[yosuke-wolfssl]

Problem

When MICRIUM is defined and no RNG override is set, settings.h maps CUSTOM_RAND_GENERATE to uC/LIB Math_Rand(). wc_GenerateSeed() then fills the whole DRBG seed from it, without any warning.

Micrium has no entropy API, so Math_Rand() stays as the fallback, which keeps existing builds compiling. The change makes the fallback visible.

Fix (wolfcrypt/src/random.c)

• settings.h no longer sets the Math_Rand default for MICRIUM.
• random.c gains a MICRIUM && !CUSTOM_RAND_GENERATE_BLOCK arm of wc_GenerateSeed(), next to the Deos arm and following the same pattern. It seeds from Math_Rand() and emits a #warning (#pragma message on MSVC/TASKING) naming CUSTOM_RAND_GENERATE_SEED.
• Sample user_settings.h and README.md document how to supply a hardware seed.

Seed source per configuration:

Configuration	Seed source
MICRIUM only	Math_Rand() + build warning
CUSTOM_RAND_GENERATE_SEED / _SEED_OS / CUSTOM_RAND_GENERATE	user function, no warning
WOLFSSL_SILABS_SE_ACCEL, STM32_RNG	hardware TRNG (unchanged)
Platform arms earlier in the chain (USE_WINDOWS_API simulator, PIC32, Freescale RNGA/RNGB)	that platform's source instead of Math_Rand()

Closes f-16887.

Verification

• Compiled random.c against the open-source Micrium headers (uC-OS3/CPU/LIB/Clk, POSIX port) for each override case: the warning fires only in the default case.
• Linked against uC-LIB's lib_math.c: wc_GenerateSeed() output (19 bytes, odd tail) matches the LCG sequence from seed 1.
• Host build and testwolfcrypt pass (MICRIUM not set).
• No CI job builds MICRIUM.

[Copilot]

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[github-actions]

MemBrowse Memory Report · Explore what changed →

zephyr-frdm_rw612

• FLASH: log_const_area -8 B, rodata -8 B, text +160 B (+0.1%, 282,608 B / 67,108,864 B, total: 0% used)

No memory changes detected for:

• gcc-arm-cortex-m0plus
• gcc-arm-cortex-m3
• gcc-arm-cortex-m4
• gcc-arm-cortex-m4-baremetal
• gcc-arm-cortex-m4-crypto-only
• gcc-arm-cortex-m4-dtls13
• gcc-arm-cortex-m4-min-ecc
• gcc-arm-cortex-m4-openssl-compat
• gcc-arm-cortex-m4-pkcs7
• gcc-arm-cortex-m4-pq
• gcc-arm-cortex-m4-rsa-only
• gcc-arm-cortex-m4-sp-math
• gcc-arm-cortex-m4-tls12
• gcc-arm-cortex-m4-tls13
• gcc-arm-cortex-m7
• gcc-arm-cortex-m7-pq
• gcc-arm-cortex-m7-tls13
• stm32-sim-stm32h753

---

_{Catch memory regressions in CI with MemBrowse. Free for open source.}

[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #11922

Scan targets checked: wolfcrypt-src, wolfcrypt-bugs, wolfssl-src, wolfssl-bugs
Not reviewed (no scan target covers them): IDE/ECLIPSE/MICRIUM/README.md, IDE/ECLIPSE/MICRIUM/user_settings.h
Coverage: 2 of 2 in-scope changed file(s) opened by the reviewer

Fenrir result: Approved ✅

No new issues found in the changed files.

Advisory only — this automated result does not count as a GitHub approval.

Review tier: Lite

[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #11922

Fenrir already completed a review of this PR at commit 8189deaa8b2c (run 3546); its findings are the review threads on the PR. Push a new commit to request another review.