> For the complete documentation index, see [llms.txt](https://meowsec.gitbook.io/w1/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://meowsec.gitbook.io/w1/tryhackme/thmw/linux-local-enumeration.md).

# Linux: Local Enumeration

This room from [tryHackMe](https://tryhackme.com/room/lle) describes some technique to enumerate and escalate privilege after getting a shell in a Linux machine. 

Target website shows the way to connect and get a reverse shell: 

![](/files/-Mb1smj1e9skb2QhwGlr)

### Unit 1: tty

Reverse shell - 

* netcat shell can be broken often
* stable shell is needed
* Some commands like  **`su`** and **`ssh`** needs proper terminal to run
* Python one liner for a stable shell: **`python3 -c 'import pty; pty.spawn("/bin/bash")'`**
* Upgrading shell to interactive shell: [blog post](https://blog.ropnop.com/upgrading-simple-shells-to-fully-interactive-ttys)
* Curated list of privesc command: [GTFOBins](https://gtfobins.github.io/)

The command from GTFOBins gives us shell but as we want to execute bash, we need to modify it: **`perl -e 'exec "/bin/sh";'`**

![](/files/-Mb1twP9VtxI6dE1qMw4)

### Unit 1: ssh

SSH - 

* SSH can give us stable reverse connection
* Usually located in **`.ssh`** file
* If I get the private key, **`id_rsa`** :
  * Download it to my own machine
  * Give permission: **`chmod 600`**
  * Connect ssh: **`ssh -i id_rsa [user]@[IP]`**
* If private key isn't there or inaccessible:
  * Generate own ssh key in attacker machine: **`ssh-keygen`**
  * Copy the **`id_rsa.pub`** to the target machine's **`authorized_keys`** file. This file will be inside the **`.ssh`** file
  * Connect ssh from attacker machine using own **`id_rsa`** file

![](/files/-Mb1yM8pX-pBYmcPq7mr)

### Unit 2: Basic enumeration

Quick methodology - 

* get system info: **`uname -a`** 
* User command history can be here: **`.bash_history`**
* These two file contains shell command that run when bash executed: **`.bash_profile`** and **`.bashrc`**
* Check sudo version: **`sudo -v`**
* User list with sudo access: **`sudo -l`**

![](/files/-Mb26bX_e2eAX4Z87BMS)

### Unit 3: /etc

/etc/passwd file - 

* This file contains essential information
* Format of /passwd file - 

![](/files/-Mb29yv-FsPhyy5rQ-9X)

/etc/shadow file -

* This file contains hashed password 

/etc/hosts file - 

* This file assigns hostname to IP address

![](/files/-Mb2BB14XPzCrQ9lVxH_)

### Unit 4: Find command

Find command - 

* Most important switch : **`-type`** and **`-name`**
* Look for interesting log (.log) and configuration (.conf) file. There can be a backup (.bak) file too

Task - 

* Found password in backup file: **`find -type f -name "*.bak" 2>/dev/null`**
* Found flag in a .conf file: **`find -type f -name "*.conf" 2>/dev/null`**

![](/files/-Mb2N-HmjtUc___cjH3H)

### Unit 4: SUID

SUID bit - 

* If this bit is set, anyone can run the file with the owner level access
* Find command: find / -type f -perm -u=s 2>/dev/null
* GTFOBins shows good payload for grep

![](/files/-Mb2Ptqvf0EWl4cL6C_4)

### Unit 5:

SSH tunnelling - 

* Three types of ssh tunnel (with example):
  * Forward tunnel: this will connect from office to home using a ssh tunnel
  * Reverse tunnel: this tunnel will connect from home to office
  * Dynamic tunnel: this will use sock proxy and divert all traffic to specified address
* Explained video: [YouTube](https://youtu.be/AtuAdk4MwWw)

SSH tunnelling **command** - 

* Forward tunnel : map port from remote machine/network to local machine

```
ssh -L $LOCAL_PORT:$REMOTE_IP:$REMOTE_PORT $USER@$SERVER
```

* Reverse tunnel : make local port accessible to remote machine

```
ssh -R $REMOTE_PORT:$LOCAL_IP:$LOCAL_PORT $USER@$SERVER
```


---

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