uncrypt/uncrypt.cpp - android_bootable_recovery - Gitiles

 /*
  * 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 <errno.h>
 #include <fcntl.h>
 #include <linux/fs.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/mman.h>
 #include <unistd.h>

 #define LOG_TAG "uncrypt"
 #include <log/log.h>
 #include <cutils/android_reboot.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) {
     if (TEMP_FAILURE_RETRY(lseek64(wfd, offset, SEEK_SET)) == -1) {
         ALOGE("error seeking to offset %lld: %s\n", offset, strerror(errno));
         return -1;
     }
     size_t written = 0;
     while (written < size) {
         ssize_t wrote = TEMP_FAILURE_RETRY(write(wfd, buffer + written, size - written));
         if (wrote == -1) {
             ALOGE("error writing offset %lld: %s\n", (offset + written), strerror(errno));
             return -1;
         }
         written += wrote;
     }
     return 0;
 }

 static 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 = reinterpret_cast<int*>(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), "")) {
         ALOGE("failed to get ro.hardware\n");
         return NULL;
     }

     fstab = fs_mgr_read_fstab(fstab_path);
     if (!fstab) {
         ALOGE("failed to read %s\n", fstab_path);
         return NULL;
     }

     return fstab;
 }

 static const char* find_block_device(const char* path, bool* encryptable, bool* 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.
     for (int 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 = false;
             *encryptable = false;
             if (fs_mgr_is_encryptable(v)) {
                 *encryptable = true;
                 char buffer[PROPERTY_VALUE_MAX+1];
                 if (property_get("ro.crypto.state", buffer, "") &&
                     strcmp(buffer, "encrypted") == 0) {
                     *encrypted = true;
                 }
             }
             return v->blk_device;
         }
     }

     return NULL;
 }

 // Parse the command file RECOVERY_COMMAND_FILE to find the update package
 // name. If it's on the /data partition, replace the package name with the
 // block map file name and store it temporarily in RECOVERY_COMMAND_FILE_TMP.
 // It will be renamed to RECOVERY_COMMAND_FILE if uncrypt finishes
 // successfully.
 static char* find_update_package()
 {
     FILE* f = fopen(RECOVERY_COMMAND_FILE, "r");
     if (f == NULL) {
         return NULL;
     }
     int fd = open(RECOVERY_COMMAND_FILE_TMP, O_WRONLY | O_CREAT | O_SYNC, S_IRUSR | S_IWUSR);
     if (fd < 0) {
         ALOGE("failed to open %s\n", RECOVERY_COMMAND_FILE_TMP);
         return NULL;
     }
     FILE* fo = fdopen(fd, "w");
     char* fn = NULL;
     char* line = NULL;
     size_t len = 0;
     while (getline(&line, &len, f) != -1) {
         if (strncmp(line, "--update_package=", strlen("--update_package=")) == 0) {
             fn = strdup(line + strlen("--update_package="));
             // Replace the package name with block map file if it's on /data partition.
             if (strncmp(fn, "/data/", strlen("/data/")) == 0) {
                 fputs("--update_package=@" CACHE_BLOCK_MAP "\n", fo);
                 continue;
             }
         }
         fputs(line, fo);
     }
     free(line);
     fclose(f);
     if (fsync(fd) == -1) {
         ALOGE("failed to fsync \"%s\": %s\n", RECOVERY_COMMAND_FILE_TMP, strerror(errno));
         fclose(fo);
         return NULL;
     }
     fclose(fo);

     if (fn) {
         char* newline = strchr(fn, '\n');
         if (newline) {
             *newline = 0;
         }
     }
     return fn;
 }

 static int produce_block_map(const char* path, const char* map_file, const char* blk_dev,
                              bool encrypted) {

     int mapfd = open(map_file, O_WRONLY | O_CREAT | O_SYNC, S_IRUSR | S_IWUSR);
     if (mapfd < 0) {
         ALOGE("failed to open %s\n", map_file);
         return -1;
     }
     FILE* mapf = fdopen(mapfd, "w");

     struct stat sb;
     int ret = stat(path, &sb);
     if (ret != 0) {
         ALOGE("failed to stat %s\n", path);
         return -1;
     }

     ALOGI(" block size: %ld bytes\n", (long)sb.st_blksize);

     int blocks = ((sb.st_size-1) / sb.st_blksize) + 1;
     ALOGI("  file size: %lld bytes, %d blocks\n", (long long)sb.st_size, blocks);

     int range_alloc = 1;
     int range_used = 1;
     int* ranges = reinterpret_cast<int*>(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];
     if (encrypted) {
         for (size_t i = 0; i < WINDOW_SIZE; ++i) {
             buffers[i] = reinterpret_cast<unsigned char*>(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) {
         ALOGE("failed to open fd for reading: %s\n", strerror(errno));
         return -1;
     }

     int wfd = -1;
     if (encrypted) {
         wfd = open(blk_dev, O_WRONLY | O_SYNC);
         if (wfd < 0) {
             ALOGE("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) {
                 ALOGE("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 =
                         TEMP_FAILURE_RETRY(read(fd, buffers[tail] + so_far, sb.st_blksize - so_far));
                 if (this_read == -1) {
                     ALOGE("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) {
             ALOGE("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 (int i = 0; i < range_used; ++i) {
         fprintf(mapf, "%d %d\n", ranges[i*2], ranges[i*2+1]);
     }

     if (fsync(mapfd) == -1) {
         ALOGE("failed to fsync \"%s\": %s\n", map_file, strerror(errno));
         return -1;
     }
     fclose(mapf);
     close(fd);
     if (encrypted) {
         if (fsync(wfd) == -1) {
             ALOGE("failed to fsync \"%s\": %s\n", blk_dev, strerror(errno));
             return -1;
         }
         close(wfd);
     }

     return 0;
 }

 static void wipe_misc() {
     ALOGI("removing old commands from misc");
     for (int 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_WRONLY | O_SYNC);
             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 = TEMP_FAILURE_RETRY(write(fd, zeroes, size-written));
                 if (w == -1) {
                     ALOGE("zero write failed: %s\n", strerror(errno));
                     return;
                 } else {
                     written += w;
                 }
             }
             if (fsync(fd) == -1) {
                 ALOGE("failed to fsync \"%s\": %s\n", v->blk_device, strerror(errno));
                 close(fd);
                 return;
             }
             close(fd);
         }
     }
 }

 static void reboot_to_recovery() {
     ALOGI("rebooting to recovery");
     property_set("sys.powerctl", "reboot,recovery");
     while (true) {
       pause();
     }
     ALOGE("reboot didn't succeed?");
 }

 int main(int argc, char** argv)
 {
     const char* input_path;
     const char* map_file;
     bool do_reboot = true;

     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 = false;
     } else {
         input_path = find_update_package();
         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.
             ALOGI("no recovery command file or no update package arg");
             reboot_to_recovery();
             return 1;
         }
         map_file = CACHE_BLOCK_MAP;
     }

     ALOGI("update package is %s", input_path);

     // 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) {
         ALOGE("failed to convert %s to absolute path: %s", input_path, strerror(errno));
         return 1;
     }

     if (read_fstab() == NULL) {
         return 1;
     }

     bool encryptable;
     bool encrypted;
     const char* blk_dev = find_block_device(path, &encryptable, &encrypted);
     if (blk_dev == NULL) {
         ALOGE("failed to find block device for %s", 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).
     ALOGI("encryptable: %s\n", encryptable ? "yes" : "no");
     ALOGI("  encrypted: %s\n", encrypted ? "yes" : "no");

     // Recovery supports installing packages from 3 paths: /cache,
     // /data, and /sdcard.  (On a particular device, other locations
     // may work, but those are three we actually expect.)
     //
     // On /data we want to convert the file to a block map so that we
     // can read the package without mounting the partition.  On /cache
     // and /sdcard we leave the file alone.
     if (strncmp(path, "/data/", 6) != 0) {
         // path does not start with "/data/"; leave it alone.
         unlink(RECOVERY_COMMAND_FILE_TMP);
         wipe_misc();
     } else {
         ALOGI("writing block map %s", map_file);
         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;
 }
	/*
	* 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 <errno.h>
	#include <fcntl.h>
	#include <linux/fs.h>
	#include <stdarg.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <sys/types.h>
	#include <sys/stat.h>
	#include <sys/mman.h>
	#include <unistd.h>

	#define LOG_TAG "uncrypt"
	#include <log/log.h>
	#include <cutils/android_reboot.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) {
	if (TEMP_FAILURE_RETRY(lseek64(wfd, offset, SEEK_SET)) == -1) {
	ALOGE("error seeking to offset %lld: %s\n", offset, strerror(errno));
	return -1;
	}
	size_t written = 0;
	while (written < size) {
	ssize_t wrote = TEMP_FAILURE_RETRY(write(wfd, buffer + written, size - written));
	if (wrote == -1) {
	ALOGE("error writing offset %lld: %s\n", (offset + written), strerror(errno));
	return -1;
	}
	written += wrote;
	}
	return 0;
	}

	static 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 = reinterpret_cast<int>(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), "")) {
	ALOGE("failed to get ro.hardware\n");
	return NULL;
	}

	fstab = fs_mgr_read_fstab(fstab_path);
	if (!fstab) {
	ALOGE("failed to read %s\n", fstab_path);
	return NULL;
	}

	return fstab;
	}

	static const char* find_block_device(const char* path, bool* encryptable, bool* 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.
	for (int 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 = false;
	*encryptable = false;
	if (fs_mgr_is_encryptable(v)) {
	*encryptable = true;
	char buffer[PROPERTY_VALUE_MAX+1];
	if (property_get("ro.crypto.state", buffer, "") &&
	strcmp(buffer, "encrypted") == 0) {
	*encrypted = true;
	}
	}
	return v->blk_device;
	}
	}

	return NULL;
	}

	// Parse the command file RECOVERY_COMMAND_FILE to find the update package
	// name. If it's on the /data partition, replace the package name with the
	// block map file name and store it temporarily in RECOVERY_COMMAND_FILE_TMP.
	// It will be renamed to RECOVERY_COMMAND_FILE if uncrypt finishes
	// successfully.
	static char* find_update_package()
	{
	FILE* f = fopen(RECOVERY_COMMAND_FILE, "r");
	if (f == NULL) {
	return NULL;
	}
	int fd = open(RECOVERY_COMMAND_FILE_TMP, O_WRONLY \| O_CREAT \| O_SYNC, S_IRUSR \| S_IWUSR);
	if (fd < 0) {
	ALOGE("failed to open %s\n", RECOVERY_COMMAND_FILE_TMP);
	return NULL;
	}
	FILE* fo = fdopen(fd, "w");
	char* fn = NULL;
	char* line = NULL;
	size_t len = 0;
	while (getline(&line, &len, f) != -1) {
	if (strncmp(line, "--update_package=", strlen("--update_package=")) == 0) {
	fn = strdup(line + strlen("--update_package="));
	// Replace the package name with block map file if it's on /data partition.
	if (strncmp(fn, "/data/", strlen("/data/")) == 0) {
	fputs("--update_package=@" CACHE_BLOCK_MAP "\n", fo);
	continue;
	}
	}
	fputs(line, fo);
	}
	free(line);
	fclose(f);
	if (fsync(fd) == -1) {
	ALOGE("failed to fsync \"%s\": %s\n", RECOVERY_COMMAND_FILE_TMP, strerror(errno));
	fclose(fo);
	return NULL;
	}
	fclose(fo);

	if (fn) {
	char* newline = strchr(fn, '\n');
	if (newline) {
	*newline = 0;
	}
	}
	return fn;
	}

	static int produce_block_map(const char* path, const char* map_file, const char* blk_dev,
	bool encrypted) {

	int mapfd = open(map_file, O_WRONLY \| O_CREAT \| O_SYNC, S_IRUSR \| S_IWUSR);
	if (mapfd < 0) {
	ALOGE("failed to open %s\n", map_file);
	return -1;
	}
	FILE* mapf = fdopen(mapfd, "w");

	struct stat sb;
	int ret = stat(path, &sb);
	if (ret != 0) {
	ALOGE("failed to stat %s\n", path);
	return -1;
	}

	ALOGI(" block size: %ld bytes\n", (long)sb.st_blksize);

	int blocks = ((sb.st_size-1) / sb.st_blksize) + 1;
	ALOGI(" file size: %lld bytes, %d blocks\n", (long long)sb.st_size, blocks);

	int range_alloc = 1;
	int range_used = 1;
	int* ranges = reinterpret_cast<int>(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];
	if (encrypted) {
	for (size_t i = 0; i < WINDOW_SIZE; ++i) {
	buffers[i] = reinterpret_cast<unsigned char*>(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) {
	ALOGE("failed to open fd for reading: %s\n", strerror(errno));
	return -1;
	}

	int wfd = -1;
	if (encrypted) {
	wfd = open(blk_dev, O_WRONLY \| O_SYNC);
	if (wfd < 0) {
	ALOGE("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) {
	ALOGE("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 =
	TEMP_FAILURE_RETRY(read(fd, buffers[tail] + so_far, sb.st_blksize - so_far));
	if (this_read == -1) {
	ALOGE("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) {
	ALOGE("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 (int i = 0; i < range_used; ++i) {
	fprintf(mapf, "%d %d\n", ranges[i2], ranges[i2+1]);
	}

	if (fsync(mapfd) == -1) {
	ALOGE("failed to fsync \"%s\": %s\n", map_file, strerror(errno));
	return -1;
	}
	fclose(mapf);
	close(fd);
	if (encrypted) {
	if (fsync(wfd) == -1) {
	ALOGE("failed to fsync \"%s\": %s\n", blk_dev, strerror(errno));
	return -1;
	}
	close(wfd);
	}

	return 0;
	}

	static void wipe_misc() {
	ALOGI("removing old commands from misc");
	for (int 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_WRONLY \| O_SYNC);
	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 = TEMP_FAILURE_RETRY(write(fd, zeroes, size-written));
	if (w == -1) {
	ALOGE("zero write failed: %s\n", strerror(errno));
	return;
	} else {
	written += w;
	}
	}
	if (fsync(fd) == -1) {
	ALOGE("failed to fsync \"%s\": %s\n", v->blk_device, strerror(errno));
	close(fd);
	return;
	}
	close(fd);
	}
	}
	}

	static void reboot_to_recovery() {
	ALOGI("rebooting to recovery");
	property_set("sys.powerctl", "reboot,recovery");
	while (true) {
	pause();
	}
	ALOGE("reboot didn't succeed?");
	}

	int main(int argc, char** argv)
	{
	const char* input_path;
	const char* map_file;
	bool do_reboot = true;

	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 = false;
	} else {
	input_path = find_update_package();
	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.
	ALOGI("no recovery command file or no update package arg");
	reboot_to_recovery();
	return 1;
	}
	map_file = CACHE_BLOCK_MAP;
	}

	ALOGI("update package is %s", input_path);

	// 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) {
	ALOGE("failed to convert %s to absolute path: %s", input_path, strerror(errno));
	return 1;
	}

	if (read_fstab() == NULL) {
	return 1;
	}

	bool encryptable;
	bool encrypted;
	const char* blk_dev = find_block_device(path, &encryptable, &encrypted);
	if (blk_dev == NULL) {
	ALOGE("failed to find block device for %s", 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).
	ALOGI("encryptable: %s\n", encryptable ? "yes" : "no");
	ALOGI(" encrypted: %s\n", encrypted ? "yes" : "no");

	// Recovery supports installing packages from 3 paths: /cache,
	// /data, and /sdcard. (On a particular device, other locations
	// may work, but those are three we actually expect.)
	//
	// On /data we want to convert the file to a block map so that we
	// can read the package without mounting the partition. On /cache
	// and /sdcard we leave the file alone.
	if (strncmp(path, "/data/", 6) != 0) {
	// path does not start with "/data/"; leave it alone.
	unlink(RECOVERY_COMMAND_FILE_TMP);
	wipe_misc();
	} else {
	ALOGI("writing block map %s", map_file);
	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;
	}