fix: remove panics from merged BBMT verification #5221
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stringhandler
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### ⚠ BREAKING CHANGES * **peer_db:** more accurate peer stats per address (5142) * use consensus hashing API for validator node MMR (5207) * **consensus:** add balanced binary merkle tree (5189) ### Features * add favourite flag to contact ([5217](#5217)) ([0371b60](0371b60)) * add indexer config ([5210](#5210)) ([cf95601](cf95601)) * add merge proof for balanced binary merkle tree ([5193](#5193)) ([8962909](8962909)) * **consensus:** add balanced binary merkle tree ([5189](#5189)) ([8d34e8a](8d34e8a)) * log to base dir ([#5197](#5197)) ([5147b5c](5147b5c)) * **peer_db:** more accurate peer stats per address ([5142](#5142)) ([fdad1c6](fdad1c6)) ### Bug Fixes * add grpc commitment signature proto type ([5200](#5200)) ([d523f1e](d523f1e)) * peer seeds for esme/igor ([5202](#5202)) ([1bc226c](1bc226c)) * remove panics from merged BBMT verification ([5221](#5221)) ([a4c5fce](a4c5fce)) * source coverage ci failure ([5209](#5209)) ([80294a1](80294a1)) * use consensus hashing API for validator node MMR ([5207](#5207)) ([de28115](de28115)) * wallet reuse existing tor address ([5092](#5092)) ([576f44e](576f44e)) * **wallet:** avoids empty addresses in node identity ([5224](#5224)) ([1a66312](1a66312))
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Description
Removes panics from merged balanced binary Merkle tree proofs. Changes proof format to avoid a hash output size assumption. Minor renaming and typo fixes for clarity.
Closes issue 5220.
Motivation and Context
Recent work implements merged balanced binary Merkle tree proofs. However, the verifier depended on a specific hash output length (32 bytes) to differentiate node hashes from proof indexes. This would lead to a panic if this size restriction was not met; it was not enforced because of how hashers are used in the design.
Separately, proof semantics were not checked by the verifier, which could lead to other panics.
This PR addresses both of these points. Instead of relying on hash output size, merged path data now includes a flag to indicate if each step references a proof index or a node hash. The verifier now returns a
Result, producing an error if the proof semantics are incorrect. If they are correct, its return value can be unwrapped as aboolto assert the verification passes. It also fixes a few typos and does some minor renaming for clarity.Note that the design still retains an original assumption of a universal
usizethat may be problematic. Non-merged proofs contain ausizeindex to the node in question, and merged proofs additionally containusizevectors to indicate path lengths and proof indexes. This may lead to unexpected and inconsistent behavior, and should be carefully examined separately.How Has This Been Tested?
Existing unit tests pass.