config: detect unknown fields in configs

config/config.go

@@ -56,6 +56,17 @@ func Parse(filename string) (*Config, map[int]bool, []*regexp.Regexp, error) {
 	if err != nil {
 		return nil, nil, nil, fmt.Errorf("failed to read config file: %v", err)
 	}
+	return parse(data)
+}
+
+func parse(data []byte) (*Config, map[int]bool, []*regexp.Regexp, error) {
+	unknown, err := checkUnknownFields(data)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+	if unknown != "" {
+		return nil, nil, nil, fmt.Errorf("unknown field '%v' in config", unknown)
+	}
 	cfg := new(Config)
 	cfg.Cover = true
 	cfg.DropPrivs = true
@@ -206,3 +217,51 @@ func CreateVMConfig(cfg *Config) (*vm.Config, error) {
 	}
 	return vmCfg, nil
 }
+
+func checkUnknownFields(data []byte) (string, error) {
+	// While https://github.com/golang/go/issues/15314 is not resolved
+	// we don't have a better way than to enumerate all known fields.
+	var fields = []string{
+		"Http",
+		"Workdir",
+		"Vmlinux",
+		"Kernel",
+		"Cmdline",
+		"Image",
+		"Cpu",
+		"Mem",
+		"Sshkey",
+		"Port",
+		"Bin",
+		"Debug",
+		"Output",
+		"Syzkaller",
+		"Type",
+		"Count",
+		"Procs",
+		"Cover",
+		"DropPrivs",
+		"Leak",
+		"ConsoleDev",
+		"Enable_Syscalls",
+		"Disable_Syscalls",
+		"Suppressions",
+	}
+	f := make(map[string]interface{})
+	if err := json.Unmarshal(data, &f); err != nil {
+		return "", fmt.Errorf("failed to parse config file: %v", err)
+	}
+	for k := range f {
+		ok := false
+		for _, k1 := range fields {
+			if strings.ToLower(k) == strings.ToLower(k1) {
+				ok = true
+				break
+			}
+		}
+		if !ok {
+			return k, nil
+		}
+	}
+	return "", nil
+}

config/config_test.go

@@ -0,0 +1,16 @@
+// Copyright 2016 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package config
+
+import (
+	"testing"
+)
+
+func TestUnknown(t *testing.T) {
+	data := `{"foo": "bar"}`
+	_, _, _, err := parse([]byte(data))
+	if err == nil || err.Error() != "unknown field 'foo' in config" {
+		t.Fatalf("unknown field is not detected (%v)", err)
+	}
+}