class JSON::JWE

def decrypt!(private_key_or_secret, algorithms = nil, encryption_methods = nil)
  raise UnexpectedAlgorithm.new('Unexpected alg header') unless algorithms.blank? || Array(algorithms).include?(alg)
  raise UnexpectedAlgorithm.new('Unexpected enc header') unless encryption_methods.blank? || Array(encryption_methods).include?(enc)
  self.private_key_or_secret = with_jwk_support private_key_or_secret
  self.content_encryption_key = decrypt_content_encryption_key
  self.mac_key, self.encryption_key = derive_encryption_and_mac_keys
  verify_cbc_authentication_tag! if cbc?
  cipher.decrypt
  cipher.key = encryption_key
  cipher.iv = iv # NOTE: 'iv' has to be set after 'key' for GCM
  if gcm?
    # https://github.com/ruby/openssl/issues/63
    raise DecryptionFailed.new('Invalid authentication tag') if authentication_tag.length < 16
    cipher.auth_tag = authentication_tag
    cipher.auth_data = auth_data
  end
  begin
    self.plain_text = cipher.update(cipher_text) + cipher.final
  rescue OpenSSL::OpenSSLError
    # Ensure that the same error is raised for invalid PKCS7 padding
    # as for invalid signatures. This prevents padding-oracle attacks.
    raise DecryptionFailed
  end
  self
end