Sono nuovo di shellcoding. Ho scritto codice assembly:
section .text
global _start
_start:
jmp end
start:
;open file
pop ebx ; get address of filename
xor eax,eax
mov [ebx+3], al
mov al,5
xor ecx,ecx
mov edx,777
int 80h
;exit
xor eax,eax
mov al,1
mov ebx,1
int 80h
end:
call start
db "AAAA"
Tuttavia, quando controllo la chiamata di sistema "sys_open" o non utilizzando lo strumento "strace", non mostra alcuna chiamata di sistema relativa all'apertura del file.
Cosa c'è di sbagliato con il mio shellcode ???
"strace" output:
rakesh@rakesh-VirtualBox:~/shellcode$ strace ./a.out
execve("./a.out", ["./a.out"], [/* 21 vars */]) = 0
brk(0) = 0x6cf000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7c53efe000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=62357, ...}) = 0
mmap(NULL, 62357, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f7c53eee000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "7ELFsection .text
global _start
_start:
jmp end
start:
;open file
pop ebx ; get address of filename
xor eax,eax
mov [ebx+3], al
mov al,5
xor ecx,ecx
mov edx,777
int 80h
;exit
xor eax,eax
mov al,1
mov ebx,1
int 80h
end:
call start
db "AAAA"
rakesh@rakesh-VirtualBox:~/shellcode$ strace ./a.out
execve("./a.out", ["./a.out"], [/* 21 vars */]) = 0
brk(0) = 0x6cf000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7c53efe000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=62357, ...}) = 0
mmap(NULL, 62357, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f7c53eee000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "7ELF%pre%%pre%%pre%%pre%%pre%%pre%%pre%%pre%%pre%%pre%>%pre%%pre%%pre%%pre%0%pre%%pre%%pre%%pre%%pre%"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1815224, ...}) = 0
mmap(NULL, 3929304, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f7c5391e000
mprotect(0x7f7c53ad3000, 2097152, PROT_NONE) = 0
mmap(0x7f7c53cd3000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1b5000) = 0x7f7c53cd3000
mmap(0x7f7c53cd9000, 17624, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f7c53cd9000
close(3) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7c53eed000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7c53eec000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7c53eeb000
arch_prctl(ARCH_SET_FS, 0x7f7c53eec700) = 0
mprotect(0x7f7c53cd3000, 16384, PROT_READ) = 0
mprotect(0x600000, 4096, PROT_READ) = 0
mprotect(0x7f7c53f00000, 4096, PROT_READ) = 0
munmap(0x7f7c53eee000, 62357) = 0
fstat(1, {st_mode=03260764276, st_size=140733642434881, ...}) = 3
write(1, "20377%pre%%pre%%pre%%pre%%pre%%pre%%pre%%pre%%pre%%pre%20377%pre%%pre%60377%pre%%pre%"..., 777 <unfinished ... exit status 1>
%pre%%pre%%pre%%pre%%pre%%pre%%pre%%pre%>%pre%%pre%%pre%%pre%0%pre%%pre%%pre%%pre%%pre%"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1815224, ...}) = 0
mmap(NULL, 3929304, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f7c5391e000
mprotect(0x7f7c53ad3000, 2097152, PROT_NONE) = 0
mmap(0x7f7c53cd3000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1b5000) = 0x7f7c53cd3000
mmap(0x7f7c53cd9000, 17624, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f7c53cd9000
close(3) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7c53eed000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7c53eec000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7c53eeb000
arch_prctl(ARCH_SET_FS, 0x7f7c53eec700) = 0
mprotect(0x7f7c53cd3000, 16384, PROT_READ) = 0
mprotect(0x600000, 4096, PROT_READ) = 0
mprotect(0x7f7c53f00000, 4096, PROT_READ) = 0
munmap(0x7f7c53eee000, 62357) = 0
fstat(1, {st_mode=03260764276, st_size=140733642434881, ...}) = 3
write(1, "20377%pre%%pre%%pre%%pre%%pre%%pre%%pre%%pre%%pre%%pre%20377%pre%%pre%60377%pre%%pre%"..., 777 <unfinished ... exit status 1>