crypto.c

一个开源的VPN原码

      /* make sure IV changed */
      if (!memcmp (iv_save, co->iv, EVP_MAX_IV_LENGTH))
	  msg (M_FATAL, "IV Collision: before:%s after:%s",
	       format_hex (iv_save, EVP_MAX_IV_LENGTH, 0),
	       format_hex (co->iv, EVP_MAX_IV_LENGTH, 0));

      /* decrypt */
      openvpn_decrypt (&buf, decrypt_workspace, co, frame, current);

      /* compare */
      if (buf.len != src.len)
	msg (M_FATAL, "SELF TEST FAILED, src.len=%d buf.len=%d", src.len, buf.len);
      for (j = 0; j < i; ++j)
	{
	  const uint8_t in = *(BPTR (&src) + j);
	  const uint8_t out = *(BPTR (&buf) + j);
	  if (in != out)
	    msg (M_FATAL, "SELF TEST FAILED, pos=%d in=%d out=%d", j, in, out);
	}
    }
  msg (M_INFO, "OpenVPN crypto self-test mode SUCCEEDED.");
}

#ifdef USE_SSL
void
get_tls_handshake_key (const struct key_type *key_type,
		       struct key_ctx_bi *ctx, const char *passphrase_file)
{
  if (passphrase_file && key_type->hmac_length)
    {
      struct key key;
      struct key_type kt = *key_type;

      /* for control channel we are only authenticating, not encrypting */
      kt.cipher_length = 0;
      kt.cipher = NULL;

      /* get key material for hmac */
      {
	int digest_len;
	uint8_t digest[MAX_HMAC_KEY_LENGTH];
	EVP_MD_CTX md;

	CLEAR (key);
	EVP_DigestInit (&md, kt.digest);

	/* read passphrase file */
	{
	  const int min_passphrase_size = 8;
	  uint8_t buf[512];
	  int total_size = 0;
	  int fd = open (passphrase_file, O_RDONLY);

	  if (fd == -1)
	    msg (M_ERR, "Cannot open passphrase file: %s", passphrase_file);

	  for (;;)
	    {
	      int size = read (fd, buf, sizeof (buf));
	      if (size == 0)
		break;
	      if (size == -1)
		msg (M_ERR, "Read error on passphrase file: %s",
		     passphrase_file);
	      EVP_DigestUpdate (&md, buf, size);
	      total_size += size;
	    }
	  close (fd);
	  warn_if_group_others_accessible (passphrase_file);
	  if (total_size < min_passphrase_size)
	    msg (M_FATAL,
		 "Passphrase file %s is too small (must have at least %d characters)",
		 passphrase_file, min_passphrase_size);
	}

	EVP_DigestFinal (&md, digest, &digest_len);
	ASSERT (digest_len == kt.hmac_length);
	memcpy (key.hmac, digest, digest_len);
	CLEAR (digest);
	EVP_MD_CTX_cleanup (&md);
      }

      /* use same hmac key in both directions */

      init_key_ctx (&ctx->encrypt, &key, &kt, DO_ENCRYPT,
		    "Outgoing Control Channel Authentication");
      init_key_ctx (&ctx->decrypt, &key, &kt, DO_DECRYPT,
		    "Incoming Control Channel Authentication");

      CLEAR (key);
    }
  else
    {
      CLEAR (*ctx);
    }
}
#endif

/* header and footer for static key file */
static const char static_key_head[] = "-----BEGIN OpenVPN Static key V1-----";
static const char static_key_foot[] = "-----END OpenVPN Static key V1-----";

static const char printable_char_fmt[] =
  "Non-Hex character ('%c') found at line %d in key file %s (%d/%d bytes found/required)";

static const char unprintable_char_fmt[] =
  "Non-Hex, unprintable character (0x%02x) found at line %d in key file %s (%d/%d bytes found/required)";

/* read key from file */
void
read_key_file (struct key *key, const char *filename)
{
  const int gc_level = gc_new_level ();
  struct buffer in = alloc_buf_gc (512);
  int state = 0;
  uint8_t* out = (uint8_t*) key;
  int count = 0;
  uint8_t hex_byte[3] = {0, 0, 0};
  int hb_index = 0;
  int line_num = 1;
  int line_index = 0;
  int matchlen = 0;
  const int headlen = strlen(static_key_head);
  const int keylen = sizeof (*key);
  int fd, size;

  fd = open (filename, O_RDONLY);
  if (fd == -1)
    msg (M_ERR, "Cannot open shared secret file %s", filename);

  while (size = read (fd, in.data, in.capacity))
    {
      const char *cp = in.data;
      while (size)
	{
	  const char c = *cp;

	  /* msg (M_INFO, "char='%c' state=%d line_num=%d line_index=%d matchlen=%d",
	     c, state, line_num, line_index, matchlen); */

	  if (c == '\n')
	    {
	      line_index = 0;
	      ++line_num;
	    }
	  else
	    {
	      /* found header line? */
	      if (state == 0 && !line_index)
		{
		  if (matchlen == headlen)
		    state = 1;
		  matchlen = 0;
		}

	      /* compare read chars with header line */
	      if (state == 0) {
		if (line_index < headlen && c == static_key_head[line_index])
		  ++matchlen;
	      }

	      /* reading key */
	      if (state == 1) {
		if (isxdigit(c))
		  {
		    ASSERT(hb_index < 2);
		    hex_byte[hb_index++] = c;
		    if (hb_index == 2)
		      {
			unsigned int u;
			ASSERT(sscanf(hex_byte, "%x", &u) == 1);
			*out++ = u;
			hb_index = 0;
			if (++count == keylen)
			  state = 2;
		      }
		  }
		else if (isspace(c))
		  ;
		else
		  {
		    msg (M_FATAL,
			 (isprint (c) ? printable_char_fmt : unprintable_char_fmt),
			 c, line_num, filename, count, keylen);
		  }
	      }
	      ++line_index;
	    }
	  ++cp;
	  --size;
	}
    }

  close (fd);
  if (state != 2)
    msg (M_ERR, "Key not found in file %s (%d/%d bytes found/required)",
	 filename, count, keylen);

  /* zero file read buffer */
  memset(in.data, 0, in.capacity);

  warn_if_group_others_accessible (filename);

  /* pop our garbage collection level */
  gc_free_level (gc_level);
}

/* write key to file */
void
write_key_file (const struct key *key, const char *filename)
{
  int fd, size, len;
  char* fmt;
  const int gc_level = gc_new_level ();
  struct buffer out = alloc_buf_gc (512);

  /* open key file */
  fd = open (filename, O_CREAT | O_TRUNC | O_WRONLY, S_IRWXU);
  if (fd == -1)
    msg (M_ERR, "Cannot open shared secret file %s for write", filename);

  /* format key as ascii */
  fmt = format_hex_ex ((const uint8_t*)key, sizeof (*key), 0, 8, "\n");
  buf_printf (&out, "%s\n", static_key_head);
  buf_printf (&out, "%s\n", fmt);
  buf_printf (&out, "%s\n", static_key_foot);

  /* write data to file */
  len = strlen (BPTR(&out));
  size = write (fd, BPTR(&out), len);
  if (size != len)
    msg (M_ERR, "Write error on shared secret file %s", filename);
  if (close (fd))
    msg (M_ERR, "Close error on shared secret file %s", filename);

  /* zero memory that held keys (memory will be freed by garbage collector) */
  memset (BPTR(&out), 0, len);
  memset (fmt, 0, strlen(fmt));

  /* pop our garbage collection level */
  gc_free_level (gc_level);
}

/* given a key and key_type, write key to buffer */
void
write_key (const struct key *key, const struct key_type *kt,
	   struct buffer *buf)
{
  ASSERT (kt->cipher_length <= MAX_CIPHER_KEY_LENGTH
	  && kt->hmac_length <= MAX_HMAC_KEY_LENGTH);
  ASSERT (buf_write (buf, &kt->cipher_length, 1));
  ASSERT (buf_write (buf, &kt->hmac_length, 1));
  ASSERT (buf_write (buf, key->cipher, kt->cipher_length));
  ASSERT (buf_write (buf, key->hmac, kt->hmac_length));
}

/*
 * Given a key_type and buffer, read key from buffer.
 * Return: 1 on success
 *        -1 read failure
 *         0 on key length mismatch 
 */
int
read_key (struct key *key, const struct key_type *kt, struct buffer *buf)
{
  uint8_t cipher_length;
  uint8_t hmac_length;

  CLEAR (*key);
  if (!buf_read (buf, &cipher_length, 1))
    goto read_err;
  if (!buf_read (buf, &hmac_length, 1))
    goto read_err;

  if (!buf_read (buf, key->cipher, cipher_length))
    goto read_err;
  if (!buf_read (buf, key->hmac, hmac_length))
    goto read_err;

  if (cipher_length != kt->cipher_length || hmac_length != kt->hmac_length)
    goto key_len_err;

  return 1;

read_err:
  msg (D_TLS_ERRORS, "TLS Error: error reading key from remote");
  return -1;

key_len_err:
  msg (D_TLS_ERRORS,
       "TLS Error: key length mismatch, local cipher/hmac %d/%d, remote cipher/hmac %d/%d",
       kt->cipher_length, kt->hmac_length, cipher_length, hmac_length);
  return 0;
}

void
show_available_ciphers ()
{
  int nid;

  printf ("The following ciphers and cipher modes are available\n"
	  "for use with OpenVPN.  Each cipher shown below may be\n"
	  "used as a parameter to the --cipher option.  The default\n"
	  "key size is shown as well as whether or not it can be\n"
          "changed with the --keysize directive.  Using a CBC mode\n"
	  "is recommended.\n\n");

  for (nid = 0; nid < 10000; ++nid)	/* is there a better way to get the size of the nid list? */
    {
      const EVP_CIPHER *cipher = EVP_get_cipherbynid (nid);
      if (cipher && cipher_ok (OBJ_nid2sn (nid)))
	{
	  const unsigned int mode = EVP_CIPHER_mode (cipher);
	  if (mode == EVP_CIPH_CBC_MODE || mode == EVP_CIPH_CFB_MODE || mode == EVP_CIPH_OFB_MODE)
	    printf ("%s %d bit default key (%s)\n",
		    OBJ_nid2sn (nid),
		    EVP_CIPHER_key_length (cipher) * 8,
		    ((EVP_CIPHER_flags (cipher) & EVP_CIPH_VARIABLE_LENGTH) ?
		     "variable" : "fixed"));
	}
    }
  printf ("\n");
}

void
show_available_digests ()
{
  int nid;

  printf ("The following message digests are available for use with\n"
	  "OpenVPN.  A message digest is used in conjunction with\n"
	  "the HMAC function, to authenticate received packets.\n"
	  "You can specify a message digest as parameter to\n"
	  "the --auth option.\n\n");

  for (nid = 0; nid < 10000; ++nid)
    {
      const EVP_MD *digest = EVP_get_digestbynid (nid);
      if (digest)
	{
	  printf ("%s %d bit digest size\n",
		  OBJ_nid2sn (nid), EVP_MD_size (digest) * 8);
	}
    }
  printf ("\n");
}

/*
 * This routine should have additional OpenSSL crypto library initialisations
 * used by both crypto and ssl components of OpenVPN.
 */
void init_crypto_lib ()
{
}

#ifndef USE_SSL

void
init_ssl_lib ()
{
  ERR_load_crypto_strings ();
  OpenSSL_add_all_algorithms ();
  init_crypto_lib();
}

void
free_ssl_lib ()
{
  EVP_cleanup ();
  ERR_free_strings ();
}

#endif /* USE_SSL */
#endif /* USE_CRYPTO */