Windows Ssh Generate Public Key
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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:
- Save the text file in the same folder where you saved the private key, using the.pub extension to indicate that the file contains a public key. If you or others are going to use an SSH client that requires the OpenSSH format for private keys (such as the ssh utility on Linux), export the private key: On the Conversions menu, choose Export.
- 2 Generate a private and public key pair: Go to the Windows Start menu - All Programs - PuTTY and open PuTTYgen; Click the 'Generate' button and PuTTYgen will ask you to make some random movement with your mouse until it has enough random data to generate a secure key for you; Click the 'Save private key' button and save the resulting file.
Type in the passphrase and confirm it. The passphrase is used to protect your key. You will be asked for it when you connect via SSH. Click 'Save private key' to save your private key. Click 'Save public key' to save your public key. For more information on how to load the key and connect via SSH using PuTTY, please check this tutorial. With both Tectia SSH and OpenSSH servers, access to an account is granted by adding the public key to a /.ssh/authorizedkeys file on the server. To install the public key, Log into the server, edit the authorizedkeys file with your favorite editor, and cut-and-paste the public key output by the above command to the authorizedkeys file.
- 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.
Get Ssh Key
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.
-->This article describes ways to generate and use secure shell (SSH) keys on a Windows computer to create and connect to a Linux virtual machine (VM) in Azure. To use SSH keys from a Linux or macOS client, see the quick or detailed guidance.
Overview of SSH and keys
SSH is an encrypted connection protocol that allows secure sign-ins over unsecured connections. SSH is the default connection protocol for Linux VMs hosted in Azure. Although SSH itself provides an encrypted connection, using passwords with SSH connections still leaves the VM vulnerable to brute-force attacks or guessing of passwords. A more secure and preferred method of connecting to a VM using SSH is by using a public-private key pair, also known as SSH keys.
The public key is placed on your Linux VM, or any other service that you wish to use with public-key cryptography.
The private key remains on your local system. Protect this private key. Do not share it.
When you use an SSH client to connect to your Linux VM (which has the public key), the remote VM tests the client to make sure it possesses the private key. If the client has the private key, it's granted access to the VM.
Depending on your organization's security policies, you can reuse a single public-private key pair to access multiple Azure VMs and services. You do not need a separate pair of keys for each VM or service you wish to access.
Your public key can be shared with anyone, but only you (or your local security infrastructure) should possess your private key.
Supported SSH key formats
Azure currently supports SSH protocol 2 (SSH-2) RSA public-private key pairs with a minimum length of 2048 bits. Other key formats such as ED25519 and ECDSA are not supported.
Windows packages and SSH clients
You connect to and manage Linux VMs in Azure using an SSH client. Computers running Linux or macOS usually have a suite of SSH commands to generate and manage SSH keys and to make SSH connections.
Windows computers do not always have comparable SSH commands installed. Recent versions of Windows 10 provide OpenSSH client commands to create and manage SSH keys and make SSH connections from a command prompt. Recent Windows 10 versions also include the Windows Subsystem for Linux to run and access utilities such as an SSH client natively within a Bash shell.
Other common Windows SSH clients you can install locally are included in the following packages:
You can also use the SSH utilities available in Bash in the Azure Cloud Shell.
- Access Cloud Shell in your web browser at https://shell.azure.com or in the Azure portal.
- Access Cloud Shell as a terminal from within Visual Studio Code by installing the Azure Account extension.
Create an SSH key pair
The following sections describe two options to create an SSH key pair on Windows. You can use a shell command (ssh-keygen) or a GUI tool (PuTTYgen). Also note, when using Powershell to create a key, upload the public key as ssh.com(SECSH) format. When using CLI, convert the key into OpenSSH format prior to uploading.
Create SSH keys with ssh-keygen
If you run a command shell on Windows that supports SSH client tools (or you use Azure Cloud Shell), create an SSH key pair using the ssh-keygen command. Type the following command, and answer the prompts. If an SSH key pair exists in the chosen location, those files are overwritten.
For more background and information, see the quick or detailed steps to create SSH keys using ssh-keygen.
Create SSH keys with PuTTYgen
If you prefer to use a GUI-based tool to create SSH keys, you can use the PuTTYgen key generator, included with the PuTTY download package.
To create an SSH RSA key pair with PuTTYgen:
Start PuTTYgen.
Click Generate. By default PuTTYgen generates a 2048-bit SSH-2 RSA key.
Move the mouse around in the blank area to provide randomness for the key.
After the public key is generated, optionally enter and confirm a passphrase. You will be prompted for the passphrase when you authenticate to the VM with your private SSH key. Without a passphrase, if someone obtains your private key, they can sign in to any VM or service that uses that key. We recommend you create a passphrase. However, if you forget the passphrase, there is no way to recover it.
The public key is displayed at the top of the window. You can copy this entire public key and then paste it into the Azure portal or an Azure Resource Manager template when you create a Linux VM. You can also select Save public key to save a copy to your computer:
Optionally, to save the private key in PuTTy private key format (.ppk file), select Save private key. You will need the .ppk file later to use PuTTY to make an SSH connection to the VM.
If you want to save the private key in the OpenSSH format, the private key format used by many SSH clients, select Conversions > Export OpenSSH key.
Provide an SSH public key when deploying a VM
To create a Linux VM that uses SSH keys for authentication, provide your SSH public key when creating the VM using the Azure portal or other methods.
The following example shows how you would copy and paste this public key into the Azure portal when you create a Linux VM. The public key is typically then stored in the ~/.ssh/authorized_key directory on your new VM.
Connect to your VM
One way to make an SSH connection to your Linux VM from Windows is to use an SSH client. This is the preferred method if you have an SSH client installed on your Windows system, or if you use the SSH tools in Bash in Azure Cloud Shell. If you prefer a GUI-based tool, you can connect with PuTTY.
Use an SSH client
With the public key deployed on your Azure VM, and the private key on your local system, SSH to your VM using the IP address or DNS name of your VM. Replace azureuser and myvm.westus.cloudapp.azure.com in the following command with the administrator user name and the fully qualified domain name (or IP address):
If you configured a passphrase when you created your key pair, enter the passphrase when prompted during the sign-in process.
Generate Ssh Public Key Windows Git Bash
If the VM is using the just-in-time access policy, you need to request access before you can connect to the VM. For more information about the just-in-time policy, see Manage virtual machine access using the just in time policy.
Connect with PuTTY
If you installed the PuTTY download package and previously generated a PuTTY private key (.ppk) file, you can connect to a Linux VM with PuTTY.
Start PuTTy.
Fill in the host name or IP address of your VM from the Azure portal:
Select the Connection > SSH > Auth category. Browse to and select your PuTTY private key (.ppk file):
Click Open to connect to your VM.
Next steps
Generate Public Key Windows 10
For detailed steps, options, and advanced examples of working with SSH keys, see Detailed steps to create SSH key pairs.
You can also use PowerShell in Azure Cloud Shell to generate SSH keys and make SSH connections to Linux VMs. See the PowerShell quickstart.
If you have difficulty using SSH to connect to your Linux VMs, see Troubleshoot SSH connections to an Azure Linux VM.