Reject jumps that land inside instruction operands
A crafted jump targets the second byte of a literal and reinterprets it as an opcode.
- Focused work estimate
- 2h 30m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Control flow · Validation
Estimated field mix
- Systems programming70%
- Security30%
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 rules engine executes a tiny arithmetic bytecode over synthetic integers. Its interpreter trusts jump offsets and can run forever. Build a local Rust runtime; it has no filesystem, network, dynamic loading, host calls, or candidate-source execution.
Setup prerequisites
- Stacks
- Instruction decoding
- Control flow
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Decoder records every legal instruction boundary
- Jump targets must reference a boundary in the same program
- Backward jumps remain permitted within the execution budget
Implementation constraints
- Do not normalize invalid offsets to the nearest instruction.
Verification to include
- Execute forward and backward jumps to valid boundaries.
- Target each byte inside a multi-byte operand and reject validation.
Deliverables
- Boundary-indexed control-flow validation
Rollout and recovery
Invalidate cached programs when the instruction format version changes.
Value of the work
For the engineer: Practice runtime invariants, validation, resource accounting and compatibility.
For the team: Review a constrained execution component whose malformed programs fail deterministically without gaining host capabilities.
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.