Better error handling in x.Parse (#4987)

Robust key length checks

(cherry picked from commit d0bfee7)

x/keys.go

@@ -438,16 +438,26 @@ func SplitKey(baseKey []byte, startUid uint64) ([]byte, error) {
 func Parse(key []byte) (ParsedKey, error) {
 	var p ParsedKey
 
+	if len(key) == 0 {
+		return p, errors.Errorf("0 length key")
+	}
+
 	p.bytePrefix = key[0]
 	if p.bytePrefix == ByteUnused {
 		return p, nil
 	}
 
 	p.HasStartUid = key[0] == ByteSplit
 
+	if len(key) < 3 {
+		return p, errors.Errorf("Invalid format for key %v", key)
+	}
 	sz := int(binary.BigEndian.Uint16(key[1:3]))
 	k := key[3:]
 
+	if len(k) < sz {
+		return p, errors.Errorf("Invalid size %v for key %v", sz, key)
+	}
 	p.Attr = string(k[:sz])
 	k = k[sz:]
 

x/keys_test.go

@@ -232,3 +232,24 @@ func TestBadStartUid(t *testing.T) {
 	key = CountKey("aa", 0, true)
 	testKey(key)
 }
+
+func TestBadKeys(t *testing.T) {
+	// 0-len key
+	key := []byte{}
+	_, err := Parse(key)
+	require.Error(t, err)
+
+	// key of len < 3
+	key = []byte{1}
+	_, err = Parse(key)
+	require.Error(t, err)
+
+	key = []byte{1, 2}
+	_, err = Parse(key)
+	require.Error(t, err)
+
+	// key of len < sz (key[1], key[2])
+	key = []byte{1, 0x00, 0x04, 1, 2}
+	_, err = Parse(key)
+	require.Error(t, err)
+}