applypatch/applypatch.cpp - SHIFTPHONES/android_bootable_recovery - Gitiles

 /*
  * Copyright (C) 2008 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 "applypatch/applypatch.h"

 #include <errno.h>
 #include <fcntl.h>
 #include <libgen.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>

 #include <algorithm>
 #include <functional>
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/parseint.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 #include <openssl/sha.h>

 #include "edify/expr.h"
 #include "otautil/paths.h"
 #include "otautil/print_sha1.h"

 using namespace std::string_literals;

 static bool GenerateTarget(const Partition& target, const FileContents& source_file,
                            const Value& patch, const Value* bonus_data, bool backup_source);

 bool LoadFileContents(const std::string& filename, FileContents* file) {
   // No longer allow loading contents from eMMC partitions.
   if (android::base::StartsWith(filename, "EMMC:")) {
     return false;
   }

   std::string data;
   if (!android::base::ReadFileToString(filename, &data)) {
     PLOG(ERROR) << "Failed to read \"" << filename << "\"";
     return false;
   }

   file->data = std::vector<unsigned char>(data.begin(), data.end());
   SHA1(file->data.data(), file->data.size(), file->sha1);
   return true;
 }

 // Reads the contents of a Partition to the given FileContents buffer.
 static bool ReadPartitionToBuffer(const Partition& partition, FileContents* out,
                                   bool check_backup) {
   uint8_t expected_sha1[SHA_DIGEST_LENGTH];
   if (ParseSha1(partition.hash, expected_sha1) != 0) {
     LOG(ERROR) << "Failed to parse target hash \"" << partition.hash << "\"";
     return false;
   }

   android::base::unique_fd dev(open(partition.name.c_str(), O_RDONLY));
   if (dev == -1) {
     PLOG(ERROR) << "Failed to open eMMC partition \"" << partition << "\"";
   } else {
     std::vector<unsigned char> buffer(partition.size);
     if (!android::base::ReadFully(dev, buffer.data(), buffer.size())) {
       PLOG(ERROR) << "Failed to read " << buffer.size() << " bytes of data for partition "
                   << partition;
     } else {
       SHA1(buffer.data(), buffer.size(), out->sha1);
       if (memcmp(out->sha1, expected_sha1, SHA_DIGEST_LENGTH) == 0) {
         out->data = std::move(buffer);
         return true;
       }
     }
   }

   if (!check_backup) {
     LOG(ERROR) << "Partition contents don't have the expected checksum";
     return false;
   }

   if (LoadFileContents(Paths::Get().cache_temp_source(), out) &&
       memcmp(out->sha1, expected_sha1, SHA_DIGEST_LENGTH) == 0) {
     return true;
   }

   LOG(ERROR) << "Both of partition contents and backup don't have the expected checksum";
   return false;
 }

 bool SaveFileContents(const std::string& filename, const FileContents* file) {
   android::base::unique_fd fd(
       open(filename.c_str(), O_WRONLY | O_CREAT | O_TRUNC | O_SYNC, S_IRUSR | S_IWUSR));
   if (fd == -1) {
     PLOG(ERROR) << "Failed to open \"" << filename << "\" for write";
     return false;
   }

   if (!android::base::WriteFully(fd, file->data.data(), file->data.size())) {
     PLOG(ERROR) << "Failed to write " << file->data.size() << " bytes of data to " << filename;
     return false;
   }

   if (fsync(fd) != 0) {
     PLOG(ERROR) << "Failed to fsync \"" << filename << "\"";
     return false;
   }

   if (close(fd.release()) != 0) {
     PLOG(ERROR) << "Failed to close \"" << filename << "\"";
     return false;
   }

   return true;
 }

 // Writes a memory buffer to 'target' Partition.
 static bool WriteBufferToPartition(const FileContents& file_contents, const Partition& partition) {
   const unsigned char* data = file_contents.data.data();
   size_t len = file_contents.data.size();
   size_t start = 0;
   bool success = false;
   for (size_t attempt = 0; attempt < 2; ++attempt) {
     android::base::unique_fd fd(open(partition.name.c_str(), O_RDWR));
     if (fd == -1) {
       PLOG(ERROR) << "Failed to open \"" << partition << "\"";
       return false;
     }

     if (TEMP_FAILURE_RETRY(lseek(fd, start, SEEK_SET)) == -1) {
       PLOG(ERROR) << "Failed to seek to " << start << " on \"" << partition << "\"";
       return false;
     }

     if (!android::base::WriteFully(fd, data + start, len - start)) {
       PLOG(ERROR) << "Failed to write " << len - start << " bytes to \"" << partition << "\"";
       return false;
     }

     if (fsync(fd) != 0) {
       PLOG(ERROR) << "Failed to sync \"" << partition << "\"";
       return false;
     }
     if (close(fd.release()) != 0) {
       PLOG(ERROR) << "Failed to close \"" << partition << "\"";
       return false;
     }

     fd.reset(open(partition.name.c_str(), O_RDONLY));
     if (fd == -1) {
       PLOG(ERROR) << "Failed to reopen \"" << partition << "\" for verification";
       return false;
     }

     // Drop caches so our subsequent verification read won't just be reading the cache.
     sync();
     std::string drop_cache = "/proc/sys/vm/drop_caches";
     if (!android::base::WriteStringToFile("3\n", drop_cache)) {
       PLOG(ERROR) << "Failed to write to " << drop_cache;
     } else {
       LOG(INFO) << "  caches dropped";
     }
     sleep(1);

     // Verify.
     if (TEMP_FAILURE_RETRY(lseek(fd, 0, SEEK_SET)) == -1) {
       PLOG(ERROR) << "Failed to seek to 0 on " << partition;
       return false;
     }

     unsigned char buffer[4096];
     start = len;
     for (size_t p = 0; p < len; p += sizeof(buffer)) {
       size_t to_read = len - p;
       if (to_read > sizeof(buffer)) {
         to_read = sizeof(buffer);
       }

       if (!android::base::ReadFully(fd, buffer, to_read)) {
         PLOG(ERROR) << "Failed to verify-read " << partition << " at " << p;
         return false;
       }

       if (memcmp(buffer, data + p, to_read) != 0) {
         LOG(ERROR) << "Verification failed starting at " << p;
         start = p;
         break;
       }
     }

     if (start == len) {
       LOG(INFO) << "Verification read succeeded (attempt " << attempt + 1 << ")";
       success = true;
       break;
     }

     if (close(fd.release()) != 0) {
       PLOG(ERROR) << "Failed to close " << partition;
       return false;
     }
   }

   if (!success) {
     LOG(ERROR) << "Failed to verify after all attempts";
     return false;
   }

   sync();

   return true;
 }

 int ParseSha1(const std::string& str, uint8_t* digest) {
   const char* ps = str.c_str();
   uint8_t* pd = digest;
   for (int i = 0; i < SHA_DIGEST_LENGTH * 2; ++i, ++ps) {
     int digit;
     if (*ps >= '0' && *ps <= '9') {
       digit = *ps - '0';
     } else if (*ps >= 'a' && *ps <= 'f') {
       digit = *ps - 'a' + 10;
     } else if (*ps >= 'A' && *ps <= 'F') {
       digit = *ps - 'A' + 10;
     } else {
       return -1;
     }
     if (i % 2 == 0) {
       *pd = digit << 4;
     } else {
       *pd |= digit;
       ++pd;
     }
   }
   if (*ps != '\0') return -1;
   return 0;
 }

 bool PatchPartitionCheck(const Partition& target, const Partition& source) {
   FileContents target_file;
   FileContents source_file;
   return (ReadPartitionToBuffer(target, &target_file, false) ||
           ReadPartitionToBuffer(source, &source_file, true));
 }

 int ShowLicenses() {
   ShowBSDiffLicense();
   return 0;
 }

 bool PatchPartition(const Partition& target, const Partition& source, const Value& patch,
                     const Value* bonus, bool backup_source) {
   LOG(INFO) << "Patching " << target.name;

   // We try to load and check against the target hash first.
   FileContents target_file;
   if (ReadPartitionToBuffer(target, &target_file, false)) {
     // The early-exit case: the patch was already applied, this file has the desired hash, nothing
     // for us to do.
     LOG(INFO) << "  already " << target.hash.substr(0, 8);
     return true;
   }

   FileContents source_file;
   if (ReadPartitionToBuffer(source, &source_file, backup_source)) {
     return GenerateTarget(target, source_file, patch, bonus, backup_source);
   }

   LOG(ERROR) << "Failed to find any match";
   return false;
 }

 bool FlashPartition(const Partition& partition, const std::string& source_filename) {
   LOG(INFO) << "Flashing " << partition;

   // We try to load and check against the target hash first.
   FileContents target_file;
   if (ReadPartitionToBuffer(partition, &target_file, false)) {
     // The early-exit case: the patch was already applied, this file has the desired hash, nothing
     // for us to do.
     LOG(INFO) << "  already " << partition.hash.substr(0, 8);
     return true;
   }

   FileContents source_file;
   if (!LoadFileContents(source_filename, &source_file)) {
     LOG(ERROR) << "Failed to load source file";
     return false;
   }

   uint8_t expected_sha1[SHA_DIGEST_LENGTH];
   if (ParseSha1(partition.hash, expected_sha1) != 0) {
     LOG(ERROR) << "Failed to parse source hash \"" << partition.hash << "\"";
     return false;
   }

   if (memcmp(source_file.sha1, expected_sha1, SHA_DIGEST_LENGTH) != 0) {
     // The source doesn't have desired checksum.
     LOG(ERROR) << "source \"" << source_filename << "\" doesn't have expected SHA-1 sum";
     LOG(ERROR) << "expected: " << partition.hash.substr(0, 8)
                << ", found: " << short_sha1(source_file.sha1);
     return false;
   }
   if (!WriteBufferToPartition(source_file, partition)) {
     LOG(ERROR) << "Failed to write to " << partition;
     return false;
   }
   return true;
 }

 static bool GenerateTarget(const Partition& target, const FileContents& source_file,
                            const Value& patch, const Value* bonus_data, bool backup_source) {
   uint8_t expected_sha1[SHA_DIGEST_LENGTH];
   if (ParseSha1(target.hash, expected_sha1) != 0) {
     LOG(ERROR) << "Failed to parse target hash \"" << target.hash << "\"";
     return false;
   }

   if (patch.type != Value::Type::BLOB) {
     LOG(ERROR) << "patch is not a blob";
     return false;
   }

   const char* header = patch.data.data();
   size_t header_bytes_read = patch.data.size();
   bool use_bsdiff = false;
   if (header_bytes_read >= 8 && memcmp(header, "BSDIFF40", 8) == 0) {
     use_bsdiff = true;
   } else if (header_bytes_read >= 8 && memcmp(header, "IMGDIFF2", 8) == 0) {
     use_bsdiff = false;
   } else {
     LOG(ERROR) << "Unknown patch file format";
     return false;
   }

   // We write the original source to cache, in case the partition write is interrupted.
   if (backup_source && !CheckAndFreeSpaceOnCache(source_file.data.size())) {
     LOG(ERROR) << "Not enough free space on /cache";
     return false;
   }
   if (backup_source && !SaveFileContents(Paths::Get().cache_temp_source(), &source_file)) {
     LOG(ERROR) << "Failed to back up source file";
     return false;
   }

   // We store the decoded output in memory.
   FileContents patched;
   SHA_CTX ctx;
   SHA1_Init(&ctx);
   SinkFn sink = [&patched, &ctx](const unsigned char* data, size_t len) {
     SHA1_Update(&ctx, data, len);
     patched.data.insert(patched.data.end(), data, data + len);
     return len;
   };

   int result;
   if (use_bsdiff) {
     result = ApplyBSDiffPatch(source_file.data.data(), source_file.data.size(), patch, 0, sink);
   } else {
     result =
         ApplyImagePatch(source_file.data.data(), source_file.data.size(), patch, sink, bonus_data);
   }

   if (result != 0) {
     LOG(ERROR) << "Failed to apply the patch: " << result;
     return false;
   }

   SHA1_Final(patched.sha1, &ctx);
   if (memcmp(patched.sha1, expected_sha1, SHA_DIGEST_LENGTH) != 0) {
     LOG(ERROR) << "Patching did not produce the expected SHA-1 of " << short_sha1(expected_sha1);

     LOG(ERROR) << "target size " << patched.data.size() << " SHA-1 " << short_sha1(patched.sha1);
     LOG(ERROR) << "source size " << source_file.data.size() << " SHA-1 "
                << short_sha1(source_file.sha1);

     uint8_t patch_digest[SHA_DIGEST_LENGTH];
     SHA1(reinterpret_cast<const uint8_t*>(patch.data.data()), patch.data.size(), patch_digest);
     LOG(ERROR) << "patch size " << patch.data.size() << " SHA-1 " << short_sha1(patch_digest);

     if (bonus_data != nullptr) {
       uint8_t bonus_digest[SHA_DIGEST_LENGTH];
       SHA1(reinterpret_cast<const uint8_t*>(bonus_data->data.data()), bonus_data->data.size(),
            bonus_digest);
       LOG(ERROR) << "bonus size " << bonus_data->data.size() << " SHA-1 "
                  << short_sha1(bonus_digest);
     }

     return false;
   }

   LOG(INFO) << "  now " << short_sha1(expected_sha1);

   // Write back the temp file to the partition.
   if (!WriteBufferToPartition(patched, target)) {
     LOG(ERROR) << "Failed to write patched data to " << target.name;
     return false;
   }

   // Delete the backup copy of the source.
   if (backup_source) {
     unlink(Paths::Get().cache_temp_source().c_str());
   }

   // Success!
   return true;
 }

 bool CheckPartition(const Partition& partition) {
   FileContents target_file;
   return ReadPartitionToBuffer(partition, &target_file, false);
 }

 Partition Partition::Parse(const std::string& input_str, std::string* err) {
   std::vector<std::string> pieces = android::base::Split(input_str, ":");
   if (pieces.size() != 4 || pieces[0] != "EMMC") {
     *err = "Invalid number of tokens or non-eMMC target";
     return {};
   }

   size_t size;
   if (!android::base::ParseUint(pieces[2], &size) || size == 0) {
     *err = "Failed to parse \"" + pieces[2] + "\" as byte count";
     return {};
   }

   return Partition(pieces[1], size, pieces[3]);
 }

 std::string Partition::ToString() const {
   if (*this) {
     return "EMMC:"s + name + ":" + std::to_string(size) + ":" + hash;
   }
   return "<invalid-partition>";
 }

 std::ostream& operator<<(std::ostream& os, const Partition& partition) {
   os << partition.ToString();
   return os;
 }
	/*
	* Copyright (C) 2008 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 "applypatch/applypatch.h"

	#include <errno.h>
	#include <fcntl.h>
	#include <libgen.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <sys/stat.h>
	#include <sys/types.h>
	#include <unistd.h>

	#include <algorithm>
	#include <functional>
	#include <memory>
	#include <string>
	#include <utility>
	#include <vector>

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <android-base/parseint.h>
	#include <android-base/strings.h>
	#include <android-base/unique_fd.h>
	#include <openssl/sha.h>

	#include "edify/expr.h"
	#include "otautil/paths.h"
	#include "otautil/print_sha1.h"

	using namespace std::string_literals;

	static bool GenerateTarget(const Partition& target, const FileContents& source_file,
	const Value& patch, const Value* bonus_data, bool backup_source);

	bool LoadFileContents(const std::string& filename, FileContents* file) {
	// No longer allow loading contents from eMMC partitions.
	if (android::base::StartsWith(filename, "EMMC:")) {
	return false;
	}

	std::string data;
	if (!android::base::ReadFileToString(filename, &data)) {
	PLOG(ERROR) << "Failed to read \"" << filename << "\"";
	return false;
	}

	file->data = std::vector<unsigned char>(data.begin(), data.end());
	SHA1(file->data.data(), file->data.size(), file->sha1);
	return true;
	}

	// Reads the contents of a Partition to the given FileContents buffer.
	static bool ReadPartitionToBuffer(const Partition& partition, FileContents* out,
	bool check_backup) {
	uint8_t expected_sha1[SHA_DIGEST_LENGTH];
	if (ParseSha1(partition.hash, expected_sha1) != 0) {
	LOG(ERROR) << "Failed to parse target hash \"" << partition.hash << "\"";
	return false;
	}

	android::base::unique_fd dev(open(partition.name.c_str(), O_RDONLY));
	if (dev == -1) {
	PLOG(ERROR) << "Failed to open eMMC partition \"" << partition << "\"";
	} else {
	std::vector<unsigned char> buffer(partition.size);
	if (!android::base::ReadFully(dev, buffer.data(), buffer.size())) {
	PLOG(ERROR) << "Failed to read " << buffer.size() << " bytes of data for partition "
	<< partition;
	} else {
	SHA1(buffer.data(), buffer.size(), out->sha1);
	if (memcmp(out->sha1, expected_sha1, SHA_DIGEST_LENGTH) == 0) {
	out->data = std::move(buffer);
	return true;
	}
	}
	}

	if (!check_backup) {
	LOG(ERROR) << "Partition contents don't have the expected checksum";
	return false;
	}

	if (LoadFileContents(Paths::Get().cache_temp_source(), out) &&
	memcmp(out->sha1, expected_sha1, SHA_DIGEST_LENGTH) == 0) {
	return true;
	}

	LOG(ERROR) << "Both of partition contents and backup don't have the expected checksum";
	return false;
	}

	bool SaveFileContents(const std::string& filename, const FileContents* file) {
	android::base::unique_fd fd(
	open(filename.c_str(), O_WRONLY \| O_CREAT \| O_TRUNC \| O_SYNC, S_IRUSR \| S_IWUSR));
	if (fd == -1) {
	PLOG(ERROR) << "Failed to open \"" << filename << "\" for write";
	return false;
	}

	if (!android::base::WriteFully(fd, file->data.data(), file->data.size())) {
	PLOG(ERROR) << "Failed to write " << file->data.size() << " bytes of data to " << filename;
	return false;
	}

	if (fsync(fd) != 0) {
	PLOG(ERROR) << "Failed to fsync \"" << filename << "\"";
	return false;
	}

	if (close(fd.release()) != 0) {
	PLOG(ERROR) << "Failed to close \"" << filename << "\"";
	return false;
	}

	return true;
	}

	// Writes a memory buffer to 'target' Partition.
	static bool WriteBufferToPartition(const FileContents& file_contents, const Partition& partition) {
	const unsigned char* data = file_contents.data.data();
	size_t len = file_contents.data.size();
	size_t start = 0;
	bool success = false;
	for (size_t attempt = 0; attempt < 2; ++attempt) {
	android::base::unique_fd fd(open(partition.name.c_str(), O_RDWR));
	if (fd == -1) {
	PLOG(ERROR) << "Failed to open \"" << partition << "\"";
	return false;
	}

	if (TEMP_FAILURE_RETRY(lseek(fd, start, SEEK_SET)) == -1) {
	PLOG(ERROR) << "Failed to seek to " << start << " on \"" << partition << "\"";
	return false;
	}

	if (!android::base::WriteFully(fd, data + start, len - start)) {
	PLOG(ERROR) << "Failed to write " << len - start << " bytes to \"" << partition << "\"";
	return false;
	}

	if (fsync(fd) != 0) {
	PLOG(ERROR) << "Failed to sync \"" << partition << "\"";
	return false;
	}
	if (close(fd.release()) != 0) {
	PLOG(ERROR) << "Failed to close \"" << partition << "\"";
	return false;
	}

	fd.reset(open(partition.name.c_str(), O_RDONLY));
	if (fd == -1) {
	PLOG(ERROR) << "Failed to reopen \"" << partition << "\" for verification";
	return false;
	}

	// Drop caches so our subsequent verification read won't just be reading the cache.
	sync();
	std::string drop_cache = "/proc/sys/vm/drop_caches";
	if (!android::base::WriteStringToFile("3\n", drop_cache)) {
	PLOG(ERROR) << "Failed to write to " << drop_cache;
	} else {
	LOG(INFO) << " caches dropped";
	}
	sleep(1);

	// Verify.
	if (TEMP_FAILURE_RETRY(lseek(fd, 0, SEEK_SET)) == -1) {
	PLOG(ERROR) << "Failed to seek to 0 on " << partition;
	return false;
	}

	unsigned char buffer[4096];
	start = len;
	for (size_t p = 0; p < len; p += sizeof(buffer)) {
	size_t to_read = len - p;
	if (to_read > sizeof(buffer)) {
	to_read = sizeof(buffer);
	}

	if (!android::base::ReadFully(fd, buffer, to_read)) {
	PLOG(ERROR) << "Failed to verify-read " << partition << " at " << p;
	return false;
	}

	if (memcmp(buffer, data + p, to_read) != 0) {
	LOG(ERROR) << "Verification failed starting at " << p;
	start = p;
	break;
	}
	}

	if (start == len) {
	LOG(INFO) << "Verification read succeeded (attempt " << attempt + 1 << ")";
	success = true;
	break;
	}

	if (close(fd.release()) != 0) {
	PLOG(ERROR) << "Failed to close " << partition;
	return false;
	}
	}

	if (!success) {
	LOG(ERROR) << "Failed to verify after all attempts";
	return false;
	}

	sync();

	return true;
	}

	int ParseSha1(const std::string& str, uint8_t* digest) {
	const char* ps = str.c_str();
	uint8_t* pd = digest;
	for (int i = 0; i < SHA_DIGEST_LENGTH * 2; ++i, ++ps) {
	int digit;
	if (ps >= '0' && ps <= '9') {
	digit = *ps - '0';
	} else if (ps >= 'a' && ps <= 'f') {
	digit = *ps - 'a' + 10;
	} else if (ps >= 'A' && ps <= 'F') {
	digit = *ps - 'A' + 10;
	} else {
	return -1;
	}
	if (i % 2 == 0) {
	*pd = digit << 4;
	} else {
	*pd \|= digit;
	++pd;
	}
	}
	if (*ps != '\0') return -1;
	return 0;
	}

	bool PatchPartitionCheck(const Partition& target, const Partition& source) {
	FileContents target_file;
	FileContents source_file;
	return (ReadPartitionToBuffer(target, &target_file, false) \|\|
	ReadPartitionToBuffer(source, &source_file, true));
	}

	int ShowLicenses() {
	ShowBSDiffLicense();
	return 0;
	}

	bool PatchPartition(const Partition& target, const Partition& source, const Value& patch,
	const Value* bonus, bool backup_source) {
	LOG(INFO) << "Patching " << target.name;

	// We try to load and check against the target hash first.
	FileContents target_file;
	if (ReadPartitionToBuffer(target, &target_file, false)) {
	// The early-exit case: the patch was already applied, this file has the desired hash, nothing
	// for us to do.
	LOG(INFO) << " already " << target.hash.substr(0, 8);
	return true;
	}

	FileContents source_file;
	if (ReadPartitionToBuffer(source, &source_file, backup_source)) {
	return GenerateTarget(target, source_file, patch, bonus, backup_source);
	}

	LOG(ERROR) << "Failed to find any match";
	return false;
	}

	bool FlashPartition(const Partition& partition, const std::string& source_filename) {
	LOG(INFO) << "Flashing " << partition;

	// We try to load and check against the target hash first.
	FileContents target_file;
	if (ReadPartitionToBuffer(partition, &target_file, false)) {
	// The early-exit case: the patch was already applied, this file has the desired hash, nothing
	// for us to do.
	LOG(INFO) << " already " << partition.hash.substr(0, 8);
	return true;
	}

	FileContents source_file;
	if (!LoadFileContents(source_filename, &source_file)) {
	LOG(ERROR) << "Failed to load source file";
	return false;
	}

	uint8_t expected_sha1[SHA_DIGEST_LENGTH];
	if (ParseSha1(partition.hash, expected_sha1) != 0) {
	LOG(ERROR) << "Failed to parse source hash \"" << partition.hash << "\"";
	return false;
	}

	if (memcmp(source_file.sha1, expected_sha1, SHA_DIGEST_LENGTH) != 0) {
	// The source doesn't have desired checksum.
	LOG(ERROR) << "source \"" << source_filename << "\" doesn't have expected SHA-1 sum";
	LOG(ERROR) << "expected: " << partition.hash.substr(0, 8)
	<< ", found: " << short_sha1(source_file.sha1);
	return false;
	}
	if (!WriteBufferToPartition(source_file, partition)) {
	LOG(ERROR) << "Failed to write to " << partition;
	return false;
	}
	return true;
	}

	static bool GenerateTarget(const Partition& target, const FileContents& source_file,
	const Value& patch, const Value* bonus_data, bool backup_source) {
	uint8_t expected_sha1[SHA_DIGEST_LENGTH];
	if (ParseSha1(target.hash, expected_sha1) != 0) {
	LOG(ERROR) << "Failed to parse target hash \"" << target.hash << "\"";
	return false;
	}

	if (patch.type != Value::Type::BLOB) {
	LOG(ERROR) << "patch is not a blob";
	return false;
	}

	const char* header = patch.data.data();
	size_t header_bytes_read = patch.data.size();
	bool use_bsdiff = false;
	if (header_bytes_read >= 8 && memcmp(header, "BSDIFF40", 8) == 0) {
	use_bsdiff = true;
	} else if (header_bytes_read >= 8 && memcmp(header, "IMGDIFF2", 8) == 0) {
	use_bsdiff = false;
	} else {
	LOG(ERROR) << "Unknown patch file format";
	return false;
	}

	// We write the original source to cache, in case the partition write is interrupted.
	if (backup_source && !CheckAndFreeSpaceOnCache(source_file.data.size())) {
	LOG(ERROR) << "Not enough free space on /cache";
	return false;
	}
	if (backup_source && !SaveFileContents(Paths::Get().cache_temp_source(), &source_file)) {
	LOG(ERROR) << "Failed to back up source file";
	return false;
	}

	// We store the decoded output in memory.
	FileContents patched;
	SHA_CTX ctx;
	SHA1_Init(&ctx);
	SinkFn sink = [&patched, &ctx](const unsigned char* data, size_t len) {
	SHA1_Update(&ctx, data, len);
	patched.data.insert(patched.data.end(), data, data + len);
	return len;
	};

	int result;
	if (use_bsdiff) {
	result = ApplyBSDiffPatch(source_file.data.data(), source_file.data.size(), patch, 0, sink);
	} else {
	result =
	ApplyImagePatch(source_file.data.data(), source_file.data.size(), patch, sink, bonus_data);
	}

	if (result != 0) {
	LOG(ERROR) << "Failed to apply the patch: " << result;
	return false;
	}

	SHA1_Final(patched.sha1, &ctx);
	if (memcmp(patched.sha1, expected_sha1, SHA_DIGEST_LENGTH) != 0) {
	LOG(ERROR) << "Patching did not produce the expected SHA-1 of " << short_sha1(expected_sha1);

	LOG(ERROR) << "target size " << patched.data.size() << " SHA-1 " << short_sha1(patched.sha1);
	LOG(ERROR) << "source size " << source_file.data.size() << " SHA-1 "
	<< short_sha1(source_file.sha1);

	uint8_t patch_digest[SHA_DIGEST_LENGTH];
	SHA1(reinterpret_cast<const uint8_t*>(patch.data.data()), patch.data.size(), patch_digest);
	LOG(ERROR) << "patch size " << patch.data.size() << " SHA-1 " << short_sha1(patch_digest);

	if (bonus_data != nullptr) {
	uint8_t bonus_digest[SHA_DIGEST_LENGTH];
	SHA1(reinterpret_cast<const uint8_t*>(bonus_data->data.data()), bonus_data->data.size(),
	bonus_digest);
	LOG(ERROR) << "bonus size " << bonus_data->data.size() << " SHA-1 "
	<< short_sha1(bonus_digest);
	}

	return false;
	}

	LOG(INFO) << " now " << short_sha1(expected_sha1);

	// Write back the temp file to the partition.
	if (!WriteBufferToPartition(patched, target)) {
	LOG(ERROR) << "Failed to write patched data to " << target.name;
	return false;
	}

	// Delete the backup copy of the source.
	if (backup_source) {
	unlink(Paths::Get().cache_temp_source().c_str());
	}

	// Success!
	return true;
	}

	bool CheckPartition(const Partition& partition) {
	FileContents target_file;
	return ReadPartitionToBuffer(partition, &target_file, false);
	}

	Partition Partition::Parse(const std::string& input_str, std::string* err) {
	std::vector<std::string> pieces = android::base::Split(input_str, ":");
	if (pieces.size() != 4 \|\| pieces[0] != "EMMC") {
	*err = "Invalid number of tokens or non-eMMC target";
	return {};
	}

	size_t size;
	if (!android::base::ParseUint(pieces[2], &size) \|\| size == 0) {
	*err = "Failed to parse \"" + pieces[2] + "\" as byte count";
	return {};
	}

	return Partition(pieces[1], size, pieces[3]);
	}

	std::string Partition::ToString() const {
	if (*this) {
	return "EMMC:"s + name + ":" + std::to_string(size) + ":" + hash;
	}
	return "<invalid-partition>";
	}

	std::ostream& operator<<(std::ostream& os, const Partition& partition) {
	os << partition.ToString();
	return os;
	}