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package wgcfg
import (
"bytes"
"crypto/rand"
"crypto/subtle"
"encoding/base64"
"encoding/hex"
"errors"
"fmt"
"strings"
"golang.org/x/crypto/chacha20poly1305"
"golang.org/x/crypto/curve25519"
)
const KeySize = 32
// Key is curve25519 key.
// It is used by WireGuard to represent public and preshared keys.
type Key [KeySize]byte
// NewPresharedKey generates a new random key.
func NewPresharedKey() (*Key, error) {
var k [KeySize]byte
_, err := rand.Read(k[:])
if err != nil {
return nil, err
}
return (*Key)(&k), nil
}
func ParseKey(b64 string) (*Key, error) { return parseKeyBase64(base64.StdEncoding, b64) }
func ParseHexKey(s string) (Key, error) {
b, err := hex.DecodeString(s)
if err != nil {
return Key{}, &ParseError{"invalid hex key: " + err.Error(), s}
}
if len(b) != KeySize {
return Key{}, &ParseError{fmt.Sprintf("invalid hex key length: %d", len(b)), s}
}
var key Key
copy(key[:], b)
return key, nil
}
func ParsePrivateHexKey(v string) (PrivateKey, error) {
k, err := ParseHexKey(v)
if err != nil {
return PrivateKey{}, err
}
pk := PrivateKey(k)
if pk.IsZero() {
// Do not clamp a zero key, pass the zero through
// (much like NaN propagation) so that IsZero reports
// a useful result.
return pk, nil
}
pk.clamp()
return pk, nil
}
func (k Key) Base64() string { return base64.StdEncoding.EncodeToString(k[:]) }
func (k Key) String() string { return "pub:" + k.Base64()[:8] }
func (k Key) HexString() string { return hex.EncodeToString(k[:]) }
func (k Key) Equal(k2 Key) bool { return subtle.ConstantTimeCompare(k[:], k2[:]) == 1 }
func (k *Key) ShortString() string {
if k.IsZero() {
return "[empty]"
}
long := k.String()
if len(long) < 10 {
return "invalid"
}
return "[" + long[0:4] + "…" + long[len(long)-5:len(long)-1] + "]"
}
func (k *Key) IsZero() bool {
if k == nil {
return true
}
var zeros Key
return subtle.ConstantTimeCompare(zeros[:], k[:]) == 1
}
func (k *Key) MarshalJSON() ([]byte, error) {
if k == nil {
return []byte("null"), nil
}
buf := new(bytes.Buffer)
fmt.Fprintf(buf, `"%x"`, k[:])
return buf.Bytes(), nil
}
func (k *Key) UnmarshalJSON(b []byte) error {
if k == nil {
return errors.New("wgcfg.Key: UnmarshalJSON on nil pointer")
}
if len(b) < 3 || b[0] != '"' || b[len(b)-1] != '"' {
return errors.New("wgcfg.Key: UnmarshalJSON not given a string")
}
b = b[1 : len(b)-1]
key, err := ParseHexKey(string(b))
if err != nil {
return fmt.Errorf("wgcfg.Key: UnmarshalJSON: %v", err)
}
copy(k[:], key[:])
return nil
}
func (a *Key) LessThan(b *Key) bool {
for i := range a {
if a[i] < b[i] {
return true
} else if a[i] > b[i] {
return false
}
}
return false
}
// PrivateKey is curve25519 key.
// It is used by WireGuard to represent private keys.
type PrivateKey [KeySize]byte
// NewPrivateKey generates a new curve25519 secret key.
// It conforms to the format described on https://cr.yp.to/ecdh.html.
func NewPrivateKey() (PrivateKey, error) {
k, err := NewPresharedKey()
if err != nil {
return PrivateKey{}, err
}
k[0] &= 248
k[31] = (k[31] & 127) | 64
return (PrivateKey)(*k), nil
}
func ParsePrivateKey(b64 string) (*PrivateKey, error) {
k, err := parseKeyBase64(base64.StdEncoding, b64)
return (*PrivateKey)(k), err
}
func (k *PrivateKey) String() string { return base64.StdEncoding.EncodeToString(k[:]) }
func (k *PrivateKey) HexString() string { return hex.EncodeToString(k[:]) }
func (k *PrivateKey) Equal(k2 PrivateKey) bool { return subtle.ConstantTimeCompare(k[:], k2[:]) == 1 }
func (k *PrivateKey) IsZero() bool {
pk := Key(*k)
return pk.IsZero()
}
func (k *PrivateKey) clamp() {
k[0] &= 248
k[31] = (k[31] & 127) | 64
}
// Public computes the public key matching this curve25519 secret key.
func (k *PrivateKey) Public() Key {
pk := Key(*k)
if pk.IsZero() {
panic("Tried to generate emptyPrivateKey.Public()")
}
var p [KeySize]byte
curve25519.ScalarBaseMult(&p, (*[KeySize]byte)(k))
return (Key)(p)
}
func (k PrivateKey) MarshalText() ([]byte, error) {
buf := new(bytes.Buffer)
fmt.Fprintf(buf, `privkey:%x`, k[:])
return buf.Bytes(), nil
}
func (k *PrivateKey) UnmarshalText(b []byte) error {
s := string(b)
if !strings.HasPrefix(s, `privkey:`) {
return errors.New("wgcfg.PrivateKey: UnmarshalText not given a private-key string")
}
s = strings.TrimPrefix(s, `privkey:`)
key, err := ParseHexKey(s)
if err != nil {
return fmt.Errorf("wgcfg.PrivateKey: UnmarshalText: %v", err)
}
copy(k[:], key[:])
return nil
}
func (k PrivateKey) SharedSecret(pub Key) (ss [KeySize]byte) {
apk := (*[KeySize]byte)(&pub)
ask := (*[KeySize]byte)(&k)
curve25519.ScalarMult(&ss, ask, apk)
return ss
}
func parseKeyBase64(enc *base64.Encoding, s string) (*Key, error) {
k, err := enc.DecodeString(s)
if err != nil {
return nil, &ParseError{"Invalid key: " + err.Error(), s}
}
if len(k) != KeySize {
return nil, &ParseError{"Keys must decode to exactly 32 bytes", s}
}
var key Key
copy(key[:], k)
return &key, nil
}
func ParseSymmetricKey(b64 string) (SymmetricKey, error) {
k, err := parseKeyBase64(base64.StdEncoding, b64)
if err != nil {
return SymmetricKey{}, err
}
return SymmetricKey(*k), nil
}
func ParseSymmetricHexKey(s string) (SymmetricKey, error) {
b, err := hex.DecodeString(s)
if err != nil {
return SymmetricKey{}, &ParseError{"invalid symmetric hex key: " + err.Error(), s}
}
if len(b) != chacha20poly1305.KeySize {
return SymmetricKey{}, &ParseError{fmt.Sprintf("invalid symmetric hex key length: %d", len(b)), s}
}
var key SymmetricKey
copy(key[:], b)
return key, nil
}
// SymmetricKey is a 32-byte value used as a pre-shared key.
type SymmetricKey [chacha20poly1305.KeySize]byte
func (k SymmetricKey) Base64() string { return base64.StdEncoding.EncodeToString(k[:]) }
func (k SymmetricKey) String() string { return "sym:" + k.Base64()[:8] }
func (k SymmetricKey) HexString() string { return hex.EncodeToString(k[:]) }
func (k SymmetricKey) IsZero() bool { return k.Equal(SymmetricKey{}) }
func (k SymmetricKey) Equal(k2 SymmetricKey) bool { return subtle.ConstantTimeCompare(k[:], k2[:]) == 1 }
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