[release-v2.0] main: Use backported mixing updates. #3458
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rand.Duration may not be called with a negative or zero upper bound, but this was seen to occur in (*Client).prDelay(). Two notable possible bugs stood out. First, if sendBefore is exactly equal to now, then it will not be incremented by another epoch duration, leading to a potential invalid rand.Duration parameter. This is corrected by also checking for the times equaling exactly. Second, time.Until() causes an additional call to time.Now(), which we have already fetched and all calculations must be based on it. If sendBefore.Sub(now) is an extremely small value, it is possible that time.Until(sendBefore) now returns a small negative or zero duration. This is corrected by replacing the time.Until call with sendBefore.Sub(now).
If the csppsolver process has unexpectedly exited after successful startup (due to crash, signal, oom-killer, etc.) unset the PR flag indicating root solving support for future mixes. Wait for other peers to publish roots (if any do), otherwise our peer will be (correctly) blamed for not publishing roots.
The purpose of the SR (slot reservation) mix is to determine unique anonymous slot positions for the DC-net (xor) mix. However, there was a missing check by non-root-solving peers that the published roots are in the proper order. This could result in a malicious actor publishing roots in a different order, disrupting mixes by causing non-root-solving peers to unknowingly perform the DC-net in the wrong slots, and causing the wrong peers to be blamed for disrupting the mix. Prevent this by requiring roots to be sorted before slots are discovered. This also matches the root-sorting that occurred in the older client-server design. This change is not compatible with previous mixclient versions, as the DC-net mix would occur with peers writing messages into different slots. The pairing version included in PR messages is updated to reflect this.
When a RS (reveal secrets) message was published, the mixpool Receive method would immediately return, and blame assignment was immediately run. This created a logic race (due to message propagation over the network) where not all peers would run blame assignment with all currently-published messages, and different peers would blame different sets of peers for missing messages. Correct this by modifying the Receive method to not return ErrSecretsRevealed until the total number of expected messages have been received first.
This updates the 2.0 release branch to use the latest version of the mixing module which includes various fixes to make decentralized mixing more robust against misbehaving peers. All participants will need to update to the latest version to achieve the maximum anonymity set. In particular, the following updated module version is used: - github.com/decred/dcrd/[email protected]
jrick
approved these changes
Nov 11, 2024
davecgh
added
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mix pairing version change
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This updates the 2.0 release branch to use the latest version of the
mixingmodule which includes various fixes to make decentralized mixing more robust against misbehaving peers. All participants will need to update to the latest version to achieve the maximum anonymity set.In particular, the following updated module version is used:
Note that it also cherry picks all of the commits included in updates to the
mixingmodule to ensure they are also included in the release branch even though it is not strictly necessary sincego.modhas been updated to require the new release and thus will pull in the new code. However, from past experience, not having code backported to modules available in the release branch too leads to headaches for devs building from source in their local workspace with overrides such as those ingo.work.The following PRs are included: