JMAP quota for uploads

Why?

As a james user, I want to set up a SaaS mail offer.

As such, I can't control my SaaS users, I have limited prior control on them, and little retorsion mechanisms. As such I cannot assert that they are good actors, as I would for instance for an on-premise deployment.

It turns out the JMAP uploads offer a simple binary store that is currently not limited by James. As such it would be trivial for an attacker to exploit this to store unlimited amount of data.

The way to counter such a threat is to set up a quota on users uploads.

How?

• Store the current size of total user uploads. Cassandra and memory implementation.
• Have a global limit (configured)
• Enforce the quota checks upon uploads. Upon upload deletion.
• Expose a webadmin API to see user quota usage for JMAP uploads.

Definition of done

JMAP integration tests rejecting offending over-quota uploads.