bis_protect: guard against autorcm on rcm-patched units

exosphere/src/fuse.c

@@ -41,6 +41,11 @@ void fuse_init(void)
     fuse_secondary_private_key_disable();
     fuse_disable_programming();
     
+    /* TODO: Should we allow this to be done later? */
+    if (!g_has_checked_for_rcm_bug_patch) {
+        (void)(fuse_has_rcm_bug_patch());
+    }
+
     /* TODO: Overrides (iROM patches) and various reads happen here */
 }
 

stratosphere/ams_mitm/source/fs_mitm/fsmitm_boot0storage.cpp

@@ -24,7 +24,16 @@ static HosMutex g_boot0_mutex;
 static u8 g_boot0_bct_buffer[Boot0Storage::BctEndOffset];
 
 bool Boot0Storage::CanModifyBctPubks() {
-    return this->title_id != TitleId_Ns;
+    if (IsRcmBugPatched()) {
+        /* RCM bug patched. */
+        /* Only allow NS to update the BCT pubks. */
+        /* AutoRCM on a patched unit will cause a brick, so homebrew should NOT be allowed to write. */
+        return this->title_id == TitleId_Ns;
+    } else {
+        /* RCM bug unpatched. */
+        /* Allow homebrew but not NS to update the BCT pubks. */
+        return this->title_id != TitleId_Ns;
+    }
 }
 
 Result Boot0Storage::Read(void *_buffer, size_t size, u64 offset) {