NAME

       X509v3_get_ext_count, X509v3_get_ext, X509v3_get_ext_by_NID, X509v3_get_ext_by_OBJ,
       X509v3_get_ext_by_critical, X509v3_delete_ext, X509v3_add_ext, X509_get_ext_count,
       X509_get_ext, X509_get_ext_by_NID, X509_get_ext_by_OBJ, X509_get_ext_by_critical,
       X509_delete_ext, X509_add_ext, X509_CRL_get_ext_count, X509_CRL_get_ext,
       X509_CRL_get_ext_by_NID, X509_CRL_get_ext_by_OBJ, X509_CRL_get_ext_by_critical,
       X509_CRL_delete_ext, X509_CRL_add_ext, X509_REVOKED_get_ext_count, X509_REVOKED_get_ext,
       X509_REVOKED_get_ext_by_NID, X509_REVOKED_get_ext_by_OBJ,
       X509_REVOKED_get_ext_by_critical, X509_REVOKED_delete_ext, X509_REVOKED_add_ext -
       extension stack utility functions

SYNOPSIS

        #include <openssl/x509.h>

        int X509v3_get_ext_count(const STACK_OF(X509_EXTENSION) *x);
        X509_EXTENSION *X509v3_get_ext(const STACK_OF(X509_EXTENSION) *x, int loc);

        int X509v3_get_ext_by_NID(const STACK_OF(X509_EXTENSION) *x,
                                  int nid, int lastpos);
        int X509v3_get_ext_by_OBJ(const STACK_OF(X509_EXTENSION) *x,
                                  const ASN1_OBJECT *obj, int lastpos);
        int X509v3_get_ext_by_critical(const STACK_OF(X509_EXTENSION) *x,
                                       int crit, int lastpos);
        X509_EXTENSION *X509v3_delete_ext(STACK_OF(X509_EXTENSION) *x, int loc);
        STACK_OF(X509_EXTENSION) *X509v3_add_ext(STACK_OF(X509_EXTENSION) **x,
                                                 X509_EXTENSION *ex, int loc);

        int X509_get_ext_count(const X509 *x);
        X509_EXTENSION *X509_get_ext(const X509 *x, int loc);
        int X509_get_ext_by_NID(const X509 *x, int nid, int lastpos);
        int X509_get_ext_by_OBJ(const X509 *x, const ASN1_OBJECT *obj, int lastpos);
        int X509_get_ext_by_critical(const X509 *x, int crit, int lastpos);
        X509_EXTENSION *X509_delete_ext(X509 *x, int loc);
        int X509_add_ext(X509 *x, X509_EXTENSION *ex, int loc);

        int X509_CRL_get_ext_count(const X509_CRL *x);
        X509_EXTENSION *X509_CRL_get_ext(const X509_CRL *x, int loc);
        int X509_CRL_get_ext_by_NID(const X509_CRL *x, int nid, int lastpos);
        int X509_CRL_get_ext_by_OBJ(const X509_CRL *x, const ASN1_OBJECT *obj,
                                    int lastpos);
        int X509_CRL_get_ext_by_critical(const X509_CRL *x, int crit, int lastpos);
        X509_EXTENSION *X509_CRL_delete_ext(X509_CRL *x, int loc);
        int X509_CRL_add_ext(X509_CRL *x, X509_EXTENSION *ex, int loc);

        int X509_REVOKED_get_ext_count(const X509_REVOKED *x);
        X509_EXTENSION *X509_REVOKED_get_ext(const X509_REVOKED *x, int loc);
        int X509_REVOKED_get_ext_by_NID(const X509_REVOKED *x, int nid, int lastpos);
        int X509_REVOKED_get_ext_by_OBJ(const X509_REVOKED *x, const ASN1_OBJECT *obj,
                                        int lastpos);
        int X509_REVOKED_get_ext_by_critical(const X509_REVOKED *x, int crit, int lastpos);
        X509_EXTENSION *X509_REVOKED_delete_ext(X509_REVOKED *x, int loc);
        int X509_REVOKED_add_ext(X509_REVOKED *x, X509_EXTENSION *ex, int loc);

DESCRIPTION

       X509v3_get_ext_count() retrieves the number of extensions in x.

       X509v3_get_ext() retrieves extension loc from x. The index loc can take any value from 0
       to X509_get_ext_count(x) - 1. The returned extension is an internal pointer which MUST NOT
       be freed by the application.

       X509v3_get_ext_by_NID() and X509v3_get_ext_by_OBJ() look for an extension with nid or obj
       from extension STACK x. The search starts from the extension after lastpos or from the
       beginning if lastpos is -1. If the extension is found, its index is returned, otherwise -1
       is returned.

       X509v3_get_ext_by_critical() is similar to X509v3_get_ext_by_NID() except it looks for an
       extension of criticality crit. A zero value for crit looks for a non-critical extension. A
       nonzero value looks for a critical extension.

       X509v3_delete_ext() deletes the extension with index loc from x.  The deleted extension is
       returned and must be freed by the caller.  If loc is an invalid index value, NULL is
       returned.

       X509v3_add_ext() adds extension ex to STACK *x at position loc. If loc is -1, the new
       extension is added to the end. If *x is NULL, a new STACK will be allocated. The passed
       extension ex is duplicated internally so it must be freed after use.

       X509_get_ext_count(), X509_get_ext(), X509_get_ext_by_NID(), X509_get_ext_by_OBJ(),
       X509_get_ext_by_critical(), X509_delete_ext() and X509_add_ext() operate on the extensions
       of certificate x. They are otherwise identical to the X509v3 functions.

       X509_CRL_get_ext_count(), X509_CRL_get_ext(), X509_CRL_get_ext_by_NID(),
       X509_CRL_get_ext_by_OBJ(), X509_CRL_get_ext_by_critical(), X509_CRL_delete_ext() and
       X509_CRL_add_ext() operate on the extensions of CRL x. They are otherwise identical to the
       X509v3 functions.

       X509_REVOKED_get_ext_count(), X509_REVOKED_get_ext(), X509_REVOKED_get_ext_by_NID(),
       X509_REVOKED_get_ext_by_OBJ(), X509_REVOKED_get_ext_by_critical(),
       X509_REVOKED_delete_ext() and X509_REVOKED_add_ext() operate on the extensions of CRL
       entry x.  They are otherwise identical to the X509v3 functions.

NOTES

       These functions are used to examine stacks of extensions directly.  Applications that want
       to parse or encode and add an extension should use the extension encode and decode
       functions instead, such as X509_add1_ext_i2d() and X509_get_ext_d2i().

       For X509v3_get_ext_by_NID(), X509v3_get_ext_by_OBJ(), X509v3_get_ext_by_critical() and its
       variants, a zero index return value is not an error since extension STACK x indices start
       from zero.  These search functions start from the extension after the lastpos parameter so
       it should initially be set to -1. If it is set to zero, the initial extension will not be
       checked.

       X509v3_delete_ext() and its variants are a bit counter-intuitive because these functions
       do not free the extension they delete.  They return an X509_EXTENSION object which must be
       explicitly freed using X509_EXTENSION_free().

RETURN VALUES

       X509v3_get_ext_count() returns the extension count.

       X509v3_get_ext(), X509v3_delete_ext() and X509_delete_ext() return an X509_EXTENSION
       structure or NULL if an error occurs.

       X509v3_get_ext_by_NID(), X509v3_get_ext_by_OBJ() and X509v3_get_ext_by_critical() return
       the extension index or -1 if an error occurs.

       X509v3_add_ext() returns a STACK of extensions or NULL on error.

       X509_add_ext() returns 1 on success and 0 on error.

SEE ALSO

       X509V3_get_d2i(3)

COPYRIGHT

       Copyright 2015-2021 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>.