shellcodetester -asm file.asm

ShellcodeTester v0.2.0 by Helvio Junior (M4v3r1ck)
ShellcodeTester is a tool to assembly, compile and test ASM shellcode.
https://github.com/helviojunior/shellcodetester

 [+] Startup parameters
     command line: shellcodetester -asm test_linux.asm
     log level: NOTSET
     transform format: RAW
     bad chars: 0x00

 [+] start time 2023-02-12 01:53:56
 [+] Assembling x86 file teste_linux.asm to /home/shellcodetester/st_test_linux.o
 [+] Compiling x86 binary to /home/shellcodetester/st_test_linux.elf32
 [+] Payload size: 65 bytes
 [+] Final size of RAW data: 160 bytes
31c0b00431dbb301eb1259ba00000000b220cd8031c0b00131dbcd80e8e9ffffff4c616220303120636f6d706c657461646f20636f6d207375636573736f210a00

 [+] End time 2023-02-12 01:53:56

$ nasm_shell
┌─[NASM Shell]─[x86 linux]─[ASM → Hex]
└──╼➤ push eax
[+] Payload size: 1 bytes
[+] Final size of RAW data: 2 bytes
50

[+] Disassembly
   0:	50                   	push   eax

┌─[NASM Shell]─[x86 linux]─[ASM → Hex]
└──╼➤ push eax ; retn 4
[+] Payload size: 4 bytes
[+] Final size of RAW data: 8 bytes
50c20400

[+] Disassembly
   0:	50                   	push   eax
   1:	c2 04 00             	ret    0x4

$ nasm_shell --mode dis
┌─[NASM Shell]─[x86 linux]─[Hex → ASM]
└──╼➤ 50ff501c
[+] Payload size: 4 bytes
[+] Final size of RAW data: 8 bytes
50ff501c

[+] Disassembly
   0:	50                   	push   eax
   1:	ff 50 1c             	call   DWORD PTR [eax+0x1c]

$ nasm_shell --arch x86_64
┌─[NASM Shell]─[x86_64 linux]─[ASM → Hex]
└──╼➤ push rax
[+] Payload size: 1 bytes
[+] Final size of RAW data: 2 bytes
50

[+] Disassembly
   0:	50                   	push   rax

┌─[NASM Shell]─[x86_64 linux]─[ASM → Hex]
└──╼➤ push rax ; push rbx
[+] Payload size: 2 bytes
[+] Final size of RAW data: 4 bytes
5053

[+] Disassembly
   0:	50                   	push   rax
   1:	53                   	push   rbx

pip3 install --upgrade shellcodetester

$ shellcodetester -h

ShellcodeTester v0.X.X by Helvio Junior (M4v3r1ck)
ShellcodeTester is a tool to assembly, compile and test ASM shellcode.
https://github.com/helviojunior/shellcodetester

options:
  -h, --help                      show this help message and exit

General Setting:
  -asm [ASM file name]            Assembly file to be assembled
  -o [output file]                Save output to disk (default: none)

Custom Settings:
  --break-point                   Set software breakpoint (INT3) before shellcode (default: false)
  --bad-chars [bad char list]     List of bad chars to highlight (ex: \x00\x0a, default: \0x00)
  --remove                        Remove bad chars from final binary executable (EXE, ELF and Mach-O). (default: false)
  --cave-size [size]              Code cave size (default: 1024)
  --fill-with-nop                 Fill entire page with NOP (default: false)
  --list                          List all supported output format
  -f [format], --format [format]  Output format (use --list formats to list)
  -v, --verbose                   Shows more options (-h -v). Prints commands and outputs. (default: quiet)

$ nasm_shell -h
options:
  -h, --help                      show this help message and exit

General Setting:
  --mode [mode]                   Operation mode. (default: assembly, permitted: assembly and disassembly)
  --arch [architecture]           Architecture to assembly/disassembly. (default: x86, permitted: x86_64 and x86)
  --platform [platform]           Platform. (permitted: linux, windows and darwin)

Custom Settings:
  --bad-chars [bad char list]     List of bad chars to highlight (ex: \x00\x0a, default: \0x00)
  --list                          List all supported output format
  -f [format], --format [format]  Output format (use --list formats to list)
  -v, --verbose                   Shows more options (-h -v). Prints commands and outputs. (default: quiet)
  -q, --quiet                     Quiet mode, not show banners. (default: false)