---
name: "gnutls_x509_crt_get_issuer_alt_name"
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_get_issuer_alt_name"
---

# gnutls\_x509\_crt\_get\_issuer\_alt\_name(3)

API function

## NAME

gnutls\_x509\_crt\_get\_issuer\_alt\_name - API function

## SYNOPSIS

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

**int gnutls\_x509\_crt\_get\_issuer\_alt\_name(gnutls\_x509\_crt\_t** *cert***, unsigned int** *seq***, void \*** *ian***, size\_t \*** *ian\_size***, unsigned int \*** *critical***);**

## ARGUMENTS

- gnutls\_x509\_crt\_t cert

  should contain a **gnutls\_x509\_crt\_t** type

- unsigned int seq

  specifies the sequence number of the alt name (0 for the first one, 1 for the second etc.)

- void \* ian

  is the place where the alternative name will be copied to

- size\_t \* ian\_size

  holds the size of ian.

- unsigned int \* critical

  will be non-zero if the extension is marked as critical (may be null)

## DESCRIPTION

This function retrieves the Issuer Alternative Name (2.5.29.18), contained in the given certificate in the X509v3 Certificate Extensions.

When the SAN type is otherName, it will extract the data in the otherName's value field, and **GNUTLS\_SAN\_OTHERNAME** is returned. You may use **gnutls\_x509\_crt\_get\_subject\_alt\_othername\_oid()** to get the corresponding OID and the "virtual" SAN types (e.g., **GNUTLS\_SAN\_OTHERNAME\_XMPP**).

If an otherName OID is known, the data will be decoded.  Otherwise the returned data will be DER encoded, and you will have to decode it yourself.  Currently, only the RFC 3920 id-on-xmppAddr Issuer AltName is recognized.

## RETURNS

the alternative issuer name type on success, one of the enumerated **gnutls\_x509\_subject\_alt\_name\_t**.  It will return **GNUTLS\_E\_SHORT\_MEMORY\_BUFFER** if  *ian\_size* is not large enough to hold the value.  In that case  *ian\_size* will be updated with the required size.  If the certificate does not have an Alternative name with the specified sequence number then **GNUTLS\_E\_REQUESTED\_DATA\_NOT\_AVAILABLE** is returned.

## SINCE

2\.10.0

## 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/