Add a test for math/big.Int.Exp rule

Author: Cosmin Cojocar

rules/big.go

@@ -26,17 +26,17 @@ type UsingBigExp struct {
 }
 
 func (r *UsingBigExp) Match(n ast.Node, c *gas.Context) (gi *gas.Issue, err error) {
-	if _, matches := gas.MatchCallByPackage(n, c, r.pkg, r.calls...); matches {
+	if _, matched := gas.MatchCallByType(n, c, r.pkg, r.calls...); matched {
 		return gas.NewIssue(c, n, r.What, r.Severity, r.Confidence), nil
 	}
 	return nil, nil
 }
 func NewUsingBigExp(conf map[string]interface{}) (gas.Rule, []ast.Node) {
 	return &UsingBigExp{
-		pkg:   "big",
+		pkg:   "*math/big.Int",
 		calls: []string{"Exp"},
 		MetaData: gas.MetaData{
-			What:       "Use of big.Exp call should be audited for modulus == 0",
+			What:       "Use of math/big.Int.Exp function should be audited for modulus == 0",
 			Severity:   gas.Low,
 			Confidence: gas.High,
 		},

rules/big_test.go

@@ -0,0 +1,49 @@
+// (c) Copyright 2016 Hewlett Packard Enterprise Development LP
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package rules
+
+import (
+	"testing"
+
+	gas "github.com/GoASTScanner/gas/core"
+)
+
+func TestBigExp(t *testing.T) {
+	config := map[string]interface{}{"ignoreNosec": false}
+	analyzer := gas.NewAnalyzer(config, nil)
+	analyzer.AddRule(NewUsingBigExp(config))
+
+	issues := gasTestRunner(`
+        package main
+
+        import (
+        	"math/big"
+        )
+
+        func main() {
+            z := new(big.Int)
+            x := new(big.Int)
+            x = x.SetUint64(2)
+            y := new(big.Int)
+            y = y.SetUint64(4)
+            m := new(big.Int)
+            m = m.SetUint64(0)
+
+            z = z.Exp(x, y, m)
+        }
+        `, analyzer)
+
+	checkTestResults(t, issues, 1, "Use of math/big.Int.Exp function")
+}