d2i_ACCESS_DESCRIPTION, d2i_ADMISSIONS, d2i_ADMISSION_SYNTAX, d2i_ASIdOrRange,
  d2i_ASIdentifierChoice, d2i_ASIdentifiers, d2i_ASN1_BIT_STRING,
  d2i_ASN1_BMPSTRING, d2i_ASN1_ENUMERATED, d2i_ASN1_GENERALIZEDTIME,
  d2i_ASN1_GENERALSTRING, d2i_ASN1_IA5STRING, d2i_ASN1_INTEGER, d2i_ASN1_NULL,
  d2i_ASN1_OBJECT, d2i_ASN1_OCTET_STRING, d2i_ASN1_PRINTABLE,
  d2i_ASN1_PRINTABLESTRING, d2i_ASN1_SEQUENCE_ANY, d2i_ASN1_SET_ANY,
  d2i_ASN1_T61STRING, d2i_ASN1_TIME, d2i_ASN1_TYPE, d2i_ASN1_UINTEGER,
  d2i_ASN1_UNIVERSALSTRING, d2i_ASN1_UTCTIME, d2i_ASN1_UTF8STRING,
  d2i_ASN1_VISIBLESTRING, d2i_ASRange, d2i_AUTHORITY_INFO_ACCESS,
  d2i_AUTHORITY_KEYID, d2i_BASIC_CONSTRAINTS, d2i_CERTIFICATEPOLICIES,
  d2i_CMS_ContentInfo, d2i_CMS_ReceiptRequest, d2i_CMS_bio, d2i_CRL_DIST_POINTS,
  d2i_DHxparams, d2i_DIRECTORYSTRING, d2i_DISPLAYTEXT, d2i_DIST_POINT,
  d2i_DIST_POINT_NAME, d2i_DSA_SIG, d2i_ECDSA_SIG, d2i_ECPKParameters,
  d2i_EDIPARTYNAME, d2i_ESS_CERT_ID, d2i_ESS_CERT_ID_V2, d2i_ESS_ISSUER_SERIAL,
  d2i_ESS_SIGNING_CERT, d2i_ESS_SIGNING_CERT_V2, d2i_EXTENDED_KEY_USAGE,
  d2i_GENERAL_NAME, d2i_GENERAL_NAMES, d2i_IPAddressChoice, d2i_IPAddressFamily,
  d2i_IPAddressOrRange, d2i_IPAddressRange, d2i_ISSUER_SIGN_TOOL,
  d2i_ISSUING_DIST_POINT, d2i_NAMING_AUTHORITY, d2i_NETSCAPE_CERT_SEQUENCE,
  d2i_NETSCAPE_SPKAC, d2i_NETSCAPE_SPKI, d2i_NOTICEREF, d2i_OCSP_BASICRESP,
  d2i_OCSP_CERTID, d2i_OCSP_CERTSTATUS, d2i_OCSP_CRLID, d2i_OCSP_ONEREQ,
  d2i_OCSP_REQINFO, d2i_OCSP_REQUEST, d2i_OCSP_RESPBYTES, d2i_OCSP_RESPDATA,
  d2i_OCSP_RESPID, d2i_OCSP_RESPONSE, d2i_OCSP_REVOKEDINFO, d2i_OCSP_SERVICELOC,
  d2i_OCSP_SIGNATURE, d2i_OCSP_SINGLERESP, d2i_OSSL_CMP_MSG,
  d2i_OSSL_CMP_PKIHEADER, d2i_OSSL_CMP_PKISI, d2i_OSSL_CRMF_CERTID,
  d2i_OSSL_CRMF_CERTTEMPLATE, d2i_OSSL_CRMF_ENCRYPTEDVALUE, d2i_OSSL_CRMF_MSG,
  d2i_OSSL_CRMF_MSGS, d2i_OSSL_CRMF_PBMPARAMETER,
  d2i_OSSL_CRMF_PKIPUBLICATIONINFO, d2i_OSSL_CRMF_SINGLEPUBINFO, d2i_OTHERNAME,
  d2i_PBE2PARAM, d2i_PBEPARAM, d2i_PBKDF2PARAM, d2i_PKCS12, d2i_PKCS12_BAGS,
  d2i_PKCS12_MAC_DATA, d2i_PKCS12_SAFEBAG, d2i_PKCS12_bio, d2i_PKCS12_fp,
  d2i_PKCS7, d2i_PKCS7_DIGEST, d2i_PKCS7_ENCRYPT, d2i_PKCS7_ENC_CONTENT,
  d2i_PKCS7_ENVELOPE, d2i_PKCS7_ISSUER_AND_SERIAL, d2i_PKCS7_RECIP_INFO,
  d2i_PKCS7_SIGNED, d2i_PKCS7_SIGNER_INFO, d2i_PKCS7_SIGN_ENVELOPE,
  d2i_PKCS7_bio, d2i_PKCS7_fp, d2i_PKCS8_PRIV_KEY_INFO,
  d2i_PKCS8_PRIV_KEY_INFO_bio, d2i_PKCS8_PRIV_KEY_INFO_fp, d2i_PKCS8_bio,
  d2i_PKCS8_fp, d2i_PKEY_USAGE_PERIOD, d2i_POLICYINFO, d2i_POLICYQUALINFO,
  d2i_PROFESSION_INFO, d2i_PROXY_CERT_INFO_EXTENSION, d2i_PROXY_POLICY,
  d2i_RSA_OAEP_PARAMS, d2i_RSA_PSS_PARAMS, d2i_SCRYPT_PARAMS, d2i_SCT_LIST,
  d2i_SXNET, d2i_SXNETID, d2i_TS_ACCURACY, d2i_TS_MSG_IMPRINT,
  d2i_TS_MSG_IMPRINT_bio, d2i_TS_MSG_IMPRINT_fp, d2i_TS_REQ, d2i_TS_REQ_bio,
  d2i_TS_REQ_fp, d2i_TS_RESP, d2i_TS_RESP_bio, d2i_TS_RESP_fp,
  d2i_TS_STATUS_INFO, d2i_TS_TST_INFO, d2i_TS_TST_INFO_bio, d2i_TS_TST_INFO_fp,
  d2i_USERNOTICE, d2i_X509, d2i_X509_bio, d2i_X509_fp, d2i_X509_ALGOR,
  d2i_X509_ALGORS, d2i_X509_ATTRIBUTE, d2i_X509_CERT_AUX, d2i_X509_CINF,
  d2i_X509_CRL, d2i_X509_CRL_INFO, d2i_X509_CRL_bio, d2i_X509_CRL_fp,
  d2i_X509_EXTENSION, d2i_X509_EXTENSIONS, d2i_X509_NAME, d2i_X509_NAME_ENTRY,
  d2i_X509_PUBKEY, d2i_X509_PUBKEY_bio, d2i_X509_PUBKEY_fp, d2i_X509_REQ,
  d2i_X509_REQ_INFO, d2i_X509_REQ_bio, d2i_X509_REQ_fp, d2i_X509_REVOKED,
  d2i_X509_SIG, d2i_X509_VAL, i2d_ACCESS_DESCRIPTION, i2d_ADMISSIONS,
  i2d_ADMISSION_SYNTAX, i2d_ASIdOrRange, i2d_ASIdentifierChoice,
  i2d_ASIdentifiers, i2d_ASN1_BIT_STRING, i2d_ASN1_BMPSTRING,
  i2d_ASN1_ENUMERATED, i2d_ASN1_GENERALIZEDTIME, i2d_ASN1_GENERALSTRING,
  i2d_ASN1_IA5STRING, i2d_ASN1_INTEGER, i2d_ASN1_NULL, i2d_ASN1_OBJECT,
  i2d_ASN1_OCTET_STRING, i2d_ASN1_PRINTABLE, i2d_ASN1_PRINTABLESTRING,
  i2d_ASN1_SEQUENCE_ANY, i2d_ASN1_SET_ANY, i2d_ASN1_T61STRING, i2d_ASN1_TIME,
  i2d_ASN1_TYPE, i2d_ASN1_UNIVERSALSTRING, i2d_ASN1_UTCTIME,
  i2d_ASN1_UTF8STRING, i2d_ASN1_VISIBLESTRING, i2d_ASN1_bio_stream, i2d_ASRange,
  i2d_AUTHORITY_INFO_ACCESS, i2d_AUTHORITY_KEYID, i2d_BASIC_CONSTRAINTS,
  i2d_CERTIFICATEPOLICIES, i2d_CMS_ContentInfo, i2d_CMS_ReceiptRequest,
  i2d_CMS_bio, i2d_CRL_DIST_POINTS, i2d_DHxparams, i2d_DIRECTORYSTRING,
  i2d_DISPLAYTEXT, i2d_DIST_POINT, i2d_DIST_POINT_NAME, i2d_DSA_SIG,
  i2d_ECDSA_SIG, i2d_ECPKParameters, i2d_EDIPARTYNAME, i2d_ESS_CERT_ID,
  i2d_ESS_CERT_ID_V2, i2d_ESS_ISSUER_SERIAL, i2d_ESS_SIGNING_CERT,
  i2d_ESS_SIGNING_CERT_V2, i2d_EXTENDED_KEY_USAGE, i2d_GENERAL_NAME,
  i2d_GENERAL_NAMES, i2d_IPAddressChoice, i2d_IPAddressFamily,
  i2d_IPAddressOrRange, i2d_IPAddressRange, i2d_ISSUER_SIGN_TOOL,
  i2d_ISSUING_DIST_POINT, i2d_NAMING_AUTHORITY, i2d_NETSCAPE_CERT_SEQUENCE,
  i2d_NETSCAPE_SPKAC, i2d_NETSCAPE_SPKI, i2d_NOTICEREF, i2d_OCSP_BASICRESP,
  i2d_OCSP_CERTID, i2d_OCSP_CERTSTATUS, i2d_OCSP_CRLID, i2d_OCSP_ONEREQ,
  i2d_OCSP_REQINFO, i2d_OCSP_REQUEST, i2d_OCSP_RESPBYTES, i2d_OCSP_RESPDATA,
  i2d_OCSP_RESPID, i2d_OCSP_RESPONSE, i2d_OCSP_REVOKEDINFO, i2d_OCSP_SERVICELOC,
  i2d_OCSP_SIGNATURE, i2d_OCSP_SINGLERESP, i2d_OSSL_CMP_MSG,
  i2d_OSSL_CMP_PKIHEADER, i2d_OSSL_CMP_PKISI, i2d_OSSL_CRMF_CERTID,
  i2d_OSSL_CRMF_CERTTEMPLATE, i2d_OSSL_CRMF_ENCRYPTEDVALUE, i2d_OSSL_CRMF_MSG,
  i2d_OSSL_CRMF_MSGS, i2d_OSSL_CRMF_PBMPARAMETER,
  i2d_OSSL_CRMF_PKIPUBLICATIONINFO, i2d_OSSL_CRMF_SINGLEPUBINFO, i2d_OTHERNAME,
  i2d_PBE2PARAM, i2d_PBEPARAM, i2d_PBKDF2PARAM, i2d_PKCS12, i2d_PKCS12_BAGS,
  i2d_PKCS12_MAC_DATA, i2d_PKCS12_SAFEBAG, i2d_PKCS12_bio, i2d_PKCS12_fp,
  i2d_PKCS7, i2d_PKCS7_DIGEST, i2d_PKCS7_ENCRYPT, i2d_PKCS7_ENC_CONTENT,
  i2d_PKCS7_ENVELOPE, i2d_PKCS7_ISSUER_AND_SERIAL, i2d_PKCS7_NDEF,
  i2d_PKCS7_RECIP_INFO, i2d_PKCS7_SIGNED, i2d_PKCS7_SIGNER_INFO,
  i2d_PKCS7_SIGN_ENVELOPE, i2d_PKCS7_bio, i2d_PKCS7_fp,
  i2d_PKCS8PrivateKeyInfo_bio, i2d_PKCS8PrivateKeyInfo_fp,
  i2d_PKCS8_PRIV_KEY_INFO, i2d_PKCS8_PRIV_KEY_INFO_bio,
  i2d_PKCS8_PRIV_KEY_INFO_fp, i2d_PKCS8_bio, i2d_PKCS8_fp,
  i2d_PKEY_USAGE_PERIOD, i2d_POLICYINFO, i2d_POLICYQUALINFO,
  i2d_PROFESSION_INFO, i2d_PROXY_CERT_INFO_EXTENSION, i2d_PROXY_POLICY,
  i2d_RSA_OAEP_PARAMS, i2d_RSA_PSS_PARAMS, i2d_SCRYPT_PARAMS, i2d_SCT_LIST,
  i2d_SXNET, i2d_SXNETID, i2d_TS_ACCURACY, i2d_TS_MSG_IMPRINT,
  i2d_TS_MSG_IMPRINT_bio, i2d_TS_MSG_IMPRINT_fp, i2d_TS_REQ, i2d_TS_REQ_bio,
  i2d_TS_REQ_fp, i2d_TS_RESP, i2d_TS_RESP_bio, i2d_TS_RESP_fp,
  i2d_TS_STATUS_INFO, i2d_TS_TST_INFO, i2d_TS_TST_INFO_bio, i2d_TS_TST_INFO_fp,
  i2d_USERNOTICE, i2d_X509, i2d_X509_bio, i2d_X509_fp, i2d_X509_ALGOR,
  i2d_X509_ALGORS, i2d_X509_ATTRIBUTE, i2d_X509_CERT_AUX, i2d_X509_CINF,
  i2d_X509_CRL, i2d_X509_CRL_INFO, i2d_X509_CRL_bio, i2d_X509_CRL_fp,
  i2d_X509_EXTENSION, i2d_X509_EXTENSIONS, i2d_X509_NAME, i2d_X509_NAME_ENTRY,
  i2d_X509_PUBKEY, i2d_X509_PUBKEY_bio, i2d_X509_PUBKEY_fp, i2d_X509_REQ,
  i2d_X509_REQ_INFO, i2d_X509_REQ_bio, i2d_X509_REQ_fp, i2d_X509_REVOKED,
  i2d_X509_SIG, i2d_X509_VAL, - convert objects from/to ASN.1/DER representation
 TYPE *d2i_TYPE(TYPE **a, const unsigned char **ppin, long length);
 TYPE *d2i_TYPE_bio(BIO *bp, TYPE **a);
 TYPE *d2i_TYPE_fp(FILE *fp, TYPE **a);
 int i2d_TYPE(const TYPE *a, unsigned char **ppout);
 int i2d_TYPE(TYPE *a, unsigned char **ppout);
 int i2d_TYPE_fp(FILE *fp, const TYPE *a);
 int i2d_TYPE_fp(FILE *fp, TYPE *a);
 int i2d_TYPE_bio(BIO *bp, const TYPE *a);
 int i2d_TYPE_bio(BIO *bp, TYPE *a);
In the description here, TYPE is used a placeholder
  for any of the OpenSSL datatypes, such as X509_CRL. The function
  parameters ppin and ppout are generally either both named
  pp in the headers, or in and out.
These functions convert OpenSSL objects to and from their
    ASN.1/DER encoding. Unlike the C structures which can have pointers to
    sub-objects within, the DER is a serialized encoding, suitable for sending
    over the network, writing to a file, and so on.
d2i_TYPE() attempts to decode
    len bytes at *ppin. If successful a pointer to the
    TYPE structure is returned and *ppin is
    incremented to the byte following the parsed data. If a is not NULL
    then a pointer to the returned structure is also written to *a. If an
    error occurred then NULL is returned.
On a successful return, if *a is not NULL then it is
    assumed that *a contains a valid TYPE
    structure and an attempt is made to reuse it. For
    TYPE structures where it matters it is possible
    to set up a library context on the decoded structure this way (see the
    EXAMPLES section). However using the "reuse" capability for
    other purposes is strongly discouraged (see BUGS below,
    and the discussion in the RETURN VALUES section).
d2i_TYPE_bio() is similar to
    d2i_ TYPE() except it attempts to parse data
    from BIO bp.
d2i_TYPE_fp() is similar to
    d2i_ TYPE() except it attempts to parse data
    from FILE pointer fp.
i2d_TYPE() encodes the structure
    pointed to by a into DER format. If ppout is not NULL, it
    writes the DER encoded data to the buffer at *ppout, and increments
    it to point after the data just written. If the return value is negative an
    error occurred, otherwise it returns the length of the encoded data.
If *ppout is NULL memory will be allocated for a buffer and
    the encoded data written to it. In this case *ppout is not
    incremented and it points to the start of the data just written.
i2d_TYPE_bio() is similar to
    i2d_ TYPE() except it writes the encoding of the
    structure a to BIO bp and it returns 1 for success and 0 for
    failure.
i2d_TYPE_fp() is similar to
    i2d_ TYPE() except it writes the encoding of the
    structure a to FILE pointer fp and it returns 1 for success
    and 0 for failure.
These routines do not encrypt private keys and therefore offer no
    security; use PEM_write_PrivateKey(3) or similar for writing to
    files.
The letters i and d in i2d_TYPE()
  stand for "internal" (that is, an internal C structure) and
  "DER" respectively. So i2d_TYPE()
  converts from internal to DER.
The functions can also understand BER forms.
The actual TYPE structure passed to
    i2d_TYPE() must be a valid populated
    TYPE structure -- it cannot simply be fed
    with an empty structure such as that returned by TYPE_new().
The encoded data is in binary form and may contain embedded zeros.
    Therefore, any FILE pointers or BIOs should be opened in binary mode.
    Functions such as strlen() will not return the correct length
    of the encoded structure.
The ways that *ppin and *ppout are incremented after
    the operation can trap the unwary. See the WARNINGS section for some
    common errors. The reason for this-auto increment behaviour is to reflect a
    typical usage of ASN1 functions: after one structure is encoded or decoded
    another will be processed after it.
The following points about the data types might be useful:
  - ASN1_OBJECT
- Represents an ASN1 OBJECT IDENTIFIER.
- DHparams
- Represents a PKCS#3 DH parameters structure.
- DHxparams
- Represents an ANSI X9.42 DH parameters structure.
- ECDSA_SIG
- Represents an ECDSA signature.
- X509_ALGOR
- Represents an AlgorithmIdentifier structure as used in IETF RFC
      6960 and elsewhere.
- X509_NAME
- Represents a Name type as used for subject and issuer names in IETF
      RFC 6960 and elsewhere.
- X509_REQ
- Represents a PKCS#10 certificate request.
- X509_SIG
- Represents the DigestInfo structure defined in PKCS#1 and
    PKCS#7.
d2i_TYPE(),
  d2i_TYPE_bio() and
  d2i_TYPE_fp() return a valid
  TYPE  structure or NULL if an error occurs. If the
  "reuse" capability has been used with a valid structure being passed
  in via a, then the object is freed in the event of error and *a
  is set to NULL.i2d_TYPE() returns the number of bytes
    successfully encoded or a negative value if an error occurs.
i2d_TYPE_bio() and
    i2d_TYPE_fp() return 1 for success and 0 if an
    error occurs.
Allocate and encode the DER encoding of an X509 structure:
 int len;
 unsigned char *buf;
 buf = NULL;
 len = i2d_X509(x, &buf);
 if (len < 0)
     /* error */
Attempt to decode a buffer:
 X509 *x;
 unsigned char *buf;
 const unsigned char *p;
 int len;
 /* Set up buf and len to point to the input buffer. */
 p = buf;
 x = d2i_X509(NULL, &p, len);
 if (x == NULL)
     /* error */
Alternative technique:
 X509 *x;
 unsigned char *buf;
 const unsigned char *p;
 int len;
 /* Set up buf and len to point to the input buffer. */
 p = buf;
 x = NULL;
 if (d2i_X509(&x, &p, len) == NULL)
     /* error */
Setting up a library context and property query:
 X509 *x;
 unsigned char *buf;
 const unsigned char *p;
 int len;
 OSSL_LIB_CTX *libctx = ....;
 const char *propq = ....;
 /* Set up buf and len to point to the input buffer. */
 p = buf;
 x = X509_new_ex(libctx, propq);
 if (d2i_X509(&x, &p, len) == NULL)
     /* error, x was freed and NULL assigned to it (see RETURN VALUES) */
Using a temporary variable is mandatory. A common mistake is to attempt to use a
  buffer directly as follows:
 int len;
 unsigned char *buf;
 len = i2d_X509(x, NULL);
 buf = OPENSSL_malloc(len);
 ...
 i2d_X509(x, &buf);
 ...
 OPENSSL_free(buf);
This code will result in buf apparently containing garbage
    because it was incremented after the call to point after the data just
    written. Also buf will no longer contain the pointer allocated by
    OPENSSL_malloc() and the subsequent call to OPENSSL_free() is
    likely to crash.
Another trap to avoid is misuse of the a argument to
    d2i_TYPE():
 X509 *x;
 if (d2i_X509(&x, &p, len) == NULL)
     /* error */
This will probably crash somewhere in d2i_X509(). The
    reason for this is that the variable x is uninitialized and an
    attempt will be made to interpret its (invalid) value as an X509
    structure, typically causing a segmentation violation. If x is set to
    NULL first then this will not happen.
In some versions of OpenSSL the "reuse" behaviour of
  d2i_TYPE() when *a is valid is broken and
  some parts of the reused structure may persist if they are not present in the
  new one. Additionally, in versions of OpenSSL prior to 1.1.0, when the
  "reuse" behaviour is used and an error occurs the behaviour is
  inconsistent. Some functions behaved as described here, while some did not
  free *a on error and did not set *a to NULL.
As a result of the above issues the "reuse" behaviour is
    strongly discouraged.
i2d_TYPE() will not return an error in
    many versions of OpenSSL, if mandatory fields are not initialized due to a
    programming error then the encoded structure may contain invalid data or
    omit the fields entirely and will not be parsed by
    d2i_TYPE (). This may be fixed in future so code
    should not assume that i2d_TYPE() will always
    succeed.
Any function which encodes a structure
    (i2d_TYPE (),
    i2d_TYPE_bio() or
    i2d_TYPE_fp()) may return a stale encoding if
    the structure has been modified after deserialization or previous
    serialization. This is because some objects cache the encoding for
    efficiency reasons.
Copyright 1998-2023 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License").
    You may not use this file except in compliance with the License. You can
    obtain a copy in the file LICENSE in the source distribution or at
    <https://www.openssl.org/source/license.html>.