[Merged by Bors] - Use a fixed state hasher in bevy_reflect for deterministic Reflect::reflect_hash() across processes #7583
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alice-i-cecile
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It's hard to imagine a case where we wouldn't want this. Why should this be a feature, rather than always enabled? |
Yeah, I guess the possibility of DOS attacks through bevy_reflect are pretty far fetched. I guess if anything it should probably an opt-in feature to make it runtime-seeded. Hard-coding to always use fixed state |
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MrGVSV
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crates/bevy_reflect/src/reflect.rs
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| use bevy_utils::FixedState; | ||
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| #[inline] | ||
| pub fn reflect_hasher() -> bevy_utils::AHasher { |
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Nit: This should probably have a doc stating what it does, how/where it's used, and when/why to use it.
Conflicts: - crates/bevy_reflect/src/list.rs
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Sorry for the noise, still figuring out how the "reviewers" system on github works |
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james7132
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…eflect_hash() across processes (#7583) # Objective - bevy_ggrs uses `reflect_hash` in order to produce checksums for its world snapshots. These checksums are sent between clients in order to detect desyncronization. - However, since we currently use `async::AHasher` with the `std` feature, this means that hashes will always be different for different peers, even if the state is identical. - This means bevy_ggrs needs a way to get a deterministic (fixed) hash. ## Solution - ~~Add a feature to use `bevy_utils::FixedState` for the hasher used by bevy_reflect.~~ - Always use `bevy_utils::FixedState` for initializing the bevy_reflect hasher. --- ## Changelog - bevy_reflect now uses a fixed state for its hasher, which means the output of `Reflect::reflect_hash` is now deterministic across processes.
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…eflect_hash() across processes (#7583) # Objective - bevy_ggrs uses `reflect_hash` in order to produce checksums for its world snapshots. These checksums are sent between clients in order to detect desyncronization. - However, since we currently use `async::AHasher` with the `std` feature, this means that hashes will always be different for different peers, even if the state is identical. - This means bevy_ggrs needs a way to get a deterministic (fixed) hash. ## Solution - ~~Add a feature to use `bevy_utils::FixedState` for the hasher used by bevy_reflect.~~ - Always use `bevy_utils::FixedState` for initializing the bevy_reflect hasher. --- ## Changelog - bevy_reflect now uses a fixed state for its hasher, which means the output of `Reflect::reflect_hash` is now deterministic across processes.
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…eflect_hash() across processes (bevyengine#7583) - bevy_ggrs uses `reflect_hash` in order to produce checksums for its world snapshots. These checksums are sent between clients in order to detect desyncronization. - However, since we currently use `async::AHasher` with the `std` feature, this means that hashes will always be different for different peers, even if the state is identical. - This means bevy_ggrs needs a way to get a deterministic (fixed) hash. - ~~Add a feature to use `bevy_utils::FixedState` for the hasher used by bevy_reflect.~~ - Always use `bevy_utils::FixedState` for initializing the bevy_reflect hasher. --- - bevy_reflect now uses a fixed state for its hasher, which means the output of `Reflect::reflect_hash` is now deterministic across processes.
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Objective
reflect_hashin order to produce checksums for its world snapshots. These checksums are sent between clients in order to detect desyncronization.async::AHasherwith thestdfeature, this means that hashes will always be different for different peers, even if the state is identical.Solution
Add a feature to usebevy_utils::FixedStatefor the hasher used by bevy_reflect.bevy_utils::FixedStatefor initializing the bevy_reflect hasher.Changelog
Reflect::reflect_hashis now deterministic across processes.