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