upstream: Factor out PuTTY setup.

Factor out PuTTY and call only when needed.

This allows us to avoid PuTTY key setup when it's not needed, which
speeds up the overall test run by a couple of percent.

OpenBSD-Regress-ID: c25eaccc3c91bc874400f7c85ce40e9032358c1c

regress/test-exec.sh

@@ -1,4 +1,4 @@
-#	$OpenBSD: test-exec.sh,v 1.105 2023/10/31 04:15:40 dtucker Exp $
+#	$OpenBSD: test-exec.sh,v 1.106 2024/02/09 08:47:42 dtucker Exp $
 #	Placed in the Public Domain.
 
 #SUDO=sudo
@@ -762,6 +762,11 @@ case "$SCRIPT" in
 esac
 
 if test "$REGRESS_INTEROP_PUTTY" = "yes" ; then
+    puttysetup() {
+	if test "x$REGRESS_INTEROP_PUTTY" != "xyes" ; then
+		skip "putty interop tests not enabled"
+	fi
+
 	mkdir -p ${OBJ}/.putty
 
 	# Add a PuTTY key to authorized_keys
@@ -794,8 +799,24 @@ if test "$REGRESS_INTEROP_PUTTY" = "yes" ; then
 	echo "ProxyTelnetCommand=${OBJ}/sshd-log-wrapper.sh -i -f $OBJ/sshd_proxy" >> ${OBJ}/.putty/sessions/localhost_proxy
 	echo "ProxyLocalhost=1" >> ${OBJ}/.putty/sessions/localhost_proxy
 
+	PUTTYVER="`${PLINK} --version | awk '/plink: Release/{print $3}'`"
+	PUTTYMINORVER="`echo ${PUTTYVER} | cut -f2 -d.`"
+	verbose "plink version ${PUTTYVER} minor ${PUTTYMINORVER}"
+
+	# Re-enable ssh-rsa on older PuTTY versions since they don't do newer
+	# key types.
+	if [ "$PUTTYMINORVER" -lt "76" ]; then
+		echo "HostKeyAlgorithms +ssh-rsa" >> ${OBJ}/sshd_proxy
+		echo "PubkeyAcceptedKeyTypes +ssh-rsa" >> ${OBJ}/sshd_proxy
+	fi
+
+	if [ "$PUTTYMINORVER" -le "64" ]; then
+		echo "KexAlgorithms +diffie-hellman-group14-sha1" \
+		    >>${OBJ}/sshd_proxy
+	fi
 	PUTTYDIR=${OBJ}/.putty
 	export PUTTYDIR
+    }
 fi
 
 REGRESS_INTEROP_DROPBEAR=no