Accept high version numbers in non-overwinter transactions

[conradoplg]

Version

zebra-chain v1.0.0-alpha.8 commit 227757a

Platform

Linux 5.8.0-53-generic #60~20.04.1-Ubuntu SMP Thu May 6 09:52:46 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

Description

Zebra does not accept high version numbers in pre-overwinter transactions.

I tried this:

Deserialize transaction from https://github.com/zcash/zcash/blob/master/src/test/data/sighash.json (e.g. the first one)

I expected to see this happen: the transaction to be successfully deserialized

Instead, this happened: parse error: bad tx header

See section 7.1 of the spec:

Version constraints apply to the effectiveVersion, which is equal to min(2, version) when fOverwintered = 0 and
to version otherwise.

Solution

• Add a u32 version field to Transaction::V2
• Serialize and deserialize it
• Add round-trip serialization tests with the test vectors that are currently failing

Commands

N/A

Logs

N/A

[teor2345]

In practice this issue never actually happened on the Mainnet or Testnet chain, so it's a low-priority fix. (Unless it's blocking other necessary work.)

[conradoplg]

We don't need this since we checkpoint on Canopy and no existing transactions has high version numbers.