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fix: sync lenient DC-ID validation for key exchange

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This commit is contained in:
onysd 2026-07-24 17:36:13 +03:00
parent 0e2fcdf9c8
commit e7eb07b9eb
5 changed files with 82 additions and 6 deletions
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26
internal/mtprotoedge/exchange_compat.go
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@ -27,9 +27,12 @@ import (
//
// DrKLO Android marks media temporary auth-key exchange with a negative DC in
// p_q_inner_data_temp_dc (for example DC 2 -> -2). gotd v0.158.0 validates this
// field by exact equality and rejects that legitimate media-temp path. Keep the
// permanent-key check strict, but allow temp-key DC values whose absolute value
// matches this server DC.
// field by exact equality and rejects that legitimate media-temp path. The
// temp-key DC check accepts any value whose absolute value matches this
// server DC. The permanent-key check is lenient by default too (see
// Options.StrictDC doc) — self-hosted single-server deployments commonly
// have clients that alias dc_id 1..5 to the one backend, so a client-chosen
// dc_id that isn't our configured DC is expected, not an error.
func (s *Server) runServerExchange(ctx context.Context, conn transport.Conn) (exchange.ServerExchangeResult, error) {
ex := serverExchangeCompat{
conn: conn,
@ -38,6 +41,7 @@ func (s *Server) runServerExchange(ctx context.Context, conn transport.Conn) (ex
timeout: exchange.DefaultTimeout,
key: s.key,
dc: s.dc,
strictDC: s.strictDC,
log: s.log.Named("exchange"),
rng: compatServerRNG{rand: s.rand},
commitKey: s.commitExchangeAuthKey,
@ -65,6 +69,7 @@ type serverExchangeCompat struct {
timeout time.Duration
key exchange.PrivateKey
dc int
strictDC bool
log *zap.Logger
rng compatServerRNG
commitKey func(context.Context, exchange.ServerExchangeResult, int) error
@ -345,10 +350,23 @@ func (s serverExchangeCompat) validatePQInnerDataDC(d mt.PQInnerDataClass) error
switch innerDataDC := d.(type) {
case *mt.PQInnerDataDC:
if innerDataDC.DC != s.dc {
if !s.strictDC {
// Lenient by default (Options.StrictDC doc has the full
// rationale): telesrv is a single physical backend, and
// self-hosted client forks commonly alias dc_id 1..5 to this
// one server, so a client-chosen dc_id that isn't our
// configured DC is expected, not an error. dc_id plays no
// role in key derivation, so accepting it doesn't weaken the
// exchange.
s.log.Debug("Accepted permanent auth key DC mismatch (lenient mode)",
zap.Int("server_dc", s.dc),
zap.Int("client_dc", innerDataDC.DC))
return nil
}
return wrongDCError(s.dc, innerDataDC.DC)
}
case *mt.PQInnerDataTempDC:
if !sameDCByAbs(innerDataDC.DC, s.dc) {
if !sameDCByAbs(innerDataDC.DC, s.dc) && s.strictDC {
return wrongDCError(s.dc, innerDataDC.DC)
}
if innerDataDC.DC < 0 {