agent: reject config with invalid options

command/agent/config.go

@@ -474,6 +474,20 @@ func DecodeConfig(r io.Reader) (*Config, error) {
 		return nil, err
 	}
 
+	// Check unused fields and verify that no bad configuration options were
+	// passed to Consul. There are a few additional fields which don't directly
+	// use mapstructure decoding, so we need to account for those as well.
+	allowedKeys := []string{"service", "services", "check", "checks"}
+	var unused []string
+	for _, field := range md.Unused {
+		if !strContains(allowedKeys, field) {
+			unused = append(unused, field)
+		}
+	}
+	if len(unused) > 0 {
+		return nil, fmt.Errorf("Config has invalid keys: %s", strings.Join(unused, ","))
+	}
+
 	// Handle time conversions
 	if raw := result.DNSConfig.NodeTTLRaw; raw != "" {
 		dur, err := time.ParseDuration(raw)

command/agent/config_test.go

@@ -7,6 +7,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"strings"
 	"testing"
 	"time"
 )
@@ -591,6 +592,14 @@ func TestDecodeConfig(t *testing.T) {
 	}
 }
 
+func TestDecodeConfig_invalidKeys(t *testing.T) {
+	input := `{"bad": "no way jose"}`
+	_, err := DecodeConfig(bytes.NewReader([]byte(input)))
+	if err == nil || !strings.Contains(err.Error(), "invalid keys") {
+		t.Fatalf("should have rejected invalid config keys")
+	}
+}
+
 func TestDecodeConfig_Services(t *testing.T) {
 	input := `{
 		"services": [