wolfBoot hardening: PCI BAR restore, DICE zeroization, FIT bounds, and CT-compare fixes

[aidangarske]

F-6561, F-6568, F-6593, F-6562, F-6589

[Copilot]

Pull request overview

Hardening-focused update across wolfBoot’s PCI enumeration, FIT image loading, DICE handling, and constant-time verification logic, with new unit tests to prevent regressions in key failure paths.

Changes:

• Fix PCI 64-bit BAR failure cleanup to restore both BAR dwords (and add coverage for the non-“too much memory” failure path).
• Add bounds enforcement for uncompressed FIT subimages copied into a caller-provided buffer (plus a regression unit test).
• Reduce sensitive-data exposure risk via DICE digest/hash zeroization and a more optimization-resistant constant-time compare accumulator.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tools/unit-tests/unit-pci.c	Adds a unit test ensuring 64-bit BAR upper dword is restored on a non-“too much memory” failure path.
tools/unit-tests/unit-fit-gzip.c	Adds a unit test verifying oversized uncompressed (“none”) FIT subimages are rejected when exceeding out_max.
src/pci.c	Restores 64-bit BAR high dword via unified restore_bar: path to avoid leaving probe masks behind.
src/fdt.c	Enforces out_max bound for uncompressed payload memcpy to prevent overflow; improves failure behavior.
src/dice/dice.c	Zeroizes hash contexts and derived digests after UEID derivation to reduce sensitive-data lifetime.
src/wolfhsm_flash_hal.c	Uses a volatile accumulator in constant-time compare to reduce risk of compiler “helpfulness” altering behavior.
options.mk	Emits a build-time warning when WOLFBOOT_SKIP_BOOT_VERIFY=1 is enabled, clarifying security impact.

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