112 lines
3.6 KiB
C++
112 lines
3.6 KiB
C++
/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef KEYSTORE_BLOB_H_
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#define KEYSTORE_BLOB_H_
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#include <stdint.h>
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#include <openssl/aes.h>
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#include <openssl/md5.h>
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#include <keystore/keystore.h>
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#define VALUE_SIZE 32768
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/* Here is the file format. There are two parts in blob.value, the secret and
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* the description. The secret is stored in ciphertext, and its original size
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* can be found in blob.length. The description is stored after the secret in
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* plaintext, and its size is specified in blob.info. The total size of the two
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* parts must be no more than VALUE_SIZE bytes. The first field is the version,
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* the second is the blob's type, and the third byte is flags. Fields other
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* than blob.info, blob.length, and blob.value are modified by encryptBlob()
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* and decryptBlob(). Thus they should not be accessed from outside. */
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/* ** Note to future implementors of encryption: **
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* Currently this is the construction:
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* metadata || Enc(MD5(data) || data)
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*
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* This should be the construction used for encrypting if re-implementing:
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*
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* Derive independent keys for encryption and MAC:
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* Kenc = AES_encrypt(masterKey, "Encrypt")
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* Kmac = AES_encrypt(masterKey, "MAC")
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*
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* Store this:
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* metadata || AES_CTR_encrypt(Kenc, rand_IV, data) ||
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* HMAC(Kmac, metadata || Enc(data))
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*/
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struct __attribute__((packed)) blob {
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uint8_t version;
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uint8_t type;
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uint8_t flags;
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uint8_t info;
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uint8_t vector[AES_BLOCK_SIZE];
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uint8_t encrypted[0]; // Marks offset to encrypted data.
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uint8_t digest[MD5_DIGEST_LENGTH];
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uint8_t digested[0]; // Marks offset to digested data.
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int32_t length; // in network byte order when encrypted
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uint8_t value[VALUE_SIZE + AES_BLOCK_SIZE];
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};
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static const uint8_t CURRENT_BLOB_VERSION = 2;
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typedef enum {
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TYPE_ANY = 0, // meta type that matches anything
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TYPE_GENERIC = 1,
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TYPE_MASTER_KEY = 2,
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TYPE_KEY_PAIR = 3,
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TYPE_KEYMASTER_10 = 4,
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TYPE_KEY_CHARACTERISTICS = 5,
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} BlobType;
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class Entropy;
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class Blob {
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public:
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Blob(const uint8_t* value, size_t valueLength, const uint8_t* info, uint8_t infoLength,
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BlobType type);
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Blob(blob b);
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Blob();
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const uint8_t* getValue() const { return mBlob.value; }
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int32_t getLength() const { return mBlob.length; }
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const uint8_t* getInfo() const { return mBlob.value + mBlob.length; }
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uint8_t getInfoLength() const { return mBlob.info; }
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uint8_t getVersion() const { return mBlob.version; }
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bool isEncrypted() const;
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void setEncrypted(bool encrypted);
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bool isFallback() const { return mBlob.flags & KEYSTORE_FLAG_FALLBACK; }
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void setFallback(bool fallback);
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void setVersion(uint8_t version) { mBlob.version = version; }
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BlobType getType() const { return BlobType(mBlob.type); }
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void setType(BlobType type) { mBlob.type = uint8_t(type); }
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ResponseCode writeBlob(const char* filename, AES_KEY* aes_key, State state, Entropy* entropy);
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ResponseCode readBlob(const char* filename, AES_KEY* aes_key, State state);
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private:
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struct blob mBlob;
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};
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#endif // KEYSTORE_BLOB_H_
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