SecCertificateRef: How to get the certificate information?

I couldn’t wait for an answer to the bounty, so I found a solution myself. As others said, Security.framework doesn’t give you a way to get this information, so you need to ask OpenSSL to parse the certificate data for you:

#import <openssl/x509.h>

// ...

NSData *certificateData = (NSData *) SecCertificateCopyData(certificate);

const unsigned char *certificateDataBytes = (const unsigned char *)[certificateData bytes];
X509 *certificateX509 = d2i_X509(NULL, &certificateDataBytes, [certificateData length]);

NSString *issuer = CertificateGetIssuerName(certificateX509);
NSDate *expiryDate = CertificateGetExpiryDate(certificateX509);

Where CertificateGetIssuerName and CertificateGetExpiryDate are as follows:

static NSString * CertificateGetIssuerName(X509 *certificateX509)
{
    NSString *issuer = nil;
    if (certificateX509 != NULL) {
        X509_NAME *issuerX509Name = X509_get_issuer_name(certificateX509);

        if (issuerX509Name != NULL) {
            int nid = OBJ_txt2nid("O"); // organization
            int index = X509_NAME_get_index_by_NID(issuerX509Name, nid, -1);

            X509_NAME_ENTRY *issuerNameEntry = X509_NAME_get_entry(issuerX509Name, index);

            if (issuerNameEntry) {
                ASN1_STRING *issuerNameASN1 = X509_NAME_ENTRY_get_data(issuerNameEntry);

                if (issuerNameASN1 != NULL) {
                    unsigned char *issuerName = ASN1_STRING_data(issuerNameASN1);
                    issuer = [NSString stringWithUTF8String:(char *)issuerName];
                }
            }
        }
    }

    return issuer;
}

static NSDate *CertificateGetExpiryDate(X509 *certificateX509)
{
    NSDate *expiryDate = nil;

    if (certificateX509 != NULL) {
        ASN1_TIME *certificateExpiryASN1 = X509_get_notAfter(certificateX509);
        if (certificateExpiryASN1 != NULL) {
            ASN1_GENERALIZEDTIME *certificateExpiryASN1Generalized = ASN1_TIME_to_generalizedtime(certificateExpiryASN1, NULL);
            if (certificateExpiryASN1Generalized != NULL) {
                unsigned char *certificateExpiryData = ASN1_STRING_data(certificateExpiryASN1Generalized);

                // ASN1 generalized times look like this: "20131114230046Z"
                //                                format:  YYYYMMDDHHMMSS
                //                               indices:  01234567890123
                //                                                   1111
                // There are other formats (e.g. specifying partial seconds or 
                // time zones) but this is good enough for our purposes since
                // we only use the date and not the time.
                //
                // (Source: http://www.obj-sys.com/asn1tutorial/node14.html)

                NSString *expiryTimeStr = [NSString stringWithUTF8String:(char *)certificateExpiryData];
                NSDateComponents *expiryDateComponents = [[NSDateComponents alloc] init];

                expiryDateComponents.year   = [[expiryTimeStr substringWithRange:NSMakeRange(0, 4)] intValue];
                expiryDateComponents.month  = [[expiryTimeStr substringWithRange:NSMakeRange(4, 2)] intValue];
                expiryDateComponents.day    = [[expiryTimeStr substringWithRange:NSMakeRange(6, 2)] intValue];
                expiryDateComponents.hour   = [[expiryTimeStr substringWithRange:NSMakeRange(8, 2)] intValue];
                expiryDateComponents.minute = [[expiryTimeStr substringWithRange:NSMakeRange(10, 2)] intValue];
                expiryDateComponents.second = [[expiryTimeStr substringWithRange:NSMakeRange(12, 2)] intValue];

                NSCalendar *calendar = [NSCalendar currentCalendar];
                expiryDate = [calendar dateFromComponents:expiryDateComponents];

                [expiryDateComponents release];
            }
        }
    }

    return expiryDate;
}

I only actually needed the issuer’s organization name and the expiry date for my purposes, so that’s all the code I’ve included below. But, based on this you should be able to figure out the rest by reading the x509.h header file.

Edit:

Here’s how to get the certificate. I haven’t put any error handling, etc. You’ll want to check trustResult, err, etc., for example.

NSURLAuthenticationChallenge *challenge;
SecTrustResultType trustResult;
SecTrustRef trust = challenge.protectionSpace.serverTrust;
OSStatus err = SecTrustEvaluate(trust, &trustResult);
SecCertificateRef certificate = SecGetLeafCertificate(trust); // See Apple docs for implementation of SecGetLeafCertificate