change(secure_boot): mark ECDSA based Secure Boot V2 as insecure on affected SoCs

ECDSA based Secure Boot V2 is not functional for certain input vectors on
ESP32-C5/C61/H2/P4 and on the preview targets ESP32-H4/H21. RSA based Secure
Boot V2 is the recommended scheme where the SoC supports it. This issue will be
fixed in a future hardware ECO revision; more details will be shared through the
hardware errata document.

A new hidden Kconfig option SECURE_BOOT_V2_ECDSA_INSECURE marks the affected
mass-production SoCs (ESP32-C5/C61/H2/P4). On these SoCs, when hardware Secure
Boot V2 is enabled, the ECDSA (V2) signing scheme is no longer offered by
default; it must be turned on explicitly via SECURE_BOOT_V2_FORCE_ENABLE_ECDSA
under "Allow potentially insecure options" (CONFIG_SECURE_BOOT_INSECURE). App
signing without hardware Secure Boot is not affected. Note that ESP32-C61 has no
RSA based Secure Boot V2, so it has no Secure Boot scheme enabled by default.

The preview targets ESP32-H4 and ESP32-H21 mark ECDSA Secure Boot V2 as not
supported in their SoC capabilities instead of using the option above. As
ESP32-H4 has no other Secure Boot V2 scheme, Secure Boot is disabled entirely on
it; ESP32-H21 retains RSA based Secure Boot V2.

The security documentation keeps the ECDSA Secure Boot V2 content visible and
adds a warning describing the limitation (including that ECDSA Secure Boot V2 on
ESP32-C61 is not recommended for production). CI apps that exercise ECDSA Secure
Boot V2 on the affected SoCs set CONFIG_SECURE_BOOT_V2_FORCE_ENABLE_ECDSA
accordingly.

docs/en/security/secure-boot-v2.rst

@@ -46,6 +46,18 @@ Secure Boot v2
 
     In this guide, most used commands are in the form of ``idf.py secure-<command>``, which is a wrapper around corresponding ``espsecure.py <command>``. The ``idf.py`` based commands provides more user-friendly experience, although may lack some of the advanced functionality of their ``espsecure.py`` based counterparts.
 
+.. only:: CONFIG_SECURE_BOOT_V2_ECDSA_INSECURE and SOC_SECURE_BOOT_V2_RSA
+
+    .. warning::
+
+        On {IDF_TARGET_NAME}, the ECDSA based Secure Boot V2 scheme is not functional for certain input vectors and is therefore **not recommended**. Please use the RSA based Secure Boot V2 scheme instead. To use the ECDSA based scheme regardless of this limitation, enable :ref:`CONFIG_SECURE_BOOT_INSECURE` and :ref:`CONFIG_SECURE_BOOT_V2_FORCE_ENABLE_ECDSA`. This issue will be fixed in a future hardware ECO revision; refer to the hardware errata document for details.
+
+.. only:: CONFIG_SECURE_BOOT_V2_ECDSA_INSECURE and not SOC_SECURE_BOOT_V2_RSA
+
+    .. warning::
+
+        On {IDF_TARGET_NAME}, the ECDSA based Secure Boot V2 scheme is vulnerable for certain input vectors and is therefore **not recommended for production**. To use the ECDSA based Secure Boot V2 scheme regardless of this limitation, enable :ref:`CONFIG_SECURE_BOOT_INSECURE` and :ref:`CONFIG_SECURE_BOOT_V2_FORCE_ENABLE_ECDSA`. This issue will be fixed in a future hardware ECO revision; refer to the hardware errata document for details.
+
 Background
 ----------
 

docs/zh_CN/security/secure-boot-v2.rst

@@ -46,6 +46,18 @@
 
     在本指南中，最常用的命令形式为 ``idf.py secure-<command>``，这是对应 ``espsecure.py <command>`` 的封装。基于 ``idf.py`` 的命令能提供更好的用户体验，但与基于 ``espsecure.py`` 的命令相比，可能会损失一部分高级功能。
 
+.. only:: CONFIG_SECURE_BOOT_V2_ECDSA_INSECURE and SOC_SECURE_BOOT_V2_RSA
+
+    .. warning::
+
+        在 {IDF_TARGET_NAME} 上，基于 ECDSA 的 Secure Boot V2 方案在某些输入向量下无法正常工作，因此**不推荐使用**。请改用基于 RSA 的 Secure Boot V2 方案。如果仍需使用基于 ECDSA 的方案，请启用 :ref:`CONFIG_SECURE_BOOT_INSECURE` 和 :ref:`CONFIG_SECURE_BOOT_V2_FORCE_ENABLE_ECDSA`。该问题将在未来的硬件 ECO 版本中修复，详情请参阅硬件勘误文档。
+
+.. only:: CONFIG_SECURE_BOOT_V2_ECDSA_INSECURE and not SOC_SECURE_BOOT_V2_RSA
+
+    .. warning::
+
+        在 {IDF_TARGET_NAME} 上，基于 ECDSA 的 Secure Boot V2 方案在某些输入向量下存在漏洞，因此**不推荐用于量产**。如果仍需使用基于 ECDSA 的 Secure Boot V2 方案，请启用 :ref:`CONFIG_SECURE_BOOT_INSECURE` 和 :ref:`CONFIG_SECURE_BOOT_V2_FORCE_ENABLE_ECDSA`。该问题将在未来的硬件 ECO 版本中修复，详情请参阅硬件勘误文档。
+
 背景
 ----------