upstream: avoid possible NULL deref if

ssh_packet_check_rekey_blocklimit() called before the encrypted transport is
brought up.

OpenBSD-Commit-ID: fb998ccbe59865e33a8ab6a6577f254d39bdc72f

Author: djmdjm

packet.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.c,v 1.329 2025/12/30 00:35:37 djm Exp $ */
+/* $OpenBSD: packet.c,v 1.330 2025/12/30 04:23:53 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1096,6 +1096,9 @@ ssh_packet_check_rekey_blocklimit(struct ssh *ssh, u_int packet_len, int hard)
 	    state->p_read.packets > MAX_PACKETS)
 		return 1;
 
+	if (state->newkeys == NULL)
+		return 0;
+
 	/* Rekey after (cipher-specific) maximum blocks */
 	out_blocks = ROUNDUP(packet_len,
 	    state->newkeys[MODE_OUT]->enc.block_size);