class Aws::Plugins::SignatureV4

def apply_signature(options = {})
  context = apply_authtype(options[:context])
  signer = options[:signer] || context.config.sigv4_signer
  req = context.http_request
  # in case this request is being re-signed
  req.headers.delete('Authorization')
  req.headers.delete('X-Amz-Security-Token')
  req.headers.delete('X-Amz-Date')
  # compute the signature
  begin
    signature = signer.sign_request(
      http_method: req.http_method,
      url: req.endpoint,
      headers: req.headers,
      body: req.body
    )
  rescue Aws::Sigv4::Errors::MissingCredentialsError
    raise Aws::Errors::MissingCredentialsError
  end
  # apply signature headers
  req.headers.update(signature.headers)
  # add request metadata with signature components for debugging
  context[:canonical_request] = signature.canonical_request
  context[:string_to_sign] = signature.string_to_sign
end