docs: add details about plat_mboot_measure_key function
Added details of 'plat_mboot_measure_key' function in the porting-guide.
Change-Id: Id62211abc0ba13a0f581dc8e24c7b367afe2dcf5
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/docs/design_documents/measured_boot.rst b/docs/design_documents/measured_boot.rst
index 8130d7d..c4e5213 100644
--- a/docs/design_documents/measured_boot.rst
+++ b/docs/design_documents/measured_boot.rst
@@ -204,6 +204,28 @@
In FVP, Non volatile counters get measured and recorded as Critical data
using the backend via this interface.
+#. **Function : plat_mboot_measure_key()**
+
+ .. code-block:: c
+
+ int plat_mboot_measure_key(const void *pk_oid, const void *pk_ptr,
+ size_t pk_len);
+
+ - This function is used by the platform to measure the passed key and
+ publicise it using any of the supported backends.
+ - The authentication module within the trusted boot framework calls this
+ function for every ROTPK involved in verifying the signature of a root
+ certificate and for every subsidiary key that gets extracted from a key
+ certificate for later authentication of a content certificate.
+ - A cookie, passed as the first argument, serves as a key-OID pointer
+ associated with the public key data, passed as the second argument.
+ - Public key data size is passed as the third argument to this function.
+ - This function must return 0 on success, a signed integer error code
+ otherwise.
+ - In FVP platform, this function is used to calculate the hash of the given
+ key and forward this hash to RSS alongside the measurement of the image
+ which the key signs.
+
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