public function get_oauth_parameters() {
		$params = array_merge( $_GET, $_POST ); // WPCS: CSRF ok.
		$params = wp_unslash( $params );
		$header = $this->get_authorization_header();

		if ( ! empty( $header ) ) {
			// Trim leading spaces.
			$header        = trim( $header );
			$header_params = $this->parse_header( $header );

			if ( ! empty( $header_params ) ) {
				$params = array_merge( $params, $header_params );
			}
		}

		$param_names = array(
			'oauth_consumer_key',
			'oauth_timestamp',
			'oauth_nonce',
			'oauth_signature',
			'oauth_signature_method',
		);

		$errors   = array();
		$have_one = false;

		// Check for required OAuth parameters.
		foreach ( $param_names as $param_name ) {
			if ( empty( $params[ $param_name ] ) ) {
				$errors[] = $param_name;
			} else {
				$have_one = true;
			}
		}

		// All keys are missing, so we're probably not even trying to use OAuth.
		if ( ! $have_one ) {
			return array();
		}

		// If we have at least one supplied piece of data, and we have an error,
		// then it's a failed authentication.
		if ( ! empty( $errors ) ) {
			$message = sprintf(
				/* translators: %s: amount of errors */
				_n( 'Missing OAuth parameter %s', 'Missing OAuth parameters %s', count( $errors ), 'woocommerce' ),
				implode( ', ', $errors )
			);

			$this->set_error( new WP_Error( 'woocommerce_rest_authentication_missing_parameter', $message, array( 'status' => 401 ) ) );

			return array();
		}

		return $params;
	}