Validating the label values against regex

internal/config/config.go

@@ -931,7 +931,9 @@ func resolveLabels() map[string]interface{} {
 			result[trimmedKey] = parseJSON(trimmedValue)
 
 		default: // String
-			result[trimmedKey] = trimmedValue
+			if validateLabel(trimmedValue) {
+				result[trimmedKey] = trimmedValue
+			}
 		}
 	}
 
@@ -940,6 +942,17 @@ func resolveLabels() map[string]interface{} {
 	return result
 }
 
+func validateLabel(labelValue string) bool {
+	const maxLength = 256
+	labelPattern := regexp.MustCompile("^[a-zA-Z0-9]([a-zA-Z0-9-_]{0,254}[a-zA-Z0-9])?$")
+	if len(labelValue) > maxLength || !labelPattern.MatchString(labelValue) {
+		slog.Warn("Label value contains unsupported character ", "label_value", labelValue)
+		return false
+	}
+
+	return true
+}
+
 func resolveEnvironmentVariableLabels() map[string]string {
 	envLabels := make(map[string]string)
 	envInput := viperInstance.GetString(LabelsRootKey)

internal/config/config_test.go

@@ -1234,7 +1234,7 @@ func createConfig() *Config {
 						{
 							Action: "insert",
 							Key:    "label1",
-							Value:  "label 1",
+							Value:  "label-1",
 						},
 						{
 							Action: "insert",
@@ -1314,7 +1314,7 @@ func createConfig() *Config {
 			},
 		},
 		Labels: map[string]any{
-			"label1": "label 1",
+			"label1": "label-1",
 			"label2": "new-value",
 			"label3": 123,
 		},

internal/config/testdata/nginx-agent.conf

@@ -13,7 +13,7 @@ watchers:
                     - \.*log$
 
 labels:
-  label1: label 1
+  label1: label-1
   label2: new-value
   label3: 123