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
|
package cryptfs
import (
"encoding/json"
"fmt"
"io/ioutil"
)
import "os"
const (
// The dot "." is not used in base64url (RFC4648), hence
// we can never clash with an encrypted file.
ConfDefaultName = "gocryptfs.conf"
)
type ConfFile struct {
// File the config is saved to. Not exported to JSON.
filename string
// Encrypted AES key, unlocked using a password hashed with scrypt
EncryptedKey []byte
// Stores parameters for scrypt hashing (key derivation)
ScryptObject scryptKdf
// The On-Disk-Format version this filesystem uses
Version uint16
// Do not encrypt filenames
PlaintextNames bool
}
// CreateConfFile - create a new config with a random key encrypted with
// "password" and write it to "filename"
func CreateConfFile(filename string, password string, plaintextNames bool) error {
var cf ConfFile
cf.filename = filename
// Generate new random master key
key := RandBytes(KEY_LEN)
// Encrypt it using the password
// This sets ScryptObject and EncryptedKey
cf.EncryptKey(key, password)
cf.Version = HEADER_CURRENT_VERSION
cf.PlaintextNames = plaintextNames
// Write file to disk
return cf.WriteFile()
}
// LoadConfFile - read config file from disk and decrypt the
// contained key using password
func LoadConfFile(filename string, password string) ([]byte, *ConfFile, error) {
var cf ConfFile
cf.filename = filename
// Read from disk
js, err := ioutil.ReadFile(filename)
if err != nil {
return nil, nil, err
}
// Unmarshal
err = json.Unmarshal(js, &cf)
if err != nil {
Warn.Printf("Failed to unmarshal config file\n")
return nil, nil, err
}
if cf.Version != HEADER_CURRENT_VERSION {
return nil, nil, fmt.Errorf("Unsupported version %d", cf.Version)
}
// Generate derived key from password
scryptHash := cf.ScryptObject.DeriveKey(password)
// Unlock master key using password-based key
// We use stock go GCM instead of OpenSSL here as speed is not important
// and we get better error messages
cfs := NewCryptFS(scryptHash, false, false)
key, err := cfs.DecryptBlock(cf.EncryptedKey, 0, nil)
if err != nil {
Warn.Printf("failed to unlock master key: %s\n", err.Error())
Warn.Printf("Password incorrect.\n")
return nil, nil, err
}
return key, &cf, nil
}
// EncryptKey - encrypt "key" using an scrypt hash generated from "password"
// and store it in cf.EncryptedKey
func (cf *ConfFile) EncryptKey(key []byte, password string) {
// Generate derived key from password
cf.ScryptObject = NewScryptKdf()
scryptHash := cf.ScryptObject.DeriveKey(password)
// Lock master key using password-based key
cfs := NewCryptFS(scryptHash, false, false)
cf.EncryptedKey = cfs.EncryptBlock(key, 0, nil)
}
// WriteFile - write out config in JSON format to file "filename.tmp"
// then rename over "filename"
func (cf *ConfFile) WriteFile() error {
tmp := cf.filename + ".tmp"
fd, err := os.Create(tmp)
if err != nil {
return err
}
js, err := json.MarshalIndent(cf, "", "\t")
if err != nil {
return err
}
_, err = fd.Write(js)
if err != nil {
return err
}
err = fd.Sync()
if err != nil {
return err
}
err = fd.Close()
if err != nil {
return err
}
err = os.Rename(tmp, cf.filename)
if err != nil {
return err
}
return nil
}
|
