/*
 * Copyright (c) 2014 Yubico AB
 * All rights reserved.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 *
 * Additional permission under GNU GPL version 3 section 7
 *
 * If you modify this program, or any covered work, by linking or
 * combining it with the OpenSSL project's OpenSSL library (or a
 * modified version of that library), containing parts covered by the
 * terms of the OpenSSL or SSLeay licenses, We grant you additional 
 * permission to convey the resulting work. Corresponding Source for a
 * non-source form of such a combination shall include the source code
 * for the parts of OpenSSL used as well as that of the covered work.
 *
 */

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <stdint.h>

#include <openssl/des.h>
#include <openssl/rand.h>

#include "internal.h"
#include "ykpiv.h"

static void dump_hex(const unsigned char *buf, unsigned int len) {
  unsigned int i;
  for (i = 0; i < len; i++) {
    fprintf(stderr, "%02x ", buf[i]);
  }
}

static int set_length(unsigned char *buffer, int length) {
  if(length < 0x80) {
    *buffer++ = length;
    return 1;
  } else if(length < 0xff) {
    *buffer++ = 0x81;
    *buffer++ = length;
    return 2;
  } else {
    *buffer++ = 0x82;
    *buffer++ = (length >> 8) & 0xff;
    *buffer++ = length & 0xff;
    return 3;
  }
}

static int get_length(unsigned char *buffer, int *len) {
  if(buffer[0] < 0x81) {
    *len = buffer[0];
    return 1;
  } else if((*buffer & 0x7f) == 1) {
    *len = buffer[1];
    return 2;
  } else if((*buffer & 0x7f) == 2) {
    *len = (buffer[1] << 8) + buffer[2];
    return 3;
  }
  return 0;
}

ykpiv_rc ykpiv_init(ykpiv_state **state, int verbose) {
  ykpiv_state *s = malloc(sizeof(ykpiv_state));
  if(s == NULL) {
    return YKPIV_MEMORY_ERROR;
  }
  memset(s, 0, sizeof(ykpiv_state));
  s->verbose = verbose;
  *state = s;
  return YKPIV_OK;
}

ykpiv_rc ykpiv_done(ykpiv_state *state) {
  ykpiv_disconnect(state);
  free(state);
  return YKPIV_OK;
}

ykpiv_rc ykpiv_disconnect(ykpiv_state *state) {
  if(state->card) {
    SCardDisconnect(state->card, SCARD_RESET_CARD);
    state->card = 0;
  }

  if(state->context) {
    SCardReleaseContext(state->context);
    state->context = 0;
  }

  return YKPIV_OK;
}

ykpiv_rc ykpiv_connect(ykpiv_state *state, const char *wanted) {
  unsigned long num_readers = 0;
  unsigned long active_protocol;
  char reader_buf[1024];
  long rc;
  char *reader_ptr;

  rc = SCardEstablishContext(SCARD_SCOPE_SYSTEM, NULL, NULL, &state->context);
  if (rc != SCARD_S_SUCCESS) {
    if(state->verbose) {
      fprintf (stderr, "error: SCardEstablishContext failed, rc=%08lx\n", rc);
    }
    return YKPIV_PCSC_ERROR;
  }

  rc = SCardListReaders(state->context, NULL, NULL, &num_readers);
  if (rc != SCARD_S_SUCCESS) {
    if(state->verbose) {
      fprintf (stderr, "error: SCardListReaders failed, rc=%08lx\n", rc);
    }
    SCardReleaseContext(state->context);
    return YKPIV_PCSC_ERROR;
  }

  if (num_readers > sizeof(reader_buf)) {
    num_readers = sizeof(reader_buf);
  }

  rc = SCardListReaders(state->context, NULL, reader_buf, &num_readers);
  if (rc != SCARD_S_SUCCESS)
  {
    if(state->verbose) {
      fprintf (stderr, "error: SCardListReaders failed, rc=%08lx\n", rc);
    }
    SCardReleaseContext(state->context);
    return YKPIV_PCSC_ERROR;
  }

  reader_ptr = reader_buf;
  if(wanted) {
    while(*reader_ptr != '\0') {
      if(strstr(reader_ptr, wanted)) {
	if(state->verbose) {
	  fprintf(stderr, "using reader '%s' matching '%s'.\n", reader_ptr, wanted);
	}
	break;
      } else {
	if(state->verbose) {
	  fprintf(stderr, "skipping reader '%s' since it doesn't match.\n", reader_ptr);
	}
	reader_ptr += strlen(reader_ptr) + 1;
      }
    }
  }
  if(*reader_ptr == '\0') {
    if(state->verbose) {
      fprintf(stderr, "error: no useable reader found.\n");
    }
    SCardReleaseContext(state->context);
    return YKPIV_PCSC_ERROR;
  }

  rc = SCardConnect(state->context, reader_ptr, SCARD_SHARE_SHARED,
      SCARD_PROTOCOL_T1, &state->card, &active_protocol);
  if(rc != SCARD_S_SUCCESS)
  {
    if(state->verbose) {
      fprintf(stderr, "error: SCardConnect failed, rc=%08lx\n", rc);
    }
    SCardReleaseContext(state->context);
    return YKPIV_PCSC_ERROR;
  }

  {
    APDU apdu;
    unsigned char data[0xff];
    unsigned long recv_len = sizeof(data);
    int sw;
    ykpiv_rc res;

    memset(apdu.raw, 0, sizeof(apdu));
    apdu.st.ins = 0xa4;
    apdu.st.p1 = 0x04;
    apdu.st.lc = sizeof(aid);
    memcpy(apdu.st.data, aid, sizeof(aid));

    if((res = ykpiv_send_data(state, apdu.raw, data, &recv_len, &sw) != YKPIV_OK)) {
      return res;
    } else if(sw == 0x9000) {
      return YKPIV_OK;
    }

    return YKPIV_APPLET_ERROR;
  }

  return YKPIV_OK;
}

ykpiv_rc ykpiv_transfer_data(ykpiv_state *state, const unsigned char *templ,
    const unsigned char *in_data, long in_len,
    unsigned char *out_data, unsigned long *out_len, int *sw) {
  const unsigned char *in_ptr = in_data;
  unsigned long max_out = *out_len;
  ykpiv_rc res;
  *out_len = 0;

  while(in_ptr < in_data + in_len) {
    size_t this_size = 0xff;
    unsigned long recv_len = 0xff;
    unsigned char data[0xff];
    APDU apdu;

    memset(apdu.raw, 0, sizeof(apdu.raw));
    memcpy(apdu.raw, templ, 4);
    if(in_ptr + 0xff < in_data + in_len) {
      apdu.st.cla = 0x10;
    } else {
      this_size = (size_t)((in_data + in_len) - in_ptr);
    }
    if(state->verbose > 2) {
      fprintf(stderr, "Going to send %lu bytes in this go.\n", (unsigned long)this_size);
    }
    apdu.st.lc = this_size;
    memcpy(apdu.st.data, in_ptr, this_size);
    res = ykpiv_send_data(state, apdu.raw, data, &recv_len, sw);
    if(res != YKPIV_OK) {
      return res;
    } else if(*sw != 0x9000 && *sw >> 8 != 0x61) {
      return YKPIV_OK;
    }
    if(*out_len + recv_len - 2 > max_out) {
      if(state->verbose) {
	fprintf(stderr, "Output buffer to small, wanted to write %lu, max was %lu.\n", *out_len + recv_len - 2, max_out);
      }
      return YKPIV_SIZE_ERROR;
    }
    memcpy(out_data, data, recv_len - 2);
    out_data += recv_len - 2;
    *out_len += recv_len - 2;
    in_ptr += this_size;
  }
  while(*sw >> 8 == 0x61) {
    APDU apdu;
    unsigned long recv_len = 0xff;
    unsigned char data[0xff];

    if(state->verbose > 2) {
      fprintf(stderr, "The card indicates there is %d bytes more data for us.\n", *sw & 0xff);
    }

    memset(apdu.raw, 0, sizeof(apdu.raw));
    apdu.st.ins = 0xc0;
    res = ykpiv_send_data(state, apdu.raw, data, &recv_len, sw);
    if(res != YKPIV_OK) {
      return res;
    } else if(*sw != 0x9000 && *sw >> 8 != 0x61) {
      return YKPIV_OK;
    }
    if(*out_len + recv_len - 2 > max_out) {
      fprintf(stderr, "Output buffer to small, wanted to write %lu, max was %lu.", *out_len + recv_len - 2, max_out);
    }
    memcpy(out_data, data, recv_len - 2);
    out_data += recv_len - 2;
    *out_len += recv_len - 2;
  }
  return YKPIV_OK;
}

ykpiv_rc ykpiv_send_data(ykpiv_state *state, unsigned char *apdu,
    unsigned char *data, unsigned long *recv_len, int *sw) {
  long rc;
  unsigned int send_len = (unsigned int)(apdu[4] + 5); /* magic numbers.. */

  if(state->verbose > 1) {
    fprintf(stderr, "> ");
    dump_hex(apdu, send_len);
    fprintf(stderr, "\n");
  }
  rc = SCardTransmit(state->card, SCARD_PCI_T1, apdu, send_len, NULL, data, recv_len);
  if(rc != SCARD_S_SUCCESS) {
    if(state->verbose) {
      fprintf (stderr, "error: SCardTransmit failed, rc=%08lx\n", rc);
    }
    return YKPIV_PCSC_ERROR;
  }

  if(state->verbose > 1) {
    fprintf(stderr, "< ");
    dump_hex(data, *recv_len);
    fprintf(stderr, "\n");
  }
  if(*recv_len >= 2) {
    *sw = (data[*recv_len - 2] << 8) | data[*recv_len - 1];
  } else {
    *sw = 0;
  }
  return YKPIV_OK;
}

ykpiv_rc ykpiv_authenticate(ykpiv_state *state, unsigned const char *key) {
  APDU apdu;
  unsigned char data[0xff];
  DES_cblock challenge;
  unsigned long recv_len = sizeof(data);
  int sw;
  ykpiv_rc res;

  DES_key_schedule ks1, ks2, ks3;

  /* set up our key */
  {
    const_DES_cblock key_tmp;
    memcpy(key_tmp, key, 8);
    DES_set_key_unchecked(&key_tmp, &ks1);
    memcpy(key_tmp, key + 8, 8);
    DES_set_key_unchecked(&key_tmp, &ks2);
    memcpy(key_tmp, key + 16, 8);
    DES_set_key_unchecked(&key_tmp, &ks3);
  }

  /* get a challenge from the card */
  {
    memset(apdu.raw, 0, sizeof(apdu));
    apdu.st.ins = 0x87;
    apdu.st.p1 = 0x03; /* triple des */
    apdu.st.p2 = 0x9b; /* management key */
    apdu.st.lc = 0x04;
    apdu.st.data[0] = 0x7c;
    apdu.st.data[1] = 0x02;
    apdu.st.data[2] = 0x80;
    if((res = ykpiv_send_data(state, apdu.raw, data, &recv_len, &sw)) != YKPIV_OK) {
      return res;
    } else if(sw != 0x9000) {
      return YKPIV_AUTHENTICATION_ERROR;
    }
    memcpy(challenge, data + 4, 8);
  }

  /* send a response to the cards challenge and a challenge of our own. */
  {
    unsigned char *dataptr = apdu.st.data;
    DES_cblock response;
    DES_ecb3_encrypt(&challenge, &response, &ks1, &ks2, &ks3, 0);

    recv_len = 0xff;
    memset(apdu.raw, 0, sizeof(apdu));
    apdu.st.ins = YKPIV_INS_AUTHENTICATE;
    apdu.st.p1 = YKPIV_ALGO_3DES; /* triple des */
    apdu.st.p2 = YKPIV_KEY_CARDMGM; /* management key */
    *dataptr++ = 0x7c;
    *dataptr++ = 20; /* 2 + 8 + 2 +8 */
    *dataptr++ = 0x80;
    *dataptr++ = 8;
    memcpy(dataptr, response, 8);
    dataptr += 8;
    *dataptr++ = 0x81;
    *dataptr++ = 8;
    if(RAND_pseudo_bytes(dataptr, 8) == -1) {
      if(state->verbose) {
	fprintf(stderr, "Failed getting randomness for authentication.\n");
      }
      return YKPIV_RANDOMNESS_ERROR;
    }
    memcpy(challenge, dataptr, 8);
    dataptr += 8;
    apdu.st.lc = dataptr - apdu.st.data;
    if((res = ykpiv_send_data(state, apdu.raw, data, &recv_len, &sw)) != YKPIV_OK) {
      return res;
    } else if(sw != 0x9000) {
      return YKPIV_AUTHENTICATION_ERROR;
    }
  }

  /* compare the response from the card with our challenge */
  {
    DES_cblock response;
    DES_ecb3_encrypt(&challenge, &response, &ks1, &ks2, &ks3, 1);
    if(memcmp(response, data + 4, 8) == 0) {
      return YKPIV_OK;
    } else {
      return YKPIV_AUTHENTICATION_ERROR;
    }
  }
}

ykpiv_rc ykpiv_set_mgmkey(ykpiv_state *state, const unsigned char *new_key) {
  APDU apdu;
  unsigned char data[0xff];
  unsigned long recv_len = sizeof(data);
  int sw;
  size_t i;
  ykpiv_rc res;

  for(i = 0; i < 3; i++) {
    const_DES_cblock key_tmp;
    memcpy(key_tmp, new_key + i * 8, 8);
    if(DES_is_weak_key(&key_tmp) == 1) {
      if(state->verbose) {
	fprintf(stderr, "Won't set new key '");
	dump_hex(new_key + i, 8);
	fprintf(stderr, "' since it's considered weak.\n");
      }
      return YKPIV_GENERIC_ERROR;
    }
  }

  memset(apdu.raw, 0, sizeof(apdu));
  apdu.st.ins = YKPIV_INS_SET_MGMKEY;
  apdu.st.p1 = 0xff;
  apdu.st.p2 = 0xff;
  apdu.st.lc = DES_KEY_SZ * 3 + 3;
  apdu.st.data[0] = YKPIV_ALGO_3DES;
  apdu.st.data[1] = YKPIV_KEY_CARDMGM;
  apdu.st.data[2] = DES_KEY_SZ * 3;
  memcpy(apdu.st.data + 3, new_key, DES_KEY_SZ * 3);
  if((res = ykpiv_send_data(state, apdu.raw, data, &recv_len, &sw)) != YKPIV_OK) {
    return res;
  } else if(sw == 0x9000) {
    return YKPIV_OK;
  }
  return YKPIV_GENERIC_ERROR;
}

ykpiv_rc ykpiv_parse_key(ykpiv_state *state,
    const char *key_in, unsigned char *key_out) {
  unsigned int i;
  char key_part[4] = {0};
  int key_len = strlen(key_in);

  if(key_len != DES_KEY_SZ * 3 * 2) {
    if(state->verbose) {
      fprintf(stderr, "Wrong key size, should be %lu characters (was %d).\n", DES_KEY_SZ * 3 * 2, key_len);
    }
    return YKPIV_SIZE_ERROR;
  }
  for(i = 0; i < DES_KEY_SZ * 3; i++) {
    key_part[0] = *key_in++;
    key_part[1] = *key_in++;
    if(sscanf(key_part, "%hhx", &key_out[i]) != 1) {
      if(state->verbose) {
	fprintf(stderr, "Failed parsing key at position %d.\n", i);
      }
      return YKPIV_KEY_ERROR;
    }
  }
  if(state->verbose > 1) {
    fprintf(stderr, "parsed key: ");
    dump_hex(key_out, DES_KEY_SZ * 3);
    fprintf(stderr, "\n");
  }
  return YKPIV_OK;
}

ykpiv_rc ykpiv_sign_data(ykpiv_state *state,
    const unsigned char *sign_in, int in_len,
    unsigned char *sign_out, int *out_len,
    unsigned char algorithm, unsigned char key) {

  unsigned char indata[1024];
  unsigned char *dataptr = indata;
  unsigned char data[1024];
  unsigned char templ[] = {0, YKPIV_INS_AUTHENTICATE, algorithm, key};
  unsigned long recv_len = sizeof(data);
  int sw;
  int bytes;
  int len = 0;
  ykpiv_rc res;

  if(in_len > 1000) {
    return YKPIV_SIZE_ERROR;
  }

  if(in_len < 0x80) {
    bytes = 1;
  } else if(in_len < 0xff) {
    bytes = 2;
  } else {
    bytes = 3;
  }

  *dataptr++ = 0x7c;
  dataptr += set_length(dataptr, in_len + bytes + 3);
  *dataptr++ = 0x82;
  *dataptr++ = 0x00;
  *dataptr++ = 0x81;
  dataptr += set_length(dataptr, in_len);
  memcpy(dataptr, sign_in, (size_t)in_len);
  dataptr += in_len;

  if((res = ykpiv_transfer_data(state, templ, indata, dataptr - indata, data,
        &recv_len, &sw)) != YKPIV_OK) {
    if(state->verbose) {
      fprintf(stderr, "Sign command failed to communicate.\n");
    }
    return res;
  } else if(sw != 0x9000) {
    if(state->verbose) {
      fprintf(stderr, "Failed sign command with code %x.\n", sw);
    }
    return YKPIV_GENERIC_ERROR;
  }
  /* skip the first 7c tag */
  if(data[0] != 0x7c) {
    if(state->verbose) {
      fprintf(stderr, "Failed parsing signature reply.\n");
    }
    return YKPIV_PARSE_ERROR;
  }
  dataptr = data + 1;
  dataptr += get_length(dataptr, &len);
  /* skip the 82 tag */
  if(*dataptr != 0x82) {
    if(state->verbose) {
      fprintf(stderr, "Failed parsing signature reply.\n");
    }
    return YKPIV_PARSE_ERROR;
  }
  dataptr++;
  dataptr += get_length(dataptr, &len);
  if(len > *out_len) {
    if(state->verbose) {
      fprintf(stderr, "Wrong size on output buffer.\n");
    }
    return YKPIV_SIZE_ERROR;
  }
  *out_len = len;
  memcpy(sign_out, dataptr, len);
  return YKPIV_OK;
}

ykpiv_rc ykpiv_get_version(ykpiv_state *state, char *version, size_t len) {
  APDU apdu;
  unsigned char data[0xff];
  unsigned long recv_len = sizeof(data);
  int sw;
  ykpiv_rc res;

  memset(apdu.raw, 0, sizeof(apdu));
  apdu.st.ins = YKPIV_INS_GET_VERSION;
  if((res = ykpiv_send_data(state, apdu.raw, data, &recv_len, &sw)) != YKPIV_OK) {
    return res;
  } else if(sw == 0x9000) {
    int result = snprintf(version, len, "%d.%d.%d", data[0], data[1], data[2]);
    if(result < 0) {
      return YKPIV_SIZE_ERROR;
    }
    return YKPIV_OK;
  } else {
    return YKPIV_GENERIC_ERROR;
  }
}

ykpiv_rc ykpiv_verify(ykpiv_state *state, const char *pin, int *tries) {
  APDU apdu;
  unsigned char data[0xff];
  unsigned long recv_len = sizeof(data);
  int sw;
  size_t len = strlen(pin);
  ykpiv_rc res;

  if(len > 8) {
    return YKPIV_SIZE_ERROR;
  }

  memset(apdu.raw, 0, sizeof(apdu.raw));
  apdu.st.ins = YKPIV_INS_VERIFY;
  apdu.st.p1 = 0x00;
  apdu.st.p2 = 0x80;
  apdu.st.lc = 0x08;
  memcpy(apdu.st.data, pin, len);
  if(len < 8) {
    memset(apdu.st.data + len, 0xff, 8 - len);
  }
  if((res = ykpiv_send_data(state, apdu.raw, data, &recv_len, &sw)) != YKPIV_OK) {
    return res;
  } else if(sw == 0x9000) {
    return YKPIV_OK;
  } else if((sw >> 8) == 0x63) {
    if(state->verbose) {
      fprintf(stderr, "Pin verification failed, %d tries left before pin is blocked.\n", sw & 0xff);
    }
    *tries = (sw & 0xff);
    return YKPIV_WRONG_PIN;
  } else if(sw == 0x6983) {
    if(state->verbose) {
      fprintf(stderr, "Pin code blocked, use unblock-pin action to unblock.\n");
    }
    *tries = 0;
    return YKPIV_WRONG_PIN;
  } else {
    if(state->verbose) {
      fprintf(stderr, "Pin code verification failed with code %x.\n", sw);
    }
    return YKPIV_GENERIC_ERROR;
  }
}