Add a new rule to detect integer overflow on integer types conversion

Signed-off-by: Cosmin Cojocar <cosmin@cojocar.ch>

analyzers/conversion_overflow.go

@@ -0,0 +1,134 @@
+// (c) Copyright gosec's authors
+//
+// 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 analyzers
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+
+	"github.com/securego/gosec/v2/issue"
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/buildssa"
+	"golang.org/x/tools/go/ssa"
+)
+
+func newConversionOverflowAnalyzer(id string, description string) *analysis.Analyzer {
+	return &analysis.Analyzer{
+		Name:     id,
+		Doc:      description,
+		Run:      runConversionOverflow,
+		Requires: []*analysis.Analyzer{buildssa.Analyzer},
+	}
+}
+
+func runConversionOverflow(pass *analysis.Pass) (interface{}, error) {
+	ssaResult, err := getSSAResult(pass)
+	if err != nil {
+		return nil, fmt.Errorf("building ssa representation: %w", err)
+	}
+
+	issues := []*issue.Issue{}
+	for _, mcall := range ssaResult.SSA.SrcFuncs {
+		for _, block := range mcall.DomPreorder() {
+			for _, instr := range block.Instrs {
+				switch instr := instr.(type) {
+				case *ssa.Convert:
+					src := instr.X.Type().String()
+					dst := instr.Type().String()
+					if isIntOverflow(src, dst) {
+						issue := newIssue(pass.Analyzer.Name,
+							fmt.Sprintf("integer overflow conversion %s -> %s", src, dst),
+							pass.Fset,
+							instr.Pos(),
+							issue.High,
+							issue.Medium,
+						)
+						issues = append(issues, issue)
+					}
+				}
+			}
+		}
+	}
+
+	if len(issues) > 0 {
+		return issues, nil
+	}
+	return nil, nil
+}
+
+type integer struct {
+	signed bool
+	size   int
+}
+
+func parseIntType(intType string) (integer, error) {
+	re := regexp.MustCompile(`(?P<type>u?int)(?P<size>\d{2})?`)
+	matches := re.FindStringSubmatch(intType)
+	if matches == nil {
+		return integer{}, fmt.Errorf("no integer type match found for %s", intType)
+	}
+
+	it := matches[re.SubexpIndex("type")]
+	is := matches[re.SubexpIndex("size")]
+
+	signed := false
+	if it == "int" {
+		signed = true
+	}
+
+	// use default system int type in case size is not present in the type
+	intSize := strconv.IntSize
+	if is != "" {
+		var err error
+		intSize, err = strconv.Atoi(is)
+		if err != nil {
+			return integer{}, fmt.Errorf("failed to parse the integer type size: %w", err)
+		}
+	}
+
+	return integer{signed: signed, size: intSize}, nil
+}
+
+func isIntOverflow(src string, dst string) bool {
+	srcInt, err := parseIntType(src)
+	if err != nil {
+		return false
+	}
+
+	dstInt, err := parseIntType(dst)
+	if err != nil {
+		return false
+	}
+
+	// converting uint to int of the same size or smaller might lead to overflow
+	if !srcInt.signed && dstInt.signed && dstInt.size <= srcInt.size {
+		return true
+	}
+	// converting uint to unit of a smaller size might lead to overflow
+	if !srcInt.signed && !dstInt.signed && dstInt.size < srcInt.size {
+		return true
+	}
+	// converting int to int of a smaller size might lead to overflow
+	if srcInt.signed && dstInt.signed && dstInt.size < srcInt.size {
+		return true
+	}
+	// converting int to uint of a smaller size might lead to overflow
+	if srcInt.signed && !dstInt.signed && dstInt.size < srcInt.size && srcInt.size-dstInt.size > 8 {
+		return true
+	}
+
+	return false
+}

analyzers/util.go

@@ -38,6 +38,7 @@ type SSAAnalyzerResult struct {
 // BuildDefaultAnalyzers returns the default list of analyzers
 func BuildDefaultAnalyzers() []*analysis.Analyzer {
 	return []*analysis.Analyzer{
+		newConversionOverflowAnalyzer("G115", "Type conversion which leads to integer overflow"),
 		newSliceBoundsAnalyzer("G602", "Possible slice bounds out of range"),
 	}
 }

rules/rules_test.go

@@ -111,6 +111,10 @@ var _ = Describe("gosec rules", func() {
 			runner("G114", testutils.SampleCodeG114)
 		})
 
+		It("should detect integer conversion overflow", func() {
+			runner("G115", testutils.SampleCodeG115)
+		})
+
 		It("should detect sql injection via format strings", func() {
 			runner("G201", testutils.SampleCodeG201)
 		})

testutils/g103_samples.go

@@ -27,7 +27,7 @@ func main() {
 	intPtr = (*int)(unsafe.Pointer(addressHolder))
 	fmt.Printf("\nintPtr=%p, *intPtr=%d.\n\n", intPtr, *intPtr)
 }
-`}, 2, gosec.NewConfig()},
+`}, 3, gosec.NewConfig()},
 	{[]string{`
 package main
 

testutils/g109_samples.go

@@ -20,7 +20,7 @@ func main() {
 	value := int32(bigValue)
 	fmt.Println(value)
 }
-`}, 1, gosec.NewConfig()},
+`}, 2, gosec.NewConfig()},
 	{[]string{`
 package main
 
@@ -38,7 +38,7 @@ func main() {
 		fmt.Println(bigValue)
 	}
 }
-`}, 1, gosec.NewConfig()},
+`}, 2, gosec.NewConfig()},
 	{[]string{`
 package main
 
@@ -74,7 +74,7 @@ func main() {
 
 func test() {
 	bigValue := 30
-	value := int32(bigValue)
+	value := int64(bigValue)
 	fmt.Println(value)
 }
 `}, 0, gosec.NewConfig()},
@@ -92,7 +92,7 @@ func main() {
 		value, _ := strconv.Atoi("2147483648")
 		fmt.Println(value)
 	}
-	v := int32(value)
+	v := int64(value)
 	fmt.Println(v)
 }
 `}, 0, gosec.NewConfig()},
@@ -105,7 +105,7 @@ import (
 )
 func main() {
 	a, err := strconv.Atoi("a")
-	b := int32(a) //#nosec G109
+	b := int64(a) //#nosec G109
 	fmt.Println(b, err)
 }
 `}, 0, gosec.NewConfig()},

testutils/g115_samples.go

@@ -0,0 +1,118 @@
+package testutils
+
+import "github.com/securego/gosec/v2"
+
+var SampleCodeG115 = []CodeSample{
+	{[]string{`
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+    var a uint32 = math.MaxUint32
+    b := int32(a)
+    fmt.Println(b)
+}
+	`}, 1, gosec.NewConfig()},
+	{[]string{`
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+    var a uint16 = math.MaxUint16
+    b := int32(a)
+    fmt.Println(b)
+}
+	`}, 0, gosec.NewConfig()},
+	{[]string{`
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+    var a uint32 = math.MaxUint32
+    b := uint16(a)
+    fmt.Println(b)
+}
+	`}, 1, gosec.NewConfig()},
+	{[]string{`
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+    var a int32 = math.MaxInt32
+    b := int16(a)
+    fmt.Println(b)
+}
+	`}, 1, gosec.NewConfig()},
+	{[]string{`
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+    var a int16 = math.MaxInt16
+    b := int32(a)
+    fmt.Println(b)
+}
+	`}, 0, gosec.NewConfig()},
+	{[]string{`
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+    var a int32 = math.MaxInt32
+    b := uint32(a)
+    fmt.Println(b)
+}
+	`}, 0, gosec.NewConfig()},
+	{[]string{`
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+    var a uint = math.MaxUint
+    b := int16(a)
+    fmt.Println(b)
+}
+	`}, 1, gosec.NewConfig()},
+	{[]string{`
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+    var a uint = math.MaxUint
+    b := int64(a)
+    fmt.Println(b)
+}
+	`}, 1, gosec.NewConfig()},
+}