Merge pull request securego#114 from GoASTScanner/feature

Consider entropy when warning on hardcoded credentials

.travis.yml

@@ -1,6 +1,6 @@
 language: go
 before_script:
-  - go vet ./...
+  - go vet $(go list ./... | grep -v /vendor/)
 go:
   - 1.5
   - tip

rules/hardcoded_credentials.go

@@ -19,11 +19,34 @@ import (
 	"go/ast"
 	"go/token"
 	"regexp"
+
+	"github.com/nbutton23/zxcvbn-go"
+	"strconv"
 )
 
 type Credentials struct {
 	gas.MetaData
-	pattern *regexp.Regexp
+	pattern          *regexp.Regexp
+	entropyThreshold float64
+	perCharThreshold float64
+	truncate         int
+	ignoreEntropy    bool
+}
+
+func truncate(s string, n int) string {
+	if n > len(s) {
+		return s
+	}
+	return s[:n]
+}
+
+func (r *Credentials) isHighEntropyString(str string) bool {
+	s := truncate(str, r.truncate)
+	info := zxcvbn.PasswordStrength(s, []string{})
+	entropyPerChar := info.Entropy / float64(len(s))
+	return (info.Entropy >= r.entropyThreshold ||
+		(info.Entropy >= (r.entropyThreshold/2) &&
+			entropyPerChar >= r.perCharThreshold))
 }
 
 func (r *Credentials) Match(n ast.Node, ctx *gas.Context) (*gas.Issue, error) {
@@ -41,8 +64,10 @@ func (r *Credentials) matchAssign(assign *ast.AssignStmt, ctx *gas.Context) (*ga
 		if ident, ok := i.(*ast.Ident); ok {
 			if r.pattern.MatchString(ident.Name) {
 				for _, e := range assign.Rhs {
-					if rhs, ok := e.(*ast.BasicLit); ok && rhs.Kind == token.STRING {
-						return gas.NewIssue(ctx, assign, r.What, r.Severity, r.Confidence), nil
+					if val, err := gas.GetString(e); err == nil {
+						if r.ignoreEntropy || (!r.ignoreEntropy && r.isHighEntropyString(val)) {
+							return gas.NewIssue(ctx, assign, r.What, r.Severity, r.Confidence), nil
+						}
 					}
 				}
 			}
@@ -63,8 +88,10 @@ func (r *Credentials) matchGenDecl(decl *ast.GenDecl, ctx *gas.Context) (*gas.Is
 					if len(valueSpec.Values) <= index {
 						index = len(valueSpec.Values) - 1
 					}
-					if rhs, ok := valueSpec.Values[index].(*ast.BasicLit); ok && rhs.Kind == token.STRING {
-						return gas.NewIssue(ctx, valueSpec, r.What, r.Severity, r.Confidence), nil
+					if val, err := gas.GetString(valueSpec.Values[index]); err == nil {
+						if r.ignoreEntropy || (!r.ignoreEntropy && r.isHighEntropyString(val)) {
+							return gas.NewIssue(ctx, valueSpec, r.What, r.Severity, r.Confidence), nil
+						}
 					}
 				}
 			}
@@ -75,11 +102,43 @@ func (r *Credentials) matchGenDecl(decl *ast.GenDecl, ctx *gas.Context) (*gas.Is
 
 func NewHardcodedCredentials(conf map[string]interface{}) (gas.Rule, []ast.Node) {
 	pattern := `(?i)passwd|pass|password|pwd|secret|token`
+	entropyThreshold := 80.0
+	perCharThreshold := 3.0
+	ignoreEntropy := false
+	var truncateString int = 16
 	if val, ok := conf["G101"]; ok {
-		pattern = val.(string)
+		conf := val.(map[string]string)
+		if configPattern, ok := conf["pattern"]; ok {
+			pattern = configPattern
+		}
+		if configIgnoreEntropy, ok := conf["ignore_entropy"]; ok {
+			if parsedBool, err := strconv.ParseBool(configIgnoreEntropy); err == nil {
+				ignoreEntropy = parsedBool
+			}
+		}
+		if configEntropyThreshold, ok := conf["entropy_threshold"]; ok {
+			if parsedNum, err := strconv.ParseFloat(configEntropyThreshold, 64); err == nil {
+				entropyThreshold = parsedNum
+			}
+		}
+		if configCharThreshold, ok := conf["per_char_threshold"]; ok {
+			if parsedNum, err := strconv.ParseFloat(configCharThreshold, 64); err == nil {
+				perCharThreshold = parsedNum
+			}
+		}
+		if configTruncate, ok := conf["truncate"]; ok {
+			if parsedInt, err := strconv.Atoi(configTruncate); err == nil {
+				truncateString = parsedInt
+			}
+		}
 	}
+
 	return &Credentials{
-		pattern: regexp.MustCompile(pattern),
+		pattern:          regexp.MustCompile(pattern),
+		entropyThreshold: entropyThreshold,
+		perCharThreshold: perCharThreshold,
+		ignoreEntropy:    ignoreEntropy,
+		truncate:         truncateString,
 		MetaData: gas.MetaData{
 			What:       "Potential hardcoded credentials",
 			Confidence: gas.Low,

rules/hardcoded_credentials_test.go

@@ -25,6 +25,51 @@ func TestHardcoded(t *testing.T) {
 	analyzer := gas.NewAnalyzer(config, nil)
 	analyzer.AddRule(NewHardcodedCredentials(config))
 
+	issues := gasTestRunner(
+		`
+		package samples
+
+		import "fmt"
+
+		func main() {
+			username := "admin"
+			password := "f62e5bcda4fae4f82370da0c6f20697b8f8447ef"
+			fmt.Println("Doing something with: ", username, password)
+		}`, analyzer)
+
+	checkTestResults(t, issues, 1, "Potential hardcoded credentials")
+}
+
+func TestHardcodedWithEntropy(t *testing.T) {
+	config := map[string]interface{}{"ignoreNosec": false}
+	analyzer := gas.NewAnalyzer(config, nil)
+	analyzer.AddRule(NewHardcodedCredentials(config))
+
+	issues := gasTestRunner(
+		`
+		package samples
+
+		import "fmt"
+
+		func main() {
+			username := "admin"
+			password := "secret"
+			fmt.Println("Doing something with: ", username, password)
+		}`, analyzer)
+
+	checkTestResults(t, issues, 0, "Potential hardcoded credentials")
+}
+
+func TestHardcodedIgnoreEntropy(t *testing.T) {
+	config := map[string]interface{}{
+		"ignoreNosec": false,
+		"G101": map[string]string{
+			"ignore_entropy": "true",
+		},
+	}
+	analyzer := gas.NewAnalyzer(config, nil)
+	analyzer.AddRule(NewHardcodedCredentials(config))
+
 	issues := gasTestRunner(
 		`
 		package samples
@@ -50,7 +95,7 @@ func TestHardcodedGlobalVar(t *testing.T) {
 
 		import "fmt"
 
-		var password = "admin"
+		var password = "f62e5bcda4fae4f82370da0c6f20697b8f8447ef"
 
 		func main() {
 			username := "admin"
@@ -70,7 +115,7 @@ func TestHardcodedConstant(t *testing.T) {
 
 		import "fmt"
 
-		const password = "secret"
+		const password = "f62e5bcda4fae4f82370da0c6f20697b8f8447ef"
 
 		func main() {
 			username := "admin"
@@ -92,7 +137,7 @@ func TestHardcodedConstantMulti(t *testing.T) {
 
 		const (
 			username = "user"
-			password = "secret"
+			password = "f62e5bcda4fae4f82370da0c6f20697b8f8447ef"
 		)
 
 		func main() {
@@ -110,7 +155,7 @@ func TestHardecodedVarsNotAssigned(t *testing.T) {
 		package main
 		var password string
 		func init() {
-			password = "this is a secret string"
+			password = "f62e5bcda4fae4f82370da0c6f20697b8f8447ef"
 		}`, analyzer)
 	checkTestResults(t, issues, 1, "Potential hardcoded credentials")
 }
@@ -140,7 +185,7 @@ func TestHardcodedConstString(t *testing.T) {
 		package main
 
 		const (
-			ATNStateTokenStart = "foo bar"
+			ATNStateTokenStart = "f62e5bcda4fae4f82370da0c6f20697b8f8447ef"
 		)
 		func main() {
 			println(ATNStateTokenStart)

vendor.conf

@@ -1,2 +1,7 @@
-# Import path             | revision                               | Repository(optional)
-github.com/ryanuber/go-glob 572520ed46dbddaed19ea3d9541bdd0494163693
+# package
+github.com/GoAstScanner/gas
+
+# import
+github.com/GoASTScanner/gas	cc52ef5
+github.com/nbutton23/zxcvbn-go	a22cb81
+github.com/ryanuber/go-glob	v0.1