdatasync(fd) fcntl((fd), F_FULLFSYNC)
#endif
#include "fec_private.h"
/* used by `find_offset'; returns metadata size for a file size `size' and
`roots' Reed-Solomon parity bytes */
using size_func = uint64_t (*)(uint64_t size, int roots);
/* performs a binary search to find a metadata offset from a file so that
the metadata size matches function `get_real_size(size, roots)', using
the approximate size returned by `get_appr_size' as a starting point */
static int find_offset(uint64_t file_size, int roots, uint64_t *offset,
size_func get_appr_size, size_func get_real_size)
{
check(offset);
check(get_appr_size);
check(get_real_size);
if (file_size % FEC_BLOCKSIZE) {
/* must be a multiple of block size */
error("file size not multiple of " stringify(FEC_BLOCKSIZE));
errno = EINVAL;
return -1;
}
uint64_t mi = get_appr_size(file_size, roots);
uint64_t lo = file_size - mi * 2;
uint64_t hi = file_size - mi / 2;
while (lo < hi) {
mi = ((hi + lo) / (2 * FEC_BLOCKSIZE)) * FEC_BLOCKSIZE;
uint64_t total = mi + get_real_size(mi, roots);
if (total < file_size) {
lo = mi + FEC_BLOCKSIZE;
} else if (total > file_size) {
hi = mi;
} else {
*offset = mi;
debug("file_size = %" PRIu64 " -> offset = %" PRIu64, file_size,
mi);
return 0;
}
}
warn("could not determine offset");
errno = ERANGE;
return -1;
}
/* returns verity metadata size for a `size' byte file */
static uint64_t get_verity_size(uint64_t size, int)
{
return VERITY_METADATA_SIZE + verity_get_size(size, NULL, NULL);
}
/* computes the verity metadata offset for a file with size `f->size' */
static int find_verity_offset(fec_handle *f, uint64_t *offset)
{
check(f);
check(offset);
return find_offset(f->data_size, 0, offset, get_verity_size,
get_verity_size);
}
/* attempts to read and validate an ecc header from file position `offset' */
static int parse_ecc_header(fec_handle *f, uint64_t offset)
{
check(f);
check(f->ecc.rsn > 0 && f->ecc.rsn < FEC_RSM);
check(f->size > sizeof(fec_header));
debug("offset = %" PRIu64, offset);
if (offset > f->size - sizeof(fec_header)) {
return -1;
}
fec_header header;
/* there's obviously no ecc data at this point, so there is no need to
call fec_pread to access this data */
if (!raw_pread(f, &header, sizeof(fec_header), offset)) {
error("failed to read: %s", strerror(errno));
return -1;
}
/* move offset back to the beginning of the block for validating header */
offset -= offset % FEC_BLOCKSIZE;
if (header.magic != FEC_MAGIC) {
return -1;
}
if (header.version != FEC_VERSION) {
error("unsupported ecc version: %u", header.version);
return -1;
}
if (header.size != sizeof(fec_header)) {
error("unexpected ecc header size: %u", header.size);
return -1;
}
if (header.roots == 0 || header.roots >= FEC_RSM) {
error("invalid ecc roots: %u", header.roots);
return -1;
}
if (f->ecc.roots != (int)header.roots) {
error("unexpected number of roots: %d vs %u", f->ecc.roots,
header.roots);
return -1;
}
if (header.fec_size % header.roots ||
header.fec_size % FEC_BLOCKSIZE) {
error("inconsistent ecc size %u", header.fec_size);
return -1;
}
/* structure: data | ecc | header */
if (offset < header.fec_size ||
offset - header.fec_size != header.inp_size) {
error("unexpected input size: %" PRIu64 " vs %" PRIu64, offset,
header.inp_size);
return -1;
}
f->data_size = header.inp_size;
f->ecc.blocks = fec_div_round_up(f->data_size, FEC_BLOCKSIZE);
f->ecc.rounds = fec_div_round_up(f->ecc.blocks, f->ecc.rsn);
if (header.fec_size !=
(uint32_t)f->ecc.rounds * f->ecc.roots * FEC_BLOCKSIZE) {
error("inconsistent ecc size %u", header.fec_size);
return -1;
}
f->ecc.size = header.fec_size;
f->ecc.start = header.inp_size;
/* validate encoding data; caller may opt not to use it if invalid */
SHA256_CTX ctx;
SHA256_Init(&ctx);
uint8_t buf[FEC_BLOCKSIZE];
uint32_t n = 0;
uint32_t len = FEC_BLOCKSIZE;
while (n < f->ecc.size) {
if (len > f->ecc.size - n) {
len = f->ecc.size - n;
}
if (!raw_pread(f, buf, len, f->ecc.start + n)) {
error("failed to read ecc: %s", strerror(errno));
return -1;
}
SHA256_Update(&ctx, buf, len);
n += len;
}
uint8_t hash[SHA256_DIGEST_LENGTH];
SHA256_Final(hash, &ctx);
f->ecc.valid = !memcmp(hash, header.hash, SHA256_DIGEST_LENGTH);
if (!f->ecc.valid) {
warn("ecc data not valid");
}
return 0;
}
/* attempts to read an ecc header from `offset', and checks for a backup copy
at the end of the block if the primary header is not valid */
static int parse_ecc(fec_handle *f, uint64_t offset)
{
check(f);
check(offset % FEC_BLOCKSIZE == 0);
check(offset < UINT64_MAX - FEC_BLOCKSIZE);
/* check the primary header at the beginning of the block */
if (parse_ecc_header(f, offset) == 0) {
return 0;
}
/* check the backup header at the end of the block */
if (parse_ecc_header(f, offset + FEC_BLOCKSIZE - sizeof(fec_header)) == 0) {
warn("using backup ecc header");
return 0;
}
return -1;
}
/* reads the squashfs superblock and returns the size of the file system in
`offset' */
static int get_squashfs_size(fec_handle *f, uint64_t *offset)
{
check(f);
check(offset);
size_t sb_size = squashfs_get_sb_size();
check(sb_size <= SSIZE_MAX);
uint8_t buffer[sb_size];
if (fec_pread(f, buffer, sizeof(buffer), 0) != (ssize_t)sb_size) {
error("failed to read superblock: %s", strerror(errno));
return -1;
}
squashfs_info sq;
if (squashfs_parse_sb_buffer(buffer, &sq) < 0) {
error("failed to parse superblock: %s", strerror(errno));
return -1;
}
*offset = sq.bytes_used_4K_padded;
return 0;
}
/* reads the ext4 superblock and returns the size of the file system in
`offset' */
static int get_ext4_size(fec_handle *f, uint64_t *offset)
{
check(f);
check(f->size > 1024 + sizeof(ext4_super_block));
check(offset);
ext4_super_block sb;
if (fec_pread(f, &sb, sizeof(sb), 1024) != sizeof(sb)) {
error("failed to read superblock: %s", strerror(errno));
return -1;
}
fs_info info;
info.len = 0; /* only len is set to 0 to ask the device for real size. */
if (ext4_parse_sb(&sb, &info) != 0) {
errno = EINVAL;
return -1;
}
*offset = info.len;
return 0;
}
/* attempts to determine file system size, if no fs type is specified in
`f->flags', tries all supported types, and returns the size in `offset' */
static int get_fs_size(fec_handle *f, uint64_t *offset)
{
check(f);
check(offset);
if (f->flags & FEC_FS_EXT4) {
return get_ext4_size(f, offset);
} else if (f->flags & FEC_FS_SQUASH) {
return get_squashfs_size(f, offset);
} else {
/* try all alternatives */
int rc = get_ext4_size(f, offset);
if (rc == 0) {
debug("found ext4fs");
return rc;
}
rc = get_squashfs_size(f, offset);
if (rc == 0) {
debug("found squashfs");
}
return rc;
}
}
/* locates, validates, and loads verity metadata from `f->fd' */
static int load_verity(fec_handle *f)
{
check(f);
debug("size = %" PRIu64 ", flags = %d", f->data_size, f->flags);
uint64_t offset = f->data_size - VERITY_METADATA_SIZE;
/* verity header is at the end of the data area */
if (verity_parse_header(f, offset) == 0) {
debug("found at %" PRIu64 " (start %" PRIu64 ")", offset,
f->verity.hash_start);
return 0;
}
debug("trying legacy formats");
/* legacy format at the end of the partition */
if (find_verity_offset(f, &offset) == 0 &&
verity_parse_header(f, offset) == 0) {
debug("found at %" PRIu64 " (start %" PRIu64 ")", offset,
f->verity.hash_start);
return 0;
}
/* legacy format after the file system, but not at the end */
int rc = get_fs_size(f, &offset);
if (rc == 0) {
debug("file system size = %" PRIu64, offset);
rc = verity_parse_header(f, offset);
if (rc == 0) {
debug("found at %" PRIu64 " (start %" PRIu64 ")", offset,
f->verity.hash_start);
}
}
return rc;
}
/* locates, validates, and loads ecc data from `f->fd' */
static int load_ecc(fec_handle *f)
{
check(f);
debug("size = %" PRIu64, f->data_size);
uint64_t offset = f->data_size - FEC_BLOCKSIZE;
if (parse_ecc(f, offset) == 0) {
debug("found at %" PRIu64 " (start %" PRIu64 ")", offset,
f->ecc.start);
return 0;
}
return -1;
}
/* sets `f->size' to the size of the file or block device */
static int get_size(fec_handle *f)
{
check(f);
struct stat st;
if (fstat(f->fd, &st) == -1) {
error("fstat failed: %s", strerror(errno));
return -1;
}
if (S_ISBLK(st.st_mode)) {
debug("block device");
if (ioctl(f->fd, BLKGETSIZE64, &f->size) == -1) {
error("ioctl failed: %s", strerror(errno));
return -1;
}
} else if (S_ISREG(st.st_mode)) {
debug("file");
f->size = st.st_size;
} else {
error("unsupported type %d", (int)st.st_mode);
errno = EACCES;
return -1;
}
return 0;
}
/* clears fec_handle fiels to safe values */
static void reset_handle(fec_handle *f)
{
f->fd = -1;
f->flags = 0;
f->mode = 0;
f->errors = 0;
f->data_size = 0;
f->pos = 0;
f->size = 0;
memset(&f->ecc, 0, sizeof(f->ecc));
memset(&f->verity, 0, sizeof(f->verity));
}
/* closes and flushes `f->fd' and releases any memory allocated for `f' */
int fec_close(struct fec_handle *f)
{
check(f);
if (f->fd != -1) {
if (f->mode & O_RDWR && fdatasync(f->fd) == -1) {
warn("fdatasync failed: %s", strerror(errno));
}
TEMP_FAILURE_RETRY(close(f->fd));
}
if (f->verity.hash) {
delete[] f->verity.hash;
}
if (f->verity.salt) {
delete[] f->verity.salt;
}
if (f->verity.table) {
delete[] f->verity.table;
}
pthread_mutex_destroy(&f->mutex);
reset_handle(f);
delete f;
return 0;
}
/* populates `data' from the internal data in `f', returns a value <0 if verity
metadata is not available in `f->fd' */
int fec_verity_get_metadata(struct fec_handle *f, struct fec_verity_metadata *data)
{
check(f);
check(data);
if (!f->verity.metadata_start) {
return -1;
}
check(f->data_size < f->size);
check(f->data_size <= f->verity.hash_start);
check(f->data_size <= f->verity.metadata_start);
check(f->verity.table);
data->disabled = f->verity.disabled;
data->data_size = f->data_size;
memcpy(data->signature, f->verity.header.signature,
sizeof(data->signature));
memcpy(data->ecc_signature, f->verity.ecc_header.signature,
sizeof(data->ecc_signature));
data->table = f->verity.table;
data->table_length = f->verity.header.length;
return 0;
}
/* populates `data' from the internal data in `f', returns a value <0 if ecc
metadata is not available in `f->fd' */
int fec_ecc_get_metadata(struct fec_handle *f, struct fec_ecc_metadata *data)
{
check(f);
check(data);
if (!f->ecc.start) {
return -1;
}
check(f->data_size < f->size);
check(f->ecc.start >= f->data_size);
check(f->ecc.start < f->size);
check(f->ecc.start % FEC_BLOCKSIZE == 0)
data->valid = f->ecc.valid;
data->roots = f->ecc.roots;
data->blocks = f->ecc.blocks;
data->rounds = f->ecc.rounds;
data->start = f->ecc.start;
return 0;
}
/* populates `data' from the internal status in `f' */
int fec_get_status(struct fec_handle *f, struct fec_status *s)
{
check(f);
check(s);
s->flags = f->flags;
s->mode = f->mode;
s->errors = f->errors;
s->data_size = f->data_size;
s->size = f->size;
return 0;
}
/* opens `path' using given options and returns a fec_handle in `handle' if
successful */
int fec_open(struct fec_handle **handle, const char *path, int mode, int flags,
int roots)
{
check(path);
check(handle);
check(roots > 0 && roots < FEC_RSM);
debug("path = %s, mode = %d, flags = %d, roots = %d", path, mode, flags,
roots);
if (mode & (O_CREAT | O_TRUNC | O_EXCL | O_WRONLY)) {
/* only reading and updating existing files is supported */
error("failed to open '%s': (unsupported mode %d)", path, mode);
errno = EACCES;
return -1;
}
fec::handle f(new (std::nothrow) fec_handle, fec_close);
if (unlikely(!f)) {
error("failed to allocate file handle");
errno = ENOMEM;
return -1;
}
reset_handle(f.get());
f->mode = mode;
f->ecc.roots = roots;
f->ecc.rsn = FEC_RSM - roots;
f->flags = flags;
if (unlikely(pthread_mutex_init(&f->mutex, NULL) != 0)) {
error("failed to create a mutex: %s", strerror(errno));
return -1;
}
f->fd = TEMP_FAILURE_RETRY(open(path, mode | O_CLOEXEC));
if (f->fd == -1) {
error("failed to open '%s': %s", path, strerror(errno));
return -1;
}
if (get_size(f.get()) == -1) {
error("failed to get size for '%s': %s", path, strerror(errno));
return -1;
}
f->data_size = f->size; /* until ecc and/or verity are loaded */
if (load_ecc(f.get()) == -1) {
debug("error-correcting codes not found from '%s'", path);
}
if (load_verity(f.get()) == -1) {
debug("verity metadata not found from '%s'", path);
}
*handle = f.release();
return 0;
}