Generate Ssh_host_ecdsa_key

The first time I connect to a newly-created Droplet, I expect to be able to validate that the ECDSA key fingerprint is valid before adding it to my known_hosts file. I have not been able to find this information on the forum, how-to’s, or in the web console.

1. Generate Ssh_host_ecdsa_key File
2. Ssh Keygen Ecdsa
3. Ecdsa Host Key Has Changed

I’ve read through How To Connect To Your Droplet with SSH, and the DO moderator surprisingly recommends disregarding the possibility of a man-in-the-middle attack and blindly accepting the key. The actual statement is as follows: “The first time you attempt to connect to your server, you will likely see a warning that looks like this… The authenticity of host ‘123.123.123.123 (123.123.123.123)’ can’t be established… Go ahead and type yes to continue to connect. Here, your computer is telling you that the remote server is not recognized. Since this is your first time connecting, this is completely expected.” I agree that it’s expected. However, I don’t agree that that means it’s safe to assume that the connection is not compromised.

Cd /etc/ssh/ sudo rm sshhostecdsakey sudo touch sshhostecdsakey sudo rm sshhostecdsakey.pub sudo touch sshhostecdsakey.pub The key is invalid and not used, but is not corrected/regenerate when starting up.

Back to my question then: Is there any way to validate the host’s fingerprint before connecting? Ideally it would be part of the response body when a new droplet is created or have its own API call.

• englunddavidbOctober 25, 2017

  I found ways to validate host keys with Azure and with EC2 but still haven’t found the equivalent for DigitalOcean Droplets.

• Only RSA is an encryption algorithm. Both DSA and ECDSA are used for digital signing - the latter being an Elliptic Curve implementation of DSA (Digital Signature Algorithm). Elliptic curve cryptography is able to provide the same security level as RSA with a smaller key and is a 'lighter calculation' workload-wise.
• A host key is a cryptographic key used for authenticating computers in the SSH protocol. Host keys are key pairs, typically using the RSA, DSA, or ECDSA algorithms. Public host keys are stored on and/or distributed to SSH clients, and private keys are stored on SSH servers.
• How to regenerate new ssh server keys This is an unusual topic since most distribution create these keys for you during the installation of the OpenSSH server package. But it may be useful to be able generate new server keys from time to time, this happen to me when I duplicate Virtual Private Server which contains an installed ssh package.
• I deleted the existing keys: $ sudo rm -f /etc/ssh/sshhostecdsakey. I uncomment ECDSA in /etc/ssh/sshdconfig $ grep -i ecdsa /etc/ssh/sshdconfig # Stack Exchange Network Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge.
• When you are done, you have performed setup for server authentication in which keys will be stored in UNIX files. Each time the host keys are regenerated, they must be redistributed and added to the key ring of the remote system. Figure 1 shows how the knownhosts file is created when keys are stored in UNIX files.

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This repo contains a showcase of how to use SSH certificates (for hosts & users) generated by step-ca using the step CLI'sssh sub-command.

If you haven't already you should read our blogpost on why SSH certificatesare better than SSH public keys for authentication and how you can achieve defacto SSH Single Sign-on while doing away with pesky public key managementacross your server fleet.

This document describes:

• how to provision step-ca to issue SSH host & user certificates.
• how sshd is configured to accept user certificates for client authentication using a CA key.
• how sshd is configured to present a host certificate for host authentication on the client-side.
• how to configure a user's ssh to accept host certificate signed by a CA key.
• how to configure a user's ssh to present a user certificate for authentication on the server-side.

The code in this repo comes with a pre-generated PKI. You will need stepv0.13.3+ (installation docs)and Vagrant (plus a provider likeVirtualBox) installed locally.

Setup VM

We're going to run a CA in your local environment, and we'll use ssh toconnect to a Vagrant VM(representing a remote host) that has sshd pre-configured to acceptuser certificates signed by our CA.

With Vagrant installed, run the following commands inside the repo:

Configure ssh client to accept host certs

Go ahead and follow the instructions printed by Vagrant. This will enable yourlocal SSH client to accept SSH host certificates (signed by the root SSH hostprivate key). The following command will append the SSH host CA key(root SSH host public key corresponding to the root SSH host private key) toyour local known_hosts file:

You can also find the root SSH host CA key stored atstep/certs/ssh_host_key.pub in this repo.

Certificates bind names to public keys. This SSH host certificate has theidentity testhost which is why the following entry must be added to thelocal /etc/hosts file on the VM:

Configure sshd to accept user certs

Vagrant has already configured sshd on testhost, the VMgenerated by Vagrant. Please note that for demo purposes the PKI is shared withthe VM using a shared directory mount. Below you can see the relevant linesfrom the testhost VM's sshd_config:

• TrustUserCAKeys: The root SSH user public key used to verify SSHuser certificates.
• HostKey: The SSH private key specific to this host.
• HostCertificate: The SSH public certificate that uniquelyidentifies this host (signed by the root SSH host private key).

Login to VM via SSH user cert

A valid user certificate is required to log into the testhost VM. Using thestep CLI we will authenticate with our SSH-enabled CA and fetch a new SSHcertificate.

In one terminal window run the following command to startup your CA (passwordis password):

Generate Ssh_host_ecdsa_key File

In another terminal window run:

NOTE: step-ca enforces authentication for all certificate requests and usesthe concept ofprovisionersto carry out this enforcement. Provisioners are configured instep/config/ca.json. Authenticating as one of the sanctioned provisionersindicates to step-ca that you have the right to provisione newcertificates. In the above invocation of step ssh certificate we haveauthenticated our request using a JWK provisioner, which simply requires apassword to decrypt a private key. However, there are a handful of supportedprovisioners, each with it's own authentication methods. The OIDC provisioneris particularly interesting for SSH user certificates because it enablesSingle Sign-On SSH.

Conveniently, step ssh certificate adds the new SSH user certificate to yourlocal ssh agent. The default lifetime of an SSH certificate from step-ca is4hrs. The lifetime can be configured using command line options (run step ssh certificate -h for documentation and examples).

Boom! As you can see the testhost VM will welcome you with a matchingtestuser@testhost prompt.

Learn how to use OAuth OIDC proviers like Gsuite or Instance Identity Documentsto bootstrap SSH host and user certificates in our blog post If you’re not using SSHcertificates you’re doing SSHwrong or check out thestep CLI reference athttps://smallstep.com/docs/cli/ssh/.

Generate ssh host certificates

This example repo includes a pre-generated SSH host certificate and key. To replace itor generate SSH certificates for other hosts running following command:

Where --principal identifies the hostname(s) (ideally FQDNs) for the machine.For a single principal you can short cut the command to:

Generate your own PKI for step-ca

Ssh Keygen Ecdsa

We recommend using your own PKI for usage outside of this example. You caninitialize your step-ca withboth X509 and SSH certificates using the following command:

Now you can launch your instance ofstep-ca with your own PKI likeso:

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Ecdsa Host Key Has Changed

Please note that after you regenerate ssh_host_key.pub and ssh_user_key.pubyou will have to reconfigure ssh and sshd for clients and hosts to acceptthe new CA keys. Check out this host bootstrapping script forconfiguration examples.