iphone - SecCertificateRef : How to get the certificate information?

Question

我有一个证书 (SecCertificateRef)，我可以检查它是否有效，我可以使用 SecCertificateCopySubjectSummary 提取“摘要”。

“摘要”到底是什么？我不明白术语“包含证书内容的人类可读摘要的字符串”。在苹果文档中。我认为，它们指的是证书中的“CN”，对吗？

有没有什么方法可以从 SecCertificateRef 中获取明确的 X509 信息？强制转换为钥匙串(keychain)对象有帮助吗？

我想要这样的东西，我特别关注“CN”，将其与我提交的 URL 进行比较，以避免中间人攻击。 (或者有什么更好的想法？)

这就是我想要的:

Version: 3 (0x2)
        Serial Number: 1 (0x1)
        Signature Algorithm: md5WithRSAEncryption
        Issuer: C=XY, ST=Austria, L=Graz, O=TrustMe Ltd, OU=Certificate Authority, CN=CA/Email=ca@trustme.dom
        Validity
            Not Before: Oct 29 17:39:10 2000 GMT
            Not After : Oct 29 17:39:10 2001 GMT
        Subject: C=DE, ST=Austria, L=Vienna, O=Home, OU=Web Lab, CN=anywhere.com/Email=xyz@anywhere.com
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
            RSA Public Key: (1024 bit)
                Modulus (1024 bit):
                    00:c4:40:4c:6e:14:1b:61:36:84:24:b2:61:c0:b5:
                    d7:e4:7a:a5:4b:94:ef:d9:5e:43:7f:c1:64:80:fd:
                    9f:50:41:6b:70:73:80:48:90:f3:58:bf:f0:4c:b9:
                    90:32:81:59:18:16:3f:19:f4:5f:11:68:36:85:f6:
                    1c:a9:af:fa:a9:a8:7b:44:85:79:b5:f1:20:d3:25:
                    7d:1c:de:68:15:0c:b6:bc:59:46:0a:d8:99:4e:07:
                    50:0a:5d:83:61:d4:db:c9:7d:c3:2e:eb:0a:8f:62:
                    8f:7e:00:e1:37:67:3f:36:d5:04:38:44:44:77:e9:
                    f0:b4:95:f5:f9:34:9f:f8:43
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Subject Alternative Name:
                email:xyz@anywhere.com
            Netscape Comment:
                mod_ssl generated test server certificate
            Netscape Cert Type:
                SSL Server
    Signature Algorithm: md5WithRSAEncryption
        12:ed:f7:b3:5e:a0:93:3f:a0:1d:60:cb:47:19:7d:15:59:9b:
        3b:2c:a8:a3:6a:03:43:d0:85:d3:86:86:2f:e3:aa:79:39:e7:
        82:20:ed:f4:11:85:a3:41:5e:5c:8d:36:a2:71:b6:6a:08:f9:
        cc:1e:da:c4:78:05:75:8f:9b:10:f0:15:f0:9e:67:a0:4e:a1:
        4d:3f:16:4c:9b:19:56:6a:f2:af:89:54:52:4a:06:34:42:0d:
        d5:40:25:6b:b0:c0:a2:03:18:cd:d1:07:20:b6:e5:c5:1e:21:
        44:e7:c5:09:d2:d5:94:9d:6c:13:07:2f:3b:7c:4c:64:90:bf:
        ff:8e

Answer 1

我等不及悬赏的答案，所以我自己找到了解决方案。正如其他人所说，Security.framework 没有为您提供获取此信息的方法，因此您需要让 OpenSSL 为您解析证书数据:

#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);

其中CertificateGetIssuerName和CertificateGetExpiryDate如下:

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;
}

出于我的目的，我实际上只需要发行人的组织名称和到期日，所以这就是我在下面包含的所有代码。但是，基于此，您应该能够通过阅读 x509.h 头文件来找出其余部分。

编辑:

这是获取证书的方法。我没有放置任何错误处理等。例如，您需要检查 trustResult、err 等。

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