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Secure SSH connectivty

Security
  • Hi all,

    I’m curious to understand how you all connect to your servers - hopefully, it’s at the very least using SSH and at the better end of the spectrum, using a key and passphrase combination. For those who are curious to understand why we need a key and passphrase, it’s because without it, your SSH session is still subject to brute force. In addition, you should NEVER allow root to login directly - either at the console physically (if you have a physical server within your reach), or via SSH session.

    In this case, you should be using a normal account to gain access via SSH, then elevating your session using

    su - or su root

    Permitting login as root directly is simply asking for trouble, and will effectively negate your security completely by allowing a complete stranger to bruteforce and then assume control of your server. You should also use a firewall to permit access to SSH via specified and approved IP addresses.

    This is security101 and an industry standard.

    Now it’s confession time on your part… 😄

    The other part of the bargain would be which SSH client you should use. There’s the go-to PUTTY for Windows, or even the command line (which has been greatly simplified in Windows 10/11). However, one I recently started using which is 100% free and extremely powerful is Bitvise

    https://www.bitvise.com/

    Seriously, if you haven’t already got this application in your toolkit, then it’s time to add it.

  • phenomlabundefined phenomlab marked this topic as a regular topic on
  • And, if you want to confess that you’re not using SSH keys, then this is a great guide to change all that, and to take the necessary steps in securing your server…

    https://linuxhint.com/generate-ssh-key-ubuntu/

  • @phenomlab

    Change SSH port is good too

    I use Tabby on Windows, very very good product

    https://tabby.sh

    I search a tutorial for use SSH keys with virtualmin but Ithink it’s not obliged to desactivate root login if you have sh key no ?

    I use crowdsec for bruteforce ssh attack (and other)

    https://www.crowdsec.net

  • @DownPW thanks for the update 👍

  • @DownPW said in Secure SSH connectivty:

    Change SSH port is good too

    Yes, agreed, but easily revealed by a port scanner, and more obfuscation than actual security. Changing the default 22 is of course good security practice but won’t stop a determined attacker.

    @DownPW said in Secure SSH connectivty:

    I use Tabby on Windows, very very good product

    Not tried this, but will definitely take a look

    @DownPW said in Secure SSH connectivty:

    I search a tutorial for use SSH keys with virtualmin but I think it’s not obliged to desactivate root login if you have sh key no ?

    Again, this is more about your attitude to security. It’s a good point, but my preference is to not permit direct root access at all.

    @DownPW said in Secure SSH connectivty:

    I use crowdsec for bruteforce ssh attack (and other)

    Yes, I’m looking at this also.

  • @phenomlab said in Secure SSH connectivty:

    I use Tabby on Windows, very very good product

    Seems this product is ALPHA ?
    f64b1ad2-281b-45d6-8c65-f4200d8f4cd5-image.png

  • @phenomlab

    yep but I use it since several month and I haven’t see any bugs or crash
    In any case, I only use him anymore 🙂

    Tabby offers tabs and a panel system, but also themes, plugins and color palettes to allow you to push the experience to the limit. It can support different shells in the same window, offers completion, has an encrypted container for your passwords, SSH keys and other secrets, and can handle different connection profiles.

    Each tab is persistent (you can restore them if you close one by mistake) and has a notification system, which will let you know if, for example, a process is finished while you are tapping in another tab.

    It’s really a great terminal that will easily replace cmd.exe for Windowsians or your usual terminal. And it can even work in a portable version for those who like to carry their tools on a USB key.

    –> To test it, you can download it, but there is also a web version. Handy for getting an idea.

    https://app.tabby.sh

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    I’ve been using this service for a couple of days now, and it’s made my internet access so much faster. That alone is a plus, and I never thought there would be a contender for Cloudflare in this area.

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    @crazycells good question. Gmail being provided by Google is going to be one of the more secure by default out of the box, although you have to bear in mind that you can have the best security in the world, but that is easily diluted by user decision.

    Obviously, it makes sense to secure all cloud based services with at least 2fa protection, or better still, biometric if available, but email still remains vastly unprotected (unless enforced in the sense of 2fa, which I know Sendgrid do) because of user choice (in the sense that users will always go for the path of least resistance when it comes to security to make their lives easier). The ultimate side effect of taking this route is being vulnerable to credentials theft via phishing attacks and social engineering.

    The same principle would easily apply to Proton Mail, who also (from memory) do not enforce 2fa. Based on this fact, neither product is more secure than the other without one form of additional authentication at least being imposed.

    In terms of direct attack on the servers holding mail accounts themselves, this is a far less common type of attack these days as tricking the user is so much simpler than brute forcing a server where you are very likely to be detected by perimeter security (IDS / IPS etc).

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    @DownPW yeah, I seem to spend a large amount of my time trying to educate people that there’s no silver bullet when it comes to security.

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    @mike-jones Hi Mike,

    There are multiple answers to this, so I’m going to provide some of the most important ones here

    JS is a client side library, so you shouldn’t rely on it solely for validation. Any values collected by JS will need to be passed back to the PHP backend for processing, and will need to be fully sanitised first to ensure that your database is not exposed to SQL injection. In order to pass back those values into PHP, you’ll need to use something like

    <script> var myvalue = $('#id').val(); $(document).ready(function() { $.ajax({ type: "POST", url: "https://myserver/myfile.php?id=" + myvalue, success: function() { $("#targetdiv").load('myfile.php?id=myvalue #targetdiv', function() {}); }, //error: ajaxError }); return false; }); </script>

    Then collect that with PHP via a POST / GET request such as

    <?php $myvalue= $_GET['id']; echo "The value is " . $myvalue; ?>

    Of course, the above is a basic example, but is fully functional. Here, the risk level is low in the sense that you are not attempting to manipulate data, but simply request it. However, this in itself would still be vulnerable to SQL injection attack if the request is not sent as OOP (Object Orientated Programming). Here’s an example of how to get the data safely

    <?php function getid($theid) { global $db; $stmt = $db->prepare("SELECT *FROM data where id = ?"); $stmt->execute([$theid]); while ($result= $stmt->fetch(PDO::FETCH_ASSOC)){ $name = $result['name']; $address = $result['address']; $zip = $result['zip']; } return array( 'name' => $name, 'address' => $address, 'zip' => $zip ); } ?>

    Essentially, using the OOP method, we send placeholders rather than actual values. The job of the function is to check the request and automatically sanitise it to ensure we only return what is being asked for, and nothing else. This prevents typical injections such as “AND 1=1” which of course would land up returning everything which isn’t what you want at all for security reasons.

    When calling the function, you’d simply use

    <?php echo getid($myvalue); ?>

    @mike-jones said in Securing javascript -> PHP mysql calls on Website:

    i am pretty sure the user could just use the path to the php file and just type a web address into the search bar

    This is correct, although with no parameters, no data would be returned. You can actually prevent the PHP script from being called directly using something like

    <?php if(!defined('MyConst')) { die('Direct access not permitted'); } ?>

    then on the pages that you need to include it

    <?php define('MyConst', TRUE); ?>

    Obviously, access requests coming directly are not going via your chosen route, therefore, the connection will die because MyConst does not equal TRUE

    @mike-jones said in Securing javascript -> PHP mysql calls on Website:

    Would it be enough to just check if the number are a number 1-100 and if the drop down is one of the 5 specific words and then just not run the rest of the code if it doesn’t fit one of those perameters?

    In my view, no, as this will expose the PHP file to SQL injection attack without any server side checking.

    Hope this is of some use to start with. Happy to elaborate if you’d like.

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    @justoverclock yes, completely understand that. It’s a haven for criminal gangs and literally everything is on the table. Drugs, weapons, money laundering, cyber attacks for rent, and even murder for hire.

    Nothing it seems is off limits. The dark web is truly a place where the only limitation is the amount you are prepared to spend.