rhboot / rhboot/shim

Verification by vendor cert -- dead code?

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Dominant language
C
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Description

https://github.com/rhboot/shim/blob/7ba7440c49d32f911fb9e1c213307947a777085d/shim.c#L542

How is this code-path reachable?

The vendor cert is addended into MokListRT, thus when loading a vendor signed executable, the certificate check succeeds in check_allowlist in shim.c, measuring the matching certificate under the name MokListRT into PCR7. The success condition in the #if defined(VENDOR_CERT_FILE) section in verify_one_signature never executes for valid executables.

Under PCR7, I am only able to get a measurement named under MokListRT in the eventlog, never Shim.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start in shim.c around line 542 and trace verify_one_signature, check_allowlist, and the VENDOR_CERT_FILE condition for vendor-signed executables. Compare that path with PCR7 event-log measurements named MokListRT and Shim. Done means establishing whether the condition is reachable and explaining the observed measurement behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
c
Domain
operating-systems, security
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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