upstream: Record session ID, host key and sig at intital KEX

These will be used later for agent session ID / hostkey binding

ok markus@

OpenBSD-Commit-ID: a9af29e33772b18e3e867c6fa8ab35e1694a81fe

1 files changed, 21 insertions, 3 deletions

diff --git a/kexgexc.c b/kexgexc.c
index 4a2e741d..e99e0cf2 100644
--- a/kexgexc.c
+++ b/kexgexc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexgexc.c,v 1.37 2021/01/31 22:55:29 djm Exp $ */
+/* $OpenBSD: kexgexc.c,v 1.38 2021/12/19 22:08:06 djm Exp $ */
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
@@ -206,8 +206,26 @@ input_kex_dh_gex_reply(int type, u_int32_t seq, struct ssh *ssh)
 	    hashlen, kex->hostkey_alg, ssh->compat, NULL)) != 0)
 		goto out;
 
-	if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
-		r = kex_send_newkeys(ssh);
+	if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) != 0 ||
+	    (r = kex_send_newkeys(ssh)) != 0)
+		goto out;
+
+	/* save initial signature and hostkey */
+	if ((kex->flags & KEX_INITIAL) != 0) {
+		if (kex->initial_hostkey != NULL || kex->initial_sig != NULL) {
+			r = SSH_ERR_INTERNAL_ERROR;
+			goto out;
+		}
+		if ((kex->initial_sig = sshbuf_new()) == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
+		if ((r = sshbuf_put(kex->initial_sig, signature, slen)) != 0)
+			goto out;
+		kex->initial_hostkey = server_host_key;
+		server_host_key = NULL;
+	}
+	/* success */
  out:
 	explicit_bzero(hash, sizeof(hash));
 	DH_free(kex->dh);