=pod
=head1 NAME
X509_get0_extensions, X509_CRL_get0_extensions, X509_REVOKED_get0_extensions,
X509V3_get_d2i, X509V3_add1_i2d, X509V3_EXT_d2i, X509V3_EXT_i2d,
X509_get_ext_d2i, X509_add1_ext_i2d, X509_CRL_get_ext_d2i,
X509_CRL_add1_ext_i2d, X509_REVOKED_get_ext_d2i,
X509_REVOKED_add1_ext_i2d - X509 extension decode and encode functions
=head1 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);
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_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_CRL_get0_extensions(const X509_CRL *crl);
const STACK_OF(X509_EXTENSION) *X509_REVOKED_get0_extensions(const X509_REVOKED *r);
=head1 DESCRIPTION
X509V3_get_ext_d2i() looks for an extension with OID B<nid> in the extensions
B<x> and, if found, decodes it. If B<idx> is B<NULL> then only one
occurrence of an extension is permissible otherwise the first extension after
index B<*idx> is returned and B<*idx> updated to the location of the extension.
If B<crit> is not B<NULL> then B<*crit> is set to a status value: -2 if the
extension occurs multiple times (this is only returned if B<idx> is B<NULL>),
-1 if the extension could not be found, 0 if the extension is found and is
not critical and 1 if critical. A pointer to an extension specific structure
or B<NULL> is returned.
X509V3_add1_i2d() adds extension B<value> to STACK B<*x> (allocating a new
STACK if necessary) using OID B<nid> and criticality B<crit> according
to B<flags>.
X509V3_EXT_d2i() attempts to decode the ASN.1 data contained in extension
B<ext> and returns a pointer to an extension specific structure or B<NULL>
if the extension could not be decoded (invalid syntax or not supported).
X509V3_EXT_i2d() encodes the extension specific structure B<ext>
with OID B<ext_nid> and criticality B<crit>.
X509_get_ext_d2i() and X509_add1_ext_i2d() operate on the extensions of
certificate B<x>, they are otherwise identical to X509V3_get_d2i() and
X509V3_add_i2d().
X509_CRL_get_ext_d2i() and X509_CRL_add1_ext_i2d() operate on the extensions
of CRL B<crl>, they are otherwise identical to X509V3_get_d2i() and
X509V3_add_i2d().
X509_REVOKED_get_ext_d2i() and X509_REVOKED_add1_ext_i2d() operate on the
extensions of B<X509_REVOKED> structure B<r> (i.e for CRL entry extensions),
they are otherwise identical to X509V3_get_d2i() and X509V3_add_i2d().
X509_get0_extensions(), X509_CRL_get0_extensions() and
X509_REVOKED_get0_extensions() return a stack of all the extensions
of a certificate a CRL or a CRL entry respectively.
=head1 NOTES
In almost all cases an extension can occur at most once and multiple
occurrences is an error. Therefore, the B<idx> parameter is usually B<NULL>.
The B<flags> parameter may be one of the following values.
B<X509V3_ADD_DEFAULT> appends a new extension only if the extension does
not already exist. An error is returned if the extension does already
exist.
B<X509V3_ADD_APPEND> appends a new extension, ignoring whether the extension
already exists.
B<X509V3_ADD_REPLACE> replaces an extension if it exists otherwise appends
a new extension.
B<X509V3_ADD_REPLACE_EXISTING> replaces an existing extension if it exists
otherwise returns an error.
B<X509V3_ADD_KEEP_EXISTING> appends a new extension only if the extension does
not already exist. An error B<is not> returned if the extension does already
exist.
B<X509V3_ADD_DELETE> extension B<nid> is deleted: no new extension is added.
If B<X509V3_ADD_SILENT> is ored with B<flags>: any error returned will not
be added to the error queue.
The function X509V3_get_d2i() will return B<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 B<*crit>.
=head1 SUPPORTED EXTENSIONS
The following sections contain a list of all supported extensions
including their name and NID.
=head2 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
=head2 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
=head2 Miscellaneous Certificate Extensions
Strong Extranet ID NID_sxnet
Proxy Certificate Information NID_proxyCertInfo
=head2 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
=head2 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
=head2 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
=head1 RETURN VALUES
X509V3_EXT_d2i() and *X509V3_get_d2i() return a pointer to an extension
specific structure of B<NULL> if an error occurs.
X509V3_EXT_i2d() returns a pointer to an B<X509_EXTENSION> structure
or B<NULL> if an error occurs.
X509V3_add1_i2d() returns 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.
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.
=head1 SEE ALSO
L<d2i_X509(3)>,
L<ERR_get_error(3)>,
L<X509_CRL_get0_by_serial(3)>,
L<X509_get0_signature(3)>,
L<X509_get_ext_d2i(3)>,
L<X509_get_extension_flags(3)>,
L<X509_get_pubkey(3)>,
L<X509_get_subject_name(3)>,
L<X509_get_version(3)>,
L<X509_NAME_add_entry_by_txt(3)>,
L<X509_NAME_ENTRY_get_object(3)>,
L<X509_NAME_get_index_by_NID(3)>,
L<X509_NAME_print_ex(3)>,
L<X509_new(3)>,
L<X509_sign(3)>,
L<X509_verify_cert(3)>
=head1 COPYRIGHT
Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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
L<https://www.openssl.org/source/license.html>.
=cut
