使用程序集执行系统命令(bash)?

问题描述

基本上我正在尝试使用程序集执行命令 /bin/ls，但不幸的是我失败了:

Basically I am trying to execute the command /bin/ls using assembly, but unfortunately I am failing:

SECTION .data
    buf: db "Hello", 5
SECTION .text
global _start

_start:
    xor eax, eax
    mov edx, eax
    push edx
    mov eax, 0x736c2f2f     ; "sl/"
    push eax
    mov eax, 0x6e69622f     ; "nib/"
    push eax
    mov ebx, esp
    push edx
    mov eax, 0x2f
    push eax
    mov ecx, esp
    mov eax, 11
    xor edx, edx
    int 0x80

    mov eax, 1
    int 0x80

但是如果我将 mov eax, 11 更改为 mov eax, 4 并在 xor edx 之后添加 mov edx, 7, edx.它确实打印 /bin/ls

But If I change the mov eax, 11 to mov eax, 4 and add mov edx, 7 after xor edx, edx. It do print /bin/ls

谁能指出我犯的错误?使用 nasm -g -f elf -F dwarf ./shell.asm && 编译代码ld -m elf_i386 -o shell shell.o 而我的弧是 Linux kali 5.2.0-kali2-amd64 #1 SMP Debian 5.2.9-2kali1 (2019-08-22) x86_64 GNU/Linux

Can anyone point the mistake I am making?Compiling the code with nasm -g -f elf -F dwarf ./shell.asm && ld -m elf_i386 -o shell shell.o and my arc is Linux kali 5.2.0-kali2-amd64 #1 SMP Debian 5.2.9-2kali1 (2019-08-22) x86_64 GNU/Linux

推荐答案

发现问题，正如@Jestor 指出的(谢谢)，我需要将执行文件存储在 ebx 和所有参数包括 ecx 中的文件名并将 edx 设置为 null，如下所示:

Found the problem, as pointed by @Jestor (thank you), I needed to store the executing file at ebx and all the arguments including the filename in ecx and set edx to null as below:

SECTION .data
buf: db "./", 0
SECTION .text
global _start

_start:
xor eax, eax
xor edx, edx
push eax
push long 0x736c2f2f    ; "sl/"
push long 0x6e69622f    ; "nib/"
mov ebx, esp
push eax
push byte 0x2f
mov esi, esp

push eax
push esi
push ebx
mov ecx, esp
mov eax, 0x0b
int 0x80

mov eax, 1
int 0x80

在我工作的 shell 之后，ecx 如下所示:

after my working shell, the ecx looked like below:

(gdb) x/50x $ecx
0xffffd370:     0xffffd384      0xffffd37c      0x00000000      0x0000002f
0xffffd380:     0x00000000      0x6e69622f      0x736c2f2f      0x00000000

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