8/29/2021
39
  1. Private Key Example
  2. Private Key Ssh Authentication
  3. Remove Ssh Private Key Passphrase

Log in with an SSH private key on Linux and macOS

Private keys allow the users to login to SSH without a password. This is considered a safe practice in some cases while also discards the need to remember multiple passwords. Sep 19, 2019 Your private key. For more information about generating a key on Linux or macOS, see Connect to a server by using SSH on Linux or Mac OS X. Log in with a private key Using a text editor, create a file in which to store your private key. SSH also offers passwordless authentication. In this scenario, a public-private key pair is manually generated. The public key is placed on all remote systems and allows access to the owner of the matching private key. The owner is responsible for keeping the private key secret. SSH clients will typically use /.ssh/identity (ssh v1) or one of /.ssh/idrsa or /.ssh/iddsa (v2) as the default private key. You can change this in /.ssh/config (the IdentityFile parameter - the -i option to SSH actually overrides this. See man sshconfig for details). @ @@@@@ Permissions for 'private-key.ppk' are too open. It is required that your private key files are NOT accessible by others. This private key will be ignored. Load key 'private-key.ppk': bad permissions [email protected]: Permission denied (publickey).

Authored by: Brint Ohearn

This article demonstrates how to use a private key to log in to a Linux®server by using a private key with a Terminal session on macOS®. However,you can follow the same process to use a private key when using anyterminal software on Linux.

Note: For information about using Secure Shell (SSH) private keys on Microsoft®Windows® operating systems, seeLogging in with an SSH Private Key on Windowsand Generate RSA keys with SSH by using PuTTYgen.

Prerequisites

To complete this process, you need the following software applications:

  • SSH client software that is installed on your Linux or macOS operating system by default.
  • Your favorite text editor. This example uses the vim text editor.
  • Your private key. For more information about generating a key on Linux or macOS, seeConnect to a server by using SSH on Linux or Mac OS X.

Log in with a private key

  1. Using a text editor, create a file in which to store your private key. This example usesthe file deployment_key.txt.

  2. To edit the file in vim, type the following command:

  3. After the editor starts, press i to turn on insert mode.

  4. Paste your private key, such as the one in the following image, into the file.Be sure to include the BEGIN and END lines.

  5. To save your changes, press Esc.

  6. Type :wq to write the file and return to the command line.

  7. Run the following command to change the file permissions to 600 to secure the key. You can also set them to 400.This step is required:

  8. Use the key to log in to the SSH client as shown in the following example, which loads the key in file deployment_key.txt, and logs in as user demo to IP 192.237.248.66:

  9. When you are prompted to confirm the connection, type yes and then press Enter.

  10. If your SSH key requires a password, enter it when prompted to complete the connection.

Share this information:

©2020 Rackspace US, Inc.

Except where otherwise noted, content on this site is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License

-->

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 vulnerable to brute force intrusions.

By comparison, Linux environments commonly use public-key/private-key pairs to drive authentication which doesn't require the use of guessable passwords.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.

Private Key Example

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 stay 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 keys for username provided against the private key. If the server-side public key cannot be validated against the client-side private key, authentication fails.

Private Key Ssh Authentication

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.

Remove Ssh Private Key Passphrase

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.

Private Key Ssh

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.

Swerve

6817.info – 2018