#include <stdio.h>
#include "cryptlib.h"
#include <openssl/x509v3.h>
#include <openssl/x509_vfy.h>

'defines'
#define	X509_PURPOSE_COUNT (sizeof(xstandard)/sizeof(X509_PURPOSE))
#define	V1_ROOT (EXFLAG_V1\|EXFLAG_SS)
#define	ku_reject(x, usage) (((x)->ex_flags & EXFLAG_KUSAGE) && !((x)->ex_kusage & (usage)))
#define	xku_reject(x, usage) (((x)->ex_flags & EXFLAG_XKUSAGE) && !((x)->ex_xkusage & (usage)))
#define	ns_reject(x, usage) (((x)->ex_flags & EXFLAG_NSCERT) && !((x)->ex_nscert & (usage)))
Funciones
int	X509_check_purpose (X509 *x, int id, int ca)
int	X509_PURPOSE_set (int *p, int purpose)
int	X509_PURPOSE_get_count (void)
X509_PURPOSE *	X509_PURPOSE_get0 (int idx)
int	X509_PURPOSE_get_by_sname (char *sname)
int	X509_PURPOSE_get_by_id (int purpose)
int	X509_PURPOSE_add (int id, int trust, int flags, int(ck)(const X509_PURPOSE , const X509 , int), char name, char sname, void arg)
void	X509_PURPOSE_cleanup (void)
int	X509_PURPOSE_get_id (X509_PURPOSE *xp)
char *	X509_PURPOSE_get0_name (X509_PURPOSE *xp)
char *	X509_PURPOSE_get0_sname (X509_PURPOSE *xp)
int	X509_PURPOSE_get_trust (X509_PURPOSE *xp)
int	X509_supported_extension (X509_EXTENSION *ex)
int	X509_check_ca (X509 *x)
int	X509_check_issued (X509 issuer, X509 subject)

Documentación de los 'defines'

#define ku_reject	(	x,
		usage
	)	(((x)->ex_flags & EXFLAG_KUSAGE) && !((x)->ex_kusage & (usage)))

#define ns_reject	(	x,
		usage
	)	(((x)->ex_flags & EXFLAG_NSCERT) && !((x)->ex_nscert & (usage)))

#define V1_ROOT (EXFLAG_V1|EXFLAG_SS)

#define X509_PURPOSE_COUNT (sizeof(xstandard)/sizeof(X509_PURPOSE))

#define xku_reject	(	x,
		usage
	)	(((x)->ex_flags & EXFLAG_XKUSAGE) && !((x)->ex_xkusage & (usage)))

Documentación de las funciones

int X509_check_ca ( X509 * x )

int X509_PURPOSE_add	(	int	id,
		int	trust,
		int	flags,
		int()(const X509_PURPOSE , const X509 *, int)	ck,
		char *	name,
		char *	sname,
		void *	arg
	)

void X509_PURPOSE_cleanup ( void )

X509_PURPOSE* X509_PURPOSE_get0 ( int idx )

char* X509_PURPOSE_get0_name ( X509_PURPOSE * xp )

char* X509_PURPOSE_get0_sname ( X509_PURPOSE * xp )

int X509_PURPOSE_get_by_id ( int purpose )

int X509_PURPOSE_get_by_sname ( char * sname )

int X509_PURPOSE_get_count ( void )

int X509_PURPOSE_get_id ( X509_PURPOSE * xp )

int X509_PURPOSE_get_trust ( X509_PURPOSE * xp )

int X509_supported_extension ( X509_EXTENSION * ex )