Validating the label values against regex

internal/config/config.go

@@ -46,7 +46,8 @@ const (
 
 	// Regular expression to match invalid characters in paths.
 	// It matches whitespace, control characters, non-printable characters, and specific Unicode characters.
-	regexInvalidPath = "\\s|[[:cntrl:]]|[[:space:]]|[[^:print:]]|ㅤ|\\.\\.|\\*"
+	regexInvalidPath  = "\\s|[[:cntrl:]]|[[:space:]]|[[^:print:]]|ㅤ|\\.\\.|\\*"
+	regexLabelPattern = "^[a-zA-Z0-9]([a-zA-Z0-9-_]{0,254}[a-zA-Z0-9])?$"
 )
 
 var viperInstance = viper.NewWithOptions(viper.KeyDelimiter(KeyDelimiter))
@@ -931,7 +932,9 @@ func resolveLabels() map[string]interface{} {
 			result[trimmedKey] = parseJSON(trimmedValue)
 
 		default: // String
-			result[trimmedKey] = trimmedValue
+			if validateLabel(trimmedValue) {
+				result[trimmedKey] = trimmedValue
+			}
 		}
 	}
 
@@ -940,6 +943,19 @@ func resolveLabels() map[string]interface{} {
 	return result
 }
 
+func validateLabel(labelValue string) bool {
+	const maxLength = 256
+	labelPattern := regexp.MustCompile(regexLabelPattern)
+	if len(labelValue) > maxLength || !labelPattern.MatchString(labelValue) {
+		slog.Warn("Label value contains unsupported character or exceed maximum length of 256 characters ",
+			"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,
 		},
@@ -1410,3 +1410,59 @@ func createDefaultCollectorConfig() *Collector {
 		},
 	}
 }
+
+func TestValidateLabel(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected bool
+	}{
+		{
+			name:     "Test 1: Valid label - simple",
+			input:    "label123",
+			expected: true,
+		},
+		{
+			name:     "Test 2: Valid label - with dash and underscore",
+			input:    "label-123_abc",
+			expected: true,
+		},
+		{
+			name:     "Test 3: Invalid label - too long",
+			input:    strings.Repeat("a", 257),
+			expected: false,
+		},
+		{
+			name:     "Test 4: Invalid label - special char",
+			input:    "label$",
+			expected: false,
+		},
+		{
+			name:     "Test 5: Invalid label - starts with dash",
+			input:    "-label",
+			expected: false,
+		},
+		{
+			name:     "Test 6: Invalid label - ends with dash",
+			input:    "label-",
+			expected: false,
+		},
+		{
+			name:     "Test 7: Invalid label - empty",
+			input:    "",
+			expected: false,
+		},
+		{
+			name:     "Test 8: Invalid label - contains spaces",
+			input:    "label 123",
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			actual := validateLabel(tt.input)
+			assert.Equal(t, tt.expected, actual)
+		})
+	}
+}

internal/config/testdata/nginx-agent.conf

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