Encryption

This topic isn't crucial to understanding Concourse; if you're just getting started and have finished the Installing section, you may want to first move on to Using Concourse.

Automating everything means authorizing something to automate many things. This makes CI systems a high-risk target for security leaks.

Concourse pipelines are loaded with credentials: resources are configured with private keys, tasks are given credentials to servers they integrate against via params, etc. etc. etc. If someone gets their hands on your config, they have access to everything.

To mitigate this, Concourse supports encrypting sensitive information before it reaches the database. This way the plaintext credentials only exist in memory for as long as they need to, and if someone gains access to your database, they can't so easily gain the keys to the kingdom.

We strongly encourage anyone running Concourse to configure encryption. Going further, it's best to have Concourse not store the credentials in the first place, in which case you may want to configure credential management as well.

What's encrypted?

The following values are expected to contain credentials, and so will be encrypted:

  • Resource sources, as they often contain private keys and other credentials for writing to (or simply granting access to) the resource.

  • Resource type sources, for the same reason as above, though this is probably a less common use case.

  • Task step params, as they are often used to configure access to e.g. an external deployment that the task is integrating with.

  • Put step params and get step params are also encrypted, even though they rarely should contain credentials (they're usually in source).

  • Team auth configurations, as they often contain things like GitHub or other oAuth client secrets.

Note that the actual implementation encrypts things in a more heavy-handed way than the above list implies. For example, pipeline configs are actually encrypted as one large blob.

Notably, the following things are NOT encrypted:

  • Build logs. If your jobs are outputting credentials, encryption won't help you. We have chosen not to tackle this initially as it would introduce a performance burden for what is not as much of an obvious win.

  • Resource versions. These should never contain credentials, and are often meaningless on their own.

  • Resource metadata. These are visible to anyone if your pipeline is exposed, and should never contain credentials.

  • Pipeline names, job names, etc. - anything else that is not a high-risk target for credential leakage, as opposed to regular information leaks.

    Resources and jobs in particular exist in their own tables, with their names in plaintext, and only their config encrypted. In this way, names are not protected, even though the pipeline config itself is also stored as one big encrypted blob.

Enabling Encryption

To enable encryption, you'll just need to come up with a 16 or 32-byte random character sequence and configure it as --encryption-key flag to the web command. For BOSH, this is the encryption_key property.

On startup, the ATC will encrypt all existing plaintext data, and any new data being written will be encrypted before it's sent over the network to the database.

The initial bulk encryption shouldn't take too long, but it will scale linearly with the amount of data that you have, and if another ATC is running it'll suddenly not be able to read the data until it's also given the key. So, expect some downtime.

Rotating the Encryption Key

To swap out the encryption key, you'll need to pass the previous key as --old-encryption-key (or old_encryption_key), and the new key as --encryption-key (or encryption_key).

On startup, the ATC will decrypt all existing data and re-encrypt it with the new key, in one go. If it encounters a row which is already encrypted with the new key, it will continue on (as may be the case when restarting with the flags again, or if the ATC died in the middle of rotating).

If the ATC encounters a row which cannot be decrypted with neither the old key nor the new one, it will log loudly and fail to start, telling you which row it choked on. This data must be dealt with in some way, either by re-configuring the key the row was encrypted with as the old key, or manually performing database surgery to remove the offending row. Hopefully this doesn't happen to you!

Disabling Encryption

To opt out of encryption entirely (I'm sure you have your reasons), simply pass --old-encryption-key (or old_encryption_key) alone. With no new encryption key, the ATC will decrypt all existing data on start.