Bound fwTPM PCR capability response parsing

[aidangarske]

• Coverity CID 913848 flagged response controlled loop bounds in the fwTPM test helper.
• Validate the response length before reading the fixed fields.
• Bound the bank count and PCR selection size before iterating.
• Return an error for truncated or malformed capability data.
• Add regression cases for valid and malformed responses.

[Copilot]

Warning

Copilot couldn't run its full agentic review because it didn't start before the timeout. Make sure your repository has a runner available, or add a copilot-code-review.yml file specifying one with the runs-on attribute. See the docs for more details.

Copilot review overview

Review effort: Lite
Findings: 2

Open (2)

• fwtpm_parse_bank_allocated() is presented as a response parser, but it reads from the global… · New
• The parser claims to handle “a TPM_CAP_PCRS response”, but it never validates that the capability… · New

What changed in this PR

This PR hardens fwTPM PCR capability response parsing by adding explicit bounds checks before iterating over response-controlled fields, and introduces regression tests for valid and malformed responses.

Changes:

• Split PCR bank detection into a response parser (fwtpm_parse_bank_allocated) plus a command wrapper (fwtpm_bank_allocated).
• Add defensive validation for response size, bank count, and PCR selection size before parsing.
• Add a new unit test to cover valid and malformed PCR capability responses.

File	Description
tests/​fwtpm_unit_tests.c	Adds a bounded parser for TPM_CAP_PCRS responses and regression tests for malformed/truncated data.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.