X509V3_GET_D2I(3ossl)

📦 version 3.5.0, in opensuse-leap 16.0

🎀 NAME 🎀

Hiii bestie 💖 welcome to the X509V3_GET_D2I(3ossl) page — the one where we decode and encode X509 extensions. The whole squad is:

  • X509V3_get_d2i
  • X509V3_add1_i2d
  • X509V3_EXT_d2i
  • X509V3_EXT_i2d
  • X509_get_ext_d2i
  • X509_add1_ext_i2d
  • X509_ACERT_get_ext_d2i
  • X509_ACERT_add1_ext_i2d
  • X509_CRL_get_ext_d2i
  • X509_CRL_add1_ext_i2d
  • X509_REVOKED_get_ext_d2i
  • X509_REVOKED_add1_ext_i2d
  • X509_get0_extensions
  • X509_ACERT_get0_extensions
  • X509_CRL_get0_extensions
  • X509_REVOKED_get0_extensions

These are the X509 extension decode and encode functions, periodt 💅

📜 SYNOPSIS 📜

#include <openssl/x509v3.h>

void *X509V3_get_d2i(const STACK_OF(X509_EXTENSION) *x, int nid, int *crit,
                     int *idx);
int X509V3_add1_i2d(STACK_OF(X509_EXTENSION) **x, int nid, void *value,
                    int crit, unsigned long flags);

void *X509V3_EXT_d2i(X509_EXTENSION *ext);
X509_EXTENSION *X509V3_EXT_i2d(int ext_nid, int crit, void *ext_struc);

void *X509_get_ext_d2i(const X509 *x, int nid, int *crit, int *idx);
int X509_add1_ext_i2d(X509 *x, int nid, void *value, int crit,
                      unsigned long flags);

void *X509_ACERT_get_ext_d2i(const X509_ACERT *x, int nid, int *crit, int *idx);
int X509_ACERT_add1_ext_i2d(X509_ACERT *x, int nid, void *value, int crit,
                            unsigned long flags);

void *X509_CRL_get_ext_d2i(const X509_CRL *crl, int nid, int *crit, int *idx);
int X509_CRL_add1_ext_i2d(X509_CRL *crl, int nid, void *value, int crit,
                          unsigned long flags);

void *X509_REVOKED_get_ext_d2i(const X509_REVOKED *r, int nid, int *crit, int *idx);
int X509_REVOKED_add1_ext_i2d(X509_REVOKED *r, int nid, void *value, int crit,
                              unsigned long flags);

const STACK_OF(X509_EXTENSION) *X509_get0_extensions(const X509 *x);
const STACK_OF(X509_EXTENSION) *X509_ACERT_get0_extensions(const X509 *x);
const STACK_OF(X509_EXTENSION) *X509_CRL_get0_extensions(const X509_CRL *crl);
const STACK_OF(X509_EXTENSION) *X509_REVOKED_get0_extensions(const X509_REVOKED *r);

💖 DESCRIPTION 💖

Okay so here’s the tea, bestie 🍓:

  • X509V3_get_d2i() — looks for an extension with OID nid in the extensions x and, if found, decodes it. If idx is NULL then only one occurrence of an extension is permissible, otherwise the first extension after index *idx is returned and *idx updated to the location of the extension. If crit is not NULL then *crit is set to a status value:
    • -2 if the extension occurs multiple times (this is only returned if idx is NULL)
    • -1 if the extension could not be found
    • 0 if the extension is found and is not critical
    • 1 if critical

A pointer to an extension specific structure or NULL is returned.

  • X509V3_add1_i2d() — adds extension value to STACK *x (allocating a new STACK if necessary) using OID nid and criticality crit according to flags.
  • X509V3_EXT_d2i() — attempts to decode the ASN.1 data contained in extension ext and returns a pointer to an extension specific structure or NULL if the extension could not be decoded (invalid syntax or not supported).
  • X509V3_EXT_i2d() — encodes the extension specific structure ext_struc with OID ext_nid and criticality crit.
  • X509_get_ext_d2i() and X509_add1_ext_i2d() — operate on the extensions of certificate x. They are otherwise identical to X509V3_get_d2i() and X509V3_add1_i2d().
  • X509_ACERT_get_ext_d2i() and X509_ACERT_add1_ext_i2d() — operate on the extensions of X509_ACERT structure x. They are otherwise identical to X509V3_get_d2i() and X509V3_add1_i2d().
  • X509_CRL_get_ext_d2i() and X509_CRL_add1_ext_i2d() — operate on the extensions of CRL crl. They are otherwise identical to X509V3_get_d2i() and X509V3_add1_i2d().
  • X509_REVOKED_get_ext_d2i() and X509_REVOKED_add1_ext_i2d() — operate on the extensions of X509_REVOKED structure r (i.e for CRL entry extensions). They are otherwise identical to X509V3_get_d2i() and X509V3_add1_i2d().
  • X509_get0_extensions(), X509_ACERT_get0_extensions(), X509_CRL_get0_extensions() and X509_REVOKED_get0_extensions() — return a STACK of all the extensions of a certificate, an attribute certificate, a CRL or a CRL entry respectively.

🧠 NOTES 🧠

In almost all cases an extension can occur at most once and multiple occurrences is an error. Therefore, the idx parameter is usually NULL.

The flags parameter may be one of the following values.

  • X509V3_ADD_DEFAULT — appends a new extension only if the extension does not exist. An error is returned if the extension exists.
  • X509V3_ADD_APPEND — appends a new extension, ignoring whether the extension exists.
  • X509V3_ADD_REPLACE — replaces an existing extension. If the extension does not exist, appends a new extension.
  • X509V3_ADD_REPLACE_EXISTING — replaces an existing extension. If the extension does not exist, returns an error.
  • X509V3_ADD_KEEP_EXISTING — appends a new extension only if the extension does not exist. An error is not returned if the extension exists.
  • X509V3_ADD_DELETE — deletes and frees an existing extension. If the extension does not exist, returns an error. No new extension is added.
  • X509V3_ADD_SILENT — if bitwise ORed with flags: any error returned will not be added to the error queue.

The function X509V3_get_d2i() and its variants will return NULL if the extension is not found, occurs multiple times or cannot be decoded. It is possible to determine the precise reason by checking the value of *crit. The returned pointer must be explicitly freed.

The function X509V3_add1_i2d() and its variants allocate X509_EXTENSION objects on STACK *x depending on flags. The X509_EXTENSION objects must be explicitly freed using X509_EXTENSION_free().

🌈 SUPPORTED EXTENSIONS 🌈

The following sections contain a list of all supported extensions including their name and NID.

🦋 PKIX Certificate Extensions 🦋

The following certificate extensions are defined in PKIX standards such as RFC5280.

  • Basic Constraints — NID_basic_constraints
  • Key Usage — NID_key_usage
  • Extended Key Usage — NID_ext_key_usage
  • Subject Key Identifier — NID_subject_key_identifier
  • Authority Key Identifier — NID_authority_key_identifier
  • Private Key Usage Period — NID_private_key_usage_period
  • Subject Alternative Name — NID_subject_alt_name
  • Issuer Alternative Name — NID_issuer_alt_name
  • Authority Information Access — NID_info_access
  • Subject Information Access — NID_sinfo_access
  • Name Constraints — NID_name_constraints
  • Certificate Policies — NID_certificate_policies
  • Policy Mappings — NID_policy_mappings
  • Policy Constraints — NID_policy_constraints
  • Inhibit Any Policy — NID_inhibit_any_policy
  • TLS Feature — NID_tlsfeature

🕸️ Netscape Certificate Extensions 🕸️

The following are (largely obsolete) Netscape certificate extensions.

  • Netscape Cert Type — NID_netscape_cert_type
  • Netscape Base Url — NID_netscape_base_url
  • Netscape Revocation Url — NID_netscape_revocation_url
  • Netscape CA Revocation Url — NID_netscape_ca_revocation_url
  • Netscape Renewal Url — NID_netscape_renewal_url
  • Netscape CA Policy Url — NID_netscape_ca_policy_url
  • Netscape SSL Server Name — NID_netscape_ssl_server_name
  • Netscape Comment — NID_netscape_comment

🎲 Miscellaneous Certificate Extensions 🎲

  • Strong Extranet ID — NID_sxnet
  • Proxy Certificate Information — NID_proxyCertInfo

📚 PKIX CRL Extensions 📚

The following are CRL extensions from PKIX standards such as RFC5280.

  • CRL Number — NID_crl_number
  • CRL Distribution Points — NID_crl_distribution_points
  • Delta CRL Indicator — NID_delta_crl
  • Freshest CRL — NID_freshest_crl
  • Invalidity Date — NID_invalidity_date
  • Issuing Distribution Point — NID_issuing_distribution_point

The following are CRL entry extensions from PKIX standards such as RFC5280.

  • CRL Reason Code — NID_crl_reason
  • Certificate Issuer — NID_certificate_issuer

🩺 OCSP Extensions 🩺

  • OCSP Nonce — NID_id_pkix_OCSP_Nonce
  • OCSP CRL ID — NID_id_pkix_OCSP_CrlID
  • Acceptable OCSP Responses — NID_id_pkix_OCSP_acceptableResponses
  • OCSP No Check — NID_id_pkix_OCSP_noCheck
  • OCSP Archive Cutoff — NID_id_pkix_OCSP_archiveCutoff
  • OCSP Service Locator — NID_id_pkix_OCSP_serviceLocator
  • Hold Instruction Code — NID_hold_instruction_code

🔍 Certificate Transparency Extensions 🔍

The following extensions are used by certificate transparency, RFC6962.

  • CT Precertificate SCTs — NID_ct_precert_scts
  • CT Certificate SCTs — NID_ct_cert_scts

💀 RETURN VALUES 💀

  • X509V3_get_d2i(), its variants, and X509V3_EXT_d2i() — return a pointer to an extension specific structure or NULL if an error occurs.
  • X509V3_add1_i2d() and its variants — return 1 if the operation is successful and 0 if it fails due to a non-fatal error (extension not found, already exists, cannot be encoded) or -1 due to a fatal error such as a memory allocation failure.
  • X509V3_EXT_i2d() — returns a pointer to an X509_EXTENSION structure or NULL if an error occurs.
  • X509_get0_extensions(), X509_CRL_get0_extensions() and X509_REVOKED_get0_extensions() — return a stack of extensions. They return NULL if no extensions are present.

🫶 SEE ALSO 🫶

🧚 HISTORY 🧚

X509_ACERT_get_ext_d2i(), X509_ACERT_add1_ext_i2d(), X509_ACERT_get0_extensions() were added in OpenSSL 3.4.

Copyright 2015-2024 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>.

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