From a783671c72aa4b9fde5bf7a2af3bf11a7c876191 Mon Sep 17 00:00:00 2001
From: Othmar Gsenger <otti@wirdorange.org>
Date: Wed, 6 Feb 2013 20:56:51 +0000
Subject: moved keystore and usb/serial to seperate files stdio_ptr might need
 some improvement

git-svn-id: https://svn.spreadspace.org/avr/trunk@134 aa12f405-d877-488e-9caf-2d797e2a1cc7
---
 usb-i2c-sl018/keystore.c | 109 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100644 usb-i2c-sl018/keystore.c

(limited to 'usb-i2c-sl018/keystore.c')

diff --git a/usb-i2c-sl018/keystore.c b/usb-i2c-sl018/keystore.c
new file mode 100644
index 0000000..1d8a5db
--- /dev/null
+++ b/usb-i2c-sl018/keystore.c
@@ -0,0 +1,109 @@
+/*
+ *  spreadspace avr utils
+ *
+ *
+ *  Copyright (C) 2013 Christian Pointner <equinox@spreadspace.org>
+ *                     Othmar Gsenger <otti@wirdorange.org>
+ *
+ *  This file is part of spreadspace avr utils.
+ *
+ *  spreadspace avr utils 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 3 of the License, or
+ *  any later version.
+ *
+ *  spreadspace avr utils 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 spreadspace avr utils. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "keystore.h"
+#include <avr/eeprom.h>
+#include <stdio.h>
+#include "usb_serial.h"
+#include "led.h"
+
+#define EEPROM_SIZE 1024
+typedef uint8_t keyslot_t[8];
+keyslot_t EEMEM keystore[EEPROM_SIZE/sizeof(keyslot_t)];
+
+
+void flash_keystore_from_stdio(FILE * stdio)
+{
+  keyslot_t ks;
+  uint8_t byte_pos=0;
+  fprintf(stdio,"Flashing keys:\n\r");
+  fflush(stdio);
+  for(uint8_t ks_pos=0;ks_pos<EEPROM_SIZE/sizeof(ks);) {
+    usb_serial_task();
+
+    int16_t bytes_received = usb_serial_bytes_received();
+    while(bytes_received > 0) {
+      ks[byte_pos++]=fgetc(stdio);
+      bytes_received--;
+      if (byte_pos == sizeof(ks)) {
+        byte_pos=0;
+        eeprom_update_block(&ks,&keystore[ks_pos],sizeof(ks));
+        ks_pos++;
+        fputc('.', stdio);
+        fflush(stdio);
+        led_toggle();
+      }
+    }
+  }
+  fprintf(stdio,"\n");
+  fputc(0, stdio);
+  led_off();
+}
+
+void dump_keystore_to_stdio(FILE * stdio)
+{
+  keyslot_t ks;
+  for(uint8_t ks_pos=0;ks_pos<EEPROM_SIZE/sizeof(ks);ks_pos++) {
+    eeprom_read_block(&ks,&keystore[ks_pos],sizeof(ks));
+    for (uint8_t i=0; i< sizeof(ks); i++)
+      fprintf(stdio,"%02X",ks[i]);
+    fprintf(stdio,"\n\r");
+  }
+}
+
+/* this generates a Fletcher8 checksum  */
+/* code from: http://stackoverflow.com/questions/13491700/8-bit-fletcher-checksum-of-16-byte-data */
+uint8_t generate_csum(uint8_t* data)
+{
+  uint16_t sum1 = 0xf, sum2 = 0xf, len = sizeof(keyslot_t) - 1;
+  do { sum2 += ( sum1 += *data++ ); } while (--len);
+  return sum2<<4 | sum1;
+}
+
+uint8_t compare_keyslots(const keyslot_t a, const keyslot_t b)
+{
+  uint8_t tmp=0;
+      // constant time compare
+  for(uint8_t i=0; i<sizeof(keyslot_t); ++i)
+    tmp |= a[i] ^ b[i];
+  return tmp;
+}
+
+uint8_t keystore_check_card(const uint8_t * uid, uint8_t uid_len)
+{
+  keyslot_t card, ks;
+  memset(card, 0, sizeof(card));
+  for (uint8_t pos=0; pos<uid_len; pos++)
+    card[pos]=uid[uid_len-pos-1];
+  card[sizeof(keyslot_t)-1]=generate_csum(card);
+  uint8_t valid=0;
+  for(uint8_t ks_pos=0;ks_pos<(EEPROM_SIZE/sizeof(ks));ks_pos++) {
+    eeprom_read_block(&ks,&keystore[ks_pos],sizeof(ks));
+    if(!compare_keyslots(card, ks)) {
+      valid=1;
+      // break;  // this would break security (not constant time)
+    }
+  }
+  return valid;
+}
+
-- 
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