Add fuzz testing to 'serv' for the GQL hash parser

serv/corpus/001.gql

@@ -0,0 +1,21 @@
+query {
+  products(
+    # returns only 30 items
+    limit: 30,
+
+    # starts from item 10, commented out for now
+    # offset: 10,
+
+    # orders the response items by highest price
+    order_by: { price: desc },
+
+    # no duplicate prices returned
+    distinct: [ price ]
+    
+    # only items with an id >= 30 and < 30 are returned
+    where: { id: { and: { greater_or_equals: 20, lt: 28 } } }) {
+    id
+    name
+    price
+  }
+}

serv/fuzz.go

@@ -0,0 +1,9 @@
+package serv
+
+func Fuzz(data []byte) int {
+	gql := string(data)
+	isMutation(gql)
+	gqlHash(gql, nil, "")
+
+	return 1
+}

serv/fuzz_test.go

@@ -0,0 +1,16 @@
+package serv
+
+import "testing"
+
+func TestFuzzCrashers(t *testing.T) {
+	var crashers = []string{
+		"query",
+		"q",
+		"que",
+	}
+
+	for _, f := range crashers {
+		isMutation(f)
+		gqlHash(f, nil, "")
+	}
+}

serv/utils.go

@@ -32,6 +32,10 @@ func gqlHash(b string, vars []byte, role string) string {
 
 	var b0, b1 byte
 
+	if len(b) == 0 {
+		return ""
+	}
+
 	for {
 		if starting && b[e] == 'q' {
 			n := 0
@@ -44,6 +48,9 @@ func gqlHash(b string, vars []byte, role string) string {
 				io.WriteString(h, strings.ToLower(b[se:e]))
 			}
 		}
+		if e >= len(b) {
+			break
+		}
 		if ws(b[e]) {
 			for e < len(b) && ws(b[e]) {
 				e++