KeyUtil.cpp - platform/system/vold - Gitiles

 /*
  * Copyright (C) 2016 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 "KeyUtil.h"

 #include <iomanip>
 #include <sstream>
 #include <string>

 #include <openssl/sha.h>

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <keyutils.h>

 #include "KeyStorage.h"
 #include "Utils.h"

 namespace android {
 namespace vold {

 // ext4enc:TODO get this const from somewhere good
 const int EXT4_KEY_DESCRIPTOR_SIZE = 8;

 // ext4enc:TODO Include structure from somewhere sensible
 // MUST be in sync with ext4_crypto.c in kernel
 constexpr int EXT4_ENCRYPTION_MODE_AES_256_XTS = 1;
 constexpr int EXT4_AES_256_XTS_KEY_SIZE = 64;
 constexpr int EXT4_MAX_KEY_SIZE = 64;
 struct ext4_encryption_key {
     uint32_t mode;
     char raw[EXT4_MAX_KEY_SIZE];
     uint32_t size;
 };

 bool randomKey(KeyBuffer* key) {
     *key = KeyBuffer(EXT4_AES_256_XTS_KEY_SIZE);
     if (ReadRandomBytes(key->size(), key->data()) != 0) {
         // TODO status_t plays badly with PLOG, fix it.
         LOG(ERROR) << "Random read failed";
         return false;
     }
     return true;
 }

 // Get raw keyref - used to make keyname and to pass to ioctl
 static std::string generateKeyRef(const char* key, int length) {
     SHA512_CTX c;

     SHA512_Init(&c);
     SHA512_Update(&c, key, length);
     unsigned char key_ref1[SHA512_DIGEST_LENGTH];
     SHA512_Final(key_ref1, &c);

     SHA512_Init(&c);
     SHA512_Update(&c, key_ref1, SHA512_DIGEST_LENGTH);
     unsigned char key_ref2[SHA512_DIGEST_LENGTH];
     SHA512_Final(key_ref2, &c);

     static_assert(EXT4_KEY_DESCRIPTOR_SIZE <= SHA512_DIGEST_LENGTH,
                   "Hash too short for descriptor");
     return std::string((char*)key_ref2, EXT4_KEY_DESCRIPTOR_SIZE);
 }

 static bool fillKey(const KeyBuffer& key, ext4_encryption_key* ext4_key) {
     if (key.size() != EXT4_AES_256_XTS_KEY_SIZE) {
         LOG(ERROR) << "Wrong size key " << key.size();
         return false;
     }
     static_assert(EXT4_AES_256_XTS_KEY_SIZE <= sizeof(ext4_key->raw), "Key too long!");
     ext4_key->mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
     ext4_key->size = key.size();
     memset(ext4_key->raw, 0, sizeof(ext4_key->raw));
     memcpy(ext4_key->raw, key.data(), key.size());
     return true;
 }

 static char const* const NAME_PREFIXES[] = {"ext4", "f2fs", "fscrypt", nullptr};

 static std::string keyname(const std::string& prefix, const std::string& raw_ref) {
     std::ostringstream o;
     o << prefix << ":";
     for (unsigned char i : raw_ref) {
         o << std::hex << std::setw(2) << std::setfill('0') << (int)i;
     }
     return o.str();
 }

 // Get the keyring we store all keys in
 static bool e4cryptKeyring(key_serial_t* device_keyring) {
     *device_keyring = keyctl_search(KEY_SPEC_SESSION_KEYRING, "keyring", "e4crypt", 0);
     if (*device_keyring == -1) {
         PLOG(ERROR) << "Unable to find device keyring";
         return false;
     }
     return true;
 }

 // Install password into global keyring
 // Return raw key reference for use in policy
 bool installKey(const KeyBuffer& key, std::string* raw_ref) {
     // Place ext4_encryption_key into automatically zeroing buffer.
     KeyBuffer ext4KeyBuffer(sizeof(ext4_encryption_key));
     ext4_encryption_key& ext4_key = *reinterpret_cast<ext4_encryption_key*>(ext4KeyBuffer.data());

     if (!fillKey(key, &ext4_key)) return false;
     *raw_ref = generateKeyRef(ext4_key.raw, ext4_key.size);
     key_serial_t device_keyring;
     if (!e4cryptKeyring(&device_keyring)) return false;
     for (char const* const* name_prefix = NAME_PREFIXES; *name_prefix != nullptr; name_prefix++) {
         auto ref = keyname(*name_prefix, *raw_ref);
         key_serial_t key_id =
             add_key("logon", ref.c_str(), (void*)&ext4_key, sizeof(ext4_key), device_keyring);
         if (key_id == -1) {
             PLOG(ERROR) << "Failed to insert key into keyring " << device_keyring;
             return false;
         }
         LOG(DEBUG) << "Added key " << key_id << " (" << ref << ") to keyring " << device_keyring
                    << " in process " << getpid();
     }
     return true;
 }

 bool evictKey(const std::string& raw_ref) {
     key_serial_t device_keyring;
     if (!e4cryptKeyring(&device_keyring)) return false;
     bool success = true;
     for (char const* const* name_prefix = NAME_PREFIXES; *name_prefix != nullptr; name_prefix++) {
         auto ref = keyname(*name_prefix, raw_ref);
         auto key_serial = keyctl_search(device_keyring, "logon", ref.c_str(), 0);

         // Unlink the key from the keyring.  Prefer unlinking to revoking or
         // invalidating, since unlinking is actually no less secure currently, and
         // it avoids bugs in certain kernel versions where the keyring key is
         // referenced from places it shouldn't be.
         if (keyctl_unlink(key_serial, device_keyring) != 0) {
             PLOG(ERROR) << "Failed to unlink key with serial " << key_serial << " ref " << ref;
             success = false;
         } else {
             LOG(DEBUG) << "Unlinked key with serial " << key_serial << " ref " << ref;
         }
     }
     return success;
 }

 bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_authentication,
                            const std::string& key_path, const std::string& tmp_path,
                            std::string* key_ref) {
     KeyBuffer key;
     if (pathExists(key_path)) {
         LOG(DEBUG) << "Key exists, using: " << key_path;
         if (!retrieveKey(key_path, key_authentication, &key)) return false;
     } else {
         if (!create_if_absent) {
             LOG(ERROR) << "No key found in " << key_path;
             return false;
         }
         LOG(INFO) << "Creating new key in " << key_path;
         if (!randomKey(&key)) return false;
         if (!storeKeyAtomically(key_path, tmp_path, key_authentication, key)) return false;
     }

     if (!installKey(key, key_ref)) {
         LOG(ERROR) << "Failed to install key in " << key_path;
         return false;
     }
     return true;
 }

 bool retrieveKey(bool create_if_absent, const std::string& key_path, const std::string& tmp_path,
                  KeyBuffer* key) {
     if (pathExists(key_path)) {
         LOG(DEBUG) << "Key exists, using: " << key_path;
         if (!retrieveKey(key_path, kEmptyAuthentication, key)) return false;
     } else {
         if (!create_if_absent) {
             LOG(ERROR) << "No key found in " << key_path;
             return false;
         }
         LOG(INFO) << "Creating new key in " << key_path;
         if (!randomKey(key)) return false;
         if (!storeKeyAtomically(key_path, tmp_path, kEmptyAuthentication, *key)) return false;
     }
     return true;
 }

 }  // namespace vold
 }  // namespace android
	/*
	* Copyright (C) 2016 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 "KeyUtil.h"

	#include <iomanip>
	#include <sstream>
	#include <string>

	#include <openssl/sha.h>

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <keyutils.h>

	#include "KeyStorage.h"
	#include "Utils.h"

	namespace android {
	namespace vold {

	// ext4enc:TODO get this const from somewhere good
	const int EXT4_KEY_DESCRIPTOR_SIZE = 8;

	// ext4enc:TODO Include structure from somewhere sensible
	// MUST be in sync with ext4_crypto.c in kernel
	constexpr int EXT4_ENCRYPTION_MODE_AES_256_XTS = 1;
	constexpr int EXT4_AES_256_XTS_KEY_SIZE = 64;
	constexpr int EXT4_MAX_KEY_SIZE = 64;
	struct ext4_encryption_key {
	uint32_t mode;
	char raw[EXT4_MAX_KEY_SIZE];
	uint32_t size;
	};

	bool randomKey(KeyBuffer* key) {
	*key = KeyBuffer(EXT4_AES_256_XTS_KEY_SIZE);
	if (ReadRandomBytes(key->size(), key->data()) != 0) {
	// TODO status_t plays badly with PLOG, fix it.
	LOG(ERROR) << "Random read failed";
	return false;
	}
	return true;
	}

	// Get raw keyref - used to make keyname and to pass to ioctl
	static std::string generateKeyRef(const char* key, int length) {
	SHA512_CTX c;

	SHA512_Init(&c);
	SHA512_Update(&c, key, length);
	unsigned char key_ref1[SHA512_DIGEST_LENGTH];
	SHA512_Final(key_ref1, &c);

	SHA512_Init(&c);
	SHA512_Update(&c, key_ref1, SHA512_DIGEST_LENGTH);
	unsigned char key_ref2[SHA512_DIGEST_LENGTH];
	SHA512_Final(key_ref2, &c);

	static_assert(EXT4_KEY_DESCRIPTOR_SIZE <= SHA512_DIGEST_LENGTH,
	"Hash too short for descriptor");
	return std::string((char*)key_ref2, EXT4_KEY_DESCRIPTOR_SIZE);
	}

	static bool fillKey(const KeyBuffer& key, ext4_encryption_key* ext4_key) {
	if (key.size() != EXT4_AES_256_XTS_KEY_SIZE) {
	LOG(ERROR) << "Wrong size key " << key.size();
	return false;
	}
	static_assert(EXT4_AES_256_XTS_KEY_SIZE <= sizeof(ext4_key->raw), "Key too long!");
	ext4_key->mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
	ext4_key->size = key.size();
	memset(ext4_key->raw, 0, sizeof(ext4_key->raw));
	memcpy(ext4_key->raw, key.data(), key.size());
	return true;
	}

	static char const* const NAME_PREFIXES[] = {"ext4", "f2fs", "fscrypt", nullptr};

	static std::string keyname(const std::string& prefix, const std::string& raw_ref) {
	std::ostringstream o;
	o << prefix << ":";
	for (unsigned char i : raw_ref) {
	o << std::hex << std::setw(2) << std::setfill('0') << (int)i;
	}
	return o.str();
	}

	// Get the keyring we store all keys in
	static bool e4cryptKeyring(key_serial_t* device_keyring) {
	*device_keyring = keyctl_search(KEY_SPEC_SESSION_KEYRING, "keyring", "e4crypt", 0);
	if (*device_keyring == -1) {
	PLOG(ERROR) << "Unable to find device keyring";
	return false;
	}
	return true;
	}

	// Install password into global keyring
	// Return raw key reference for use in policy
	bool installKey(const KeyBuffer& key, std::string* raw_ref) {
	// Place ext4_encryption_key into automatically zeroing buffer.
	KeyBuffer ext4KeyBuffer(sizeof(ext4_encryption_key));
	ext4_encryption_key& ext4_key = reinterpret_cast<ext4_encryption_key>(ext4KeyBuffer.data());

	if (!fillKey(key, &ext4_key)) return false;
	*raw_ref = generateKeyRef(ext4_key.raw, ext4_key.size);
	key_serial_t device_keyring;
	if (!e4cryptKeyring(&device_keyring)) return false;
	for (char const* const* name_prefix = NAME_PREFIXES; *name_prefix != nullptr; name_prefix++) {
	auto ref = keyname(name_prefix, raw_ref);
	key_serial_t key_id =
	add_key("logon", ref.c_str(), (void*)&ext4_key, sizeof(ext4_key), device_keyring);
	if (key_id == -1) {
	PLOG(ERROR) << "Failed to insert key into keyring " << device_keyring;
	return false;
	}
	LOG(DEBUG) << "Added key " << key_id << " (" << ref << ") to keyring " << device_keyring
	<< " in process " << getpid();
	}
	return true;
	}

	bool evictKey(const std::string& raw_ref) {
	key_serial_t device_keyring;
	if (!e4cryptKeyring(&device_keyring)) return false;
	bool success = true;
	for (char const* const* name_prefix = NAME_PREFIXES; *name_prefix != nullptr; name_prefix++) {
	auto ref = keyname(*name_prefix, raw_ref);
	auto key_serial = keyctl_search(device_keyring, "logon", ref.c_str(), 0);

	// Unlink the key from the keyring. Prefer unlinking to revoking or
	// invalidating, since unlinking is actually no less secure currently, and
	// it avoids bugs in certain kernel versions where the keyring key is
	// referenced from places it shouldn't be.
	if (keyctl_unlink(key_serial, device_keyring) != 0) {
	PLOG(ERROR) << "Failed to unlink key with serial " << key_serial << " ref " << ref;
	success = false;
	} else {
	LOG(DEBUG) << "Unlinked key with serial " << key_serial << " ref " << ref;
	}
	}
	return success;
	}

	bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_authentication,
	const std::string& key_path, const std::string& tmp_path,
	std::string* key_ref) {
	KeyBuffer key;
	if (pathExists(key_path)) {
	LOG(DEBUG) << "Key exists, using: " << key_path;
	if (!retrieveKey(key_path, key_authentication, &key)) return false;
	} else {
	if (!create_if_absent) {
	LOG(ERROR) << "No key found in " << key_path;
	return false;
	}
	LOG(INFO) << "Creating new key in " << key_path;
	if (!randomKey(&key)) return false;
	if (!storeKeyAtomically(key_path, tmp_path, key_authentication, key)) return false;
	}

	if (!installKey(key, key_ref)) {
	LOG(ERROR) << "Failed to install key in " << key_path;
	return false;
	}
	return true;
	}

	bool retrieveKey(bool create_if_absent, const std::string& key_path, const std::string& tmp_path,
	KeyBuffer* key) {
	if (pathExists(key_path)) {
	LOG(DEBUG) << "Key exists, using: " << key_path;
	if (!retrieveKey(key_path, kEmptyAuthentication, key)) return false;
	} else {
	if (!create_if_absent) {
	LOG(ERROR) << "No key found in " << key_path;
	return false;
	}
	LOG(INFO) << "Creating new key in " << key_path;
	if (!randomKey(key)) return false;
	if (!storeKeyAtomically(key_path, tmp_path, kEmptyAuthentication, *key)) return false;
	}
	return true;
	}

	} // namespace vold
	} // namespace android