tari-project / tari / 36590992162

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Build Type

push

github

Committed by web-flow

Commit Message

fix(jellyfish)!: domain-separate leaf and internal node hashes (#8060)

Description
---
Domain-separates JMT leaf and internal node hashes by using distinct
`"Leaf"` and `"Internal"` hasher labels, where both previously used
`"Node"`.

Replaces the ootle-generated eviction proof fixture with synthetic
tests. Ootle no longer produces the eviction command, and the fixture's
inclusion proof was built with the old hashing. The base layer still
validates eviction proofs, so `tests/eviction_proof.rs` now builds a
command JMT locally (`key == value == command_hash`). It checks that a
valid inclusion proof passes, and that a proof for another command, a
command not in the tree, or the wrong root is rejected. The
unknown-validator QC rejection moved to `commit_proof.rs`.

`jmt_node_hash`, `jmt_node_hash2` and the `JmtHashDomain` version are
unchanged, so leaf key mapping in consumers (e.g. `key_mapper` in ootle)
is not affected.

Motivation and Context
---
Leaf and internal nodes were hashed with the same hasher over the same
64-byte layout (`H(key, value_hash)` vs `H(left, right)`). Because of
this, a real internal node could be presented as a leaf with `key = left
child hash` and `value = right child hash`:
- **Forged inclusion:** this succeeds when the fake key's prefix matches
the node's path, which has probability ~2^-depth, so ~50% at depth 1.
- **Forged non-inclusion:** `verify_exclusion` accepts the same fake
leaf for any key in that subtree, so it can "prove" that existing keys
are absent.

The current base layer caller (`key == value == command_hash`) was not
exploitable. Other consumers of `verify_exclusion`, or of inclusion with
an arbitrary key and value, were.

How Has This Been Tested?
---
Added `it_rejects_an_internal_node_presented_as_a_leaf`, which builds a
two-leaf tree and forges a proof from the root's children. The test
fails on the old hashing, where the forged proof verifies, and passes
with this change. `cargo test -p tari_jellyfish -p... (continued)

Coverage Stats

45 of 45 new or added lines in 2 files covered. (100.0%)

1437 existing lines in 33 files now uncovered.

102373 of 146436 relevant lines covered (69.91%)

398594.29 hits per line