Xray-core/proxy/mtproto/auth.go

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2020-11-25 13:01:53 +02:00
package mtproto
import (
"context"
"crypto/rand"
"crypto/sha256"
"io"
"sync"
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"github.com/xtls/xray-core/common"
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)
const (
HeaderSize = 64
)
type SessionContext struct {
ConnectionType [4]byte
DataCenterID uint16
}
func DefaultSessionContext() SessionContext {
return SessionContext{
ConnectionType: [4]byte{0xef, 0xef, 0xef, 0xef},
DataCenterID: 0,
}
}
type contextKey int32
const (
sessionContextKey contextKey = iota
)
func ContextWithSessionContext(ctx context.Context, c SessionContext) context.Context {
return context.WithValue(ctx, sessionContextKey, c)
}
func SessionContextFromContext(ctx context.Context) SessionContext {
if c := ctx.Value(sessionContextKey); c != nil {
return c.(SessionContext)
}
return DefaultSessionContext()
}
type Authentication struct {
Header [HeaderSize]byte
DecodingKey [32]byte
EncodingKey [32]byte
DecodingNonce [16]byte
EncodingNonce [16]byte
}
func (a *Authentication) DataCenterID() uint16 {
x := ((int16(a.Header[61]) << 8) | int16(a.Header[60]))
if x < 0 {
x = -x
}
return uint16(x) - 1
}
func (a *Authentication) ConnectionType() [4]byte {
var x [4]byte
copy(x[:], a.Header[56:60])
return x
}
func (a *Authentication) ApplySecret(b []byte) {
a.DecodingKey = sha256.Sum256(append(a.DecodingKey[:], b...))
a.EncodingKey = sha256.Sum256(append(a.EncodingKey[:], b...))
}
func generateRandomBytes(random []byte, connType [4]byte) {
for {
common.Must2(rand.Read(random))
if random[0] == 0xef {
continue
}
val := (uint32(random[3]) << 24) | (uint32(random[2]) << 16) | (uint32(random[1]) << 8) | uint32(random[0])
if val == 0x44414548 || val == 0x54534f50 || val == 0x20544547 || val == 0x4954504f || val == 0xeeeeeeee {
continue
}
if (uint32(random[7])<<24)|(uint32(random[6])<<16)|(uint32(random[5])<<8)|uint32(random[4]) == 0x00000000 {
continue
}
copy(random[56:60], connType[:])
return
}
}
func NewAuthentication(sc SessionContext) *Authentication {
auth := getAuthenticationObject()
random := auth.Header[:]
generateRandomBytes(random, sc.ConnectionType)
copy(auth.EncodingKey[:], random[8:])
copy(auth.EncodingNonce[:], random[8+32:])
keyivInverse := Inverse(random[8 : 8+32+16])
copy(auth.DecodingKey[:], keyivInverse)
copy(auth.DecodingNonce[:], keyivInverse[32:])
return auth
}
func ReadAuthentication(reader io.Reader) (*Authentication, error) {
auth := getAuthenticationObject()
if _, err := io.ReadFull(reader, auth.Header[:]); err != nil {
putAuthenticationObject(auth)
return nil, err
}
copy(auth.DecodingKey[:], auth.Header[8:])
copy(auth.DecodingNonce[:], auth.Header[8+32:])
keyivInverse := Inverse(auth.Header[8 : 8+32+16])
copy(auth.EncodingKey[:], keyivInverse)
copy(auth.EncodingNonce[:], keyivInverse[32:])
return auth, nil
}
// Inverse returns a new byte array. It is a sequence of bytes when the input is read from end to beginning.Inverse
// Visible for testing only.
func Inverse(b []byte) []byte {
lenb := len(b)
b2 := make([]byte, lenb)
for i, v := range b {
b2[lenb-i-1] = v
}
return b2
}
var (
authPool = sync.Pool{
New: func() interface{} {
return new(Authentication)
},
}
)
func getAuthenticationObject() *Authentication {
return authPool.Get().(*Authentication)
}
func putAuthenticationObject(auth *Authentication) {
authPool.Put(auth)
}