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hitag2.c
1845 lines (1614 loc) · 52.7 KB
/
hitag2.c
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//-----------------------------------------------------------------------------
// This code is licensed to you under the terms of the GNU GPL, version 2 or,
// at your option, any later version. See the LICENSE.txt file for the text of
// the license.
//-----------------------------------------------------------------------------
// Hitag2 emulation (preliminary test version)
//
// (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
//-----------------------------------------------------------------------------
// Hitag2 complete rewrite of the code
// - Fixed modulation/encoding issues
// - Rewrote code for transponder emulation
// - Added snooping of transponder communication
// - Added reader functionality
//
// (c) 2012 Roel Verdult
//-----------------------------------------------------------------------------
#include "hitag2.h"
#include "proxmark3.h"
#include "usb_cdc.h"
#include "apps.h"
#include "util.h"
#include "hitag.h"
#include "string.h"
#include "BigBuf.h"
#include "fpgaloader.h"
#include "protocols.h"
static bool bQuiet;
static bool bCrypto;
static bool bAuthenticating;
static bool bPwd;
static bool bSuccessful;
struct hitag2_tag {
uint32_t uid;
enum {
TAG_STATE_RESET = 0x01, // Just powered up, awaiting GetSnr
TAG_STATE_ACTIVATING = 0x02 , // In activation phase (password mode), sent UID, awaiting reader password
TAG_STATE_ACTIVATED = 0x03, // Activation complete, awaiting read/write commands
TAG_STATE_WRITING = 0x04, // In write command, awaiting sector contents to be written
} state;
unsigned int active_sector;
uint8_t crypto_active;
uint64_t cs;
uint8_t sectors[12][4];
};
static struct hitag2_tag tag = {
.state = TAG_STATE_RESET,
.sectors = { // Password mode: | Crypto mode:
[0] = { 0x02, 0x4e, 0x02, 0x20}, // UID | UID
[1] = { 0x4d, 0x49, 0x4b, 0x52}, // Password RWD | 32 bit LSB key
[2] = { 0x20, 0xf0, 0x4f, 0x4e}, // Reserved | 16 bit MSB key, 16 bit reserved
[3] = { 0x0e, 0xaa, 0x48, 0x54}, // Configuration, password TAG | Configuration, password TAG
[4] = { 0x46, 0x5f, 0x4f, 0x4b}, // Data: F_OK
[5] = { 0x55, 0x55, 0x55, 0x55}, // Data: UUUU
[6] = { 0xaa, 0xaa, 0xaa, 0xaa}, // Data: ....
[7] = { 0x55, 0x55, 0x55, 0x55}, // Data: UUUU
[8] = { 0x00, 0x00, 0x00, 0x00}, // RSK Low
[9] = { 0x00, 0x00, 0x00, 0x00}, // RSK High
[10] = { 0x00, 0x00, 0x00, 0x00}, // RCF
[11] = { 0x00, 0x00, 0x00, 0x00}, // SYNC
},
};
static enum {
WRITE_STATE_START = 0x0,
WRITE_STATE_PAGENUM_WRITTEN,
WRITE_STATE_PROG
} writestate;
// ToDo: define a meaningful maximum size for auth_table. The bigger this is, the lower will be the available memory for traces.
// Historically it used to be FREE_BUFFER_SIZE, which was 2744.
#define AUTH_TABLE_LENGTH 2744
static uint8_t *auth_table;
static size_t auth_table_pos = 0;
static size_t auth_table_len = AUTH_TABLE_LENGTH;
static uint8_t password[4];
static uint8_t NrAr[8];
static uint8_t key[8];
static uint8_t writedata[4];
static uint64_t cipher_state;
/* Following is a modified version of cryptolib.com/ciphers/hitag2/ */
// Software optimized 48-bit Philips/NXP Mifare Hitag2 PCF7936/46/47/52 stream cipher algorithm by I.C. Wiener 2006-2007.
// For educational purposes only.
// No warranties or guarantees of any kind.
// This code is released into the public domain by its author.
// Single bit Hitag2 functions:
#define i4(x,a,b,c,d) ((uint32_t)((((x)>>(a))&1)+(((x)>>(b))&1)*2+(((x)>>(c))&1)*4+(((x)>>(d))&1)*8))
static const uint32_t ht2_f4a = 0x2C79; // 0010 1100 0111 1001
static const uint32_t ht2_f4b = 0x6671; // 0110 0110 0111 0001
static const uint32_t ht2_f5c = 0x7907287B; // 0111 1001 0000 0111 0010 1000 0111 1011
static uint32_t _f20(const uint64_t x) {
uint32_t i5;
i5 = ((ht2_f4a >> i4(x, 1, 2, 4, 5)) & 1) * 1
+ ((ht2_f4b >> i4(x, 7,11,13,14)) & 1) * 2
+ ((ht2_f4b >> i4(x,16,20,22,25)) & 1) * 4
+ ((ht2_f4b >> i4(x,27,28,30,32)) & 1) * 8
+ ((ht2_f4a >> i4(x,33,42,43,45)) & 1) * 16;
return (ht2_f5c >> i5) & 1;
}
static uint64_t _hitag2_init(const uint64_t key, const uint32_t serial, const uint32_t IV) {
uint32_t i;
uint64_t x = ((key & 0xFFFF) << 32) + serial;
for (i = 0; i < 32; i++) {
x >>= 1;
x += (uint64_t)(_f20(x) ^ (((IV >> i) ^ (key >> (i+16))) & 1)) << 47;
}
return x;
}
static uint64_t _hitag2_round(uint64_t *state) {
uint64_t x = *state;
x = (x >> 1) +
((((x >> 0) ^ (x >> 2) ^ (x >> 3) ^ (x >> 6)
^ (x >> 7) ^ (x >> 8) ^ (x >> 16) ^ (x >> 22)
^ (x >> 23) ^ (x >> 26) ^ (x >> 30) ^ (x >> 41)
^ (x >> 42) ^ (x >> 43) ^ (x >> 46) ^ (x >> 47)) & 1) << 47);
*state = x;
return _f20(x);
}
static uint32_t _hitag2_byte(uint64_t *x) {
uint32_t i, c;
for (i = 0, c = 0; i < 8; i++) {
c += (uint32_t) _hitag2_round(x) << (i^7);
}
return c;
}
static int hitag2_reset(void) {
tag.state = TAG_STATE_RESET;
tag.crypto_active = 0;
return 0;
}
static int hitag2_init(void) {
hitag2_reset();
return 0;
}
static void hitag2_cipher_reset(struct hitag2_tag *tag, const uint8_t *iv) {
uint64_t key = ((uint64_t)tag->sectors[2][2]) |
((uint64_t)tag->sectors[2][3] << 8) |
((uint64_t)tag->sectors[1][0] << 16) |
((uint64_t)tag->sectors[1][1] << 24) |
((uint64_t)tag->sectors[1][2] << 32) |
((uint64_t)tag->sectors[1][3] << 40);
uint32_t uid = ((uint32_t)tag->sectors[0][0]) |
((uint32_t)tag->sectors[0][1] << 8) |
((uint32_t)tag->sectors[0][2] << 16) |
((uint32_t)tag->sectors[0][3] << 24);
uint32_t iv_ = (((uint32_t)(iv[0]))) |
(((uint32_t)(iv[1])) << 8) |
(((uint32_t)(iv[2])) << 16) |
(((uint32_t)(iv[3])) << 24);
tag->cs = _hitag2_init(REV64(key), REV32(uid), REV32(iv_));
}
static int hitag2_cipher_authenticate(uint64_t *cs, const uint8_t *authenticator_is) {
uint8_t authenticator_should[4];
authenticator_should[0] = ~_hitag2_byte(cs);
authenticator_should[1] = ~_hitag2_byte(cs);
authenticator_should[2] = ~_hitag2_byte(cs);
authenticator_should[3] = ~_hitag2_byte(cs);
return (memcmp(authenticator_should, authenticator_is, 4) == 0);
}
static int hitag2_cipher_transcrypt(uint64_t *cs, uint8_t *data, unsigned int bytes, unsigned int bits) {
int i;
for (i = 0; i < bytes; i++) data[i] ^= _hitag2_byte(cs);
for (i = 0; i < bits; i++) data[bytes] ^= _hitag2_round(cs) << (7-i);
return 0;
}
// Sam7s has several timers, we will use the source TIMER_CLOCK1 (aka AT91C_TC_CLKS_TIMER_DIV1_CLOCK)
// TIMER_CLOCK1 = MCK/2, MCK is running at 48 MHz, Timer is running at 48/2 = 24 MHz
// Hitag units (T0) have duration of 8 microseconds (us), which is 1/125000 per second (carrier)
// T0 = TIMER_CLOCK1 / 125000 = 192
#define T0 192
#define HITAG_FRAME_LEN 20
#define HITAG_T_STOP 36 /* T_EOF should be > 36 */
#define HITAG_T_LOW 8 /* T_LOW should be 4..10 */
#define HITAG_T_0_MIN 15 /* T[0] should be 18..22 */
#define HITAG_T_1_MIN 25 /* T[1] should be 26..30 */
//#define HITAG_T_EOF 40 /* T_EOF should be > 36 */
#define HITAG_T_EOF 80 /* T_EOF should be > 36 */
#define HITAG_T_WAIT_1 200 /* T_wresp should be 199..206 */
#define HITAG_T_WAIT_2 90 /* T_wresp should be 199..206 */
#define HITAG_T_WAIT_MAX 300 /* bit more than HITAG_T_WAIT_1 + HITAG_T_WAIT_2 */
#define HITAG_T_PROG 614
#define HITAG_T_TAG_ONE_HALF_PERIOD 10
#define HITAG_T_TAG_TWO_HALF_PERIOD 25
#define HITAG_T_TAG_THREE_HALF_PERIOD 41
#define HITAG_T_TAG_FOUR_HALF_PERIOD 57
#define HITAG_T_TAG_HALF_PERIOD 16
#define HITAG_T_TAG_FULL_PERIOD 32
#define HITAG_T_TAG_CAPTURE_ONE_HALF 13
#define HITAG_T_TAG_CAPTURE_TWO_HALF 25
#define HITAG_T_TAG_CAPTURE_THREE_HALF 41
#define HITAG_T_TAG_CAPTURE_FOUR_HALF 57
static void hitag_send_bit(int bit) {
LED_A_ON();
// Reset clock for the next bit
AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
// Fixed modulation, earlier proxmark version used inverted signal
if (bit == 0) {
// Manchester: Unloaded, then loaded |__--|
LOW(GPIO_SSC_DOUT);
while (AT91C_BASE_TC0->TC_CV < T0*HITAG_T_TAG_HALF_PERIOD);
HIGH(GPIO_SSC_DOUT);
while (AT91C_BASE_TC0->TC_CV < T0*HITAG_T_TAG_FULL_PERIOD);
} else {
// Manchester: Loaded, then unloaded |--__|
HIGH(GPIO_SSC_DOUT);
while (AT91C_BASE_TC0->TC_CV < T0*HITAG_T_TAG_HALF_PERIOD);
LOW(GPIO_SSC_DOUT);
while (AT91C_BASE_TC0->TC_CV < T0*HITAG_T_TAG_FULL_PERIOD);
}
LED_A_OFF();
}
static void hitag_send_frame(const uint8_t *frame, size_t frame_len)
{
// Send start of frame
for(size_t i = 0; i < 5; i++) {
hitag_send_bit(1);
}
// Send the content of the frame
for (size_t i = 0; i < frame_len; i++) {
hitag_send_bit((frame[i/8] >> (7-(i%8))) & 0x01);
}
// Drop the modulation
LOW(GPIO_SSC_DOUT);
}
static void hitag2_handle_reader_command(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen) {
uint8_t rx_air[HITAG_FRAME_LEN];
// Copy the (original) received frame how it is send over the air
memcpy(rx_air, rx, nbytes(rxlen));
if (tag.crypto_active) {
hitag2_cipher_transcrypt(&(tag.cs), rx, rxlen/8, rxlen%8);
}
// Reset the transmission frame length
*txlen = 0;
// Try to find out which command was send by selecting on length (in bits)
switch (rxlen) {
// Received 11000 from the reader, request for UID, send UID
case 05: {
// Always send over the air in the clear plaintext mode
if (rx_air[0] != HITAG2_START_AUTH) {
// Unknown frame ?
return;
}
*txlen = 32;
memcpy(tx, tag.sectors[0], 4);
tag.crypto_active = 0;
}
break;
// Read/Write command: ..xx x..y yy with yyy == ~xxx, xxx is sector number
case 10: {
unsigned int sector = (~( ((rx[0]<<2) & 0x04) | ((rx[1]>>6) & 0x03) ) & 0x07);
// Verify complement of sector index
if (sector != ((rx[0]>>3) & 0x07)) {
//DbpString("Transmission error (read/write)");
return;
}
switch (rx[0] & 0xC6) {
// Read command: 11xx x00y
case HITAG2_READ_PAGE:
memcpy(tx, tag.sectors[sector], 4);
*txlen = 32;
break;
// Inverted Read command: 01xx x10y
case HITAG2_READ_PAGE_INVERTED:
for (size_t i = 0; i < 4; i++) {
tx[i] = tag.sectors[sector][i] ^ 0xff;
}
*txlen = 32;
break;
// Write command: 10xx x01y
case HITAG2_WRITE_PAGE:
// Prepare write, acknowledge by repeating command
memcpy(tx, rx, nbytes(rxlen));
*txlen = rxlen;
tag.active_sector = sector;
tag.state = TAG_STATE_WRITING;
break;
// Unknown command
default:
Dbprintf("Unknown command: %02x %02x", rx[0], rx[1]);
return;
break;
}
}
break;
// Writing data or Reader password
case 32: {
if (tag.state == TAG_STATE_WRITING) {
// These are the sector contents to be written. We don't have to do anything else.
memcpy(tag.sectors[tag.active_sector], rx, nbytes(rxlen));
tag.state = TAG_STATE_RESET;
return;
} else {
// Received RWD password, respond with configuration and our password
if (memcmp(rx, tag.sectors[1], 4) != 0) {
DbpString("Reader password is wrong");
return;
}
*txlen = 32;
memcpy(tx, tag.sectors[3], 4);
}
}
break;
// Received RWD authentication challenge and respnse
case 64: {
// Store the authentication attempt
if (auth_table_len < (AUTH_TABLE_LENGTH-8)) {
memcpy(auth_table+auth_table_len, rx, 8);
auth_table_len += 8;
}
// Reset the cipher state
hitag2_cipher_reset(&tag, rx);
// Check if the authentication was correct
if (!hitag2_cipher_authenticate(&(tag.cs), rx+4)) {
// The reader failed to authenticate, do nothing
Dbprintf("auth: %02x%02x%02x%02x%02x%02x%02x%02x Failed!", rx[0], rx[1], rx[2], rx[3], rx[4], rx[5], rx[6], rx[7]);
return;
}
// Succesful, but commented out reporting back to the Host, this may delay to much.
// Dbprintf("auth: %02x%02x%02x%02x%02x%02x%02x%02x OK!",rx[0],rx[1],rx[2],rx[3],rx[4],rx[5],rx[6],rx[7]);
// Activate encryption algorithm for all further communication
tag.crypto_active = 1;
// Use the tag password as response
memcpy(tx, tag.sectors[3], 4);
*txlen = 32;
}
break;
}
// LogTraceHitag(rx, rxlen, 0, 0, false);
// LogTraceHitag(tx, *txlen, 0, 0, true);
if (tag.crypto_active) {
hitag2_cipher_transcrypt(&(tag.cs), tx, *txlen/8, *txlen%8);
}
}
static void hitag_reader_send_bit(int bit) {
LED_A_ON();
// Reset clock for the next bit
AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
// Binary puls length modulation (BPLM) is used to encode the data stream
// This means that a transmission of a one takes longer than that of a zero
// Enable modulation, which means, drop the field
HIGH(GPIO_SSC_DOUT);
// t_low = 4...10 carrier periods
while (AT91C_BASE_TC0->TC_CV < T0*6);
// Disable modulation, just activates the field again
LOW(GPIO_SSC_DOUT);
if (bit == 0) {
// Zero bit: |_-|, T[0] = 18...22 carrier periods
while (AT91C_BASE_TC0->TC_CV < T0*22);
} else {
// One bit: |_--|, T[1] = 26...32 carrier periods
while (AT91C_BASE_TC0->TC_CV < T0*28);
}
LED_A_OFF();
}
static void hitag_reader_send_frame(const uint8_t *frame, size_t frame_len)
{
// Send the content of the frame
for(size_t i = 0; i < frame_len; i++) {
hitag_reader_send_bit((frame[i/8] >> (7-(i%8))) & 0x01);
}
// Send EOF
AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
// Enable modulation, which means, drop the field
HIGH(GPIO_SSC_DOUT);
// t_low = 4...10 carrier periods
while (AT91C_BASE_TC0->TC_CV < T0*6);
// Disable modulation, just activates the field again
LOW(GPIO_SSC_DOUT);
// t_stop > 36 carrier periods
while (AT91C_BASE_TC0->TC_CV < T0*36);
}
size_t blocknr;
//-----------------------------------------------------------------------------
// Hitag2 operations
//-----------------------------------------------------------------------------
static bool hitag2_write_page(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen) {
switch (writestate) {
case WRITE_STATE_START:
tx[0] = HITAG2_WRITE_PAGE | (blocknr << 3) | ((blocknr^7) >> 2);
tx[1] = ((blocknr^7) << 6);
*txlen = 10;
writestate = WRITE_STATE_PAGENUM_WRITTEN;
break;
case WRITE_STATE_PAGENUM_WRITTEN:
// Check if page number was received correctly
if ((rxlen == 10)
&& (rx[0] == (HITAG2_WRITE_PAGE | (blocknr << 3) | ((blocknr^7) >> 2)))
&& (rx[1] == (((blocknr & 0x3) ^ 0x3) << 6))) {
*txlen = 32;
memset(tx, 0, HITAG_FRAME_LEN);
memcpy(tx, writedata, 4);
writestate = WRITE_STATE_PROG;
} else {
Dbprintf("hitag2_write_page: Page number was not received correctly: rxlen=%d rx=%02x%02x%02x%02x",
rxlen, rx[0], rx[1], rx[2], rx[3]);
bSuccessful = false;
return false;
}
break;
case WRITE_STATE_PROG:
if (rxlen == 0) {
bSuccessful = true;
} else {
bSuccessful = false;
Dbprintf("hitag2_write_page: unexpected rx data (%d) after page write", rxlen);
}
return false;
default:
DbpString("hitag2_write_page: Unknown state %d");
bSuccessful = false;
return false;
}
return true;
}
static bool hitag2_password(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen, bool write) {
// Reset the transmission frame length
*txlen = 0;
if (bPwd && !bAuthenticating && write) {
if (!hitag2_write_page(rx, rxlen, tx, txlen)) {
return false;
}
} else {
// Try to find out which command was send by selecting on length (in bits)
switch (rxlen) {
// No answer, try to resurrect
case 0: {
// Stop if there is no answer (after sending password)
if (bPwd) {
DbpString("Password failed!");
return false;
}
tx[0] = HITAG2_START_AUTH;
*txlen = 5;
}
break;
// Received UID, tag password
case 32: {
if (!bPwd) {
bPwd = true;
bAuthenticating = true;
memcpy(tx, password, 4);
*txlen = 32;
} else {
if (bAuthenticating) {
bAuthenticating = false;
if (write) {
if (!hitag2_write_page(rx, rxlen, tx, txlen)) {
return false;
}
break;
}
} else {
memcpy(tag.sectors[blocknr], rx, 4);
blocknr++;
}
if (blocknr > 7) {
DbpString("Read successful!");
bSuccessful = true;
return false;
}
tx[0] = HITAG2_READ_PAGE | (blocknr << 3) | ((blocknr^7) >> 2);
tx[1] = ((blocknr^7) << 6);
*txlen = 10;
}
}
break;
// Unexpected response
default: {
Dbprintf("Unknown frame length: %d", rxlen);
return false;
}
break;
}
}
return true;
}
static bool hitag2_crypto(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen, bool write) {
// Reset the transmission frame length
*txlen = 0;
if (bCrypto) {
hitag2_cipher_transcrypt(&cipher_state, rx, rxlen/8, rxlen%8);
}
if (bCrypto && !bAuthenticating && write) {
if (!hitag2_write_page(rx, rxlen, tx, txlen)) {
return false;
}
} else {
// Try to find out which command was send by selecting on length (in bits)
switch (rxlen) {
// No answer, try to resurrect
case 0: {
// Stop if there is no answer while we are in crypto mode (after sending NrAr)
if (bCrypto) {
// Failed during authentication
if (bAuthenticating) {
DbpString("Authentication failed!");
return false;
} else {
// Failed reading a block, could be (read/write) locked, skip block and re-authenticate
if (blocknr == 1) {
// Write the low part of the key in memory
memcpy(tag.sectors[1], key+2, 4);
} else if (blocknr == 2) {
// Write the high part of the key in memory
tag.sectors[2][0] = 0x00;
tag.sectors[2][1] = 0x00;
tag.sectors[2][2] = key[0];
tag.sectors[2][3] = key[1];
} else {
// Just put zero's in the memory (of the unreadable block)
memset(tag.sectors[blocknr], 0x00, 4);
}
blocknr++;
bCrypto = false;
}
} else {
tx[0] = HITAG2_START_AUTH;
*txlen = 5;
}
break;
}
// Received UID, crypto tag answer
case 32: {
if (!bCrypto) {
uint64_t ui64key = key[0] | ((uint64_t)key[1]) << 8 | ((uint64_t)key[2]) << 16 | ((uint64_t)key[3]) << 24 | ((uint64_t)key[4]) << 32 | ((uint64_t)key[5]) << 40;
uint32_t ui32uid = rx[0] | ((uint32_t)rx[1]) << 8 | ((uint32_t)rx[2]) << 16 | ((uint32_t)rx[3]) << 24;
Dbprintf("hitag2_crypto: key=0x%x%x uid=0x%x", (uint32_t) ((REV64(ui64key)) >> 32), (uint32_t) ((REV64(ui64key)) & 0xffffffff), REV32(ui32uid));
cipher_state = _hitag2_init(REV64(ui64key), REV32(ui32uid), 0);
memset(tx, 0x00, 4);
memset(tx+4, 0xff, 4);
hitag2_cipher_transcrypt(&cipher_state, tx+4, 4, 0);
*txlen = 64;
bCrypto = true;
bAuthenticating = true;
} else {
// Check if we received answer tag (at)
if (bAuthenticating) {
bAuthenticating = false;
if (write) {
if (!hitag2_write_page(rx, rxlen, tx, txlen)) {
return false;
}
break;
}
}
// stage 2+, got data block
else {
// Store the received block
memcpy(tag.sectors[blocknr], rx, 4);
blocknr++;
}
if (blocknr > 7) {
DbpString("Read successful!");
bSuccessful = true;
return false;
} else {
tx[0] = HITAG2_READ_PAGE | (blocknr << 3) | ((blocknr ^ 7) >> 2);
tx[1] = ((blocknr ^ 7) << 6);
*txlen = 10;
}
}
}
break;
// Unexpected response
default: {
Dbprintf("Unknown frame length: %d",rxlen);
return false;
}
break;
}
}
if (bCrypto) {
// We have to return now to avoid double encryption
if (!bAuthenticating) {
hitag2_cipher_transcrypt(&cipher_state, tx, *txlen/8, *txlen%8);
}
}
return true;
}
static bool hitag2_authenticate(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen) {
// Reset the transmission frame length
*txlen = 0;
// Try to find out which command was send by selecting on length (in bits)
switch (rxlen) {
// No answer, try to resurrect
case 0: {
// Stop if there is no answer while we are in crypto mode (after sending NrAr)
if (bCrypto) {
DbpString("Authentication failed!");
return false;
}
tx[0] = HITAG2_START_AUTH;
*txlen = 5;
}
break;
// Received UID, crypto tag answer
case 32: {
if (!bCrypto) {
memcpy(tx, NrAr, 8);
*txlen = 64;
bCrypto = true;
} else {
DbpString("Authentication successful!");
// We are done... for now
return false;
}
}
break;
// Unexpected response
default: {
Dbprintf("Unknown frame length: %d",rxlen);
return false;
}
break;
}
return true;
}
static bool hitag2_test_auth_attempts(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen) {
// Reset the transmission frame length
*txlen = 0;
// Try to find out which command was send by selecting on length (in bits)
switch (rxlen) {
// No answer, try to resurrect
case 0: {
// Stop if there is no answer while we are in crypto mode (after sending NrAr)
if (bCrypto) {
Dbprintf("auth: %02x%02x%02x%02x%02x%02x%02x%02x Failed, removed entry!", NrAr[0], NrAr[1], NrAr[2], NrAr[3], NrAr[4], NrAr[5], NrAr[6], NrAr[7]);
// Removing failed entry from authentiations table
memcpy(auth_table+auth_table_pos, auth_table+auth_table_pos+8, 8);
auth_table_len -= 8;
// Return if we reached the end of the authentications table
bCrypto = false;
if (auth_table_pos == auth_table_len) {
return false;
}
// Copy the next authentication attempt in row (at the same position, b/c we removed last failed entry)
memcpy(NrAr, auth_table+auth_table_pos, 8);
}
tx[0] = HITAG2_START_AUTH;
*txlen = 5;
}
break;
// Received UID, crypto tag answer, or read block response
case 32: {
if (!bCrypto) {
*txlen = 64;
memcpy(tx, NrAr, 8);
bCrypto = true;
} else {
Dbprintf("auth: %02x%02x%02x%02x%02x%02x%02x%02x OK", NrAr[0], NrAr[1], NrAr[2], NrAr[3], NrAr[4], NrAr[5], NrAr[6], NrAr[7]);
bCrypto = false;
if ((auth_table_pos+8) == auth_table_len) {
return false;
}
auth_table_pos += 8;
memcpy(NrAr, auth_table+auth_table_pos, 8);
}
}
break;
default: {
Dbprintf("Unknown frame length: %d",rxlen);
return false;
}
break;
}
return true;
}
static bool hitag2_read_uid(uint8_t *rx, const size_t rxlen, uint8_t *tx, size_t *txlen) {
// Reset the transmission frame length
*txlen = 0;
// Try to find out which command was send by selecting on length (in bits)
switch (rxlen) {
// No answer, try to resurrect
case 0: {
// Just starting or if there is no answer
tx[0] = HITAG2_START_AUTH;
*txlen = 5;
}
break;
// Received UID
case 32: {
// Check if we received answer tag (at)
if (bAuthenticating) {
bAuthenticating = false;
} else {
// Store the received block
memcpy(tag.sectors[blocknr], rx, 4);
blocknr++;
}
if (blocknr > 0) {
//DbpString("Read successful!");
bSuccessful = true;
return false;
}
}
break;
// Unexpected response
default: {
Dbprintf("Unknown frame length: %d",rxlen);
return false;
}
break;
}
return true;
}
void SnoopHitag(uint32_t type) {
// int frame_count;
int response;
int overflow;
bool rising_edge;
bool reader_frame;
int lastbit;
bool bSkip;
int tag_sof;
uint8_t rx[HITAG_FRAME_LEN] = {0};
size_t rxlen = 0;
FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
// Clean up trace and prepare it for storing frames
set_tracing(true);
clear_trace();
auth_table_len = 0;
auth_table_pos = 0;
BigBuf_free();
auth_table = (uint8_t *)BigBuf_malloc(AUTH_TABLE_LENGTH);
memset(auth_table, 0x00, AUTH_TABLE_LENGTH);
DbpString("Starting Hitag2 snoop");
LED_D_ON();
// Set up eavesdropping mode, frequency divisor which will drive the FPGA
// and analog mux selection.
FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_EDGE_DETECT | FPGA_LF_EDGE_DETECT_TOGGLE_MODE);
FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
SetAdcMuxFor(GPIO_MUXSEL_LOPKD);
// Configure output pin that is connected to the FPGA (for modulating)
AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
// Disable modulation, we are going to eavesdrop, not modulate ;)
LOW(GPIO_SSC_DOUT);
// Enable Peripheral Clock for TIMER_CLOCK1, used to capture edges of the reader frames
AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
AT91C_BASE_PIOA->PIO_BSR = GPIO_SSC_FRAME;
// Disable timer during configuration
AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
// TC1: Capture mode, default timer source = MCK/2 (TIMER_CLOCK1), TIOA is external trigger,
// external trigger rising edge, load RA on rising edge of TIOA.
AT91C_BASE_TC1->TC_CMR = AT91C_TC_CLKS_TIMER_DIV1_CLOCK | AT91C_TC_ETRGEDG_BOTH | AT91C_TC_ABETRG | AT91C_TC_LDRA_BOTH;
// Enable and reset counter
AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
// Reset the received frame, frame count and timing info
// frame_count = 0;
response = 0;
overflow = 0;
reader_frame = false;
lastbit = 1;
bSkip = true;
tag_sof = 4;
while (!BUTTON_PRESS()) {
// Watchdog hit
WDT_HIT();
// Receive frame, watch for at most T0*EOF periods
while (AT91C_BASE_TC1->TC_CV < T0*HITAG_T_EOF) {
// Check if rising edge in modulation is detected
if (AT91C_BASE_TC1->TC_SR & AT91C_TC_LDRAS) {
// Retrieve the new timing values
int ra = (AT91C_BASE_TC1->TC_RA/T0);
// Find out if we are dealing with a rising or falling edge
rising_edge = (AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_FRAME) > 0;
// Shorter periods will only happen with reader frames
if (!reader_frame && rising_edge && ra < HITAG_T_TAG_CAPTURE_ONE_HALF) {
// Switch from tag to reader capture
LED_C_OFF();
reader_frame = true;
memset(rx, 0x00, sizeof(rx));
rxlen = 0;
}
// Only handle if reader frame and rising edge, or tag frame and falling edge
if (reader_frame != rising_edge) {
overflow += ra;
continue;
}
// Add the buffered timing values of earlier captured edges which were skipped
ra += overflow;
overflow = 0;
if (reader_frame) {
LED_B_ON();
// Capture reader frame
if (ra >= HITAG_T_STOP) {
if (rxlen != 0) {
//DbpString("wierd0?");
}
// Capture the T0 periods that have passed since last communication or field drop (reset)
response = (ra - HITAG_T_LOW);
} else if (ra >= HITAG_T_1_MIN) {
// '1' bit
rx[rxlen / 8] |= 1 << (7-(rxlen%8));
rxlen++;
} else if (ra >= HITAG_T_0_MIN) {
// '0' bit
rx[rxlen / 8] |= 0 << (7-(rxlen%8));
rxlen++;
} else {
// Ignore wierd value, is to small to mean anything
}
} else {
LED_C_ON();
// Capture tag frame (manchester decoding using only falling edges)
if (ra >= HITAG_T_EOF) {
if (rxlen != 0) {
//DbpString("wierd1?");
}
// Capture the T0 periods that have passed since last communication or field drop (reset)
// We always recieve a 'one' first, which has the falling edge after a half period |-_|
response = ra - HITAG_T_TAG_HALF_PERIOD;
} else if (ra >= HITAG_T_TAG_CAPTURE_FOUR_HALF) {
// Manchester coding example |-_|_-|-_| (101)
rx[rxlen / 8] |= 0 << (7-(rxlen%8));
rxlen++;
rx[rxlen / 8] |= 1 << (7-(rxlen%8));
rxlen++;
} else if (ra >= HITAG_T_TAG_CAPTURE_THREE_HALF) {
// Manchester coding example |_-|...|_-|-_| (0...01)
rx[rxlen / 8] |= 0 << (7-(rxlen%8));
rxlen++;
// We have to skip this half period at start and add the 'one' the second time
if (!bSkip) {
rx[rxlen / 8] |= 1 << (7-(rxlen%8));
rxlen++;
}
lastbit = !lastbit;
bSkip = !bSkip;
} else if (ra >= HITAG_T_TAG_CAPTURE_TWO_HALF) {
// Manchester coding example |_-|_-| (00) or |-_|-_| (11)
if (tag_sof) {
// Ignore bits that are transmitted during SOF
tag_sof--;
} else {
// bit is same as last bit
rx[rxlen / 8] |= lastbit << (7-(rxlen%8));
rxlen++;
}
} else {
// Ignore wierd value, is to small to mean anything
}
}
}
}
// Check if frame was captured
if (rxlen > 0) {
// frame_count++;
if (!LogTraceHitag(rx, rxlen, response, 0, reader_frame)) {
DbpString("Trace full");
break;
}
// Check if we recognize a valid authentication attempt
if (nbytes(rxlen) == 8) {
// Store the authentication attempt
if (auth_table_len < (AUTH_TABLE_LENGTH-8)) {
memcpy(auth_table+auth_table_len,rx,8);
auth_table_len += 8;
}
}
// Reset the received frame and response timing info
memset(rx, 0x00, sizeof(rx));
response = 0;
reader_frame = false;
lastbit = 1;
bSkip = true;
tag_sof = 4;
overflow = 0;
LED_B_OFF();
LED_C_OFF();
} else {
// Save the timer overflow, will be 0 when frame was received
overflow += (AT91C_BASE_TC1->TC_CV/T0);
}
// Reset the frame length
rxlen = 0;
// Reset the timer to restart while-loop that receives frames
AT91C_BASE_TC1->TC_CCR = AT91C_TC_SWTRG;
}