blob: 5e7ec4800bffa62245a9b54367ed771511647e4d [file] [log] [blame]
Pragya Arya324337e2020-02-20 14:35:08 +05301package rfc4757
2
3import (
4 "bytes"
5 "encoding/hex"
6 "errors"
7 "fmt"
8 "io"
9
10 "golang.org/x/crypto/md4"
11)
12
13// StringToKey returns a key derived from the string provided according to the definition in RFC 4757.
14func StringToKey(secret string) ([]byte, error) {
15 b := make([]byte, len(secret)*2, len(secret)*2)
16 for i, r := range secret {
17 u := fmt.Sprintf("%04x", r)
18 c, err := hex.DecodeString(u)
19 if err != nil {
20 return []byte{}, errors.New("character could not be encoded")
21 }
22 // Swap round the two bytes to make little endian as we put into byte slice
23 b[2*i] = c[1]
24 b[2*i+1] = c[0]
25 }
26 r := bytes.NewReader(b)
27 h := md4.New()
28 _, err := io.Copy(h, r)
29 if err != nil {
30 return []byte{}, err
31 }
32 return h.Sum(nil), nil
33}
34
35func deriveKeys(key, checksum []byte, usage uint32, export bool) (k1, k2, k3 []byte) {
36 //if export {
37 // L40 := make([]byte, 14, 14)
38 // copy(L40, []byte(`fortybits`))
39 // k1 = HMAC(key, L40)
40 //} else {
41 // tb := MessageTypeBytes(usage)
42 // k1 = HMAC(key, tb)
43 //}
44 //k2 = k1[:16]
45 //if export {
46 // mask := []byte{0xAB,0xAB,0xAB,0xAB,0xAB,0xAB,0xAB,0xAB,0xAB}
47 // copy(k1[7:16], mask)
48 //}
49 //k3 = HMAC(k1, checksum)
50 //return
51 k1 = key
52 k2 = HMAC(k1, UsageToMSMsgType(usage))
53 k3 = HMAC(k2, checksum)
54 return
55}