use strlcpy & strlcat (#74) * refactor checkpubkeyperms() with safe BSD functions fix gcc8 warnings ``` svr-authpubkey.c: In function 'checkpubkeyperms': svr-authpubkey.c:427:2: warning: 'strncat' specified bound 5 equals source length [-Wstringop-overflow=] strncat(filename, "/.ssh", 5); /* strlen("/.ssh") == 5 */ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ svr-authpubkey.c:433:2: warning: 'strncat' specified bound 16 equals source length [-Wstringop-overflow=] strncat(filename, "/authorized_keys", 16); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ``` see https://www.sudo.ws/todd/papers/strlcpy.html * restore strlcpy in xstrdup see original https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/xmalloc.c?rev=1.16

#! /bin/sh
set -e

test "$1" = 'purge' || exit 0
if test -e /etc/dropbear; then
  rm -f /etc/dropbear/dropbear_rsa_host_key
  rm -f /etc/dropbear/dropbear_dss_host_key
  rmdir --ignore-fail-on-non-empty /etc/dropbear
fi
update-rc.d dropbear remove >/dev/null
rm -f /etc/default/dropbear
rm -rf /etc/dropbear/supervise /etc/dropbear/log/supervise