int gnutls_x509_crq_get_extension_by_oid(gnutls_x509_crq_t cert, const char * oid, int indx, void * buf, size_t * sizeof_buf, unsigned int * critical);
should contain a gnutls_x509_crq_t structure
const char * oid
holds an Object Identified in null terminated string
In case multiple same OIDs exist in the extensions, this
specifies which to send. Use zero to get the first one.
void * buf
a pointer to a structure to hold the name (may be null)
size_t * sizeof_buf
initially holds the size of buf
unsigned int * critical
will be non zero if the extension is marked as critical
This function will return the extension specified by the OID in
the certificate. The extensions will be returned as binary data
DER encoded, in the provided buffer.
On success, GNUTLS_E_SUCCESS is returned, otherwise a
negative value in case of an error. If the certificate does not
contain the specified extension
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE will be returned.