x/oracle: Lack of prioritization for oracle messages

[alexanderbez]

From ToB Audit

Description

Oracle messages use the same mechanism as other transactions to be included in a block.
If the network is highly congested they may be not included in blocks. The only mechanism
to prevent this would be an increased fee paid, which is a suboptimal solution that may fail.
Three example mechanisms solving the problem of prioritization of transactions important
for the functioning of the system are:
● A priority argument returned by custom CheckTx implementation, introduced by
Tendermint in version 0.35.
● Reimplementation of part of the tendermint engine. Done by Terra Money.
● Substrate’s dispatch classes. The Substrate allows developers to mark transaction
types as either normal, operational, and mandatory.

Exploit Scenario

The Umee network is congested. Validators send their exchange rates votes in the last
possible block but they cannot update exchange rates. Attackers exploit this situation to
drain the network from tokens.

Recommendations

Short term, prioritize oracle messages using a custom CheckTx method. This will help
prevent a situation when an oracle misses their vote due to it not being included in a block.

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No major actionable items here. Once we update to SDK v0.46, we need to modify/replace the Tx priority AnteHandler middleware, s.t. that txs with a single oracle message have highest-ish priority.

[alexanderbez]

We're blocked on this until SDK v0.46 is released.

[adamewozniak]

Pretty sure this was closed by #1217, @robert-zaremba please verify

[robert-zaremba]

No, i need to do one more update