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Compact committees root uses incorrect start shard #1315

michaelsproul opened this issue Jul 25, 2019 · 2 comments

Compact committees root uses incorrect start shard #1315

michaelsproul opened this issue Jul 25, 2019 · 2 comments


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@michaelsproul michaelsproul commented Jul 25, 2019

In the process_final_updates function we increment the start shard by the shard delta before computing the compact committees root. This is problematic because get_compact_committees_root calls get_start_shard (alone and via get_crosslink_committee) to work out the start shard and committees for the next epoch. The get_start_shard function adds the shard delta to the state's already-incremented start shard, resulting in a start shard for the "next epoch" which has been double incremented. This shard is then used to calculate committees for the next epoch, yielding incorrect results (the committees it computes are not the committees that will be computed once the next epoch actually comes around).

For example, with the minimal config that's used for the sanity tests, if we begin with the start shard equal to 0, it will get incremented to 7 as part of process_final_updates, and then when get_compact_committees_root runs it will incorrectly see the next epoch's start shard as 6.

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@djrtwo djrtwo commented Jul 25, 2019

Indeed! fixing

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@protolambda protolambda commented Jul 25, 2019

Fixed in #1319

paulhauner added a commit to sigp/lighthouse that referenced this issue Jul 30, 2019
* types: first updates for v0.8

* state_processing: epoch processing v0.8.0

* state_processing: block processing v0.8.0

* tree_hash_derive: support generics in SignedRoot

* types v0.8: update to use ssz_types

* state_processing v0.8: use ssz_types

* ssz_types: add bitwise methods and from_elem

* types: fix v0.8 FIXMEs

* ssz_types: add bitfield shift_up

* ssz_types: iterators and DerefMut for VariableList

* types,state_processing: use VariableList

* ssz_types: fix BitVector Decode impl

Fixed a typo in the implementation of ssz::Decode for BitVector, which caused it
to be considered variable length!

* types: fix test modules for v0.8 update

* types: remove slow type-level arithmetic

* state_processing: fix tests for v0.8

* op_pool: update for v0.8

* ssz_types: Bitfield difference length-independent

Allow computing the difference of two bitfields of different lengths.

* Implement compact committee support

* epoch_processing: committee & active index roots

* state_processing: genesis state builder v0.8

* state_processing: implement v0.8.1

* Further improve tree_hash

* Strip examples, tests from cached_tree_hash

* Update TreeHash, un-impl CachedTreeHash

* Update bitfield TreeHash, un-impl CachedTreeHash

* Update FixedLenVec TreeHash, unimpl CachedTreeHash

* Update update tree_hash_derive for new TreeHash

* Fix TreeHash, un-impl CachedTreeHash for ssz_types

* Remove fixed_len_vec, ssz benches

SSZ benches relied upon fixed_len_vec -- it is easier to just delete
them and rebuild them later (when necessary)

* Remove boolean_bitfield crate

* Fix fake_crypto BLS compile errors

* Update ef_tests for new v.8 type params

* Update ef_tests submodule to v0.8.1 tag

* Make fixes to support parsing ssz ef_tests

* `compact_committee...` to `compact_committees...`

* Derive more traits for `CompactCommittee`

* Flip bitfield byte-endianness

* Fix tree_hash for bitfields

* Modify CLI output for ef_tests

* Bump ssz crate version

* Update ssz_types doc comment

* Del cached tree hash tests from ssz_static tests

* Tidy SSZ dependencies

* Rename ssz_types crate to eth2_ssz_types

* validator_client: update for v0.8

* ssz_types: update union/difference for bit order swap

* beacon_node: update for v0.8, EthSpec

* types: disable cached tree hash, update min spec

* state_processing: fix slot bug in committee update

* tests: temporarily disable fork choice harness test

See #447

* committee cache: prevent out-of-bounds access

In the case where we tried to access the committee of a shard that didn't have a committee in the
current epoch, we were accessing elements beyond the end of the shuffling vector and panicking! This
commit adds a check to make the failure safe and explicit.

* fix bug in get_indexed_attestation and simplify

There was a bug in our implementation of get_indexed_attestation whereby
incorrect "committee indices" were used to index into the custody bitfield. The
bug was only observable in the case where some bits of the custody bitfield were
set to 1. The implementation has been simplified to remove the bug, and a test

* state_proc: workaround for compact committees bug


* v0.8: updates to make the EF tests pass

* Remove redundant max operation checks.
* Always supply both messages when checking attestation signatures -- allowing
  verification of an attestation with no signatures.
* Swap the order of the fork and domain constant in `get_domain`, to match
  the spec.

* rustfmt

* ef_tests: add new epoch processing tests

* Integrate v0.8 into master (compiles)

* Remove unused crates, fix clippy lints

* Replace v0.6.3 tags w/ v0.8.1

* Remove old comment

* Ensure lmd ghost tests only run in release

* Update readme
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