Ensure the default length calculation includes the content type byte

TLSv1.3 includes an extra byte after the payload for the content type.
We should incorporate that in the calculation of the default buffer length.

Fixes #23015

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/23021)

diff --git a/ssl/record/methods/tls_common.c b/ssl/record/methods/tls_common.c
index 423777c18dd40fa13671c6718958a352783c38fb..7da423e24300e62a2b2931f5e0a4d0324a856f37 100644 (file)
--- a/ssl/record/methods/tls_common.c
+++ b/ssl/record/methods/tls_common.c
@@ -147,6 +147,7 @@ int tls_setup_write_buffer(OSSL_RECORD_LAYER *rl, size_t numwpipes,
     TLS_BUFFER *wb;
     size_t currpipe;
     size_t defltlen = 0;
+    size_t contenttypelen = 0;
 
     if (firstlen == 0 || (numwpipes > 1 && nextlen == 0)) {
         if (rl->isdtls)
@@ -154,21 +155,26 @@ int tls_setup_write_buffer(OSSL_RECORD_LAYER *rl, size_t numwpipes,
         else
             headerlen = SSL3_RT_HEADER_LENGTH;
 
+        /* TLSv1.3 adds an extra content type byte after payload data */
+        if (rl->version == TLS1_3_VERSION)
+            contenttypelen = 1;
+
 #if defined(SSL3_ALIGN_PAYLOAD) && SSL3_ALIGN_PAYLOAD != 0
         align = SSL3_ALIGN_PAYLOAD - 1;
 #endif
 
-        defltlen = rl->max_frag_len + SSL3_RT_SEND_MAX_ENCRYPTED_OVERHEAD
-                   + headerlen + align + rl->eivlen;
+        defltlen = align + headerlen + rl->eivlen + rl->max_frag_len
+                   + contenttypelen + SSL3_RT_SEND_MAX_ENCRYPTED_OVERHEAD;
 #ifndef OPENSSL_NO_COMP
         if (tls_allow_compression(rl))
             defltlen += SSL3_RT_MAX_COMPRESSED_OVERHEAD;
 #endif
         /*
          * We don't need to add eivlen here since empty fragments only occur
-         * when we don't have an explicit IV
+         * when we don't have an explicit IV. The contenttype byte will also
+         * always be 0 in these protocol versions
          */
-        if (!(rl->options & SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS))
+        if ((rl->options & SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS) == 0)
             defltlen += headerlen + align + SSL3_RT_SEND_MAX_ENCRYPTED_OVERHEAD;
     }