fix #2790 - MFU OTP writes shouldnt allow for zeroing. Bad sanity check implemented, it should check that every bit doesnt try to zero out. Will do for now

CHANGELOG.md

@@ -3,6 +3,7 @@ All notable changes to this project will be documented in this file.
 This project uses the changelog in accordance with [keepchangelog](http://keepachangelog.com/). Please use this to write notable changes, which is not the same as git commit log...
 
 ## [unreleased][unreleased]
+- Change `hf mfu sim` deny OTP changes with all zeros (@iceman1001)
 - Added missing file in CMakeLists.txt (@iceman1001)
 - Major update to `lf em 4x70` internals on ARM side; Enabling improved debugging and reliability (@henrygab)
 - Improved `pcf7931` generic readability of the code. Unified datatypes and added documentation/explainations (@tinooo)

armsrc/iso14443a.c

@@ -1730,6 +1730,18 @@ void SimulateIso14443aTag(uint8_t tagType, uint16_t flags, uint8_t *useruid, uin
             if (CheckCrc14A(receivedCmd, len)) {
 
                 uint8_t block = receivedCmd[1];
+
+                // OTP sanity check
+                // Quite a bad one,  one should look at all individual bits and see if anyone tries be set as zero
+                // we cheat and do fat 00000000 check instead
+                if (block == 0x03) {
+                    if (memcmp(receivedCmd + 2, "\x00\x00\x00\x00", 4) == 0) {
+                        // OTP can't be set back to zero
+                        // send NACK 0x0 == invalid argument,
+                        EmSend4bit(CARD_NACK_IV);
+                    }
+                }
+
                 if (block > pages) {
                     // send NACK 0x0 == invalid argument
                     EmSend4bit(CARD_NACK_IV);