Perl CGI hacked? But I'm doing everything right
I just noticed some strange PHP files in one of my web directories. They turned out to be spammer-placed exploit files.
They've been there since 2006, around the time that I was running a high-profile donation campaign using a CGI script of mine. And the files were placed in the script's writeable directory, so I suspect that my script might have been exploited somehow.
But I'm using Perl "taint checking", strict, etc, and I'm never passing query data to the shell (it never invokes the shell!) or using query data to generate a file path for OPEN... I only OPEN files that I specify directly in the script. I do pass query data INTO written files as file content, but as far as I'm aware, that's not dangerous.
I've stared at these scripts and cannot see anything, and I've studied all the standard Perl CGI holes. Of course, they could have gotten the password to my hosting account somehow, but the fact that these scripts were placed in my CGI script's data directory makes me suspect the script. (Also, them getting my password "somehow" is a much scarier explanation.) Also, around that time, my logs show lots of "Warning, IPN received from a non-PayPal address" messages, with those IPs coming from Russia. So it seems like someone was at least TRYING to hack these scripts.
Two scripts are involved, and I'm pasting them below. Anyone see anything that could be exploited to write unexpected files?
Here's the first script (for receiving PayPal IPN and tracking the donations, and also tracking which site is generating the most donations):
#!/usr/bin/perl -wT
# Created by Jason Rohrer, December 2005
# Copied basic structure and PayPal protocol code from DonationTracker v0.1
# Script settings
# Basic settings
# email address this script is tracking payments for
my $receiverEmail = "receiver\@yahoo.com";
# This script must have write permissions to BOTH of its DataDirectories.
# It must be able to create files in these directories.
# On most web servers, this means the directory must be world-writable.
# ( chmod a+w donationData )
# These paths are relative to the location of the script.
my $pubDataDirectory = "../goliath";
my $privDataDirectory = "../../cgi-data/donationNet";
# If this $privDataDirectory setting is changed, you must also change it below
# where the error LOG is opened
# end of Basic settings
# Advanced settings
# Ignore these unless you know what you are doing.
# where the log of incoming donations is stored
my $donationLogFile = "$privDataDirectory/donationLog.txt";
# location of public data generated by this script
my $overallSumFile = "$pubDataDirectory/overallSum.html";
my $overallCountFile = "$pubDataDirectory/donationCount.html";
my $topSiteListFile = "$pubDataDirectory/topSiteList.html";
# private data tracking which donation total coming from each site
my $siteTrackingFile = "$privDataDirectory/siteTracking.txt";
# Where non-fatal errors and other information is logged
my $logFile = "$privDataDirectory/log.txt";
# IP of notify.paypal.com
# used as cheap security to make sure IPN is only coming from PayPal
my $paypalNotifyIP = "216.113.188.202";
# setup a local error log
use CGI::Carp qw( carpout );
BEGIN {
# location of the error log
my $errorLogLocation = "../../cgi-data/donationNet/errors.log";
use CGI::Carp qw( carpout );
open( LOG, ">>$errorLogLocation" ) or
die( "Unable to open $errorLogLocation: $!\n" );
carpout( LOG );
}
# end of Advanced settings
# end of script settings
use strict;
use CGI; # Object-Oriented CGI library
# setup stuff, make sure our needed files are initialized
if( not doesFileExist( $overallSumFile ) ) {
writeFile( $overallSumFile, "0" );
}
if( not doesFileExist( $overallCountFile ) ) {
writeFile( $overallCountFile, "0" );
}
if( not doesFileExist( $topSiteListFile ) ) {
writeFile( $topSiteListFile, "" );
}
if( not doesFileExist( $siteTrackingFile ) ) {
writeFile( $siteTrackingFile, "" );
}
# allow group to write to our data files
umask( oct( "02" ) );
# create object to extract the CGI query elements
my $cgiQuery = CGI->new();
# always at least send an HTTP OK header
print $cgiQuery->header( -type=>'text/html', -expires=>'now',
-Cache_control=>'no-cache' );
my $remoteAddress = $cgiQuery->remote_host();
my $action = $cgiQuery->param( "action" ) || '';
# first, check if our count/sum is being queried by another script
if( $action eq "checkResults" ) {
my $sum = readTrimmedFileValue( $overallSumFile );
my $count = readTrimmedFileValue( 开发者_JAVA技巧$overallCountFile );
print "$count \$$sum";
}
elsif( $remoteAddress eq $paypalNotifyIP ) {
my $donorName;
# $customField contains URL of site that received donation
my $customField = $cgiQuery->param( "custom" ) || '';
# untaint and find whitespace-free string (assume it's a URL)
( my $siteURL ) = ( $customField =~ /(\S+)/ );
my $amount = $cgiQuery->param( "mc_gross" ) || '';
my $currency = $cgiQuery->param( "mc_currency" ) || '';
my $fee = $cgiQuery->param( "mc_fee" ) || '0';
my $date = $cgiQuery->param( "payment_date" ) || '';
my $transactionID = $cgiQuery->param( "txn_id" ) || '';
# these are for our private log only, for tech support, etc.
# this information should not be stored in a web-accessible
# directory
my $payerFirstName = $cgiQuery->param( "first_name" ) || '';
my $payerLastName = $cgiQuery->param( "last_name" ) || '';
my $payerEmail = $cgiQuery->param( "payer_email" ) || '';
# only track US Dollars
# (can't add apples to oranges to get a final sum)
if( $currency eq "USD" ) {
my $status = $cgiQuery->param( "payment_status" ) || '';
my $completed = $status eq "Completed";
my $pending = $status eq "Pending";
my $refunded = $status eq "Refunded";
if( $completed or $pending or $refunded ) {
# write all relevant payment info into our private log
addToFile( $donationLogFile,
"$transactionID $date\n" .
"From: $payerFirstName $payerLastName " .
"($payerEmail)\n" .
"Amount: \$$amount\n" .
"Fee: \$$fee\n" .
"Status: $status\n\n" );
my $netDonation;
if( $refunded ) {
# subtract from total sum
my $oldSum =
readTrimmedFileValue( $overallSumFile );
# both the refund amount and the
# fee on the refund are now reported as negative
# this changed as of February 13, 2004
$netDonation = $amount - $fee;
my $newSum = $oldSum + $netDonation;
# format to show 2 decimal places
my $newSumString = sprintf( "%.2f", $newSum );
writeFile( $overallSumFile, $newSumString );
my $oldCount = readTrimmedFileValue( $overallCountFile );
my $newCount = $oldCount - 1;
writeFile( $overallCountFile, $newCount );
}
# This check no longer needed as of February 13, 2004
# since now only one IPN is sent for a refund.
#
# ignore negative completed transactions, since
# they are reported for each refund (in addition to
# the payment with Status: Refunded)
if( $completed and $amount > 0 ) {
# fee has not been subtracted yet
# (fee is not reported for Pending transactions)
my $oldSum =
readTrimmedFileValue( $overallSumFile );
$netDonation = $amount - $fee;
my $newSum = $oldSum + $netDonation;
# format to show 2 decimal places
my $newSumString = sprintf( "%.2f", $newSum );
writeFile( $overallSumFile, $newSumString );
my $oldCount = readTrimmedFileValue(
$overallCountFile );
my $newCount = $oldCount + 1;
writeFile( $overallCountFile, $newCount );
}
if( $siteURL =~ /http:\/\/\S+/ ) {
# a valid URL
# track the total donations of this site
my $siteTrackingText = readFileValue( $siteTrackingFile );
my @siteDataList = split( /\n/, $siteTrackingText );
my $newSiteData = "";
my $exists = 0;
foreach my $siteData ( @siteDataList ) {
( my $url, my $siteSum ) = split( /\s+/, $siteData );
if( $url eq $siteURL ) {
$exists = 1;
$siteSum += $netDonation;
}
$newSiteData = $newSiteData . "$url $siteSum\n";
}
if( not $exists ) {
$newSiteData = $newSiteData . "$siteURL $netDonation";
}
trimWhitespace( $newSiteData );
writeFile( $siteTrackingFile, $newSiteData );
# now generate the top site list
# our comparison routine, descending order
sub highestTotal {
( my $url_a, my $total_a ) = split( /\s+/, $a );
( my $url_b, my $total_b ) = split( /\s+/, $b );
return $total_b <=> $total_a;
}
my @newSiteDataList = split( /\n/, $newSiteData );
my @sortedList = sort highestTotal @newSiteDataList;
my $listHTML = "<TABLE BORDER=0>\n";
foreach my $siteData ( @sortedList ) {
( my $url, my $siteSum ) = split( /\s+/, $siteData );
# format to show 2 decimal places
my $siteSumString = sprintf( "%.2f", $siteSum );
$listHTML = $listHTML .
"<TR><TD><A HREF=\"$url\">$url</A></TD>".
"<TD ALIGN=RIGHT>\$$siteSumString</TD></TR>\n";
}
$listHTML = $listHTML . "</TABLE>";
writeFile( $topSiteListFile, $listHTML );
}
}
else {
addToFile( $logFile, "Payment status unexpected\n" );
addToFile( $logFile, "status = $status\n" );
}
}
else {
addToFile( $logFile, "Currency not USD\n" );
addToFile( $logFile, "currency = $currency\n" );
}
}
else {
# else not from paypal, so it might be a user accessing the script
# URL directly for some reason
my $customField = $cgiQuery->param( "custom" ) || '';
my $date = $cgiQuery->param( "payment_date" ) || '';
my $transactionID = $cgiQuery->param( "txn_id" ) || '';
my $amount = $cgiQuery->param( "mc_gross" ) || '';
my $payerFirstName = $cgiQuery->param( "first_name" ) || '';
my $payerLastName = $cgiQuery->param( "last_name" ) || '';
my $payerEmail = $cgiQuery->param( "payer_email" ) || '';
my $fee = $cgiQuery->param( "mc_fee" ) || '0';
my $status = $cgiQuery->param( "payment_status" ) || '';
# log it
addToFile( $donationLogFile,
"WARNING: got IPN from unexpected IP address\n" .
"IP address: $remoteAddress\n" .
"$transactionID $date\n" .
"From: $payerFirstName $payerLastName " .
"($payerEmail)\n" .
"Amount: \$$amount\n" .
"Fee: \$$fee\n" .
"Status: $status\n\n" );
# print an error page
print "Request blocked.";
}
##
# Reads file as a string.
#
# @param0 the name of the file.
#
# @return the file contents as a string.
#
# Example:
# my $value = readFileValue( "myFile.txt" );
##
sub readFileValue {
my $fileName = $_[0];
open( FILE, "$fileName" )
or die( "Failed to open file $fileName: $!\n" );
flock( FILE, 1 )
or die( "Failed to lock file $fileName: $!\n" );
my @lineList = <FILE>;
my $value = join( "", @lineList );
close FILE;
return $value;
}
##
# Reads file as a string, trimming leading and trailing whitespace off.
#
# @param0 the name of the file.
#
# @return the trimmed file contents as a string.
#
# Example:
# my $value = readFileValue( "myFile.txt" );
##
sub readTrimmedFileValue {
my $returnString = readFileValue( $_[0] );
trimWhitespace( $returnString );
return $returnString;
}
##
# Writes a string to a file.
#
# @param0 the name of the file.
# @param1 the string to print.
#
# Example:
# writeFile( "myFile.txt", "the new contents of this file" );
##
sub writeFile {
my $fileName = $_[0];
my $stringToPrint = $_[1];
open( FILE, ">$fileName" )
or die( "Failed to open file $fileName: $!\n" );
flock( FILE, 2 )
or die( "Failed to lock file $fileName: $!\n" );
print FILE $stringToPrint;
close FILE;
}
##
# Checks if a file exists in the filesystem.
#
# @param0 the name of the file.
#
# @return 1 if it exists, and 0 otherwise.
#
# Example:
# $exists = doesFileExist( "myFile.txt" );
##
sub doesFileExist {
my $fileName = $_[0];
if( -e $fileName ) {
return 1;
}
else {
return 0;
}
}
##
# Trims any whitespace from the beginning and end of a string.
#
# @param0 the string to trim.
##
sub trimWhitespace {
# trim from front of string
$_[0] =~ s/^\s+//;
# trim from end of string
$_[0] =~ s/\s+$//;
}
##
# Appends a string to a file.
#
# @param0 the name of the file.
# @param1 the string to append.
#
# Example:
# addToFile( "myFile.txt", "the new contents of this file" );
##
sub addToFile {
my $fileName = $_[0];
my $stringToPrint = $_[1];
open( FILE, ">>$fileName" )
or die( "Failed to open file $fileName: $!\n" );
flock( FILE, 2 )
or die( "Failed to lock file $fileName: $!\n" );
print FILE $stringToPrint;
close FILE;
}
##
# Makes a directory file.
#
# @param0 the name of the directory.
# @param1 the octal permission mask.
#
# Example:
# makeDirectory( "myDir", oct( "0777" ) );
##
sub makeDirectory {
my $fileName = $_[0];
my $permissionMask = $_[1];
mkdir( $fileName, $permissionMask );
}
And, there's some redundancy here (sorry about that... completeness?), but here's the second script (for generating website HTML buttons that people can add to their own site):
#!/usr/bin/perl -wT
# Created by Jason Rohrer, December 2005
# Script settings
# Basic settings
my $templateFile = "buttonTemplate.html";
# end of Basic settings
# Advanced settings
# Ignore these unless you know what you are doing.
# setup a local error log
use CGI::Carp qw( carpout );
BEGIN {
# location of the error log
my $errorLogLocation = "../../cgi-data/donationNet/errors.log";
use CGI::Carp qw( carpout );
open( LOG, ">>$errorLogLocation" ) or
die( "Unable to open $errorLogLocation: $!\n" );
carpout( LOG );
}
# end of Advanced settings
# end of script settings
use strict;
use CGI; # Object-Oriented CGI library
# create object to extract the CGI query elements
my $cgiQuery = CGI->new();
# always at least send an HTTP OK header
print $cgiQuery->header( -type=>'text/html', -expires=>'now',
-Cache_control=>'no-cache' );
my $siteURL = $cgiQuery->param( "site_url" ) || '';
print "Paste this HTML into your website:<BR>\n";
print "<FORM><TEXTAREA COLS=40 ROWS=10>\n";
my $buttonTemplate = readFileValue( $templateFile );
$buttonTemplate =~ s/SITE_URL/$siteURL/g;
# escape all tags
$buttonTemplate =~ s/&/&/g;
$buttonTemplate =~ s/</</g;
$buttonTemplate =~ s/>/>/g;
print $buttonTemplate;
print "\n</TEXTAREA></FORM>";
##
# Reads file as a string.
#
# @param0 the name of the file.
#
# @return the file contents as a string.
#
# Example:
# my $value = readFileValue( "myFile.txt" );
##
sub readFileValue {
my $fileName = $_[0];
open( FILE, "$fileName" )
or die( "Failed to open file $fileName: $!\n" );
flock( FILE, 1 )
or die( "Failed to lock file $fileName: $!\n" );
my @lineList = <FILE>;
my $value = join( "", @lineList );
close FILE;
return $value;
}
##
# Reads file as a string, trimming leading and trailing whitespace off.
#
# @param0 the name of the file.
#
# @return the trimmed file contents as a string.
#
# Example:
# my $value = readFileValue( "myFile.txt" );
##
sub readTrimmedFileValue {
my $returnString = readFileValue( $_[0] );
trimWhitespace( $returnString );
return $returnString;
}
##
# Writes a string to a file.
#
# @param0 the name of the file.
# @param1 the string to print.
#
# Example:
# writeFile( "myFile.txt", "the new contents of this file" );
##
sub writeFile {
my $fileName = $_[0];
my $stringToPrint = $_[1];
open( FILE, ">$fileName" )
or die( "Failed to open file $fileName: $!\n" );
flock( FILE, 2 )
or die( "Failed to lock file $fileName: $!\n" );
print FILE $stringToPrint;
close FILE;
}
##
# Checks if a file exists in the filesystem.
#
# @param0 the name of the file.
#
# @return 1 if it exists, and 0 otherwise.
#
# Example:
# $exists = doesFileExist( "myFile.txt" );
##
sub doesFileExist {
my $fileName = $_[0];
if( -e $fileName ) {
return 1;
}
else {
return 0;
}
}
##
# Trims any whitespace from the beginning and end of a string.
#
# @param0 the string to trim.
##
sub trimWhitespace {
# trim from front of string
$_[0] =~ s/^\s+//;
# trim from end of string
$_[0] =~ s/\s+$//;
}
##
# Appends a string to a file.
#
# @param0 the name of the file.
# @param1 the string to append.
#
# Example:
# addToFile( "myFile.txt", "the new contents of this file" );
##
sub addToFile {
my $fileName = $_[0];
my $stringToPrint = $_[1];
open( FILE, ">>$fileName" )
or die( "Failed to open file $fileName: $!\n" );
flock( FILE, 2 )
or die( "Failed to lock file $fileName: $!\n" );
print FILE $stringToPrint;
close FILE;
}
##
# Makes a directory file.
#
# @param0 the name of the directory.
# @param1 the octal permission mask.
#
# Example:
# makeDirectory( "myDir", oct( "0777" ) );
##
sub makeDirectory {
my $fileName = $_[0];
my $permissionMask = $_[1];
mkdir( $fileName, $permissionMask );
}
I've seen something similar before. In our case, I'm pretty sure the hackers used a buffer overflow in a library that hadn't been updated. They were then able to use a PHP shell to write files the server.
It's quite likely the problem wasn't in your code. Updating your software more often would make attacks less likely but unfortunately it's impossible to be completely hack-proof. Chances are that they were scanning for a common vulnerability in an old version of software.
Been a while since I played with perl's CGI module, but are you sure CGI::param escapes the values? From where I'm sitting, the values may contain backticks and thus will be expanded and executed.
You could refactor your code to make all the filepath references into compile-time constants with the constant pragma:
use constant {
DIR_PRIVATE_DATA => "/paths/of/glory",
FILE_DONATION_LOG => "donationLog.txt"
};
open( FILE, ">>".DIR_PRIVATE_DATA."/".FILE_DONATION_LOG );
Dealing with constants is a pain because they don't get interpolated by qq, and you've got to constantly endlessly be using (s)printf or a lot of concatenation operators. But it should make it a lot harder for ne'erdowells to alter any arguments that are being passed as filepaths.
Your code seems quite safe to me. I would only slightly object to the use of relative paths for the files, that makes me a little uncomfortable, but it's hard to imagine some security risk in that. I'd bet the vulnerability was somewhere below (perl, apache ...)
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