PORTREVISION=	1

diff --git a/gtests/ssl_gtest/ssl_tls13compat_unittest.cc b/gtests/ssl_gtest/ssl_tls13compat_unittest.cc

--- gtests/ssl_gtest/ssl_tls13compat_unittest.cc

+++ gtests/ssl_gtest/ssl_tls13compat_unittest.cc

@@ -343,29 +343,28 @@ TEST_F(TlsConnectStreamTls13, ChangeCiph

   // Client sends CCS before starting the handshake.

   client_->SendDirect(DataBuffer(kCannedCcs, sizeof(kCannedCcs)));

   client_->SendDirect(DataBuffer(kCannedCcs, sizeof(kCannedCcs)));

   ConnectExpectAlert(server_, kTlsAlertUnexpectedMessage);

   server_->CheckErrorCode(SSL_ERROR_RX_UNEXPECTED_CHANGE_CIPHER);

   client_->CheckErrorCode(SSL_ERROR_HANDSHAKE_UNEXPECTED_ALERT);

 }

-// The server rejects a ChangeCipherSpec if the client advertises an

-// empty session ID.

+// The server accepts a ChangeCipherSpec even if the client advertises

+// an empty session ID.

 TEST_F(TlsConnectStreamTls13, ChangeCipherSpecAfterClientHelloEmptySid) {

   EnsureTlsSetup();

   ConfigureVersion(SSL_LIBRARY_VERSION_TLS_1_3);

   StartConnect();

   client_->Handshake();  // Send ClientHello

   client_->SendDirect(DataBuffer(kCannedCcs, sizeof(kCannedCcs)));  // Send CCS

-  server_->ExpectSendAlert(kTlsAlertUnexpectedMessage);

-  server_->Handshake();  // Consume ClientHello and CCS

-  server_->CheckErrorCode(SSL_ERROR_RX_MALFORMED_CHANGE_CIPHER);

+  Handshake();

+  CheckConnected();

 }

 // The server rejects multiple ChangeCipherSpec even if the client

 // indicates compatibility mode with non-empty session ID.

 TEST_F(Tls13CompatTest, ChangeCipherSpecAfterClientHelloTwice) {

   EnsureTlsSetup();

   ConfigureVersion(SSL_LIBRARY_VERSION_TLS_1_3);

   EnableCompatMode();

@@ -376,36 +375,37 @@ TEST_F(Tls13CompatTest, ChangeCipherSpec

   client_->SendDirect(DataBuffer(kCannedCcs, sizeof(kCannedCcs)));

   client_->SendDirect(DataBuffer(kCannedCcs, sizeof(kCannedCcs)));

   server_->ExpectSendAlert(kTlsAlertUnexpectedMessage);

   server_->Handshake();  // Consume ClientHello and CCS.

   server_->CheckErrorCode(SSL_ERROR_RX_MALFORMED_CHANGE_CIPHER);

 }

-// The client rejects a ChangeCipherSpec if it advertises an empty

+// The client accepts a ChangeCipherSpec even if it advertises an empty

 // session ID.

 TEST_F(TlsConnectStreamTls13, ChangeCipherSpecAfterServerHelloEmptySid) {

   EnsureTlsSetup();

   ConfigureVersion(SSL_LIBRARY_VERSION_TLS_1_3);

   // To replace Finished with a CCS below

   auto filter = MakeTlsFilter<TlsHandshakeDropper>(server_);

   filter->SetHandshakeTypes({kTlsHandshakeFinished});

   filter->EnableDecryption();

   StartConnect();

   client_->Handshake();  // Send ClientHello

   server_->Handshake();  // Consume ClientHello, and

                          // send ServerHello..CertificateVerify

   // Send CCS

   server_->SendDirect(DataBuffer(kCannedCcs, sizeof(kCannedCcs)));

-  client_->ExpectSendAlert(kTlsAlertUnexpectedMessage);

-  client_->Handshake();  // Consume ClientHello and CCS

-  client_->CheckErrorCode(SSL_ERROR_RX_MALFORMED_CHANGE_CIPHER);

+

+  // No alert is sent from the client. As Finished is dropped, we

+  // can't use Handshake() and CheckConnected().

+  client_->Handshake();

 }

 // The client rejects multiple ChangeCipherSpec in a row even if the

 // client indicates compatibility mode with non-empty session ID.

 TEST_F(Tls13CompatTest, ChangeCipherSpecAfterServerHelloTwice) {

   EnsureTlsSetup();

   ConfigureVersion(SSL_LIBRARY_VERSION_TLS_1_3);

   EnableCompatMode();

diff --git a/lib/ssl/ssl3con.c b/lib/ssl/ssl3con.c

--- lib/ssl/ssl3con.c

+++ lib/ssl/ssl3con.c

@@ -6640,21 +6640,17 @@ ssl_CheckServerSessionIdCorrectness(sslS

         if (sentFakeSid) {

             return !sidMatch;

         }

         return PR_TRUE;

     }

     /* TLS 1.3: We sent a session ID.  The server's should match. */

     if (!IS_DTLS(ss) && (sentRealSid || sentFakeSid)) {

-        if (sidMatch) {

-            ss->ssl3.hs.allowCcs = PR_TRUE;

-            return PR_TRUE;

-        }

-        return PR_FALSE;

+        return sidMatch;

     }

     /* TLS 1.3 (no SID)/DTLS 1.3: The server shouldn't send a session ID. */

     return sidBytes->len == 0;

 }

 static SECStatus

 ssl_CheckServerRandom(sslSocket *ss)

@@ -8691,17 +8687,16 @@ ssl3_HandleClientHello(sslSocket *ss, PR

         if (sidBytes.len > 0 && !IS_DTLS(ss)) {

             SECITEM_FreeItem(&ss->ssl3.hs.fakeSid, PR_FALSE);

             rv = SECITEM_CopyItem(NULL, &ss->ssl3.hs.fakeSid, &sidBytes);

             if (rv != SECSuccess) {

                 desc = internal_error;

                 errCode = PORT_GetError();

                 goto alert_loser;

             }

-            ss->ssl3.hs.allowCcs = PR_TRUE;

         }

         /* TLS 1.3 requires that compression include only null. */

         if (comps.len != 1 || comps.data[0] != ssl_compression_null) {

             goto alert_loser;

         }

         /* If there is a cookie, then this is a second ClientHello (TLS 1.3). */

@@ -13061,25 +13056,24 @@ ssl3_HandleRecord(sslSocket *ss, SSL3Cip

          * will fail if the server fails to negotiate compatibility mode in a

          * 0-RTT session that is resumed from a session that did negotiate it.

          * We don't care about that corner case right now. */

         if (ss->version >= SSL_LIBRARY_VERSION_TLS_1_3 &&

             cText->hdr[0] == ssl_ct_change_cipher_spec &&

             ss->ssl3.hs.ws != idle_handshake &&

             cText->buf->len == 1 &&

             cText->buf->buf[0] == change_cipher_spec_choice) {

-            if (ss->ssl3.hs.allowCcs) {

-                /* Ignore the first CCS. */

-                ss->ssl3.hs.allowCcs = PR_FALSE;

+            if (!ss->ssl3.hs.rejectCcs) {

+                /* Allow only the first CCS. */

+                ss->ssl3.hs.rejectCcs = PR_TRUE;

                 return SECSuccess;

-            }

-

-            /* Compatibility mode is not negotiated. */

-            alert = unexpected_message;

-            PORT_SetError(SSL_ERROR_RX_MALFORMED_CHANGE_CIPHER);

+            } else {

+                alert = unexpected_message;

+                PORT_SetError(SSL_ERROR_RX_MALFORMED_CHANGE_CIPHER);

+            }

         }

         if ((IS_DTLS(ss) && !dtls13_AeadLimitReached(spec)) ||

             (!IS_DTLS(ss) && ss->sec.isServer &&

              ss->ssl3.hs.zeroRttIgnore == ssl_0rtt_ignore_trial)) {

             /* Silently drop the packet unless we sent a fatal alert. */

             if (ss->ssl3.fatalAlertSent) {

                 return SECFailure;

diff --git a/lib/ssl/sslimpl.h b/lib/ssl/sslimpl.h

--- lib/ssl/sslimpl.h

+++ lib/ssl/sslimpl.h

@@ -705,20 +705,17 @@ typedef struct SSL3HandshakeStateStr {

     sslZeroRttIgnore zeroRttIgnore;       /* Are we ignoring 0-RTT? */

     ssl3CipherSuite zeroRttSuite;         /* The cipher suite we used for 0-RTT. */

     PRCList bufferedEarlyData;            /* Buffered TLS 1.3 early data

                                            * on server.*/

     PRBool helloRetry;                    /* True if HelloRetryRequest has been sent

                                            * or received. */

     PRBool receivedCcs;                   /* A server received ChangeCipherSpec

                                            * before the handshake started. */

-    PRBool allowCcs;                      /* A server allows ChangeCipherSpec

-                                           * as the middlebox compatibility mode

-                                           * is explicitly indicarted by

-                                           * legacy_session_id in TLS 1.3 ClientHello. */

+    PRBool rejectCcs;                     /* Excessive ChangeCipherSpecs are rejected. */

     PRBool clientCertRequested;           /* True if CertificateRequest received. */

     PRBool endOfFlight;                   /* Processed a full flight (DTLS 1.3). */

     ssl3KEADef kea_def_mutable;           /* Used to hold the writable kea_def

                                            * we use for TLS 1.3 */

     PRUint16 ticketNonce;                 /* A counter we use for tickets. */

     SECItem fakeSid;                      /* ... (server) the SID the client used. */

     /* rttEstimate is used to guess the round trip time between server and client.