#!/usr/bin/perl

# Copyright (C) 2003 Jonathan Middleton <jjm@ixtab.org.uk
# Copyright (C) 2001 Paul Slootman <paul@debian.org>

# This file is part of Logcheck.

# Logcheck is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.

# Logcheck 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 Foobar; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

my ($logfile, $offsetfile) = @ARGV;
if (! -f $logfile) {
    print "File $logfile cannot be read.\n";
    exit 66;
}
unless ($offsetfile) {
    # offsetfile not given, use .offset/$logfile in the same directory
    $offsetfile = $logfile . '.offset';
}

unless (open(LOGFILE, $logfile)) {
    print "File $logfile cannot be read.\n";
    exit 66;
}

my ($inode, $offset) = (0, 0);

if (open(OFFSET, $offsetfile)) {
    $_ = <OFFSET>;
    if (defined) {
	chomp;
	$inode = $_;
	$_ = <OFFSET>;
	if (defined) {
	    chomp;
	    $offset = $_;
	}
    }
}

my ($ino, $size);
unless ((undef,$ino,undef,undef,undef,undef,undef,$size) = stat $logfile) {
    print "Cannot get $logfile file size.\n", $logfile;
    exit 65;
}

if ($inode == $ino) {
    exit 0 if $offset == $size; # short cut
    if ($offset > $size) {
        $offset = 0;
        print "***************\n";
        print "*** WARNING ***: Log file $logfile is smaller than last time checked!\n";
        print "*************** This could indicate tampering.\n";
    }
}
if ($inode != $ino || $offset > $size) {
    $offset = 0;
}

seek(LOGFILE, $offset, 0);

while (<LOGFILE>) {
    print;
}

$size = tell LOGFILE;
close LOGFILE;

unless (open(OFFSET, ">$offsetfile")) {
    print "File $offsetfile cannot be created. Check your permissions.\n";
    exit 73;
}
unless (chmod 0600, $offsetfile) {
    print "Cannot set permissions on file $offsetfile\n";
    exit 65;
}
print OFFSET "$ino\n$size\n";
close OFFSET;

exit 0;