@deftypefun {int} {gnutls_x509_crt_get_issuer_alt_name} (gnutls_x509_crt_t @var{cert}, unsigned int @var{seq}, void * @var{ian}, size_t * @var{ian_size}, unsigned int * @var{critical})

@var{cert}: should contain a @code{gnutls_x509_crt_t}  type

@var{seq}: specifies the sequence number of the alt name (0 for the first one, 1 for the second etc.)

@var{ian}: is the place where the alternative name will be copied to

@var{ian_size}: holds the size of ian.

@var{critical}: will be non-zero if the extension is marked as critical (may be null)

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 @code{GNUTLS_SAN_OTHERNAME}  is returned.

You may use @code{gnutls_x509_crt_get_subject_alt_othername_oid()}  to get

the corresponding OID and the "virtual" SAN types (e.g.,

@code{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.

@strong{Returns:} the alternative issuer name type on success, one of the

enumerated @code{gnutls_x509_subject_alt_name_t} .  It will return

@code{GNUTLS_E_SHORT_MEMORY_BUFFER}  if  @code{ian_size} is not large enough

to hold the value.  In that case  @code{ian_size} will be updated with

the required size.  If the certificate does not have an

Alternative name with the specified sequence number then

@code{GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE}  is returned.

@strong{Since:} 2.10.0

@end deftypefun