Let signing backend validate personalization (#873)

For soft signing, let backend handle checksum verification of
personalization data. This ensures that the backends sha256 library is
used and avoids an unnecessary instanitation of the public library.
For atsha204 signing, no checksum verification is made, just chip
locking flags.

Fixes #872

core/MySigning.cpp

@@ -90,7 +90,6 @@ extern bool signerAtsha204SignMsg(MyMessage &msg);
 #define signerBackendVerifyMsg  signerAtsha204VerifyMsg
 #define signerBackendSignMsg    signerAtsha204SignMsg
 #endif
-static bool signerValidatePersonalization(void);
 static bool skipSign(MyMessage &msg);
 #else // not MY_SIGNING_FEATURE
 #define signerBackendCheckTimer() true
@@ -103,8 +102,6 @@ static bool signerInternalProcessNonceResponse(MyMessage &msg);
 void signerInit(void)
 {
 #if defined(MY_SIGNING_FEATURE)
-	(void)signerValidatePersonalization();
-
 	// Read out the signing requirements from EEPROM
 	hwReadConfigBlock((void*)_doSign, (void*)EEPROM_SIGNING_REQUIREMENT_TABLE_ADDRESS,
 	                  sizeof(_doSign));
@@ -341,33 +338,6 @@ int signerMemcmp(const void* a, const void* b, size_t sz)
 
 #if defined(MY_SIGNING_FEATURE)
 // Helper function to centralize signing/verification exceptions
-static bool signerValidatePersonalization(void)
-{
-#ifdef MY_SIGNING_SIMPLE_PASSWD
-	return true;
-#else
-	uint8_t buffer[32];
-	uint8_t* hash;
-	uint8_t checksum;
-	signerSha256Init();
-	hwReadConfigBlock((void*)buffer, (void*)EEPROM_SIGNING_SOFT_HMAC_KEY_ADDRESS, 32);
-	signerSha256Update(buffer, 32);
-	hwReadConfigBlock((void*)buffer, (void*)EEPROM_RF_ENCRYPTION_AES_KEY_ADDRESS, 16);
-	signerSha256Update(buffer, 16);
-	hwReadConfigBlock((void*)buffer, (void*)EEPROM_SIGNING_SOFT_SERIAL_ADDRESS, 9);
-	signerSha256Update(buffer, 9);
-	hash = signerSha256Final();
-	hwReadConfigBlock((void*)&checksum, (void*)EEPROM_PERSONALIZATION_CHECKSUM_ADDRESS, 1);
-	if (checksum != hash[0]) {
-		SIGN_DEBUG(PSTR("!SGN:PER:TAMPERED\n"));
-		return false;
-	} else {
-		SIGN_DEBUG(PSTR("SGN:PER:OK\n"));
-		return true;
-	}
-#endif
-}
-
 static bool skipSign(MyMessage &msg)
 {
 	bool ret = false;

core/MySigningAtsha204Soft.cpp

@@ -103,8 +103,37 @@ bool signerAtsha204SoftInit(void)
 		_signing_node_serial_info[8] = getNodeId();
 	}
 #else
+	uint8_t buffer[32];
+	uint8_t* hash;
+	uint8_t checksum;
+
+	_signing_sha256.init();
+	hwReadConfigBlock((void*)buffer, (void*)EEPROM_SIGNING_SOFT_HMAC_KEY_ADDRESS, 32);
+	for (int i = 0; i < 32; i++) {
+		_signing_sha256.write(buffer[i]);
+	}
+	hwReadConfigBlock((void*)buffer, (void*)EEPROM_RF_ENCRYPTION_AES_KEY_ADDRESS, 16);
+	for (int i = 0; i < 16; i++) {
+		_signing_sha256.write(buffer[i]);
+	}
+	hwReadConfigBlock((void*)buffer, (void*)EEPROM_SIGNING_SOFT_SERIAL_ADDRESS, 9);
+	for (int i = 0; i < 9; i++) {
+		_signing_sha256.write(buffer[i]);
+	}
+	hash = _signing_sha256.result();
+	hwReadConfigBlock((void*)&checksum, (void*)EEPROM_PERSONALIZATION_CHECKSUM_ADDRESS, 1);
+	if (checksum != hash[0]) {
+		SIGN_DEBUG(PSTR("!SGN:PER:TAMPERED\n"));
+		init_ok = false;
+	} else {
+		SIGN_DEBUG(PSTR("SGN:PER:OK\n"));
+		init_ok = true;
+	}
+
+	if (init_ok) {
 		hwReadConfigBlock((void*)_signing_hmac_key, (void*)EEPROM_SIGNING_SOFT_HMAC_KEY_ADDRESS, 32);
 		hwReadConfigBlock((void*)_signing_node_serial_info, (void*)EEPROM_SIGNING_SOFT_SERIAL_ADDRESS, 9);
+	}
 #endif
 	if (!memcmp(_signing_node_serial_info, reset_serial, 9)) {
 		unique_id_t uniqueID;