Add senderHmac and shouldPush to MessageV2
#519
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src/keystore/InMemoryKeystore.ts
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| encrypted: ciphertext, | ||
| senderHmac: await generateHmacSignature( | ||
| keyMaterial, | ||
| new TextEncoder().encode(contentTopic), |
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For the hkdf salt/domain, I would suggest we also include some kind of time-dependent value, such as the number of months since the Unix epoch: xmtp/XIPs#35 (comment). This ensures that we have automatic key rotation
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My worry about the time-dependent value is the complexity of keeping the push server up to date with the correct keys. If we had it roll over at 12am on the first of the month UTC, we'd guarantee that push notifications would not be correctly filtered for some time at the start of each month. Basically would be broken until the app starts up again, which requires integrators to have some sort of wakeup scheduled to refresh keys if they aren't comfortable with extended breakages each month. That's going to be a bigger ask for integrators.
The way to fix this is to have each user pass in not just the current month's key but also the next N months keys for each topic. That's fine, but it makes things more complicated from the push server side. Need to handle expirations etc. Clients would also need to be aware of their last upload time and periodically refresh.
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Summary of discussion:
- We can pass (prev_hmac_key, current_hmac_key, next_hmac_key). That solves any roll over issues.
- We can expose an API that maps (list of topics to subscribe pushes for) -> (hmac keys for topics). Integrators simply need to call it any time the topic list changes, as well as periodically, and upload it if it changes. This only needs to happen every 30 days at most.
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MessageV2senderHmac and shouldPush to MessageV2
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🎉 This PR is included in version 11.4.0-beta.1 🎉 The release is available on: Your semantic-release bot 📦🚀 |
context: https://community.xmtp.org/t/xip-35-message-sender-identifier-in-topic/509/2
in this PR:
shouldPushtoContentCodectypeshouldPushmethod toTextCodecandCompositeCodecsenderHmacandshouldPushtoMessageV2getV2ConversationHmacKeystoInMemoryKeystoreto retrieve conversation topics and their associated HMAC keysTODO: