Pomerium

# Data Storage

# About

# Background

Pomerium keeps persistent state out of most components, but an identity-aware access proxy must maintain some data about every user's session. Historically, all user/session related data was stored in cookies, but this quickly became challenging.

  • Cookie and header limits would impact large organizations and some IdPs
  • SPAs would break when session cookies expired
  • No central visibility or management of existing sessions
  • Group membership was fixed from session creation
  • Slow initial authentication flow to fetch user data

To address these limitations, the Pomerium cache service runs a number of internal services responsible for maintaining data and state.

# Design

Internal to the cache service, the databroker is responsible for providing a stateful storage layer. Services which require high performance maintain a streaming local cache of the contents of the databroker, while others may call databroker in real time. Only the databroker is expected to maintain authoritative state.

# Persistence

At this time, most data stored by Pomerium is externally sourced and recoverable at startup (eg, group membership). The notable exception is user sessions. If the data hosted by the databroker is lost, users will need to log in through their IdP again at next session expiration.

To prevent early session loss in production deployments, persistent storage backends are available for configuration in the databroker. Use of these is strongly encouraged, but smaller or non-production deployments can make use of an in-memory storage layer if external dependencies are not practical or justifiable.

# Backends

Configuration options for each backend are detailed in cache configuration reference.

In all backends, Pomerium encrypts record values. This ensures security of all records at rest, regardless of data store capabilities. While this prevents many classes of attack vector, additional security measaures should always be taken to secure data in transit and minimize access to the backends themselves.

Please see Pomerium backend and upstream storage system documentation for best practices.

# In-Memory

  • Cache Service HA: no
  • Data Store HA: no
  • Data Persistence: no

The default storage backend for databroker is memory based. This backend provides easy deployment semantics but is not persistent or highly available. Running more than one cache instance configured for memory backed storage is not supported and will lead to non-deterministic behavior.

# Redis

  • Cache Service HA: yes
  • Data Store HA: yes
  • Data Persistence: yes

The Redis based backend supports multiple cache instances and persistence across restarts. We recommend a dedicated redis instance for Pomerium to provide the strongest security and performance guarantees.

# High Availability

Redis should be configured to provide high availability via replication and failover. Sentinal and cluster are not supported at this time.

# Security

Pomerium supports and strongly encourages ACL based authentication. To set up an ACL for pomerium, use the following template:

ACL setuser pomerium on >[MYPASSWORD] ~* +@all -@scripting -@dangerous -@admin -@connection

Pomerium supports and strongly encourages TLS support in Redis version 6. Both traditional and mutual TLS are supported.

Example secure configuration:

databroker_storage_connection_string: rediss://pomerium:MYSECUREPASSWORD@[HOST]:6379/
databroker_storage_cert_file: /tls/client.pem
databroker_storage_key_file: /tls/client.key
databroker_storage_ca_file: /tls/ca.pem

TIP

the second s in rediss is intentional and turns on TLS support

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