hardening: mark append_fixed_slice_as_bytes as unsafe and document safety requirements#20
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MegaRedHand wants to merge 2 commits into
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hardening: mark append_fixed_slice_as_bytes as unsafe and document safety requirements#20MegaRedHand wants to merge 2 commits into
append_fixed_slice_as_bytes as unsafe and document safety requirements#20MegaRedHand wants to merge 2 commits into
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decode_byte_array_vec: drop "no padding" (not a soundness requirement for the decode direction; [u8; N] is valid for any bit pattern). append_fixed_slice_as_bytes: keep "no padding" (the encode direction reads T as bytes, and the Reference allows padding in valid T values to hold uninitialized bytes, making the u8 reinterpretation UB).
MegaRedHand
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unsafe blocksappend_fixed_slice_as_bytes as unsafe and document safety requirements
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Summary
This PR marks
append_fixed_slice_as_bytesasunsafeand documents the safety requirements for both remainingunsafeblocks in the SSZ encode/decode paths.append_fixed_slice_as_bytesreinterprets&[T]as&[u8]viafrom_raw_parts. This is only sound ifThas no padding bytes, because the Reference allows padding within a validTto hold uninitialized bytes, and a&[u8]covering uninitialized bytes violates the requirement that a reference must point to valid values.decode_byte_array_vecusescopy_nonoverlapping+set_lento bulk-decodeVec<[u8; N]>. Since[u8; N]is trivially valid for any bit pattern, no safety contract is needed on the function itself; the// SAFETY:comment documents the bounds check.Changes
encode.rsappend_fixed_slice_as_bytesunsafe fn, added# Safetydoc ("T must not have padding"), added// SAFETY:at each call sitedecode.rsdecode_byte_array_vec// SAFETY:comment documenting the bounds invariant