Apply Phase 9D security mitigations

- Add fail-closed wolfSSL small-math policy and vectors
- Backport DHCP, EMS, and X.509 allocation fixes
- Extend source override validation and operational documentation

cmake/wolf_crypto_policy.h

@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-3.0-only */
+#ifndef SAK_WOLF_CRYPTO_POLICY_H
+#define SAK_WOLF_CRYPTO_POLICY_H
+
+#include <wolfssl/wolfcrypt/settings.h>
+
+/* PR9275 selects small math on Xtensa to avoid compiler-introduced timing
+ * differences. Check resolved settings, not just command-line intentions.
+ * https://github.com/wolfSSL/wolfssl/pull/9275
+ */
+#if !defined(HAVE_CURVE25519) || !defined(CURVE25519_SMALL)
+#error "wolf crypto policy: X25519 requires CURVE25519_SMALL"
+#endif
+#if !defined(HAVE_ED25519) || !defined(ED25519_SMALL)
+#error "wolf crypto policy: Ed25519 requires ED25519_SMALL"
+#endif
+/* 5.8.2 excludes small math from automatic blinding and rejects this pairing.
+ * Do not force blinding back on: key layout and function signatures differ.
+ */
+#ifdef WOLFSSL_CURVE25519_BLINDING
+#error "wolf crypto policy: small X25519 is incompatible with blinding"
+#endif
+#if defined(HAVE_CURVE448) || defined(HAVE_ED448)
+#error "wolf crypto policy: review PR9275 small math before enabling 448"
+#endif
+
+#endif