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/*
* Copyright (C) 2015 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.
*/
#ifndef KEYSTORE_BLOB_H_
#define KEYSTORE_BLOB_H_
#include <stdint.h>
#include <openssl/aes.h>
#include <openssl/md5.h>
#include <keystore/keystore.h>
#define VALUE_SIZE 32768
/* Here is the file format. There are two parts in blob.value, the secret and
* the description. The secret is stored in ciphertext, and its original size
* can be found in blob.length. The description is stored after the secret in
* plaintext, and its size is specified in blob.info. The total size of the two
* parts must be no more than VALUE_SIZE bytes. The first field is the version,
* the second is the blob's type, and the third byte is flags. Fields other
* than blob.info, blob.length, and blob.value are modified by encryptBlob()
* and decryptBlob(). Thus they should not be accessed from outside. */
/* ** Note to future implementors of encryption: **
* Currently this is the construction:
* metadata || Enc(MD5(data) || data)
*
* This should be the construction used for encrypting if re-implementing:
*
* Derive independent keys for encryption and MAC:
* Kenc = AES_encrypt(masterKey, "Encrypt")
* Kmac = AES_encrypt(masterKey, "MAC")
*
* Store this:
* metadata || AES_CTR_encrypt(Kenc, rand_IV, data) ||
* HMAC(Kmac, metadata || Enc(data))
*/
struct __attribute__((packed)) blob {
uint8_t version;
uint8_t type;
uint8_t flags;
uint8_t info;
uint8_t vector[AES_BLOCK_SIZE];
uint8_t encrypted[0]; // Marks offset to encrypted data.
uint8_t digest[MD5_DIGEST_LENGTH];
uint8_t digested[0]; // Marks offset to digested data.
int32_t length; // in network byte order when encrypted
uint8_t value[VALUE_SIZE + AES_BLOCK_SIZE];
};
static const uint8_t CURRENT_BLOB_VERSION = 2;
typedef enum {
TYPE_ANY = 0, // meta type that matches anything
TYPE_GENERIC = 1,
TYPE_MASTER_KEY = 2,
TYPE_KEY_PAIR = 3,
TYPE_KEYMASTER_10 = 4,
} BlobType;
class Entropy;
class Blob {
public:
Blob(const uint8_t* value, size_t valueLength, const uint8_t* info, uint8_t infoLength,
BlobType type);
Blob(blob b);
Blob();
const uint8_t* getValue() const { return mBlob.value; }
int32_t getLength() const { return mBlob.length; }
const uint8_t* getInfo() const { return mBlob.value + mBlob.length; }
uint8_t getInfoLength() const { return mBlob.info; }
uint8_t getVersion() const { return mBlob.version; }
bool isEncrypted() const;
void setEncrypted(bool encrypted);
bool isFallback() const { return mBlob.flags & KEYSTORE_FLAG_FALLBACK; }
void setFallback(bool fallback);
void setVersion(uint8_t version) { mBlob.version = version; }
BlobType getType() const { return BlobType(mBlob.type); }
void setType(BlobType type) { mBlob.type = uint8_t(type); }
ResponseCode writeBlob(const char* filename, AES_KEY* aes_key, State state, Entropy* entropy);
ResponseCode readBlob(const char* filename, AES_KEY* aes_key, State state);
private:
struct blob mBlob;
};
#endif // KEYSTORE_BLOB_H_
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