130 lines
4.3 KiB
Bash
Executable file
130 lines
4.3 KiB
Bash
Executable file
#!/bin/sh -eu
|
|
# Copyright (c) The Exim Maintainers 2022
|
|
# SPDX-License-Identifier: GPL-2.0-or-later
|
|
#
|
|
# Short version of this script:
|
|
# curl -f -o /var/cache/exim/opendmarc.tlds https://publicsuffix.org/list/public_suffix_list.dat
|
|
# but run as Exim runtime user, writing to a place it can write to, and with
|
|
# sanity checks and atomic replacement.
|
|
#
|
|
# For now, we deliberately leave the invalid file around for analysis
|
|
# with .<pid> suffix.
|
|
#
|
|
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~8< cut here >8~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
#
|
|
# Create a cron-job as the Exim run-time user to invoke this daily, with a
|
|
# single parameter, 'cron'. Eg:
|
|
#
|
|
# 3 4 * * * /usr/local/sbin/renew-opendmarc-tlds.sh cron
|
|
#
|
|
# That will, at 3 minutes past the 4th hour (in whatever timezone cron is
|
|
# running it) invoke this script with 'cron'; we will then sleep between 10 and
|
|
# 50 seconds, before continuing.
|
|
#
|
|
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~8< cut here >8~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
#
|
|
# This should be "pretty portable"; the only things it depends upon are:
|
|
# * a POSIX shell which additionally implements 'local' (dash works)
|
|
# * the 'curl' command; change the fetch_candidate() function to replace that
|
|
# * the 'stat' command, to get the size of a file; else Perl
|
|
# + change size_of() if need be; it's defined per-OS
|
|
# * the 'hexdump' command and /dev/urandom existing
|
|
# + used when invoked with 'cron', to avoid retrieving on a minute boundary
|
|
# and contending with many other automated systems.
|
|
# + with bash/zsh, can replace with: $(( 10 + ( RANDOM % 40 ) ))
|
|
# + on Debian/Ubuntu systems, hexdump is in the 'bsdmainutils' package.
|
|
|
|
# Consider putting an email address inside the parentheses, something like
|
|
# noc@example.org or other reachable address, so that if something goes wrong
|
|
# and the server operators need to step in, they can see from logs who to
|
|
# contact instead of just blocking your IP:
|
|
readonly CurlUserAgent='renew-opendmarc-tlds/0.1 (distributed with Exim)'
|
|
|
|
# change this to your Exim run-time user (exim -n -bP exim_user) :
|
|
readonly RuntimeUser='_exim'
|
|
|
|
# Do not make this a directory which untrusted users can write to:
|
|
readonly StateDir='/var/cache/exim'
|
|
|
|
readonly URL='https://publicsuffix.org/list/public_suffix_list.dat'
|
|
|
|
readonly TargetShortFile='opendmarc.tlds'
|
|
|
|
# When replacing, new file must be at least this percentage the size of
|
|
# the old one or it's an error:
|
|
readonly MinNewSizeRation=90
|
|
|
|
# Each of these regexps must be matched by the file, or it's an error:
|
|
readonly MustExistRegexps='
|
|
^ac\.uk$
|
|
^org$
|
|
^tech$
|
|
'
|
|
|
|
# =======================8< end of configuration >8=======================
|
|
|
|
set -eu
|
|
|
|
readonly FullTargetPath="${StateDir}/${TargetShortFile}"
|
|
readonly WorkingFile="${FullTargetPath}.$$"
|
|
|
|
progname="$(basename "$0")"
|
|
note() { printf >&2 '%s: %s\n' "$progname" "$*"; }
|
|
die() { note "$@"; exit 1; }
|
|
|
|
# guard against stomping on file-permissions
|
|
[ ".$(id -un)" = ".${RuntimeUser:?}" ] || \
|
|
die "must be invoked as ${RuntimeUser}"
|
|
|
|
fetch_candidate() {
|
|
curl --user-agent "$CurlUserAgent" -fSs -o "${WorkingFile}" "${URL}"
|
|
}
|
|
|
|
case $(uname -s) in
|
|
*BSD|Darwin)
|
|
size_of() { stat -f %z "$1"; }
|
|
;;
|
|
Linux)
|
|
size_of() { stat -c %s "$1"; }
|
|
;;
|
|
*)
|
|
# why do we live in a world where Perl is the safe portable solution
|
|
# to getting the size of a file?
|
|
size_of() { perl -le 'print((stat($ARGV[0]))[7])' -- "$1"; }
|
|
;;
|
|
esac
|
|
|
|
sanity_check_candidate() {
|
|
local new_size prev_size re
|
|
new_size="$(size_of "$WorkingFile")"
|
|
|
|
for re in $MustExistRegexps; do
|
|
grep -qs "$re" -- "$WorkingFile" || \
|
|
die "regexp $re not found in $WorkingFile"
|
|
done
|
|
|
|
if ! prev_size="$(size_of "$FullTargetPath")"; then
|
|
note "missing previous file, can't size-compare: $FullTargetPath"
|
|
# We're sane by definition, probably initial fetch, and the
|
|
# stat failure and this note will be printed. That's fine; if
|
|
# a cron invocation is missing the file then something has gone
|
|
# badly wrong.
|
|
return 0
|
|
fi
|
|
local ratio
|
|
ratio=$(expr $new_size \* 100 / $prev_size)
|
|
if [ $ratio -lt $MinNewSizeRation ]; then
|
|
die "New $TargetShortFile candidate only ${ratio}% size of old; $new_size vs $prev_size"
|
|
fi
|
|
}
|
|
|
|
if [ "${1:-.}" = "cron" ]; then
|
|
shift
|
|
# Don't pull on-the-minute, wait for off-cycle-peak
|
|
sleep $(( ($(dd if=/dev/urandom bs=1 count=1 2>/dev/null | hexdump -e '1/1 "%u"') % 40) + 10))
|
|
fi
|
|
|
|
umask 022
|
|
fetch_candidate
|
|
sanity_check_candidate
|
|
mv -- "$WorkingFile" "$FullTargetPath"
|