fwTPM: append-only NV journal for write-once flash + swtpm UART symlinks

[dgarske]

• Append-only NV mode for write-once flash (internal flash/NOR). The journal stops rewriting the header and trailing MAC in place; instead it derives writePos by scanning, seals each commit with an appended MAC checkpoint, and streams granule-aligned writes so a sector is erased only on compaction. This avoids wearing the header sector and survives a torn final commit (power loss). It plugs into the existing FWTPM_NV_HAL (read/write/erase) - a port sets hal.appendOnly = 1 and hal.writeAlign; no separate adapter. Opt-in and off by default (--enable-fwtpm-nv-appendonly / CMake WOLFTPM_FWTPM_NV_APPEND_ONLY); the file backend and default builds are unchanged and carry no extra memory.
• swtpm UART now accepts symlinked serial paths (drops O_NOFOLLOW; keeps S_ISCHR/O_NOCTTY, adds O_NONBLOCK).

Tests: new unit test (RAM-backed write-once HAL) covers persist/reboot, torn-tail recovery, and tamper rejection. Verified clean with the option both off and on.

Docs: docs/FWTPM.md and src/fwtpm/ports/README.md (links wolftpm-examples; ports: STM32H5, PolarFire SoC U54, ZCU102 R5 lock-step).

[aidangarske]

Skoll Multi-Scan Review

Modes: review + review-security + bugsOverall recommendation: REQUEST_CHANGES
Findings: 4 total — 4 posted, 0 skipped
4 finding(s) posted as inline comments (see file-level comments below)

Posted findings

• [High] [review-security] Append-only NV tamper can roll state back to an earlier checkpoint — src/fwtpm/fwtpm_nv.c:1517-1604
• [High] [bugs] Append-only recovery misses a torn header at the next append offset — src/fwtpm/fwtpm_nv.c:1514-1604
• [Medium] [review] Document zero-initialization requirement for extended NV HAL — wolftpm/fwtpm/fwtpm_nv.h:182-184
• [Medium] [review] Add coverage for no-key append-only images without a checkpoint — src/fwtpm/fwtpm_nv.c:1545-1557

Review generated by Skoll