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**SSH or Secure Shell or Secure Socket Shell,** is a network protocol that gives users a **secure way to access a computer over an unsecured network.**
* [Dropbear](https://matt.ucc.asn.au/dropbear/dropbear.html) – SSH implementation for environments with low memory and processor resources, shipped in OpenWrt
* [PuTTY](https://www.chiark.greenend.org.uk/\~sgtatham/putty/) – SSH implementation for Windows, the client is commonly used but the use of the server is rarer
* [libssh](https://www.libssh.org) – multiplatform C library implementing the SSHv2 protocol with bindings in [Python](https://github.com/ParallelSSH/ssh-python), [Perl](https://github.com/garnier-quentin/perl-libssh/) and [R](https://github.com/ropensci/ssh); it’s used by KDE for sftp and by GitHub for the git SSH infrastructure
* [wolfSSH](https://www.wolfssl.com/products/wolfssh/) – SSHv2 server library written in ANSI C and targeted for embedded, RTOS, and resource-constrained environments
* [Apache MINA SSHD](https://mina.apache.org/sshd-project/index.html) – Apache SSHD java library is based on Apache MINA
[https://github.com/jtesta/ssh-audit](https://github.com/jtesta/ssh-audit) is an updated fork from [https://github.com/arthepsy/ssh-audit/](https://github.com/arthepsy/ssh-audit/)
**Features:**
* SSH1 and SSH2 protocol server support;
* analyze SSH client configuration;
* grab banner, recognize device or software and operating system, detect compression;
* gather key-exchange, host-key, encryption and message authentication code algorithms;
Some common ssh credentials [here ](https://github.com/danielmiessler/SecLists/blob/master/Passwords/Default-Credentials/ssh-betterdefaultpasslist.txt)and [here](https://github.com/danielmiessler/SecLists/blob/master/Passwords/Common-Credentials/top-20-common-SSH-passwords.txt) and below.
Or use `ssh-keybrute.py` (native python3, lightweight and has legacy algorithms enabled): [snowdroppe/ssh-keybrute](https://github.com/snowdroppe/ssh-keybrute).
Some systems have known flaws in the random seed used to generate cryptographic material. This can result in a dramatically reduced keyspace which can be bruteforced. Pre-generated sets of keys generated on Debian systems affected by weak PRNG are available here: [g0tmi1k/debian-ssh](https://github.com/g0tmi1k/debian-ssh).
If you are in the local network as the victim which is going to connect to the SSH server using username and password you could try to **perform a MitM attack to steal those credentials:**
**Attack path:**
* user traffic is redirected to the attacking machine
* the attacker monitors attempts to connect to the SSH server and redirects them to its SSH server
* the attacker's SSH server is configured, firstly, to log all entered data, including the user's password, and, secondly, send commands to the legitimate SSH server to which the user wants to connect, to execute them, and then return the results to the legitimate user
In order to capture perform the actual MitM you could use techniques like ARP spoofing, DNS spoofin or others described in the [**Network Spoofing attacks**](../generic-methodologies-and-resources/pentesting-network/#spoofing).
By default most SSH server implementation will allow root login, it is advised to disable it because if the credentials of this accounts leaks, attackers will get administrative privileges directly and this will also allow attackers to conduct bruteforce attacks on this account.
Another common SSH misconfiguration is often seen in SFTP configuration. Most of the time when creating a SFTP server the administrator want users to have a SFTP access to share files but not to get a remote shell on the machine. So they think that creating a user, attributing him a placeholder shell (like `/usr/bin/nologin` or `/usr/bin/false`) and chrooting him in a jail is enough to avoid a shell access or abuse on the whole file system. But they are wrong, **a user can ask to execute a command right after authentication before it’s default command or shell is executed**. So to bypass the placeholder shell that will deny shell access, one only has to ask to execute a command (eg. `/bin/bash`) before, just by doing:
This configuration will allow only SFTP: disabling shell access by forcing the start command and disabling TTY access but also disabling all kind of port forwarding or tunneling.
The **sftp** have the command "**symlink**". Therefor, if you have **writable rights** in some folder, you can create **symlinks** of **other folders/files**. As you are probably **trapped** inside a chroot this **won't be specially useful** for you, but, if you can **access** the created **symlink** from a **no-chroot****service** (for example, if you can access the symlink from the web), you could **open the symlinked files through the web**.
On high security environment it’s a common practice to enable only key-based or two factor authentication rather than the simple factor password based authentication. But often the stronger authentication methods are enabled without disabling the weaker ones. A frequent case is enabling `publickey` on openSSH configuration and setting it as the default method but not disabling `password`. So by using the verbose mode of the SSH client an attacker can see that a weaker method is enabled:
debug1: Authentications that can continue: publickey,password,keyboard-interactive
```
For example if an authentication failure limit is set and you never get the chance to reach the password method, you can use the `PreferredAuthentications` option to force to use this method.
* You can find interesting guides on how to harden SSH in [https://www.ssh-audit.com/hardening\_guides.html](https://www.ssh-audit.com/hardening\_guides.html)
* Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
* **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.**
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