Support empty OAuth2 inline secrets (#547)

Signed-off-by: Daniel Hrabovcak <thespiritxiii@gmail.com>

config/generate.go

@@ -71,7 +71,6 @@ func SerialNumber() *big.Int {
 	serialNumber.Add(&serial, big.NewInt(1))
 
 	return &serial
-
 }
 
 func GenerateCertificateAuthority(commonName string, parentCert *x509.Certificate, parentKey *rsa.PrivateKey) (*x509.Certificate, *rsa.PrivateKey, error) {
@@ -170,7 +169,7 @@ func writeCertificateAndKey(path string, cert *x509.Certificate, key *rsa.Privat
 		return err
 	}
 
-	if err := os.WriteFile(fmt.Sprintf("%s.crt", path), b.Bytes(), 0644); err != nil {
+	if err := os.WriteFile(fmt.Sprintf("%s.crt", path), b.Bytes(), 0o644); err != nil {
 		return err
 	}
 
@@ -179,7 +178,7 @@ func writeCertificateAndKey(path string, cert *x509.Certificate, key *rsa.Privat
 		return err
 	}
 
-	if err := os.WriteFile(fmt.Sprintf("%s.key", path), b.Bytes(), 0644); err != nil {
+	if err := os.WriteFile(fmt.Sprintf("%s.key", path), b.Bytes(), 0o644); err != nil {
 		return err
 	}
 
@@ -239,7 +238,7 @@ func main() {
 		log.Fatal(err)
 	}
 
-	if err := os.WriteFile("testdata/tls-ca-chain.pem", b.Bytes(), 0644); err != nil {
+	if err := os.WriteFile("testdata/tls-ca-chain.pem", b.Bytes(), 0o644); err != nil {
 		log.Fatal(err)
 	}
 }

config/http_config.go

@@ -378,9 +378,6 @@ func (c *HTTPClientConfig) Validate() error {
 		if len(c.OAuth2.ClientID) == 0 {
 			return fmt.Errorf("oauth2 client_id must be configured")
 		}
-		if len(c.OAuth2.ClientSecret) == 0 && len(c.OAuth2.ClientSecretFile) == 0 {
-			return fmt.Errorf("either oauth2 client_secret or client_secret_file must be configured")
-		}
 		if len(c.OAuth2.TokenURL) == 0 {
 			return fmt.Errorf("oauth2 token_url must be configured")
 		}
@@ -729,13 +726,12 @@ func (rt *oauth2RoundTripper) RoundTrip(req *http.Request) (*http.Response, erro
 		rt.mtx.RLock()
 		changed = secret != rt.secret
 		rt.mtx.RUnlock()
+	} else {
+		// Either an inline secret or nothing (use an empty string) was provided.
+		secret = string(rt.config.ClientSecret)
 	}
 
 	if changed || rt.rt == nil {
-		if rt.config.ClientSecret != "" {
-			secret = string(rt.config.ClientSecret)
-		}
-
 		config := &clientcredentials.Config{
 			ClientID:       rt.config.ClientID,
 			ClientSecret:   secret,

config/http_config_test.go

@@ -115,10 +115,6 @@ var invalidHTTPClientConfigs = []struct {
 		httpClientConfigFile: "testdata/http.conf.oauth2-no-client-id.bad.yaml",
 		errMsg:               "oauth2 client_id must be configured",
 	},
-	{
-		httpClientConfigFile: "testdata/http.conf.oauth2-no-client-secret.bad.yaml",
-		errMsg:               "either oauth2 client_secret or client_secret_file must be configured",
-	},
 	{
 		httpClientConfigFile: "testdata/http.conf.oauth2-no-token-url.bad.yaml",
 		errMsg:               "oauth2 token_url must be configured",
@@ -423,6 +419,46 @@ func TestNewClientFromConfig(t *testing.T) {
 				}
 			},
 		},
+		{
+			clientConfig: HTTPClientConfig{
+				OAuth2: &OAuth2{
+					ClientID: "ExpectedUsername",
+					TLSConfig: TLSConfig{
+						CAFile:             TLSCAChainPath,
+						CertFile:           ClientCertificatePath,
+						KeyFile:            ClientKeyNoPassPath,
+						ServerName:         "",
+						InsecureSkipVerify: false,
+					},
+				},
+				TLSConfig: TLSConfig{
+					CAFile:             TLSCAChainPath,
+					CertFile:           ClientCertificatePath,
+					KeyFile:            ClientKeyNoPassPath,
+					ServerName:         "",
+					InsecureSkipVerify: false,
+				},
+			},
+			handler: func(w http.ResponseWriter, r *http.Request) {
+				switch r.URL.Path {
+				case "/token":
+					res, _ := json.Marshal(oauth2TestServerResponse{
+						AccessToken: ExpectedAccessToken,
+						TokenType:   "Bearer",
+					})
+					w.Header().Add("Content-Type", "application/json")
+					_, _ = w.Write(res)
+
+				default:
+					authorization := r.Header.Get("Authorization")
+					if authorization != "Bearer "+ExpectedAccessToken {
+						fmt.Fprintf(w, "Expected Authorization header %q, got %q", "Bearer "+ExpectedAccessToken, authorization)
+					} else {
+						fmt.Fprint(w, ExpectedMessage)
+					}
+				}
+			},
+		},
 		{
 			clientConfig: HTTPClientConfig{
 				OAuth2: &OAuth2{
@@ -1448,38 +1484,81 @@ type oauth2TestServerResponse struct {
 	TokenType   string `json:"token_type"`
 }
 
-func TestOAuth2(t *testing.T) {
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+type testOAuthServer struct {
+	tokenTS *httptest.Server
+	ts      *httptest.Server
+}
+
+// newTestOAuthServer returns a new test server with the expected base64 encoded client ID and secret.
+func newTestOAuthServer(t testing.TB, expectedAuth *string) testOAuthServer {
+	var previousAuth string
+	tokenTS := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		auth := r.Header.Get("Authorization")
+		if auth != *expectedAuth {
+			t.Fatalf("bad auth, expected %s, got %s", *expectedAuth, auth)
+		}
+		if auth == previousAuth {
+			t.Fatal("token endpoint called twice")
+		}
+		previousAuth = auth
 		res, _ := json.Marshal(oauth2TestServerResponse{
 			AccessToken: "12345",
 			TokenType:   "Bearer",
 		})
 		w.Header().Add("Content-Type", "application/json")
 		_, _ = w.Write(res)
 	}))
-	defer ts.Close()
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		auth := r.Header.Get("Authorization")
+		if auth != "Bearer 12345" {
+			t.Fatalf("bad auth, expected %s, got %s", "Bearer 12345", auth)
+		}
+		fmt.Fprintln(w, "Hello, client")
+	}))
+	return testOAuthServer{
+		tokenTS: tokenTS,
+		ts:      ts,
+	}
+}
+
+func (s *testOAuthServer) url() string {
+	return s.ts.URL
+}
+
+func (s *testOAuthServer) tokenURL() string {
+	return s.tokenTS.URL
+}
+
+func (s *testOAuthServer) close() {
+	s.tokenTS.Close()
+	s.ts.Close()
+}
+
+func TestOAuth2(t *testing.T) {
+	var expectedAuth string
+	ts := newTestOAuthServer(t, &expectedAuth)
+	defer ts.close()
 
 	yamlConfig := fmt.Sprintf(`
 client_id: 1
 client_secret: 2
 scopes:
  - A
  - B
-token_url: %s/token
+token_url: %s
 endpoint_params:
  hi: hello
-`, ts.URL)
+`, ts.tokenURL())
 	expectedConfig := OAuth2{
 		ClientID:       "1",
 		ClientSecret:   "2",
 		Scopes:         []string{"A", "B"},
 		EndpointParams: map[string]string{"hi": "hello"},
-		TokenURL:       fmt.Sprintf("%s/token", ts.URL),
+		TokenURL:       ts.tokenURL(),
 	}
 
 	var unmarshalledConfig OAuth2
-	err := yaml.Unmarshal([]byte(yamlConfig), &unmarshalledConfig)
-	if err != nil {
+	if err := yaml.Unmarshal([]byte(yamlConfig), &unmarshalledConfig); err != nil {
 		t.Fatalf("Expected no error unmarshalling yaml, got %v", err)
 	}
 	if !reflect.DeepEqual(unmarshalledConfig, expectedConfig) {
@@ -1491,9 +1570,59 @@ endpoint_params:
 	client := http.Client{
 		Transport: rt,
 	}
-	resp, _ := client.Get(ts.URL)
+
+	// Default secret.
+	expectedAuth = "Basic MToy"
+	resp, err := client.Get(ts.url())
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	authorization := resp.Request.Header.Get("Authorization")
+	if authorization != "Bearer 12345" {
+		t.Fatalf("Expected authorization header to be 'Bearer', got '%s'", authorization)
+	}
+
+	// Making a second request with the same secret should not re-call the token API.
+	_, err = client.Get(ts.url())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Empty secret.
+	expectedAuth = "Basic MTo="
+	expectedConfig.ClientSecret = ""
+	resp, err = client.Get(ts.url())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	authorization = resp.Request.Header.Get("Authorization")
+	if authorization != "Bearer 12345" {
+		t.Fatalf("Expected authorization header to be 'Bearer 12345', got '%s'", authorization)
+	}
+
+	// Making a second request with the same secret should not re-call the token API.
+	resp, err = client.Get(ts.url())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Update secret.
+	expectedAuth = "Basic MToxMjM0NTY3"
+	expectedConfig.ClientSecret = "1234567"
+	_, err = client.Get(ts.url())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Making a second request with the same secret should not re-call the token API.
+	_, err = client.Get(ts.url())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	authorization = resp.Request.Header.Get("Authorization")
 	if authorization != "Bearer 12345" {
 		t.Fatalf("Expected authorization header to be 'Bearer 12345', got '%s'", authorization)
 	}
@@ -1543,33 +1672,9 @@ func TestOAuth2UserAgent(t *testing.T) {
 }
 
 func TestOAuth2WithFile(t *testing.T) {
-	var expectedAuth *string
-	var previousAuth string
-	tokenTS := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		auth := r.Header.Get("Authorization")
-		if auth != *expectedAuth {
-			t.Fatalf("bad auth, expected %s, got %s", *expectedAuth, auth)
-		}
-		if auth == previousAuth {
-			t.Fatal("token endpoint called twice")
-		}
-		previousAuth = auth
-		res, _ := json.Marshal(oauth2TestServerResponse{
-			AccessToken: "12345",
-			TokenType:   "Bearer",
-		})
-		w.Header().Add("Content-Type", "application/json")
-		_, _ = w.Write(res)
-	}))
-	defer tokenTS.Close()
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		auth := r.Header.Get("Authorization")
-		if auth != "Bearer 12345" {
-			t.Fatalf("bad auth, expected %s, got %s", "Bearer 12345", auth)
-		}
-		fmt.Fprintln(w, "Hello, client")
-	}))
-	defer ts.Close()
+	var expectedAuth string
+	ts := newTestOAuthServer(t, &expectedAuth)
+	defer ts.close()
 
 	secretFile, err := os.CreateTemp("", "oauth2_secret")
 	if err != nil {
@@ -1586,13 +1691,13 @@ scopes:
 token_url: %s
 endpoint_params:
  hi: hello
-`, secretFile.Name(), tokenTS.URL)
+`, secretFile.Name(), ts.tokenURL())
 	expectedConfig := OAuth2{
 		ClientID:         "1",
 		ClientSecretFile: secretFile.Name(),
 		Scopes:           []string{"A", "B"},
 		EndpointParams:   map[string]string{"hi": "hello"},
-		TokenURL:         tokenTS.URL,
+		TokenURL:         ts.tokenURL(),
 	}
 
 	var unmarshalledConfig OAuth2
@@ -1610,40 +1715,57 @@ endpoint_params:
 		Transport: rt,
 	}
 
-	tk := "Basic MToxMjM0NTY="
-	expectedAuth = &tk
+	// Empty secret file.
+	expectedAuth = "Basic MTo="
+	resp, err := client.Get(ts.url())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	authorization := resp.Request.Header.Get("Authorization")
+	if authorization != "Bearer 12345" {
+		t.Fatalf("Expected authorization header to be 'Bearer', got '%s'", authorization)
+	}
+
+	// Making a second request with the same file content should not re-call the token API.
+	_, err = client.Get(ts.url())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// File populated.
+	expectedAuth = "Basic MToxMjM0NTY="
 	if _, err := secretFile.Write([]byte("123456")); err != nil {
 		t.Fatal(err)
 	}
-	resp, err := client.Get(ts.URL)
+	resp, err = client.Get(ts.url())
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	authorization := resp.Request.Header.Get("Authorization")
+	authorization = resp.Request.Header.Get("Authorization")
 	if authorization != "Bearer 12345" {
 		t.Fatalf("Expected authorization header to be 'Bearer 12345', got '%s'", authorization)
 	}
 
 	// Making a second request with the same file content should not re-call the token API.
-	resp, err = client.Get(ts.URL)
+	resp, err = client.Get(ts.url())
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	tk = "Basic MToxMjM0NTY3"
-	expectedAuth = &tk
+	// Update file.
+	expectedAuth = "Basic MToxMjM0NTY3"
 	if _, err := secretFile.Write([]byte("7")); err != nil {
 		t.Fatal(err)
 	}
-
-	_, err = client.Get(ts.URL)
+	_, err = client.Get(ts.url())
 	if err != nil {
 		t.Fatal(err)
 	}
 
 	// Making a second request with the same file content should not re-call the token API.
-	_, err = client.Get(ts.URL)
+	_, err = client.Get(ts.url())
 	if err != nil {
 		t.Fatal(err)
 	}