cryptfs.cpp - platform/system/vold - Git at Google

 /*
  * Copyright (C) 2010 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 file contains the implementation of the dm-crypt volume metadata
 // encryption method, which is deprecated.  Devices that launched with Android
 // 11 or higher use a different method instead.  For details, see
 // https://source.android.com/security/encryption/metadata#configuration-on-adoptable-storage
 //

 #define LOG_TAG "Cryptfs"

 #include "cryptfs.h"

 #include "CryptoType.h"
 #include "Utils.h"

 #include <android-base/parseint.h>
 #include <android-base/properties.h>
 #include <cutils/properties.h>
 #include <libdm/dm.h>
 #include <log/log.h>

 #include <chrono>

 using android::base::ParseUint;
 using android::vold::CryptoType;
 using android::vold::KeyBuffer;
 using android::vold::KeyGeneration;
 using namespace android::dm;
 using namespace android::vold;
 using namespace std::chrono_literals;

 #define MAX_KEY_LEN 48

 #define TABLE_LOAD_RETRIES 10

 constexpr CryptoType aes_128_cbc = CryptoType()
                                            .set_config_name("AES-128-CBC")
                                            .set_kernel_name("aes-cbc-essiv:sha256")
                                            .set_keysize(16);

 constexpr CryptoType supported_crypto_types[] = {aes_128_cbc, android::vold::adiantum};

 static_assert(validateSupportedCryptoTypes(MAX_KEY_LEN, supported_crypto_types,
                                            array_length(supported_crypto_types)),
               "We have a CryptoType with keysize > MAX_KEY_LEN or which was "
               "incompletely constructed.");

 static const CryptoType& get_crypto_type() {
     // We only want to parse this read-only property once.  But we need to wait
     // until the system is initialized before we can read it.  So we use a static
     // scoped within this function to get it only once.
     static CryptoType crypto_type =
             lookup_crypto_algorithm(supported_crypto_types, array_length(supported_crypto_types),
                                     aes_128_cbc, "ro.crypto.fde_algorithm");
     return crypto_type;
 }

 const KeyGeneration cryptfs_get_keygen() {
     return KeyGeneration{get_crypto_type().get_keysize(), true, false};
 }

 /* Convert a binary key of specified length into an ascii hex string equivalent,
  * without the leading 0x and with null termination
  */
 static void convert_key_to_hex_ascii(const KeyBuffer& key, char* key_ascii) {
     unsigned int i, a;
     unsigned char nibble;

     for (i = 0, a = 0; i < key.size(); i++, a += 2) {
         /* For each byte, write out two ascii hex digits */
         nibble = (key[i] >> 4) & 0xf;
         key_ascii[a] = nibble + (nibble > 9 ? 0x37 : 0x30);

         nibble = key[i] & 0xf;
         key_ascii[a + 1] = nibble + (nibble > 9 ? 0x37 : 0x30);
     }

     /* Add the null termination */
     key_ascii[a] = '\0';
 }

 /*
  * Called by vold when it's asked to mount an encrypted external
  * storage volume. The incoming partition has no crypto header/footer,
  * as any metadata is been stored in a separate, small partition.  We
  * assume it must be using our same crypt type and keysize.
  */
 int cryptfs_setup_ext_volume(const char* label, const char* real_blkdev, const KeyBuffer& key,
                              std::string* out_crypto_blkdev) {
     auto crypto_type = get_crypto_type();
     if (key.size() != crypto_type.get_keysize()) {
         SLOGE("Raw keysize %zu does not match crypt keysize %zu", key.size(),
               crypto_type.get_keysize());
         return -1;
     }
     uint64_t nr_sec = 0;
     if (android::vold::GetBlockDev512Sectors(real_blkdev, &nr_sec) != android::OK) {
         SLOGE("Failed to get size of %s: %s", real_blkdev, strerror(errno));
         return -1;
     }

     constexpr char DM_CRYPT_SECTOR_SIZE[] = "ro.crypto.fde_sector_size";
     char value[PROPERTY_VALUE_MAX];
     unsigned int sector_size = 0;

     if (property_get(DM_CRYPT_SECTOR_SIZE, value, "") > 0) {
         if (!ParseUint(value, &sector_size) || sector_size < 512 || sector_size > 4096 ||
             (sector_size & (sector_size - 1)) != 0) {
             SLOGE("Invalid value for %s: %s.  Must be >= 512, <= 4096, and a power of 2\n",
                   DM_CRYPT_SECTOR_SIZE, value);
             return -1;
         }
     }

     // Round the crypto device size down to a crypto sector boundary.
     if (sector_size > 0) {
         nr_sec &= ~((sector_size / 512) - 1);
     }

     auto& dm = DeviceMapper::Instance();
     // We need two ASCII characters to represent each byte, and need space for
     // the '\0' terminator.
     char key_ascii[MAX_KEY_LEN * 2 + 1];
     convert_key_to_hex_ascii(key, key_ascii);

     auto target = std::make_unique<DmTargetCrypt>(0, nr_sec, crypto_type.get_kernel_name(),
                                                   key_ascii, 0, real_blkdev, 0);
     target->AllowDiscards();

     if (IsFbeEnabled() &&
         android::base::GetBoolProperty("ro.crypto.allow_encrypt_override", false)) {
         target->AllowEncryptOverride();
     }

     // Append the parameters to make dm-crypt use the specified crypto sector size.
     if (sector_size > 0) {
         target->SetSectorSize(sector_size);
         // With this option, IVs will match the sector numbering, instead
         // of being hard-coded to being based on 512-byte sectors.
         target->SetIvLargeSectors();
     }

     DmTable table;
     table.AddTarget(std::move(target));

     int load_count = 1;
     while (load_count < TABLE_LOAD_RETRIES) {
         if (dm.CreateDevice(label, table)) {
             break;
         }
         load_count++;
     }

     if (load_count >= TABLE_LOAD_RETRIES) {
         SLOGE("Cannot load dm-crypt mapping table.\n");
         return -1;
     }
     if (load_count > 1) {
         SLOGI("Took %d tries to load dmcrypt table.\n", load_count);
     }

     if (!dm.GetDmDevicePathByName(label, out_crypto_blkdev)) {
         SLOGE("Cannot determine dm-crypt path for %s.\n", label);
         return -1;
     }

     /* Ensure the dm device has been created before returning. */
     if (android::vold::WaitForFile(out_crypto_blkdev->c_str(), 1s) < 0) {
         // WaitForFile generates a suitable log message
         return -1;
     }
     return 0;
 }
	/*
	* Copyright (C) 2010 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 file contains the implementation of the dm-crypt volume metadata
	// encryption method, which is deprecated. Devices that launched with Android
	// 11 or higher use a different method instead. For details, see
	// https://source.android.com/security/encryption/metadata#configuration-on-adoptable-storage
	//

	#define LOG_TAG "Cryptfs"

	#include "cryptfs.h"

	#include "CryptoType.h"
	#include "Utils.h"

	#include <android-base/parseint.h>
	#include <android-base/properties.h>
	#include <cutils/properties.h>
	#include <libdm/dm.h>
	#include <log/log.h>

	#include <chrono>

	using android::base::ParseUint;
	using android::vold::CryptoType;
	using android::vold::KeyBuffer;
	using android::vold::KeyGeneration;
	using namespace android::dm;
	using namespace android::vold;
	using namespace std::chrono_literals;

	#define MAX_KEY_LEN 48

	#define TABLE_LOAD_RETRIES 10

	constexpr CryptoType aes_128_cbc = CryptoType()
	.set_config_name("AES-128-CBC")
	.set_kernel_name("aes-cbc-essiv:sha256")
	.set_keysize(16);

	constexpr CryptoType supported_crypto_types[] = {aes_128_cbc, android::vold::adiantum};

	static_assert(validateSupportedCryptoTypes(MAX_KEY_LEN, supported_crypto_types,
	array_length(supported_crypto_types)),
	"We have a CryptoType with keysize > MAX_KEY_LEN or which was "
	"incompletely constructed.");

	static const CryptoType& get_crypto_type() {
	// We only want to parse this read-only property once. But we need to wait
	// until the system is initialized before we can read it. So we use a static
	// scoped within this function to get it only once.
	static CryptoType crypto_type =
	lookup_crypto_algorithm(supported_crypto_types, array_length(supported_crypto_types),
	aes_128_cbc, "ro.crypto.fde_algorithm");
	return crypto_type;
	}

	const KeyGeneration cryptfs_get_keygen() {
	return KeyGeneration{get_crypto_type().get_keysize(), true, false};
	}

	/* Convert a binary key of specified length into an ascii hex string equivalent,
	* without the leading 0x and with null termination
	*/
	static void convert_key_to_hex_ascii(const KeyBuffer& key, char* key_ascii) {
	unsigned int i, a;
	unsigned char nibble;

	for (i = 0, a = 0; i < key.size(); i++, a += 2) {
	/* For each byte, write out two ascii hex digits */
	nibble = (key[i] >> 4) & 0xf;
	key_ascii[a] = nibble + (nibble > 9 ? 0x37 : 0x30);

	nibble = key[i] & 0xf;
	key_ascii[a + 1] = nibble + (nibble > 9 ? 0x37 : 0x30);
	}

	/* Add the null termination */
	key_ascii[a] = '\0';
	}

	/*
	* Called by vold when it's asked to mount an encrypted external
	* storage volume. The incoming partition has no crypto header/footer,
	* as any metadata is been stored in a separate, small partition. We
	* assume it must be using our same crypt type and keysize.
	*/
	int cryptfs_setup_ext_volume(const char* label, const char* real_blkdev, const KeyBuffer& key,
	std::string* out_crypto_blkdev) {
	auto crypto_type = get_crypto_type();
	if (key.size() != crypto_type.get_keysize()) {
	SLOGE("Raw keysize %zu does not match crypt keysize %zu", key.size(),
	crypto_type.get_keysize());
	return -1;
	}
	uint64_t nr_sec = 0;
	if (android::vold::GetBlockDev512Sectors(real_blkdev, &nr_sec) != android::OK) {
	SLOGE("Failed to get size of %s: %s", real_blkdev, strerror(errno));
	return -1;
	}

	constexpr char DM_CRYPT_SECTOR_SIZE[] = "ro.crypto.fde_sector_size";
	char value[PROPERTY_VALUE_MAX];
	unsigned int sector_size = 0;

	if (property_get(DM_CRYPT_SECTOR_SIZE, value, "") > 0) {
	if (!ParseUint(value, &sector_size) \|\| sector_size < 512 \|\| sector_size > 4096 \|\|
	(sector_size & (sector_size - 1)) != 0) {
	SLOGE("Invalid value for %s: %s. Must be >= 512, <= 4096, and a power of 2\n",
	DM_CRYPT_SECTOR_SIZE, value);
	return -1;
	}
	}

	// Round the crypto device size down to a crypto sector boundary.
	if (sector_size > 0) {
	nr_sec &= ~((sector_size / 512) - 1);
	}

	auto& dm = DeviceMapper::Instance();
	// We need two ASCII characters to represent each byte, and need space for
	// the '\0' terminator.
	char key_ascii[MAX_KEY_LEN * 2 + 1];
	convert_key_to_hex_ascii(key, key_ascii);

	auto target = std::make_unique<DmTargetCrypt>(0, nr_sec, crypto_type.get_kernel_name(),
	key_ascii, 0, real_blkdev, 0);
	target->AllowDiscards();

	if (IsFbeEnabled() &&
	android::base::GetBoolProperty("ro.crypto.allow_encrypt_override", false)) {
	target->AllowEncryptOverride();
	}

	// Append the parameters to make dm-crypt use the specified crypto sector size.
	if (sector_size > 0) {
	target->SetSectorSize(sector_size);
	// With this option, IVs will match the sector numbering, instead
	// of being hard-coded to being based on 512-byte sectors.
	target->SetIvLargeSectors();
	}

	DmTable table;
	table.AddTarget(std::move(target));

	int load_count = 1;
	while (load_count < TABLE_LOAD_RETRIES) {
	if (dm.CreateDevice(label, table)) {
	break;
	}
	load_count++;
	}

	if (load_count >= TABLE_LOAD_RETRIES) {
	SLOGE("Cannot load dm-crypt mapping table.\n");
	return -1;
	}
	if (load_count > 1) {
	SLOGI("Took %d tries to load dmcrypt table.\n", load_count);
	}

	if (!dm.GetDmDevicePathByName(label, out_crypto_blkdev)) {
	SLOGE("Cannot determine dm-crypt path for %s.\n", label);
	return -1;
	}

	/* Ensure the dm device has been created before returning. */
	if (android::vold::WaitForFile(out_crypto_blkdev->c_str(), 1s) < 0) {
	// WaitForFile generates a suitable log message
	return -1;
	}
	return 0;
	}