fix(consensus): Check that Zebra's state contains the social consensus chain on startup

[teor2345]

Motivation

Zebra does not check that the state has followed the correct chain, but this is a new consensus requirement on mainnet.

Closes #5912

Specifications

A network upgrade is settled on a given network when there is a social consensus that it has activated with a given activation block hash. A full validator that potentially risks Mainnet funds or displays Mainnet transaction information to a user MUST do so only for a block chain that includes the activation block of the most recent settled network upgrade

https://zips.z.cash/protocol/protocol.pdf#blockchain

Complex Code or Requirements

This PR adds another short startup task using the existing concurrent task framework and event loop.

Solution

• Validate existing state block hashes at startup
  • Make Request::BestChainBlockHash redirect to the ReadStateService
• Monitor state block hash checkpoint task in the start command
• Re-write the checkpoint_sync config docs based on the latest consensus rules

Unrelated cleanups:

• Allow missing docs directly on derived error types

Testing

New tests:

• check that this code is active in the existing cached state tests
• check that it fails when the checkpoints don't match the previous cached state (and succeeds when they do)

I also did full and partial syncs locally, and they passed. (I had some unrelated issues with syncing due to proof errors, likely caused by disk corruption.)

Changelog

Added security and deprecation notes in this PR.

Review

This PR's code is ready for review. It is not on the critical path.

Reviewer Checklist

• Will the PR name make sense to users?
  • Does it need extra CHANGELOG info? (new features, breaking changes, large changes)
• Are the PR labels correct?
• Does the code do what the ticket and PR says?
  • Does it change concurrent code, unsafe code, or consensus rules?
• How do you know it works? Does it have tests?

Follow Up

• Require NU5 checkpoints regardless of zebrad.toml settings #6178

[teor2345]

This new task takes about one second on my machine, about the same time as validating the Zcash parameters:

2023-02-15T02:51:47.494988Z  INFO {zebrad="f5dca6c" net="Main"}: zebrad::commands::start: initializing verifiers
2023-02-15T02:51:47.494999Z  INFO {zebrad="f5dca6c" net="Main"}:crawl_and_dial{new_peer_interval=61s}: zebra_network::peer_set::initialize: starting the peer address crawler crawl_new_peer_interval=61s outbound_connections=18
2023-02-15T02:51:47.495024Z  INFO {zebrad="f5dca6c" net="Main"}:init{config=Config { checkpoint_sync: true, debug_skip_parameter_preload: false } network=Mainnet debug_skip_parameter_preload=false}: zebra_consensus::chain: starting state checkpoint validation...
2023-02-15T02:51:47.495058Z  INFO {zebrad="f5dca6c" net="Main"}:init{config=Config { checkpoint_sync: true, debug_skip_parameter_preload: false } network=Mainnet debug_skip_parameter_preload=false}: zebra_consensus::primitives::groth16::params: checking and loading Zcash Sapling and Sprout parameters
2023-02-15T02:51:47.498429Z  INFO {zebrad="f5dca6c" net="Main"}:init{config=Config { checkpoint_sync: true, debug_skip_parameter_preload: false } network=Mainnet debug_skip_parameter_preload=false}: zebra_consensus::chain: initializing chain verifier tip=Some((Height(1984325), block::Hash("00000000011c7c1efffc288d30fae56d9f3a82ad62c662e81c63c3c1984d755d"))) max_checkpoint_height=Height(1965904)
2023-02-15T02:51:47.498444Z  INFO {zebrad="f5dca6c" net="Main"}: zebrad::commands::start: initializing syncer
2023-02-15T02:51:47.498459Z  INFO {zebrad="f5dca6c" net="Main"}: zebrad::commands::start: initializing mempool
2023-02-15T02:51:47.498470Z  INFO {zebrad="f5dca6c" net="Main"}: zebra_rpc::server: Trying to open RPC endpoint at 0.0.0.0:28232...
2023-02-15T02:51:47.515981Z  INFO {zebrad="f5dca6c" net="Main"}: zebra_rpc::server: Opened RPC endpoint at 0.0.0.0:28232
2023-02-15T02:51:47.516147Z  INFO {zebrad="f5dca6c" net="Main"}: zebrad::commands::start: spawned initial Zebra tasks
2023-02-15T02:51:47.516252Z  INFO {zebrad="f5dca6c" net="Main"}: zebrad::components::mempool::crawler: initializing mempool crawler task
2023-02-15T02:51:47.516252Z  INFO {zebrad="f5dca6c" net="Main"}: zebrad::components::sync::gossip: initializing block gossip task
2023-02-15T02:51:47.516269Z  INFO {zebrad="f5dca6c" net="Main"}: zebrad::components::mempool::gossip: initializing transaction gossip task
2023-02-15T02:51:47.516268Z  INFO {zebrad="f5dca6c" net="Main"}: zebra_state::config: finished old database version cleanup task
2023-02-15T02:51:47.516272Z  INFO {zebrad="f5dca6c" net="Main"}: zebrad::components::mempool::queue_checker::initializing mempool queue checker task
2023-02-15T02:51:47.519140Z  INFO {zebrad="f5dca6c" net="Main"}:sync:try_to_sync: zebrad::components::sync::starting sync, obtaining new tips state_tip=Some(Height(1984325))
2023-02-15T02:51:47.520915Z  INFO {zebrad="f5dca6c" net="Main"}: zebrad::components::sync::progress: estimated progress to chain tip sync_percent=99.995% current_height=Height(1984325) network_upgrade=Nu5 remaining_sync_blocks=109 time_since_last_state_block=0s
2023-02-15T02:51:47.973306Z  INFO {zebrad="f5dca6c" net="Main"}:init{config=Config { checkpoint_sync: true, debug_skip_parameter_preload: false } network=Mainnet debug_skip_parameter_preload=false}: zebra_consensus::chain: finished state checkpoint validation
2023-02-15T02:51:48.466416Z  INFO {zebrad="f5dca6c" net="Main"}:init{config=Config { checkpoint_sync: true, debug_skip_parameter_preload: false } network=Mainnet debug_skip_parameter_preload=false}: zebra_consensus::primitives::groth16::params: Zcash Sapling and Sprout parameters downloaded and/or verified

[codecov]

Codecov Report

Merging #6163 (eb59780) into main (cbc4b44) will increase coverage by 0.10%.
The diff coverage is 50.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6163      +/-   ##
==========================================
+ Coverage   77.96%   78.07%   +0.10%     
==========================================
  Files         304      304              
  Lines       39197    39251      +54     
==========================================
+ Hits        30560    30644      +84     
+ Misses       8637     8607      -30     

[arya2]

This is looking good!

[teor2345]

Coverage failed downloading Zcash parameters:

thread 'main' panicked at 'error downloading Sapling parameter files after 3 retries. IoError(Custom { kind: InvalidData, error: "sapling-spend.params failed validation:\nexpected: 8270785a1a0d0bc77196f000ee6d221c9c9894f55307bd9357c3f0105d31ca63991ab91324160d8f53e2bbd3c2633a6eb8bdf5205d822e7f3f73edac51b2b70c hashing 47958396 bytes,\nactual: 786a02f742015903c6c6fd852552d272912f4740e15847618a86e217f71f5419d25e1031afee585313896444934eb04b903a685b1448b755d56f701afe9be2ce hashing 0 bytes from "https://download.z.cash/downloads/sapling-spend.params.part.1 + [https://download.z.cash/downloads/sapling-spend.params.part.2](https://download.z.cash/downloads/sapling-spend.params.part.2/)"" })

https://github.com/ZcashFoundation/zebra/actions/runs/4192197818/jobs/7267473489#step:9:18

It's possible the download server is very slow right now.

[arya2]

There are "missing documentation for a struct field" warnings in the BackgroundTaskHandles, but this looks perfect otherwise!

[teor2345]

There are "missing documentation for a struct field" warnings in the BackgroundTaskHandles, but this looks perfect otherwise!

Oops, that should be fixed now!

[arya2]

Looks great! Thank you!

[mpguerra]

@Mergifyio refresh

[mergify]

refresh

✅ Pull request refreshed

[teor2345]

@Mergifyio update

[mergify]

update

✅ Branch has been successfully updated

[teor2345]

Failed due to bug #5940, that fix is in the main branch now.

This approval should have been dismissed by the main branch update, this is a bug in GitHub's latest pusher setting.

[teor2345]

@arya2 this just needs a re-approval after a main branch merge.

[teor2345]

@Mergifyio refresh

[mergify]

refresh

✅ Pull request refreshed

[teor2345]

Unrelated failure in the getblocktemplate tests, I'll open another ticket.

[teor2345]

@Mergifyio refresh

[mergify]

refresh

✅ Pull request refreshed