Teleport is software which provides an SSH Jump Host (or Bastion host) service in a secure, modern, way, with support for role-based access control, and single sign-on.
It can be used as a replacement for the ecAccess SSH service, and is being evaluated by the CD Apps team and User Support.
This service is under development and not widely accessible. Please continue to use the existing ECAccess service!
Please read all the introductory "understanding" sections (even if you think you know them), so that the presentation of Teleport makes sense in context.
Security Context
We have remote users, who we do not know very much about (e.g. researcher in a university who is sponsored by a Member State national weather service), connecting to our HPC cluster on which we also run mission-critical operational forecasting. As these aspects are unavoidable, measures need to be in place to sufficiently secure the access to our HPC facility.
Let's take the JASMIN cluster service as an example and compare our situation to theirs.
First, JASMIN is a research facility, so does not have the same availability and integrity concerns as ECMWF.
Second, we can see that it's normal for users to have to go through a non-trivial process to access a cluster: generating an SSH keypair and uploading the public key to a website. This also implies ECMWF running such a service to manage key uploads.
Furthermore, JASMIN "requires" users to secure their key with a passphrase, but there's no way this can be enforced. It's quite likely users don't bother, and the SSH keys are copied around freely and even lost and replaced, while remaining active for access to the facility.
Third, we also know from other remote cluster providers that it's common to have to connect to a bastion host, and then hop onwards to the final working node. At ECMWF we much prefer users have a single hop straight to the cluster.
Finally, although our ActivID tokens work well, they are very expensive and the software (at ECMWF's end) is unreliable and troublesome to maintain. We would like to move away from ActivID in the post-BOND timeframe, so any access service should not be bound too tightly to it.
For these reasons, Teleport is a good choice, as it allows separation from ActivID, avoids a complex initiation for the user, avoids maintenance of SSH keys and their inherent security risks, avoids ECMWF running additional web services, and is single-hop client to server.
If you have any other product for us to look at, please make it known!
Understanding ecAccess
A user outside of ECMWF wishes to ssh to one of the Centre's clusters, batch farms, or workstations. This can be done by running:
ssh sy0@ecaccess.ecmwf.int
Since 2016 the ecAccess ssh module has required custom configuration on the ssh client end to enable known-insecure ciphers.
The replacement of this service will of course bring an up-to-date ssh implementation without this issue.
The user is prompted for a password, which happens to be the one-time code from an ActivID token.
ecAccess is not aware of the use of multi-factor authentication (ActivID token). It sees only a simple username and password and delegates authentication to another service.
After authenticating to ecAccess, the user is prompted for the destination host:
[cca-login,ecgate] ?
In fact, the user can enter any ECMWF server or workstation name.
The destination server or workstation must run the ecauth binary which is installed "setuid root" (so it can become any user).
ecauth receives the TCP/IP connection from ecAccess and spawns a shell as the original user (sy0, in this example).
It is important to know that the user authenticates to the ecAccess gateway only, not the destination server or workstation.
Understanding our SSH Proxy service
When servers or workstations inside the Centre wish to ssh to the Internet (not the RMDCN), we tell the client to use our SSH Proxy service.
The Proxy sits in the DMZ and allows transit of the TCP/IP connection from ssh client to server. It does not interrupt the encryption in any way.
The need for the SSH Proxy is mostly to support a network setup where the Centre is dual-homed on both RMDCN and Internet.
In the near future (BOND timeframe) the network will be redesigned and this need will go away, so all outgoing proxy services are to be retired.
Clients inside the Centre use the openssh ProxyCommand setting to direct the connection via our Proxy:
ProxyCommand /usr/bin/connect -H proxy.ecmwf.int:2222 %h %p
This is a commonly used behaviour in ssh, and in fact new openssh clients and servers support the ProxyJump setting, to simplify configuration even further.
It is important to know that our SSH Proxy is not authenticating users; it merely passes a TCP/IP stream.
Understanding Teleport
Teleport functions somewhat like a combination of ecAccess, and the SSH Proxy service, with additional features relating to role-based access control and single sign-on.
Users outside of the Centre configure their clients to use Teleport as a proxy service for the destination host. That is, it's a bit like the reverse of systems inside ECMWF connecting to the Internet.
Like ecAccess, Teleport can have its own binary installed on the destination server or workstation. However, this is optional, and standard openssh server works too.
Teleport is open source, hosted on GitHub, written in Go, and the Enterprise edition is licensed (at modest cost) to gain support and allow use of the single sign-on feature.
The notable difference between Teleport and our current services is that a specific command-line application, called tsh, is required to do the single sign-on function (once per day).
The single sign-on step will open a web browser and prompt the user for their username and password (from the token). This means if we migrate away from ActivID in the future then the Teleport service is not affected in any way, because login is delegated to the web service.
After login, a user's ssh-agent is populated with some SSH Certificates signed by the Teleport server, valid for a limited time (say, eight hours).
SSH clients present the certificates in a similar way to SSH Keys each time they login, and the certificates are validated by both the Teleport gateway and the destination host.
With Teleport, users are authenticated both at the gateway and at the destination host.