unleashed-firmware/lib/lfrfid/protocols/protocol_hid_generic.c

#include <furi.h>
#include <toolbox/protocols/protocol.h>
#include <lfrfid/tools/fsk_demod.h>
#include <lfrfid/tools/fsk_osc.h>
#include "lfrfid_protocols.h"
#include "lfrfid_write_fill.h"
#include <bit_lib/bit_lib.h>

#define JITTER_TIME (20)
#define MIN_TIME    (64 - JITTER_TIME)
#define MAX_TIME    (80 + JITTER_TIME)

#define HID_DATA_SIZE             11
#define HID_PREAMBLE_SIZE         1
#define HID_PROTOCOL_SIZE_UNKNOWN 0

#define HID_ENCODED_DATA_SIZE (HID_PREAMBLE_SIZE + HID_DATA_SIZE + HID_PREAMBLE_SIZE)
#define HID_ENCODED_BIT_SIZE  ((HID_PREAMBLE_SIZE + HID_DATA_SIZE) * 8)
#define HID_DECODED_DATA_SIZE (6)
#define HID_DECODED_BIT_SIZE  ((HID_ENCODED_BIT_SIZE - HID_PREAMBLE_SIZE * 8) / 2)

#define HID_PREAMBLE 0x1D

typedef struct {
    FSKDemod* fsk_demod;
} ProtocolHIDDecoder;

typedef struct {
    FSKOsc* fsk_osc;
    uint8_t encoded_index;
    uint32_t pulse;
} ProtocolHIDEncoder;

typedef struct {
    ProtocolHIDDecoder decoder;
    ProtocolHIDEncoder encoder;
    uint8_t encoded_data[HID_ENCODED_DATA_SIZE];
    uint8_t data[HID_DECODED_DATA_SIZE];
} ProtocolHID;

ProtocolHID* protocol_hid_generic_alloc(void) {
    ProtocolHID* protocol = malloc(sizeof(ProtocolHID));
    protocol->decoder.fsk_demod = fsk_demod_alloc(MIN_TIME, 6, MAX_TIME, 5);
    protocol->encoder.fsk_osc = fsk_osc_alloc(8, 10, 50);

    return protocol;
}

void protocol_hid_generic_free(ProtocolHID* protocol) {
    fsk_demod_free(protocol->decoder.fsk_demod);
    fsk_osc_free(protocol->encoder.fsk_osc);
    free(protocol);
}

uint8_t* protocol_hid_generic_get_data(ProtocolHID* protocol) {
    return protocol->data;
}

void protocol_hid_generic_decoder_start(ProtocolHID* protocol) {
    memset(protocol->encoded_data, 0, HID_ENCODED_DATA_SIZE);
}

static bool protocol_hid_generic_can_be_decoded(const uint8_t* data) {
    // check preamble
    if(data[0] != HID_PREAMBLE || data[HID_PREAMBLE_SIZE + HID_DATA_SIZE] != HID_PREAMBLE) {
        return false;
    }

    // check for manchester encoding
    for(size_t i = HID_PREAMBLE_SIZE; i < (HID_PREAMBLE_SIZE + HID_DATA_SIZE); i++) {
        for(size_t n = 0; n < 4; n++) {
            uint8_t bit_pair = (data[i] >> (n * 2)) & 0b11;
            if(bit_pair == 0b11 || bit_pair == 0b00) {
                return false;
            }
        }
    }

    return true;
}

static void protocol_hid_generic_decode(const uint8_t* from, uint8_t* to) {
    size_t bit_index = 0;
    for(size_t i = HID_PREAMBLE_SIZE; i < (HID_PREAMBLE_SIZE + HID_DATA_SIZE); i++) {
        for(size_t n = 0; n < 4; n++) {
            uint8_t bit_pair = (from[i] >> (6 - (n * 2))) & 0b11;
            if(bit_pair == 0b01) {
                bit_lib_set_bit(to, bit_index, 0);
            } else if(bit_pair == 0b10) {
                bit_lib_set_bit(to, bit_index, 1);
            }
            bit_index++;
        }
    }
}

/**
 * Decodes size from the HID Proximity header:
 * - If any of the first six bits is 1, the key is composed of the bits
 *   following the first 1
 * - Otherwise, if the first six bits are 0:
 *   - If the seventh bit is 0, the key is composed of the remaining 37 bits.
 *   - If the seventh bit is 1, the size header continues until the next 1 bit,
 *     and the key is composed of however many bits remain.
 *
 * HID Proximity keys are 26 bits at minimum. If the header implies a key size
 * under 26 bits, this function returns HID_PROTOCOL_SIZE_UNKNOWN.
 */
static uint8_t protocol_hid_generic_decode_protocol_size(ProtocolHID* protocol) {
    for(size_t bit_index = 0; bit_index < 6; bit_index++) {
        if(bit_lib_get_bit(protocol->data, bit_index)) {
            return HID_DECODED_BIT_SIZE - bit_index - 1;
        }
    }

    if(!bit_lib_get_bit(protocol->data, 6)) {
        return 37;
    }

    size_t bit_index = 7;
    uint8_t size = 36;
    while(!bit_lib_get_bit(protocol->data, bit_index) && size >= 26) {
        size--;
        bit_index++;
    }
    return size < 26 ? HID_PROTOCOL_SIZE_UNKNOWN : size;
}

bool protocol_hid_generic_decoder_feed(ProtocolHID* protocol, bool level, uint32_t duration) {
    bool value;
    uint32_t count;
    bool result = false;

    fsk_demod_feed(protocol->decoder.fsk_demod, level, duration, &value, &count);
    if(count > 0) {
        for(size_t i = 0; i < count; i++) {
            bit_lib_push_bit(protocol->encoded_data, HID_ENCODED_DATA_SIZE, value);
            if(protocol_hid_generic_can_be_decoded(protocol->encoded_data)) {
                protocol_hid_generic_decode(protocol->encoded_data, protocol->data);
                result = true;
            }
        }
    }

    return result;
}

static void protocol_hid_generic_encode(ProtocolHID* protocol) {
    protocol->encoded_data[0] = HID_PREAMBLE;

    size_t bit_index = 0;
    for(size_t i = 0; i < HID_DECODED_BIT_SIZE; i++) {
        bool bit = bit_lib_get_bit(protocol->data, i);
        if(bit) {
            bit_lib_set_bit(protocol->encoded_data, 8 + bit_index, 1);
            bit_lib_set_bit(protocol->encoded_data, 8 + bit_index + 1, 0);
        } else {
            bit_lib_set_bit(protocol->encoded_data, 8 + bit_index, 0);
            bit_lib_set_bit(protocol->encoded_data, 8 + bit_index + 1, 1);
        }
        bit_index += 2;
    }
}

bool protocol_hid_generic_encoder_start(ProtocolHID* protocol) {
    protocol->encoder.encoded_index = 0;
    protocol->encoder.pulse = 0;
    protocol_hid_generic_encode(protocol);

    return true;
}

LevelDuration protocol_hid_generic_encoder_yield(ProtocolHID* protocol) {
    bool level = 0;
    uint32_t duration = 0;

    // if pulse is zero, we need to output high, otherwise we need to output low
    if(protocol->encoder.pulse == 0) {
        // get bit
        uint8_t bit = bit_lib_get_bit(protocol->encoded_data, protocol->encoder.encoded_index);

        // get pulse from oscillator
        bool advance = fsk_osc_next(protocol->encoder.fsk_osc, bit, &duration);

        if(advance) {
            bit_lib_increment_index(protocol->encoder.encoded_index, HID_ENCODED_BIT_SIZE);
        }

        // duration diveded by 2 because we need to output high and low
        duration = duration / 2;
        protocol->encoder.pulse = duration;
        level = true;
    } else {
        // output low half and reset pulse
        duration = protocol->encoder.pulse;
        protocol->encoder.pulse = 0;
        level = false;
    }

    return level_duration_make(level, duration);
}

bool protocol_hid_generic_write_data(ProtocolHID* protocol, void* data) {
    LFRFIDWriteRequest* request = (LFRFIDWriteRequest*)data;
    bool result = false;

    // Correct protocol data by redecoding
    protocol_hid_generic_encoder_start(protocol);
    protocol_hid_generic_decode(protocol->encoded_data, protocol->data);

    protocol_hid_generic_encoder_start(protocol);

    if(request->write_type == LFRFIDWriteTypeT5577) {
        lfrfid_write_fill_t5577(
            request,
            LFRFID_T5577_MODULATION_FSK2a | LFRFID_T5577_BITRATE_RF_50 |
                (3 << LFRFID_T5577_MAXBLOCK_SHIFT),
            protocol->encoded_data);
        result = true;
    }
    return result;
}

void protocol_hid_generic_render_data(ProtocolHID* protocol, FuriString* result) {
    // the data itself is shown in hex by every caller, so only the frame length is added
    const uint8_t protocol_size = protocol_hid_generic_decode_protocol_size(protocol);

    if(protocol_size == HID_PROTOCOL_SIZE_UNKNOWN) {
        furi_string_set(result, "Generic HID Proximity");
    } else {
        furi_string_printf(result, "%hhu-bit HID Proximity", protocol_size);
    }
}

const ProtocolBase protocol_hid_generic = {
    .name = "HIDProx",
    .manufacturer = "Generic",
    .data_size = HID_DECODED_DATA_SIZE,
    .features = LFRFIDFeatureASK,
    .validate_count = 6,
    .alloc = (ProtocolAlloc)protocol_hid_generic_alloc,
    .free = (ProtocolFree)protocol_hid_generic_free,
    .get_data = (ProtocolGetData)protocol_hid_generic_get_data,
    .decoder =
        {
            .start = (ProtocolDecoderStart)protocol_hid_generic_decoder_start,
            .feed = (ProtocolDecoderFeed)protocol_hid_generic_decoder_feed,
        },
    .encoder =
        {
            .start = (ProtocolEncoderStart)protocol_hid_generic_encoder_start,
            .yield = (ProtocolEncoderYield)protocol_hid_generic_encoder_yield,
        },
    .render_data = (ProtocolRenderData)protocol_hid_generic_render_data,
    .render_brief_data = (ProtocolRenderData)protocol_hid_generic_render_data,
    .write_data = (ProtocolWriteData)protocol_hid_generic_write_data,
};