From 3e8ff9671c740f6fa430d12cd0edd5be35aafa33 Mon Sep 17 00:00:00 2001
From: Michael Cardell Widerkrantz <mc@tillitis.se>
Date: Fri, 25 Apr 2025 16:36:19 +0200
Subject: [PATCH] fw/tools: Change partition checksum to vanilla BLAKE2s
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Instead of using 16 byte BLAKE2s with a dummy key, use plain vanilla
unkeyed 32 byte BLAKE2s for partition checksum.

Co-authored-by: Mikael Ågren <mikael@tillitis.se>
---
 hw/application_fpga/fw/tk1/partition_table.c  |  6 +-----
 hw/application_fpga/fw/tk1/partition_table.h  |  2 +-
 .../tools/partition_table/partition_table.go  | 21 +++----------------
 3 files changed, 5 insertions(+), 24 deletions(-)

diff --git a/hw/application_fpga/fw/tk1/partition_table.c b/hw/application_fpga/fw/tk1/partition_table.c
index 0f35d62..110719a 100644
--- a/hw/application_fpga/fw/tk1/partition_table.c
+++ b/hw/application_fpga/fw/tk1/partition_table.c
@@ -27,14 +27,10 @@ static void part_checksum(struct partition_table *part_table,
 {
 	int blake2err = 0;
 
-	uint8_t key[16] = {
-	    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-	};
-
 	assert(part_table != NULL);
 	assert(out_digest != NULL);
 
-	blake2err = blake2s(out_digest, out_len, key, sizeof(key), part_table,
+	blake2err = blake2s(out_digest, out_len, NULL, 0, part_table,
 			    sizeof(struct partition_table));
 
 	assert(blake2err == 0);
diff --git a/hw/application_fpga/fw/tk1/partition_table.h b/hw/application_fpga/fw/tk1/partition_table.h
index 04ca116..f45ff92 100644
--- a/hw/application_fpga/fw/tk1/partition_table.h
+++ b/hw/application_fpga/fw/tk1/partition_table.h
@@ -46,7 +46,7 @@
 #define SIZE_STORAGE_AREA 0x20000UL // 128KiB
 #define N_STORAGE_AREA 4
 
-#define PART_CHECKSUM_SIZE 16
+#define PART_CHECKSUM_SIZE 32
 
 enum part_status {
 	PART_SLOT0_INVALID = 1,
diff --git a/hw/application_fpga/tools/partition_table/partition_table.go b/hw/application_fpga/tools/partition_table/partition_table.go
index b2f556d..2903f11 100644
--- a/hw/application_fpga/tools/partition_table/partition_table.go
+++ b/hw/application_fpga/tools/partition_table/partition_table.go
@@ -34,7 +34,7 @@ type PartTable struct {
 
 type PartTableStorage struct {
 	PartTable PartTable
-	Digest    [16]uint8
+	Checksum  [32]byte
 }
 
 type Flash struct {
@@ -85,21 +85,7 @@ func printPartTableStorageCondensed(storage PartTableStorage) {
 		fmt.Printf("                         %x\n", appData.Signature[32:48])
 		fmt.Printf("                         %x\n", appData.Signature[48:])
 	}
-	fmt.Printf("  Digest               : %x\n", storage.Digest)
-}
-
-func calculateStorageDigest(data []byte) []byte {
-	key := [16]byte{}
-
-	hash, err := blake2s.New128(key[:])
-	if err != nil {
-		panic(err)
-	}
-
-	hash.Write(data)
-	digest := hash.Sum([]byte{})
-
-	return digest
+	fmt.Printf("  Digest               : %x\n", storage.Checksum)
 }
 
 func generatePartTableStorage(outputFilename string, app0Filename string) {
@@ -125,8 +111,7 @@ func generatePartTableStorage(outputFilename string, app0Filename string) {
 		panic(err)
 	}
 
-	digest := calculateStorageDigest(buf[:len])
-	copy(storage.Digest[:], digest)
+	storage.Checksum = blake2s.Sum256(buf[:len])
 
 	storageFile, err := os.Create(outputFilename)
 	if err != nil {