Add a middlebox_compat flag and condition session ID randomisation on it.

ok tb@

3 files changed, 7 insertions, 4 deletions

diff --git a/src/lib/libssl/tls13_client.c b/src/lib/libssl/tls13_client.c
index aab83dcc69..d5ac6ba5e0 100644
--- a/src/lib/libssl/tls13_client.c
+++ b/src/lib/libssl/tls13_client.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls13_client.c,v 1.55 2020/05/09 15:05:50 beck Exp $ */
+/* $OpenBSD: tls13_client.c,v 1.56 2020/05/09 15:30:21 jsing Exp $ */
 /*
  * Copyright (c) 2018, 2019 Joel Sing <jsing@openbsd.org>
  *
@@ -61,7 +61,7 @@ tls13_client_init(struct tls13_ctx *ctx)
          * legacy session identifier triggers compatibility mode (see RFC 8446
          * Appendix D.4). In the pre-TLSv1.3 case a zero length value is used.
          */
-        if (ctx->hs->max_version >= TLS1_3_VERSION) {
+        if (ctx->middlebox_compat && ctx->hs->max_version >= TLS1_3_VERSION) {
                 arc4random_buf(ctx->hs->legacy_session_id,
                     sizeof(ctx->hs->legacy_session_id));
                 ctx->hs->legacy_session_id_len =
diff --git a/src/lib/libssl/tls13_internal.h b/src/lib/libssl/tls13_internal.h
index b699b20501..f15d11551a 100644
--- a/src/lib/libssl/tls13_internal.h
+++ b/src/lib/libssl/tls13_internal.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls13_internal.h,v 1.68 2020/05/09 15:05:50 beck Exp $ */
+/* $OpenBSD: tls13_internal.h,v 1.69 2020/05/09 15:30:21 jsing Exp $ */
 /*
  * Copyright (c) 2018 Bob Beck <beck@openbsd.org>
  * Copyright (c) 2018 Theo Buehler <tb@openbsd.org>
@@ -218,6 +218,7 @@ struct tls13_ctx {
         uint8_t mode;
         struct tls13_handshake_stage handshake_stage;
         int handshake_completed;
+        int middlebox_compat;
 
         int close_notify_sent;
         int close_notify_recv;
diff --git a/src/lib/libssl/tls13_lib.c b/src/lib/libssl/tls13_lib.c
index 37f300ae43..3825707d5c 100644
--- a/src/lib/libssl/tls13_lib.c
+++ b/src/lib/libssl/tls13_lib.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: tls13_lib.c,v 1.37 2020/05/09 15:05:50 beck Exp $ */
+/*      $OpenBSD: tls13_lib.c,v 1.38 2020/05/09 15:30:21 jsing Exp $ */
 /*
  * Copyright (c) 2018, 2019 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2019 Bob Beck <beck@openbsd.org>
@@ -351,6 +351,8 @@ tls13_ctx_new(int mode)
         ctx->handshake_message_recv_cb = tls13_legacy_handshake_message_recv_cb;
         ctx->ocsp_status_recv_cb = tls13_legacy_ocsp_status_recv_cb;
 
+        ctx->middlebox_compat = 1;
+
         return ctx;
 
  err: