Basic Auth Generator Using Ssh Key
Set up your first SSH keys
- Creating SSH-Keys using Terminal Keys Generator is highly recommended before deploying your VPS instance, hence, SSH-Keys Authentication will be used instead of Password Authentication. SSH-Keys are part of the OpenSSH package which provides secure and encrypted communication between SSH Client (Admin Station) and the OpenSSH Server (VPS). SSH-Keys make it possible to have Multifactor.
- PuTTY Key Generator Tool Having downloaded and launched the PuTTY Key Generator tool we first have to select what type of key to generate along with a key size. SSH-2 RSA is strongly recommended as the key type. In terms of key size it is important to understand that a larger key provides ‘extra’ security at the cost of processing overhead.
Use SSH keys for authentication when you are connecting to your server, or even between your servers. They can greatly simplify and increase the security of your login process. When keys are implemented correctly they provide a secure, fast, and easy way of accessing your cloud server.
Follow our guide and learn how to set up your first SSH keys for authentication using OpenSSH or PuTTYTray.
Before using ssh, MobaXterm requires a persistent home directory. Go to Settings and set the persistent home directory. First step is to generate the ssh key, therefore open a local terminal and generate a key (rsa) with this command.
Preparing your server
To add an SSH key pair, first, create a hidden folder to your user account home directory on your cloud server with the following command.
Then restrict the permissions to that directory to just yourself with the command below.
This creates a secure location for you to save your SSH keys for authentication. However, note that since the keys are stored in your user home directory, every user that wishes to connect using SSH keys for authentication has to repeat these steps on their own profile.
Using OpenSSH to generate a key pair
Now continue on your own computer if you are using Linux or any other OS that has OpenSSH. PuTTY users should skip to the next section.
1. Generate a new key pair in a terminal with the next command
The key generator will ask for location and file name to which the key is saved to. Enter a new name or use the default by pressing enter.
2. (Optional) Create a passphrase for the key when prompted
This is a simple password that will protect your private key should someone be able to get their hands on it. Enter the password you wish or continue without a password. Press enter twice. Note that some automation tools might not be able to unlock passphrase-protected private keys.
3. Copy the public half of the key pair to your cloud server using the following command
Replace the user and server with your username and the server address you wish to use the key authentication on.
This also assumes you saved the key pair using the default file name and location. If not, just replace the key path ~/.ssh/id_rsa.pub above with your own key name.
Enter your user account password for that SSH server when prompted.
You can now authenticate to your server with the key pair, but at the moment you would need to enter the passphrase every time you connect.
4. (Optional) Set up SSH Agent to store the keys to avoid having to re-enter passphrase at every login
Enter the following commands to start the agent and add the private SSH key.
Type in your key’s current passphrase when asked. If you saved the private key somewhere other than the default location and name, you’ll have to specify it when adding the key.
Afterwards, you can connect to your cloud server using the keys for authentication, and only having to unlock the key by repeating the last 2 steps once after every computer restart.
Using PuTTYTray to generate a key pair
If you are running Windows and PuTTYTray for SSH, you can use the built-in key generator from PuTTY to create a new key pair.
1. Click the Keygen button at the bottom of the PuTTY Configuration window to get started.
Then in the Key Generator window, check that the Type of key to generate at the bottom is set to SSH-2 RSA. The older SSH-1 was the first version on the standard but is now generally considered obsolete. Most modern servers and clients support SSH-2.
/automatically-generate-aws-key-everyday.html. 2. Click the Generate button to begin.
3. Keep moving your mouse over the blank area in any manner to help generate randomness for a few moments until the progress is complete.
With the keys finished, PuTTY will show the relative information about the pair along with the public key for easier copying.
4. (Optional) Enter a key passphrase in the 2 empty fields for the added security before continuing. The passphrase will protect your key from unauthorized use should someone be able to copy it. However, some automation tools might not be able to unlock passphrase-protected private keys.
5. Click the Save private key button and store it somewhere safe. Generally anywhere in your user directory is fine as long as your PC is password protected. Before closing the keygen, you may want to copy the public key to your clipboard, but you can always get it later as well.
Now that you have a new key saved on your computer, you’ll need to import it into the PuTTY key agent.
6. Click the Agent button to open the key manager in the PuTTY Configuration window.
7. Click Add Key button in the Key List, then browse to the location you saved the private key, select it and click Open.
Enter your key passphrase if asked.
This will import the key to your PuTTY client, but you still need to copy the public key over to your server.
8. Open an SSH connection to your cloud server and go to the SSH key directory.
9. Open or create the default file OpenSSH looks for public keys called authorized_keys.
10. Paste the public key into the file by simply right-clicking the SSH client window. Make sure the key goes on a single line for OpenSSH to be able to read it.
When you’ve copied the public key over to the authorized keys list, save the file and exit the editor. You can now test the public key authentication by logging in to your server again. You should not get asked for your password, but instead logged straight in with the key. If it’s not working, check that your private key is unlocked at your SSH Agent and try again.
Turn off password authentication
With SSH key authentication configured and tested, you can disable password authentication for SSH all together to prevent brute-forcing. When logged in to your cloud server.
1. Open the SSH configuration file with the following command.
2. Set the password authentication to no to disable clear text passwords.
3. Check that public key authentication is enabled, just to be safe and not get locked out from your server. If you do find yourself unable to log in with SSH, you can always use the Web terminal at your UpCloud control panel.
Then save and exit the editor.
4. Restart the SSH service to apply the changes by using the command below.
With that done your cloud server is now another step along towards security. Malicious attempts to connect to your server will results in authentication rejection, as plain passwords are not allowed, and brute-forcing an RSA key is practically impossible.
Conclusions
Remember to always keep your private keys safe. You can use the same key from multiple computers if you wish, or generate new ones on each client connecting to your cloud server for added security. Each user should generate their own key pair and passphrase for secure access control. With proper management, even in case one of the private keys gets compromised you won’t have to replace them all.
Previous Contents Index Next
- Chapter 8: Using public keys for SSH authentication
- 8.2 Using PuTTYgen, the PuTTY key generator
8.1 Public key authentication - an introduction
Public key authentication is an alternative means of identifying yourself to a login server, instead of typing a password. It is more secure and more flexible, but more difficult to set up.
In conventional password authentication, you prove you are who you claim to be by proving that you know the correct password. The only way to prove you know the password is to tell the server what you think the password is. This means that if the server has been hacked, or spoofed (see section 2.2), an attacker can learn your password.
Public key authentication solves this problem. You generate a key pair, consisting of a public key (which everybody is allowed to know) and a private key (which you keep secret and do not give to anybody). The private key is able to generate signatures. A signature created using your private key cannot be forged by anybody who does not have that key; but anybody who has your public key can verify that a particular signature is genuine.
So you generate a key pair on your own computer, and you copy the public key to the server. Then, when the server asks you to prove who you are, PuTTY can generate a signature using your private key. The server can verify that signature (since it has your public key) and allow you to log in. Now if the server is hacked or spoofed, the attacker does not gain your private key or password; they only gain one signature. And signatures cannot be re-used, so they have gained nothing.
There is a problem with this: if your private key is stored unprotected on your own computer, then anybody who gains access to that will be able to generate signatures as if they were you. So they will be able to log in to your server under your account. For this reason, your private key is usually encrypted when it is stored on your local machine, using a passphrase of your choice. In order to generate a signature, PuTTY must decrypt the key, so you have to type your passphrase.
This can make public-key authentication less convenient than password authentication: every time you log in to the server, instead of typing a short password, you have to type a longer passphrase. One solution to this is to use an authentication agent, a separate program which holds decrypted private keys and generates signatures on request. PuTTY's authentication agent is called Pageant. When you begin a Windows session, you start Pageant and load your private key into it (typing your passphrase once). For the rest of your session, you can start PuTTY any number of times and Pageant will automatically generate signatures without you having to do anything. When you close your Windows session, Pageant shuts down, without ever having stored your decrypted private key on disk. Many people feel this is a good compromise between security and convenience. See chapter 9 for further details.
There is more than one public-key algorithm available. The most common is RSA, but others exist, notably DSA (otherwise known as DSS), the USA's federal Digital Signature Standard. The key types supported by PuTTY are described in section 8.2.2.
8.2 Using PuTTYgen, the PuTTY key generator
PuTTYgen is a key generator. It generates pairs of public and private keys to be used with PuTTY, PSCP, and Plink, as well as the PuTTY authentication agent, Pageant (see chapter 9). PuTTYgen generates RSA and DSA keys.
When you run PuTTYgen you will see a window where you have two choices: ‘Generate’, to generate a new public/private key pair, or ‘Load’ to load in an existing private key.
8.2.1 Generating a new key
This is a general outline of the procedure for generating a new key pair. The following sections describe the process in more detail.
- First, you need to select which type of key you want to generate, and also select the strength of the key. This is described in more detail in section 8.2.2 and section 8.2.3.
- Then press the ‘Generate’ button, to actually generate the key. Section 8.2.4 describes this step.
- Once you have generated the key, select a comment field (section 8.2.6) and a passphrase (section 8.2.7).
- Now you're ready to save the private key to disk; press the ‘Save private key’ button. (See section 8.2.8).
Your key pair is now ready for use. You may also want to copy the public key to your server, either by copying it out of the ‘Public key for pasting into authorized_keys file’ box (see section 8.2.10), or by using the ‘Save public key’ button (section 8.2.9). However, you don't need to do this immediately; if you want, you can load the private key back into PuTTYgen later (see section 8.2.11) and the public key will be available for copying and pasting again.
Section 8.3 describes the typical process of configuring PuTTY to attempt public-key authentication, and configuring your SSH server to accept it.
8.2.2 Selecting the type of key
Before generating a key pair using PuTTYgen, you need to select which type of key you need. PuTTYgen currently supports three types of key:
- An RSA key for use with the SSH-1 protocol.
- An RSA key for use with the SSH-2 protocol.
- A DSA key for use with the SSH-2 protocol.
The SSH-1 protocol only supports RSA keys; if you will be connecting using the SSH-1 protocol, you must select the first key type or your key will be completely useless.
The SSH-2 protocol supports more than one key type. The two types supported by PuTTY are RSA and DSA.
The PuTTY developers strongly recommend you use RSA. DSA has an intrinsic weakness which makes it very easy to create a signature which contains enough information to give away the private key! This would allow an attacker to pretend to be you for any number of future sessions. PuTTY's implementation has taken very careful precautions to avoid this weakness, but we cannot be 100% certain we have managed it, and if you have the choice we strongly recommend using RSA keys instead.
If you really need to connect to an SSH server which only supports DSA, then you probably have no choice but to use DSA. If you do use DSA, we recommend you do not use the same key to authenticate with more than one server.
8.2.3 Selecting the size (strength) of the key
The ‘Number of bits’ input box allows you to choose the strength of the key PuTTYgen will generate.
Currently 1024 bits should be sufficient for most purposes.
8.2.4 The ‘Generate’ button
Once you have chosen the type of key you want, and the strength of the key, press the ‘Generate’ button and PuTTYgen will begin the process of actually generating the key.
First, a progress bar will appear and PuTTYgen will ask you to move the mouse around to generate randomness. Wave the mouse in circles over the blank area in the PuTTYgen window, and the progress bar will gradually fill up as PuTTYgen collects enough randomness. You don't need to wave the mouse in particularly imaginative patterns (although it can't hurt); PuTTYgen will collect enough randomness just from the fine detail of exactly how far the mouse has moved each time Windows samples its position.
When the progress bar reaches the end, PuTTYgen will begin creating the key. The progress bar will reset to the start, and gradually move up again to track the progress of the key generation. It will not move evenly, and may occasionally slow down to a stop; this is unfortunately unavoidable, because key generation is a random process and it is impossible to reliably predict how long it will take.
When the key generation is complete, a new set of controls will appear in the window to indicate this.
8.2.5 The ‘Key fingerprint’ box
The ‘Key fingerprint’ box shows you a fingerprint value for the generated key. This is derived cryptographically from the public key value, so it doesn't need to be kept secret.
The fingerprint value is intended to be cryptographically secure, in the sense that it is computationally infeasible for someone to invent a second key with the same fingerprint, or to find a key with a particular fingerprint. So some utilities, such as the Pageant key list box (see section 9.2.1) and the Unix ssh-add utility, will list key fingerprints rather than the whole public key.
8.2.6 Setting a comment for your key
If you have more than one key and use them for different purposes, you don't need to memorise the key fingerprints in order to tell them apart. PuTTYgen allows you to enter a comment for your key, which will be displayed whenever PuTTY or Pageant asks you for the passphrase.
The default comment format, if you don't specify one, contains the key type and the date of generation, such as rsa-key-20011212. Another commonly used approach is to use your name and the name of the computer the key will be used on, such as simon@simons-pc.
To alter the key comment, just type your comment text into the ‘Key comment’ box before saving the private key. If you want to change the comment later, you can load the private key back into PuTTYgen, change the comment, and save it again.
8.2.7 Setting a passphrase for your key
The ‘Key passphrase’ and ‘Confirm passphrase’ boxes allow you to choose a passphrase for your key. The passphrase will be used to encrypt the key on disk, so you will not be able to use the key without first entering the passphrase.
When you save the key, PuTTYgen will check that the ‘Key passphrase’ and ‘Confirm passphrase’ boxes both contain exactly the same passphrase, and will refuse to save the key otherwise.
If you leave the passphrase fields blank, the key will be saved unencrypted. You should not do this without good reason; if you do, your private key file on disk will be all an attacker needs to gain access to any machine configured to accept that key. If you want to be able to log in without having to type a passphrase every time, you should consider using Pageant (chapter 9) so that your decrypted key is only held in memory rather than on disk.
Under special circumstances you may genuinely need to use a key with no passphrase; for example, if you need to run an automated batch script that needs to make an SSH connection, you can't be there to type the passphrase. In this case we recommend you generate a special key for each specific batch script (or whatever) that needs one, and on the server side you should arrange that each key is restricted so that it can only be used for that specific purpose. The documentation for your SSH server should explain how to do this (it will probably vary between servers).
Choosing a good passphrase is difficult. Just as you shouldn't use a dictionary word as a password because it's easy for an attacker to run through a whole dictionary, you should not use a song lyric, quotation or other well-known sentence as a passphrase. DiceWare (www.diceware.com) recommends using at least five words each generated randomly by rolling five dice, which gives over 2^64 possible passphrases and is probably not a bad scheme. If you want your passphrase to make grammatical sense, this cuts down the possibilities a lot and you should use a longer one as a result.
Do not forget your passphrase. There is no way to recover it.
8.2.8 Saving your private key to a disk file
Once you have generated a key, set a comment field and set a passphrase, you are ready to save your private key to disk.
Press the ‘Save private key’ button. PuTTYgen will put up a dialog box asking you where to save the file. Select a directory, type in a file name, and press ‘Save’.
This file is in PuTTY's native format (*.PPK); it is the one you will need to tell PuTTY to use for authentication (see section 4.21.8) or tell Pageant to load (see section 9.2.2).
8.2.9 Saving your public key to a disk file
RFC 4716 specifies a standard format for storing SSH-2 public keys on disk. Some SSH servers (such as ssh.com's) require a public key in this format in order to accept authentication with the corresponding private key. (Others, such as OpenSSH, use a different format; see section 8.2.10.)
To save your public key in the SSH-2 standard format, press the ‘Save public key’ button in PuTTYgen. PuTTYgen will put up a dialog box asking you where to save the file. Select a directory, type in a file name, and press ‘Save’.
You will then probably want to copy the public key file to your SSH server machine. See section 8.3 for general instructions on configuring public-key authentication once you have generated a key.
If you use this option with an SSH-1 key, the file PuTTYgen saves will contain exactly the same text that appears in the ‘Public key for pasting’ box. This is the only existing standard for SSH-1 public keys.
8.2.10 ‘Public key for pasting into authorized_keys file’
All SSH-1 servers require your public key to be given to it in a one-line format before it will accept authentication with your private key. The OpenSSH server also requires this for SSH-2.
The ‘Public key for pasting into authorized_keys file’ gives the public-key data in the correct one-line format. Typically you will want to select the entire contents of the box using the mouse, press Ctrl+C to copy it to the clipboard, and then paste the data into a PuTTY session which is already connected to the server.
See section 8.3 for general instructions on configuring public-key authentication once you have generated a key.
8.2.11 Reloading a private key
PuTTYgen allows you to load an existing private key file into memory. If you do this, you can then change the passphrase and comment before saving it again; you can also make extra copies of the public key.
To load an existing key, press the ‘Load’ button. PuTTYgen will put up a dialog box where you can browse around the file system and find your key file. Once you select the file, PuTTYgen will ask you for a passphrase (if necessary) and will then display the key details in the same way as if it had just generated the key.
If you use the Load command to load a foreign key format, it will work, but you will see a message box warning you that the key you have loaded is not a PuTTY native key. See section 8.2.12 for information about importing foreign key formats.
8.2.12 Dealing with private keys in other formats
Most SSH-1 clients use a standard format for storing private keys on disk. PuTTY uses this format as well; so if you have generated an SSH-1 private key using OpenSSH or ssh.com's client, you can use it with PuTTY, and vice versa.
However, SSH-2 private keys have no standard format. OpenSSH and ssh.com have different formats, and PuTTY's is different again. So a key generated with one client cannot immediately be used with another.
Using the ‘Import’ command from the ‘Conversions’ menu, PuTTYgen can load SSH-2 private keys in OpenSSH's format and ssh.com's format. Once you have loaded one of these key types, you can then save it back out as a PuTTY-format key (*.PPK) so that you can use it with the PuTTY suite. The passphrase will be unchanged by this process (unless you deliberately change it). You may want to change the key comment before you save the key, since OpenSSH's SSH-2 key format contains no space for a comment and ssh.com's default comment format is long and verbose.
PuTTYgen can also export private keys in OpenSSH format and in ssh.com format. To do so, select one of the ‘Export’ options from the ‘Conversions’ menu. Exporting a key works exactly like saving it (see section 8.2.8) - you need to have typed your passphrase in beforehand, and you will be warned if you are about to save a key without a passphrase.
Note that since only SSH-2 keys come in different formats, the export options are not available if you have generated an SSH-1 key.
8.3 Getting ready for public key authentication
Connect to your SSH server using PuTTY with the SSH protocol. When the connection succeeds you will be prompted for your user name and password to login. Once logged in, you must configure the server to accept your public key for authentication:
Auth Key Generator
- If your server is using the SSH-1 protocol, you should change into the
.sshdirectory and open the fileauthorized_keyswith your favourite editor. (You may have to create this file if this is the first key you have put in it). Then switch to the PuTTYgen window, select all of the text in the ‘Public key for pasting into authorized_keys file’ box (see section 8.2.10), and copy it to the clipboard (Ctrl+C). Then, switch back to the PuTTY window and insert the data into the open file, making sure it ends up all on one line. Save the file. - If your server is OpenSSH and is using the SSH-2 protocol, you should follow the same instructions, except that in earlier versions of OpenSSH 2 the file might be called
authorized_keys2. (In modern versions the sameauthorized_keysfile is used for both SSH-1 and SSH-2 keys.) - If your server is
ssh.com's product and is using SSH-2, you need to save a public key file from PuTTYgen (see section 8.2.9), and copy that into the.ssh2directory on the server. Then you should go into that.ssh2directory, and edit (or create) a file calledauthorization. In this file you should put a line likeKey mykey.pub, withmykey.pubreplaced by the name of your key file. - For other SSH server software, you should refer to the manual for that server.
You may also need to ensure that your home directory, your .ssh directory, and any other files involved (such as authorized_keys, authorized_keys2 or authorization) are not group-writable or world-writable. You can typically do this by using a command such as
Your server should now be configured to accept authentication using your private key. Now you need to configure PuTTY to attempt authentication using your private key. You can do this in any of three ways:
- Select the private key in PuTTY's configuration. See section 4.21.8 for details.
- Specify the key file on the command line with the
-ioption. See section 3.8.3.18 for details. - Load the private key into Pageant (see chapter 9). In this case PuTTY will automatically try to use it for authentication if it can.
If you want to provide feedback on this manual or on the PuTTY tools themselves, see the Feedback page.