github: support provider URL (#2490)

internal/httputil/client.go

@@ -80,11 +80,13 @@ func (c *httpClient) Do(req *http.Request) (*http.Response, error) {
 	return c.Client.Do(req)
 }
 
-// defaultClient avoids leaks by setting an upper limit for timeouts.
-var defaultClient = &httpClient{
+// getDefaultClient returns an HTTP client that avoids leaks by setting an upper limit for timeouts.
+func getDefaultClient() *httpClient {
+	return &httpClient{
 		&http.Client{Timeout: 1 * time.Minute},
 		requestid.NewRoundTripper(http.DefaultTransport),
 	}
+}
 
 // Do provides a simple helper interface to make HTTP requests
 func Do(ctx context.Context, method, endpoint, userAgent string, headers map[string]string, params url.Values, response interface{}) error {
@@ -113,7 +115,7 @@ func Do(ctx context.Context, method, endpoint, userAgent string, headers map[str
 		req.Header.Set(k, v)
 	}
 
-	resp, err := defaultClient.Do(req)
+	resp, err := getDefaultClient().Do(req)
 	if err != nil {
 		return err
 	}

internal/httputil/client_test.go

@@ -21,5 +21,5 @@ func TestDefaultClient(t *testing.T) {
 	defer ts.Close()
 	req, _ := http.NewRequest(http.MethodGet, ts.URL, nil)
 	req = req.WithContext(requestid.WithValue(context.Background(), "foo"))
-	_, _ = defaultClient.Do(req)
+	_, _ = getDefaultClient().Do(req)
 }

internal/identity/oauth/github/github.go

@@ -21,6 +21,7 @@ import (
 	"github.com/pomerium/pomerium/internal/identity/oauth"
 	"github.com/pomerium/pomerium/internal/identity/oidc"
 	"github.com/pomerium/pomerium/internal/log"
+	"github.com/pomerium/pomerium/internal/urlutil"
 	"github.com/pomerium/pomerium/internal/version"
 )
 
@@ -51,6 +52,7 @@ type Provider struct {
 	Oauth *oauth2.Config
 
 	userEndpoint  string
+	emailEndpoint string
 }
 
 // New instantiates an OAuth2 provider for Github.
@@ -59,6 +61,16 @@ func New(ctx context.Context, o *oauth.Options) (*Provider, error) {
 	if o.ProviderURL == "" {
 		o.ProviderURL = defaultProviderURL
 	}
+
+	// when the default provider url is used, use the Github API endpoint
+	if o.ProviderURL == defaultProviderURL {
+		p.userEndpoint = urlutil.Join(githubAPIURL, userPath)
+		p.emailEndpoint = urlutil.Join(githubAPIURL, emailPath)
+	} else {
+		p.userEndpoint = urlutil.Join(o.ProviderURL, userPath)
+		p.emailEndpoint = urlutil.Join(o.ProviderURL, emailPath)
+	}
+
 	if len(o.Scopes) == 0 {
 		o.Scopes = defaultScopes
 	}
@@ -68,11 +80,10 @@ func New(ctx context.Context, o *oauth.Options) (*Provider, error) {
 		Scopes:       o.Scopes,
 		RedirectURL:  o.RedirectURL.String(),
 		Endpoint: oauth2.Endpoint{
-			AuthURL:  o.ProviderURL + authURL,
-			TokenURL: o.ProviderURL + tokenURL,
+			AuthURL:  urlutil.Join(o.ProviderURL, authURL),
+			TokenURL: urlutil.Join(o.ProviderURL, tokenURL),
 		},
 	}
-	p.userEndpoint = githubAPIURL + userPath
 	return &p, nil
 }
 
@@ -133,8 +144,7 @@ func (p *Provider) userEmail(ctx context.Context, t *oauth2.Token, v interface{}
 		Visibility string `json:"visibility"`
 	}
 	headers := map[string]string{"Authorization": fmt.Sprintf("token %s", t.AccessToken)}
-	emailURL := githubAPIURL + emailPath
-	err := httputil.Do(ctx, http.MethodGet, emailURL, version.UserAgent(), headers, nil, &response)
+	err := httputil.Do(ctx, http.MethodGet, p.emailEndpoint, version.UserAgent(), headers, nil, &response)
 	if err != nil {
 		return err
 	}

internal/urlutil/url.go

@@ -113,3 +113,21 @@ func GetDomainsForURL(u url.URL) []string {
 func IsTCP(u *url.URL) bool {
 	return u.Scheme == "tcp+http" || u.Scheme == "tcp+https"
 }
+
+// Join joins elements of a URL with '/'.
+func Join(elements ...string) string {
+	var builder strings.Builder
+	appendSlash := false
+	for i, el := range elements {
+		if appendSlash {
+			builder.WriteByte('/')
+		}
+		if i > 0 && strings.HasPrefix(el, "/") {
+			builder.WriteString(el[1:])
+		} else {
+			builder.WriteString(el)
+		}
+		appendSlash = !strings.HasSuffix(el, "/")
+	}
+	return builder.String()
+}

internal/urlutil/url_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
+	"github.com/stretchr/testify/assert"
 )
 
 func Test_StripPort(t *testing.T) {
@@ -158,3 +159,10 @@ func TestGetDomainsForURL(t *testing.T) {
 		})
 	}
 }
+
+func TestJoin(t *testing.T) {
+	assert.Equal(t, "/x/y/z/", Join("/x", "y/z/"))
+	assert.Equal(t, "/x/y/z/", Join("/x/", "y/z/"))
+	assert.Equal(t, "/x/y/z/", Join("/x", "/y/z/"))
+	assert.Equal(t, "/x/y/z/", Join("/x/", "/y/z/"))
+}