## Challenge Info

This challenge is a HackTheBox like box, so we are given an ip address to scan `` and hack our way into the box , this writeups cover the challenges from Htbx02-> Htbx06 as they are the same box.

## Writeup summary

- initial enumeration
- No Sql injection
- XXE in /admin
- Zip Slip in /home
- Server enumeration

### Initial enumeration

As we always start with any Htb box we will launch the `nmap` scan on the ip address `nmap -sC -sV -oA src/` so `-sC` is for using default nmap scripts , `-sV` for enumerating services versions , `-oA` is for output ALL format and specify the directory `src` , NOTICE: you may be adding `-Pn` if you have an error wait for some time and here is the result :

![nmap result ](src/nmap_result.png)

In Summary , we have a web application running NodeJs in port `3000` ,an ssh port `22` and the `53` port for dns , also we should thank the `http.robots` nmap script now we have an extra information in the `robots.txt` saying there is a `/admin` route in the web application . So we will start by checking the web application at `` :

It's a simple login form we tried dummy credentials like `admin:admin` or `admin:password` we got `No user with username: admin and password: admin.` so it actually doing the login its not just fake , first thing we tried was a sql injection attack so we tried to check if it is filtering our input by passing as credentials `';-#$()` and we got this `No user with username: ';-#$() and password: ';-#$()` , that means it is not filtering any inputs and may be vulnerable to sql injection attacks , so we tried different payloads like `1 or 1=1` , `1' or 1=1 --` but we had no result it keeps sending us our input , and at that moment we remembered we have a nodejs application and of course when you hear nodejs first db it came out in your mind is mongodb which is a nosql db so maybe it is a nosql injection attack lets test it out with Burpsuite.

### No Sql injection

By intercepting the request in burpsuite we can now add our payload of nosqli we used the payloads from [PayloadAllTheThings]([https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/NoSQL%20Injection](https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/NoSQL Injection)) which is a great source for payloads , we tried the first payload `username[$ne]=toto&password[$ne]=toto` which means that the mongodb will interpret this as `username!=toto&&password&&toto` which gives true .

Annnddd we got redirection so nosqlinjection did work and this website is vulnerable to nosqlinjection , next thing to do when you have a vulnerable website to nosql injection is to leak the credentials and this is possible by using the regex ability in mongodb , by sending this payload `password[$regex]=m.*` mongodb will interpret this as username start with m in regex `^m.*` so to extract information we have to make a script that bruteforce all the caracteres each at time and here is our [script](src/nosqlin.py) , wait for some time ..... and finally the creds for admin are `admin:d2f312ed7ed60ea79e3ab3d16ab2f8db` after logging with we got redirected to /home with a zip upload page

let's just check the /admin page first we got a zip extractor and by checking the source code we found the flag for **Htbx02** and here is it `csictf{n0t_4ll_1nj3ct10n5_4re_SQLi}`

### XXE in /admin

by trying different payloads for each type we knew that only the json and xml were accepted in other types we receive :

`This type is not supported right now. Sorry for the inconvenience.` so first though when we see xml we try the xml external entity `XXE` it will allow us to read files from the server so we used some payloads from [PayloadAllTheThings]([https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/XXE%20Injection](https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/XXE Injection)) and we tried to read the /etc/passwd by using this payload we got it printed :

So in response we got the regular `/etc/passwd` we can notice the users `csictf`, `administrator` and ... wait a minute what is that !! we found a link in the /etc/passwd to a [github gist](https://gist.github.com/sivel/c68f601137ef9063efd7) , after reading that gist we understand it is about structuring the ssh keys for better ssh keys management , so basically for this key management to work we have to create a bash script at `/usr/local/bin/` and add our configuration to it , than we need to modify the ssh configuration to point to this bash script , so as an attacker we need to get ssh keys so we tried to read the ssh configuration with xxe `/etc/ssh/sshd_config` after a deep look into the file we saw a flag and it was for **HTBX05** `csictf{cu5t0m_4uth0rizat10n}` and after reading the`/user/local/bin/userkeys` we knew that ssh keys must be put in `/home/administrator/uploads/keys/`

### Zip Slip in /home

after getting that flag we though we are done with the xxe attack and we must have a reverse shell or ssh keys so we tried read ssh keys from different folders but we found anything so we decided to go back to the `/home` page and scan if it has some vulnerability , so we tried to upload dummy zip it said that `zip too large` so we just put a txt dummy file in it and it returned `{success:true}` that's all , we tried to access the file we uploaded trying different routes like /file.txt , /uploads/file.txt ... but didn't found anything after a search about zip upload vulnerabilities we found a vulnerability called **ZIP SLIP** which exploit zip extraction and allow us to override files when extracting the zip .(some of the great resources to read about it are [LiveOverflow video](https://www.youtube.com/watch?v=Ry_yb5Oipq0) or [Official website](https://snyk.io/research/zip-slip-vulnerability) ), now let's create our zip exploit as this (Notice use `/home/administrator/uploads/keys/` as location to ssh public key )

first create the `administrator/uploads/keys` and put ssh keys in it :

sudo mkdir -p administrator/uploads/keys
cd administrator/uploads/keys
sudo ssh-keygen
# pass /home/administrator/uploads/keys/id_rsa as path

then create our zip (NOTICE we must rename id_rsa.pub to `authorized_keys` because that's what the ssh server accept):

sudo mv id_rsa.pub authorized_keys
sudo zip exploit.zip ../../../../../../../../../../../home/administrator/uploads/keys/authorized_keys

we added multiple `..` because we don't know the exact path the zip will be extracted after uploading it we got `{"success":true}` let's try to connect via ssh private key

sudo ssh -i id_rsa [email protected]

we got a shell :tada: :tada: , doing an `ls ` we dound `flag.txt` and by reading it we got a flag `csictf{w3lc0m3_t0_th3_s3rv3r}` for **HTBx03**

### Server enumeration

let's start by enumerating the /home/csictf folder

csictf@instance-3:~$ ls -la
total 24
drwxr-xr-x 2 root root 4096 Jul 20 13:12 .
drwxr-xr-x 9 root root 4096 Jul 20 12:46 ..
-rw-r--r-- 1 root root 220 Jul 20 12:40 .bash_logout
-rw-r--r-- 1 root root 3771 Jul 20 12:40 .bashrc
-rw-r--r-- 1 root root 807 Jul 20 12:40 .profile
-rw-r--r-- 1 root root 30 Jul 20 13:12 flag.txt

nothing very useful here we checked the `/home` for other home directory all were empty except for the `administrator` we found two folders `uploads` where the zip where puts and `website` that contains the code for the web app , after listing and viewing different folders and files we saw a file in `website/models/db.js` that contain a flag :

csictf@instance-3:/home/administrator/website/models$ cat db.js
const mongoose = require('mongoose');

mongoose.Promise = global.Promise;

// csictf{exp0s3d_sec23ts}
mongoose.connect('mongodb://web:[email protected]:27017/HTBDB', {
useNewUrlParser: true,
useCreateIndex: true,
useUnifiedTopology: true,

so the flag `csictf{exp0s3d_sec23ts}` is for the challenge **HTBx06** and we have a url for connecting to mongodb with the creds in it so we tried to dump the db with `mongodump`

mongodump --uri='mongodb://web:[email protected]:27017/HTBDB'

and we got a list of mongodb collection . after scanning the result we found the last flag for **HTBx04** in the collection stuff here is the flag `csictf{m0ng0_c0llect10ns_yay}` and that conclude this series of challenge .

Original writeup (https://github.com/team0se7en/CTF-Writeups/tree/master/csictf2020/linux/Htb).