Shellen

General

Shellen is an interactive shellcoding environment. If you want a handy tool to write shellcodes, then shellen may be your friend. Shellen can also be used as an assembly or disassembly tool.

keystone and capstone engines are used for all of shellen's operations.

Shellen only works on python3. python2 support may appear in the future.

Installing

First, you should install shellen's dependencies:

$ sudo apt-get install cmake python3-dev python3-setuptools

You can install the stable version of shellen using pip3:

$ sudo pip3 install shellen

Or if you already have all required packages (see Requirements):

$ python3 setup.py install

If you have any problems with installing keystone-engine, then you should compile keystone-engine (see the COMPILE.md file in the keystone repository)

How to Run Shellen

After installing shellen and its required packages, you can run shellen by typing the following in your terminal:

$ shellen

You can run shellen's help command to get information about shellen's usage.

Shellen assembles and disassembles instructions, so there are two usage modes: asm and dsm respectively. There are other features which include searching syscall tables and searching for common shellcodes.

Prompt

Shellen has a useful prompt that displays the current mode, OS (operating system for syscalls), and the current mode's chosen architecture. Shellen's prompt looks like this:

L:asm:x86_32 >

You can edit your input like you're typing in a terminal. Also, shellen records your command history (just type your up arrow to see your previous commands).

L is the shortened name of Linux in the prompt. Below listed all other OS names:

L is Linux
W is Windows
M is MacOS

If you want to change OS, then type setos [linux/windows/macos] as follows:

L:asm:x86_32 > setos windows

[+] OS changed to windows.

To change current mode, enter asm or dsm in the prompt.

L:dsm:arm32 > asm

[+] Changed to asm (assembly) mode

L:asm:x86_32 > dsm

[+] Changed to dsm (disassembly) mode

L:dsm:arm32 >

Base Commands

Command	Description
`clear`	Clear the terminal screen. As usual `cls` on Windows or `clear` on *nix systems.
`help`	Show the help message.
`quit,q,exit`	Finish the current session and quit

Assembling

To assemble instuctions, type them and separate them with semicolons as shown here:

L:asm:x86_32 > mov edx, eax; xor eax, eax; inc edx; int 80;
   [+] Bytes count: 7
       Raw bytes:  "\x89\xc2\x31\xc0\x42\xcd\x50"
       Hex string: "89c231c042cd50"

If your assembled bytes contain a null byte, then shellen will tell you about this.

Disassembling

Disassembling is similar to assembling. Instead, type your bytes in the prompt and see the result!

L:dsm:x86_32 > 89c231c042cd50
        0x00080000:     mov     edx, eax
        0x00080002:     xor     eax, eax
        0x00080004:     inc     edx
        0x00080005:     int     0x50

Architectures

asm and dsm modes work for different architectures. To see a list of available architectures for shellen's current mode, type this:

L:dsm:x86_32 > archs
┌────────┬────────┬─────────┬─────────┬────────┐
│        │        │         │         │        │
│ arm32  │ mips32 │ sparc32 │ systemz │ x86_16 │
│ arm64  │ mips64 │ sparc64 │         │ x86_32 │
│ arm_tb │        │         │         │ x86_64 │
└────────┴────────┴─────────┴─────────┴────────┘

If you want to change the current architecture, enter the following:

L:dsm:x86_32 > setarch arm32

[+] Architecture of dsm changed to arm32

Syscalls

When you create a shellcode, you will need syscalls. To lookup syscalls with shellen, type sys and the name of your desired syscall. Shellen will produce a list of syscalls which may contain the syscall you were looking for.

L:asm:x86_32 > sys open

┌────────┬───────┬──────────────────────┬──────────────────────┬──────────────┬──────────────┐
│ name   │ eax   │ ebx                  │ ecx                  │ edx          │ esi          │
├────────┼───────┼──────────────────────┼──────────────────────┼──────────────┼──────────────┤
│ open   │ 0x05  │ const char *filename │ int flags            │ umode_t mode │ -            │
│ openat │ 0x127 │ int dfd              │ const char *filename │ int flags    │ umode_t mode │
└────────┴───────┴──────────────────────┴──────────────────────┴──────────────┴──────────────┘

sys prints a list of possible variants for the provided syscall. The syscall table that shellen searches depends on the chosen architecture and operating system (OS). In this case, the architecture is x86_32 and the OS is Linux.

Common Shellcodes

Shellen can show you a list of common shellcodes depending on your keyword. Shellen's keyword lookup uses shell-storm.org's API (thanks to the author!) and can be used like this:

L:asm:x86_32 > shell <keyword> <count>

Note, the count parameter isn't required. There is an image of shell <keyword> <count>'s output in the Pictures section.

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