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Diffstat (limited to 'uncrypt/uncrypt.c')
| -rw-r--r-- | uncrypt/uncrypt.c | 382 |
1 files changed, 382 insertions, 0 deletions
diff --git a/uncrypt/uncrypt.c b/uncrypt/uncrypt.c new file mode 100644 index 000000000..7c2d99477 --- /dev/null +++ b/uncrypt/uncrypt.c @@ -0,0 +1,382 @@ +/* + * 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 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; + } +} + +const char* find_block_device(const char* path, int* encryptable, int* encrypted) +{ + // 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; + } + + struct fstab* fstab = fs_mgr_read_fstab(fstab_path); + if (!fstab) { + fprintf(stderr, "failed to read %s\n", fstab_path); + return NULL; + } + + // 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=", strlen("--update_package=")) == 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", sb.st_blksize); + + int blocks = ((sb.st_size-1) / sb.st_blksize) + 1; + printf(" file size: %lld bytes, %d blocks\n", 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, sb.st_size, 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 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; + 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; + } + } + + rename(RECOVERY_COMMAND_FILE_TMP, RECOVERY_COMMAND_FILE); + reboot_to_recovery(); + return 0; +} |