How to create certificate choosing window like one in Safari? - macos

Question

I was looking for a way to create a window like that one in my program, but I haven't found any implementation of that. All I can do for now is get all certificates from keychain, but I can't get a cert in pem or der format. It is needed to supply certificate to a particular site.
- (void)logMessageForStatus:(OSStatus)status
functionName:(NSString *)functionName
{
CFStringRef errorMessage;
errorMessage = SecCopyErrorMessageString(status, NULL);
NSLog(#"error after %#: %#", functionName, (__bridge NSString *)errorMessage);
CFRelease(errorMessage);
}
- (void)listCertificates
{
OSStatus status;
SecKeychainSearchRef search = NULL;
// The first argument being NULL indicates the user's current keychain list
status = SecKeychainSearchCreateFromAttributes(NULL,
kSecCertificateItemClass, NULL, &search);
if (status != errSecSuccess) {
[self logMessageForStatus:status
functionName:#"SecKeychainSearchCreateFromAttributes()"];
return;
}
SecKeychainItemRef searchItem = NULL;
while (SecKeychainSearchCopyNext(search, &searchItem) != errSecItemNotFound) {
SecKeychainAttributeList attrList;
CSSM_DATA certData;
attrList.count = 0;
attrList.attr = NULL;
status = SecKeychainItemCopyContent(searchItem, NULL, &attrList,
(UInt32 *)(&certData.Length),
(void **)(&certData.Data));
if (status != errSecSuccess) {
[self logMessageForStatus:status
functionName:#"SecKeychainItemCopyContent()"];
CFRelease(searchItem);
continue;
}
// At this point you should have a valid CSSM_DATA structure
// representing the certificate
SecCertificateRef certificate;
status = SecCertificateCreateFromData(&certData, CSSM_CERT_X_509v3,
CSSM_CERT_ENCODING_BER, &certificate);
if (status != errSecSuccess) {
[self logMessageForStatus:status
functionName:#"SecCertificateCreateFromData()"];
SecKeychainItemFreeContent(&attrList, certData.Data);
CFRelease(searchItem);
continue;
}
// Do whatever you want to do with the certificate
// For instance, print its common name (if there's one)
CFStringRef commonName = NULL;
CFErrorRef err = NULL;
///CFArrayRef arr = NULL;
SecCertificateCopyCommonName(certificate, &commonName);
certs = SecCertificateCopyValues(certificate, NULL, &err);
//NSLog(#"common name = %#", (__bridge NSString *)commonName);
//NSLog(#"data = %#", (__bridge NSArray *)arr);
//certs = arr;
if (commonName) CFRelease(commonName);
//if (arr) CFRelease(arr);
SecKeychainItemFreeContent(&attrList, certData.Data);
CFRelease(searchItem);
}
CFRelease(search);
}
example
Is there any standard api to call such window? Or maybe there is some library? And how can I get der data from SecCertificateRef.
Thank you in advance!