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Teleport

Architecture Introduction

This guide is for those looking for a deeper understanding of Teleport. If you are looking for hands-on instructions on how to set up Teleport for your team, check out the Admin Guide

Design Principles

Teleport was designed in accordance with the following principles:

  • Off the Shelf Security: Teleport does not re-implement any security primitives and uses well-established, popular implementations of the encryption and network protocols.
  • Open Standards: There is no security through obscurity. Teleport is fully compatible with existing and open standards and other software, including OpenSSH.
  • Cluster-Oriented Design: Teleport is built for managing clusters, not individual servers. In practice this means that hosts and Users have cluster memberships. Identity management and authorization happen on a cluster level.
  • Built for Teams: Teleport was created under the assumption of multiple teams operating on several disconnected clusters. Example use cases might be production-vs-staging environment, or a cluster-per-customer or cluster-per-application basis.

This doc introduces the basic concepts of Teleport so you can get started managing access!

Definitions

Here are definitions of the key concepts you will use in Teleport.

ConceptDescription
NodeA node is a "server", "host" or "computer". Users can create shell sessions to access nodes remotely.
UserA user represents someone (a person) or something (a machine) who can perform a set of operations on a node.
ClusterA cluster is a group of nodes that work together and can be considered a single system. Cluster nodes can create connections to each other, often over a private network. Cluster nodes often require TLS authentication to ensure that communication between nodes remains secure and comes from a trusted source.
Certificate Authority (CA)A Certificate Authority issues SSL certificates in the form of public/private keypairs.
Teleport NodeA Teleport Node is a regular node that is running the Teleport Node service. Teleport Nodes can be accessed by authorized Teleport Users. A Teleport Node is always considered a member of a Teleport Cluster, even if it's a single-node cluster.
Teleport UserA Teleport User represents someone who needs access to a Teleport Cluster. Users have stored usernames and passwords, and are mapped to OS users on each node. User data is stored locally or in an external store.
Teleport ClusterA Teleport Cluster is comprised of one or more nodes, each of which hold certificates signed by the same Auth Server CA. The CA cryptographically signs the certificate of a node, establishing cluster membership.
Teleport CATeleport operates two internal CAs as a function of the Auth service. One is used to sign User certificates and the other signs Node certificates. Each certificate is used to prove identity, cluster membership and manage access.

Teleport Services

Teleport uses three services which work together: Nodes, Auth, and Proxy.

Teleport Nodes are servers which can be accessed remotely with SSH. The Teleport Node service runs on a machine and is similar to the sshd daemon you may be familiar with. Users can log in to a Teleport Node with all of the following clients:

Teleport Auth authenticates Users and Nodes, authorizes User access to Nodes, and acts as a CA by signing certificates issued to Users and Nodes.

Teleport Proxy forwards User credentials to the Auth Service, creates connections to a requested Node after successful authentication, and serves a Web UI.

Basic Architecture Overview

The numbers correspond to the steps needed to connect a client to a node. These steps are explained below the diagram.

Caution
The teleport daemon calls services "roles" in the CLI client. The --roles flag has no relationship to concept of User Roles or permissions.
Teleport Overview
  1. Initiate Client Connection
  2. Authenticate Client
  3. Connect to Node
  4. Authorize Client Access to Node
Tip
In the diagram above we show each Teleport service separately for clarity, but Teleport services do not have to run on separate nodes. Teleport can be run as a binary on a single-node cluster with no external storage backend. We demonstrate this minimal setup in the Getting Started Guide.

Detailed Architecture Overview

Here is a detailed diagram of a Teleport Cluster.

The numbers correspond to the steps needed to connect a client to a node. These steps are explained in detail below the diagram.

Teleport Everything
Caution
The Teleport Admin tool, tctl , must be physically present on the same machine where Teleport Auth is running. Adding new nodes or inviting new users to the cluster is only possible using this tool.

1: Initiate Client Connection

Client offers certificate

The client tries to establish an SSH connection to a proxy using the CLI interface or a web browser. When establishing a connection, the client offers its certificate. Clients must always connect through a proxy for two reasons:

  1. Individual nodes may not always be reachable from outside a secure network.

  2. Proxies always record SSH sessions and keep track of active user sessions.

    This makes it possible for an SSH user to see if someone else is connected to a node she is about to work on.

2: Authenticate Client Certificate

Client offers valid certificate

The proxy checks if the submitted certificate has been previously signed by the auth server.

Client obtains new certificate

If there was no certificate previously offered (first time login) or if the certificate has expired, the proxy denies the connection and asks the client to login interactively using a password and a 2nd factor if enabled.

Teleport supports Google Authenticator, Authy, or another TOTP generator. The password + 2nd factor are submitted to a proxy via HTTPS, therefore it is critical for a secure configuration of Teleport to install a proper HTTPS certificate on a proxy.

Warning
Do not use self-signed SSL/HTTPS certificates in production!

If the credentials are correct, the auth server generates and signs a new certificate and returns it to the client via the proxy. The client stores this certificate and will use it for subsequent logins. The certificate will automatically expire after 12 hours by default. This TTL can be configured to another value by the cluster administrator.

3: Lookup Node

Node lookup

At this step, the proxy tries to locate the requested node in a cluster. There are three lookup mechanisms a proxy uses to find the node's IP address:

  1. Uses DNS to resolve the name requested by the client.
  2. Asks the Auth Server if there is a Node registered with this nodename .
  3. Asks the Auth Server to find a node (or nodes) with a label that matches the requested name.

If the node is located, the proxy establishes the connection between the client and the requested node. The destination node then begins recording the session, sending the session history to the auth server to be stored.

Note
Teleport may also be configured to have the session recording occur on the proxy, see Audit Log for more information.

4: Authenticate Node Certificate

Node Membership Authentication

When the node receives a connection request, it checks with the Auth Server to validate the node's certificate and validate the Node's cluster membership.

If the node certificate is valid, the node is allowed to access the Auth Server API which provides access to information about nodes and users in the cluster.

5: Grant User Node Access

User Granted Node Access

The node requests the Auth Server to provide a list of OS users (user mappings) for the connecting client, to make sure the client is authorized to use the requested OS login.

Finally, the client is authorized to create an SSH connection to a node.

Proxy Connection Established

Teleport CLI Tools

Teleport offers two command line tools. tsh is a client tool used by the end users, while tctl is used for cluster administration.

TSH

tsh is similar in nature to OpenSSH ssh or scp. In fact, it has subcommands named after them so you can call:

$ tsh --proxy=p ssh -p 1522 [email protected]
$ tsh --proxy=p scp -P example.txt [email protected]/destination/dir

Unlike ssh, tsh is very opinionated about authentication: it always uses auto-expiring certificates and it always connects to Teleport nodes via a proxy.

When tsh logs in, the auto-expiring certificate is stored in ~/.tsh and is valid for 12 hours by default, unless you specify another interval via the --ttl flag (capped by the server-side configuration).

You can learn more about tsh in the User Manual.

TCTL

tctl is used to administer a Teleport cluster. It connects to the Auth server listening on 127.0.0.1 and allows a cluster administrator to manage nodes and users in the cluster.

tctl is also a tool which can be used to modify the dynamic configuration of the cluster, like creating new user roles or connecting trusted clusters.

You can learn more about tctl in the Admin Manual.

Next Steps

Read the rest of the Architecture Guides:

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