Session Storage

Sessions allow a user's authentication to be tracked between multiple HTTP requests to a service.

The OAuth2 Proxy uses a Cookie to track user sessions and will store the session data in one of the available session storage backends.

At present the available backends are (as passed to --session-store-type):

• cookie (default)
• redis

Cookie Storage

The Cookie storage backend is the default backend implementation and has been used in the OAuth2 Proxy historically.

With the Cookie storage backend, all session information is stored in client side cookies and transferred with each and every request.

The following should be known when using this implementation:

• Since all state is stored client side, this storage backend means that the OAuth2 Proxy is completely stateless
• Cookies are signed server side to prevent modification client-side
• It is mandatory to set a cookie-secret which will ensure data is encrypted within the cookie data.
• Since multiple requests can be made concurrently to the OAuth2 Proxy, this session implementation cannot lock sessions and while updating and refreshing sessions, there can be conflicts which force users to re-authenticate

Redis Storage

The Redis Storage backend stores encrypted sessions in redis. Instead of sending all the information back the client for storage, as in the Cookie storage, a ticket is sent back to the user as the cookie value instead.

A ticket is composed as the following:

{CookieName}-{ticketID}.{secret}

Where:

• The CookieName is the OAuth2 cookie name (_oauth2_proxy by default)
• The ticketID is a 128-bit random number, hex-encoded
• The secret is a 128-bit random number, base64url encoded (no padding). The secret is unique for every session.
• The pair of {CookieName}-{ticketID} comprises a ticket handle, and thus, the redis key to which the session is stored. The encoded session is encrypted with the secret and stored in redis via the SETEX command.

Encrypting every session uniquely protects the refresh/access/id tokens stored in the session from disclosure. Additionally, the browser only has to send a short Cookie with every request and not the whole JWT, which can get quite big.

Two settings are used to configure the OAuth2 Proxy cookie lifetime:

--cookie-refresh duration refresh the cookie after this duration; 0 to disable --cookie-expire duration expire timeframe for cookie 168h0m0s

The "cookie-expire" value should be equal to the lifetime of the Refresh-Token that is issued by the OAuth2 authorization server. If it expires earlier and is deleted by the browser, OAuth2 Proxy cannot find the stored Refresh-Tokens in Redis and thus cannot start the refresh flow to get a new Access-Token. If it is longer, it might be that the old Refresh-Token will be found in Redis but has already expired.

The "cookie-refresh" value controls when OAuth2 Proxy tries to refresh an Access-Token. If it is set to "0", the Access-Token will never be refreshed, even if it is already expired and a valid Refresh-Token is available. If set, OAuth2-Proxy will refresh the Access-Token after this many seconds whether it is still valid or not. According to the official OAuth2.0 specification Access-Tokens are not required to follow a specific format. Therefore OAuth2-Proxy cannot check for any expiry date without an introspection endpoint. If an Access-Token expires and you have not set a corresponding "cookie-refresh" value, you will likely encounter expiry issues.

Caveat: It can happen that the Access-Token is valid for e.g. "1m" and a request happens after exactly "59s". It would pass OAuth2 Proxy and be forwarded to the backend but is just expired when the backend tries to validate it. This is especially relevant if the backend uses the JWT to make requests to other backends. For this reason, it's advised to set the cookie-refresh a couple of seconds less than the Access-Token lifespan.

Recommended settings:

• cookie_refresh := Access-Token lifespan - 1m
• cookie_expire := Refresh-Token lifespan (i.e. Keycloak client_session_idle)

Usage

When using the redis store, specify --session-store-type=redis as well as the Redis connection URL, via --redis-connection-url=redis://host[:port][/db-number].

You may also configure the store for Redis Sentinel. In this case, you will want to use the --redis-use-sentinel=true flag, as well as configure the flags --redis-sentinel-master-name and --redis-sentinel-connection-urls appropriately.

Redis Cluster is available to be the backend store as well. To leverage it, you will need to set the --redis-use-cluster=true flag, and configure the flags --redis-cluster-connection-urls appropriately.

Note that flags --redis-use-sentinel=true and --redis-use-cluster=true are mutually exclusive.

Note, if Redis timeout option is set to non-zero, the --redis-connection-idle-timeout must be less than Redis timeout option. For example: if either redis.conf includes timeout 15 or using CONFIG SET timeout 15 the --redis-connection-idle-timeout must be at least --redis-connection-idle-timeout=14