int gnutls_x509_crt_get_issuer_dn_by_oid(gnutls_x509_crt_t cert, const char * oid, int indx, unsigned int raw_flag, void * buf, size_t * sizeof_buf);
should contain a gnutls_x509_crt_t structure
const char * oid
holds an Object Identified in null terminated string
In case multiple same OIDs exist in the RDN, this specifies which to send. Use zero to get the first one.
unsigned int raw_flag
If non zero returns the raw DER data of the DN part.
void * buf
a pointer to a structure to hold the name (may be null)
size_t * sizeof_buf
initially holds the size of buf
This function will extract the part of the name of the Certificate
issuer specified by the given OID. The output, if the raw flag is not
used, will be encoded as described in RFC2253. Thus a string that is
ASCII or UTF-8 encoded, depending on the certificate data.
Some helper macros with popular OIDs can be found in gnutls/x509.h
If raw flag is zero, this function will only return known OIDs as
text. Other OIDs will be DER encoded, as described in RFC2253 --
in hex format with a '#' prefix. You can check about known OIDs
If buf is null then only the size will be filled.
GNUTLS_E_SHORT_MEMORY_BUFFER if the provided buffer is not
long enough, and in that case the *sizeof_buf will be updated with
the required size. On success 0 is returned.