Can a Unified Push push server see/read notifications?
Can a Unified Push push server see/read notifications?
Yes, I believe all the messages are in plain text, and it's up to the server not to log it.
It is possible to e2ee the message content yourself tho.
Edit: it looks like ntfy.sh specifically keeps messages cached in memory for a few hours befor discarding them. https://docs.ntfy.sh/config/
Isn't this contradicting the Unified Push spec? It states:
Push message: This is an array of bytes (ByteArray) sent by the application server to the push server. The distributor sends this message to the end user application. It MUST be the raw POST data received by the push server (or the rewrite proxy if present). The message MUST be an encrypted content that follows RFC8291. Its size is between 1 and 4096 bytes (inclusive). [1]
References
- Unified Push spec. Unified Push. Accessed: 2024-11-22T05:07Z. https://unifiedpush.org/developers/spec/android/
- "Developers/Specifications/Android". §"Resources"
- Unified Push spec. Unified Push. Accessed: 2024-11-22T05:07Z. https://unifiedpush.org/developers/spec/android/
Yes, they can read the data. But apps like Molly (Signal Fork) send encrypted notifications. So, the time and some other metadata may be read by the server, but the content and contact won't be visible in plain text.
For Signal/Molly, it's less that the notification is encrypted as I understand it. It's more the notification content is just "Hey! Stuff happened" for Signal. The app then reaches out directly to the Signal servers to see what's new. So the message content is never sent via the push notification service (UnifiedPush or Google's service).
Yes, they can read the data.
Isn't this contradicting the Unified Push spec? It states:
Push message: This is an array of bytes (ByteArray) sent by the application server to the push server. The distributor sends this message to the end user application. It MUST be the raw POST data received by the push server (or the rewrite proxy if present). The message MUST be an encrypted content that follows RFC8291. Its size is between 1 and 4096 bytes (inclusive). [1]
References
- Unified Push spec. Unified Push. Accessed: 2024-11-22T05:07Z. https://unifiedpush.org/developers/spec/android/
- "Developers/Specifications/Android". §"Resources"
- Unified Push spec. Unified Push. Accessed: 2024-11-22T05:07Z. https://unifiedpush.org/developers/spec/android/
I think a lot of comments have missed that ntfy.sh does not use UnifiedPush, the ntfy server is a UnifiedPush provider and the ntfy app is a UnifiedPush distributor.
The app that wants to provide the notifications would then be said to use UnifiedPush, right?
I never used it, but I would assume yes after reading the frontpage and the doc. At no point there is a PSK set between sender and reciever, not I see any signs for key exchange between devices.
This is not a definitive answer though as I didn't read the source code of Nfty, nor the UnifiedPush spec.
Regarding encryption of the push message, from https://unifiedpush.org/developers/spec/android/ :
Push message: This is an array of bytes (ByteArray) sent by the application server to the push server. The distributor sends this message to the end user application. It MUST be the raw POST data received by the push server (or the rewrite proxy if present). The message MUST be an encrypted content that follows RFC8291. Its size is between 1 and 4096 bytes (inclusive).
What's interesting, and is confusing me about this, is that Ntfy does not adhere to this [1]. I'm not sure how this can be.
References
- "End-to-end encryption (E2E) between clients (Android app, CLI, web app)". binwiederhier. ntfy/binwiederhier. GitHub. Published: 2021-12-29T02:07:36Z. Accessed: 2024-11-22T05:04Z. https://github.com/binwiederhier/ntfy/issues/69.
I still want to know if MQTT already did this & UnifiedPush is just a startup trying to reimplement the same concept
IMHO UnifiedPush is just a poor re-implementation of WebPush which is an open and distributed standard that supports (and in the browser requires, so support is universal) E2EE.
UnifiedPush would be better as a framework for WebPush providers and a client API. But use the same protocol and backends as WebPush (as how to get a WebPush endpoint is defined as a JS API in browsers, would would need to be adapted).