Replace hardcoded parameters

common/ecies_crypto.h

@@ -0,0 +1,82 @@
+////////////////////////////////////////////////////////////////////////////////
+// Copyright 2019 Google LLC.
+//
+// This software is licensed under the terms defined in the Widevine Master
+// License Agreement. For a copy of this agreement, please contact
+// widevine-licensing@google.com.
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef COMMON_ECIES_CRYPTO_H_
+#define COMMON_ECIES_CRYPTO_H_
+
+#include <memory>
+#include <string>
+
+#include "common/ec_key.h"
+#include "common/ec_key_source.h"
+
+namespace widevine {
+
+class EciesEncryptor {
+ public:
+  static std::unique_ptr<EciesEncryptor> Create(const std::string& public_key,
+                                                ECKeySource* key_source);
+  virtual ~EciesEncryptor() = default;
+  EciesEncryptor(const EciesEncryptor&) = delete;
+  EciesEncryptor& operator=(const EciesEncryptor&) = delete;
+
+  // Generates an encrypted EC-IES message using the public key, an ephemeral
+  // private key and context. This function uses AES 256 bit encryption with a
+  // master key derived from EC shared key generated from the public key and
+  // ephemeral private key.
+  // |plaintext| is the value to be encrypted.
+  // |context| is used as part of the key derivation.
+  // |ecies_message| is the concatenation of
+  //    1) the ephemeral public key.
+  //    2) the plaintext encrypted with the derived AES key using AES CBC,
+  //       PKCS7 padding and a zerio iv.
+  //    3) The HMAC SHA256 of the cipher text.
+  // Returns false if there is a problem encrypting the content, true otherwise.
+  virtual bool Encrypt(const std::string& plaintext, const std::string& context,
+                       std::string* ecies_message) const;
+
+ protected:
+  // Creates the EciesEncryptor with a given ECKey. This is protected in order
+  // to support mock tests.
+  EciesEncryptor(std::unique_ptr<ECPublicKey> public_key,
+                 ECKeySource* key_source);
+
+ private:
+  std::unique_ptr<ECPublicKey> public_key_;
+  ECKeySource* key_source_;
+};
+
+class EciesDecryptor {
+ public:
+  static std::unique_ptr<EciesDecryptor> Create(
+      const std::string& serialized_private_key);
+
+  virtual ~EciesDecryptor() = default;
+  EciesDecryptor(const EciesDecryptor&) = delete;
+  EciesDecryptor& operator=(const EciesDecryptor&) = delete;
+
+  // Decrypts and verifies an EC-IES message using the private key, the
+  // ephemeral public key embedded in |ecies_message| and the |context|.
+  // This function uses a master AES key to decrypt the content and validate the
+  // signature.  The content is encrypted with AES CBC, PKCS7 padded with a
+  // zero iv.
+  // |plaintext| will be populated iff decryption is successful and the
+  // signature is valid.
+  // Returns false if there is a problem decrypting the content, true otherwise.
+  virtual bool Decrypt(const std::string& ecies_message,
+                       const std::string& context,
+                       std::string* plaintext) const;
+
+ private:
+  explicit EciesDecryptor(std::unique_ptr<ECPrivateKey> private_key);
+  std::unique_ptr<ECPrivateKey> private_key_;
+};
+
+}  // namespace widevine
+
+#endif  // COMMON_ECIES_CRYPTO_H_