X509V3_GET_EXT_BY_NID(3) | Library Functions Manual | X509V3_GET_EXT_BY_NID(3)

# 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

library “libcrypto”
`#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 up 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, a negative value is returned.

`X509v3_get_ext_by_critical`() is similar to `X509v3_get_ext_by_NID`() except that it looks for an extension of criticality crit. A zero value for crit looks for a non-critical extension; a non-zero 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 the extension ex to the 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 the 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 the CRL entry x. They are otherwise identical to the X509v3 functions.

These functions are used to examine stacks of extensions directly. Many applications will want to parse or encode and add an extension: they should use the extension encode and decode functions instead such as X509_get_ext_d2i(3).

Extension indices start from zero, so a zero index return value is not an error. These search functions start from the extension after the lastpos parameter, so it should initially be set to -1. If it is set to 0, the initial extension will not be checked.

# RETURN VALUES

`X509v3_get_ext_count`() returns the extension count.

`X509v3_get_ext`(), `X509v3_delete_ext`(), and `X509_delete_ext`() return an X509_EXTENSION pointer 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. In addition, `X509v3_get_ext_by_NID`() returns -2 if OBJ_nid2obj(3) fails on the requested nid.

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

`X509_add_ext`() returns 1 on success or 0 on error.

# SEE ALSO

OBJ_nid2obj(3), X509_CRL_new(3), X509_EXTENSION_new(3), X509_new(3), X509_REVOKED_new(3), X509V3_EXT_print(3), X509V3_extensions_print(3), X509V3_get_d2i(3)

# HISTORY

These functions first appeared in SSLeay 0.8.0 and have been available since OpenBSD 2.4.

June 8, 2025 | Debian