[RFC PATCH 02/10] This adds code to read OSTC3 firmware files.

[Anton Lundin]

This code is inspired by JeanDo ostc-companion.

Signed-off-by: Anton Lundin <glance at acc.umu.se>
---
 src/hw_ostc3.c | 120 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 120 insertions(+)

diff --git a/src/hw_ostc3.c b/src/hw_ostc3.c
index b78702c..cc1deb3 100644
--- a/src/hw_ostc3.c
+++ b/src/hw_ostc3.c
@@ -21,6 +21,7 @@
 
 #include <string.h> // memcmp, memcpy
 #include <stdlib.h> // malloc, free
+#include <stdio.h>  // FILE, fopen
 
 #include <libdivecomputer/hw_ostc3.h>
 
@@ -30,6 +31,7 @@
 #include "checksum.h"
 #include "ringbuffer.h"
 #include "array.h"
+#include "aes.h"
 
 #define ISINSTANCE(device) dc_device_isinstance((device), &hw_ostc3_device_vtable)
 
@@ -43,6 +45,7 @@
 #define SZ_VERSION    (SZ_CUSTOMTEXT + 4)
 #define SZ_MEMORY     0x200000
 #define SZ_CONFIG     4
+#define SZ_FIRMWARE   0x01E000        // 120KB
 
 #define RB_LOGBOOK_SIZE  256
 #define RB_LOGBOOK_COUNT 256
@@ -622,3 +625,120 @@ hw_ostc3_device_config_reset (dc_device_t *abstract)
 
 	return DC_STATUS_SUCCESS;
 }
+
+typedef struct hw_ostc3_firmware_t {
+	unsigned char data[SZ_FIRMWARE];
+	unsigned int checksum;
+} hw_ostc3_firmware_t;
+
+// FIXME: This key is specific to the ostc3
+// The ostc sport has another key but the same protocoll
+// How should we refactor the code for that?
+static unsigned char ostc3_key[16] = {
+	0xF1, 0xE9, 0xB0, 0x30,
+	0x45, 0x6F, 0xBE, 0x55,
+	0xFF, 0xE7, 0xF8, 0x31,
+	0x13, 0x6C, 0xF2, 0xFE
+};
+
+static unsigned int hw_ostc3_firmware_checksum(hw_ostc3_firmware_t *firmware)
+{
+	unsigned short low = 0;
+	unsigned short high = 0;
+	for(unsigned int i = 0;i < SZ_FIRMWARE;i++)
+	{
+		low  += firmware->data[i];
+		high += low;
+	}
+	return (((unsigned int)high) << 16) + low;
+}
+
+static dc_status_t
+hw_ostc3_firmware_readfile (hw_ostc3_firmware_t *firmware, dc_context_t *context, const char *filename)
+{
+	dc_status_t rc = DC_STATUS_SUCCESS;
+	FILE *fp;
+	unsigned char iv[16] = {0};
+	unsigned char tmpbuf[16] = {0};
+	unsigned char encrypted[16] = {0};
+	unsigned int bytes = 0, addr = 0, faddr = 0;
+	char checksum[4];
+
+	if (firmware == NULL) {
+		ERROR (context, "Invalid arguments.");
+		return DC_STATUS_INVALIDARGS;
+	}
+
+	// Initialize the buffers.
+	memset (firmware->data, 0xFF, sizeof (firmware->data));
+	firmware->checksum = 0;
+
+	fp = fopen (filename, "rb");
+	if (fp == NULL) {
+		ERROR (context, "Failed to open the file.");
+		return DC_STATUS_IO;
+	}
+
+	// FIXME: replace with array_convert_hex2bin
+	if (fscanf(fp, ":000000"
+			"%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx"
+			"%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx"
+			"\n",
+			iv, iv + 1, iv + 2, iv + 3, iv + 4, iv + 5, iv + 6, iv + 7,
+			iv + 8, iv + 9, iv + 10, iv + 11, iv + 12, iv + 13, iv + 14, iv + 15) != 16) {
+		fclose(fp);
+		ERROR (context, "Failed to parse header.");
+		return DC_STATUS_IO;
+	}
+	bytes += 16;
+
+	// Load the iv for AES-FCB-mode
+	AES128_ECB_encrypt(iv, ostc3_key, tmpbuf);
+
+	for(addr = 0; addr < SZ_FIRMWARE; addr += 16) {
+		// FIXME: replace with array_convert_hex2bin
+		if (fscanf(fp, ":%6x"
+					"%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx"
+					"%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx%2hhx"
+					"\n",
+					&faddr,
+					encrypted, encrypted + 1, encrypted + 2, encrypted + 3, encrypted + 4, encrypted + 5, encrypted + 6, encrypted + 7,
+					encrypted + 8, encrypted + 9, encrypted + 10, encrypted + 11, encrypted + 12, encrypted + 13, encrypted + 14, encrypted + 15) != 17) {
+			fclose(fp);
+			ERROR (context, "Failed to parse data.");
+			return DC_STATUS_IO;
+		}
+
+		if (faddr != bytes) {
+			fclose(fp);
+			ERROR (context, "Failed to data address.");
+			return DC_STATUS_IO;
+		}
+
+		// Decrypt AES-FCB data
+		for(int i=0;i < 16;i++)
+			firmware->data[addr + i] = encrypted[i] ^ tmpbuf[i];
+
+		// Run the next round of encryption
+		AES128_ECB_encrypt(encrypted, ostc3_key, tmpbuf);
+
+		bytes += 16;
+	}
+
+	// This file format contains a tail with the checksum in
+	if (fscanf(fp, ":%6x%2hhx%2hhx%2hhx%2hhx\n", &faddr, checksum, checksum + 1, checksum + 2, checksum + 3) != 5 || faddr != bytes) {
+		fclose(fp);
+		ERROR (context, "Failed to parse file tail.");
+		return DC_STATUS_IO;
+	}
+	fclose(fp);
+
+	firmware->checksum = array_uint32_le(checksum);
+
+	if (firmware->checksum != hw_ostc3_firmware_checksum(firmware)) {
+		ERROR (context, "Failed to verify file checksum.");
+		return DC_STATUS_IO;
+	}
+
+	return DC_STATUS_SUCCESS;
+}
-- 
1.9.1