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nixos/geoip-updater: new service
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The GeoIP databases from MaxMind have no stable URLs and change every
month (or so). Our current method of packaging these database in Nix and
playing catch-up with ever-changing file hashes is a bad idea. For
instance, it makes it impossible to realize old NixOS configurations.

This patch adds a NixOS service that periodically updates the GeoIP
databases in /var/lib/geoip-databases. Moving NixOS modules over can be
done in later patches.

I tried adding MD5 check, but not all databases have them, so i skipped
it. We are downloading over HTTPS though, it should be good. I also
tried adding zip support, but the first zip file I extracted had a
different filename inside than the archive name, which breaks an
assumption in this service, so I skipped that too.

Changes v9 -> v10:
  - Pass "--max-time" to curl to set upper bound on downloads (ensures
    no indefinite hanging if there's problem with networking).
    Timeout for network connectivity check: 60s.
    Timeout for geoip database (each): 15m.

Changes v8 -> v9:
  - Mention the random timer delay in the documentation for the
    'interval' option.

Changes v7 -> v8:
  - Add "RemainAfterExit=true" for the setup service, so it won't be
    restarted needlessly. (Thanks @danbst!)

Changes v6 -> v7:
  - Add --skip-existing flag to geoip-updater, which skips updating
    existing database files. Pass that flag when we run the service on
    boot (and on any NixOS configuration change).
    (IMHO, this is somewhat a workaround for systemd persistent timers
    not being triggered immediately when a timer has never expired
    before. But it does have the nice side effect of ensuring that the
    installed databases always correspond to the configured ones, since
    the service is now always run after configuration changes.)

Changes v5 -> v6:
  - Update database files atomically (per DB)
  - If a database is removed from the configuration, it'll be removed
    from /var/lib/geoip-databases too (on next run).
  - Add NixOS module assertion so that if user inputs non- .gz or .xz
    file there will be a build time error instead of runtime.
  - Run updater as user "nobody" instead of "root".
  - Rename NixOS service from "geoip-databases" to "geoip-updater".
  - Drop RemainAfterExit, or else the timer won't trigger the unit.
  - Bring back "curl --fail", or else we won't catch and log curl
    failures.

Changes v4 -> v5:
  - Add "GeoLite2-City.mmdb.gz" to default database list.

Changes v3 -> v4:
  - Remove unneeded geoip-updater-setup.service after adding
    'wantedBy = [ "multi-user.target" ]' directly to
    geoip-updater.service
  - Drop unneeded "Service" name from service descriptions.

Changes v2 -> v3:
  - Network may be down when starting from a cold boot, so try a few
    times. Possibly, if using systemd-networkd, it'll pass on the first
    try. But with default DHCP on NixOS, the service is started before
    hostnames can be resolved and thus we need a few extra seconds.
  - Add error handling and mark service as failed if fatal error.
  - Add proper syslog log levels.
  - Add RandomizedDelaySec=3600 to the timer to not put high load on the
    MaxMind servers. Suggested by @Mic92.
  - Set RemainAfterExit on geoip-updater.service instead of
    geoip-updater-setup.service. (The latter is only a proxy that pulls
    in the former service).

Changes v1 -> v2:
From Данило Глинський (Danylo Hlynskyi) <abcz2.uprola@gmail.com>:
  nixos/geoip-databases: add `databases` option and fix initial setup

  There were two great issues when using this service:
  - When you just enable service, databases aren't downloaded, they are
    downloaded when timer triggers. Fixed this with automatic download on
    first system activation.
  - When there is no internet, updater outputs nothing to logs, which is
    IMO misbehavior. Fixed this with removing `--fail` option, better be
    explicit here.
  • Loading branch information
@bjornfor
bjornfor committed Feb 12, 2017
1 parent 9e04b57 commit 824d82f
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1 change: 1 addition & 0 deletions nixos/modules/module-list.nix
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Expand Up @@ -259,6 +259,7 @@
./services/misc/felix.nix
./services/misc/folding-at-home.nix
./services/misc/gammu-smsd.nix
./services/misc/geoip-updater.nix
#./services/misc/gitit.nix
./services/misc/gitlab.nix
./services/misc/gitolite.nix
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300 changes: 300 additions & 0 deletions nixos/modules/services/misc/geoip-updater.nix
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@@ -0,0 +1,300 @@
{ config, lib, pkgs, ... }:

with lib;

let
cfg = config.services.geoip-updater;

dbBaseUrl = "https://geolite.maxmind.com/download/geoip/database";

randomizedTimerDelaySec = "3600";

# Use writeScriptBin instead of writeScript, so that argv[0] (logged to the
# journal) doesn't include the long nix store path hash. (Prefixing the
# ExecStart= command with '@' doesn't work because we start a shell (new
# process) that creates a new argv[0].)
geoip-updater = pkgs.writeScriptBin "geoip-updater" ''
#!${pkgs.stdenv.shell}
skipExisting=0
debug()
{
echo "<7>$@"
}
info()
{
echo "<6>$@"
}
error()
{
echo "<3>$@"
}
die()
{
error "$@"
exit 1
}
waitNetworkOnline()
{
ret=1
for i in $(seq 6); do
curl_out=$("${pkgs.curl.bin}/bin/curl" \
--silent --fail --show-error --max-time 60 "${dbBaseUrl}" 2>&1)
if [ $? -eq 0 ]; then
debug "Server is reachable (try $i)"
ret=0
break
else
debug "Server is unreachable (try $i): $curl_out"
sleep 10
fi
done
return $ret
}
dbFnameTmp()
{
dburl=$1
echo "${cfg.databaseDir}/.$(basename "$dburl")"
}
dbFnameTmpDecompressed()
{
dburl=$1
echo "${cfg.databaseDir}/.$(basename "$dburl")" | sed 's/\.\(gz\|xz\)$//'
}
dbFname()
{
dburl=$1
echo "${cfg.databaseDir}/$(basename "$dburl")" | sed 's/\.\(gz\|xz\)$//'
}
downloadDb()
{
dburl=$1
curl_out=$("${pkgs.curl.bin}/bin/curl" \
--silent --fail --show-error --max-time 900 -L -o "$(dbFnameTmp "$dburl")" "$dburl" 2>&1)
if [ $? -ne 0 ]; then
error "Failed to download $dburl: $curl_out"
return 1
fi
}
decompressDb()
{
fn=$(dbFnameTmp "$1")
ret=0
case "$fn" in
*.gz)
cmd_out=$("${pkgs.gzip}/bin/gzip" --decompress --force "$fn" 2>&1)
;;
*.xz)
cmd_out=$("${pkgs.xz.bin}/bin/xz" --decompress --force "$fn" 2>&1)
;;
*)
cmd_out=$(echo "File \"$fn\" is neither a .gz nor .xz file")
false
;;
esac
if [ $? -ne 0 ]; then
error "$cmd_out"
ret=1
fi
}
atomicRename()
{
dburl=$1
mv "$(dbFnameTmpDecompressed "$dburl")" "$(dbFname "$dburl")"
}
removeIfNotInConfig()
{
# Arg 1 is the full path of an installed DB.
# If the corresponding database is not specified in the NixOS config we
# remove it.
db=$1
for cdb in ${lib.concatStringsSep " " cfg.databases}; do
confDb=$(echo "$cdb" | sed 's/\.\(gz\|xz\)$//')
if [ "$(basename "$db")" = "$(basename "$confDb")" ]; then
return 0
fi
done
rm "$db"
if [ $? -eq 0 ]; then
debug "Removed $(basename "$db") (not listed in services.geoip-updater.databases)"
else
error "Failed to remove $db"
fi
}
removeUnspecifiedDbs()
{
for f in "${cfg.databaseDir}/"*; do
test -f "$f" || continue
case "$f" in
*.dat|*.mmdb|*.csv)
removeIfNotInConfig "$f"
;;
*)
debug "Not removing \"$f\" (unknown file extension)"
;;
esac
done
}
downloadAndInstall()
{
dburl=$1
if [ "$skipExisting" -eq 1 -a -f "$(dbFname "$dburl")" ]; then
debug "Skipping existing file: $(dbFname "$dburl")"
return 0
fi
downloadDb "$dburl" || return 1
decompressDb "$dburl" || return 1
atomicRename "$dburl" || return 1
info "Updated $(basename "$(dbFname "$dburl")")"
}
for arg in "$@"; do
case "$arg" in
--skip-existing)
skipExisting=1
info "Option --skip-existing is set: not updating existing databases"
;;
*)
error "Unknown argument: $arg";;
esac
done
waitNetworkOnline || die "Network is down (${dbBaseUrl} is unreachable)"
test -d "${cfg.databaseDir}" || die "Database directory (${cfg.databaseDir}) doesn't exist"
debug "Starting update of GeoIP databases in ${cfg.databaseDir}"
all_ret=0
for db in ${lib.concatStringsSep " \\\n " cfg.databases}; do
downloadAndInstall "${dbBaseUrl}/$db" || all_ret=1
done
removeUnspecifiedDbs || all_ret=1
if [ $all_ret -eq 0 ]; then
info "Completed GeoIP database update in ${cfg.databaseDir}"
else
error "Completed GeoIP database update in ${cfg.databaseDir}, with error(s)"
fi
# Hack to work around systemd journal race:
# https://github.com/systemd/systemd/issues/2913
sleep 2
exit $all_ret
'';

in

{
options = {
services.geoip-updater = {
enable = mkOption {
default = false;
type = types.bool;
description = ''
Whether to enable periodic downloading of GeoIP databases from
maxmind.com. You might want to enable this if you, for instance, use
ntopng or Wireshark.
'';
};

interval = mkOption {
type = types.str;
default = "weekly";
description = ''
Update the GeoIP databases at this time / interval.
The format is described in
<citerefentry><refentrytitle>systemd.time</refentrytitle>
<manvolnum>7</manvolnum></citerefentry>.
To prevent load spikes on maxmind.com, the timer interval is
randomized by an additional delay of ${randomizedTimerDelaySec}
seconds. Setting a shorter interval than this is not recommended.
'';
};

databaseDir = mkOption {
type = types.path;
default = "/var/lib/geoip-databases";
description = ''
Directory that will contain GeoIP databases.
'';
};

databases = mkOption {
type = types.listOf types.str;
default = [
"GeoLiteCountry/GeoIP.dat.gz"
"GeoIPv6.dat.gz"
"GeoLiteCity.dat.xz"
"GeoLiteCityv6-beta/GeoLiteCityv6.dat.gz"
"asnum/GeoIPASNum.dat.gz"
"asnum/GeoIPASNumv6.dat.gz"
"GeoLite2-Country.mmdb.gz"
"GeoLite2-City.mmdb.gz"
];
description = ''
Which GeoIP databases to update. The full URL is ${dbBaseUrl}/ +
<literal>the_database</literal>.
'';
};

};

};

config = mkIf cfg.enable {

assertions = [
{ assertion = (builtins.filter
(x: builtins.match ".*\.(gz|xz)$" x == null) cfg.databases) == [];
message = ''
services.geoip-updater.databases supports only .gz and .xz databases.
Current value:
${toString cfg.databases}
Offending element(s):
${toString (builtins.filter (x: builtins.match ".*\.(gz|xz)$" x == null) cfg.databases)};
'';
}
];

systemd.timers.geoip-updater =
{ description = "GeoIP Updater Timer";
partOf = [ "geoip-updater.service" ];
wantedBy = [ "timers.target" ];
timerConfig.OnCalendar = cfg.interval;
timerConfig.Persistent = "true";
timerConfig.RandomizedDelaySec = randomizedTimerDelaySec;
};

systemd.services.geoip-updater = {
description = "GeoIP Updater";
after = [ "network-online.target" "nss-lookup.target" ];
wants = [ "network-online.target" ];
preStart = ''
mkdir -p "${cfg.databaseDir}"
chmod 755 "${cfg.databaseDir}"
chown nobody:root "${cfg.databaseDir}"
'';
serviceConfig = {
ExecStart = "${geoip-updater}/bin/geoip-updater";
User = "nobody";
PermissionsStartOnly = true;
};
};

systemd.services.geoip-updater-setup = {
description = "GeoIP Updater Setup";
after = [ "network-online.target" "nss-lookup.target" ];
wants = [ "network-online.target" ];
wantedBy = [ "multi-user.target" ];
conflicts = [ "geoip-updater.service" ];
preStart = ''
mkdir -p "${cfg.databaseDir}"
chmod 755 "${cfg.databaseDir}"
chown nobody:root "${cfg.databaseDir}"
'';
serviceConfig = {
ExecStart = "${geoip-updater}/bin/geoip-updater --skip-existing";
User = "nobody";
PermissionsStartOnly = true;
# So it won't be (needlessly) restarted:
RemainAfterExit = true;
};
};

};
}

5 comments on commit 824d82f

@abbradar
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If I get that correctly, one will be able to tamper with database as nobody (remove or modify it). Not sure if you can fix that without introducing new user. I may also be just plain wrong -- haven't tested that in practice!

@danbst
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@danbst danbst commented on 824d82f Feb 12, 2017

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Right, but maybe better wait new systemd (dynamic users feature) and fix then properly?

@abbradar
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This then introduces possible security issue meanwhile -- I'm not sure how critical GeoIP can be (maybe for a shop with custom per-country prices this can lead to a money loss) but surely you don't want nobodys changing this...

@bjornfor
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Should we create a geoip-updater user?

Or is there some way to run the updater simply as root, but in a "protected" mode so that even if there is a security flaw in the downloader, it cannot be used for executing code as root (or have access to the whole system).

I know systemd has some options related to this, but need to look closer.

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I think the simplest/safest way would be to create user for now and to drop it after we get dynamic users as @danbst proposed. Maybe leave a FIXME comment?

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