mirror of
https://github.com/securego/gosec.git
synced 2024-11-05 11:35:51 +00:00
560 lines
14 KiB
Go
560 lines
14 KiB
Go
// (c) Copyright gosec's authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package analyzers
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import (
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"fmt"
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"go/token"
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"math"
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"regexp"
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"strconv"
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"strings"
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"golang.org/x/exp/constraints"
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"golang.org/x/tools/go/analysis"
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"golang.org/x/tools/go/analysis/passes/buildssa"
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"golang.org/x/tools/go/ssa"
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"github.com/securego/gosec/v2/issue"
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)
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type integer struct {
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signed bool
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size int
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min int
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max uint
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}
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type rangeResult struct {
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minValue int
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maxValue uint
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explicitPositiveVals []uint
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explicitNegativeVals []int
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isRangeCheck bool
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convertFound bool
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}
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type branchResults struct {
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minValue *int
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maxValue *uint
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explixitPositiveVals []uint
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explicitNegativeVals []int
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convertFound bool
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}
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func newConversionOverflowAnalyzer(id string, description string) *analysis.Analyzer {
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return &analysis.Analyzer{
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Name: id,
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Doc: description,
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Run: runConversionOverflow,
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Requires: []*analysis.Analyzer{buildssa.Analyzer},
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}
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}
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func runConversionOverflow(pass *analysis.Pass) (interface{}, error) {
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ssaResult, err := getSSAResult(pass)
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if err != nil {
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return nil, fmt.Errorf("building ssa representation: %w", err)
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}
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issues := []*issue.Issue{}
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for _, mcall := range ssaResult.SSA.SrcFuncs {
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for _, block := range mcall.DomPreorder() {
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for _, instr := range block.Instrs {
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switch instr := instr.(type) {
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case *ssa.Convert:
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src := instr.X.Type().Underlying().String()
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dst := instr.Type().Underlying().String()
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if isIntOverflow(src, dst) {
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if isSafeConversion(instr) {
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continue
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}
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issue := newIssue(pass.Analyzer.Name,
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fmt.Sprintf("integer overflow conversion %s -> %s", src, dst),
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pass.Fset,
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instr.Pos(),
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issue.High,
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issue.Medium,
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)
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issues = append(issues, issue)
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}
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}
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}
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}
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}
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if len(issues) > 0 {
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return issues, nil
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}
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return nil, nil
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}
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func isIntOverflow(src string, dst string) bool {
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srcInt, err := parseIntType(src)
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if err != nil {
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return false
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}
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dstInt, err := parseIntType(dst)
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if err != nil {
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return false
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}
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return srcInt.min < dstInt.min || srcInt.max > dstInt.max
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}
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func parseIntType(intType string) (integer, error) {
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re := regexp.MustCompile(`^(?P<type>u?int)(?P<size>\d{1,2})?$`)
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matches := re.FindStringSubmatch(intType)
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if matches == nil {
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return integer{}, fmt.Errorf("no integer type match found for %s", intType)
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}
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it := matches[re.SubexpIndex("type")]
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is := matches[re.SubexpIndex("size")]
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signed := it == "int"
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// use default system int type in case size is not present in the type.
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intSize := strconv.IntSize
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if is != "" {
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var err error
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intSize, err = strconv.Atoi(is)
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if err != nil {
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return integer{}, fmt.Errorf("failed to parse the integer type size: %w", err)
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}
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}
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if intSize != 8 && intSize != 16 && intSize != 32 && intSize != 64 && is != "" {
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return integer{}, fmt.Errorf("invalid bit size: %d", intSize)
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}
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var min int
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var max uint
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if signed {
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shiftAmount := intSize - 1
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// Perform a bounds check.
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if shiftAmount < 0 {
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return integer{}, fmt.Errorf("invalid shift amount: %d", shiftAmount)
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}
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max = (1 << uint(shiftAmount)) - 1
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min = -1 << (intSize - 1)
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} else {
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max = (1 << uint(intSize)) - 1
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min = 0
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}
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return integer{
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signed: signed,
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size: intSize,
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min: min,
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max: max,
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}, nil
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}
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func isSafeConversion(instr *ssa.Convert) bool {
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dstType := instr.Type().Underlying().String()
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// Check for constant conversions.
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if constVal, ok := instr.X.(*ssa.Const); ok {
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if isConstantInRange(constVal, dstType) {
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return true
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}
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}
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// Check for string to integer conversions with specified bit size.
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if isStringToIntConversion(instr, dstType) {
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return true
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}
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// Check for explicit range checks.
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if hasExplicitRangeCheck(instr, dstType) {
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return true
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}
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return false
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}
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func isConstantInRange(constVal *ssa.Const, dstType string) bool {
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value, err := strconv.ParseInt(constVal.Value.String(), 10, 64)
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if err != nil {
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return false
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}
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dstInt, err := parseIntType(dstType)
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if err != nil {
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return false
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}
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if dstInt.signed {
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return value >= -(1<<(dstInt.size-1)) && value <= (1<<(dstInt.size-1))-1
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}
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return value >= 0 && value <= (1<<dstInt.size)-1
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}
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func isStringToIntConversion(instr *ssa.Convert, dstType string) bool {
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// Traverse the SSA instructions to find the original variable.
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original := instr.X
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for {
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switch v := original.(type) {
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case *ssa.Call:
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if v.Call.StaticCallee() != nil && (v.Call.StaticCallee().Name() == "ParseInt" || v.Call.StaticCallee().Name() == "ParseUint") {
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if len(v.Call.Args) == 3 {
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if bitSize, ok := v.Call.Args[2].(*ssa.Const); ok {
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signed := v.Call.StaticCallee().Name() == "ParseInt"
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bitSizeValue, err := strconv.Atoi(bitSize.Value.String())
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if err != nil {
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return false
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}
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dstInt, err := parseIntType(dstType)
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if err != nil {
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return false
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}
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isSafe := bitSizeValue <= dstInt.size && signed == dstInt.signed
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return isSafe
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}
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}
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}
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return false
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case *ssa.Phi:
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original = v.Edges[0]
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case *ssa.Extract:
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original = v.Tuple
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default:
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return false
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}
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}
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}
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func hasExplicitRangeCheck(instr *ssa.Convert, dstType string) bool {
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dstInt, err := parseIntType(dstType)
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if err != nil {
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return false
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}
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srcInt, err := parseIntType(instr.X.Type().String())
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if err != nil {
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return false
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}
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minValue := srcInt.min
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maxValue := srcInt.max
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explicitPositiveVals := []uint{}
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explicitNegativeVals := []int{}
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if minValue > dstInt.min && maxValue < dstInt.max {
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return true
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}
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visitedIfs := make(map[*ssa.If]bool)
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for _, block := range instr.Parent().Blocks {
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for _, blockInstr := range block.Instrs {
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switch v := blockInstr.(type) {
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case *ssa.If:
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result := getResultRange(v, instr, visitedIfs)
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if result.isRangeCheck {
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minValue = max(minValue, &result.minValue)
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maxValue = min(maxValue, &result.maxValue)
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explicitPositiveVals = append(explicitPositiveVals, result.explicitPositiveVals...)
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explicitNegativeVals = append(explicitNegativeVals, result.explicitNegativeVals...)
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}
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case *ssa.Call:
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// These function return an int of a guaranteed size.
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if v != instr.X {
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continue
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}
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if fn, isBuiltin := v.Call.Value.(*ssa.Builtin); isBuiltin {
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switch fn.Name() {
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case "len", "cap":
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minValue = 0
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}
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}
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}
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if explicitValsInRange(explicitPositiveVals, explicitNegativeVals, dstInt) {
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return true
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} else if minValue >= dstInt.min && maxValue <= dstInt.max {
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return true
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}
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}
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}
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return false
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}
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// getResultRange is a recursive function that walks the branches of the if statement to find the range of the variable.
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func getResultRange(ifInstr *ssa.If, instr *ssa.Convert, visitedIfs map[*ssa.If]bool) rangeResult {
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if visitedIfs[ifInstr] {
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return rangeResult{minValue: math.MinInt, maxValue: math.MaxUint}
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}
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visitedIfs[ifInstr] = true
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cond := ifInstr.Cond
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binOp, ok := cond.(*ssa.BinOp)
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if !ok || !isRangeCheck(binOp, instr.X) {
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return rangeResult{minValue: math.MinInt, maxValue: math.MaxUint}
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}
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result := rangeResult{
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minValue: math.MinInt,
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maxValue: math.MaxUint,
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isRangeCheck: true,
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}
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thenBounds := walkBranchForConvert(ifInstr.Block().Succs[0], instr, visitedIfs)
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elseBounds := walkBranchForConvert(ifInstr.Block().Succs[1], instr, visitedIfs)
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updateResultFromBinOp(&result, binOp, instr, thenBounds.convertFound)
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if thenBounds.convertFound {
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result.convertFound = true
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result.minValue = max(result.minValue, thenBounds.minValue)
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result.maxValue = min(result.maxValue, thenBounds.maxValue)
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} else if elseBounds.convertFound {
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result.convertFound = true
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result.minValue = max(result.minValue, elseBounds.minValue)
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result.maxValue = min(result.maxValue, elseBounds.maxValue)
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}
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result.explicitPositiveVals = append(result.explicitPositiveVals, thenBounds.explixitPositiveVals...)
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result.explicitNegativeVals = append(result.explicitNegativeVals, thenBounds.explicitNegativeVals...)
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result.explicitPositiveVals = append(result.explicitPositiveVals, elseBounds.explixitPositiveVals...)
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result.explicitNegativeVals = append(result.explicitNegativeVals, elseBounds.explicitNegativeVals...)
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return result
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}
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// updateResultFromBinOp updates the rangeResult based on the BinOp instruction and the location of the Convert instruction.
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func updateResultFromBinOp(result *rangeResult, binOp *ssa.BinOp, instr *ssa.Convert, successPathConvert bool) {
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x, y := binOp.X, binOp.Y
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operandsFlipped := false
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compareVal, op := getRealValueFromOperation(instr.X)
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// Handle FieldAddr
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if fieldAddr, ok := compareVal.(*ssa.FieldAddr); ok {
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compareVal = fieldAddr
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}
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if !isSameOrRelated(x, compareVal) {
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y = x
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operandsFlipped = true
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}
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constVal, ok := y.(*ssa.Const)
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if !ok {
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return
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}
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// TODO: constVal.Value nil check avoids #1229 panic but seems to be hiding a bug in the code above or in x/tools/go/ssa.
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if constVal.Value == nil {
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// log.Fatalf("[gosec] constVal.Value is nil flipped=%t, constVal=%#v, binOp=%#v", operandsFlipped, constVal, binOp)
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return
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}
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switch binOp.Op {
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case token.LEQ, token.LSS:
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updateMinMaxForLessOrEqual(result, constVal, binOp.Op, operandsFlipped, successPathConvert)
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case token.GEQ, token.GTR:
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updateMinMaxForGreaterOrEqual(result, constVal, binOp.Op, operandsFlipped, successPathConvert)
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case token.EQL:
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if !successPathConvert {
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break
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}
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updateExplicitValues(result, constVal)
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case token.NEQ:
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if successPathConvert {
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break
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}
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updateExplicitValues(result, constVal)
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}
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if op == "neg" {
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min := result.minValue
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max := result.maxValue
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if min >= 0 {
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result.maxValue = uint(min)
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}
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if max <= math.MaxInt {
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result.minValue = int(max)
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}
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}
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}
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func updateExplicitValues(result *rangeResult, constVal *ssa.Const) {
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if strings.Contains(constVal.String(), "-") {
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result.explicitNegativeVals = append(result.explicitNegativeVals, int(constVal.Int64()))
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} else {
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result.explicitPositiveVals = append(result.explicitPositiveVals, uint(constVal.Uint64()))
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}
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}
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func updateMinMaxForLessOrEqual(result *rangeResult, constVal *ssa.Const, op token.Token, operandsFlipped bool, successPathConvert bool) {
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// If the success path has a conversion and the operands are not flipped, then the constant value is the maximum value.
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if successPathConvert && !operandsFlipped {
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result.maxValue = uint(constVal.Uint64())
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if op == token.LEQ {
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result.maxValue--
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}
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} else {
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result.minValue = int(constVal.Int64())
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if op == token.GTR {
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result.minValue++
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}
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}
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}
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func updateMinMaxForGreaterOrEqual(result *rangeResult, constVal *ssa.Const, op token.Token, operandsFlipped bool, successPathConvert bool) {
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// If the success path has a conversion and the operands are not flipped, then the constant value is the minimum value.
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if successPathConvert && !operandsFlipped {
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result.minValue = int(constVal.Int64())
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if op == token.GEQ {
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result.minValue++
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}
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} else {
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result.maxValue = uint(constVal.Uint64())
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if op == token.LSS {
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result.maxValue--
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}
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}
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}
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// walkBranchForConvert walks the branch of the if statement to find the range of the variable and where the conversion is.
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func walkBranchForConvert(block *ssa.BasicBlock, instr *ssa.Convert, visitedIfs map[*ssa.If]bool) branchResults {
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bounds := branchResults{}
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for _, blockInstr := range block.Instrs {
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switch v := blockInstr.(type) {
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case *ssa.If:
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result := getResultRange(v, instr, visitedIfs)
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bounds.convertFound = bounds.convertFound || result.convertFound
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if result.isRangeCheck {
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bounds.minValue = toPtr(max(result.minValue, bounds.minValue))
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bounds.maxValue = toPtr(min(result.maxValue, bounds.maxValue))
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bounds.explixitPositiveVals = append(bounds.explixitPositiveVals, result.explicitPositiveVals...)
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bounds.explicitNegativeVals = append(bounds.explicitNegativeVals, result.explicitNegativeVals...)
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}
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case *ssa.Call:
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if v == instr.X {
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if fn, isBuiltin := v.Call.Value.(*ssa.Builtin); isBuiltin && (fn.Name() == "len" || fn.Name() == "cap") {
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bounds.minValue = toPtr(0)
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}
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}
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case *ssa.Convert:
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if v == instr {
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bounds.convertFound = true
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return bounds
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}
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}
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}
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return bounds
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}
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func isRangeCheck(v ssa.Value, x ssa.Value) bool {
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compareVal, _ := getRealValueFromOperation(x)
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switch op := v.(type) {
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case *ssa.BinOp:
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switch op.Op {
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case token.LSS, token.LEQ, token.GTR, token.GEQ, token.EQL, token.NEQ:
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leftMatch := isSameOrRelated(op.X, compareVal)
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rightMatch := isSameOrRelated(op.Y, compareVal)
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return leftMatch || rightMatch
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}
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}
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return false
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}
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func getRealValueFromOperation(v ssa.Value) (ssa.Value, string) {
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switch v := v.(type) {
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case *ssa.UnOp:
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if v.Op == token.SUB {
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val, _ := getRealValueFromOperation(v.X)
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return val, "neg"
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}
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return getRealValueFromOperation(v.X)
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case *ssa.FieldAddr:
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return v, "field"
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case *ssa.Alloc:
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return v, "alloc"
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}
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return v, ""
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}
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func isSameOrRelated(a, b ssa.Value) bool {
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aVal, _ := getRealValueFromOperation(a)
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bVal, _ := getRealValueFromOperation(b)
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if aVal == bVal {
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return true
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}
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// Check if both are FieldAddr operations referring to the same field of the same struct
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if aField, aOk := aVal.(*ssa.FieldAddr); aOk {
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if bField, bOk := bVal.(*ssa.FieldAddr); bOk {
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return aField.X == bField.X && aField.Field == bField.Field
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}
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}
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return false
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}
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func explicitValsInRange(explicitPosVals []uint, explicitNegVals []int, dstInt integer) bool {
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if len(explicitPosVals) == 0 && len(explicitNegVals) == 0 {
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return false
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}
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for _, val := range explicitPosVals {
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if val > dstInt.max {
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return false
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}
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}
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for _, val := range explicitNegVals {
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if val < dstInt.min {
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return false
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}
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}
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return true
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}
|
|
|
|
func min[T constraints.Integer](a T, b *T) T {
|
|
if b == nil {
|
|
return a
|
|
}
|
|
if a < *b {
|
|
return a
|
|
}
|
|
return *b
|
|
}
|
|
|
|
func max[T constraints.Integer](a T, b *T) T {
|
|
if b == nil {
|
|
return a
|
|
}
|
|
if a > *b {
|
|
return a
|
|
}
|
|
return *b
|
|
}
|
|
|
|
func toPtr[T any](a T) *T {
|
|
return &a
|
|
}
|