---
name: "gnutls_x509_crt_set_extension_by_oid"
section: "3"
platform: "linux"
package: "gnutls"
version: "3.8.13-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/gnutls_x509_crt_set_extension_by_oid"
---

# gnutls\_x509\_crt\_set\_extension\_by\_oid(3)

API function

## NAME

gnutls\_x509\_crt\_set\_extension\_by\_oid - API function

## SYNOPSIS

**#include \<gnutls/x509.h\>**

**int gnutls\_x509\_crt\_set\_extension\_by\_oid(gnutls\_x509\_crt\_t** *crt***, const char \*** *oid***, const void \*** *buf***, size\_t** *sizeof\_buf***, unsigned int** *critical***);**

## ARGUMENTS

- gnutls\_x509\_crt\_t crt

  a certificate of type **gnutls\_x509\_crt\_t**

- const char \* oid

  holds an Object Identifier in null terminated string

- const void \* buf

  a pointer to a DER encoded data

- size\_t sizeof\_buf

  holds the size of  *buf*

- unsigned int critical

  should be non-zero if the extension is to be marked as critical

## DESCRIPTION

This function will set an the extension, by the specified OID, in the certificate.  The extension data should be binary data DER encoded.

## RETURNS

On success, **GNUTLS\_E\_SUCCESS** (0) is returned, otherwise a negative error value.

## REPORTING BUGS

Report bugs to \<bugs@gnutls.org\>.\
 Home page: https://www.gnutls.org

## COPYRIGHT

Copyright © 2001-2023 Free Software Foundation, Inc., and others.\
 Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.

## SEE ALSO

The full documentation for **gnutls** is maintained as a Texinfo manual. If the /usr/share/doc/gnutls/ directory does not contain the HTML form visit

- https://www.gnutls.org/manual/