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Fix MAD CRC algorithm.

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The CRC algorithm is not a standard CRC algorithm so rename it to nxp_crc() and adjust all related code.
This commit is contained in:
Romain Tartiere 2010-03-18 21:03:07 +00:00
parent 42692ccf54
commit feb240ee73
3 changed files with 110 additions and 136 deletions
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2
libfreefare/freefare_internal.h
View file

@ -39,7 +39,7 @@
struct mad_sector_0x00; struct mad_sector_0x00;
struct mad_sector_0x10; struct mad_sector_0x10;
void crc8 (uint8_t *crc, const uint8_t value); void nxp_crc (uint8_t *crc, const uint8_t value);
MifareTag mifare_classic_tag_new (void); MifareTag mifare_classic_tag_new (void);
void mifare_classic_tag_free (MifareTag tag); void mifare_classic_tag_free (MifareTag tag);
MifareTag mifare_ultralight_tag_new (void); MifareTag mifare_ultralight_tag_new (void);

31
libfreefare/mad.c
View file

@ -38,15 +38,10 @@
#include "freefare_internal.h" #include "freefare_internal.h"
/* /*
* XXX The documentation says the preset is 0xE3, but the various card dumps * The documentation says the preset is 0xE3 but the bits have to be mirrored:
* and the documentation example MAD CRC can be verified only with a CRC * 0xe3 = 1110 0011 <=> 1100 0111 = 0xc7
* preset of 0x67.
*
* This is still under investigation:
* http://www.libnfc.org/community/post/667/
* http://discussion.forum.nokia.com/forum/showthread.php?t=181702#14
*/ */
#define CRC_PRESET 0x67 #define CRC_PRESET 0xc7
#define SECTOR_0X00_AIDS 15 #define SECTOR_0X00_AIDS 15
#define SECTOR_0X10_AIDS 23 #define SECTOR_0X10_AIDS 23
@ -96,15 +91,15 @@ mad_new (uint8_t version)
* Compute CRC. * Compute CRC.
*/ */
void void
crc8 (uint8_t *crc, const uint8_t value) nxp_crc (uint8_t *crc, const uint8_t value)
{ {
/* x^8 + x^4 + x^3 + x^2 + 1 => 0x11d */ /* x^8 + x^4 + x^3 + x^2 + 1 => 0x11d */
const uint8_t poly = 0x1d; const uint8_t poly = 0x1d;
*crc ^= value;
for (int current_bit = 7; current_bit >= 0; current_bit--) { for (int current_bit = 7; current_bit >= 0; current_bit--) {
int bit_out = (*crc) & 0x80; int bit_out = (*crc) & 0x80;
*crc = ((*crc) << 1) | (( value >> (current_bit)) & 0x01); *crc <<= 1;
if (bit_out) if (bit_out)
*crc ^= poly; *crc ^= poly;
@ -116,13 +111,12 @@ sector_0x00_crc8 (Mad mad)
{ {
uint8_t crc = CRC_PRESET; uint8_t crc = CRC_PRESET;
crc8 (&crc, mad->sector_0x00.info); nxp_crc (&crc, mad->sector_0x00.info);
for (int n = 0; n < SECTOR_0X00_AIDS; n++) { for (int n = 0; n < SECTOR_0X00_AIDS; n++) {
crc8 (&crc, mad->sector_0x00.aids[n].application_code); nxp_crc (&crc, mad->sector_0x00.aids[n].application_code);
crc8 (&crc, mad->sector_0x00.aids[n].function_cluster_code); nxp_crc (&crc, mad->sector_0x00.aids[n].function_cluster_code);
} }
crc8 (&crc, 0x00);
return crc; return crc;
} }
@ -132,13 +126,12 @@ sector_0x10_crc8 (Mad mad)
{ {
uint8_t crc = CRC_PRESET; uint8_t crc = CRC_PRESET;
crc8 (&crc, mad->sector_0x10.info); nxp_crc (&crc, mad->sector_0x10.info);
for (int n = 0; n < SECTOR_0X10_AIDS; n++) { for (int n = 0; n < SECTOR_0X10_AIDS; n++) {
crc8 (&crc, mad->sector_0x10.aids[n].application_code); nxp_crc (&crc, mad->sector_0x10.aids[n].application_code);
crc8 (&crc, mad->sector_0x10.aids[n].function_cluster_code); nxp_crc (&crc, mad->sector_0x10.aids[n].function_cluster_code);
} }
crc8 (&crc, 0x00);
return crc; return crc;
} }

213
test/test_mad.c
View file

@ -67,7 +67,7 @@ test_mad (void)
mad_free (mad); mad_free (mad);
} }
#define CRC_PRESET 0x67 #define CRC_PRESET 0xc7
void void
test_mad_crc8_basic (void) test_mad_crc8_basic (void)
@ -75,30 +75,14 @@ test_mad_crc8_basic (void)
uint8_t crc; uint8_t crc;
const uint8_t crc_value = 0x42; const uint8_t crc_value = 0x42;
/* Insert data */
crc = 0x00;
crc8(&crc, crc_value);
cut_assert_equal_int (crc_value, crc, cut_message ("Initialization should not produce a CRC"));
/* Insert data with leading zeros */
crc = 0x00;
crc8(&crc, 0x00);
crc8(&crc, 0x00);
crc8(&crc, 0x00);
crc8(&crc, 0x00);
crc8(&crc, 0x00);
crc8(&crc, crc_value);
cut_assert_equal_int (crc_value, crc, cut_message ("Burst error should not be detected with uninitialized polies"));
/* Check integrity */ /* Check integrity */
crc = CRC_PRESET; crc = CRC_PRESET;
crc8(&crc, crc_value); nxp_crc(&crc, crc_value);
crc8(&crc, 0x00);
uint8_t save = crc; uint8_t save = crc;
crc = CRC_PRESET; crc = CRC_PRESET;
crc8(&crc, crc_value); nxp_crc(&crc, crc_value);
crc8(&crc, save); nxp_crc(&crc, save);
cut_assert_equal_int (0x00, crc, cut_message ("CRC should verify crc(message + crc(message)) = 0")); cut_assert_equal_int (0x00, crc, cut_message ("CRC should verify crc(message + crc(message)) = 0"));
} }
@ -112,46 +96,45 @@ test_mad_crc8_doc_example (void)
uint8_t crc = CRC_PRESET; uint8_t crc = CRC_PRESET;
/* Block 1 -- 0x01 - 0x07 */ /* Block 1 -- 0x01 - 0x07 */
crc8(&crc, 0x01); nxp_crc(&crc, 0x01);
crc8(&crc, 0x01); nxp_crc(&crc, 0x01);
crc8(&crc, 0x08); nxp_crc(&crc, 0x08);
crc8(&crc, 0x01); nxp_crc(&crc, 0x01);
crc8(&crc, 0x08); nxp_crc(&crc, 0x08);
crc8(&crc, 0x01); nxp_crc(&crc, 0x01);
crc8(&crc, 0x08); nxp_crc(&crc, 0x08);
/* Block 2 -- 0x08 - 0x0f */ /* Block 2 -- 0x08 - 0x0f */
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x04); nxp_crc(&crc, 0x04);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
/* Block 3 -- 0x00 - 0x07 */ /* Block 3 -- 0x00 - 0x07 */
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0x10); nxp_crc(&crc, 0x10);
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0x10); nxp_crc(&crc, 0x10);
crc8(&crc, 0x02); nxp_crc(&crc, 0x02);
crc8(&crc, 0x10); nxp_crc(&crc, 0x10);
crc8(&crc, 0x02); nxp_crc(&crc, 0x02);
crc8(&crc, 0x10); nxp_crc(&crc, 0x10);
/* Block 3 -- 0x08 - 0x0f */ /* Block 3 -- 0x08 - 0x0f */
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x11); nxp_crc(&crc, 0x11);
crc8(&crc, 0x30); nxp_crc(&crc, 0x30);
/* Append zeros of augmented message */ /* Append zeros of augmented message */
crc8(&crc, 0x00);
cut_assert_equal_int (0x89, crc, cut_message ("Sample CRC should match")); cut_assert_equal_int (0x89, crc, cut_message ("Sample CRC should match"));
} }
@ -166,46 +149,45 @@ test_mad_crc8_real_example_1 (void)
uint8_t crc = CRC_PRESET; uint8_t crc = CRC_PRESET;
/* Block 1 -- 0x01 - 0x07 */ /* Block 1 -- 0x01 - 0x07 */
crc8(&crc, 0x01); nxp_crc(&crc, 0x01);
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0xe1); nxp_crc(&crc, 0xe1);
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0xe1); nxp_crc(&crc, 0xe1);
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0xe1); nxp_crc(&crc, 0xe1);
/* Block 2 -- 0x08 - 0x0f */ /* Block 2 -- 0x08 - 0x0f */
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0xe1); nxp_crc(&crc, 0xe1);
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0xe1); nxp_crc(&crc, 0xe1);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
/* Block 3 -- 0x00 - 0x07 */ /* Block 3 -- 0x00 - 0x07 */
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
/* Block 3 -- 0x08 - 0x0f */ /* Block 3 -- 0x08 - 0x0f */
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
/* Append zeros of augmented message */ /* Append zeros of augmented message */
crc8(&crc, 0x00);
cut_assert_equal_int (0xc4, crc, cut_message ("Read example 1 CRC should match")); cut_assert_equal_int (0xc4, crc, cut_message ("Read example 1 CRC should match"));
} }
@ -220,46 +202,45 @@ test_mad_crc8_real_example_2 (void)
uint8_t crc = CRC_PRESET; uint8_t crc = CRC_PRESET;
/* Block 1 -- 0x01 - 0x07 */ /* Block 1 -- 0x01 - 0x07 */
crc8(&crc, 0x01); nxp_crc(&crc, 0x01);
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0xe1); nxp_crc(&crc, 0xe1);
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0xe1); nxp_crc(&crc, 0xe1);
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0xe1); nxp_crc(&crc, 0xe1);
/* Block 2 -- 0x08 - 0x0f */ /* Block 2 -- 0x08 - 0x0f */
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0xe1); nxp_crc(&crc, 0xe1);
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0xe1); nxp_crc(&crc, 0xe1);
crc8(&crc, 0x03); nxp_crc(&crc, 0x03);
crc8(&crc, 0xe1); nxp_crc(&crc, 0xe1);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
/* Block 3 -- 0x00 - 0x07 */ /* Block 3 -- 0x00 - 0x07 */
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
/* Block 3 -- 0x08 - 0x0f */ /* Block 3 -- 0x08 - 0x0f */
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
crc8(&crc, 0x00); nxp_crc(&crc, 0x00);
/* Append zeros of augmented message */ /* Append zeros of augmented message */
crc8(&crc, 0x00);
cut_assert_equal_int (0xab, crc, cut_message ("Read example 1 CRC should match")); cut_assert_equal_int (0xab, crc, cut_message ("Read example 1 CRC should match"));
} }