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libwolfboot: scrub the key cache on the static-buffer builds 

The exit_lock scrub was guarded to the case where ENCRYPT_CACHE is a
stack local, skipping both static ones -- NVM_FLASH_WRITEONCE aliases
it to NVM_CACHE, WOLFBOOT_SMALL_STACK gives it its own array. Those
are exactly the buffers where the plaintext key and nonce would stay
resident for the rest of the boot.
pull/862/head
Daniele Lacamera 2026-08-18 09:19:13 +02:00
parent 597283ad8d
commit c7f277f495
1 changed files with 7 additions and 2 deletions
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9
src/libwolfboot.c
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@ -2016,8 +2016,13 @@ static int RAMFUNCTION hal_set_key(const uint8_t *k, const uint8_t *nonce)
ret = hal_flash_erase(addr_align, WOLFBOOT_SECTOR_SIZE);
#endif
exit_lock:
#if !defined(WOLFBOOT_SMALL_STACK) && !defined(NVM_FLASH_WRITEONCE) && \
!defined(WOLFBOOT_ENCRYPT_CACHE)
/* The raw key and nonce were staged in ENCRYPT_CACHE above. Scrub it
* on every build where wolfBoot owns the buffer: the two static
* cases -- NVM_FLASH_WRITEONCE aliases ENCRYPT_CACHE to NVM_CACHE,
* WOLFBOOT_SMALL_STACK gives it its own static array -- are exactly
* the ones where the plaintext would otherwise stay resident for the
* rest of the boot. Only a caller-supplied buffer is left alone. */
#if !defined(WOLFBOOT_ENCRYPT_CACHE)
ForceZero(ENCRYPT_CACHE, NVM_CACHE_SIZE);
#endif
hal_flash_lock();