signers.py 文件源码

def _choose_signer(self, operation_name, signing_type):
        """
        Allow setting the signature version via the choose-signer event.
        A value of `botocore.UNSIGNED` means no signing will be performed.

        :param operation_name: The operation to sign.
        :param signing_type: The type of signing that the signer is to be used
            for.
        :return: The signature version to sign with.
        """
        signing_type_suffix_map = {
            'presign-post': '-presign-post',
            'presign-url': '-query'
        }
        suffix = signing_type_suffix_map.get(signing_type, '')

        signature_version = self._signature_version
        if signature_version is not botocore.UNSIGNED and not \
                signature_version.endswith(suffix):
            signature_version += suffix

        handler, response = self._event_emitter.emit_until_response(
            'choose-signer.{0}.{1}'.format(self._service_name, operation_name),
            signing_name=self._signing_name, region_name=self._region_name,
            signature_version=signature_version)

        if response is not None:
            signature_version = response
            # The suffix needs to be checked again in case we get an improper
            # signature version from choose-signer.
            if signature_version is not botocore.UNSIGNED and not \
                    signature_version.endswith(suffix):
                signature_version += suffix

        return signature_version