# ret2libc

## Theory

If the function is dynamically linked, it is possible to utilize gadgets from libc. For example, if the binary calls `puts()`, we can control EIP/RIP and then leak an address from GOT. If `libc.so` is given, just attach it and find the offset; otherwise, use libc database to search the offset. We compute the libc base address:

```
libc_base_address = leaked_address_from_GOT - offset
```

Then we compute the system() address and "/bin/sh" address:

```
system_address = libc_base_address + offset
bin_sh_address = libc_base_address + offset
```

In the end we call `system("/bin/sh")`. Read this writeup to learn more:

{% embed url="<https://www.ctfwriteup.com/pwn/jarvis-oj-pwn-xman-series>" %}
Jarvis OJ Pwn Xman Series - ctfwriteup.com
{% endembed %}

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