add functions to alter easycard log records and mifare value blocks

easytool/Makefile

@@ -6,7 +6,7 @@ all:	easytool
 clean:
 	@rm -f *.o easytool
 
-easytool: easytool.o data.o utils.o mifare_classic.o
+easytool: easytool.o easycard.o data.o utils.o mifare_classic.o
 	$(CC) $(LDFLAGS) -o $@ $^
 
 %.o:	%.c

easytool/easycard.c

@@ -0,0 +1,77 @@
+/* A reverse-engineered implementation of the EasyCard data format */
+
+/* (C) 2010 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved
+ *
+ * This program 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
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+/* System includes */
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <fcntl.h>
+#include <string.h>
+#include <time.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <netinet/in.h>
+
+/* libnfc includes */
+#include <nfc/nfc-types.h>
+#include <nfc/mifaretag.h>
+
+#include "mifare_classic.h"
+
+/* Easycard specific includes */
+#include "easycard.h"
+
+time_t easy_timestamp2time(const uint8_t *easy_ts)
+{
+	return (easy_ts[2] << 16 | easy_ts[1] << 8 | easy_ts[0]) << 8;
+}
+
+/* apply a telta (positive or negative) to a EasyCard log record */
+int easy_update_log_rec(struct easy_log_rec *elr, int16_t delta)
+{
+	int32_t sum = elr->amount + delta;
+	int32_t remaining = elr->remaining = delta;
+
+	if ((sum < 0 || sum > 0xffff) ||
+	    (remaining < 0 || remaining > 0xffff))
+		return -ERANGE;
+
+	elr->amount = sum;
+	elr->remaining = remaining;
+
+	return 0;
+}
+
+static char tsbuf[64];
+char *easy_asc_timestamp(const uint8_t *timestamp)
+{
+	time_t t_time = easy_timestamp2time(timestamp);
+	struct tm *t_tm = gmtime(&t_time);
+	memset(tsbuf, 0, sizeof(tsbuf));
+	snprintf(tsbuf, sizeof(tsbuf), "%4u-%02u-%02u %02u:%02u",
+		t_tm->tm_year+1900, t_tm->tm_mon+1, t_tm->tm_mday,
+		t_tm->tm_hour, t_tm->tm_min);
+	return tsbuf;
+}
+

easytool/easycard.h

@@ -11,4 +11,37 @@
 extern const struct value_string easy_tt_names[];
 extern const struct value_string taipei_mrt_stn_id[];
 
+/* Sector 0 of Block 2 seems to contain manufacturing timestamp */
+struct easy_block2sec0 {
+	uint8_t unknown[6];
+	uint8_t timestamp[3];
+	uint8_t unknown2[7];
+} __attribute__ ((packed));
+
+/* Sector 2 of Block 15 */
+struct easy_block15sec2 {
+	uint8_t unknown[11];
+	uint8_t day_of_month;
+	uint8_t unknown2;	/* always 0x3d? */
+	uint16_t sum_of_day;	/* sum of all shop purchases on a day */
+	uint8_t unknown3;
+} __attribute__ ((packed));
+
+
+/* storage of a transaction log record on the transponder itself */
+struct easy_log_rec {
+	uint8_t trans_id;
+	uint8_t unknown;
+	uint8_t timestamp[3];	/* seconds since January 1st 1970 / 256 */
+	uint8_t trans_type;
+	uint16_t amount;	/* transaction amount / value */
+	uint16_t remaining;	/* remaining value on card _after_ trans */
+	uint8_t unknown2;
+	uint8_t station_code;	/* MRT station code */
+	uint16_t reader_code;	/* unique code of RFID reader */
+	uint8_t unknown3[2];
+} __attribute__ ((packed));
+
+time_t easy_timestamp2time(const uint8_t *easy_ts);
+
 #endif /* EASYCARD_H */

easytool/easytool.c

@@ -54,62 +54,6 @@ struct {
 	mifare_tag *mft;
 } global;
 
-/* Sector 0 of Block 2 seems to contain manufacturing timestamp */
-struct easy_block2sec0 {
-	uint8_t unknown[6];
-	uint8_t timestamp[3];
-	uint8_t unknown2[7];
-} __attribute__ ((packed));
-
-/* Sector 2 of Block 15 */
-struct easy_block15sec2 {
-	uint8_t unknown[11];
-	uint8_t day_of_month;
-	uint8_t unknown2;	/* always 0x3d? */
-	uint16_t sum_of_day;	/* sum of all shop purchases on a day */
-	uint8_t unknown3;
-} __attribute__ ((packed));
-
-
-/* storage of a transaction log record on the transponder itself */
-struct easy_log_rec {
-	uint8_t trans_id;
-	uint8_t unknown;
-	uint8_t timestamp[3];	/* seconds since January 1st 1970 / 256 */
-	uint8_t trans_type;
-	uint16_t amount;	/* transaction amount / value */
-	uint16_t remaining;	/* remaining value on card _after_ trans */
-	uint8_t unknown2;
-	uint8_t station_code;	/* MRT station code */
-	uint16_t reader_code;	/* unique code of RFID reader */
-	uint8_t unknown3[2];
-} __attribute__ ((packed));
-
-/* Mifare classic VALUE BLOCK */
-struct mfcl_value_block {
-	uint32_t value;		/* value in NTD */
-	uint32_t value_inv;	/* bit-inverted copy of value in NTD */
-	uint32_t value_backup;	/* backup copy of value in NTD */
-	uint8_t addr[4];
-} __attribute__ ((packed));
-
-static time_t easy_timestamp2time(const uint8_t *easy_ts)
-{
-	return (easy_ts[2] << 16 | easy_ts[1] << 8 | easy_ts[0]) << 8;
-}
-
-static char tsbuf[64];
-char *easy_asc_timestamp(const uint8_t *timestamp)
-{
-	time_t t_time = easy_timestamp2time(timestamp);
-	struct tm *t_tm = gmtime(&t_time);
-	memset(tsbuf, 0, sizeof(tsbuf));
-	snprintf(tsbuf, sizeof(tsbuf), "%4u-%02u-%02u %02u:%02u",
-		t_tm->tm_year+1900, t_tm->tm_mon+1, t_tm->tm_mday,
-		t_tm->tm_hour, t_tm->tm_min);
-	return tsbuf;
-}
-
 static void dump_easy_log(const struct easy_log_rec *elr)
 {
 	printf("%s | %02x | %10s | Paid %4u NTD | %4u NTD remaining\n",

easytool/mifare_classic.c

@@ -1,6 +1,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>
+#include <errno.h>
 
 #include "mifare_classic.h"
 
@@ -27,3 +28,18 @@ void mfcl_parse_acc_bits(struct acc_bits_parsed *abp, uint8_t *acc_bits)
 			abp->block[block] |= ABP_C3;
 	}
 }
+
+/* apply a delta (positive or negative) to a Mifare Classic VALUE block */
+int mfcl_update_value_block(struct mfcl_value_block *mvb, int32_t delta)
+{
+	int64_t sum = mvb->value + delta;
+
+	if (sum > 0xffffffff || sum < 0)
+		return -ERANGE;
+
+	mvb->value = sum;
+	mvb->value_backup = mvb->value;
+	mvb->value_inv = ~sum;
+
+	return 0;
+}

easytool/mifare_classic.h

@@ -13,4 +13,12 @@ struct acc_bits_parsed {
 
 void mfcl_parse_acc_bits(struct acc_bits_parsed *abp, uint8_t *acc_bits);
 
+/* Mifare classic VALUE BLOCK */
+struct mfcl_value_block {
+	uint32_t value;		/* value in NTD */
+	uint32_t value_inv;	/* bit-inverted copy of value in NTD */
+	uint32_t value_backup;	/* backup copy of value in NTD */
+	uint8_t addr[4];
+} __attribute__ ((packed));
+
 #endif