Adding support for file based configuration of basic auth username in http client config

config/http_config.go

@@ -129,6 +129,7 @@ func (tv *TLSVersion) String() string {
 // BasicAuth contains basic HTTP authentication credentials.
 type BasicAuth struct {
 	Username     string `yaml:"username" json:"username"`
+	UsernameFile string `yaml:"username_file,omitempty" json:"username_file,omitempty"`
 	Password     Secret `yaml:"password,omitempty" json:"password,omitempty"`
 	PasswordFile string `yaml:"password_file,omitempty" json:"password_file,omitempty"`
 }
@@ -139,6 +140,7 @@ func (a *BasicAuth) SetDirectory(dir string) {
 		return
 	}
 	a.PasswordFile = JoinDir(dir, a.PasswordFile)
+	a.UsernameFile = JoinDir(dir, a.UsernameFile)
 }
 
 // Authorization contains HTTP authorization credentials.
@@ -334,6 +336,9 @@ func (c *HTTPClientConfig) Validate() error {
 	if (c.BasicAuth != nil || c.OAuth2 != nil) && (len(c.BearerToken) > 0 || len(c.BearerTokenFile) > 0) {
 		return fmt.Errorf("at most one of basic_auth, oauth2, bearer_token & bearer_token_file must be configured")
 	}
+	if c.BasicAuth != nil && (string(c.BasicAuth.Username) != "" && c.BasicAuth.UsernameFile != "") {
+		return fmt.Errorf("at most one of basic_auth username & username_file must be configured")
+	}
 	if c.BasicAuth != nil && (string(c.BasicAuth.Password) != "" && c.BasicAuth.PasswordFile != "") {
 		return fmt.Errorf("at most one of basic_auth password & password_file must be configured")
 	}
@@ -555,7 +560,7 @@ func NewRoundTripperFromConfig(cfg HTTPClientConfig, name string, optFuncs ...HT
 		}
 
 		if cfg.BasicAuth != nil {
-			rt = NewBasicAuthRoundTripper(cfg.BasicAuth.Username, cfg.BasicAuth.Password, cfg.BasicAuth.PasswordFile, rt)
+			rt = NewBasicAuthRoundTripper(cfg.BasicAuth.Username, cfg.BasicAuth.Password, cfg.BasicAuth.PasswordFile, cfg.BasicAuth.UsernameFile, rt)
 		}
 
 		if cfg.OAuth2 != nil {
@@ -646,32 +651,52 @@ type basicAuthRoundTripper struct {
 	username     string
 	password     Secret
 	passwordFile string
+	usernameFile string
 	rt           http.RoundTripper
 }
 
 // NewBasicAuthRoundTripper will apply a BASIC auth authorization header to a request unless it has
 // already been set.
-func NewBasicAuthRoundTripper(username string, password Secret, passwordFile string, rt http.RoundTripper) http.RoundTripper {
-	return &basicAuthRoundTripper{username, password, passwordFile, rt}
+func NewBasicAuthRoundTripper(username string, password Secret, passwordFile string, usernameFile string, rt http.RoundTripper) http.RoundTripper {
+	return &basicAuthRoundTripper{username, password, passwordFile, usernameFile, rt}
 }
 
 func (rt *basicAuthRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
 	if len(req.Header.Get("Authorization")) != 0 {
 		return rt.rt.RoundTrip(req)
 	}
+	username, err := getBasicAuthUsername(*rt)
+	if err != nil {
+		return nil, err
+	}
+	password, err := getBasicAuthPassword(*rt)
+	if err != nil {
+		return nil, err
+	}
 	req = cloneRequest(req)
+	req.SetBasicAuth(username, password)
+	return rt.rt.RoundTrip(req)
+}
+func getBasicAuthUsername(rt basicAuthRoundTripper) (string, error) {
+	if rt.usernameFile != "" {
+		usernameBytes, err := os.ReadFile(rt.usernameFile)
+		if err != nil {
+			return "", fmt.Errorf("unable to read basic auth password file %s: %s", rt.usernameFile, err)
+		}
+		return strings.TrimSpace(string(usernameBytes)), nil
+	}
+	return rt.username, nil
+}
+func getBasicAuthPassword(rt basicAuthRoundTripper) (string, error) {
 	if rt.passwordFile != "" {
-		bs, err := os.ReadFile(rt.passwordFile)
+		passwordBytes, err := os.ReadFile(rt.passwordFile)
 		if err != nil {
-			return nil, fmt.Errorf("unable to read basic auth password file %s: %s", rt.passwordFile, err)
+			return "", fmt.Errorf("unable to read basic auth password file %s: %s", rt.passwordFile, err)
 		}
-		req.SetBasicAuth(rt.username, strings.TrimSpace(string(bs)))
-	} else {
-		req.SetBasicAuth(rt.username, strings.TrimSpace(string(rt.password)))
+		return strings.TrimSpace(string(passwordBytes)), nil
 	}
-	return rt.rt.RoundTrip(req)
+	return string(rt.password), nil
 }
-
 func (rt *basicAuthRoundTripper) CloseIdleConnections() {
 	if ci, ok := rt.rt.(closeIdler); ok {
 		ci.CloseIdleConnections()

config/http_config_test.go

@@ -83,6 +83,10 @@ var invalidHTTPClientConfigs = []struct {
 		httpClientConfigFile: "testdata/http.conf.basic-auth.too-much.bad.yaml",
 		errMsg:               "at most one of basic_auth password & password_file must be configured",
 	},
+	{
+		httpClientConfigFile: "testdata/http.conf.basic-auth.bad-username.yaml",
+		errMsg:               "at most one of basic_auth username & username_file must be configured",
+	},
 	{
 		httpClientConfigFile: "testdata/http.conf.mix-bearer-and-creds.bad.yaml",
 		errMsg:               "authorization is not compatible with bearer_token & bearer_token_file",
@@ -896,6 +900,32 @@ func TestBasicAuthPasswordFile(t *testing.T) {
 	}
 }
 
+func TestBasicUsernameFile(t *testing.T) {
+	cfg, _, err := LoadHTTPConfigFile("testdata/http.conf.basic-auth.username-file.good.yaml")
+	if err != nil {
+		t.Fatalf("Error loading HTTP client config: %v", err)
+	}
+	client, err := NewClientFromConfig(*cfg, "test")
+	if err != nil {
+		t.Fatalf("Error creating HTTP Client: %v", err)
+	}
+
+	rt, ok := client.Transport.(*basicAuthRoundTripper)
+	if !ok {
+		t.Fatalf("Error casting to basic auth transport, %v", client.Transport)
+	}
+
+	if rt.username != "" {
+		t.Errorf("Bad HTTP client username: %s", rt.username)
+	}
+	if string(rt.usernameFile) != "testdata/basic-auth-username" {
+		t.Errorf("Bad HTTP client usernameFile: %s", rt.usernameFile)
+	}
+	if string(rt.passwordFile) != "testdata/basic-auth-password" {
+		t.Errorf("Bad HTTP client passwordFile: %s", rt.passwordFile)
+	}
+}
+
 func getCertificateBlobs(t *testing.T) map[string][]byte {
 	files := []string{
 		TLSCAChainPath,

config/testdata/basic-auth-username

@@ -0,0 +1 @@
+testuser

config/testdata/http.conf.basic-auth.bad-username.yaml

@@ -0,0 +1,4 @@
+basic_auth:
+  username: user
+  username_file: testdata/basic-auth-username
+  password: foo

config/testdata/http.conf.basic-auth.username-file.good.yaml

@@ -0,0 +1,3 @@
+basic_auth:
+  username_file: testdata/basic-auth-username
+  password_file: testdata/basic-auth-password