[openssh-commits] [openssh] branch V_9_9 updated: upstream: Check if dbclient supports SHA1 before trying SHA1-based

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dtucker pushed a commit to branch V_9_9
in repository openssh.

The following commit(s) were added to refs/heads/V_9_9 by this push:
     new 3eeda15e upstream: Check if dbclient supports SHA1 before trying SHA1-based
3eeda15e is described below

commit 3eeda15eb9d3b9f2fd762ba3493ba88abe6bbcd9
Author: dtucker at openbsd.org <dtucker at openbsd.org>
AuthorDate: Tue Mar 11 07:42:08 2025 +0000

    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 at .
    
    OpenBSD-Regress-ID: acfa8e26c001cb18b9fb81a27271c3b51288d304
---
 regress/dropbear-kex.sh | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/regress/dropbear-kex.sh b/regress/dropbear-kex.sh
index d9f1b32c..72717fbb 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 at 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

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