fw: Add pre loaded flash app and flash data storage

- Add per app flash storage
  - Adds four data areas. An app can allocate an area. Once allocated
    the area is tied to the CDI of the app and can only be
    read/written/deallocated by the same app.
- Add two pre loaded app slots to flash
  - Load an app from the first slot at boot. The app digest must match a
    specific digest specified in firmware.
  - Optionally load an app from the second slot
- Add a resetinfo area in FW_RAM which is used to signal an app's intent
  of resetting the system and, optionally, pass data to firmware or the
  next app in a bootchain.

Co-authored-by: Jonas Thörnblad <jonas@tillitis.se>
Co-authored-by: Mikael Ågren <mikael@tillitis.se>
Co-authored-by: Daniel Jobson <jobson@tillitis.se>

hw/application_fpga/fw/tk1/auth_app.c

@@ -0,0 +1,77 @@
+// Copyright (C) 2024 - Tillitis AB
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <tkey/assert.h>
+#include <tkey/lib.h>
+#include <tkey/tk1_mem.h>
+
+#include "auth_app.h"
+#include "blake2s/blake2s.h"
+#include "partition_table.h"
+#include "rng.h"
+
+static volatile uint32_t *cdi = (volatile uint32_t *)TK1_MMIO_TK1_CDI_FIRST;
+
+/* Calculates the authentication digest based on a supplied nonce and the CDI.
+ * Requires that the CDI is already calculated and stored */
+static void calculate_auth_digest(uint8_t *nonce, uint8_t *auth_digest)
+{
+	assert(nonce != NULL);
+	assert(auth_digest != NULL);
+
+	blake2s_ctx ctx = {0};
+
+	// Generate a 16 byte authentication digest
+	int blake2err = blake2s_init(&ctx, 16, NULL, 0);
+	assert(blake2err == 0);
+	blake2s_update(&ctx, (const void *)cdi, 32);
+	blake2s_update(&ctx, nonce, 16);
+	blake2s_final(&ctx, auth_digest);
+}
+
+/* Generates a 16 byte nonce */
+static void generate_nonce(uint32_t *nonce)
+{
+	assert(nonce != NULL);
+
+	for (uint8_t i = 0; i < 4; i++) {
+		nonce[i] = rng_get_word();
+	}
+	return;
+}
+
+/* Returns the authentication digest and random nonce. Requires that the CDI is
+ * already calculated and stored */
+void auth_app_create(struct auth_metadata *auth_table)
+{
+	assert(auth_table != NULL);
+
+	uint8_t nonce[16] = {0};
+	uint8_t auth_digest[16] = {0};
+
+	generate_nonce((uint32_t *)nonce);
+
+	calculate_auth_digest(nonce, auth_digest);
+
+	memcpy_s(auth_table->authentication_digest, 16, auth_digest, 16);
+	memcpy_s(auth_table->nonce, 16, nonce, 16);
+
+	return;
+}
+
+bool auth_app_authenticate(struct auth_metadata *auth_table)
+{
+	assert(auth_table != NULL);
+
+	uint8_t auth_digest[16] = {0};
+
+	calculate_auth_digest(auth_table->nonce, auth_digest);
+
+	if (memeq(auth_digest, auth_table->authentication_digest, 16)) {
+		return true;
+	}
+
+	return false;
+}