//-----------------------------------------------------------------------------
// Frederik Möllers - August 2012
//
// 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.
//-----------------------------------------------------------------------------
// Routines to support the German electronic "Personalausweis" (ID card)
// Note that the functions which do not implement USB commands do NOT initialize
// the card (with iso14443a_select_card etc.). If You want to use these
// functions, You need to do the setup before calling them!
//-----------------------------------------------------------------------------
#include "epa.h"

#include "cmd.h"
#include "fpgaloader.h"
#include "iso14443a.h"
#include "iso14443b.h"
#include "string.h"
#include "util.h"
#include "dbprint.h"
#include "commonutil.h"
#include "ticks.h"

// Protocol and Parameter Selection Request for ISO 14443 type A cards
// use regular (1x) speed in both directions
// CRC is already included
static const uint8_t pps[] = {0xD0, 0x11, 0x00, 0x52, 0xA6};

// APDUs for communication with German Identification Card

// General Authenticate (request encrypted nonce) WITHOUT the Le at the end
static const uint8_t apdu_general_authenticate_pace_get_nonce[] = {
    0x10, // CLA
    0x86, // INS
    0x00, // P1
    0x00, // P2
    0x02, // Lc
    0x7C, // Type: Dynamic Authentication Data
    0x00, // Length: 0 bytes
};

// MSE: Set AT (only CLA, INS, P1 and P2)
static const uint8_t apdu_mse_set_at_start[] = {
    0x00, // CLA
    0x22, // INS
    0xC1, // P1
    0xA4, // P2
};

// SELECT BINARY with the ID for EF.CardAccess
static const uint8_t apdu_select_binary_cardaccess[] = {
    0x00, // CLA
    0xA4, // INS
    0x02, // P1
    0x0C, // P2
    0x02, // Lc
    0x01, // ID
    0x1C  // ID
};

// READ BINARY
static const uint8_t apdu_read_binary[] = {
    0x00, // CLA
    0xB0, // INS
    0x00, // P1
    0x00, // P2
    0x38  // Le
};


// the leading bytes of a PACE OID
static const uint8_t oid_pace_start[] = {
    0x04, // itu-t, identified-organization
    0x00, // etsi
    0x7F, // reserved
    0x00, // etsi-identified-organization
    0x07, // bsi-de
    0x02, // protocols
    0x02, // smartcard
    0x04 // id-PACE
};

// APDUs for replaying:
// MSE: Set AT (initiate PACE)
static uint8_t apdu_replay_mse_set_at_pace[41];
// General Authenticate (Get Nonce)
static uint8_t apdu_replay_general_authenticate_pace_get_nonce[8];
// General Authenticate (Map Nonce)
static uint8_t apdu_replay_general_authenticate_pace_map_nonce[75];
// General Authenticate (Mutual Authenticate)
static uint8_t apdu_replay_general_authenticate_pace_mutual_authenticate[75];
// General Authenticate (Perform Key Agreement)
static uint8_t apdu_replay_general_authenticate_pace_perform_key_agreement[18];
// pointers to the APDUs (for iterations)
static struct {
    uint8_t len;
    uint8_t *data;
} const apdus_replay[] = {
    {sizeof(apdu_replay_mse_set_at_pace), apdu_replay_mse_set_at_pace},
    {sizeof(apdu_replay_general_authenticate_pace_get_nonce), apdu_replay_general_authenticate_pace_get_nonce},
    {sizeof(apdu_replay_general_authenticate_pace_map_nonce), apdu_replay_general_authenticate_pace_map_nonce},
    {sizeof(apdu_replay_general_authenticate_pace_mutual_authenticate), apdu_replay_general_authenticate_pace_mutual_authenticate},
    {sizeof(apdu_replay_general_authenticate_pace_perform_key_agreement), apdu_replay_general_authenticate_pace_perform_key_agreement}
};

// lengths of the replay APDUs
static uint8_t apdu_lengths_replay[5];

// type of card (ISO 14443 A or B)
static char iso_type = 0;

//-----------------------------------------------------------------------------
// Wrapper for sending APDUs to type A and B cards
//-----------------------------------------------------------------------------
int EPA_APDU(uint8_t *apdu, size_t length, uint8_t *response) {
    switch (iso_type) {
        case 'a':
            return iso14_apdu(apdu, (uint16_t) length, false, response, NULL);
            break;
        case 'b':
            return iso14443b_apdu(apdu, length, response);
            break;
        default:
            return 0;
            break;
    }
}

//-----------------------------------------------------------------------------
// Closes the communication channel and turns off the field
//-----------------------------------------------------------------------------
void EPA_Finish() {
    FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
    LEDsoff();
    iso_type = 0;
}

//-----------------------------------------------------------------------------
// Parses DER encoded data, e.g. from EF.CardAccess and fills out the given
// structs. If a pointer is 0, it is ignored.
// The function returns 0 on success and if an error occurred, it returns the
// offset where it occurred.
//
// TODO: This function can access memory outside of the given data if the DER
//       encoding is broken
// TODO: Support skipping elements with a length > 0x7F
// TODO: Support OIDs with a length > 7F
// TODO: Support elements with long tags (tag is longer than 1 byte)
// TODO: Support proprietary PACE domain parameters
//-----------------------------------------------------------------------------
size_t EPA_Parse_CardAccess(uint8_t *data,
                            size_t length,
                            pace_version_info_t *pace_info) {
    size_t index = 0;

    while (index <= length - 2) {
        // determine type of element
        // SET or SEQUENCE
        if (data[index] == 0x31 || data[index] == 0x30) {
            // enter the set (skip tag + length)
            index += 2;
            // check for extended length
            if ((data[index - 1] & 0x80) != 0) {
                index += (data[index - 1] & 0x7F);
            }
        }
        // OID
        else if (data[index] == 0x06) {
            // is this a PACE OID?
            if (data[index + 1] == 0x0A // length matches
                    && memcmp(data + index + 2,
                              oid_pace_start,
                              sizeof(oid_pace_start)) == 0 // content matches
                    && pace_info != NULL) {
                // first, clear the pace_info struct
                memset(pace_info, 0, sizeof(pace_version_info_t));
                memcpy(pace_info->oid, data + index + 2, sizeof(pace_info->oid));
                // a PACE OID is followed by the version
                index += data[index + 1] + 2;
                if (data[index] == 02 && data[index + 1] == 01) {
                    pace_info->version = data[index + 2];
                    index += 3;
                } else {
                    return index;
                }
                // after that there might(!) be the parameter ID
                if (data[index] == 02 && data[index + 1] == 01) {
                    pace_info->parameter_id = data[index + 2];
                    index += 3;
                }
            } else {
                // skip this OID
                index += 2 + data[index + 1];
            }
        }
        // if the length is 0, something is wrong
        // TODO: This needs to be extended to support long tags
        else if (data[index + 1] == 0) {
            return index;
        } else {
            // skip this part
            // TODO: This needs to be extended to support long tags
            // TODO: This needs to be extended to support unknown elements with
            //       a size > 0x7F
            index += 2 + data[index + 1];
        }
    }

    // TODO: We should check whether we reached the end in error, but for that
    //       we need a better parser (e.g. with states like IN_SET or IN_PACE_INFO)
    return 0;
}

//-----------------------------------------------------------------------------
// Read the file EF.CardAccess and save it into a buffer (at most max_length bytes)
// Returns -1 on failure or the length of the data on success
// TODO: for the moment this sends only 1 APDU regardless of the requested length
//-----------------------------------------------------------------------------
int EPA_Read_CardAccess(uint8_t *buffer, size_t max_length) {
    // the response APDU of the card
    // since the card doesn't always care for the expected length we send it,
    // we reserve 262 bytes here just to be safe (256-byte APDU + SW + ISO frame)
    uint8_t response_apdu[262];
    int rapdu_length = 0;

    // select the file EF.CardAccess
    rapdu_length = EPA_APDU((uint8_t *)apdu_select_binary_cardaccess,
                            sizeof(apdu_select_binary_cardaccess),
                            response_apdu);
    if (rapdu_length < 6
            || response_apdu[rapdu_length - 4] != 0x90
            || response_apdu[rapdu_length - 3] != 0x00) {
        DbpString("Failed to select EF.CardAccess!");
        return -1;
    }

    // read the file
    rapdu_length = EPA_APDU((uint8_t *)apdu_read_binary,
                            sizeof(apdu_read_binary),
                            response_apdu);
    if (rapdu_length <= 6
            || response_apdu[rapdu_length - 4] != 0x90
            || response_apdu[rapdu_length - 3] != 0x00) {
        Dbprintf("Failed to read EF.CardAccess!");
        return -1;
    }

    // copy the content into the buffer
    // length of data available: apdu_length - 4 (ISO frame) - 2 (SW)
    size_t to_copy = rapdu_length - 6;
    to_copy = to_copy < max_length ? to_copy : max_length;
    memcpy(buffer, response_apdu + 2, to_copy);
    return to_copy;
}

//-----------------------------------------------------------------------------
// Abort helper function for EPA_PACE_Collect_Nonce
// sets relevant data in ack, sends the response
//-----------------------------------------------------------------------------
static void EPA_PACE_Collect_Nonce_Abort(uint8_t step, int func_return) {
    // power down the field
    EPA_Finish();

    // send the USB packet
    reply_old(CMD_ACK, step, func_return, 0, 0, 0);
}

//-----------------------------------------------------------------------------
// Acquire one encrypted PACE nonce
//-----------------------------------------------------------------------------
void EPA_PACE_Collect_Nonce(PacketCommandNG *c) {
    /*
     * ack layout:
     *   arg:
     *       1. element
     *           step where the error occurred or 0 if no error occurred
     *       2. element
     *           return code of the last executed function
     *   d:
     *       Encrypted nonce
     */

    // return value of a function
    int func_return = 0;

    // set up communication
    func_return = EPA_Setup();
    if (func_return != 0) {
        EPA_PACE_Collect_Nonce_Abort(1, func_return);
        return;
    }

    // read the CardAccess file
    // this array will hold the CardAccess file
    uint8_t card_access[256] = {0};
    int card_access_length = EPA_Read_CardAccess(card_access, 256);
    // the response has to be at least this big to hold the OID
    if (card_access_length < 18) {
        EPA_PACE_Collect_Nonce_Abort(2, card_access_length);
        return;
    }

    // this will hold the PACE info of the card
    pace_version_info_t pace_version_info;
    // search for the PACE OID
    func_return = EPA_Parse_CardAccess(card_access,
                                       card_access_length,
                                       &pace_version_info);
    if (func_return != 0 || pace_version_info.version == 0) {
        EPA_PACE_Collect_Nonce_Abort(3, func_return);
        return;
    }

    // initiate the PACE protocol
    // use the CAN for the password since that doesn't change
    func_return = EPA_PACE_MSE_Set_AT(pace_version_info, 2);
    // check if the command succeeded
    if (func_return != 0) {
        EPA_PACE_Collect_Nonce_Abort(4, func_return);
        return;
    }

    // now get the nonce
    uint8_t nonce[256] = {0};
    uint8_t requested_size = (uint8_t)c->oldarg[0];
    func_return = EPA_PACE_Get_Nonce(requested_size, nonce);
    // check if the command succeeded
    if (func_return < 0) {
        EPA_PACE_Collect_Nonce_Abort(5, func_return);
        return;
    }

    // all done, return
    EPA_Finish();

    // save received information
    reply_old(CMD_ACK, 0, func_return, 0, nonce, func_return);
}

//-----------------------------------------------------------------------------
// Performs the "Get Nonce" step of the PACE protocol and saves the returned
// nonce. The caller is responsible for allocating enough memory to store the
// nonce. Note that the returned size might be less or than or greater than the
// requested size!
// Returns the actual size of the nonce on success or a less-than-zero error
// code on failure.
//-----------------------------------------------------------------------------
int EPA_PACE_Get_Nonce(uint8_t requested_length, uint8_t *nonce) {
    // build the APDU
    uint8_t apdu[sizeof(apdu_general_authenticate_pace_get_nonce) + 1];
    // copy the constant part
    memcpy(apdu,
           apdu_general_authenticate_pace_get_nonce,
           sizeof(apdu_general_authenticate_pace_get_nonce));
    // append Le (requested length + 2 due to tag/length taking 2 bytes) in RAPDU
    apdu[sizeof(apdu_general_authenticate_pace_get_nonce)] = requested_length + 4;

    // send it
    uint8_t response_apdu[262];
    int send_return = EPA_APDU(apdu,
                               sizeof(apdu),
                               response_apdu);
    // check if the command succeeded
    if (send_return < 6
            || response_apdu[send_return - 4] != 0x90
            || response_apdu[send_return - 3] != 0x00) {
        return -1;
    }

    // if there is no nonce in the RAPDU, return here
    if (send_return < 10) {
        // no error
        return 0;
    }
    // get the actual length of the nonce
    uint8_t nonce_length = response_apdu[5];
    if (nonce_length > send_return - 10) {
        nonce_length = send_return - 10;
    }
    // copy the nonce
    memcpy(nonce, response_apdu + 6, nonce_length);

    return nonce_length;
}

//-----------------------------------------------------------------------------
// Initializes the PACE protocol by performing the "MSE: Set AT" step
// Returns 0 on success or a non-zero error code on failure
//-----------------------------------------------------------------------------
int EPA_PACE_MSE_Set_AT(pace_version_info_t pace_version_info, uint8_t password) {
    // create the MSE: Set AT APDU
    uint8_t apdu[23];
    // the minimum length (will be increased as more data is added)
    size_t apdu_length = 20;
    // copy the constant part
    memcpy(apdu,
           apdu_mse_set_at_start,
           sizeof(apdu_mse_set_at_start));
    // type: OID
    apdu[5] = 0x80;
    // length of the OID
    apdu[6] = sizeof(pace_version_info.oid);
    // copy the OID
    memcpy(apdu + 7,
           pace_version_info.oid,
           sizeof(pace_version_info.oid));
    // type: password
    apdu[17] = 0x83;
    // length: 1
    apdu[18] = 1;
    // password
    apdu[19] = password;
    // if standardized domain parameters are used, copy the ID
    if (pace_version_info.parameter_id != 0) {
        apdu_length += 3;
        // type: domain parameter
        apdu[20] = 0x84;
        // length: 1
        apdu[21] = 1;
        // copy the parameter ID
        apdu[22] = pace_version_info.parameter_id;
    }
    // now set Lc to the actual length
    apdu[4] = apdu_length - 5;
    // send it
    uint8_t response_apdu[6];
    int send_return = EPA_APDU(apdu,
                               apdu_length,
                               response_apdu);
    // check if the command succeeded
    if (send_return != 6
            || response_apdu[send_return - 4] != 0x90
            || response_apdu[send_return - 3] != 0x00) {
        return 1;
    }
    return 0;
}

//-----------------------------------------------------------------------------
// Perform the PACE protocol by replaying given APDUs
//-----------------------------------------------------------------------------
void EPA_PACE_Replay(PacketCommandNG *c) {
    uint32_t timings[ARRAYLEN(apdu_lengths_replay)] = {0};

    // if an APDU has been passed, save it
    if (c->oldarg[0] != 0) {
        // make sure it's not too big
        if (c->oldarg[2] > apdus_replay[c->oldarg[0] - 1].len) {
            reply_old(CMD_ACK, 1, 0, 0, NULL, 0);
        }
        memcpy(apdus_replay[c->oldarg[0] - 1].data + c->oldarg[1],
               c->data.asBytes,
               c->oldarg[2]);
        // save/update APDU length
        if (c->oldarg[1] == 0) {
            apdu_lengths_replay[c->oldarg[0] - 1] = c->oldarg[2];
        } else {
            apdu_lengths_replay[c->oldarg[0] - 1] += c->oldarg[2];
        }
        reply_old(CMD_ACK, 0, 0, 0, NULL, 0);
        return;
    }

    // return value of a function
    int func_return;

    // set up communication
    func_return = EPA_Setup();
    if (func_return != 0) {
        EPA_Finish();
        reply_old(CMD_ACK, 2, func_return, 0, NULL, 0);
        return;
    }

    // increase the timeout (at least some cards really do need this!)/////////////
    // iso14a_set_timeout(0x0003FFFF);

    // response APDU
    uint8_t response_apdu[300] = {0};

    // now replay the data and measure the timings
    for (int i = 0; i < ARRAYLEN(apdu_lengths_replay); i++) {
        StartCountUS();
        func_return = EPA_APDU(apdus_replay[i].data,
                               apdu_lengths_replay[i],
                               response_apdu);
        timings[i] = GetCountUS();
        // every step but the last one should succeed
        if (i < ARRAYLEN(apdu_lengths_replay) - 1
                && (func_return < 6
                    || response_apdu[func_return - 4] != 0x90
                    || response_apdu[func_return - 3] != 0x00)) {
            EPA_Finish();
            reply_old(CMD_ACK, 3 + i, func_return, 0, timings, 20);
            return;
        }
    }
    EPA_Finish();
    reply_old(CMD_ACK, 0, 0, 0, timings, 20);
    return;
}

//-----------------------------------------------------------------------------
// Set up a communication channel (Card Select, PPS)
// Returns 0 on success or a non-zero error code on failure
//-----------------------------------------------------------------------------
int EPA_Setup() {
    uint8_t uid[10];
    iso14a_card_select_t card_a_info;

    // first, look for type A cards
    // power up the field
    iso14443a_setup(FPGA_HF_ISO14443A_READER_MOD);
    // select the card
    int return_code = iso14443a_select_card(uid, &card_a_info, NULL, true, 0, false);
    if (return_code == 1) {
        uint8_t pps_response[3];
        uint8_t pps_response_par[1];
        // send the PPS request
        ReaderTransmit((uint8_t *)pps, sizeof(pps), NULL);
        return_code = ReaderReceive(pps_response, pps_response_par);
        if (return_code != 3 || pps_response[0] != 0xD0) {
            return return_code == 0 ? 2 : return_code;
        }
        Dbprintf("ISO 14443 Type A");
        iso_type = 'a';
        return 0;
    }

    // if we're here, there is no type A card, so we look for type B
    // power up the field
    iso14443b_setup();
    iso14b_card_select_t card_b_info;
    // select the card
    return_code = iso14443b_select_card(&card_b_info);
    if (return_code == 0) {
        Dbprintf("ISO 14443 Type B");
        iso_type = 'b';
        return 0;
    }
    Dbprintf("No card found.");
    return 1;
}
