Add Checksums to Firmware & External App images (#1809)

* Pad image to 1MB and add simple checksum

* Test code to verify firmware checksum

* Comment out unneeded zlib

* Add files via upload

* Print space remaining in ROM

* Append checksum to external apps too

* Check external app checksums when loading

* Is it 2024 already?!

* Validate firmware checksum before flashing

* Add files via upload

* Added flash error warning to nav screen

* Clang

* Replaced some hard-coded values with #defines

* Check FW checksum before USB serial flash too

* Add files via upload

firmware/tools/export_external_apps.py

@@ -104,6 +104,14 @@ for external_image_prefix in sys.argv[4:]:
 		external_application_image = patch_image(external_application_image, search_address, replace_address)
 		external_application_image[memory_location_header_position:memory_location_header_position+4] = replace_address.to_bytes(4, byteorder='little')
 
+		checksum = 0
+		for i in range(0, len(external_application_image), 4):
+			checksum += external_application_image[i] + (external_application_image[i + 1] << 8) + (external_application_image[i + 2] << 16) + (external_application_image[i + 3] << 24)
+
+		final_checksum = 0
+		checksum = (final_checksum - checksum) & 0xFFFFFFFF
+		external_application_image += checksum.to_bytes(4, 'little')
+
 		write_image(external_application_image, "{}/{}.ppma".format(binary_dir, external_image_prefix))
 		continue
 
@@ -127,5 +135,13 @@ for external_image_prefix in sys.argv[4:]:
 		print("application {} can not exceed 32kb: {} bytes used".format(external_image_prefix, len(external_application_image)))
 		sys.exit(-1)
 
+	checksum = 0
+	for i in range(0, len(external_application_image), 4):
+		checksum += external_application_image[i] + (external_application_image[i + 1] << 8) + (external_application_image[i + 2] << 16) + (external_application_image[i + 3] << 24)
+
+	final_checksum = 0
+	checksum = (final_checksum - checksum) & 0xFFFFFFFF
+	external_application_image += checksum.to_bytes(4, 'little')
+
 	# write .ppma (portapack mayhem application)
 	write_image(external_application_image, "{}/{}.ppma".format(binary_dir, external_image_prefix))

firmware/tools/make_spi_image.py

@@ -74,7 +74,24 @@ for image in images:
 	padded_data = image['data'] + (spi_image_default_byte * pad_size)
 	spi_image += padded_data
 
-if len(spi_image) > spi_size:
-	raise RuntimeError('SPI flash image size of %d exceeds device size of %d bytes' % (len(spi_image), spi_size))
+if len(spi_image) > spi_size - 4:
+	raise RuntimeError('SPI flash image size of %d exceeds device size of %d bytes' % (len(spi_image) + 4, spi_size))
+
+pad_size = spi_size - 4 - len(spi_image)
+for i in range(pad_size):
+	spi_image += spi_image_default_byte
+
+# quick "add up the words" checksum:
+checksum = 0
+for i in range(0, len(spi_image), 4):
+	checksum += (spi_image[i] + (spi_image[i + 1] << 8) + (spi_image[i + 2] << 16) + (spi_image[i + 3] << 24))
+
+final_checksum = 0
+checksum = (final_checksum - checksum) & 0xFFFFFFFF
+
+spi_image += checksum.to_bytes(4, 'little')
 
 write_image(spi_image, output_path)
+
+percent_remaining = round(1000 * pad_size / spi_size) / 10;
+print ("Space remaining in flash ROM:", pad_size, "bytes (", percent_remaining, "%)")

firmware/tools/simple_checksum.py

@@ -0,0 +1,57 @@
+#!/usr/bin/env python3
+
+#
+# Copyright (C) 2024 Mark Thompson
+#
+# This file is part of PortaPack.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; see the file COPYING.  If not, write to
+# the Free Software Foundation, Inc., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+#
+
+import sys
+import struct
+
+usage_message = """
+PortaPack ROM image checksum checker
+
+Usage: <command> <input-file>
+"""
+
+def read_image(path):
+	f = open(path, 'rb')
+	data = f.read()
+	f.close()
+	return data
+
+def write_image(data, path):
+	f = open(path, 'wb')
+	f.write(data)
+	f.close()
+
+if len(sys.argv) != 2:
+	print(usage_message)
+	sys.exit(-1)
+
+image = read_image(sys.argv[1])
+image = bytearray(image)
+
+# simple "add up the words" checksum:
+checksum = 0
+for i in range(0, len(image), 4):
+	checksum += (image[i] + (image[i + 1] << 8) + (image[i + 2] << 16) + (image[i + 3] << 24))
+
+checksum &= 0xFFFFFFFF
+print ("Simple checksum =", checksum)