Public key authentication is a way of logging into an SSH/SFTP account using a cryptographic key rather than a password.
Overview
Create Ssh Key Cisco
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
Nov 17, 2016 hello everyone. Today I will show you how to login Cisco router using ssh key. We will enable ssh on the router and then generate a key on an Ubuntu Linux server and using that key we will login to our router. The process is easy, lets start. Change the hostname of the router. Follow the below procedure to change the hostname of the router. Since we selected to generate a key using 4096 bits, the router took a bit over 3 minutes to generate the key! Note that router used in our example was a Cisco 877. With SSH enabled we are able to ssh into our router and manage it securely from any location around the globe. To view any active SSH session, simply use the show ssh command: R1. How to configure SSH on Cisco IOS In a previous lesson, I explained how you can use telnet for remote access to your Cisco IOS devices. The problem with telnet is that everything is sent in plaintext, for that reason you shouldnât use it. Config t crypto key generate rsa exit Then ssh to the router and complete the config. Or just enable telnet if you can get away with it. Config t vty 0 4 transport input ssh telnet exit I have a perl script that does this to reset enable passwords. Apr 23, 2019 Encryption keys can vary in length, with typical lengths from 512 bits to 2048 bits. In general, a longer key is more secure than a shorter key. Cisco UCS Manager provides a default key ring with an initial 1024-bit key pair, and allows you to create additional key rings.
How Public Key Authentication WorksSsh Generate Key Pair
Keys come in pairs of a public key and a private key. Each key pair is unique, and the two keys work together. Cheese sauce for mac n cheese.
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:
Mac osx 10.6.8 update apps. 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 KeyMethod 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.
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 InformationRetrieve 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.
Command To Generate Ssh Key Cisco PasswordDisabling Password Authentication
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.
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:
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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.
Cisco Ssh Rsa Key
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