---
name: "gnutls_certificate_set_retrieve_function"
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_certificate_set_retrieve_function"
---

# gnutls\_certificate\_set\_retrieve\_function(3)

API function

## NAME

gnutls\_certificate\_set\_retrieve\_function - API function

## SYNOPSIS

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

**void gnutls\_certificate\_set\_retrieve\_function(gnutls\_certificate\_credentials\_t** *cred***, gnutls\_certificate\_retrieve\_function \*** *func***);**

## ARGUMENTS

- gnutls\_certificate\_credentials\_t cred

  is a **gnutls\_certificate\_credentials\_t** type.

- gnutls\_certificate\_retrieve\_function \* func

  is the callback function

## DESCRIPTION

This function sets a callback to be called in order to retrieve the certificate to be used in the handshake. The callback will take control only if a certificate is requested by the peer. You are advised to use **gnutls\_certificate\_set\_retrieve\_function2()** because it is much more efficient in the processing it requires from gnutls.

The callback's function prototype is: int (\*callback)(gnutls\_session\_t, const gnutls\_datum\_t\* req\_ca\_dn, int nreqs, const gnutls\_pk\_algorithm\_t\* pk\_algos, int pk\_algos\_length, gnutls\_retr2\_st\* st);

 *req\_ca\_dn* is only used in X.509 certificates. Contains a list with the CA names that the server considers trusted. This is a hint and typically the client should send a certificate that is signed by one of these CAs. These names, when available, are DER encoded. To get a more meaningful value use the function **gnutls\_x509\_rdn\_get()**.

 *pk\_algos* contains a list with server's acceptable public key algorithms. The certificate returned should support the server's given algorithms.

 *st* should contain the certificates and private keys.

If the callback function is provided then gnutls will call it, in the handshake, after the certificate request message has been received.

In server side pk\_algos and req\_ca\_dn are NULL.

The callback function should set the certificate list to be sent, and return 0 on success. If no certificate was selected then the number of certificates should be set to zero. The value (-1) indicates error and the handshake will be terminated. If both certificates are set in the credentials and a callback is available, the callback takes predence.

## SINCE

3\.0

## 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/