[PATCH] wg-tools: Fix too strict file permissions on resolv.conf

Florian Bausch fbausch at ernw.de
Wed Feb 15 12:54:05 UTC 2023


I hardened my system by setting a strict umask of 077 in
/etc/login.defs. However, this breaks DNS as soon as wg-quick is used to
bring up a WireGuard tunnel. This is, because the strict umask value
will be applied to /etc/resolv.conf (at least if the DNS hatchet is
used) and therefore, unprivileged processes are not able to read

While the behavior can be worked around by setting umask in other
places, the fix below would prevent this behavior to occur. The umask
022 is applied before creating the new /etc/resolv.conf in the DNS hatchet.

Kind regards

Signed-off-by: Florian Bausch <fbausch at ernw.de>
  contrib/dns-hatchet/hatchet.bash | 1 +
  1 file changed, 1 insertion(+)

diff --git a/contrib/dns-hatchet/hatchet.bash 
index bc4d090..807a14a 100644
--- a/contrib/dns-hatchet/hatchet.bash
+++ b/contrib/dns-hatchet/hatchet.bash
@@ -20,6 +20,7 @@ set_dns() {
  		[[ ${#DNS_SEARCH[@]} -eq 0 ]] || printf 'search %s\n' "${DNS_SEARCH[*]}"
  		} | unshare -m --propagation shared bash -c "$(cat <<-_EOF
  			set -e
+			umask 022
  			context="\$(stat -c %C /etc/resolv.conf 2>/dev/null)" || unset context
  			mount --make-private /dev/shm
  			mount -t tmpfs none /dev/shm
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