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- SSH, the secure shell, is often used to access remote Linux systems. But its authentication mechanism, where a private local key is paired with a public remote key, is used to secure all kinds of online services, from GitHub and Launchpad to Linux running on Microsoft’s Azure cloud.
- Aug 19, 2019 In this article, you learned how to generate SSH key pairs and set up an SSH key-based authentication. We also covered copying keys to your remote CentOS server, and disabling SSH password authentication.
- May 20, 2018 Private keys are protected with DPAPI and stored in the HKCU registry hive. I released some PoC code here to extract and reconstruct the RSA private key from the registry. Using OpenSSH in Windows 10. The first thing I tested was using the OpenSSH utilities normally to generate a few key-pairs and adding them to the ssh-agent.
Dec 01, 2017 SSH Key Gen & SSH Keys on windows system to Linux Server NAME ssh-keygen - authentication key generation, management and conversion ssh-keygen generates, manages and converts authentication keys for ssh. Ssh-keygen can create RSA keys for use by SSH protocol version 1 and DSA, ECDSA or RSA keys for use by SSH protocol version 2. From the PuTTY Key Generator dialog, click the Generate button. As the SSH key generates, hover your mouse over the blank area in the dialog. It may take a minute or two. When SSH key generation is complete, you see the public key and a few other fields. Enter a passphrase for your SSH key in the Key passphrase and Confirm passphrase fields.
Most authentication in Windows environments is done with a username-password pair.This works well for systems that share a common domain.When working across domains, such as between on-premise and cloud-hosted systems, it becomes more difficult.
By comparison, Linux environments commonly use public-key/private-key pairs to drive authentication.OpenSSH includes tools to help support this, specifically:
- ssh-keygen for generating secure keys
- ssh-agent and ssh-add for securely storing private keys
- scp and sftp to securely copy public key files during initial use of a server
This document provides an overview of how to use these tools on Windows to begin using key authentication with SSH.If you are unfamiliar with SSH key management, we strongly recommend you review NIST document IR 7966 titled 'Security of Interactive and Automated Access Management Using Secure Shell (SSH).'
About key pairs
Key pairs refer to the public and private key files that are used by certain authentication protocols.
SSH public-key authentication uses asymmetric cryptographic algorithms to generate two key files – one 'private' and the other 'public'. The private key files are the equivalent of a password, and should protected under all circumstances. If someone acquires your private key, they can log in as you to any SSH server you have access to. The public key is what is placed on the SSH server, and may be shared without compromising the private key.
When using key authentication with an SSH server, the SSH server and client compare the public key for username provided against the private key. If the public key cannot be validated against the client-side private key, authentication fails.
Multi-factor authentication may be implemented with key pairs by requiring that a passphrase be supplied when the key pair is generated (see key generation below).During authentication the user is prompted for the passphrase, which is used along with the presence of the private key on the SSH client to authenticate the user.
Host key generation
Public keys have specific ACL requirements that, on Windows, equate to only allowing access to administrators and System.To make this easier,
- The OpenSSHUtils PowerShell module has been created to set the key ACLs properly, and should be installed on the server
- On first use of sshd, the key pair for the host will be automatically generated. If ssh-agent is running, the keys will be automatically added to the local store.
To make key authentication easy with an SSH server, run the following commands from an elevated PowerShell prompt:
Since there is no user associated with the sshd service, the host keys are stored under ProgramDatassh.
User key generation
To use key-based authentication, you first need to generate some public/private key pairs for your client.From PowerShell or cmd, use ssh-keygen to generate some key files.
This should display something like the following (where 'username' is replaced by your user name)
You can hit Enter to accept the default, or specify a path where you'd like your keys to be generated.At this point, you'll be prompted to use a passphrase to encrypt your private key files.The passphrase works with the key file to provide 2-factor authentication.For this example, we are leaving the passphrase empty.
Now you have a public/private ED25519 key pair(the .pub files are public keys and the rest are private keys):
Remember that private key files are the equivalent of a password should be protected the same way you protect your password.To help with that, use ssh-agent to securely store the private keys within a Windows security context, associated with your Windows login.To do that, start the ssh-agent service as Administrator and use ssh-add to store the private key.
After completing these steps, whenever a private key is needed for authentication from this client, ssh-agent will automatically retrieve the local private key and pass it to your SSH client.
Note
It is strongly recommended that you back up your private key to a secure location,then delete it from the local system, after adding it to ssh-agent.The private key cannot be retrieved from the agent.If you lose access to the private key, you would have to create a new key pairand update the public key on all systems you interact with.
Deploying the public key
To use the user key that was created above, the public key needs to be placed on the server into a text file called authorized_keys under usersusername.ssh.The OpenSSH tools include scp, which is a secure file-transfer utility, to help with this.
To move the contents of your public key (~.sshid_ed25519.pub) into a text file called authorized_keys in ~.ssh on your server/host.
This example uses the Repair-AuthorizedKeyPermissions function in the OpenSSHUtils module which was previously installed on the host in the instructions above.
These steps complete the configuration required to use key-based authentication with SSH on Windows.After this, the user can connect to the sshd host from any client that has the private key.
Overview
Public key authentication is a way of logging into an SSH/SFTP account using a cryptographic key rather than a password.
If you use very strong SSH/SFTP passwords, your accounts are already safe from brute force attacks. However, using public key authentication provides many benefits when working with multiple developers. For example, with SSH keys you can
- allow multiple developers to log in as the same system user without having to share a single password between them;
- revoke a single developer's access without revoking access by other developers; and
- make it easier for a single developer to log in to many accounts without needing to manage many different passwords.
How Public Key Authentication Works
Keys come in pairs of a public key and a private key. Each key pair is unique, and the two keys work together.
These two keys have a very special and beautiful mathematical property: if you have the private key, you can prove you have it without showing what it is. It's like proving you know a password without having to show someone the password.
Public key authentication works like this:
- Generate a key pair.
- Give someone (or a server) the public key.
- Later, anytime you want to authenticate, the person (or the server) asks you to prove you have the private key that corresponds to the public key.
- You prove you have the private key.
You don't have to do the math or implement the key exchange yourself. The SSH server and client programs take care of this for you.
Generate an SSH Key Pair
You should generate your key pair on your laptop, not on your server. All Mac and Linux systems include a command called ssh-keygen that will generate a new key pair.
If you're using Windows, you can generate the keys on your server. Just remember to copy your keys to your laptop and delete your private key from the server after you've generated it.
To generate an SSH key pair, run the command ssh-keygen.
It will look like this when you run it:
You'll be prompted to choose the location to store the keys. The default location is good unless you already have a key. Press Enter to choose the default location.
Next, you'll be asked to choose a password. Using a password means a password will be required to use the private key. It's a good idea to use a password on your private key.
After you choose a password, your public and private keys will be generated. There will be two different files. The one named id_rsa is your private key. The one named id_rsa.pub is your public key.
You'll also be shown a fingerprint and 'visual fingerprint' of your key. You do not need to save these.
Configure an SSH/SFTP User for Your Key
Method 1: Using ssh-copy-id
Now that you have an SSH key pair, you're ready to configure your app's system user so you can SSH or SFTP in using your private key.
To copy your public key to your server, run the following command. Be sure to replace 'x.x.x.x' with your server's IP address and SYSUSER with the name of the the system user your app belongs to.
![Generate Generate](/uploads/1/2/6/0/126088143/612718076.png)
Method 2: Manual Configuration
If you don't have the ssh-copy-id command (for example, if you are using Windows), you can instead SSH in to your server and manually create the .ssh/authorized_keys file so it contains your public key.
First, run the following commands to make create the file with the correct permissions.
Next, edit the file .ssh/authorized_keys using your preferred editor. Copy and paste your id_rsa.pub file into the file.
Log In Using Your Private Key
You can now SSH or SFTP into your server using your private key. From the command line, you can use:
If you didn't create your key in the default location, you'll need to specify the location:
If you're using a Windows SSH client, such as PuTTy, look in the configuration settings to specify the path to your private key.
Granting Access to Multiple Keys
The .ssh/authorized_keys file you created above uses a very simple format: it can contain many keys as long as you put one key on each line in the file.
If you have multiple keys (for example, one on each of your laptops) or multiple developers you need to grant access to, just follow the same instructions above using ssh-copy-id or manually editing the file to paste in additional keys, one on each line.
When you're done, the .ssh/authorized_keys file will look something like this (don't copy this, use your own public keys):
Additional Information
Retrieve Your Public Key from Your Private Key
The following command will retrieve the public key from a private key:
This can be useful, for example, if your server provider generated your SSH key for you and you were only able to download the private key portion of the key pair.
Note that you cannot retrieve the private key if you only have the public key.
Correcting Permissions on the .ssh Directory
The instructions in this article will create your server's .ssh directory and .ssh/authorized_keys file with the correct permissions. However, if you've created them yourself and need to fix permissions, you can run the following commands on your server while SSH'd in as your app's system user.
Disabling Password Authentication
Ssh Generate Private Key Windows 8
NOTE: When changing anything about the way SSH is accessed(ports, authentication methods, et cetera), it is very strongly recommended to leave an active root SSH session open until everything is working as intended. This ensures you have a way to revert changes in the event something goes wrongand logins are not working properly.
Generate Ssh Key Windows Cmd
As an extra security precaution, once you have set up SSH keys, you may wish to disable password authentication entirely. This will mean no users will be able to log into SSH or SFTP without SSH keys. Anyone entering a password will receive a message like:
Or:
Disabling password authentication is an excellent way to improve server security. Please see our guide here for the steps to accomplish this goal.
Then, test whether you're able to log in with a password by opening a new SSH or SFTP session to the server. Passwords should not be able to be used and, if everything has been done correctly, an error will be issued when someone tries to use a password. Unless this setting is changed back to allow password authentication, no users will be able to log in without an SSH key set up.