int gnutls_x509_crt_get_key_purpose_oid(gnutls_x509_crt_t cert, int indx, void * oid, size_t * sizeof_oid, unsigned int * critical);
should contain a gnutls_x509_crt_t structure
This specifies which OID to return. Use zero to get the first one.
void * oid
a pointer to a buffer to hold the OID (may be null)
size_t * sizeof_oid
initially holds the size of oid
unsigned int * critical
output flag to indicate criticality of extension
This function will extract the key purpose OIDs of the Certificate
specified by the given index. These are stored in the Extended
Key Usage extension (18.104.22.168) See the GNUTLS_KP_* definitions
for human readable names.
If oid 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_oid will be
updated with the required size. On success 0 is returned.