process_attestation: Validate epoch before using it #1996
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
`data.target.epoch` is used to count the active validator set. Because `get_committee_count_per_slot` is extremely inefficient the way the spec is written, clients cache it, or the underlying active validator set. Performing the checks in the given order leads to a (very unlikely) security issue where the a cold and above all, distant value may get used which may be costly - reordering the checks brings the value into a more reasonable range before using it.
|
Notably, this is predominantly an issue for implementations - the outcome, even if processed in the order given by the spec, remains the same. |
protolambda
approved these changes
Jul 24, 2020
There was a problem hiding this comment.
Thanks! Looks good, not a breaking change, so I think it can go into next release.
Regarding slowness: pre-computing committee data helps a lot with performance, and makes the committee-per-slot lookup just a fast epoch range check + length read (ZRNT example). Moving this epoch comparison should not be a reason to not consider pre-computing the committees.
cc @djrtwo non-breaking beacon spec change for v0.12.2
djrtwo
approved these changes
Jul 24, 2020
This was referenced Jul 24, 2020
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
data.target.epochis used to count the active validator set.Because
get_committee_count_per_slotis extremely inefficient the waythe spec is written, clients cache it, or the underlying active
validator set.
Performing the checks in the given order leads to a (very unlikely)
security issue where the a cold and above all, distant value may get
used which may be costly - reordering the checks brings the value into a
more reasonable range before using it.