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Formal verification related fixes #29

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16 of 21 tasks
OlivierBBB opened this issue Oct 27, 2023 · 0 comments
Open
16 of 21 tasks

Formal verification related fixes #29

OlivierBBB opened this issue Oct 27, 2023 · 0 comments
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@OlivierBBB
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OlivierBBB commented Oct 27, 2023

Main point

There is an issue with the padding in the ADD module spotted by @ericsson49 : a malicious prover can use the padding to insert a single wrong instruction into the ADD module. This is a serious security issue, thankfully with a trivial fix.

Other modules of that era may also be affected.

List of fixes

  • ADD module: constrain INST to be zero in the padding (+ optional vanishing of arguments in padding)
  • check if affected and fix if necessary
    • MUL
    • MOD
      • currently requires instruction decoding, but could be done with out with 4 binary columns
      • missing constraint killing INST in the padding (spotted by @ericsson49)
    • EXT
    • SHF
      • instruction isn't constrained in padding
      • instruction isn't constrained outside of padding either, though the point is recognized
        image
      • again 3 binary columns would suffice
    • BIN
      • spec update
      • lisp update
      • java update
    • WCP
      • spec update
      • lisp update
      • java update
        instruction + simplifying OLI etc ...
@OlivierBBB OlivierBBB self-assigned this Oct 27, 2023
@OlivierBBB OlivierBBB changed the title Fix ALU Formal verification related fixes Oct 27, 2023
@OlivierBBB OlivierBBB added the bug Something isn't working label Nov 18, 2023
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