fetch-sanesecurity-sigs.sh

#!/bin/bash
#
# fetch-sanesecurity-sigs
# by Malcolm Scott, Retrosnub Internet Services
# <malcolm at retrosnub dot co dot uk>
#
# http://www.retrosnub.co.uk/sanesecurity
# svn://svn.sanesecurity.retrosnub.co.uk/
#
# $Revision$
# $Date$
#
# -----------------------------------------------------------------------------
# Copyright (C) 2009 Malcolm Scott
#
# This program is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License version 2 as published by the
# Free Software Foundation.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along with
# this program; if not, write to the Free Software Foundation, Inc., 59 Temple
# Place, Suite 330, Boston, MA 02111-1307 USA
# -----------------------------------------------------------------------------
#
# INSTALLATION AND USAGE:
#
#  * Ensure that you have wget, gpg and rsync installed (in addition to a
#    standard set of UNIX tools).
#  * Configure this script by editing the configuration variables below.
#  * Set up cron to run this script periodically, at a randomly-selected time
#    (i.e. not just on the hour unless unavoidable), not more often than once
#    per hour.  The script should be run either as root or as the user clamd
#    runs as.  For example, add the following line to /etc/crontab or a file
#    in /etc/cron.d:
#         42 * * * *  root  /path/to/fetch-sanesecurity-sigs >/dev/null
#    (Redirection of the output to /dev/null is recommended when running from
#    cron as the script is verbose in normal operation.  This will not hide
#    errors, however.)
#
# Note that this script is tailored to the Sanesecurity setup (as of January
# 2009).  It should replace scripts using the pre-2009 setup (HTTP).  It is
# not intended to download non-Sanesecurity signatures; use another script
# for that purpose.


### Configuration ###

# ClamAV database location
clamd_dbdir="/var/lib/clamav"

# ClamAV daemon process ID file
# (If this is commented out, the daemon will not be reloaded automatically)
clamd_pidfile="/var/run/clamav/clamd.pid"

# Directory in which this script will keep its persistent data
data_dir="/var/lib/sanesecurity"

# Directory in which this script will keep its cache
# (This should not be the same as data_dir.  Any unexpected files in this
# directory will be deleted!)
cache_dir="/var/cache/sanesecurity"

# Mirror to use, in a form accepted by rsync
# (Leave set to the round robin address unless you know what you are doing:
# forcing the use of one particular mirror will cause excess load for that
# mirror)
mirror="rsync://rsync.sanesecurity.net/sanesecurity"

# Extra options for rsync
# The default, --contimeout=30, makes for faster recovery if a mirror is
# blocking your connection (e.g. if you connect too frequently).  However
# this is not available in older versions of rsync so you may need to
# remove it.
# Additionally, if you have a slow link you may want to add -z here to
# enable compression.
rsync_extra_opts="--contimeout=30"

# Minimum interval between updates, in minutes
# (Note that the download servers may be configured to drop connections made
# at too great a rate)
min_interval="30"

# Randomly sleep before downloading if running noninteractively?
# (Please leave this enabled, as it reduces peak load on the mirrors)
random_sleep=1

# URL of the Sanesecurity GnuPG public key
gpg_key_url="http://www.sanesecurity.net/publickey.gpg"

# Location of GnuPG home directory
# (If you change this, be sure that you understand the security implications:
# signatures by *any* key in your public keyring will be accepted)
gpg_homedir="$data_dir/gnupg"

# Extra options for GnuPG, if required
gpg_extra_opts=""

# Exclude logical signatures (*.ldb)?
# These are not supported by versions of ClamAV prior to 0.94.
# If you use an old version of ClamAV, you should enable this option.
#exclude_ldb=1

### End of configuration ###


umask 0022

# Check the configuration looks sane
if [ ! -d "$clamd_dbdir" ]
then
    echo "clamd_dbdir ($clamd_dbdir) does not exist; aborting" >&2
    echo "(check your configuration)" >&2
    exit 1
fi

mkdir -p "$data_dir" "$cache_dir"

# Set up GnuPG, if necessary
if [ ! -d "$gpg_homedir" ]
then
    echo "GnuPG homedir is nonexistant; initialising" >&2
    echo "(This should only occur once)" >&2
    mkdir -p "$gpg_homedir"
    chmod 0700 "$gpg_homedir"
    gpg_tmp="$(mktemp -t fetch-sanesecurity-sigs.XXXXXXXXXX)"
    if ! wget -O "$gpg_tmp" "$gpg_key_url"
    then
        echo "ERROR: could not fetch GnuPG public key; aborting" >&2
        rm -f "$gpg_tmp"
        exit 4
    fi
    if ! gpg --homedir "$gpg_homedir" $gpg_extra_opts --import "$gpg_tmp"
    then
        echo "ERROR: could not import GnuPG public key; aborting" >&2
        rm -f "$gpg_tmp"
        exit 4
    fi
    rm -f "$gpg_tmp"
fi

# This appears to be the most portable way to find the current timestamp
# (suggestions on how to avoid calling perl are very welcome)
time_now="$(perl -le print+time)"
if [ ! "$time_now" -gt 1 ]
then
    echo "Could not find current timestamp -- is perl installed?" >&2
    exit 5
fi

# Check that min_interval seconds have elapsed since last run
if [ -s "$data_dir/update-stamp" ]
then
    time_then="$(cat "$data_dir/update-stamp")"
    minutes_elapsed=$(( (time_now - time_then) / 60 ))
    if [ "$minutes_elapsed" -lt "$min_interval" ]
    then
        echo "Must wait at least $min_interval minutes between updates; aborting" >&2
        exit 2
    fi
fi

# Random sleep (see comment in configuration section)
if [ "$random_sleep" = "1" ]
then
    # Are we running noninteractively, i.e. without a tty on stdin?
    if ! tty -s
    then
        # $RANDOM is between 0 and 32767.
        # Use this to generate a time between 30 and 32767/200+30 = 193 seconds.
        sleep_time=$((RANDOM/200+30))
        echo "Sleeping for $sleep_time seconds."
        sleep $sleep_time
    fi
fi

# Update the cache
if [ "$exclude_ldb" = "1" ]
then
    rsync_extra_opts="$rsync_extra_opts --exclude=*.ldb"
    rm -f "$cache_dir"/*.ldb
fi
if ! rsync --progress --delete -rt $rsync_extra_opts "$mirror/." "$cache_dir/"
then
    echo "rsync failed; aborting." >&2
    exit 3
fi
echo "$time_now" > "$data_dir/update-stamp"
chmod 0644 "$cache_dir"/*
echo

# Iterate through the databases in the cache
installed=0
for db in "$cache_dir"/*.?db "$cache_dir"/*.ftm
do
    db_name=$(basename "$db")
    db_live="$clamd_dbdir/sanesecurity-$db_name"

    # Only pay any attention to this database if it's newer than the installed version
    if [ -e "$db_live" -a ! "$db" -nt "$db_live" ]
    then
        echo "$db_name is already up-to-date; skipping"
        continue
    fi

    # Zero-length databases have no value and confuse the test below
    if [ ! -s "$db" ]
    then
        echo "$db_name is zero-length; discarding"
        continue
    fi

    # Check that the GnuPG signature is present and correct
    if ! gpg_out=$(gpg --homedir "$gpg_homedir" $gpg_extra_opts --verify "$db.sig" "$db" 2>&1)
    then
        echo "SECURITY ERROR: $db_name has a bad GnuPG signature; discarding:" >&2
        echo "$gpg_out" >&2
        continue
    fi

    # Test the database by asking ClamAV to check something with it
    if ! clamscan --quiet --tempdir="${TMPDIR:-/tmp}" --database="$db" - < /dev/null
    then
        echo "ERROR: $db_name fails a simple test; discarding" >&2
        continue
    fi

    # Now we can actually install this database
    echo "Installing $db_name into $db_live"
    if rsync -p "$db" "$db_live"
    then
        installed=$((installed+1))

        # Clean up stuff left behind by old scripts
        rm -f "$clamd_dbdir/$db_name"*
    fi
done

# Finished; display summary and perhaps reload clamd
echo
if [ "$installed" -gt 0 ]
then
    if [ "$installed" -eq 1 ]
    then
        s=""
    else
        s="s"
    fi
    echo "Installed $installed database$s"

    # Is clamd running?
    if [ "$clamd_pidfile" -a -f "$clamd_pidfile" ]
    then
        echo "Reloading ClamAV daemon"
        clamdscan --reload
    fi
else
    echo "No databases installed."
fi

exit 0