src/server/auth/server/saml.go
func fetchRawIDPMetadata(name string, mdURL *url.URL) ([]byte, error) {
	c := http.DefaultClient
	req, err := http.NewRequest("GET", mdURL.String(), nil)
	if err != nil {
		return nil, fmt.Errorf("could not retrieve IdP metadata for %q: %v", name, err)
	}
	req.Header.Set("User-Agent", "Golang; github.com/pachyderm/pachdyerm")

	var rawMetadata []byte
	b := backoff.NewInfiniteBackOff()
	b.MaxElapsedTime = 30 * time.Second
	b.MaxInterval = 2 * time.Second
	if err := backoff.RetryNotify(func() error {
		resp, err := c.Do(req)
		if err != nil {
			return err
		}

		if resp.StatusCode != http.StatusOK {
			return fmt.Errorf("%d %s", resp.StatusCode, resp.Status)
		}
		rawMetadata, err = ioutil.ReadAll(resp.Body)
		resp.Body.Close()
		if err != nil {
			return fmt.Errorf("could not read IdP metadata response body: %v", err)
		}
		if len(rawMetadata) == 0 {
			return fmt.Errorf("empty metadata from IdP")
		}
		return nil
	}, b, func(err error, d time.Duration) error {
		logrus.Printf("error retrieving IdP metadata: %v; retrying in %v", err, d)
		return nil
	}); err != nil {
		return nil, err
	}

	// Successfully retrieved metadata
	return rawMetadata, nil
}
func fetchRawIDPMetadata(name string, mdURL *url.URL) ([]byte, error) {
	c := http.DefaultClient
	req, err := http.NewRequest("GET", mdURL.String(), nil)
	if err != nil {
		return nil, fmt.Errorf("could not retrieve IdP metadata for %q: %v", name, err)
	}
	req.Header.Set("User-Agent", "Golang; github.com/pachyderm/pachdyerm")

	var rawMetadata []byte
	b := backoff.NewInfiniteBackOff()
	b.MaxElapsedTime = 30 * time.Second
	b.MaxInterval = 2 * time.Second
	if err := backoff.RetryNotify(func() error {
		resp, err := c.Do(req)
		if err != nil {
			return err
		}

		if resp.StatusCode != http.StatusOK {
			return fmt.Errorf("%d %s", resp.StatusCode, resp.Status)
		}
		rawMetadata, err = ioutil.ReadAll(resp.Body)
		resp.Body.Close()
		if err != nil {
			return fmt.Errorf("could not read IdP metadata response body: %v", err)
		}
		if len(rawMetadata) == 0 {
			return fmt.Errorf("empty metadata from IdP")
		}
		return nil
	}, b, func(err error, d time.Duration) error {
		logrus.Printf("error retrieving IdP metadata: %v; retrying in %v", err, d)
		return nil
	}); err != nil {
		return nil, err
	}

	// Successfully retrieved metadata
	return rawMetadata, nil
}
// fetchRawIDPMetadata is a helper of validateConfig, below. It takes the URL
// of a SAML IdP's Metadata service, queries it, parses the result, and returns
// it as a struct the crewjam/saml library can use.
// This code is heavily based on the crewjam/saml/samlsp.Middleware constructor