1// (c) Copyright 2016 Hewlett Packard Enterprise Development LP
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package rules
16
17import (
18	"go/ast"
19	"go/types"
20
21	"github.com/securego/gosec/v2"
22)
23
24type readfile struct {
25	gosec.MetaData
26	gosec.CallList
27	pathJoin gosec.CallList
28}
29
30// ID returns the identifier for this rule
31func (r *readfile) ID() string {
32	return r.MetaData.ID
33}
34
35// isJoinFunc checks if there is a filepath.Join or other join function
36func (r *readfile) isJoinFunc(n ast.Node, c *gosec.Context) bool {
37	if call := r.pathJoin.ContainsPkgCallExpr(n, c, false); call != nil {
38		for _, arg := range call.Args {
39			// edge case: check if one of the args is a BinaryExpr
40			if binExp, ok := arg.(*ast.BinaryExpr); ok {
41				// iterate and resolve all found identities from the BinaryExpr
42				if _, ok := gosec.FindVarIdentities(binExp, c); ok {
43					return true
44				}
45			}
46
47			// try and resolve identity
48			if ident, ok := arg.(*ast.Ident); ok {
49				obj := c.Info.ObjectOf(ident)
50				if _, ok := obj.(*types.Var); ok && !gosec.TryResolve(ident, c) {
51					return true
52				}
53			}
54		}
55	}
56	return false
57}
58
59// Match inspects AST nodes to determine if the match the methods `os.Open` or `ioutil.ReadFile`
60func (r *readfile) Match(n ast.Node, c *gosec.Context) (*gosec.Issue, error) {
61	if node := r.ContainsPkgCallExpr(n, c, false); node != nil {
62		for _, arg := range node.Args {
63			// handles path joining functions in Arg
64			// eg. os.Open(filepath.Join("/tmp/", file))
65			if callExpr, ok := arg.(*ast.CallExpr); ok {
66				if r.isJoinFunc(callExpr, c) {
67					return gosec.NewIssue(c, n, r.ID(), r.What, r.Severity, r.Confidence), nil
68				}
69			}
70			// handles binary string concatenation eg. ioutil.Readfile("/tmp/" + file + "/blob")
71			if binExp, ok := arg.(*ast.BinaryExpr); ok {
72				// resolve all found identities from the BinaryExpr
73				if _, ok := gosec.FindVarIdentities(binExp, c); ok {
74					return gosec.NewIssue(c, n, r.ID(), r.What, r.Severity, r.Confidence), nil
75				}
76			}
77
78			if ident, ok := arg.(*ast.Ident); ok {
79				obj := c.Info.ObjectOf(ident)
80				if _, ok := obj.(*types.Var); ok && !gosec.TryResolve(ident, c) {
81					return gosec.NewIssue(c, n, r.ID(), r.What, r.Severity, r.Confidence), nil
82				}
83			}
84		}
85	}
86	return nil, nil
87}
88
89// NewReadFile detects cases where we read files
90func NewReadFile(id string, conf gosec.Config) (gosec.Rule, []ast.Node) {
91	rule := &readfile{
92		pathJoin: gosec.NewCallList(),
93		CallList: gosec.NewCallList(),
94		MetaData: gosec.MetaData{
95			ID:         id,
96			What:       "Potential file inclusion via variable",
97			Severity:   gosec.Medium,
98			Confidence: gosec.High,
99		},
100	}
101	rule.pathJoin.Add("path/filepath", "Join")
102	rule.pathJoin.Add("path", "Join")
103	rule.Add("io/ioutil", "ReadFile")
104	rule.Add("os", "Open")
105	rule.Add("os", "OpenFile")
106	return rule, []ast.Node{(*ast.CallExpr)(nil)}
107}
108