unleashed-firmware/lib/nfc_protocols/mifare_classic.c

#include "mifare_classic.h"
#include "nfca.h"
#include "nfc_util.h"

// Algorithm from https://github.com/RfidResearchGroup/proxmark3.git

#define TAG "MfClassic"

#define MF_CLASSIC_AUTH_KEY_A_CMD (0x60U)
#define MF_CLASSIC_AUTH_KEY_B_CMD (0x61U)
#define MF_CLASSIC_READ_SECT_CMD (0x30)

static uint8_t mf_classic_get_first_block_num_of_sector(uint8_t sector) {
    furi_assert(sector < 40);
    if(sector < 32) {
        return sector * 4;
    } else {
        return 32 * 4 + (sector - 32) * 16;
    }
}

static uint8_t mf_classic_get_blocks_num_in_sector(uint8_t sector) {
    furi_assert(sector < 40);
    return sector < 32 ? 4 : 16;
}

uint8_t mf_classic_get_total_sectors_num(MfClassicReader* reader) {
    furi_assert(reader);
    if(reader->type == MfClassicType1k) {
        return MF_CLASSIC_1K_TOTAL_SECTORS_NUM;
    } else if(reader->type == MfClassicType4k) {
        return MF_CLASSIC_4K_TOTAL_SECTORS_NUM;
    } else {
        return 0;
    }
}

bool mf_classic_check_card_type(uint8_t ATQA0, uint8_t ATQA1, uint8_t SAK) {
    UNUSED(ATQA1);
    if((ATQA0 == 0x44 || ATQA0 == 0x04) && (SAK == 0x08)) {
        return true;
    } else if((ATQA0 == 0x42 || ATQA0 == 0x02) && (SAK == 0x18)) {
        return true;
    } else {
        return false;
    }
}

bool mf_classic_get_type(
    uint8_t* uid,
    uint8_t uid_len,
    uint8_t ATQA0,
    uint8_t ATQA1,
    uint8_t SAK,
    MfClassicReader* reader) {
    UNUSED(ATQA1);
    furi_assert(uid);
    furi_assert(reader);
    memset(reader, 0, sizeof(MfClassicReader));

    if((ATQA0 == 0x44 || ATQA0 == 0x04) && (SAK == 0x08)) {
        reader->type = MfClassicType1k;
    } else if((ATQA0 == 0x42 || ATQA0 == 0x02) && (SAK == 0x18)) {
        reader->type = MfClassicType4k;
    } else {
        return false;
    }

    uint8_t* cuid_start = uid;
    if(uid_len == 7) {
        cuid_start = &uid[3];
    }
    reader->cuid = (cuid_start[0] << 24) | (cuid_start[1] << 16) | (cuid_start[2] << 8) |
                   (cuid_start[3]);

    return true;
}

void mf_classic_reader_add_sector(
    MfClassicReader* reader,
    uint8_t sector,
    uint64_t key_a,
    uint64_t key_b) {
    furi_assert(reader);
    furi_assert(sector < MF_CLASSIC_SECTORS_MAX);
    furi_assert((key_a != MF_CLASSIC_NO_KEY) || (key_b != MF_CLASSIC_NO_KEY));

    if(reader->sectors_to_read < MF_CLASSIC_SECTORS_MAX - 1) {
        reader->sector_reader[reader->sectors_to_read].key_a = key_a;
        reader->sector_reader[reader->sectors_to_read].key_b = key_b;
        reader->sector_reader[reader->sectors_to_read].sector_num = sector;
        reader->sectors_to_read++;
    }
}

void mf_classic_auth_init_context(MfClassicAuthContext* auth_ctx, uint32_t cuid, uint8_t sector) {
    furi_assert(auth_ctx);
    auth_ctx->cuid = cuid;
    auth_ctx->sector = sector;
    auth_ctx->key_a = MF_CLASSIC_NO_KEY;
    auth_ctx->key_b = MF_CLASSIC_NO_KEY;
}

static bool mf_classic_auth(
    FuriHalNfcTxRxContext* tx_rx,
    uint32_t cuid,
    uint32_t block,
    uint64_t key,
    MfClassicKey key_type,
    Crypto1* crypto) {
    bool auth_success = false;
    memset(tx_rx, 0, sizeof(FuriHalNfcTxRxContext));

    do {
        if(key_type == MfClassicKeyA) {
            tx_rx->tx_data[0] = MF_CLASSIC_AUTH_KEY_A_CMD;
        } else {
            tx_rx->tx_data[0] = MF_CLASSIC_AUTH_KEY_B_CMD;
        }
        tx_rx->tx_data[1] = block;
        tx_rx->tx_rx_type = FuriHalNfcTxRxTypeRxNoCrc;
        tx_rx->tx_bits = 2 * 8;
        if(!furi_hal_nfc_tx_rx(tx_rx, 5)) break;

        uint32_t nt = (uint32_t)nfc_util_bytes2num(tx_rx->rx_data, 4);
        crypto1_init(crypto, key);
        crypto1_word(crypto, nt ^ cuid, 0);
        uint8_t nr[4] = {};
        nfc_util_num2bytes(prng_successor(DWT->CYCCNT, 32), 4, nr);
        for(uint8_t i = 0; i < 4; i++) {
            tx_rx->tx_data[i] = crypto1_byte(crypto, nr[i], 0) ^ nr[i];
            tx_rx->tx_parity[0] |=
                (((crypto1_filter(crypto->odd) ^ nfc_util_odd_parity8(nr[i])) & 0x01) << (7 - i));
        }
        nt = prng_successor(nt, 32);
        for(uint8_t i = 4; i < 8; i++) {
            nt = prng_successor(nt, 8);
            tx_rx->tx_data[i] = crypto1_byte(crypto, 0x00, 0) ^ (nt & 0xff);
            tx_rx->tx_parity[0] |=
                (((crypto1_filter(crypto->odd) ^ nfc_util_odd_parity8(nt & 0xff)) & 0x01)
                 << (7 - i));
        }
        tx_rx->tx_rx_type = FuriHalNfcTxRxTypeRaw;
        tx_rx->tx_bits = 8 * 8;
        if(!furi_hal_nfc_tx_rx(tx_rx, 5)) break;
        if(tx_rx->rx_bits == 32) {
            crypto1_word(crypto, 0, 0);
            auth_success = true;
        }
    } while(false);

    return auth_success;
}

bool mf_classic_auth_attempt(
    FuriHalNfcTxRxContext* tx_rx,
    MfClassicAuthContext* auth_ctx,
    uint64_t key) {
    furi_assert(tx_rx);
    furi_assert(auth_ctx);
    bool found_key = false;
    bool need_halt = (auth_ctx->key_a == MF_CLASSIC_NO_KEY) &&
                     (auth_ctx->key_b == MF_CLASSIC_NO_KEY);

    Crypto1 crypto;
    if(auth_ctx->key_a == MF_CLASSIC_NO_KEY) {
        // Try AUTH with key A
        if(mf_classic_auth(
               tx_rx,
               auth_ctx->cuid,
               mf_classic_get_first_block_num_of_sector(auth_ctx->sector),
               key,
               MfClassicKeyA,
               &crypto)) {
            auth_ctx->key_a = key;
            found_key = true;
        }
    }

    if(need_halt) {
        furi_hal_nfc_sleep();
        furi_hal_nfc_activate_nfca(300, &auth_ctx->cuid);
    }

    if(auth_ctx->key_b == MF_CLASSIC_NO_KEY) {
        // Try AUTH with key B
        if(mf_classic_auth(
               tx_rx,
               auth_ctx->cuid,
               mf_classic_get_first_block_num_of_sector(auth_ctx->sector),
               key,
               MfClassicKeyB,
               &crypto)) {
            auth_ctx->key_b = key;
            found_key = true;
        }
    }

    return found_key;
}

bool mf_classic_read_block(
    FuriHalNfcTxRxContext* tx_rx,
    Crypto1* crypto,
    uint8_t block_num,
    MfClassicBlock* block) {
    furi_assert(tx_rx);
    furi_assert(crypto);
    furi_assert(block);

    bool read_block_success = false;
    uint8_t plain_cmd[4] = {MF_CLASSIC_READ_SECT_CMD, block_num, 0x00, 0x00};
    nfca_append_crc16(plain_cmd, 2);
    memset(tx_rx, 0, sizeof(FuriHalNfcTxRxContext));

    for(uint8_t i = 0; i < 4; i++) {
        tx_rx->tx_data[i] = crypto1_byte(crypto, 0x00, 0) ^ plain_cmd[i];
        tx_rx->tx_parity[0] |=
            ((crypto1_filter(crypto->odd) ^ nfc_util_odd_parity8(plain_cmd[i])) & 0x01) << (7 - i);
    }
    tx_rx->tx_bits = 4 * 9;
    tx_rx->tx_rx_type = FuriHalNfcTxRxTypeRaw;

    if(furi_hal_nfc_tx_rx(tx_rx, 50)) {
        if(tx_rx->rx_bits == 8 * 18) {
            for(uint8_t i = 0; i < 18; i++) {
                block->value[i] = crypto1_byte(crypto, 0, 0) ^ tx_rx->rx_data[i];
            }
            read_block_success = true;
        }
    }
    return read_block_success;
}

bool mf_classic_read_sector(
    FuriHalNfcTxRxContext* tx_rx,
    Crypto1* crypto,
    MfClassicSectorReader* sector_reader,
    MfClassicSector* sector) {
    furi_assert(tx_rx);
    furi_assert(sector_reader);
    furi_assert(sector);

    uint32_t cuid = 0;
    uint64_t key;
    MfClassicKey key_type;
    uint8_t first_block;
    bool sector_read = false;

    furi_hal_nfc_sleep();
    do {
        // Activate card
        if(!furi_hal_nfc_activate_nfca(200, &cuid)) break;
        first_block = mf_classic_get_first_block_num_of_sector(sector_reader->sector_num);
        if(sector_reader->key_a != MF_CLASSIC_NO_KEY) {
            key = sector_reader->key_a;
            key_type = MfClassicKeyA;
        } else if(sector_reader->key_b != MF_CLASSIC_NO_KEY) {
            key = sector_reader->key_b;
            key_type = MfClassicKeyB;
        } else {
            break;
        }

        // Auth to first block in sector
        if(!mf_classic_auth(tx_rx, cuid, first_block, key, key_type, crypto)) break;
        sector->total_blocks = mf_classic_get_blocks_num_in_sector(sector_reader->sector_num);

        // Read blocks
        for(uint8_t i = 0; i < sector->total_blocks; i++) {
            mf_classic_read_block(tx_rx, crypto, first_block + i, &sector->block[i]);
        }
        // Save sector keys in last block
        if(sector_reader->key_a != MF_CLASSIC_NO_KEY) {
            nfc_util_num2bytes(
                sector_reader->key_a, 6, &sector->block[sector->total_blocks - 1].value[0]);
        }
        if(sector_reader->key_b != MF_CLASSIC_NO_KEY) {
            nfc_util_num2bytes(
                sector_reader->key_b, 6, &sector->block[sector->total_blocks - 1].value[10]);
        }

        sector_read = true;
    } while(false);

    return sector_read;
}

uint8_t mf_classic_read_card(
    FuriHalNfcTxRxContext* tx_rx,
    MfClassicReader* reader,
    MfClassicData* data) {
    furi_assert(tx_rx);
    furi_assert(reader);
    furi_assert(data);

    uint8_t sectors_read = 0;
    data->type = reader->type;
    MfClassicSector temp_sector = {};
    for(uint8_t i = 0; i < reader->sectors_to_read; i++) {
        if(mf_classic_read_sector(
               tx_rx, &reader->crypto, &reader->sector_reader[i], &temp_sector)) {
            uint8_t first_block =
                mf_classic_get_first_block_num_of_sector(reader->sector_reader[i].sector_num);
            for(uint8_t j = 0; j < temp_sector.total_blocks; j++) {
                data->block[first_block + j] = temp_sector.block[j];
            }
            sectors_read++;
        }
    }

    return sectors_read;
}

bool mf_classic_emulator(MfClassicEmulator* emulator, FuriHalNfcTxRxContext* tx_rx) {
    furi_assert(emulator);
    furi_assert(tx_rx);

    // Get first frame
    tx_rx->tx_bits = 0;
    tx_rx->tx_rx_type = FuriHalNfcTxRxTypeDefault;
    furi_hal_nfc_tx_rx(tx_rx, 300);

    // TODO support all commands
    uint8_t cmd = tx_rx->rx_data[0];
    if(!(cmd == 0x60 || cmd == 0x61)) {
        FURI_LOG_E(TAG, "Unsupported command");
        return false;
    }
    uint8_t block = tx_rx->rx_data[1];
    uint64_t key = 0;
    // TODO Now works only for 1k!!!
    uint8_t sector_trailer_block = block | 0x03;
    MfClassicSectorTrailer* sector_trailer =
        (MfClassicSectorTrailer*)emulator->data.block[sector_trailer_block].value;
    if(cmd & 0x01) {
        key = nfc_util_bytes2num(sector_trailer->key_b, 6);
    } else {
        key = nfc_util_bytes2num(sector_trailer->key_a, 6);
    }

    uint32_t nonce = prng_successor(DWT->CYCCNT, 32);
    uint8_t nt[4];
    uint8_t nt_keystream[4];
    nfc_util_num2bytes(nonce, 4, nt);
    nfc_util_num2bytes(nonce ^ emulator->cuid, 4, nt_keystream);
    crypto1_init(&emulator->crypto, key);
    crypto1_word(&emulator->crypto, emulator->cuid ^ nonce, 0);

    memcpy(tx_rx->tx_data, nt, sizeof(nt));
    tx_rx->tx_bits = sizeof(nt) * 8;
    tx_rx->tx_rx_type = FuriHalNfcTxRxTypeRxRaw;
    if(!furi_hal_nfc_tx_rx(tx_rx, 500)) {
        FURI_LOG_E(TAG, "Error in 1st data exchange");
        return false;
    }

    if(tx_rx->rx_bits != 64) {
        FURI_LOG_E(TAG, "Incorrect nr + ar");
        return false;
    }

    uint32_t nr = nfc_util_bytes2num(tx_rx->rx_data, 4);
    uint32_t ar = nfc_util_bytes2num(&tx_rx->rx_data[4], 4);
    crypto1_word(&emulator->crypto, nr, 1);
    uint32_t cardRr = ar ^ crypto1_word(&emulator->crypto, 0, 0);
    if(cardRr != prng_successor(nonce, 64)) {
        FURI_LOG_E(TAG, "Wrong AUTH! %08X != %08X", cardRr, prng_successor(nonce, 64));
        // Don't send NACK, as tag don't send it
        return false;
    }

    uint32_t ans = prng_successor(nonce, 96);
    uint8_t responce[4] = {};
    nfc_util_num2bytes(ans, 4, responce);
    tx_rx->tx_parity[0] = 0;
    for(uint8_t i = 0; i < 4; i++) {
        tx_rx->tx_data[i] = crypto1_byte(&emulator->crypto, 0, 0) ^ responce[i];
        tx_rx->tx_parity[0] |=
            (((crypto1_filter(emulator->crypto.odd) ^ nfc_util_odd_parity8(responce[i])) & 0x01)
             << (7 - (i & 0x0007)));
    }

    tx_rx->tx_bits = 8 * 4;
    tx_rx->tx_rx_type = FuriHalNfcTxRxTransparent;

    if(!furi_hal_nfc_tx_rx(tx_rx, 500)) {
        FURI_LOG_E(TAG, "Error in 2nd data exchange");
        return false;
    }

    uint8_t decrypted_cmd[4] = {};
    for(uint8_t i = 0; i < 4; i++) {
        decrypted_cmd[i] = crypto1_byte(&emulator->crypto, 0, 0) ^ tx_rx->rx_data[i];
    }

    // FURI_LOG_I(TAG, "Decrypted: %02X %02X", decrypted_cmd[0], decrypted_cmd[1]);
    if(decrypted_cmd[0] != 0x30) {
        FURI_LOG_W(TAG, "Not read command");
        return false;
    }
    uint16_t block_num = decrypted_cmd[1];

    // Send 0 block
    uint8_t block_data[18] = {};
    memcpy(block_data, emulator->data.block[block_num].value, MF_CLASSIC_BLOCK_SIZE);
    nfca_append_crc16(block_data, 16);
    tx_rx->tx_parity[0] = 0;
    tx_rx->tx_parity[1] = 0;
    tx_rx->tx_parity[2] = 0;

    for(uint8_t i = 0; i < 18; i++) {
        tx_rx->tx_data[i] = crypto1_byte(&emulator->crypto, 0, 0) ^ block_data[i];
        tx_rx->tx_parity[i >> 3] |=
            (((crypto1_filter(emulator->crypto.odd) ^ nfc_util_odd_parity8(block_data[i])) & 0x01)
             << (7 - (i & 0x0007)));
    }

    tx_rx->tx_bits = 18 * 8;
    tx_rx->tx_rx_type = FuriHalNfcTxRxTransparent;

    if(!furi_hal_nfc_tx_rx(tx_rx, 500)) {
        FURI_LOG_E(TAG, "Error in Block emulation data exchange");
        return false;
    }

    return false;
}