123 lines
5.1 KiB
Diff
123 lines
5.1 KiB
Diff
From e10a362f69191506e73bfa31778da45f4c5df482 Mon Sep 17 00:00:00 2001
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From: Daiki Ueno <dueno@redhat.com>
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Date: Mon, 12 Oct 2020 17:42:01 +0000
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Subject: [PATCH] Bug 1641480, TLS 1.3: tighten CCS handling in compatibility
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mode, r=mt
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This makes the server reject CCS when the client doesn't indicate the
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use of the middlebox compatibility mode with a non-empty
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ClientHello.legacy_session_id, or it sends multiple CCS in a row.
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Differential Revision: https://phabricator.services.mozilla.com/D79994
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--HG--
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extra : moz-landing-system : lando
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---
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gtests/ssl_gtest/ssl_tls13compat_unittest.cc | 33 ++++++++++++++++++++
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lib/ssl/ssl3con.c | 18 ++++-
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lib/ssl/sslimpl.h | 4 +
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3 files changed, 52 insertions(+), 3 deletions(-)
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diff --git a/nss/gtests/ssl_gtest/ssl_tls13compat_unittest.cc b/nss/gtests/ssl_gtest/ssl_tls13compat_unittest.cc
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index 6905ed0c0..dcede798c 100644
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--- a/nss/gtests/ssl_gtest/ssl_tls13compat_unittest.cc
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+++ b/nss/gtests/ssl_gtest/ssl_tls13compat_unittest.cc
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@@ -348,6 +348,39 @@ TEST_F(TlsConnectStreamTls13, ChangeCipherSpecBeforeClientHelloTwice) {
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client_->CheckErrorCode(SSL_ERROR_HANDSHAKE_UNEXPECTED_ALERT);
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}
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+// The server rejects a ChangeCipherSpec if the client advertises an
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+// empty session ID.
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+TEST_F(TlsConnectStreamTls13, ChangeCipherSpecAfterClientHelloEmptySid) {
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+ EnsureTlsSetup();
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+ ConfigureVersion(SSL_LIBRARY_VERSION_TLS_1_3);
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+
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+ StartConnect();
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+ client_->Handshake(); // Send ClientHello
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+ client_->SendDirect(DataBuffer(kCannedCcs, sizeof(kCannedCcs))); // Send CCS
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+
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+ server_->ExpectSendAlert(kTlsAlertUnexpectedMessage);
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+ server_->Handshake(); // Consume ClientHello and CCS
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+ server_->CheckErrorCode(SSL_ERROR_RX_MALFORMED_CHANGE_CIPHER);
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+}
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+
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+// The server rejects multiple ChangeCipherSpec even if the client
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+// indicates compatibility mode with non-empty session ID.
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+TEST_F(Tls13CompatTest, ChangeCipherSpecAfterClientHelloTwice) {
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+ EnsureTlsSetup();
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+ ConfigureVersion(SSL_LIBRARY_VERSION_TLS_1_3);
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+ EnableCompatMode();
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+
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+ StartConnect();
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+ client_->Handshake(); // Send ClientHello
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+ // Send CCS twice in a row
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+ client_->SendDirect(DataBuffer(kCannedCcs, sizeof(kCannedCcs)));
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+ client_->SendDirect(DataBuffer(kCannedCcs, sizeof(kCannedCcs)));
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+
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+ server_->ExpectSendAlert(kTlsAlertUnexpectedMessage);
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+ server_->Handshake(); // Consume ClientHello and CCS.
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+ server_->CheckErrorCode(SSL_ERROR_RX_MALFORMED_CHANGE_CIPHER);
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+}
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+
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// If we negotiate 1.2, we abort.
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TEST_F(TlsConnectStreamTls13, ChangeCipherSpecBeforeClientHello12) {
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EnsureTlsSetup();
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diff --git a/nss/lib/ssl/ssl3con.c b/nss/lib/ssl/ssl3con.c
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index 8be53d357..5f22872f8 100644
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--- a/nss/lib/ssl/ssl3con.c
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+++ b/nss/lib/ssl/ssl3con.c
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@@ -6645,7 +6645,11 @@ ssl_CheckServerSessionIdCorrectness(sslSocket *ss, SECItem *sidBytes)
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/* TLS 1.3: We sent a session ID. The server's should match. */
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if (!IS_DTLS(ss) && (sentRealSid || sentFakeSid)) {
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- return sidMatch;
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+ if (sidMatch) {
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+ ss->ssl3.hs.allowCcs = PR_TRUE;
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+ return PR_TRUE;
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+ }
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+ return PR_FALSE;
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}
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/* TLS 1.3 (no SID)/DTLS 1.3: The server shouldn't send a session ID. */
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@@ -8692,6 +8696,7 @@ ssl3_HandleClientHello(sslSocket *ss, PRUint8 *b, PRUint32 length)
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errCode = PORT_GetError();
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goto alert_loser;
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}
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+ ss->ssl3.hs.allowCcs = PR_TRUE;
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}
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/* TLS 1.3 requires that compression include only null. */
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@@ -13061,8 +13066,15 @@ ssl3_HandleRecord(sslSocket *ss, SSL3Ciphertext *cText)
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ss->ssl3.hs.ws != idle_handshake &&
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cText->buf->len == 1 &&
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cText->buf->buf[0] == change_cipher_spec_choice) {
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- /* Ignore the CCS. */
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- return SECSuccess;
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+ if (ss->ssl3.hs.allowCcs) {
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+ /* Ignore the first CCS. */
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+ ss->ssl3.hs.allowCcs = PR_FALSE;
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+ return SECSuccess;
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+ }
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+
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+ /* Compatibility mode is not negotiated. */
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+ alert = unexpected_message;
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+ PORT_SetError(SSL_ERROR_RX_MALFORMED_CHANGE_CIPHER);
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}
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if (IS_DTLS(ss) ||
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diff --git a/nss/lib/ssl/sslimpl.h b/nss/lib/ssl/sslimpl.h
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index b0e44a088..44c43a0e6 100644
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--- a/nss/lib/ssl/sslimpl.h
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+++ b/nss/lib/ssl/sslimpl.h
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@@ -710,6 +710,10 @@ typedef struct SSL3HandshakeStateStr {
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* or received. */
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PRBool receivedCcs; /* A server received ChangeCipherSpec
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* before the handshake started. */
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+ PRBool allowCcs; /* A server allows ChangeCipherSpec
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+ * as the middlebox compatibility mode
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+ * is explicitly indicarted by
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+ * legacy_session_id in TLS 1.3 ClientHello. */
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PRBool clientCertRequested; /* True if CertificateRequest received. */
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ssl3KEADef kea_def_mutable; /* Used to hold the writable kea_def
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* we use for TLS 1.3 */
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