/*
* Copyright (C) 2014 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.
*/
// This program takes a file on an ext4 filesystem and produces a list
// of the blocks that file occupies, which enables the file contents
// to be read directly from the block device without mounting the
// filesystem.
//
// If the filesystem is using an encrypted block device, it will also
// read the file and rewrite it to the same blocks of the underlying
// (unencrypted) block device, so the file contents can be read
// without the need for the decryption key.
//
// The output of this program is a "block map" which looks like this:
//
// /dev/block/platform/msm_sdcc.1/by-name/userdata # block device
// 49652 4096 # file size in bytes, block size
// 3 # count of block ranges
// 1000 1008 # block range 0
// 2100 2102 # ... block range 1
// 30 33 # ... block range 2
//
// Each block range represents a half-open interval; the line "30 33"
// reprents the blocks [30, 31, 32].
//
// Recovery can take this block map file and retrieve the underlying
// file data to use as an update package.
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <linux/fs.h>
#include <sys/mman.h>
#include <cutils/properties.h>
#include <fs_mgr.h>
#define WINDOW_SIZE 5
#define RECOVERY_COMMAND_FILE "/cache/recovery/command"
#define RECOVERY_COMMAND_FILE_TMP "/cache/recovery/command.tmp"
#define CACHE_BLOCK_MAP "/cache/recovery/block.map"
static struct fstab* fstab = NULL;
static int write_at_offset(unsigned char* buffer, size_t size,
int wfd, off64_t offset)
{
lseek64(wfd, offset, SEEK_SET);
size_t written = 0;
while (written < size) {
ssize_t wrote = write(wfd, buffer + written, size - written);
if (wrote < 0) {
fprintf(stderr, "error writing offset %lld: %s\n", offset, strerror(errno));
return -1;
}
written += wrote;
}
return 0;
}
void add_block_to_ranges(int** ranges, int* range_alloc, int* range_used, int new_block)
{
// If the current block start is < 0, set the start to the new
// block. (This only happens for the very first block of the very
// first range.)
if ((*ranges)[*range_used*2-2] < 0) {
(*ranges)[*range_used*2-2] = new_block;
(*ranges)[*range_used*2-1] = new_block;
}
if (new_block == (*ranges)[*range_used*2-1]) {
// If the new block comes immediately after the current range,
// all we have to do is extend the current range.
++(*ranges)[*range_used*2-1];
} else {
// We need to start a new range.
// If there isn't enough room in the array, we need to expand it.
if (*range_used >= *range_alloc) {
*range_alloc *= 2;
*ranges = realloc(*ranges, *range_alloc * 2 * sizeof(int));
}
++*range_used;
(*ranges)[*range_used*2-2] = new_block;
(*ranges)[*range_used*2-1] = new_block+1;
}
}
static struct fstab* read_fstab()
{
fstab = NULL;
// The fstab path is always "/fstab.${ro.hardware}".
char fstab_path[PATH_MAX+1] = "/fstab.";
if (!property_get("ro.hardware", fstab_path+strlen(fstab_path), "")) {
fprintf(stderr, "failed to get ro.hardware\n");
return NULL;
}
fstab = fs_mgr_read_fstab(fstab_path);
if (!fstab) {
fprintf(stderr, "failed to read %s\n", fstab_path);
return NULL;
}
return fstab;
}
const char* find_block_device(const char* path, int* encryptable, int* encrypted)
{
// Look for a volume whose mount point is the prefix of path and
// return its block device. Set encrypted if it's currently
// encrypted.
int i;
for (i = 0; i < fstab->num_entries; ++i) {
struct fstab_rec* v = &fstab->recs[i];
if (!v->mount_point) continue;
int len = strlen(v->mount_point);
if (strncmp(path, v->mount_point, len) == 0 &&
(path[len] == '/' || path[len] == 0)) {
*encrypted = 0;
*encryptable = 0;
if (fs_mgr_is_encryptable(v)) {
*encryptable = 1;
char buffer[PROPERTY_VALUE_MAX+1];
if (property_get("ro.crypto.state", buffer, "") &&
strcmp(buffer, "encrypted") == 0) {
*encrypted = 1;
}
}
return v->blk_device;
}
}
return NULL;
}
char* parse_recovery_command_file()
{
char* fn = NULL;
int count = 0;
char temp[1024];
FILE* f = fopen(RECOVERY_COMMAND_FILE, "r");
if (f == NULL) {
return NULL;
}
FILE* fo = fopen(RECOVERY_COMMAND_FILE_TMP, "w");
while (fgets(temp, sizeof(temp), f)) {
printf("read: %s", temp);
if (strncmp(temp, "--update_package=/data/", strlen("--update_package=/data/")) == 0) {
fn = strdup(temp + strlen("--update_package="));
strcpy(temp, "--update_package=@" CACHE_BLOCK_MAP "\n");
}
fputs(temp, fo);
}
fclose(f);
fclose(fo);
if (fn) {
char* newline = strchr(fn, '\n');
if (newline) *newline = 0;
}
return fn;
}
int produce_block_map(const char* path, const char* map_file, const char* blk_dev,
int encrypted)
{
struct stat sb;
int ret;
FILE* mapf = fopen(map_file, "w");
ret = stat(path, &sb);
if (ret != 0) {
fprintf(stderr, "failed to stat %s\n", path);
return -1;
}
printf(" block size: %ld bytes\n", (long)sb.st_blksize);
int blocks = ((sb.st_size-1) / sb.st_blksize) + 1;
printf(" file size: %lld bytes, %d blocks\n", (long long)sb.st_size, blocks);
int* ranges;
int range_alloc = 1;
int range_used = 1;
ranges = malloc(range_alloc * 2 * sizeof(int));
ranges[0] = -1;
ranges[1] = -1;
fprintf(mapf, "%s\n%lld %lu\n", blk_dev, (long long)sb.st_size, (unsigned long)sb.st_blksize);
unsigned char* buffers[WINDOW_SIZE];
int i;
if (encrypted) {
for (i = 0; i < WINDOW_SIZE; ++i) {
buffers[i] = malloc(sb.st_blksize);
}
}
int head_block = 0;
int head = 0, tail = 0;
size_t pos = 0;
int fd = open(path, O_RDONLY);
if (fd < 0) {
fprintf(stderr, "failed to open fd for reading: %s\n", strerror(errno));
return -1;
}
fsync(fd);
int wfd = -1;
if (encrypted) {
wfd = open(blk_dev, O_WRONLY);
if (wfd < 0) {
fprintf(stderr, "failed to open fd for writing: %s\n", strerror(errno));
return -1;
}
}
while (pos < sb.st_size) {
if ((tail+1) % WINDOW_SIZE == head) {
// write out head buffer
int block = head_block;
ret = ioctl(fd, FIBMAP, &block);
if (ret != 0) {
fprintf(stderr, "failed to find block %d\n", head_block);
return -1;
}
add_block_to_ranges(&ranges, &range_alloc, &range_used, block);
if (encrypted) {
if (write_at_offset(buffers[head], sb.st_blksize, wfd, (off64_t)sb.st_blksize * block) != 0) {
return -1;
}
}
head = (head + 1) % WINDOW_SIZE;
++head_block;
}
// read next block to tail
if (encrypted) {
size_t so_far = 0;
while (so_far < sb.st_blksize && pos < sb.st_size) {
ssize_t this_read = read(fd, buffers[tail] + so_far, sb.st_blksize - so_far);
if (this_read < 0) {
fprintf(stderr, "failed to read: %s\n", strerror(errno));
return -1;
}
so_far += this_read;
pos += this_read;
}
} else {
// If we're not encrypting; we don't need to actually read
// anything, just skip pos forward as if we'd read a
// block.
pos += sb.st_blksize;
}
tail = (tail+1) % WINDOW_SIZE;
}
while (head != tail) {
// write out head buffer
int block = head_block;
ret = ioctl(fd, FIBMAP, &block);
if (ret != 0) {
fprintf(stderr, "failed to find block %d\n", head_block);
return -1;
}
add_block_to_ranges(&ranges, &range_alloc, &range_used, block);
if (encrypted) {
if (write_at_offset(buffers[head], sb.st_blksize, wfd, (off64_t)sb.st_blksize * block) != 0) {
return -1;
}
}
head = (head + 1) % WINDOW_SIZE;
++head_block;
}
fprintf(mapf, "%d\n", range_used);
for (i = 0; i < range_used; ++i) {
fprintf(mapf, "%d %d\n", ranges[i*2], ranges[i*2+1]);
}
fclose(mapf);
close(fd);
if (encrypted) {
close(wfd);
}
return 0;
}
void wipe_misc() {
int i;
for (i = 0; i < fstab->num_entries; ++i) {
struct fstab_rec* v = &fstab->recs[i];
if (!v->mount_point) continue;
if (strcmp(v->mount_point, "/misc") == 0) {
int fd = open(v->blk_device, O_RDWR);
uint8_t zeroes[1088]; // sizeof(bootloader_message) from recovery
memset(zeroes, 0, sizeof(zeroes));
size_t written = 0;
size_t size = sizeof(zeroes);
while (written < size) {
ssize_t w = write(fd, zeroes, size-written);
if (w < 0 && errno != EINTR) {
fprintf(stderr, "zero write failed: %s\n", strerror(errno));
return;
} else {
written += w;
}
}
close(fd);
}
}
}
void reboot_to_recovery() {
property_set("sys.powerctl", "reboot,recovery");
sleep(10);
}
int main(int argc, char** argv)
{
const char* input_path;
const char* map_file;
int do_reboot = 1;
if (argc != 1 && argc != 3) {
fprintf(stderr, "usage: %s [<transform_path> <map_file>]\n", argv[0]);
return 2;
}
if (argc == 3) {
// when command-line args are given this binary is being used
// for debugging; don't reboot to recovery at the end.
input_path = argv[1];
map_file = argv[2];
do_reboot = 0;
} else {
input_path = parse_recovery_command_file();
if (input_path == NULL) {
// if we're rebooting to recovery without a package (say,
// to wipe data), then we don't need to do anything before
// going to recovery.
fprintf(stderr, "no recovery command file or no update package arg");
reboot_to_recovery();
return 1;
}
map_file = CACHE_BLOCK_MAP;
}
// Turn the name of the file we're supposed to convert into an
// absolute path, so we can find what filesystem it's on.
char path[PATH_MAX+1];
if (realpath(input_path, path) == NULL) {
fprintf(stderr, "failed to convert %s to absolute path: %s\n", input_path, strerror(errno));
return 1;
}
int encryptable;
int encrypted;
if (read_fstab() == NULL) {
return 1;
}
const char* blk_dev = find_block_device(path, &encryptable, &encrypted);
if (blk_dev == NULL) {
fprintf(stderr, "failed to find block device for %s\n", path);
return 1;
}
// If the filesystem it's on isn't encrypted, we only produce the
// block map, we don't rewrite the file contents (it would be
// pointless to do so).
printf("encryptable: %s\n", encryptable ? "yes" : "no");
printf(" encrypted: %s\n", encrypted ? "yes" : "no");
if (!encryptable) {
// If the file is on a filesystem that doesn't support
// encryption (eg, /cache), then leave it alone.
//
// TODO: change this to be !encrypted -- if the file is on
// /data but /data isn't encrypted, we don't need to use the
// block map mechanism. We do for now so as to get more
// testing of it (since most dogfood devices aren't
// encrypted).
unlink(RECOVERY_COMMAND_FILE_TMP);
} else {
if (produce_block_map(path, map_file, blk_dev, encrypted) != 0) {
return 1;
}
}
wipe_misc();
rename(RECOVERY_COMMAND_FILE_TMP, RECOVERY_COMMAND_FILE);
if (do_reboot) reboot_to_recovery();
return 0;
}
