pair.c

/*
 * The MIT License (MIT)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is furnished to do
 * so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h> // for isprint()
#include <assert.h>

#include <sodium.h>

#include "pair.h"
#include "pair-internal.h"

extern struct pair_definition pair_client_fruit;
extern struct pair_definition pair_client_homekit_normal;
extern struct pair_definition pair_client_homekit_transient;
extern struct pair_definition pair_server_homekit;

// Must be in sync with enum pair_type
static struct pair_definition *pair[] = {
    &pair_client_fruit,
    &pair_client_homekit_normal,
    &pair_client_homekit_transient,
    &pair_server_homekit,
};

/* ------------------------------ INITIALIZATION ---------------------------- */

bool
is_initialized(void)
{
  if (sodium_init() == -1)
    return false;

#if CONFIG_GCRYPT
  // According to libgcrypt documentation: "It is important that these
  // initialization steps are not done by a library but by the actual
  // application. A library using Libgcrypt might want to check for finished
  // initialization using:"
  if (!gcry_control (GCRYCTL_INITIALIZATION_FINISHED_P))
    return false;
#endif

  return true;
}


/* -------------------------- SHARED HASHING HELPERS ------------------------ */

int
hash_init(enum hash_alg alg, HashCTX *c)
{
#if CONFIG_OPENSSL
  switch (alg)
    {
      case HASH_SHA1  : return SHA1_Init(&c->sha);
      case HASH_SHA224: return SHA224_Init(&c->sha256);
      case HASH_SHA256: return SHA256_Init(&c->sha256);
      case HASH_SHA384: return SHA384_Init(&c->sha512);
      case HASH_SHA512: return SHA512_Init(&c->sha512);
      default:
        return -1;
    };
#elif CONFIG_GCRYPT
  gcry_error_t err;

  err = gcry_md_open(c, alg, 0);

  if (err)
    return -1;

  return 0;
#endif
}

int
hash_update(enum hash_alg alg, HashCTX *c, const void *data, size_t len)
{
#if CONFIG_OPENSSL
  switch (alg)
    {
      case HASH_SHA1  : return SHA1_Update(&c->sha, data, len);
      case HASH_SHA224: return SHA224_Update(&c->sha256, data, len);
      case HASH_SHA256: return SHA256_Update(&c->sha256, data, len);
      case HASH_SHA384: return SHA384_Update(&c->sha512, data, len);
      case HASH_SHA512: return SHA512_Update(&c->sha512, data, len);
      default:
        return -1;
    };
#elif CONFIG_GCRYPT
  gcry_md_write(*c, data, len);
  return 0;
#endif
}

int
hash_final(enum hash_alg alg, HashCTX *c, unsigned char *md)
{
#if CONFIG_OPENSSL
  switch (alg)
    {
      case HASH_SHA1  : return SHA1_Final(md, &c->sha);
      case HASH_SHA224: return SHA224_Final(md, &c->sha256);
      case HASH_SHA256: return SHA256_Final(md, &c->sha256);
      case HASH_SHA384: return SHA384_Final(md, &c->sha512);
      case HASH_SHA512: return SHA512_Final(md, &c->sha512);
      default:
        return -1;
    };
#elif CONFIG_GCRYPT
  unsigned char *buf = gcry_md_read(*c, alg);
  if (!buf)
    return -1;

  memcpy(md, buf, gcry_md_get_algo_dlen(alg));
  gcry_md_close(*c);
  return 0;
#endif
}

unsigned char *
hash(enum hash_alg alg, const unsigned char *d, size_t n, unsigned char *md)
{
#if CONFIG_OPENSSL
  switch (alg)
    {
      case HASH_SHA1  : return SHA1(d, n, md);
      case HASH_SHA224: return SHA224(d, n, md);
      case HASH_SHA256: return SHA256(d, n, md);
      case HASH_SHA384: return SHA384(d, n, md);
      case HASH_SHA512: return SHA512(d, n, md);
      default:
        return NULL;
    };
#elif CONFIG_GCRYPT
  gcry_md_hash_buffer(alg, md, d, n);
  return md;
#endif
}

int
hash_length(enum hash_alg alg)
{
#if CONFIG_OPENSSL
  switch (alg)
    {
      case HASH_SHA1  : return SHA_DIGEST_LENGTH;
      case HASH_SHA224: return SHA224_DIGEST_LENGTH;
      case HASH_SHA256: return SHA256_DIGEST_LENGTH;
      case HASH_SHA384: return SHA384_DIGEST_LENGTH;
      case HASH_SHA512: return SHA512_DIGEST_LENGTH;
      default:
        return -1;
    };
#elif CONFIG_GCRYPT
  return gcry_md_get_algo_dlen(alg);
#endif
}

int
hash_ab(enum hash_alg alg, unsigned char *md, const unsigned char *m1, int m1_len, const unsigned char *m2, int m2_len)
{
  HashCTX ctx;

  hash_init(alg, &ctx);
  hash_update(alg, &ctx, m1, m1_len);
  hash_update(alg, &ctx, m2, m2_len);
  return hash_final(alg, &ctx, md);
}

// See rfc5054 PAD()
bnum
H_nn_pad(enum hash_alg alg, const bnum n1, const bnum n2, int padded_len)
{
  bnum          bn;
  unsigned char *bin;
  unsigned char buff[SHA512_DIGEST_LENGTH];
  int           len_n1 = bnum_num_bytes(n1);
  int           len_n2 = bnum_num_bytes(n2);
  int           nbytes = 2 * padded_len;
  int           offset_n1 = padded_len - len_n1;
  int           offset_n2 = nbytes - len_n2;

  assert(len_n1 <= padded_len);
  assert(len_n2 <= padded_len);

  bin = calloc(1, nbytes);

  bnum_bn2bin(n1, bin + offset_n1, len_n1);
  bnum_bn2bin(n2, bin + offset_n2, len_n2);
  hash(alg, bin, nbytes, buff);
  free(bin);
  bnum_bin2bn(bn, buff, hash_length(alg));
  return bn;
}

bnum
H_ns(enum hash_alg alg, const bnum n, const unsigned char *bytes, int len_bytes)
{
  bnum          bn;
  unsigned char buff[SHA512_DIGEST_LENGTH];
  int           len_n  = bnum_num_bytes(n);
  int           nbytes = len_n + len_bytes;
  unsigned char *bin   = malloc(nbytes);

  bnum_bn2bin(n, bin, len_n);
  memcpy(bin + len_n, bytes, len_bytes);
  hash(alg, bin, nbytes, buff);
  free(bin);
  bnum_bin2bn(bn, buff, hash_length(alg));
  return bn;
}

void
update_hash_n(enum hash_alg alg, HashCTX *ctx, const bnum n)
{
  unsigned long len = bnum_num_bytes(n);
  unsigned char *n_bytes = malloc(len);

  bnum_bn2bin(n, n_bytes, len);
  hash_update(alg, ctx, n_bytes, len);
  free(n_bytes);
}

void
hash_num(enum hash_alg alg, const bnum n, unsigned char *dest)
{
  int           nbytes = bnum_num_bytes(n);
  unsigned char *bin   = malloc(nbytes);

  bnum_bn2bin(n, bin, nbytes);
  hash( alg, bin, nbytes, dest );
  free(bin);
}


/* ----------------------------- OTHER HELPERS -------------------------------*/

#ifdef DEBUG_PAIR
void
hexdump(const char *msg, uint8_t *mem, size_t len)
{
  int i, j;
  int hexdump_cols = 16;

  if (msg)
    printf("%s", msg);

  for (i = 0; i < len + ((len % hexdump_cols) ? (hexdump_cols - len % hexdump_cols) : 0); i++)
    {
      if(i % hexdump_cols == 0)
	printf("0x%06x: ", i);

      if (i < len)
	printf("%02x ", 0xFF & ((char*)mem)[i]);
      else
	printf("   ");

      if (i % hexdump_cols == (hexdump_cols - 1))
	{
	  for (j = i - (hexdump_cols - 1); j <= i; j++)
	    {
	      if (j >= len)
		putchar(' ');
	      else if (isprint(((char*)mem)[j]))
		putchar(0xFF & ((char*)mem)[j]);
	      else
		putchar('.');
	    }

	  putchar('\n');
	}
    }
}

void
bnum_dump(const char *msg, bnum n)
{
  int len_n = bnum_num_bytes(n);
  uint8_t *bin = calloc(1, len_n);
  bnum_bn2bin(n, bin, len_n);
  hexdump(msg, bin, len_n);
  free(bin);
}
#endif


/* ----------------------------------- API -----------------------------------*/

struct pair_setup_context *
pair_setup_new(enum pair_type type, const char *pin, pair_cb add_cb, void *cb_arg, const char *device_id)
{
  struct pair_setup_context *sctx;

  if (!pair[type]->pair_setup_new)
    return NULL;

  sctx = calloc(1, sizeof(struct pair_setup_context));
  if (!sctx)
    return NULL;

  sctx->type = pair[type];

  if (pair[type]->pair_setup_new(sctx, pin, add_cb, cb_arg, device_id) < 0)
    {
      free(sctx);
      return NULL;
    }

  return sctx;
}

void
pair_setup_free(struct pair_setup_context *sctx)
{
  if (!sctx)
    return;

  if (sctx->type->pair_setup_free)
    sctx->type->pair_setup_free(sctx);

  free(sctx);
}

const char *
pair_setup_errmsg(struct pair_setup_context *sctx)
{
  return sctx->errmsg;
}

int
pair_setup(uint8_t **out, size_t *out_len, struct pair_setup_context *sctx, const uint8_t *in, size_t in_len)
{
  int state;
  int ret = -1;

  if (!sctx->type->pair_state_get)
    {
      sctx->errmsg = "Getting pair state unsupported";
      return -1;
    }

  *out = NULL;
  *out_len = 0;

  state = sctx->type->pair_state_get(&sctx->errmsg, in, in_len);
  if (state < 0)
    return -1;

  switch (state)
    {
      case 0:
        *out = pair_setup_request1(out_len, sctx);
        break;
      case 1:
        ret = pair_setup_response1(sctx, in, in_len);
        if (ret < 0)
          break;
        *out = pair_setup_request1(out_len, sctx);
        break;
      case 2:
        ret = pair_setup_response1(sctx, in, in_len);
        if (ret < 0)
          break;
        *out = pair_setup_request2(out_len, sctx);
        break;
      case 3:
        ret = pair_setup_response2(sctx, in, in_len);
        if (ret < 0)
          break;
        *out = pair_setup_request2(out_len, sctx);
        break;
      case 4:
        ret = pair_setup_response2(sctx, in, in_len);
        if (ret < 0)
          break;
        *out = pair_setup_request3(out_len, sctx);
        break;
      case 5:
        ret = pair_setup_response3(sctx, in, in_len);
        if (ret < 0)
          break;
        *out = pair_setup_request3(out_len, sctx);
        break;
      case 6:
        ret = pair_setup_response3(sctx, in, in_len);
        if (ret < 0)
          break;
        break;
      default:
        sctx->errmsg = "Setup: Unsupported state";
        ret = -1;
    }

  if (ret < 0 || !(*out))
    return -1;

  return 0;
}

uint8_t *
pair_setup_request1(size_t *len, struct pair_setup_context *sctx)
{
  if (!sctx->type->pair_setup_request1)
    {
      sctx->errmsg = "Setup request 1: Unsupported";
      return NULL;
    }

  return sctx->type->pair_setup_request1(len, sctx);
}

uint8_t *
pair_setup_request2(size_t *len, struct pair_setup_context *sctx)
{
  if (!sctx->type->pair_setup_request2)
    {
      sctx->errmsg = "Setup request 2: Unsupported";
      return NULL;
    }

  return sctx->type->pair_setup_request2(len, sctx);
}

uint8_t *
pair_setup_request3(size_t *len, struct pair_setup_context *sctx)
{
  if (!sctx->type->pair_setup_request3)
    {
      sctx->errmsg = "Setup request 3: Unsupported";
      return NULL;
    }

  return sctx->type->pair_setup_request3(len, sctx);
}

int
pair_setup_response1(struct pair_setup_context *sctx, const uint8_t *in, size_t in_len)
{
  if (!sctx->type->pair_setup_response1)
    {
      sctx->errmsg = "Setup response 1: Unsupported";
      return -1;
    }

  return sctx->type->pair_setup_response1(sctx, in, in_len);
}

int
pair_setup_response2(struct pair_setup_context *sctx, const uint8_t *in, size_t in_len)
{
  if (!sctx->type->pair_setup_response2)
    {
      sctx->errmsg = "Setup response 2: Unsupported";
      return -1;
    }

  return sctx->type->pair_setup_response2(sctx, in, in_len);
}

int
pair_setup_response3(struct pair_setup_context *sctx, const uint8_t *in, size_t in_len)
{
  if (!sctx->type->pair_setup_response3)
    {
      sctx->errmsg = "Setup response 3: Unsupported";
      return -1;
    }

  if (sctx->type->pair_setup_response3(sctx, in, in_len) != 0)
    return -1;

  return 0;
}

int
pair_setup_result(const char **client_setup_keys, struct pair_result **result, struct pair_setup_context *sctx)
{
  if (sctx->status != PAIR_STATUS_COMPLETED)
    {
      sctx->errmsg = "Setup result: Pair setup has not been completed";
      return -1;
    }

  if (sctx->type->pair_setup_result)
    {
      if (sctx->type->pair_setup_result(sctx) != 0)
	return -1;
    }

  if (client_setup_keys)
    *client_setup_keys = sctx->result_str;
  if (result)
    *result = &sctx->result;
  return 0;
}

struct pair_verify_context *
pair_verify_new(enum pair_type type, const char *client_setup_keys, pair_cb get_cb, void *cb_arg, const char *device_id)
{
  struct pair_verify_context *vctx;

  if (!pair[type]->pair_verify_new)
    return NULL;

  vctx = calloc(1, sizeof(struct pair_verify_context));
  if (!vctx)
    return NULL;

  vctx->type = pair[type];

  if (pair[type]->pair_verify_new(vctx, client_setup_keys, get_cb, cb_arg, device_id) < 0)
    {
      free(vctx);
      return NULL;
    }

  return vctx;
}

void
pair_verify_free(struct pair_verify_context *vctx)
{
  if (!vctx)
    return;

  if (vctx->type->pair_verify_free)
    vctx->type->pair_verify_free(vctx);

  free(vctx);
}

const char *
pair_verify_errmsg(struct pair_verify_context *vctx)
{
  return vctx->errmsg;
}

int
pair_verify(uint8_t **out, size_t *out_len, struct pair_verify_context *vctx, const uint8_t *in, size_t in_len)
{
  int state;
  int ret = -1;

  if (!vctx->type->pair_state_get)
    {
      vctx->errmsg = "Getting pair state unsupported";
      return -1;
    }

  *out = NULL;
  *out_len = 0;

  state = vctx->type->pair_state_get(&vctx->errmsg, in, in_len);
  if (state < 0)
    return -1;

  switch (state)
    {
      case 0:
        *out = pair_verify_request1(out_len, vctx);
        break;
      case 1:
        ret = pair_verify_response1(vctx, in, in_len);
        if (ret < 0)
          break;
        *out = pair_verify_request1(out_len, vctx);
        break;
      case 2:
        ret = pair_verify_response1(vctx, in, in_len);
        if (ret < 0)
          break;
        *out = pair_verify_request2(out_len, vctx);
        break;
      case 3:
        ret = pair_verify_response2(vctx, in, in_len);
        if (ret < 0)
          break;
        *out = pair_verify_request2(out_len, vctx);
        break;
      case 4:
        ret = pair_verify_response2(vctx, in, in_len);
        if (ret < 0)
          break;
        break;
      default:
        vctx->errmsg = "Verify: Unsupported state";
        ret = -1;
    }

  if (ret < 0 || !(*out))
    return -1;

  return 0;
}

uint8_t *
pair_verify_request1(size_t *len, struct pair_verify_context *vctx)
{
  if (!vctx->type->pair_verify_request1)
    {
      vctx->errmsg = "Verify request 1: Unsupported";
      return NULL;
    }

  return vctx->type->pair_verify_request1(len, vctx);
}

uint8_t *
pair_verify_request2(size_t *len, struct pair_verify_context *vctx)
{
  if (!vctx->type->pair_verify_request2)
    {
      vctx->errmsg = "Verify request 2: Unsupported";
      return NULL;
    }

  return vctx->type->pair_verify_request2(len, vctx);
}

int
pair_verify_response1(struct pair_verify_context *vctx, const uint8_t *in, size_t in_len)
{
  if (!vctx->type->pair_verify_response1)
    {
      vctx->errmsg = "Verify response 1: Unsupported";
      return -1;
    }

  return vctx->type->pair_verify_response1(vctx, in, in_len);
}

int
pair_verify_response2(struct pair_verify_context *vctx, const uint8_t *in, size_t in_len)
{
  if (!vctx->type->pair_verify_response2)
    {
      vctx->errmsg = "Verify response 2: Unsupported";
      return -1;
    }

  if (vctx->type->pair_verify_response2(vctx, in, in_len) != 0)
    return -1;

  return 0;
}

int
pair_verify_result(struct pair_result **result, struct pair_verify_context *vctx)
{
  if (vctx->status != PAIR_STATUS_COMPLETED)
    {
      vctx->errmsg = "Verify result: The pairing verification did not complete";
      return -1;
    }

  if (vctx->type->pair_verify_result)
    {
      if (vctx->type->pair_verify_result(vctx) != 0)
	return -1;
    }

  if (result)
    *result = &vctx->result;
  return 0;
}

struct pair_cipher_context *
pair_cipher_new(enum pair_type type, int channel, const uint8_t *shared_secret, size_t shared_secret_len)
{
  if (!pair[type]->pair_cipher_new)
    return NULL;

  return pair[type]->pair_cipher_new(pair[type], channel, shared_secret, shared_secret_len);
}

void
pair_cipher_free(struct pair_cipher_context *cctx)
{
  if (!cctx)
    return;

  if (!cctx->type->pair_cipher_free)
    return;

  return cctx->type->pair_cipher_free(cctx);
}

const char *
pair_cipher_errmsg(struct pair_cipher_context *cctx)
{
  return cctx->errmsg;
}

ssize_t
pair_encrypt(uint8_t **ciphertext, size_t *ciphertext_len, const uint8_t *plaintext, size_t plaintext_len, struct pair_cipher_context *cctx)
{
  if (!cctx->type->pair_encrypt)
    {
      cctx->errmsg = "Encryption unsupported";
      return -1;
    }

  return cctx->type->pair_encrypt(ciphertext, ciphertext_len, plaintext, plaintext_len, cctx);
}

ssize_t
pair_decrypt(uint8_t **plaintext, size_t *plaintext_len, const uint8_t *ciphertext, size_t ciphertext_len, struct pair_cipher_context *cctx)
{
  if (!cctx->type->pair_decrypt)
    {
      cctx->errmsg = "Decryption unsupported";
      return -1;
    }

  return cctx->type->pair_decrypt(plaintext, plaintext_len, ciphertext, ciphertext_len, cctx);
}

void
pair_encrypt_rollback(struct pair_cipher_context *cctx)
{
  cctx->encryption_counter = cctx->encryption_counter_prev;
}

void
pair_decrypt_rollback(struct pair_cipher_context *cctx)
{
  cctx->decryption_counter = cctx->decryption_counter_prev;
}

int
pair_add(enum pair_type type, uint8_t **out, size_t *out_len, pair_cb add_cb, void *cb_arg, const uint8_t *in, size_t in_len)
{
  if (!pair[type]->pair_add)
    {
      return -1;
    }

  return pair[type]->pair_add(out, out_len, add_cb, cb_arg, in, in_len);
}

int
pair_remove(enum pair_type type, uint8_t **out, size_t *out_len, pair_cb remove_cb, void *cb_arg, const uint8_t *in, size_t in_len)
{
  if (!pair[type]->pair_remove)
    {
      return -1;
    }

  return pair[type]->pair_remove(out, out_len, remove_cb, cb_arg, in, in_len);
}

int
pair_list(enum pair_type type, uint8_t **out, size_t *out_len, pair_list_cb list_cb, void *cb_arg, const uint8_t *in, size_t in_len)
{
  if (!pair[type]->pair_list)
    {
      return -1;
    }

  return pair[type]->pair_list(out, out_len, list_cb, cb_arg, in, in_len);
}

int
pair_state_get(enum pair_type type, const char **errmsg, const uint8_t *in, size_t in_len)
{
  if (!pair[type]->pair_state_get)
    {
      *errmsg = "Getting pair state unsupported";
      return -1;
    }

  return pair[type]->pair_state_get(errmsg, in, in_len);
}

void
pair_public_key_get(enum pair_type type, uint8_t server_public_key[32], const char *device_id)
{
  if (!pair[type]->pair_public_key_get)
    {
      return;
    }

  pair[type]->pair_public_key_get(server_public_key, device_id);
}