class Aws::S3::Encryption::DecryptHandler

def v2_envelope(envelope)
  unless POSSIBLE_ENCRYPTION_FORMATS.include? envelope['x-amz-cek-alg']
    alg = envelope['x-amz-cek-alg'].inspect
    msg = "unsupported content encrypting key (cek) format: #{alg}"
    raise Errors::DecryptionError, msg
  end
  unless POSSIBLE_WRAPPING_FORMATS.include? envelope['x-amz-wrap-alg']
    alg = envelope['x-amz-wrap-alg'].inspect
    msg = "unsupported key wrapping algorithm: #{alg}"
    raise Errors::DecryptionError, msg
  end
  unless (missing_keys = V2_ENVELOPE_KEYS - envelope.keys).empty?
    msg = "incomplete v2 encryption envelope:\n"
    msg += "  missing: #{missing_keys.join(',')}\n"
    raise Errors::DecryptionError, msg
  end
  envelope
end