1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
// Package readpassword reads a password from the terminal of from stdin.
package readpassword
import (
"bytes"
"fmt"
"io"
"os"
"os/exec"
"strings"
"sync"
"time"
"golang.org/x/crypto/ssh/terminal"
"github.com/rfjakob/gocryptfs/internal/exitcodes"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
const (
// 2kB limit like EncFS
maxPasswordLen = 2048
)
// Once tries to get a password from the user, either from the terminal, extpass
// or stdin.
func Once(extpass string) []byte {
if extpass != "" {
return readPasswordExtpass(extpass)
}
if !terminal.IsTerminal(int(os.Stdin.Fd())) {
return readPasswordStdin()
}
return readPasswordTerminal("Password: ")
}
// Twice is the same as Once but will prompt twice if we get the password from
// the terminal.
func Twice(extpass string) []byte {
if extpass != "" {
return readPasswordExtpass(extpass)
}
if !terminal.IsTerminal(int(os.Stdin.Fd())) {
return readPasswordStdin()
}
p1 := readPasswordTerminal("Password: ")
p2 := readPasswordTerminal("Repeat: ")
if !bytes.Equal(p1, p2) {
tlog.Fatal.Println("Passwords do not match")
os.Exit(exitcodes.ReadPassword)
}
return p1
}
// readPasswordTerminal reads a line from the terminal.
// Exits on read error or empty result.
func readPasswordTerminal(prompt string) []byte {
fd := int(os.Stdin.Fd())
fmt.Fprintf(os.Stderr, prompt)
// terminal.ReadPassword removes the trailing newline
p, err := terminal.ReadPassword(fd)
if err != nil {
tlog.Fatal.Printf("Could not read password from terminal: %v\n", err)
os.Exit(exitcodes.ReadPassword)
}
fmt.Fprintf(os.Stderr, "\n")
if len(p) == 0 {
tlog.Fatal.Println("Password is empty")
os.Exit(exitcodes.PasswordEmpty)
}
return p
}
// readPasswordStdin reads a line from stdin.
// It exits with a fatal error on read error or empty result.
func readPasswordStdin() []byte {
tlog.Info.Println("Reading password from stdin")
p := readLineUnbuffered(os.Stdin)
if len(p) == 0 {
tlog.Fatal.Println("Got empty password from stdin")
os.Exit(exitcodes.ReadPassword)
}
return p
}
// readPasswordExtpass executes the "extpass" program and returns the first line
// of the output.
// Exits on read error or empty result.
func readPasswordExtpass(extpass string) []byte {
tlog.Info.Println("Reading password from extpass program")
var parts []string
// The option "-passfile=FILE" gets transformed to
// "-extpass="/bin/cat -- FILE". We don't want to split FILE on spaces,
// so let's handle it manually.
passfileCat := "/bin/cat -- "
if strings.HasPrefix(extpass, passfileCat) {
parts = []string{"/bin/cat", "--", extpass[len(passfileCat):]}
} else {
parts = strings.Split(extpass, " ")
}
cmd := exec.Command(parts[0], parts[1:]...)
cmd.Stderr = os.Stderr
pipe, err := cmd.StdoutPipe()
if err != nil {
tlog.Fatal.Printf("extpass pipe setup failed: %v", err)
os.Exit(exitcodes.ReadPassword)
}
err = cmd.Start()
if err != nil {
tlog.Fatal.Printf("extpass cmd start failed: %v", err)
os.Exit(exitcodes.ReadPassword)
}
p := readLineUnbuffered(pipe)
pipe.Close()
err = cmd.Wait()
if err != nil {
tlog.Fatal.Printf("extpass program returned an error: %v", err)
os.Exit(exitcodes.ReadPassword)
}
if len(p) == 0 {
tlog.Fatal.Println("extpass: password is empty")
os.Exit(exitcodes.ReadPassword)
}
return p
}
// readLineUnbuffered reads single bytes from "r" util it gets "\n" or EOF.
// The returned string does NOT contain the trailing "\n".
func readLineUnbuffered(r io.Reader) (l []byte) {
b := make([]byte, 1)
for {
if len(l) > maxPasswordLen {
tlog.Fatal.Printf("fatal: maximum password length of %d bytes exceeded", maxPasswordLen)
os.Exit(exitcodes.ReadPassword)
}
n, err := r.Read(b)
if err == io.EOF {
return l
}
if err != nil {
tlog.Fatal.Printf("readLineUnbuffered: %v", err)
os.Exit(exitcodes.ReadPassword)
}
if n == 0 {
continue
}
if b[0] == '\n' {
return l
}
l = append(l, b...)
}
}
// CheckTrailingGarbage tries to read one byte from stdin and exits with a
// fatal error if the read returns any data.
// This is meant to be called after reading the password, when there is no more
// data expected. This helps to catch problems with third-party tools that
// interface with gocryptfs.
//
// This is tested via TestInitTrailingGarbage() in tests/cli/cli_test.go.
func CheckTrailingGarbage() {
if terminal.IsTerminal(int(os.Stdin.Fd())) {
// Be lenient when interacting with a human.
return
}
var wg sync.WaitGroup
wg.Add(1)
go func() {
b := make([]byte, 1)
wg.Done()
n, _ := os.Stdin.Read(b)
if n > 0 {
tlog.Fatal.Printf("Received trailing garbage after the password")
os.Exit(exitcodes.ReadPassword)
}
}()
// Wait for the goroutine to start up plus one millisecond for the read to
// return. If there is data available, this SHOULD be plenty of time to
// read one byte. However, I don't see a way to be sure.
wg.Wait()
time.Sleep(1 * time.Millisecond)
}
|
