From: dtucker@openbsd.org <dtucker@openbsd.org>
Date: Tue, 11 Mar 2025 07:42:08 +0000 (+0000)
Subject: upstream: Check if dbclient supports SHA1 before trying SHA1-based
X-Git-Url: http://git.ipfire.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=refs%2Fheads%2FV_9_9;p=thirdparty%2Fopenssh-portable.git

upstream: Check if dbclient supports SHA1 before trying SHA1-based

KEX.

Dropbear 2025.87 removed SHA1 support by default, which means
diffie-hellman-group14-sha1 is not available.  Unfortunately there isn't a
flag to query supported KEX, so instead check MACs and if it doesn't have
SHA1 methods, assuming SHA1 based KEXes are likewise not available.  Spotted
by anton@.

OpenBSD-Regress-ID: acfa8e26c001cb18b9fb81a27271c3b51288d304
---

diff --git a/regress/dropbear-kex.sh b/regress/dropbear-kex.sh
index d9f1b32c0..72717fbb7 100644
--- a/regress/dropbear-kex.sh
+++ b/regress/dropbear-kex.sh
@@ -1,4 +1,4 @@
-#	$OpenBSD: dropbear-kex.sh,v 1.3 2024/06/19 10:10:46 dtucker Exp $
+#	$OpenBSD: dropbear-kex.sh,v 1.4 2025/03/11 07:42:08 dtucker Exp $
 #	Placed in the Public Domain.
 
 tid="dropbear kex"
@@ -10,8 +10,14 @@ fi
 cp $OBJ/sshd_proxy $OBJ/sshd_proxy.bak
 
 kex="curve25519-sha256 curve25519-sha256@libssh.org"
-if $SSH -Q kex | grep 'diffie-hellman-group14-sha1'; then
-	kex="$kex diffie-hellman-group14-sha256 diffie-hellman-group14-sha1"
+if $SSH -Q kex | grep 'diffie-hellman-group14-sha256' >/dev/null; then
+	kex="$kex diffie-hellman-group14-sha256"
+fi
+# There's no flag to query KEX, so if MACs does not contain SHA1, assume
+# there's also SHA1-based KEX methods either.
+if $SSH -Q kex | grep 'diffie-hellman-group14-sha1' >/dev/null && \
+    $DBCLIENT -m help hst 2>&1 | grep -- '-sha1' >/dev/null ; then
+	kex="$kex diffie-hellman-group14-sha1"
 fi
 
 for k in $kex; do
@@ -19,8 +25,9 @@ for k in $kex; do
 	rm -f ${COPY}
 	# dbclient doesn't have switch for kex, so force in server
 	(cat $OBJ/sshd_proxy.bak; echo "KexAlgorithms $k") >$OBJ/sshd_proxy
-	env HOME=$OBJ dbclient -y -i $OBJ/.dropbear/id_ed25519 2>$OBJ/dbclient.log \
-	    -J "$OBJ/ssh_proxy.sh" somehost cat ${DATA} > ${COPY}
+	env HOME=$OBJ \
+	    ${DBCLIENT} -y -i $OBJ/.dropbear/id_ed25519 2>$OBJ/dbclient.log \
+	   -J "$OBJ/ssh_proxy.sh" somehost cat ${DATA} > ${COPY}
 	if [ $? -ne 0 ]; then
 		fail "ssh cat $DATA failed"
 	fi