Contain unsafe decoding behind a length-checked cursor
Several parsers perform pointer arithmetic independently; one reads a declared payload length before confirming those bytes remain.
- Focused work estimate
- 6h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Unsafe code review · Binary parsing · Fuzzing
Estimated field mix
- Systems programming65%
- Security35%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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Project context
A fictional telemetry collector copies decoded packet fields into a small native arena. The prototype misaligns wide values and reuses memory while readers still hold views. Create a local Rust crate or C library with generated byte fixtures; no device traffic or production allocator replacement is supplied.
Setup prerequisites
- Pointers and slices
- Integer overflow
- Memory alignment
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- One cursor owns offset advancement and remaining-length checks
- Primitive reads define endianness and alignment behavior
- A failed read returns no partially initialized value
Implementation constraints
- Fuzz only the local parser process and cap input length, nesting, and execution time.
Verification to include
- Decode a complete packet containing every primitive type.
- Truncate at every byte boundary and run the corpus under sanitizer or Miri.
Deliverables
- Checked decode cursor, fuzz corpus, and unsafe-boundary note
Rollout and recovery
Route one packet family at a time through the cursor and retain the prior decoder for comparison.
Value of the work
For the engineer: Practice representation invariants, lifetimes, unsafe-boundary review and memory diagnostics.
For the team: Review a component whose allocation failures and corruption cases are explicit before reuse in latency-sensitive code.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.