From 43eddd123bad829330a572c4aa42a7b50acb3de1 Mon Sep 17 00:00:00 2001
From: schneider <schneider@blinkenlichts.net>
Date: Tue, 19 Jul 2011 01:12:53 +0200
Subject: [PATCH] filesystem: check signature of loadables with cbc-mc

---
 firmware/filesystem/execute.c | 19 +++++++++++++++++--
 firmware/filesystem/execute.h |  2 +-
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/firmware/filesystem/execute.c b/firmware/filesystem/execute.c
index 3232f02..071b910 100644
--- a/firmware/filesystem/execute.c
+++ b/firmware/filesystem/execute.c
@@ -10,11 +10,14 @@
 #include "filesystem/ff.h"
 #include "filesystem/select.h"
 
+
+const uint32_t signature_key[4] = {0,0,0,0};
+
 extern void * sram_top;
 
 /**************************************************************************/
 
-void execute_file (const char * fname){
+void execute_file (const char * fname, uint8_t checksignature){
     FRESULT res;
     FIL file;
     UINT readbytes;
@@ -27,6 +30,7 @@ void execute_file (const char * fname){
     dst=(void (*)(void)) 0x10001800;
 
     res=f_open(&file, fname, FA_OPEN_EXISTING|FA_READ);
+
     //lcdPrint("open: ");
     //lcdPrintln(f_get_rc_string(res));
     //lcdRefresh();
@@ -41,7 +45,18 @@ void execute_file (const char * fname){
     if(res){
         return;
     };
+    
+    if( checksignature ){
+        uint32_t mac[4];
+        uint32_t *data = (uint32_t*)dst;
+        uint32_t len = readbytes/4;
 
+        xxtea_cbcmac(mac, (uint32_t*)dst, len-4, signature_key);
+        if( data[len-4] != mac[0] || data[len-3] != mac[1]
+            || data[len-2] != mac[2] || data[len-1] != mac[3] ){
+            return;
+        }
+    }
     //lcdPrintInt(readbytes);
     //lcdPrintln(" bytes");
     //lcdRefresh();
@@ -60,6 +75,6 @@ void executeSelect(char *ext){
     filename[2]=0;
 
     if( selectFile(filename+2,ext) == 0)
-        execute_file(filename);
+        execute_file(filename,0);
 };
 
diff --git a/firmware/filesystem/execute.h b/firmware/filesystem/execute.h
index 7242d6d..2b4b0f1 100644
--- a/firmware/filesystem/execute.h
+++ b/firmware/filesystem/execute.h
@@ -1,7 +1,7 @@
 #ifndef _EXECUTE_H_
 #define _EXECUTE_H_
 
-void execute_file (const char * fname);
+void execute_file (const char * fname, uint8_t checksignature);
 void executeSelect(char *ext);
 
 #endif