• Generate Git Ssh Key Ubuntu 10
• Generate Git Ssh Key Ubuntu Windows 10
• Git

Parent page: Internet and Networking >> SSH

Public key authentication is more secure than password authentication. This is particularly important if the computer is visible on the internet. If you don't think it's important, try logging the login attempts you get for the next week. My computer - a perfectly ordinary desktop PC - had over 4,000 attempts to guess my password and almost 2,500 break-in attempts in the last week alone.

With public key authentication, the authenticating entity has a public key and a private key. Each key is a large number with special mathematical properties. The private key is kept on the computer you log in from, while the public key is stored on the .ssh/authorized_keys file on all the computers you want to log in to. When you log in to a computer, the SSH server uses the public key to 'lock' messages in a way that can only be 'unlocked' by your private key - this means that even the most resourceful attacker can't snoop on, or interfere with, your session. As an extra security measure, most SSH programs store the private key in a passphrase-protected format, so that if your computer is stolen or broken in to, you should have enough time to disable your old public key before they break the passphrase and start using your key. Wikipedia has a more detailed explanation of how keys work.

Apr 12, 2018 Step 1 — Create the RSA Key Pair. The first step is to create a key pair on the client machine (usually your computer): ssh-keygen By default ssh-keygen will create a 2048-bit RSA key pair, which is secure enough for most use cases (you may optionally pass in the -b 4096 flag to create a larger 4096-bit key). After entering the command, you should see the following output. Jun 22, 2012 SSH keys provide a more secure way of logging into a virtual private server with SSH than using a password alone. With SSH keys, users can log into a server without a password. This tutorial explains how to generate, use, and upload an SSH Key Pair.

Public key authentication is a much better solution than passwords for most people. In fact, if you don't mind leaving a private key unprotected on your hard disk, you can even use keys to do secure automatic log-ins - as part of a network backup, for example. Different SSH programs generate public keys in different ways, but they all generate public keys in a similar format:

Key-based authentication is the most secure of several modes of authentication usable with OpenSSH, such as plain password and Kerberos tickets. Key-based authentication has several advantages over password authentication, for example the key values are significantly more difficult to brute-force, or guess than plain passwords, provided an ample key length. Other authentication methods are only used in very specific situations.

SSH can use either 'RSA' (Rivest-Shamir-Adleman) or 'DSA' ('Digital Signature Algorithm') keys. Both of these were considered state-of-the-art algorithms when SSH was invented, but DSA has come to be seen as less secure in recent years. RSA is the only recommended choice for new keys, so this guide uses 'RSA key' and 'SSH key' interchangeably.

Key-based authentication uses two keys, one 'public' key that anyone is allowed to see, and another 'private' key that only the owner is allowed to see. To securely communicate using key-based authentication, one needs to create a key pair, securely store the private key on the computer one wants to log in from, and store the public key on the computer one wants to log in to.

Using key based logins with ssh is generally considered more secure than using plain password logins. This section of the guide will explain the process of generating a set of public/private RSA keys, and using them for logging into your Ubuntu computer(s) via OpenSSH.

The first step involves creating a set of RSA keys for use in authentication.

This should be done on the client.

Generation of CSR for Apache and nginxLinux servers use OpenSSL libraries when encrypting and working with keys. After successfully logging on to the server, you will create the CSR request (the public key). Generate public key certificate online free. The certificate authority must be provided with this request. In those libraries you can create the CSR request for your certificate that is used by an Apache or nginx server. You just need to put the request into the order form at SSLmarket.The CSR will be created in OpenSSL.

To create your public and private SSH keys on the command-line:

You will be prompted for a location to save the keys, and a passphrase for the keys. This passphrase will protect your private key while it's stored on the hard drive:

Your public key is now available as .ssh/id_rsa.pub in your home folder.

Congratulations! You now have a set of keys. Now it's time to make your systems allow you to login with them

Choosing a good passphrase

You need to change all your locks if your RSA key is stolen. Otherwise the thief could impersonate you wherever you authenticate with that key.

An SSH key passphrase is a secondary form of security that gives you a little time when your keys are stolen. If your RSA key has a strong passphrase, it might take your attacker a few hours to guess by brute force. That extra time should be enough to log in to any computers you have an account on, delete your old key from the .ssh/authorized_keys file, and add a new key.

Your SSH key passphrase is only used to protect your private key from thieves. It's never transmitted over the Internet, and the strength of your key has nothing to do with the strength of your passphrase.

The decision to protect your key with a passphrase involves convenience x security. Note that if you protect your key with a passphrase, then when you type the passphrase to unlock it, your local computer will generally leave the key unlocked for a time. So if you use the key multiple times without logging out of your local account in the meantime, you will probably only have to type the passphrase once.

If you do adopt a passphrase, pick a strong one and store it securely in a password manager. You may also write it down on a piece of paper and keep it in a secure place. If you choose not to protect the key with a passphrase, then just press the return when ssh-keygen asks.

Key Encryption Level

Note: The default is a 2048 bit key. You can increase this to 4096 bits with the -b flag (Increasing the bits makes it harder to crack the key by brute force methods).

Password Authentication

The main problem with public key authentication is that you need a secure way of getting the public key onto a computer before you can log in with it. If you will only ever use an SSH key to log in to your own computer from a few other computers (such as logging in to your PC from your laptop), you should copy your SSH keys over on a memory stick, and disable password authentication altogether. If you would like to log in from other computers from time to time (such as a friend's PC), make sure you have a strong password.

The key you need to transfer to the host is the public one. If you can log in to a computer over SSH using a password, you can transfer your RSA key by doing the following from your own computer:

Where <username> and <host> should be replaced by your username and the name of the computer you're transferring your key to.

Due to this bug, you cannot specify a port other than the standard port 22. You can work around this by issuing the command like this: ssh-copy-id '<username>@<host> -p <port_nr>'. If you are using the standard port 22, you can ignore this tip.

Another alternative is to copy the public key file to the server and concatenate it onto the authorized_keys file manually. It is wise to back that up first:

You can make sure this worked by doing:

You should be prompted for the passphrase for your key:

Enter your passphrase, and provided host is configured to allow key-based logins, you should then be logged in as usual.

Encrypted Home Directory

If you have an encrypted home directory, SSH cannot access your authorized_keys file because it is inside your encrypted home directory and won't be available until after you are authenticated. Therefore, SSH will default to password authentication.

To solve this, create a folder outside your home named /etc/ssh/<username> (replace '<username>' with your actual username). This directory should have 755 permissions and be owned by the user. Move the authorized_keys file into it. The authorized_keys file should have 644 permissions and be owned by the user.

Then edit your /etc/ssh/sshd_config and add:

Finally, restart ssh with:

The next time you connect with SSH you should not have to enter your password.

Generate Git Ssh Key Ubuntu 10

username@host's password:

If you are not prompted for the passphrase, and instead get just the

prompt as usual with password logins, then read on. There are a few things which could prevent this from working as easily as demonstrated above. On default Ubuntu installs however, the above examples should work. If not, then check the following condition, as it is the most frequent cause:

On the host computer, ensure that the /etc/ssh/sshd_config contains the following lines, and that they are uncommented;

If not, add them, or uncomment them, restart OpenSSH, and try logging in again. If you get the passphrase prompt now, then congratulations, you're logging in with a key!

Permission denied (publickey)

If you're sure you've correctly configured sshd_config, copied your ID, and have your private key in the .ssh directory, and still getting this error:

Chances are, your /home/<user> or ~/.ssh/authorized_keys permissions are too open by OpenSSH standards. You can get rid of this problem by issuing the following commands:

Error: Agent admitted failure to sign using the key.

This error occurs when the ssh-agent on the client is not yet managing the key. Issue the following commands to fix:

This command should be entered after you have copied your public key to the host computer.

Debugging and sorting out further problems

The permissions of files and folders is crucial to this working. You can get debugging information from both the client and server.

if you think you have set it up correctly , yet still get asked for the password, try starting the server with debugging output to the terminal.

To connect and send information to the client terminal

No matter how your public key was generated, you can add it to your Ubuntu system by opening the file .ssh/authorized_keys in your favourite text editor and adding the key to the bottom of the file. You can also limit the SSH features that the key can use, such as disallowing port-forwarding or only allowing a specific command to be run. This is done by adding 'options' before the SSH key, on the same line in the authorized_keys file. For example, if you maintain a CVS repository, you could add a line like this:

When the user with the specified key logged in, the server would automatically run /usr/bin/cvs server, ignoring any requests from the client to run another command such as a shell. For more information, see the sshd man page. /755

When you work with a Git repository, your project may be actively modified by a lot of people. Some of them may not be trustworthy as they may be new employees or something like that. In this case, if they need to do git pull in the server to update the changes of a commit in your production server, you may not want that everybody knows the password of the repository. Another case where you don't want to provide the password of the repository everytime you do git pull or git clone, are automatized deployments.

That's why the the 'deployment keys' feature exist in Gitlab, A deploy key is an SSH key that is stored on your server and grants access to a single Gitlab repository. This key is attached directly to the repository instead of to a personal user account. In this article, we'll show you step by step how you can automatize the deployment process of your project hosted on Gitlab.

1. Find or create an SSH Key for your server

The first thing that you need to do is to verify if your server has already a public key created in the .ssh directory of the user in the server, so start a SSH session to your server and type the following command:

This will automatically search in the folder of your user that in our case is /home/vagrant/.ssh, if the output of the command shows a string that starts with ssh-rsa, then you already have an SSH Key that you can use to add to your repository, so you can skip to the step 2. If instead, you get the output : cat: ~/.ssh/id_rsa.pub: No such file or directory, then you will need to create an SSH Key first. You can create a SSH Key in Ubuntu via SSH with the following command (navigate to the .ssh directory first and type):

To make the process easy, we won't add a Keyphrase for the SSH Key, so as mentioned in the creation wizard just press enter to don't use a keyphrase:

As shown in the image, we no have the id_rsa and id_rsa.pub file in our .ssh directory. This key works as a 'pass' that allows to clone/pull your project in the current server, till this point it doesn't do anything, so you will need to follow the other steps.

2. Configure SSH client to find your GitLab private SSH in the server

As next step you need to establish that, when cloning from Gitlab, the deployment key should be used as authentication instead of an username and a password. For this you need to ensure that ssh-agent is enabled by running the following command:

Then you can proceed to add your key to the SSH registry using the following command:

To retain these settings you'll need to save them to a configuration file. Normally on OpenSSH clients you can configure this in the ~/.ssh/config file. If the file doesn't exist, you can create it:

And register your key in the file. In this tutorial we are adding a single SSH Key from the Gitlab website (non self hosted version), so our config file content will be:

As you may have multiple projects in one server or a project that uses different repositories that need to be updated, you can without a problem implement multiple SSH Keys in the same file following the notation:

3. Add the Server Key as a deployment key in your Repository configuration

Now you need the public key of your server (created in step 1), in this step you are saying to Gitlab 'Hey, if someone uses this SSH Key to clone, allow him to do it'. You can get the content of the public file using a text editor via SFTP, or just by printing the output of the file with SSH using the following command:

This would output in our case the content of the public key:

Keep that long string in the clipboard as you will need it to paste it in Gitlab. As next acccess the Settings of your Repository in Gitlab, in our case as we are using the non self hosted version of Gitlab the configuration for the Deploy Keys is in https://gitlab.com/<username>/<repository-name>/settings/repository. The menu to add a new deploy key looks like this:

Here you would only need to add the content of the id_rsa.pub file, provide a title and decide wheter the server can be used to push changes as well or not (normally unchecked as it is production). Once the key is added in your repository, you should be able now to clone/pull your repository in the deployment server.

Generate Git Ssh Key Ubuntu Windows 10

4. Clone and pull repository to test

As final step, to verify if everything went right you can clone your repository to see if the credentials of the repository are requested or not, in case it does, please read the tutorial again and check what you did wrong. Otherwise, you will be able to clone your project using the following command:

Note

Git

Remember to clone via SSH, not HTTPS, otherwise you may obviously be asked for the credentials.

By doing this you may have noticed that you didn't have to input your Gitlab username nor password thanks to the deployment key!

Happy coding !