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readfile.go
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/
readfile.go
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// (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 (
"go/ast"
"go/types"
"github.com/securego/gosec/v2"
)
type readfile struct {
gosec.MetaData
gosec.CallList
pathJoin gosec.CallList
clean gosec.CallList
}
// ID returns the identifier for this rule
func (r *readfile) ID() string {
return r.MetaData.ID
}
// isJoinFunc checks if there is a filepath.Join or other join function
func (r *readfile) isJoinFunc(n ast.Node, c *gosec.Context) bool {
if call := r.pathJoin.ContainsPkgCallExpr(n, c, false); call != nil {
for _, arg := range call.Args {
// edge case: check if one of the args is a BinaryExpr
if binExp, ok := arg.(*ast.BinaryExpr); ok {
// iterate and resolve all found identities from the BinaryExpr
if _, ok := gosec.FindVarIdentities(binExp, c); ok {
return true
}
}
// try and resolve identity
if ident, ok := arg.(*ast.Ident); ok {
obj := c.Info.ObjectOf(ident)
if _, ok := obj.(*types.Var); ok && !gosec.TryResolve(ident, c) {
return true
}
}
}
}
return false
}
// isFilepathClean checks if there is a filepath.Clean before assigning to a variable
func (r *readfile) isFilepathClean(n *ast.Ident, c *gosec.Context) bool {
if n.Obj.Kind != ast.Var {
return false
}
if node, ok := n.Obj.Decl.(*ast.AssignStmt); ok {
if call, ok := node.Rhs[0].(*ast.CallExpr); ok {
if clean := r.clean.ContainsPkgCallExpr(call, c, false); clean != nil {
return true
}
}
}
return false
}
// Match inspects AST nodes to determine if the match the methods `os.Open` or `ioutil.ReadFile`
func (r *readfile) Match(n ast.Node, c *gosec.Context) (*gosec.Issue, error) {
if node := r.ContainsPkgCallExpr(n, c, false); node != nil {
for _, arg := range node.Args {
// handles path joining functions in Arg
// eg. os.Open(filepath.Join("/tmp/", file))
if callExpr, ok := arg.(*ast.CallExpr); ok {
if r.isJoinFunc(callExpr, c) {
return gosec.NewIssue(c, n, r.ID(), r.What, r.Severity, r.Confidence), nil
}
}
// handles binary string concatenation eg. ioutil.Readfile("/tmp/" + file + "/blob")
if binExp, ok := arg.(*ast.BinaryExpr); ok {
// resolve all found identities from the BinaryExpr
if _, ok := gosec.FindVarIdentities(binExp, c); ok {
return gosec.NewIssue(c, n, r.ID(), r.What, r.Severity, r.Confidence), nil
}
}
if ident, ok := arg.(*ast.Ident); ok {
obj := c.Info.ObjectOf(ident)
if _, ok := obj.(*types.Var); ok &&
!gosec.TryResolve(ident, c) &&
!r.isFilepathClean(ident, c) {
return gosec.NewIssue(c, n, r.ID(), r.What, r.Severity, r.Confidence), nil
}
}
}
}
return nil, nil
}
// NewReadFile detects cases where we read files
func NewReadFile(id string, conf gosec.Config) (gosec.Rule, []ast.Node) {
rule := &readfile{
pathJoin: gosec.NewCallList(),
clean: gosec.NewCallList(),
CallList: gosec.NewCallList(),
MetaData: gosec.MetaData{
ID: id,
What: "Potential file inclusion via variable",
Severity: gosec.Medium,
Confidence: gosec.High,
},
}
rule.pathJoin.Add("path/filepath", "Join")
rule.pathJoin.Add("path", "Join")
rule.clean.Add("path/filepath", "Clean")
rule.clean.Add("path/filepath", "Rel")
rule.Add("io/ioutil", "ReadFile")
rule.Add("os", "ReadFile")
rule.Add("os", "Open")
rule.Add("os", "OpenFile")
rule.Add("os", "Create")
return rule, []ast.Node{(*ast.CallExpr)(nil)}
}