Add proxy_url support for oauth2

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

config/http_config.go

@@ -161,6 +161,8 @@ type OAuth2 struct {
 	TokenURL         string            `yaml:"token_url" json:"token_url"`
 	EndpointParams   map[string]string `yaml:"endpoint_params,omitempty" json:"endpoint_params,omitempty"`
 
+	// HTTP proxy server to use to connect to the targets.
+	ProxyURL URL `yaml:"proxy_url,omitempty" json:"proxy_url,omitempty"`
 	// TLSConfig is used to connect to the token URL.
 	TLSConfig TLSConfig `yaml:"tls_config,omitempty"`
 }
@@ -606,10 +608,16 @@ func (rt *oauth2RoundTripper) RoundTrip(req *http.Request) (*http.Response, erro
 
 		var t http.RoundTripper
 		if len(rt.config.TLSConfig.CAFile) == 0 {
-			t = &http.Transport{TLSClientConfig: tlsConfig}
+			t = &http.Transport{
+				TLSClientConfig: tlsConfig,
+				Proxy:           http.ProxyURL(rt.config.ProxyURL.URL),
+			}
 		} else {
 			t, err = NewTLSRoundTripper(tlsConfig, rt.config.TLSConfig.CAFile, func(tls *tls.Config) (http.RoundTripper, error) {
-				return &http.Transport{TLSClientConfig: tls}, nil
+				return &http.Transport{
+					TLSClientConfig: tls,
+					Proxy:           http.ProxyURL(rt.config.ProxyURL.URL),
+				}, nil
 			})
 			if err != nil {
 				return nil, err

config/http_config_test.go

@@ -1482,3 +1482,10 @@ func TestMarshalURLWithSecret(t *testing.T) {
 		t.Fatalf("URL not properly marshaled in YAML, got '%s'", string(b))
 	}
 }
+
+func TestOAuth2Proxy(t *testing.T) {
+	_, _, err := LoadHTTPConfigFile("testdata/http.conf.oauth2-proxy.good.yml")
+	if err != nil {
+		t.Errorf("Error loading OAuth2 client config: %v", err)
+	}
+}

config/testdata/http.conf.oauth2-proxy.good.yml

@@ -0,0 +1,5 @@
+oauth2:
+  client_id: "myclient"
+  client_secret: "mysecret"
+  token_url: "http://auth"
+  proxy_url: "http://foo"