Add a test for an empty NextProto message

It is valid according to the spec for a NextProto message to have no
protocols listed in it. The OpenSSL implementation however does not allow
us to create such a message. In order to check that we work as expected
when communicating with a client that does generate such messages we have
to use a TLSProxy test.

Follow on from CVE-2024-5535

Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24718)

3 files changed, 64 insertions, 0 deletions

diff --git a/util/perl/TLSProxy/Message.pm b/util/perl/TLSProxy/Message.pm
index 2c1bdb3837..eb350de431 100644
--- a/util/perl/TLSProxy/Message.pm
+++ b/util/perl/TLSProxy/Message.pm
@@ -379,6 +379,15 @@ sub create_message
             [@message_frag_lens]
         );
         $message->parse();
+    }  elsif ($mt == MT_NEXT_PROTO) {
+        $message = TLSProxy::NextProto->new(
+            $server,
+            $data,
+            [@message_rec_list],
+            $startoffset,
+            [@message_frag_lens]
+        );
+        $message->parse();
     } else {
         #Unknown message type
         $message = TLSProxy::Message->new(
diff --git a/util/perl/TLSProxy/NextProto.pm b/util/perl/TLSProxy/NextProto.pm
new file mode 100644
index 0000000000..0e18347546
--- /dev/null
+++ b/util/perl/TLSProxy/NextProto.pm
@@ -0,0 +1,54 @@
+# Copyright 2024 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the Apache License 2.0 (the "License").  You may not use
+# this file except in compliance with the License.  You can obtain a copy
+# in the file LICENSE in the source distribution or at
+# https://www.openssl.org/source/license.html
+
+use strict;
+
+package TLSProxy::NextProto;
+
+use vars '@ISA';
+push @ISA, 'TLSProxy::Message';
+
+sub new
+{
+    my $class = shift;
+    my ($server,
+        $data,
+        $records,
+        $startoffset,
+        $message_frag_lens) = @_;
+
+    my $self = $class->SUPER::new(
+        $server,
+        TLSProxy::Message::MT_NEXT_PROTO,
+        $data,
+        $records,
+        $startoffset,
+        $message_frag_lens);
+
+    return $self;
+}
+
+sub parse
+{
+    # We don't support parsing at the moment
+}
+
+# This is supposed to reconstruct the on-the-wire message data following changes.
+# For now though since we don't support parsing we just create an empty NextProto
+# message - this capability is used in test_npn
+sub set_message_contents
+{
+    my $self = shift;
+    my $data;
+
+    $data = pack("C32", 0x00, 0x1e, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                 0x00, 0x00, 0x00);
+    $self->data($data);
+}
+1;
diff --git a/util/perl/TLSProxy/Proxy.pm b/util/perl/TLSProxy/Proxy.pm
index 3de10eccb9..b707722b6b 100644
--- a/util/perl/TLSProxy/Proxy.pm
+++ b/util/perl/TLSProxy/Proxy.pm
@@ -23,6 +23,7 @@ use TLSProxy::CertificateRequest;
 use TLSProxy::CertificateVerify;
 use TLSProxy::ServerKeyExchange;
 use TLSProxy::NewSessionTicket;
+use TLSProxy::NextProto;
 
 my $have_IPv6;
 my $IP_factory;