upstream commit

Back out rev 1.28 "Check min and max sizes sent by the
client" change. It caused "key_verify failed for server_host_key" in clients
that send a DH-GEX min value less that DH_GRP_MIN, eg old OpenSSH and PuTTY.
ok djm@

Upstream-ID: 452979d3ca5c1e9dff063287ea0a5314dd091f65

1 files changed, 9 insertions, 9 deletions

diff --git a/kexgexs.c b/kexgexs.c
index f3c7de54b..f4400dcbe 100644
--- a/kexgexs.c
+++ b/kexgexs.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexgexs.c,v 1.28 2016/06/01 04:19:49 dtucker Exp $ */
+/* $OpenBSD: kexgexs.c,v 1.29 2016/06/08 02:13:01 dtucker Exp $ */
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
@@ -83,21 +83,21 @@ input_kex_dh_gex_request(int type, u_int32_t seq, void *ctxt)
         kex->nbits = nbits;
         kex->min = min;
         kex->max = max;
+        min = MAX(DH_GRP_MIN, min);
+        max = MIN(DH_GRP_MAX, max);
+        nbits = MAX(DH_GRP_MIN, nbits);
+        nbits = MIN(DH_GRP_MAX, nbits);
+
         if (kex->max < kex->min || kex->nbits < kex->min ||
-            kex->max < kex->nbits || kex->max < DH_GRP_MIN ||
-            kex->min > DH_GRP_MAX) {
+            kex->max < kex->nbits || kex->max < DH_GRP_MIN) {
                 r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
                 goto out;
         }
-        kex->min = MAX(DH_GRP_MIN, kex->min);
-        kex->max = MIN(DH_GRP_MAX, kex->max);
-        kex->nbits = MAX(DH_GRP_MIN, kex->nbits);
-        kex->nbits = MIN(DH_GRP_MAX, kex->nbits);
 
         /* Contact privileged parent */
-        kex->dh = PRIVSEP(choose_dh(kex->min, kex->nbits, kex->max));
+        kex->dh = PRIVSEP(choose_dh(min, nbits, max));
         if (kex->dh == NULL) {
-                sshpkt_disconnect(ssh, "no matching DH group found");
+                sshpkt_disconnect(ssh, "no matching DH grp found");
                 r = SSH_ERR_ALLOC_FAIL;
                 goto out;
         }