From 7ee20d77cbb00ce040169993da778d3c85c70dcf Mon Sep 17 00:00:00 2001
From: Marco Jantke <marco.jantke@gmail.com>
Date: Sat, 19 Aug 2017 23:31:56 +0200
Subject: [PATCH] validate ConstLabels values in NewDesc

---
 prometheus/desc.go      |  7 +++++++
 prometheus/desc_test.go | 17 +++++++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 prometheus/desc_test.go

diff --git a/prometheus/desc.go b/prometheus/desc.go
index 1835b16..4c67346 100644
--- a/prometheus/desc.go
+++ b/prometheus/desc.go
@@ -122,6 +122,12 @@ func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *
 	for _, labelName := range labelNames {
 		labelValues = append(labelValues, constLabels[labelName])
 	}
+	// Validate the const label values. They can't have a wrong cardinality, so
+	// use in len(labelValues) as expectedNumberOfValues.
+	if err := validateLabelValues(labelValues, len(labelValues)); err != nil {
+		d.err = err
+		return d
+	}
 	// Now add the variable label names, but prefix them with something that
 	// cannot be in a regular label name. That prevents matching the label
 	// dimension with a different mix between preset and variable labels.
@@ -137,6 +143,7 @@ func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *
 		d.err = errors.New("duplicate label names")
 		return d
 	}
+
 	vh := hashNew()
 	for _, val := range labelValues {
 		vh = hashAdd(vh, val)
diff --git a/prometheus/desc_test.go b/prometheus/desc_test.go
new file mode 100644
index 0000000..2f96265
--- /dev/null
+++ b/prometheus/desc_test.go
@@ -0,0 +1,17 @@
+package prometheus
+
+import (
+	"testing"
+)
+
+func TestNewDescInvalidLabelValues(t *testing.T) {
+	desc := NewDesc(
+		"sample_label",
+		"sample label",
+		nil,
+		Labels{"a": "\xFF"},
+	)
+	if desc.err == nil {
+		t.Errorf("NewDesc: expected error because: %s", desc.err)
+	}
+}