Validate LabelName/LabelSet on JSON unmarshaling.

model/labelname.go

@@ -14,6 +14,7 @@
 package model
 
 import (
+	"encoding/json"
 	"fmt"
 	"regexp"
 	"strings"
@@ -81,6 +82,19 @@ func (ln *LabelName) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	return nil
 }
 
+// UnmarshalJSON implements the json.Unmarshaler interface.
+func (ln *LabelName) UnmarshalJSON(b []byte) error {
+	var s string
+	if err := json.Unmarshal(b, &s); err != nil {
+		return err
+	}
+	if !LabelNameRE.MatchString(s) {
+		return fmt.Errorf("%q is not a valid label name", s)
+	}
+	*ln = LabelName(s)
+	return nil
+}
+
 // LabelNames is a sortable LabelName slice. In implements sort.Interface.
 type LabelNames []LabelName
 

model/labelset.go

@@ -14,6 +14,7 @@
 package model
 
 import (
+	"encoding/json"
 	"fmt"
 	"sort"
 	"strings"
@@ -62,3 +63,21 @@ func (l LabelSet) MergeFromMetric(m Metric) {
 		l[k] = v
 	}
 }
+
+// UnmarshalJSON implements the json.Unmarshaler interface.
+func (l *LabelSet) UnmarshalJSON(b []byte) error {
+	var m map[LabelName]LabelValue
+	if err := json.Unmarshal(b, &m); err != nil {
+		return err
+	}
+	// encoding/json only unmarshals maps of the form map[string]T. It treats
+	// LabelName as a string and does not call its UnmarshalJSON method.
+	// Thus, we have to replicate the behavior here.
+	for ln := range m {
+		if !LabelNameRE.MatchString(string(ln)) {
+			return fmt.Errorf("%q is not a valid label name", ln)
+		}
+	}
+	*l = LabelSet(m)
+	return nil
+}