Move progressive list checks into BeaconBlock::from_ssz_bytes - #10098
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michaelsproul wants to merge 2 commits into
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michaelsproul wants to merge 2 commits into
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I don't really like this approach. I think it's too fragile. It doesn't make it easy to check that we don't accidentally bypass the length limit. There could be cases like serde decoding or manual construction, or weird piece-wise SSZ decoding that end up skipping the length checks. I think the cleanest approach is probably going to be type-level length limits again, like: I pushed the code for execution payloads in db2d410, and even though it's slop, I think it conveys the inherent complexity and fragility of this approach. |
michaelsproul
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Sep 21, 2026
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| impl<E: EthSpec> Decode for ExecutionPayloadEnvelope<E> { | ||
| fn is_ssz_fixed_len() -> bool { | ||
| false | ||
| } | ||
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| fn from_ssz_bytes(bytes: &[u8]) -> Result<Self, ssz::DecodeError> { | ||
| let mut builder = ssz::SszDecoderBuilder::new(bytes); | ||
| builder.register_type::<ExecutionPayloadGloas<E>>()?; | ||
| builder.register_type::<ExecutionRequestsGloas<E>>()?; | ||
| builder.register_type::<u64>()?; | ||
| builder.register_type::<Hash256>()?; | ||
| builder.register_type::<Hash256>()?; | ||
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| let mut decoder = builder.build()?; | ||
| let envelope = Self { | ||
| payload: decoder.decode_next()?, | ||
| execution_requests: decoder.decode_next()?, | ||
| builder_index: decoder.decode_next()?, | ||
| beacon_block_root: decoder.decode_next()?, | ||
| parent_beacon_block_root: decoder.decode_next()?, | ||
| }; | ||
| verify_execution_payload_list_lengths_post_gloas(ExecutionPayloadRef::Gloas( | ||
| &envelope.payload, | ||
| ))?; | ||
| verify_execution_request_list_lengths_post_gloas(&envelope.execution_requests)?; | ||
| Ok(envelope) | ||
| } |
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This is fairly yuck IMO.
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Closing in favour of: |
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Issue Addressed
We are vulnerable to all sorts of DoS nonsense and memory amplification due to
ProgressiveList. This PR tries to take an aggressive approach to stop oversizedProgressiveLists making it out ofDecode.Proposed Changes
BeaconBlockinsideBeaconBlock::from_ssz_bytes.ExecutionPayloadEnvelopeduring decoding (warning: slop).Additional Info
Arguably one could still decode a
BeaconBlockBody{Gloas}while bypassing the length check. Putting it one level up inBeaconBlockis convenient because we already have that method, and I have checked that production decoding always goes via this codepath (we almost always decode aSignedBeaconBlock, andany_from_ssz_bytesis only used by MockBeaconNode [we should probably delete it]).Replaces: