doc/man3/d2i_X509.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 d2i_ACCESS_DESCRIPTION,
   6 d2i_ASIdOrRange,
   7 d2i_ASIdentifierChoice,
   8 d2i_ASIdentifiers,
   9 d2i_ASN1_BIT_STRING,
  10 d2i_ASN1_BMPSTRING,
  11 d2i_ASN1_ENUMERATED,
  12 d2i_ASN1_GENERALIZEDTIME,
  13 d2i_ASN1_GENERALSTRING,
  14 d2i_ASN1_IA5STRING,
  15 d2i_ASN1_INTEGER,
  16 d2i_ASN1_NULL,
  17 d2i_ASN1_OBJECT,
  18 d2i_ASN1_OCTET_STRING,
  19 d2i_ASN1_PRINTABLE,
  20 d2i_ASN1_PRINTABLESTRING,
  21 d2i_ASN1_SEQUENCE_ANY,
  22 d2i_ASN1_SET_ANY,
  23 d2i_ASN1_T61STRING,
  24 d2i_ASN1_TIME,
  25 d2i_ASN1_TYPE,
  26 d2i_ASN1_UINTEGER,
  27 d2i_ASN1_UNIVERSALSTRING,
  28 d2i_ASN1_UTCTIME,
  29 d2i_ASN1_UTF8STRING,
  30 d2i_ASN1_VISIBLESTRING,
  31 d2i_ASRange,
  32 d2i_AUTHORITY_INFO_ACCESS,
  33 d2i_AUTHORITY_KEYID,
  34 d2i_BASIC_CONSTRAINTS,
  35 d2i_CERTIFICATEPOLICIES,
  36 d2i_CMS_ContentInfo,
  37 d2i_CMS_ReceiptRequest,
  38 d2i_CMS_bio,
  39 d2i_CRL_DIST_POINTS,
  40 d2i_DHxparams,
  41 d2i_DIRECTORYSTRING,
  42 d2i_DISPLAYTEXT,
  43 d2i_DIST_POINT,
  44 d2i_DIST_POINT_NAME,
  45 d2i_DSAPrivateKey,
  46 d2i_DSAPrivateKey_bio,
  47 d2i_DSAPrivateKey_fp,
  48 d2i_DSAPublicKey,
  49 d2i_DSA_PUBKEY_bio,
  50 d2i_DSA_PUBKEY_fp,
  51 d2i_DSA_SIG,
  52 d2i_DSAparams,
  53 d2i_ECPKParameters,
  54 d2i_ECParameters,
  55 d2i_ECPrivateKey,
  56 d2i_ECPrivateKey_bio,
  57 d2i_ECPrivateKey_fp,
  58 d2i_EC_PUBKEY,
  59 d2i_EC_PUBKEY_bio,
  60 d2i_EC_PUBKEY_fp,
  61 d2i_EDIPARTYNAME,
  62 d2i_ESS_CERT_ID,
  63 d2i_ESS_ISSUER_SERIAL,
  64 d2i_ESS_SIGNING_CERT,
  65 d2i_EXTENDED_KEY_USAGE,
  66 d2i_GENERAL_NAME,
  67 d2i_GENERAL_NAMES,
  68 d2i_IPAddressChoice,
  69 d2i_IPAddressFamily,
  70 d2i_IPAddressOrRange,
  71 d2i_IPAddressRange,
  72 d2i_ISSUING_DIST_POINT,
  73 d2i_NETSCAPE_CERT_SEQUENCE,
  74 d2i_NETSCAPE_SPKAC,
  75 d2i_NETSCAPE_SPKI,
  76 d2i_NOTICEREF,
  77 d2i_OCSP_BASICRESP,
  78 d2i_OCSP_CERTID,
  79 d2i_OCSP_CERTSTATUS,
  80 d2i_OCSP_CRLID,
  81 d2i_OCSP_ONEREQ,
  82 d2i_OCSP_REQINFO,
  83 d2i_OCSP_REQUEST,
  84 d2i_OCSP_RESPBYTES,
  85 d2i_OCSP_RESPDATA,
  86 d2i_OCSP_RESPID,
  87 d2i_OCSP_RESPONSE,
  88 d2i_OCSP_REVOKEDINFO,
  89 d2i_OCSP_SERVICELOC,
  90 d2i_OCSP_SIGNATURE,
  91 d2i_OCSP_SINGLERESP,
  92 d2i_OTHERNAME,
  93 d2i_PBE2PARAM,
  94 d2i_PBEPARAM,
  95 d2i_PBKDF2PARAM,
  96 d2i_PKCS12,
  97 d2i_PKCS12_BAGS,
  98 d2i_PKCS12_MAC_DATA,
  99 d2i_PKCS12_SAFEBAG,
 100 d2i_PKCS12_bio,
 101 d2i_PKCS12_fp,
 102 d2i_PKCS7,
 103 d2i_PKCS7_DIGEST,
 104 d2i_PKCS7_ENCRYPT,
 105 d2i_PKCS7_ENC_CONTENT,
 106 d2i_PKCS7_ENVELOPE,
 107 d2i_PKCS7_ISSUER_AND_SERIAL,
 108 d2i_PKCS7_RECIP_INFO,
 109 d2i_PKCS7_SIGNED,
 110 d2i_PKCS7_SIGNER_INFO,
 111 d2i_PKCS7_SIGN_ENVELOPE,
 112 d2i_PKCS7_bio,
 113 d2i_PKCS7_fp,
 114 d2i_PKCS8_PRIV_KEY_INFO,
 115 d2i_PKCS8_PRIV_KEY_INFO_bio,
 116 d2i_PKCS8_PRIV_KEY_INFO_fp,
 117 d2i_PKCS8_bio,
 118 d2i_PKCS8_fp,
 119 d2i_PKEY_USAGE_PERIOD,
 120 d2i_POLICYINFO,
 121 d2i_POLICYQUALINFO,
 122 d2i_PROXY_CERT_INFO_EXTENSION,
 123 d2i_PROXY_POLICY,
 124 d2i_PublicKey,
 125 d2i_RSAPrivateKey,
 126 d2i_RSAPrivateKey_bio,
 127 d2i_RSAPrivateKey_fp,
 128 d2i_RSAPublicKey,
 129 d2i_RSAPublicKey_bio,
 130 d2i_RSAPublicKey_fp,
 131 d2i_RSA_OAEP_PARAMS,
 132 d2i_RSA_PSS_PARAMS,
 133 d2i_RSA_PUBKEY,
 134 d2i_RSA_PUBKEY_bio,
 135 d2i_RSA_PUBKEY_fp,
 136 d2i_SCRYPT_PARAMS,
 137 d2i_SCT_LIST,
 138 d2i_SXNET,
 139 d2i_SXNETID,
 140 d2i_TS_ACCURACY,
 141 d2i_TS_MSG_IMPRINT,
 142 d2i_TS_MSG_IMPRINT_bio,
 143 d2i_TS_MSG_IMPRINT_fp,
 144 d2i_TS_REQ,
 145 d2i_TS_REQ_bio,
 146 d2i_TS_REQ_fp,
 147 d2i_TS_RESP,
 148 d2i_TS_RESP_bio,
 149 d2i_TS_RESP_fp,
 150 d2i_TS_STATUS_INFO,
 151 d2i_TS_TST_INFO,
 152 d2i_TS_TST_INFO_bio,
 153 d2i_TS_TST_INFO_fp,
 154 d2i_USERNOTICE,
 155 d2i_X509,
 156 d2i_X509_ALGOR,
 157 d2i_X509_ALGORS,
 158 d2i_X509_ATTRIBUTE,
 159 d2i_X509_CERT_AUX,
 160 d2i_X509_CINF,
 161 d2i_X509_CRL,
 162 d2i_X509_CRL_INFO,
 163 d2i_X509_CRL_bio,
 164 d2i_X509_CRL_fp,
 165 d2i_X509_EXTENSION,
 166 d2i_X509_EXTENSIONS,
 167 d2i_X509_NAME,
 168 d2i_X509_NAME_ENTRY,
 169 d2i_X509_PUBKEY,
 170 d2i_X509_REQ,
 171 d2i_X509_REQ_INFO,
 172 d2i_X509_REQ_bio,
 173 d2i_X509_REQ_fp,
 174 d2i_X509_REVOKED,
 175 d2i_X509_SIG,
 176 d2i_X509_VAL,
 177 i2d_ACCESS_DESCRIPTION,
 178 i2d_ASIdOrRange,
 179 i2d_ASIdentifierChoice,
 180 i2d_ASIdentifiers,
 181 i2d_ASN1_BIT_STRING,
 182 i2d_ASN1_BMPSTRING,
 183 i2d_ASN1_ENUMERATED,
 184 i2d_ASN1_GENERALIZEDTIME,
 185 i2d_ASN1_GENERALSTRING,
 186 i2d_ASN1_IA5STRING,
 187 i2d_ASN1_INTEGER,
 188 i2d_ASN1_NULL,
 189 i2d_ASN1_OBJECT,
 190 i2d_ASN1_OCTET_STRING,
 191 i2d_ASN1_PRINTABLE,
 192 i2d_ASN1_PRINTABLESTRING,
 193 i2d_ASN1_SEQUENCE_ANY,
 194 i2d_ASN1_SET_ANY,
 195 i2d_ASN1_T61STRING,
 196 i2d_ASN1_TIME,
 197 i2d_ASN1_TYPE,
 198 i2d_ASN1_UNIVERSALSTRING,
 199 i2d_ASN1_UTCTIME,
 200 i2d_ASN1_UTF8STRING,
 201 i2d_ASN1_VISIBLESTRING,
 202 i2d_ASN1_bio_stream,
 203 i2d_ASRange,
 204 i2d_AUTHORITY_INFO_ACCESS,
 205 i2d_AUTHORITY_KEYID,
 206 i2d_BASIC_CONSTRAINTS,
 207 i2d_CERTIFICATEPOLICIES,
 208 i2d_CMS_ContentInfo,
 209 i2d_CMS_ReceiptRequest,
 210 i2d_CMS_bio,
 211 i2d_CRL_DIST_POINTS,
 212 i2d_DHxparams,
 213 i2d_DIRECTORYSTRING,
 214 i2d_DISPLAYTEXT,
 215 i2d_DIST_POINT,
 216 i2d_DIST_POINT_NAME,
 217 i2d_DSAPrivateKey,
 218 i2d_DSAPrivateKey_bio,
 219 i2d_DSAPrivateKey_fp,
 220 i2d_DSAPublicKey,
 221 i2d_DSA_PUBKEY_bio,
 222 i2d_DSA_PUBKEY_fp,
 223 i2d_DSA_SIG,
 224 i2d_DSAparams,
 225 i2d_ECPKParameters,
 226 i2d_ECParameters,
 227 i2d_ECPrivateKey,
 228 i2d_ECPrivateKey_bio,
 229 i2d_ECPrivateKey_fp,
 230 i2d_EC_PUBKEY,
 231 i2d_EC_PUBKEY_bio,
 232 i2d_EC_PUBKEY_fp,
 233 i2d_EDIPARTYNAME,
 234 i2d_ESS_CERT_ID,
 235 i2d_ESS_ISSUER_SERIAL,
 236 i2d_ESS_SIGNING_CERT,
 237 i2d_EXTENDED_KEY_USAGE,
 238 i2d_GENERAL_NAME,
 239 i2d_GENERAL_NAMES,
 240 i2d_IPAddressChoice,
 241 i2d_IPAddressFamily,
 242 i2d_IPAddressOrRange,
 243 i2d_IPAddressRange,
 244 i2d_ISSUING_DIST_POINT,
 245 i2d_NETSCAPE_CERT_SEQUENCE,
 246 i2d_NETSCAPE_SPKAC,
 247 i2d_NETSCAPE_SPKI,
 248 i2d_NOTICEREF,
 249 i2d_OCSP_BASICRESP,
 250 i2d_OCSP_CERTID,
 251 i2d_OCSP_CERTSTATUS,
 252 i2d_OCSP_CRLID,
 253 i2d_OCSP_ONEREQ,
 254 i2d_OCSP_REQINFO,
 255 i2d_OCSP_REQUEST,
 256 i2d_OCSP_RESPBYTES,
 257 i2d_OCSP_RESPDATA,
 258 i2d_OCSP_RESPID,
 259 i2d_OCSP_RESPONSE,
 260 i2d_OCSP_REVOKEDINFO,
 261 i2d_OCSP_SERVICELOC,
 262 i2d_OCSP_SIGNATURE,
 263 i2d_OCSP_SINGLERESP,
 264 i2d_OTHERNAME,
 265 i2d_PBE2PARAM,
 266 i2d_PBEPARAM,
 267 i2d_PBKDF2PARAM,
 268 i2d_PKCS12,
 269 i2d_PKCS12_BAGS,
 270 i2d_PKCS12_MAC_DATA,
 271 i2d_PKCS12_SAFEBAG,
 272 i2d_PKCS12_bio,
 273 i2d_PKCS12_fp,
 274 i2d_PKCS7,
 275 i2d_PKCS7_DIGEST,
 276 i2d_PKCS7_ENCRYPT,
 277 i2d_PKCS7_ENC_CONTENT,
 278 i2d_PKCS7_ENVELOPE,
 279 i2d_PKCS7_ISSUER_AND_SERIAL,
 280 i2d_PKCS7_NDEF,
 281 i2d_PKCS7_RECIP_INFO,
 282 i2d_PKCS7_SIGNED,
 283 i2d_PKCS7_SIGNER_INFO,
 284 i2d_PKCS7_SIGN_ENVELOPE,
 285 i2d_PKCS7_bio,
 286 i2d_PKCS7_fp,
 287 i2d_PKCS8PrivateKeyInfo_bio,
 288 i2d_PKCS8PrivateKeyInfo_fp,
 289 i2d_PKCS8_PRIV_KEY_INFO,
 290 i2d_PKCS8_PRIV_KEY_INFO_bio,
 291 i2d_PKCS8_PRIV_KEY_INFO_fp,
 292 i2d_PKCS8_bio,
 293 i2d_PKCS8_fp,
 294 i2d_PKEY_USAGE_PERIOD,
 295 i2d_POLICYINFO,
 296 i2d_POLICYQUALINFO,
 297 i2d_PROXY_CERT_INFO_EXTENSION,
 298 i2d_PROXY_POLICY,
 299 i2d_PublicKey,
 300 i2d_RSAPrivateKey,
 301 i2d_RSAPrivateKey_bio,
 302 i2d_RSAPrivateKey_fp,
 303 i2d_RSAPublicKey,
 304 i2d_RSAPublicKey_bio,
 305 i2d_RSAPublicKey_fp,
 306 i2d_RSA_OAEP_PARAMS,
 307 i2d_RSA_PSS_PARAMS,
 308 i2d_RSA_PUBKEY,
 309 i2d_RSA_PUBKEY_bio,
 310 i2d_RSA_PUBKEY_fp,
 311 i2d_SCRYPT_PARAMS,
 312 i2d_SCT_LIST,
 313 i2d_SXNET,
 314 i2d_SXNETID,
 315 i2d_TS_ACCURACY,
 316 i2d_TS_MSG_IMPRINT,
 317 i2d_TS_MSG_IMPRINT_bio,
 318 i2d_TS_MSG_IMPRINT_fp,
 319 i2d_TS_REQ,
 320 i2d_TS_REQ_bio,
 321 i2d_TS_REQ_fp,
 322 i2d_TS_RESP,
 323 i2d_TS_RESP_bio,
 324 i2d_TS_RESP_fp,
 325 i2d_TS_STATUS_INFO,
 326 i2d_TS_TST_INFO,
 327 i2d_TS_TST_INFO_bio,
 328 i2d_TS_TST_INFO_fp,
 329 i2d_USERNOTICE,
 330 i2d_X509,
 331 i2d_X509_ALGOR,
 332 i2d_X509_ALGORS,
 333 i2d_X509_ATTRIBUTE,
 334 i2d_X509_CERT_AUX,
 335 i2d_X509_CINF,
 336 i2d_X509_CRL,
 337 i2d_X509_CRL_INFO,
 338 i2d_X509_CRL_bio,
 339 i2d_X509_CRL_fp,
 340 i2d_X509_EXTENSION,
 341 i2d_X509_EXTENSIONS,
 342 i2d_X509_NAME,
 343 i2d_X509_NAME_ENTRY,
 344 i2d_X509_PUBKEY,
 345 i2d_X509_REQ,
 346 i2d_X509_REQ_INFO,
 347 i2d_X509_REQ_bio,
 348 i2d_X509_REQ_fp,
 349 i2d_X509_REVOKED,
 350 i2d_X509_SIG,
 351 i2d_X509_VAL,
 352 - convert objects from/to ASN.1/DER representation
 353
 354 =head1 SYNOPSIS
 355
 356 =for comment generic
 357
 358  TYPE *d2i_TYPE(TYPE **a, unsigned char **pp, long length);
 359  TYPE *d2i_TYPE_bio(BIO *bp, TYPE **a);
 360  TYPE *d2i_TYPE_fp(FILE *fp, TYPE **a);
 361
 362  int i2d_TYPE(TYPE *a, unsigned char **pp);
 363  int i2d_TYPE_fp(FILE *fp, TYPE *a);
 364  int i2d_TYPE_bio(BIO *bp, TYPE *a);
 365
 366 =head1 DESCRIPTION
 367
 368 In the description here, I<TYPE> is used a placeholder
 369 for any of the OpenSSL datatypes, such as I<X509_CRL>.
 370
 371 These functions convert OpenSSL objects to and from their ASN.1/DER
 372 encoding.  Unlike the C structures which can have pointers to sub-objects
 373 within, the DER is a serialized encoding, suitable for sending over the
 374 network, writing to a file, and so on.
 375
 376 d2i_TYPE() attempts to decode B<len> bytes at B<*in>. If successful a
 377 pointer to the B<TYPE> structure is returned and B<*in> is incremented to
 378 the byte following the parsed data.  If B<a> is not B<NULL> then a pointer
 379 to the returned structure is also written to B<*a>.  If an error occurred
 380 then B<NULL> is returned.
 381
 382 On a successful return, if B<*a> is not B<NULL> then it is assumed that B<*a>
 383 contains a valid B<TYPE> structure and an attempt is made to reuse it. This
 384 "reuse" capability is present for historical compatibility but its use is
 385 B<strongly discouraged> (see BUGS below, and the discussion in the RETURN
 386 VALUES section).
 387
 388 d2i_TYPE_bio() is similar to d2i_TYPE() except it attempts
 389 to parse data from BIO B<bp>.
 390
 391 d2i_TYPE_fp() is similar to d2i_TYPE() except it attempts
 392 to parse data from FILE pointer B<fp>.
 393
 394 i2d_TYPE() encodes the structure pointed to by B<a> into DER format.
 395 If B<out> is not B<NULL>, it writes the DER encoded data to the buffer
 396 at B<*out>, and increments it to point after the data just written.
 397 If the return value is negative an error occurred, otherwise it
 398 returns the length of the encoded data.
 399
 400 If B<*out> is B<NULL> memory will be allocated for a buffer and the encoded
 401 data written to it. In this case B<*out> is not incremented and it points
 402 to the start of the data just written.
 403
 404 i2d_TYPE_bio() is similar to i2d_TYPE() except it writes
 405 the encoding of the structure B<a> to BIO B<bp> and it
 406 returns 1 for success and 0 for failure.
 407
 408 i2d_TYPE_fp() is similar to i2d_TYPE() except it writes
 409 the encoding of the structure B<a> to BIO B<bp> and it
 410 returns 1 for success and 0 for failure.
 411
 412 These routines do not encrypt private keys and therefore offer no
 413 security; use L<PEM_write_PrivateKey(3)> or similar for writing to files.
 414
 415 =head1 NOTES
 416
 417 The letters B<i> and B<d> in B<i2d_TYPE> stand for
 418 "internal" (that is, an internal C structure) and "DER" respectively.
 419 So B<i2d_TYPE> converts from internal to DER.
 420
 421 The functions can also understand B<BER> forms.
 422
 423 The actual TYPE structure passed to i2d_TYPE() must be a valid
 424 populated B<TYPE> structure -- it B<cannot> simply be fed with an
 425 empty structure such as that returned by TYPE_new().
 426
 427 The encoded data is in binary form and may contain embedded zeroes.
 428 Therefore any FILE pointers or BIOs should be opened in binary mode.
 429 Functions such as strlen() will B<not> return the correct length
 430 of the encoded structure.
 431
 432 The ways that B<*in> and B<*out> are incremented after the operation
 433 can trap the unwary. See the B<WARNINGS> section for some common
 434 errors.
 435 The reason for this-auto increment behaviour is to reflect a typical
 436 usage of ASN1 functions: after one structure is encoded or decoded
 437 another will be processed after it.
 438
 439 The following points about the data types might be useful:
 440
 441 =over 4
 442
 443 =item B<ASN1_OBJECT>
 444
 445 Represents an ASN1 OBJECT IDENTIFIER.
 446
 447 =item B<DHparams>
 448
 449 Represents a PKCS#3 DH parameters structure.
 450
 451 =item B<DHparamx>
 452
 453 Represents a ANSI X9.42 DH parameters structure.
 454
 455 =item B<DSA_PUBKEY>
 456
 457 Represents a DSA public key using a B<SubjectPublicKeyInfo> structure.
 458
 459 =item B<DSAPublicKey, DSAPrivateKey>
 460
 461 Use a non-standard OpenSSL format and should be avoided; use B<DSA_PUBKEY>,
 462 B<PEM_write_PrivateKey(3)>, or similar instead.
 463
 464 =item B<RSAPublicKey>
 465
 466 Represents a PKCS#1 RSA public key structure.
 467
 468 =item B<X509_ALGOR>
 469
 470 Represents an B<AlgorithmIdentifier> structure as used in IETF RFC 6960 and
 471 elsewhere.
 472
 473 =item B<X509_Name>
 474
 475 Represents a B<Name> type as used for subject and issuer names in
 476 IETF RFC 6960 and elsewhere.
 477
 478 =item B<X509_REQ>
 479
 480 Represents a PKCS#10 certificate request.
 481
 482 =item B<X509_SIG>
 483
 484 Represents the B<DigestInfo> structure defined in PKCS#1 and PKCS#7.
 485
 486 =back
 487
 488 =head1 EXAMPLES
 489
 490 Allocate and encode the DER encoding of an X509 structure:
 491
 492  int len;
 493  unsigned char *buf;
 494
 495  buf = NULL;
 496  len = i2d_X509(x, &buf);
 497  if (len < 0)
 498      /* error */
 499
 500 Attempt to decode a buffer:
 501
 502  X509 *x;
 503  unsigned char *buf, *p;
 504  int len;
 505
 506  /* Set up buf and len to point to the input buffer. */
 507  p = buf;
 508  x = d2i_X509(NULL, &p, len);
 509  if (x == NULL)
 510      /* error */
 511
 512 Alternative technique:
 513
 514  X509 *x;
 515  unsigned char *buf, *p;
 516  int len;
 517
 518  /* Set up buf and len to point to the input buffer. */
 519  p = buf;
 520  x = NULL;
 521
 522  if (d2i_X509(&x, &p, len) == NULL)
 523      /* error */
 524
 525 =head1 WARNINGS
 526
 527 Using a temporary variable is mandatory. A common
 528 mistake is to attempt to use a buffer directly as follows:
 529
 530  int len;
 531  unsigned char *buf;
 532
 533  len = i2d_X509(x, NULL);
 534  buf = OPENSSL_malloc(len);
 535  ...
 536  i2d_X509(x, &buf);
 537  ...
 538  OPENSSL_free(buf);
 539
 540 This code will result in B<buf> apparently containing garbage because
 541 it was incremented after the call to point after the data just written.
 542 Also B<buf> will no longer contain the pointer allocated by OPENSSL_malloc()
 543 and the subsequent call to OPENSSL_free() is likely to crash.
 544
 545 Another trap to avoid is misuse of the B<a> argument to d2i_TYPE():
 546
 547  X509 *x;
 548
 549  if (d2i_X509(&x, &p, len) == NULL)
 550      /* error */
 551
 552 This will probably crash somewhere in d2i_X509(). The reason for this
 553 is that the variable B<x> is uninitialized and an attempt will be made to
 554 interpret its (invalid) value as an B<X509> structure, typically causing
 555 a segmentation violation. If B<x> is set to NULL first then this will not
 556 happen.
 557
 558 =head1 BUGS
 559
 560 In some versions of OpenSSL the "reuse" behaviour of d2i_TYPE() when
 561 B<*px> is valid is broken and some parts of the reused structure may
 562 persist if they are not present in the new one. As a result the use
 563 of this "reuse" behaviour is strongly discouraged.
 564
 565 i2d_TYPE() will not return an error in many versions of OpenSSL,
 566 if mandatory fields are not initialized due to a programming error
 567 then the encoded structure may contain invalid data or omit the
 568 fields entirely and will not be parsed by d2i_TYPE(). This may be
 569 fixed in future so code should not assume that i2d_TYPE() will
 570 always succeed.
 571
 572 Any function which encodes a structure (i2d_TYPE(),
 573 i2d_TYPE() or i2d_TYPE()) may return a stale encoding if the
 574 structure has been modified after deserialization or previous
 575 serialization. This is because some objects cache the encoding for
 576 efficiency reasons.
 577
 578 =head1 RETURN VALUES
 579
 580 d2i_TYPE(), d2i_TYPE_bio() and d2i_TYPE_fp() return a valid B<TYPE> structure
 581 or B<NULL> if an error occurs.  If the "reuse" capability has been used with
 582 a valid structure being passed in via B<a>, then the object is not freed in
 583 the event of error but may be in a potentially invalid or inconsistent state.
 584
 585 i2d_TYPE() returns the number of bytes successfully encoded or a negative
 586 value if an error occurs.
 587
 588 i2d_TYPE_bio() and i2d_TYPE_fp() return 1 for success and 0 if an error
 589 occurs.
 590
 591 =head1 COPYRIGHT
 592
 593 Copyright 1998-2016 The OpenSSL Project Authors. All Rights Reserved.
 594
 595 Licensed under the OpenSSL license (the "License").  You may not use
 596 this file except in compliance with the License.  You can obtain a copy
 597 in the file LICENSE in the source distribution or at
 598 L<https://www.openssl.org/source/license.html>.
 599
 600 =cut