检测证书是否有密钥用法

int CheckCertKeyUsage(X509 *cert, int keyUsage, int exKeyUsage){int res = 0;X509_check_purpose(cert, -1, 0);if (keyUsage && ((cert->ex_kusage & keyUsage) != keyUsage)){goto end;}if (exKeyUsage && ((cert->ex_xkusage & exKeyUsage) != exKeyUsage)){goto end;}res = 1;end:return res;}