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
183
184
185
186
187
188
189
190
191
192
193
194
195
196
|
package cryptokit
import (
"bytes"
"errors"
"fmt"
"os"
"os/exec"
"path/filepath"
"strings"
)
const maxYubiCryptMessageBytes = 64 << 20
type limitedBuffer struct {
buffer bytes.Buffer
limit int
}
func (b *limitedBuffer) Write(value []byte) (int, error) {
remaining := b.limit - b.buffer.Len()
if remaining <= 0 {
return len(value), nil
}
if len(value) > remaining {
_, _ = b.buffer.Write(value[:remaining])
return len(value), nil
}
return b.buffer.Write(value)
}
var yubiCryptCandidates = []string{
"/home/gabriel1/bin/yubicrypt",
"/home/gabriel1/bin/yubicrpt-cli",
"/home/gabriel1/Projects/yubicrpt-cli/yubicrypt",
"/home/gabriel1/Projects/yubicrpt-cli/yubicrpt-cli",
"/usr/local/bin/yubicrypt",
"/usr/bin/yubicrypt",
}
// FindYubiCryptCLI returns the optional yubicrypt-cli executable. An explicit
// AEGIS_YUBICRYPT_CLI path takes precedence over the standard locations.
func FindYubiCryptCLI() (string, error) {
if configured := strings.TrimSpace(os.Getenv("AEGIS_YUBICRYPT_CLI")); configured != "" {
if isExecutableBinary(configured) {
return configured, nil
}
return "", fmt.Errorf("AEGIS_YUBICRYPT_CLI is not executable: %s", configured)
}
for _, candidate := range yubiCryptCandidates {
if isExecutableBinary(candidate) {
return candidate, nil
}
}
if path, err := exec.LookPath("yubicrypt"); err == nil {
return path, nil
}
return "", errors.New("yubicrypt-cli executable not found; set AEGIS_YUBICRYPT_CLI or install yubicrypt")
}
func isExecutableBinary(path string) bool {
info, err := os.Stat(path)
return err == nil && info.Mode().IsRegular() && info.Mode()&0o111 != 0
}
func runYubiCrypt(args []string, input []byte) ([]byte, error) {
executable, err := FindYubiCryptCLI()
if err != nil {
return nil, err
}
command := exec.Command(executable, args...)
command.Stdin = bytes.NewReader(input)
var stdout limitedBuffer
var stderr bytes.Buffer
stdout.limit = maxYubiCryptMessageBytes + 1
command.Stdout = &stdout
command.Stderr = &stderr
if err := command.Run(); err != nil {
return nil, fmt.Errorf("yubicrypt %s: %w: %s", firstCommandArg(args), err, cleanCommandError(stderr.String()))
}
if stdout.buffer.Len() > maxYubiCryptMessageBytes {
return nil, errors.New("yubicrypt output exceeds the 64 MiB limit")
}
return stdout.buffer.Bytes(), nil
}
func firstCommandArg(args []string) string {
if len(args) == 0 {
return "operation"
}
return args[0]
}
func cleanCommandError(value string) string {
value = strings.TrimSpace(value)
if len(value) > 1000 {
return value[:1000] + "..."
}
if value == "" {
return "command failed"
}
return value
}
func withYubiTemp(operation func(directory string) error) error {
directory, err := os.MkdirTemp("", "aegis-yubicrypt-")
if err != nil {
return fmt.Errorf("create temporary YubiCrypt directory: %w", err)
}
defer os.RemoveAll(directory)
if err := os.Chmod(directory, 0o700); err != nil {
return fmt.Errorf("protect temporary YubiCrypt directory: %w", err)
}
return operation(directory)
}
func writeYubiTemp(directory, name string, data []byte) (string, error) {
path := filepath.Join(directory, name)
file, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o600)
if err != nil {
return "", fmt.Errorf("create temporary YubiCrypt input: %w", err)
}
if _, err := file.Write(data); err != nil {
_ = file.Close()
return "", fmt.Errorf("write temporary YubiCrypt input: %w", err)
}
if err := file.Close(); err != nil {
return "", fmt.Errorf("close temporary YubiCrypt input: %w", err)
}
return path, nil
}
func checkYubiMessageSize(message []byte) error {
if len(message) > maxYubiCryptMessageBytes {
return errors.New("message exceeds the 64 MiB limit")
}
return nil
}
func requireYubiPIN(pin string) ([]byte, error) {
pin = strings.TrimRight(pin, "\r\n")
if pin == "" {
return nil, errors.New("YubiKey PIV PIN is required")
}
return []byte(pin + "\n"), nil
}
// SignYubiCrypt signs with the YubiKey PIV slot 9c. The PIN is sent through
// stdin to yubicrypt-cli and is not placed in command arguments or logs.
func SignYubiCrypt(message []byte, pin string) ([]byte, error) {
if err := checkYubiMessageSize(message); err != nil {
return nil, err
}
pinInput, err := requireYubiPIN(pin)
if err != nil {
return nil, err
}
var result []byte
err = withYubiTemp(func(directory string) error {
messagePath, err := writeYubiTemp(directory, "message.bin", message)
if err != nil {
return err
}
result, err = runYubiCrypt([]string{
"sign", "--quiet", "--pin-stdin", "--input", messagePath, "--output", "-",
}, pinInput)
if err != nil {
return fmt.Errorf("YubiCrypt signing failed: %w", err)
}
return nil
})
return result, err
}
// VerifyYubiCrypt verifies a yubicrypt signature block and returns the
// original message only after the CLI has authenticated it.
func VerifyYubiCrypt(signedMessage []byte) ([]byte, error) {
if err := checkYubiMessageSize(signedMessage); err != nil {
return nil, err
}
var result []byte
err := withYubiTemp(func(directory string) error {
signedPath, err := writeYubiTemp(directory, "signed.yc", signedMessage)
if err != nil {
return err
}
result, err = runYubiCrypt([]string{
"verify", "--quiet", "--input", signedPath, "--message-output", "-",
}, nil)
if err != nil {
return fmt.Errorf("YubiCrypt verification failed: %w", err)
}
return nil
})
return result, err
}
|
