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/security_overrides.cmake

@@ -31,11 +31,29 @@ set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS
 
 # Public extension point: the Python Entry registry supplies the mapping. This
 # function is backend-agnostic; a later pinned project/vendor source uses it too.
-function(sak_security_replace_source component original generated)
+function(sak_security_replace_source component original generated nested_target)
     idf_component_get_property(_target "${component}" COMPONENT_LIB)
     if(NOT TARGET "${_target}")
         message(FATAL_ERROR "Security override: missing component target ${component}")
     endif()
+    if(NOT "${nested_target}" STREQUAL "")
+        if(NOT component STREQUAL "mbedtls" OR
+           NOT nested_target MATCHES "^(mbedtls|mbedx509|mbedcrypto)$")
+            message(FATAL_ERROR "Security override: invalid nested target ${component}/${nested_target}")
+        endif()
+        if(NOT TARGET "${nested_target}")
+            message(FATAL_ERROR "Security override: missing nested target ${nested_target}")
+        endif()
+        set(_target "${nested_target}")
+        get_target_property(_imported "${_target}" IMPORTED)
+        get_target_property(_alias "${_target}" ALIASED_TARGET)
+        get_target_property(_owner_dir "${_target}" SOURCE_DIR)
+        get_filename_component(_owner_dir "${_owner_dir}" REALPATH)
+        get_filename_component(_expected_owner "${_sak_security_idf}/components/mbedtls/mbedtls/library" REALPATH)
+        if(_imported OR _alias OR NOT _owner_dir STREQUAL _expected_owner)
+            message(FATAL_ERROR "Security override: unexpected nested target owner ${_target}: ${_owner_dir}")
+        endif()
+    endif()
     get_target_property(_source_dir "${_target}" SOURCE_DIR)
     get_target_property(_sources "${_target}" SOURCES)
     get_filename_component(_expected "${original}" REALPATH)
@@ -98,5 +116,6 @@ foreach(_sak_security_id IN LISTS SAK_SECURITY_OVERRIDE_IDS)
     sak_security_replace_source(
         "${SAK_SECURITY_${_sak_security_id}_COMPONENT}"
         "${SAK_SECURITY_${_sak_security_id}_ORIGINAL}"
-        "${SAK_SECURITY_${_sak_security_id}_GENERATED}")
+        "${SAK_SECURITY_${_sak_security_id}_GENERATED}"
+        "${SAK_SECURITY_${_sak_security_id}_TARGET}")
 endforeach()

cmake/wolf_crypto_policy.cmake

@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-3.0-only
+# Apply after project(). PUBLIC propagates the resolved-settings guard to every
+# wolfSSL consumer, including wolfSSH and the application (ABI-sensitive keys).
+idf_component_get_property(_sak_wolf_target wolfssl__wolfssl COMPONENT_LIB)
+if(NOT TARGET "${_sak_wolf_target}")
+    message(FATAL_ERROR "wolf crypto policy: missing wolfSSL component target")
+endif()
+target_compile_options("${_sak_wolf_target}" PUBLIC
+    "-include${CMAKE_CURRENT_LIST_DIR}/wolf_crypto_policy.h")

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