STM32C5A3ZG: bare-metal wolfIP port + TLS 1.3 mutual auth with a HUK-protected identity key

[dgarske]

Summary

New wolfIP port for the NUCLEO-C5A3ZG (Cortex-M33F, no TrustZone), reusing the shared STM32 DWC GMAC driver (one STM32C5 alias in src/port/stm32/stm32_eth.c). All milestones validated on hardware.

What works (HW-validated)

• Network: DHCP + ICMP ping + TCP echo.
• DHUK crypto callback self-test: ECDSA-sign (HW PKA), AES-GCM (SAES), HMAC-SHA256 (HASH), TRNG.
• TLS 1.3 mutual-auth client: handshake to openssl s_server -Verify 1, TLS_AES_128_GCM_SHA256; peer verifies the device client cert.
• HUK identity key in TLS: CertificateVerify signed via the DHUK callback (SAES unwrap -> HW PKA); the identity scalar never exists in software. Peer's verify return:1 is the proof.

Build

• make (network only) / make ENABLE_CB_SELFTEST=1 / make ENABLE_TLS_CLIENT=1 / make ENABLE_TLS_CLIENT=1 ENABLE_DHUK_KEY=1.
• TLS builds need the wolfSSL STM32 bare-crypto branch (WOLFSSL_ROOT, default ../wolfssl-c5tls).
• Flash: STM32CubeProgrammer (SWD, mode=UR). Flash 3.0% -> 21.9% across the variants.

Notable fixes in this port

• _sbrk now uses the linker .heap region (was overlapping the Ethernet DMA buffers -> packet DMA corrupted malloc'd TLS objects).
• C5 RNG clock-error detector disabled (WC_STM32_RNG_CED_DISABLE / CR.CED; false-trips on the 48 MHz CK48).
• RMII RXD0/RXD1 use AF12/AF13 (not AF10); MSPLIM wired to the real stack-limit symbol; 64K heap/stack + WOLFSSL_SMALL_STACK.

Scope

Config A: identity key on the callback, ephemeral ECDHE in software. Config B (route ECDHE through the callback to strip software ECC) is a follow-on. Demo identity key is a public NIST CAVP vector; production provisions the wrapped blob off-device.

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