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proxmark3/armsrc/em4x50.c
tharexde ce5181bdc9 added std_read command for em4x50
2020-10-27 18:18:02 +01:00

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//-----------------------------------------------------------------------------
// Copyright (C) 2020 tharexde
//
// 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.
//-----------------------------------------------------------------------------
// Low frequency EM4x50 commands
//-----------------------------------------------------------------------------
#include "fpgaloader.h"
#include "ticks.h"
#include "dbprint.h"
#include "lfadc.h"
#include "commonutil.h"
#include "em4x50.h"
#include "BigBuf.h"
#include "appmain.h" // tear
// 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
// EM4x50 units (T0) have duration of 8 microseconds (us), which is 1/125000 per second (carrier)
// T0 = TIMER_CLOCK1 / 125000 = 192
#ifndef T0
#define T0 192
#endif
#define EM4X50_T_TAG_QUARTER_PERIOD 16
#define EM4X50_T_TAG_HALF_PERIOD 32
#define EM4X50_T_TAG_THREE_QUARTER_PERIOD 48
#define EM4X50_T_TAG_FULL_PERIOD 64
#define EM4X50_T_TAG_TPP 64
#define EM4X50_T_TAG_TWA 64
#define EM4X50_T_WAITING_FOR_SNGLLIW 100
#define EM4X50_T_WAITING_FOR_DBLLIW 1550
#define EM4X50_TAG_TOLERANCE 8
#define EM4X50_TAG_WORD 45
#define EM4X50_BIT_0 0
#define EM4X50_BIT_1 1
#define EM4X50_BIT_OTHER 2
#define EM4X50_COMMAND_LOGIN 0x01
#define EM4X50_COMMAND_RESET 0x80
#define EM4X50_COMMAND_WRITE 0x12
#define EM4X50_COMMAND_WRITE_PASSWORD 0x11
#define EM4X50_COMMAND_SELECTIVE_READ 0x0A
int gHigh = 0;
int gLow = 0;
// auxiliary functions
static void wait_timer0(uint32_t period) {
// do nothing for <period> using timer <timer>
AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
while (AT91C_BASE_TC0->TC_CV < period);
}
static void em4x50_setup_read(void) {
FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_ADC | FPGA_LF_ADC_READER_FIELD);
// 50ms for the resonant antenna to settle.
SpinDelay(50);
// Now set up the SSC to get the ADC samples that are now streaming at us.
FpgaSetupSsc(FPGA_MAJOR_MODE_LF_READER);
FpgaSendCommand(FPGA_CMD_SET_DIVISOR, LF_DIVISOR_125);
// Connect the A/D to the peak-detected low-frequency path.
SetAdcMuxFor(GPIO_MUXSEL_LOPKD);
// Steal this pin from the SSP (SPI communication channel with fpga) and
// use it to control the modulation
AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
// Disable modulation at default, which means enable the field
LOW(GPIO_SSC_DOUT);
// Enable Peripheral Clock for
// TIMER_CLOCK0, used to measure exact timing before answering
// TIMER_CLOCK1, used to capture edges of the tag frames
AT91C_BASE_PMC->PMC_PCER |= (1 << AT91C_ID_TC0) | (1 << AT91C_ID_TC1);
AT91C_BASE_PIOA->PIO_BSR = GPIO_SSC_FRAME;
// Disable timer during configuration
AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS;
AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
// TC0: Capture mode, default timer source = MCK/2 (TIMER_CLOCK1), no triggers
AT91C_BASE_TC0->TC_CMR = AT91C_TC_CLKS_TIMER_DIV1_CLOCK;
// TC1: Capture mode, default timer source = MCK/2 (TIMER_CLOCK1), no triggers
AT91C_BASE_TC1->TC_CMR = AT91C_TC_CLKS_TIMER_DIV1_CLOCK;
// Enable and reset counters
AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
// synchronized startup procedure
while (AT91C_BASE_TC0->TC_CV > 0) {}; // wait until TC1 returned to zero
// Watchdog hit
WDT_HIT();
}
static void em4x50_setup_sim(void) {
FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_EDGE_DETECT);
FpgaSendCommand(FPGA_CMD_SET_DIVISOR, LF_DIVISOR_125);
AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT | GPIO_SSC_CLK;
AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_CLK;
}
// functions for "reader" use case
static bool get_signalproperties(void) {
// calculate signal properties (mean amplitudes) from measured data:
// 32 amplitudes (maximum values) -> mean amplitude value -> gHigh -> gLow
bool signal_found = false;
int no_periods = 32, pct = 75, noise = 140;
uint8_t sample_ref = 127;
uint8_t sample_max_mean = 0;
uint8_t sample_max[no_periods];
uint32_t sample_max_sum = 0;
memcpy(sample_max, 0x00, sizeof(sample_max));
// wait until signal/noise > 1 (max. 32 periods)
for (int i = 0; i < T0 * no_periods; i++) {
if (BUTTON_PRESS()) return false;
// about 2 samples per bit period
wait_timer0(T0 * EM4X50_T_TAG_HALF_PERIOD);
if (AT91C_BASE_SSC->SSC_RHR > noise) {
signal_found = true;
break;
}
}
if (signal_found == false)
return false;
// calculate mean maximum value of 32 periods, each period has a length of
// 3 single "full periods" to eliminate the influence of a listen window
for (int i = 0; i < no_periods; i++) {
AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
while (AT91C_BASE_TC0->TC_CV < T0 * 3 * EM4X50_T_TAG_FULL_PERIOD) {
if (BUTTON_PRESS()) return false;
volatile uint8_t sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
if (sample > sample_max[i])
sample_max[i] = sample;
}
sample_max_sum += sample_max[i];
}
sample_max_mean = sample_max_sum / no_periods;
// set global envelope variables
gHigh = sample_ref + pct * (sample_max_mean - sample_ref) / 100;
gLow = sample_ref - pct * (sample_max_mean - sample_ref) / 100;
return true;
}
static bool invalid_bit(void) {
// returns true if bit is undefined by evaluating a single sample within
// a bit period (given there is no LIW, ACK or NAK)
// This function is used for identifying a listen window in functions
// "find_double_listen_window" and "check_ack"
// get sample at 3/4 of bit period
wait_timer0(T0 * EM4X50_T_TAG_THREE_QUARTER_PERIOD);
uint8_t sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
// wait until end of bit period
wait_timer0(T0 * EM4X50_T_TAG_QUARTER_PERIOD);
// bit in "undefined" state?
if (sample <= gHigh && sample >= gLow)
return true;
return false;
}
static uint32_t get_pulse_length(void) {
int32_t timeout = (T0 * 3 * EM4X50_T_TAG_FULL_PERIOD);
// iterates pulse length (low -> high -> low)
volatile uint8_t sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
while (sample > gLow && (timeout--))
sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
if (timeout == 0)
return 0;
AT91C_BASE_TC1->TC_CCR = AT91C_TC_SWTRG;
timeout = (T0 * 3 * EM4X50_T_TAG_FULL_PERIOD);
while (sample < gHigh && (timeout--))
sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
if (timeout == 0)
return 0;
timeout = (T0 * 3 * EM4X50_T_TAG_FULL_PERIOD);
while (sample > gLow && (timeout--))
sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
if (timeout == 0)
return 0;
return (uint32_t)AT91C_BASE_TC1->TC_CV;
}
static bool check_pulse_length(uint32_t pl, int length) {
// check if pulse length <pl> corresponds to given length <length>
return ((pl >= T0 * (length - EM4X50_TAG_TOLERANCE)) && (pl <= T0 * (length + EM4X50_TAG_TOLERANCE)));
}
static void em4x50_reader_send_bit(int bit) {
// send single bit according to EM4x50 application note and datasheet
// reset clock for the next bit
AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
if (bit == 0) {
// disable modulation (drop the field) for 7 cycles of carrier
// period (Opt64)
LOW(GPIO_SSC_DOUT);
while (AT91C_BASE_TC0->TC_CV < T0 * 7);
// enable modulation (activates the field) for remaining first
// half of bit period
HIGH(GPIO_SSC_DOUT);
while (AT91C_BASE_TC0->TC_CV < T0 * EM4X50_T_TAG_HALF_PERIOD);
// disable modulation for second half of bit period
LOW(GPIO_SSC_DOUT);
while (AT91C_BASE_TC0->TC_CV < T0 * EM4X50_T_TAG_FULL_PERIOD);
} else {
// bit = "1" means disable modulation for full bit period
LOW(GPIO_SSC_DOUT);
while (AT91C_BASE_TC0->TC_CV < T0 * EM4X50_T_TAG_FULL_PERIOD);
}
}
static void em4x50_reader_send_byte(uint8_t byte) {
// send byte (without parity)
for (int i = 0; i < 8; i++)
em4x50_reader_send_bit((byte >> (7 - i)) & 1);
}
static void em4x50_reader_send_byte_with_parity(uint8_t byte) {
// send byte followed by its (equal) parity bit
int parity = 0, bit = 0;
for (int i = 0; i < 8; i++) {
bit = (byte >> (7 - i)) & 1;
em4x50_reader_send_bit(bit);
parity ^= bit;
}
em4x50_reader_send_bit(parity);
}
static void em4x50_reader_send_word(const uint32_t word) {
// send 32 bit word with parity bits according to EM4x50 datasheet
// word hast be sent in msb notation
uint8_t bytes[4] = {0x0, 0x0, 0x0, 0x0};
for (int i = 0; i < 4; i++) {
bytes[i] = (word >> (24 - (8 * i))) & 0xFF;
em4x50_reader_send_byte_with_parity(bytes[i]);
}
// send column parities
em4x50_reader_send_byte(bytes[0] ^ bytes[1] ^ bytes[2] ^ bytes[3]);
// send final stop bit (always "0")
em4x50_reader_send_bit(0);
}
static bool find_single_listen_window(void) {
// find single listen window
int cnt_pulses = 0;
while (cnt_pulses < EM4X50_T_WAITING_FOR_SNGLLIW) {
// identification of listen window is done via evaluation of
// pulse lengths
if (check_pulse_length(get_pulse_length(), 3 * EM4X50_T_TAG_FULL_PERIOD)) {
if (check_pulse_length(get_pulse_length(), 2 * EM4X50_T_TAG_FULL_PERIOD)) {
// listen window found
return true;
}
}
cnt_pulses++;
}
return false;
}
static int find_double_listen_window(bool bcommand) {
// find two successive listen windows that indicate the beginning of
// data transmission
// double listen window to be detected within 1600 pulses -> worst case
// reason: first detectable double listen window after 34 words
// -> 34 words + 34 single listen windows -> about 1600 pulses
int cnt_pulses = 0;
while (cnt_pulses < EM4X50_T_WAITING_FOR_DBLLIW) {
// identification of listen window is done via evaluation of
// pulse lengths
if (check_pulse_length(get_pulse_length(), 3 * EM4X50_T_TAG_FULL_PERIOD)) {
if (check_pulse_length(get_pulse_length(), 2 * EM4X50_T_TAG_FULL_PERIOD)) {
// first listen window found
if (bcommand) {
// SpinDelay(10);
// data transmission from card has to be stopped, because
// a commamd shall be issued
// unfortunately the position in listen window (where
// command request has to be sent) has gone, so if a
// second window follows - sync on this to issue a command
// skip the next bit...
wait_timer0(T0 * EM4X50_T_TAG_FULL_PERIOD);
// ...and check if the following bit does make sense
// (if not it is the correct position within the second
// listen window)
if (invalid_bit()) {
// send RM for request mode
em4x50_reader_send_bit(0);
em4x50_reader_send_bit(0);
return true;
}
}
if (check_pulse_length(get_pulse_length(), 3 * EM4X50_T_TAG_FULL_PERIOD)) {
// return although second listen window consists of one
// more bit period but this period is necessary for
// evaluating further pulse lengths
return true;
}
}
}
cnt_pulses++;
}
return false;
}
static bool em4x50_sim_send_bit(uint8_t bit) {
uint16_t check = 0;
for (int t = 0; t < EM4X50_T_TAG_FULL_PERIOD; t++) {
// wait until SSC_CLK goes HIGH
// used as a simple detection of a reader field?
while (!(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_CLK)) {
WDT_HIT();
if (check == 1000) {
if (BUTTON_PRESS())
return false;
check = 0;
}
++check;
}
if (bit)
OPEN_COIL();
else
SHORT_COIL();
check = 0;
//wait until SSC_CLK goes LOW
while (AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_CLK) {
WDT_HIT();
if (check == 1000) {
if (BUTTON_PRESS())
return false;
check = 0;
}
++check;
}
if (t == EM4X50_T_TAG_HALF_PERIOD)
bit ^= 1;
}
return true;
}
static bool em4x50_sim_send_byte(uint8_t byte) {
// send byte
for (int i = 0; i < 8; i++)
if (!em4x50_sim_send_bit((byte >> (7 - i)) & 1))
return false;
return true;
}
static bool em4x50_sim_send_byte_with_parity(uint8_t byte) {
uint8_t parity = 0x0;
// send byte with parity (even)
for (int i = 0; i < 8; i++)
parity ^= (byte >> i) & 1;
if (!em4x50_sim_send_byte(byte))
return false;;
if (!em4x50_sim_send_bit(parity))
return false;
return true;
}
bool em4x50_sim_send_word(uint32_t word) {
uint8_t cparity = 0x00;
// word has tobe sent in msb, not lsb
word = reflect32(word);
// 4 bytes each with even row parity bit
for (int i = 0; i < 4; i++)
if (!em4x50_sim_send_byte_with_parity((word >> ((3 - i) * 8)) & 0xFF))
return false;
// column parity
for (int i = 0; i < 8; i++) {
cparity <<= 1;
for (int j = 0; j < 4; j++) {
cparity ^= (((word >> ((3 - j) * 8)) & 0xFF) >> (7 - i)) & 1;
}
}
if (!em4x50_sim_send_byte(cparity))
return false;
// stop bit
if (!em4x50_sim_send_bit(0))
return false;
return true;
}
bool em4x50_sim_send_listen_window(void) {
uint16_t check = 0;
for (int t = 0; t < 5 * EM4X50_T_TAG_FULL_PERIOD; t++) {
// wait until SSC_CLK goes HIGH
while (!(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_CLK)) {
WDT_HIT();
if (check == 1000) {
if (BUTTON_PRESS())
return false;
check = 0;
}
++check;
}
if (t >= 4 * EM4X50_T_TAG_FULL_PERIOD)
SHORT_COIL();
else if (t >= 3 * EM4X50_T_TAG_FULL_PERIOD)
OPEN_COIL();
else if (t >= EM4X50_T_TAG_FULL_PERIOD)
SHORT_COIL();
else if (t >= EM4X50_T_TAG_HALF_PERIOD)
OPEN_COIL();
else
SHORT_COIL();
check = 0;
// wait until SSC_CLK goes LOW
while (AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_CLK) {
WDT_HIT();
if (check == 1000) {
if (BUTTON_PRESS())
return false;
check = 0;
}
++check;
}
}
return true;
}
static bool find_em4x50_tag(void) {
// function is used to check wether a tag on the proxmark is an
// EM4x50 tag or not -> speed up "lf search" process
return find_single_listen_window();
}
static int request_receive_mode(void) {
// To issue a command we have to find a listen window first.
// Because identification and synchronization at the same time is not
// possible when using pulse lengths a double listen window is used.
return find_double_listen_window(true);
}
static bool check_ack(bool bliw) {
// returns true if signal structue corresponds to ACK, anything else is
// counted as NAK (-> false)
// Only relevant for pasword writing function:
// If <bliw> is true then within the single listen window right after the
// ack signal a RM request has to be sent.
AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
while (AT91C_BASE_TC0->TC_CV < T0 * 4 * EM4X50_T_TAG_FULL_PERIOD) {
if (check_pulse_length(get_pulse_length(), 2 * EM4X50_T_TAG_FULL_PERIOD)) {
// The received signal is either ACK or NAK.
if (check_pulse_length(get_pulse_length(), 2 * EM4X50_T_TAG_FULL_PERIOD)) {
// Now the signal must be ACK.
if (!bliw) {
return true;
} else {
// send RM request after ack signal
// wait for 2 bits (remaining "bit" of ACK signal + first
// "bit" of listen window)
wait_timer0(T0 * 2 * EM4X50_T_TAG_FULL_PERIOD);
// check for listen window (if first bit cannot be interpreted
// as a valid bit it must belong to a listen window)
if (invalid_bit()) {
// send RM for request mode
em4x50_reader_send_bit(0);
em4x50_reader_send_bit(0);
return true;
}
}
} else {
// It's NAK -> stop searching
break;
}
}
}
return false;
}
static bool extract_parities(uint64_t word, uint32_t *data) {
// extract and check parities
// return result of parity check and extracted plain data
uint8_t row_parities = 0x0, col_parities = 0x0;
uint8_t row_parities_calculated = 0x0, col_parities_calculated = 0x0;
*data = 0x0;
// extract plain data (32 bits) from raw word (45 bits)
for (int i = 0; i < 4; i++) {
*data <<= 8;
*data |= (word >> ((4 - i) * 9 + 1)) & 0xFF;
}
// extract row parities (4 bits + stop bit) from raw word (45 bits)
for (int i = 0; i < 5; i++) {
row_parities <<= 1;
row_parities |= (word >> ((4 - i) * 9)) & 0x1;
}
// extract col_parities (8 bits, no stop bit) from raw word (45 bits)
col_parities = (word >> 1) & 0xFF;
// check extracted parities against extracted data
// calculate row parities from data
for (int i = 0; i < 4; i++) {
row_parities_calculated <<= 1;
for (int j = 0; j < 8; j++) {
row_parities_calculated ^= (*data >> ((3 - i) * 8 + (7 - j))) & 0x1;
}
}
// add stop bit (always zero)
row_parities_calculated <<= 1;
// calculate column parities from data
for (int i = 0; i < 8; i++) {
col_parities_calculated <<= 1;
for (int j = 0; j < 4; j++) {
col_parities_calculated ^= (*data >> ((3 - j) * 8 + (7 - i))) & 0x1;
}
}
if ((row_parities == row_parities_calculated) && (col_parities == col_parities_calculated))
return true;
return false;
}
static int get_word_from_bitstream(uint32_t *data) {
// decodes one word by evaluating pulse lengths and previous bit;
// word must have 45 bits in total:
// 32 data bits + 4 row parity bits + 8 column parity bits + 1 stop bit
bool bitchange = false;
int cnt = 0;
uint32_t pl = 0;
uint64_t word = 0x0;
*data = 0x0;
// initial bit value depends on last pulse length of listen window
pl = get_pulse_length();
if (check_pulse_length(pl, 3 * EM4X50_T_TAG_HALF_PERIOD)) {
// pulse length = 1.5
word = 0x1;
} else if (check_pulse_length(pl, 2 * EM4X50_T_TAG_FULL_PERIOD)) {
// pulse length = 2
bitchange = true;
} else {
// pulse length = 2.5
word = 0x1;
cnt++;
}
// identify remaining bits based on pulse lengths
// between two listen windows only pulse lengths of 1, 1.5 and 2 are possible
while (true) {
cnt++;
word <<= 1;
pl = get_pulse_length();
if (check_pulse_length(pl, EM4X50_T_TAG_FULL_PERIOD)) {
// pulse length = 1 -> keep former bit value
word |= (word >> 1) & 0x1;
} else if (check_pulse_length(pl, 3 * EM4X50_T_TAG_HALF_PERIOD)) {
// pulse length = 1.5 -> decision on bit change
if (bitchange) {
// if number of pulse lengths with 1.5 periods is even -> add bit
word |= (word >> 1) & 0x1;
word <<= 1;
// pulse length of 1.5 changes bit value
word |= ((word >> 1) & 0x1) ^ 0x1;
cnt++;
// next time add only one bit
bitchange = false;
} else {
word |= ((word >> 1) & 0x1) ^ 0x1;
// next time two bits have to be added
bitchange = true;
}
} else if (check_pulse_length(pl, 2 * EM4X50_T_TAG_FULL_PERIOD)) {
// pulse length of 2 means: adding 2 bits "01"
cnt++;
word <<= 1;
word |= 0x1;
} else if (check_pulse_length(pl, 3 * EM4X50_T_TAG_FULL_PERIOD)) {
// pulse length of 3 indicates listen window -> clear last
// bit (= 0) and return (without parities)
word >>= 2;
return (extract_parities(word, data)) ? --cnt : 0;
}
}
}
//==============================================================================
// login function
//==============================================================================
static bool login(uint32_t password) {
// simple login to EM4x50,
// used in operations that require authentication
if (request_receive_mode()) {
// send login command
em4x50_reader_send_byte_with_parity(EM4X50_COMMAND_LOGIN);
// send password
em4x50_reader_send_word(password);
// check if ACK is returned
if (check_ack(false))
return true;
} else {
if (DBGLEVEL >= DBG_DEBUG)
Dbprintf("error in command request");
}
return false;
}
//==============================================================================
// reset function
//==============================================================================
static bool reset(void) {
// resets EM4x50 tag (used by write function)
if (request_receive_mode()) {
// send login command
em4x50_reader_send_byte_with_parity(EM4X50_COMMAND_RESET);
if (check_ack(false))
return true;
} else {
if (DBGLEVEL >= DBG_DEBUG)
Dbprintf("error in command request");
}
return false;
}
//==============================================================================
// read functions
//==============================================================================
static bool standard_read(int *now, uint32_t *words) {
// reads data that tag transmits when exposed to reader field
// (standard read mode); number of read words is saved in <now>
int fwr = *now;
// start with the identification of two successive listening windows
if (find_double_listen_window(false)) {
// read and save words until following double listen window is detected
while (get_word_from_bitstream(&words[*now]) == EM4X50_TAG_WORD)
(*now)++;
// number of detected words
*now -= fwr;
return true;
} else {
if (DBGLEVEL >= DBG_DEBUG)
Dbprintf("didn't find a listen window");
}
return false;
}
static bool selective_read(uint32_t addresses, uint32_t *words) {
// reads from "first word read" (fwr) to "last word read" (lwr)
// result is verified by "standard read mode"
uint8_t fwr = addresses & 0xFF; // first word read (first byte)
uint8_t lwr = (addresses >> 8) & 0xFF; // last word read (second byte)
int now = fwr; // number of words
if (request_receive_mode()) {
// send selective read command
em4x50_reader_send_byte_with_parity(EM4X50_COMMAND_SELECTIVE_READ);
// send address data
em4x50_reader_send_word(addresses);
// look for ACK sequence
if (check_ack(false))
// save and verify via standard read mode (compare number of words)
if (standard_read(&now, words))
if (now == (lwr - fwr + 1))
return true;
} else {
if (DBGLEVEL >= DBG_DEBUG)
Dbprintf("error in command request");
}
return false;
}
void em4x50_info(em4x50_data_t *etd) {
// collects as much information as possible via selective read mode
bool bsuccess = false, blogin = false;
uint8_t status = 0;
uint32_t addresses = 0x00002100; // read from fwr = 0 to lwr = 33 (0x21)
uint32_t words[EM4X50_NO_WORDS] = {0x0};
em4x50_setup_read();
// set gHigh and gLow
if (get_signalproperties() && find_em4x50_tag()) {
// login with given password
if (etd->pwd_given)
blogin = login(etd->password1);
bsuccess = selective_read(addresses, words);
}
status = (bsuccess << 1) + blogin;
lf_finalize();
reply_ng(CMD_LF_EM4X50_INFO, status, (uint8_t *)words, 136);
}
void em4x50_read(em4x50_data_t *etd) {
// reads in two different ways:
// - using "selective read mode" -> bidirectional communication
// - using "standard read mode" -> unidirectional communication (read
// data that tag transmits "voluntarily")
bool bsuccess = false, blogin = false;
int now = 0;
uint8_t status = 0;
uint32_t words[EM4X50_NO_WORDS] = {0x0};
em4x50_setup_read();
// set gHigh and gLow
if (get_signalproperties() && find_em4x50_tag()) {
if (etd->addr_given) {
// selective read mode
// try to login with given password
if (etd->pwd_given)
blogin = login(etd->password1);
// only one word has to be read -> first word read = last word read
bsuccess = selective_read(etd->addresses, words);
} else {
// standard read mode
bsuccess = standard_read(&now, words);
}
}
status = (now << 2) + (bsuccess << 1) + blogin;
LOW(GPIO_SSC_DOUT);
lf_finalize();
reply_ng(CMD_LF_EM4X50_READ, status, (uint8_t *)words, 136);
}
//==============================================================================
// write functions
//==============================================================================
static int write(uint32_t word, uint32_t addresses) {
// writes <word> to specified <address>
if (request_receive_mode()) {
// send write command
em4x50_reader_send_byte_with_parity(EM4X50_COMMAND_WRITE);
// send address data
em4x50_reader_send_byte_with_parity(addresses & 0xFF);
// send data
em4x50_reader_send_word(word);
if (tearoff_hook() == PM3_ETEAROFF) { // tearoff occurred
reply_ng(CMD_LF_EM4X50_WRITE, PM3_ETEAROFF, NULL, 0);
return PM3_ETEAROFF;
} else {
// wait for T0 * EM4X50_T_TAG_TWA (write access time)
wait_timer0(T0 * EM4X50_T_TAG_TWA);
// look for ACK sequence
if (check_ack(false)) {
// now EM4x50 needs T0 * EM4X50_T_TAG_TWEE (EEPROM write time)
// for saving data and should return with ACK
if (check_ack(false))
return PM3_SUCCESS;
}
}
} else {
if (DBGLEVEL >= DBG_DEBUG)
Dbprintf("error in command request");
}
return false;
}
static int write_password(uint32_t password, uint32_t new_password) {
// changes password from <password> to <new_password>
if (request_receive_mode()) {
// send write password command
em4x50_reader_send_byte_with_parity(EM4X50_COMMAND_WRITE_PASSWORD);
// send address data
em4x50_reader_send_word(password);
if (tearoff_hook() == PM3_ETEAROFF) { // tearoff occurred
reply_ng(CMD_LF_EM4X50_WRITE, PM3_ETEAROFF, NULL, 0);
return PM3_ETEAROFF;
} else {
// wait for T0 * EM4x50_T_TAG_TPP (processing pause time)
wait_timer0(T0 * EM4X50_T_TAG_TPP);
// look for ACK sequence and send rm request
// during following listen window
if (check_ack(true)) {
// send new password
em4x50_reader_send_word(new_password);
// wait for T0 * EM4X50_T_TAG_TWA (write access time)
wait_timer0(T0 * EM4X50_T_TAG_TWA);
if (check_ack(false))
if (check_ack(false))
return PM3_SUCCESS;
}
}
} else {
if (DBGLEVEL >= DBG_DEBUG)
Dbprintf("error in command request");
}
return PM3_ESOFT;
}
void em4x50_write(em4x50_data_t *etd) {
// write operation process for EM4x50 tag,
// single word is written to given address, verified by selective read operation
bool bsuccess = false, blogin = false;
uint8_t status = 0;
uint32_t words[EM4X50_NO_WORDS] = {0x0};
em4x50_setup_read();
// set gHigh and gLow
if (get_signalproperties() && find_em4x50_tag()) {
// if password is given try to login first
if (etd->pwd_given)
blogin = login(etd->password1);
// write word to given address
int res = write(etd->word, etd->addresses);
if (res == PM3_ETEAROFF) {
lf_finalize();
return;
}
if (res == PM3_SUCCESS) {
// to verify result reset EM4x50
if (reset()) {
// if password is given login
if (etd->pwd_given)
blogin &= login(etd->password1);
// call a selective read
if (selective_read(etd->addresses, words)) {
// compare with given word
bsuccess = (words[etd->addresses & 0xFF] == reflect32(etd->word));
}
}
}
}
status = (bsuccess << 1) + blogin;
lf_finalize();
reply_ng(CMD_LF_EM4X50_WRITE, status, (uint8_t *)words, 136);
}
void em4x50_write_password(em4x50_data_t *etd) {
// simple change of password
bool bsuccess = false;
em4x50_setup_read();
// set gHigh and gLow
if (get_signalproperties() && find_em4x50_tag()) {
// login and change password
if (login(etd->password1)) {
int res = write_password(etd->password1, etd->password2);
if (res == PM3_ETEAROFF) {
lf_finalize();
return;
}
bsuccess = (res == PM3_SUCCESS);
}
}
lf_finalize();
reply_ng(CMD_LF_EM4X50_WRITE_PASSWORD, bsuccess, 0, 0);
}
void em4x50_wipe(uint32_t *password) {
// set all data of EM4x50 tag to 0x0 including password
bool bsuccess = false;
uint32_t addresses = 0x00001E01; // from fwr = 1 to lwr = 31 (0x1E)
uint32_t words[EM4X50_NO_WORDS] = {0x0};
uint32_t zero = 0x0;
em4x50_setup_read();
// set gHigh and gLow
if (get_signalproperties() && find_em4x50_tag()) {
// login first
if (login(*password)) {
// write 0x0 to each address but ignore addresses
// 0 -> password, 32 -> serial, 33 -> uid
for (int i = 1; i <= 33; i++)
write(zero, i);
// to verify result -> reset EM4x50
if (reset()) {
// login not necessary because protected word has been set to 0
// -> no read protected words
// -> selective read can be called immediately
if (selective_read(addresses, words)) {
// check if everything is zero
bsuccess = true;
for (int i = 1; i <= 33; i++)
bsuccess &= (words[i] == 0);
}
if (bsuccess) {
// so far everything is fine
// last task: reset password
if (login(*password)) {
int res = write_password(*password, zero);
if (res == PM3_ETEAROFF) {
lf_finalize();
return;
}
bsuccess = (res == PM3_SUCCESS);
}
// verify by login with new password
if (bsuccess)
bsuccess = login(zero);
}
}
}
}
lf_finalize();
reply_ng(CMD_LF_EM4X50_WIPE, bsuccess, 0, 0);
}
void em4x50_reset(void) {
// reset EM4x50
uint8_t status = 0;
em4x50_setup_read();
// set gHigh and gLow
if (get_signalproperties() && find_em4x50_tag())
status = reset();
lf_finalize();
reply_ng(CMD_LF_EM4X50_RESET, status, 0, 0);
}
void em4x50_login(uint32_t *password) {
// login into EM4x50
uint8_t status = false;
em4x50_setup_read();
// set gHigh and gLow
if (get_signalproperties() && find_em4x50_tag())
status = login(*password);
lf_finalize();
reply_ng(CMD_LF_EM4X50_LOGIN, status, 0, 0);
}
static bool brute(uint32_t start, uint32_t stop, uint32_t *pwd) {
// searching for password in given range
bool pwd_found = false;
int cnt = 0;
for (*pwd = start; *pwd <= stop; (*pwd)++) {
if (login(*pwd)) {
pwd_found = true;
break;
}
// print password every 500 iterations
if ((++cnt % 500) == 0) {
// print header
if (cnt == 500) {
Dbprintf("|---------+------------+------------|");
Dbprintf("| no. | pwd (msb) | pwd (lsb) |");
Dbprintf("|---------+------------+------------|");
}
// print data
Dbprintf("|%8i | 0x%08x | 0x%08x |", cnt, reflect32(*pwd), *pwd);
}
if (BUTTON_PRESS())
break;
}
// print footer
if (cnt >= 500)
Dbprintf("|---------+------------+------------|");
return pwd_found;
}
void em4x50_brute(em4x50_data_t *etd) {
// envoke password search
bool bsuccess = false;
uint32_t pwd = 0x0;
em4x50_setup_read();
if (get_signalproperties() && find_em4x50_tag())
bsuccess = brute(etd->password1, etd->password2, &pwd);
lf_finalize();
reply_ng(CMD_LF_EM4X50_BRUTE, bsuccess, (uint8_t *)(&pwd), 32);
}
void em4x50_watch() {
// read continuously and display standard reads of tag
int now = 0;
uint32_t words[EM4X50_NO_WORDS] = {0x0};
em4x50_setup_read();
while (BUTTON_PRESS() == false) {
WDT_HIT();
memset(words, 0, sizeof(words));
now = 0;
if (get_signalproperties() && find_em4x50_tag()) {
standard_read(&now, words);
if (now > 0) {
Dbprintf("");
for (int i = 0; i < now; i++) {
Dbprintf("EM4x50 TAG ID: "
_GREEN_("%08x") " (msb) - " _GREEN_("%08x") " (lsb)",
words[i], reflect32(words[i]));
}
}
}
}
LOW(GPIO_SSC_DOUT);
lf_finalize();
reply_ng(CMD_LF_EM4X50_WATCH, 1, 0, 0);
}
//==============================================================================
// standalone mode functions
//==============================================================================
int em4x50_standalone_brute(uint32_t start, uint32_t stop, uint32_t *pwd) {
// envoke password search in standalone mode
int status = false;
em4x50_setup_read();
if (get_signalproperties() && find_em4x50_tag())
status = brute(start, stop, pwd);
else
status = PM3_ETIMEOUT;
lf_finalize();
return status;
}
int em4x50_standalone_read(uint32_t *words) {
int now = 0;
em4x50_setup_read();
if (get_signalproperties() && find_em4x50_tag())
if (find_double_listen_window(false))
while (get_word_from_bitstream(&words[now]) == EM4X50_TAG_WORD)
now++;
return now;
}
void em4x50_restore(em4x50_data_t *etd) {
// restore em4x50 dump file to tag
bool bsuccess = false, blogin = false;
int res = 0;
int start_word = 0;
uint8_t status = 0;
uint32_t addresses = 0x00001F01; // from fwr = 1 to lwr = 31 (0x1F)
uint32_t words_client[EM4X50_NO_WORDS] = {0x0};
uint32_t words_read[EM4X50_NO_WORDS] = {0x0};
em4x50_setup_read();
// read data
for (int i = 0; i < EM4X50_NO_WORDS; i++) {
for (int j = 0; j < 4; j++)
words_client[i] |= (etd->data[4 * i + j]) << ((3 - j) * 8);
// lsb is needed (dump is msb)
words_client[i] = reflect32(words_client[i]);
}
// set gHigh and gLow
if (get_signalproperties() && find_em4x50_tag()) {
// login first if password is available
if (etd->pwd_given)
blogin = login(etd->password1);
// write data to each address but ignore addresses
// 0 -> password, 32 -> serial, 33 -> uid
// without login words 1 and 2 cannot be written
start_word = (blogin) ? 1 : 3;
for (int i = start_word; i < EM4X50_NO_WORDS - 2; i++) {
res = write(words_client[i], i);
if (res == PM3_ETEAROFF) {
lf_finalize();
return;
}
}
// to verify result -> reset EM4x50
if (reset()) {
// login not necessary because protected word has been set to 0
// -> no read protected words
// -> selective read can be called immediately
if (selective_read(addresses, words_read)) {
// check if everything is zero
bsuccess = true;
for (int i = start_word; i < EM4X50_NO_WORDS - 2; i++)
bsuccess &= (reflect32(words_read[i]) == words_client[i]);
}
}
}
status = (bsuccess << 1) + blogin;
lf_finalize();
reply_ng(CMD_LF_EM4X50_RESTORE, status, 0, 0);
}
void em4x50_sim(em4x50_data_t *etd) {
// simulate either word (e.g. UID) or complete tag via dump file upload
uint32_t words[EM4X50_NO_WORDS] = {0x0};
em4x50_setup_sim();
// read data
for (int i = 0; i < EM4X50_NO_WORDS; i++) {
for (int j = 0; j < 4; j++)
words[i] |= (etd->data[4 * i + j]) << ((3 - j) * 8);
// lsb is needed (dump is msb)
words[i] = reflect32(words[i]);
}
// extract control data
int fwr = words[CONFIG_BLOCK] & 0xFF; // first word read
int lwr = (words[CONFIG_BLOCK] >> 8) & 0xFF; // last word read
// extract protection data
int fwrp = words[EM4X50_PROTECTION] & 0xFF; // first word read protected
int lwrp = (words[EM4X50_PROTECTION] >> 8) & 0xFF; // last word read protected
while (!BUTTON_PRESS()) {
WDT_HIT();
em4x50_sim_send_listen_window();
for (int i = fwr; i <= lwr; i++) {
em4x50_sim_send_listen_window();
if ((i >= fwrp) && (i <= lwrp))
em4x50_sim_send_word(0x00);
else
em4x50_sim_send_word(words[i]);
}
}
lf_finalize();
reply_ng(CMD_LF_EM4X50_SIM, 1, 0, 0);
}
void em4x50_std_read(void) {
// reads data that tag transmits "voluntarily" -> standard read mode
int now = 0;
uint32_t words[EM4X50_NO_WORDS] = {0x0};
em4x50_setup_read();
// set gHigh and gLow
if (get_signalproperties() && find_em4x50_tag())
standard_read(&now, words);
LOW(GPIO_SSC_DOUT);
lf_finalize();
reply_ng(CMD_LF_EM4X50_STD_READ, now, (uint8_t *)words, 4 * now);
}
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