add rk delete implementations

fido2/device.c

@@ -185,6 +185,21 @@ __attribute__((weak)) void ctap_store_rk(int index, CTAP_residentKey * rk)
 
 }
 
+__attribute__((weak)) void ctap_delete_rk(int index)
+{
+    CTAP_residentKey rk;
+
+    if (index < RK_NUM)
+    {
+        memmove(RK_STORE.rks + index, &rk, sizeof(CTAP_residentKey));
+    }
+    else
+    {
+        printf1(TAG_ERR,"Out of bounds for delete_rk\r\n");
+    }
+
+}
+
 __attribute__((weak)) void ctap_load_rk(int index, CTAP_residentKey * rk)
 {
     memmove(rk, RK_STORE.rks + index, sizeof(CTAP_residentKey));

fido2/device.h

@@ -140,6 +140,13 @@ uint32_t ctap_rk_size();
 */
 void ctap_store_rk(int index,CTAP_residentKey * rk);
 
+/** Delete a resident key from an index.
+ * @param index to delete resident key from.  Has no effect if no RK exists at index.
+ * 
+ * *Optional*, if not implemented, operates on non-persistant RK's.
+*/
+void ctap_delete_rk(int index);
+
 /** Read a resident key from an index into memory
  * @param index to read resident key from.
  * @param rk pointer to resident key structure to write into with RK.

pc/device.c

@@ -449,6 +449,12 @@ void ctap_store_rk(int index, CTAP_residentKey * rk)
 
 }
 
+void ctap_delete_rk(int index)
+{
+    CTAP_residentKey rk;
+    memset(&rk, 0xff, sizeof(CTAP_residentKey));
+    memmove(RK_STORE.rks + index, &rk, sizeof(CTAP_residentKey));
+}
 
 void ctap_load_rk(int index, CTAP_residentKey * rk)
 {

targets/stm32l432/src/device.c

@@ -793,6 +793,13 @@ void ctap_store_rk(int index,CTAP_residentKey * rk)
     ctap_overwrite_rk(index, rk);
 }
 
+void ctap_delete_rk(int index)
+{
+    CTAP_residentKey rk;
+    memset(&rk, 0xff, sizeof(CTAP_residentKey));
+    ctap_overwrite_rk(index, &rk);
+}
+
 void ctap_load_rk(int index,CTAP_residentKey * rk)
 {
     int byte_offset_into_page = (sizeof(CTAP_residentKey) * (index % (PAGE_SIZE/sizeof(CTAP_residentKey))));