111 lines
3.6 KiB
Go
111 lines
3.6 KiB
Go
// (c) Copyright 2016 Hewlett Packard Enterprise Development LP
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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 rules
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import (
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"fmt"
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"go/ast"
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"github.com/securego/gosec/v2"
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)
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type decompressionBombCheck struct {
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gosec.MetaData
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readerCalls gosec.CallList
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copyCalls gosec.CallList
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}
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func (d *decompressionBombCheck) ID() string {
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return d.MetaData.ID
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}
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func containsReaderCall(node ast.Node, ctx *gosec.Context, list gosec.CallList) bool {
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if list.ContainsPkgCallExpr(node, ctx, false) != nil {
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return true
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}
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// Resolve type info of ident (for *archive/zip.File.Open)
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s, idt, _ := gosec.GetCallInfo(node, ctx)
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return list.Contains(s, idt)
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}
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func (d *decompressionBombCheck) Match(node ast.Node, ctx *gosec.Context) (*gosec.Issue, error) {
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var readerVarObj map[*ast.Object]struct{}
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// To check multiple lines, ctx.PassedValues is used to store temporary data.
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if _, ok := ctx.PassedValues[d.ID()]; !ok {
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readerVarObj = make(map[*ast.Object]struct{})
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ctx.PassedValues[d.ID()] = readerVarObj
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} else if pv, ok := ctx.PassedValues[d.ID()].(map[*ast.Object]struct{}); ok {
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readerVarObj = pv
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} else {
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return nil, fmt.Errorf("PassedValues[%s] of Context is not map[*ast.Object]struct{}, but %T", d.ID(), ctx.PassedValues[d.ID()])
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}
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// io.Copy is a common function.
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// To reduce false positives, This rule detects code which is used for compressed data only.
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switch n := node.(type) {
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case *ast.AssignStmt:
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for _, expr := range n.Rhs {
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if callExpr, ok := expr.(*ast.CallExpr); ok && containsReaderCall(callExpr, ctx, d.readerCalls) {
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if idt, ok := n.Lhs[0].(*ast.Ident); ok && idt.Name != "_" {
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// Example:
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// r, _ := zlib.NewReader(buf)
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// Add r's Obj to readerVarObj map
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readerVarObj[idt.Obj] = struct{}{}
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}
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}
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}
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case *ast.CallExpr:
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if d.copyCalls.ContainsPkgCallExpr(n, ctx, false) != nil {
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if idt, ok := n.Args[1].(*ast.Ident); ok {
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if _, ok := readerVarObj[idt.Obj]; ok {
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// Detect io.Copy(x, r)
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return gosec.NewIssue(ctx, n, d.ID(), d.What, d.Severity, d.Confidence), nil
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}
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}
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}
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}
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return nil, nil
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}
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// NewDecompressionBombCheck detects if there is potential DoS vulnerability via decompression bomb
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func NewDecompressionBombCheck(id string, conf gosec.Config) (gosec.Rule, []ast.Node) {
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readerCalls := gosec.NewCallList()
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readerCalls.Add("compress/gzip", "NewReader")
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readerCalls.AddAll("compress/zlib", "NewReader", "NewReaderDict")
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readerCalls.Add("compress/bzip2", "NewReader")
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readerCalls.AddAll("compress/flate", "NewReader", "NewReaderDict")
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readerCalls.Add("compress/lzw", "NewReader")
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readerCalls.Add("archive/tar", "NewReader")
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readerCalls.Add("archive/zip", "NewReader")
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readerCalls.Add("*archive/zip.File", "Open")
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copyCalls := gosec.NewCallList()
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copyCalls.Add("io", "Copy")
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copyCalls.Add("io", "CopyBuffer")
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return &decompressionBombCheck{
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MetaData: gosec.MetaData{
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ID: id,
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Severity: gosec.Medium,
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Confidence: gosec.Medium,
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What: "Potential DoS vulnerability via decompression bomb",
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},
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readerCalls: readerCalls,
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copyCalls: copyCalls,
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}, []ast.Node{(*ast.FuncDecl)(nil), (*ast.AssignStmt)(nil), (*ast.CallExpr)(nil)}
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}
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