Adds a layered entropy mixer for first-boot identity Ed25519 keygen,
primarily to address ESP32 where the hardware TRNG (WDEV_RND_REG) is
only fed real entropy once the internal WiFi/BT radio is enabled —
but identity gen runs before that on companion and indefinitely
before that on a bare repeater. ESP-IDF's bootloader_random_enable()
is not compiled by Zephyr-Espressif HAL, ruling out that workaround.
Design reviewed with nextgens (author of upstream meshcore-dev/
MeshCore#2280 which fixes the same issue via BT/WiFi init/pull/deinit).
ZephyrRNG::random — retry sys_csrand_get up to 4x with k_msleep
backoff; cold-reboot on persistent failure. Previously fell back
silently to sys_rand_get (xoshiro PRNG), which would have produced
a weak Ed25519 seed on CSPRNG error. BUILD_ASSERT enforces
CONFIG_CSPRNG_ENABLED.
ZephyrRNG::mixIdentitySeed — layered entropy mixer for one-shot
identity keygen. Combines sys_csrand_get (early + late),
HWINFO unique device ID, caller-supplied ADC LSB noise, 200ms of
CPU cycle-counter jitter (NIST SP 800-90B class source), and
50ms more jitter in an independent timing window. Conditioned via
AES-256-CTR (NIST SP 800-108 KDF-in-Counter-Mode): SHA-256 of the
pool extracts a 32-byte AES key; AES-256-ECB on an incrementing
128-bit counter expands to the requested output length. Uses PSA
crypto already enabled in zephcore_common.conf. NIST-style
repetition-count + variance health check on jitter samples;
reboot on degenerate output. ~280ms one-time cost at first boot.
LoRa radio TRNG was considered as an additional source but rejected
on expert advice — radio sources are attacker-influenceable
(jamming/spoofing).
ui-joystick BLE passkey — switch from sys_rand32_get (non-crypto
xoshiro) to sys_csrand_get. The 6-digit passkey is the MITM
protection the rest of the BLE config enforces; predictable PINs
weaken it.
Identity reserved-prefix loop — replace the silent 10-attempt cap
(which committed whatever it had on fall-through) with a
bounded-retry-then-reboot pattern.
Also: fix a pre-existing scope bug at main_companion.cpp:357 in
the MESH_EVENT_PREFS_DIRTY handler — data_store was referenced
inside mesh_event_loop() but declared 50+ lines later. Moved the
call into a forward-declared helper defined after the statics.
Unrelated to crypto work but uncovered during build verification;
every companion build was broken.
Stop doing UI work nobody asked for. The 5 s housekeeping tick was
reading env sensors (I2C, 10-50 ms), the battery ADC (regulator
toggle + 8 samples, every 60 s), and re-rendering the display
unconditionally — all while the display might be off and nothing
on-air had requested any of it.
Now:
- render_sensors() reads env sensors only when the user is on
that page (event-driven, never fires during idle)
- battery refresh is lazy on ui_pages_render() with a 30 s
freshness guard; explicit ui_set_battery() calls also count
- the unconditional OLED rerender from housekeeping is gone;
real state changes (messages, BLE, button press) still fire
schedule_render() directly
Telemetry / stats paths read fresh ADC + sensors on demand and
were never using the UI cache, so over-the-air consumers are
unaffected.
- calibrate_image: revert to datasheet band table. Narrow ±2 MHz
window had truncation bug placing 433/869 MHz operating freq
outside their own calibration windows. DS §9.2.1 confirms cal
is range-validity, not point-precision
- reset_agc: K_FOREVER mutex → K_MSEC(50). Was holding dispatcher
thread up to ~3 s if a long TX/RX held the SPI lock. Now bails
with WARN log; caller retries next maintenance interval.
liquidraver