Add a rule which detects when there is potential integer overflow (#422)

* Add G109(Potential Integer OverFlow Detection)

Signed-off-by: Hiroki Suezawa <suezawa@gmail.com>

* add CWE to G109(Potential Integer Overflow)

Signed-off-by: Hiroki Suezawa <suezawa@gmail.com>

* Modify G109 to use gosec.Context

Signed-off-by: Hiroki Suezawa <suezawa@gmail.com>

README.md

@@ -71,6 +71,7 @@ directory you can supply `./...` as the input argument.
 - G106: Audit the use of ssh.InsecureIgnoreHostKey
 - G107: Url provided to HTTP request as taint input
 - G108: Profiling endpoint automatically exposed on /debug/pprof
+- G109: Potential Integer overflow made by strconv.Atoi result conversion to int16/32
 - G201: SQL query construction using format string
 - G202: SQL query construction using string concatenation
 - G203: Use of unescaped data in HTML templates

analyzer.go

@@ -47,15 +47,16 @@ const LoadMode = packages.NeedName |
 // It is passed through to all rule functions as they are called. Rules may use
 // this data in conjunction withe the encountered AST node.
 type Context struct {
-	FileSet  *token.FileSet
-	Comments ast.CommentMap
-	Info     *types.Info
-	Pkg      *types.Package
-	PkgFiles []*ast.File
-	Root     *ast.File
-	Config   Config
-	Imports  *ImportTracker
-	Ignores  []map[string]bool
+	FileSet      *token.FileSet
+	Comments     ast.CommentMap
+	Info         *types.Info
+	Pkg          *types.Package
+	PkgFiles     []*ast.File
+	Root         *ast.File
+	Config       Config
+	Imports      *ImportTracker
+	Ignores      []map[string]bool
+	PassedValues map[string]interface{}
 }
 
 // Metrics used when reporting information about a scanning run.
@@ -204,6 +205,7 @@ func (gosec *Analyzer) Check(pkg *packages.Package) {
 		gosec.context.PkgFiles = pkg.Syntax
 		gosec.context.Imports = NewImportTracker()
 		gosec.context.Imports.TrackFile(file)
+		gosec.context.PassedValues = make(map[string]interface{})
 		ast.Walk(gosec, file)
 		gosec.stats.NumFiles++
 		gosec.stats.NumLines += pkg.Fset.File(file.Pos()).LineCount()

issue.go

@@ -53,6 +53,7 @@ var IssueToCWE = map[string]Cwe{
 	"G104": GetCwe("703"),
 	"G106": GetCwe("322"),
 	"G107": GetCwe("88"),
+	"G109": GetCwe("190"),
 	"G201": GetCwe("89"),
 	"G202": GetCwe("89"),
 	"G203": GetCwe("79"),

output/formatter_test.go

@@ -250,9 +250,9 @@ var _ = Describe("Formatter", func() {
 	Context("When using different report formats", func() {
 
 		grules := []string{"G101", "G102", "G103", "G104", "G106",
-			"G107", "G201", "G202", "G203", "G204", "G301",
-			"G302", "G303", "G304", "G305", "G401", "G402",
-			"G403", "G404", "G501", "G502", "G503", "G504", "G505"}
+			"G107", "G109", "G201", "G202", "G203", "G204",
+			"G301", "G302", "G303", "G304", "G305", "G401",
+			"G402", "G403", "G404", "G501", "G502", "G503", "G504", "G505"}
 
 		It("csv formatted report should contain the CWE mapping", func() {
 			for _, rule := range grules {

rules/integer_overflow.go

@@ -0,0 +1,91 @@
+// (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 (
+	"fmt"
+	"github.com/securego/gosec"
+	"go/ast"
+)
+
+type integerOverflowCheck struct {
+	gosec.MetaData
+	calls gosec.CallList
+}
+
+func (i *integerOverflowCheck) ID() string {
+	return i.MetaData.ID
+}
+
+func (i *integerOverflowCheck) Match(node ast.Node, ctx *gosec.Context) (*gosec.Issue, error) {
+	var atoiVarName map[string]ast.Node
+
+	// To check multiple lines, ctx.PassedValues is used to store temporary data.
+	if _, ok := ctx.PassedValues[i.ID()]; !ok {
+		atoiVarName = make(map[string]ast.Node)
+		ctx.PassedValues[i.ID()] = atoiVarName
+	} else if pv, ok := ctx.PassedValues[i.ID()].(map[string]ast.Node); ok {
+		atoiVarName = pv
+	} else {
+		return nil, fmt.Errorf("PassedValues[%s] of Context is not map[string]ast.Node, but %T", i.ID(), ctx.PassedValues[i.ID()])
+	}
+
+	// strconv.Atoi is a common function.
+	// To reduce false positives, This rule detects code which is converted to int32/int16 only.
+	switch n := node.(type) {
+	case *ast.FuncDecl:
+		// Clear atoiVarName by function
+		ctx.PassedValues[i.ID()] = make(map[string]ast.Node)
+	case *ast.AssignStmt:
+		for _, expr := range n.Rhs {
+			if callExpr, ok := expr.(*ast.CallExpr); ok && i.calls.ContainsCallExpr(callExpr, ctx, false) != nil {
+				if idt, ok := n.Lhs[0].(*ast.Ident); ok && idt.Name != "_" {
+					// Example:
+					//  v, _ := strconv.Atoi("1111")
+					// Add "v" to atoiVarName map
+					atoiVarName[idt.Name] = n
+				}
+			}
+		}
+	case *ast.CallExpr:
+		if fun, ok := n.Fun.(*ast.Ident); ok {
+			if fun.Name == "int32" || fun.Name == "int16" {
+				if idt, ok := n.Args[0].(*ast.Ident); ok {
+					if n, ok := atoiVarName[idt.Name]; ok {
+						// Detect int32(v) and int16(v)
+						return gosec.NewIssue(ctx, n, i.ID(), i.What, i.Severity, i.Confidence), nil
+					}
+				}
+			}
+		}
+	}
+
+	return nil, nil
+}
+
+// NewIntegerOverflowCheck detects if there is potential Integer OverFlow
+func NewIntegerOverflowCheck(id string, conf gosec.Config) (gosec.Rule, []ast.Node) {
+	calls := gosec.NewCallList()
+	calls.Add("strconv", "Atoi")
+	return &integerOverflowCheck{
+		MetaData: gosec.MetaData{
+			ID:         id,
+			Severity:   gosec.High,
+			Confidence: gosec.Medium,
+			What:       "Potential Integer overflow made by strconv.Atoi result conversion to int16/32",
+		},
+		calls: calls,
+	}, []ast.Node{(*ast.FuncDecl)(nil), (*ast.AssignStmt)(nil), (*ast.CallExpr)(nil)}
+}

rules/rulelist.go

@@ -66,6 +66,7 @@ func Generate(filters ...RuleFilter) RuleList {
 		{"G106", "Audit the use of ssh.InsecureIgnoreHostKey function", NewSSHHostKey},
 		{"G107", "Url provided to HTTP request as taint input", NewSSRFCheck},
 		{"G108", "Profiling endpoint is automatically exposed", NewPprofCheck},
+		{"G109", "Converting strconv.Atoi result to int32/int16", NewIntegerOverflowCheck},
 
 		// injection
 		{"G201", "SQL query construction using format string", NewSQLStrFormat},

rules/rules_test.go

@@ -83,6 +83,10 @@ var _ = Describe("gosec rules", func() {
 			runner("G108", testutils.SampleCodeG108)
 		})
 
+		It("should detect integer overflow", func() {
+			runner("G109", testutils.SampleCodeG109)
+		})
+
 		It("should detect sql injection via format strings", func() {
 			runner("G201", testutils.SampleCodeG201)
 		})

testutils/pkg.go

@@ -109,12 +109,13 @@ func (p *TestPackage) CreateContext(filename string) *gosec.Context {
 			pkgFile = strings.TrimPrefix(pkgFile, strip)
 			if pkgFile == filename {
 				ctx := &gosec.Context{
-					FileSet: pkg.Fset,
-					Root:    file,
-					Config:  gosec.NewConfig(),
-					Info:    pkg.TypesInfo,
-					Pkg:     pkg.Types,
-					Imports: gosec.NewImportTracker(),
+					FileSet:      pkg.Fset,
+					Root:         file,
+					Config:       gosec.NewConfig(),
+					Info:         pkg.TypesInfo,
+					Pkg:          pkg.Types,
+					Imports:      gosec.NewImportTracker(),
+					PassedValues: make(map[string]interface{}),
 				}
 				ctx.Imports.TrackPackages(ctx.Pkg.Imports()...)
 				return ctx

testutils/source.go

@@ -522,6 +522,78 @@ func main() {
 	})
 	log.Fatal(http.ListenAndServe(":8080", nil))
 }`}, 0, gosec.NewConfig()}}
+
+	// SampleCodeG109 - Potential Integer OverFlow
+	SampleCodeG109 = []CodeSample{
+		// Bind to all networks explicitly
+		{[]string{`
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+func main() {
+	bigValue, err := strconv.Atoi("2147483648")
+	if err != nil {
+		panic(err)
+	}
+	value := int32(bigValue)
+	fmt.Println(value)
+}`}, 1, gosec.NewConfig()}, {[]string{`
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+func main() {
+	bigValue, err := strconv.Atoi("32768")
+	if err != nil {
+		panic(err)
+	}
+	if int16(bigValue) < 0 {
+		fmt.Println(bigValue)
+	}
+}`}, 1, gosec.NewConfig()}, {[]string{`
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+func main() {
+	bigValue, err := strconv.Atoi("2147483648")
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(bigValue)
+}`}, 0, gosec.NewConfig()}, {[]string{`
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+func main() {
+	bigValue, err := strconv.Atoi("2147483648")
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(bigValue)
+	test()
+}
+
+func test() {
+	bigValue := 30
+	value := int32(bigValue)
+	fmt.Println(value)
+}`}, 0, gosec.NewConfig()}}
+
 	// SampleCodeG201 - SQL injection via format string
 	SampleCodeG201 = []CodeSample{
 		{[]string{`