1 files changed, 44 insertions, 1 deletions

diff --git a/src/lib/libssl/tls13_lib.c b/src/lib/libssl/tls13_lib.c
index 044a0c5634..199f43ca16 100644
--- a/src/lib/libssl/tls13_lib.c
+++ b/src/lib/libssl/tls13_lib.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: tls13_lib.c,v 1.35 2020/04/21 16:55:17 jsing Exp $ */
+/*      $OpenBSD: tls13_lib.c,v 1.36 2020/04/28 20:30:41 jsing Exp $ */
 /*
  * Copyright (c) 2018, 2019 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2019 Bob Beck <beck@openbsd.org>
@@ -369,3 +369,46 @@ tls13_cert_add(CBB *cbb, X509 *cert)
 
         return 1;
 }
+
+int
+tls13_synthetic_handshake_message(struct tls13_ctx *ctx)
+{
+        struct tls13_handshake_msg *hm = NULL;
+        unsigned char buf[EVP_MAX_MD_SIZE];
+        size_t hash_len;
+        CBB cbb;
+        CBS cbs;
+        SSL *s = ctx->ssl;
+        int ret = 0;
+
+        /*
+         * Replace ClientHello with synthetic handshake message - see
+         * RFC 8446 section 4.4.1.
+         */
+        if (!tls1_transcript_hash_init(s))
+                goto err;
+        if (!tls1_transcript_hash_value(s, buf, sizeof(buf), &hash_len))
+                goto err;
+
+        if ((hm = tls13_handshake_msg_new()) == NULL)
+                goto err;
+        if (!tls13_handshake_msg_start(hm, &cbb, TLS13_MT_MESSAGE_HASH))
+                goto err;
+        if (!CBB_add_bytes(&cbb, buf, hash_len))
+                goto err;
+        if (!tls13_handshake_msg_finish(hm))
+                goto err;
+
+        tls13_handshake_msg_data(hm, &cbs);
+
+        tls1_transcript_reset(ctx->ssl);
+        if (!tls1_transcript_record(ctx->ssl, CBS_data(&cbs), CBS_len(&cbs)))
+                goto err;
+
+        ret = 1;
+
+ err:
+        tls13_handshake_msg_free(hm);
+
+        return ret;
+}