In iOS, how to connect to a server using https with self-signed certificate on the server?

问题

I am developing for iOS 5 and really don't want to use un-ARCed codes so I chose to implement this myself instead of using AFNetworking. Also this might be a big question so I split it into two smaller parts.

1) Connecting to the server using https in iOS 5. I use the codes extracted from "iOS 5 Programming Pushing the Limits" here. Because I am developing for iOS 5 I don't use the deprecated methods in my project. "RNSecTrustEvaluateAsX509" is a method that reevaluates the certificate as a simple X.509 certificate rather than as a part of an SSL handshake.

- (void)connection:(NSURLConnection *)connection willSendRequestForAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
{

    NSURLProtectionSpace *protSpace =  challenge.protectionSpace;
    SecTrustRef trust = protSpace.serverTrust;
    SecTrustResultType result = kSecTrustResultFatalTrustFailure;

    OSStatus status = SecTrustEvaluate(trust, &result);

    if (status == errSecSuccess && result == kSecTrustResultRecoverableTrustFailure) {
        SecCertificateRef cert = SecTrustGetCertificateAtIndex(trust, 0);
        CFStringRef subject = SecCertificateCopySubjectSummary(cert);

        NSLog(@"Trying to access %@. Got %@.", protSpace.host,
              (__bridge id)subject);
        CFRange range = CFStringFind(subject, CFSTR("192.168.1.100"), kCFCompareAnchored|kCFCompareBackwards);
        if (range.location != kCFNotFound) {
            NSLog(@"Creating new trust certificate.Ignoring the hostname.");
            status = RNSecTrustEvaluateAsX509(trust, &result);
        }
        CFRelease(subject);
    }

    if (status == errSecSuccess) {
        switch (result) {
            case kSecTrustResultInvalid:
            case kSecTrustResultDeny:
            case kSecTrustResultFatalTrustFailure:
            case kSecTrustResultOtherError:
            case kSecTrustResultRecoverableTrustFailure: {
                NSLog(@"Failing due to result: %lu", result);
                [challenge.sender cancelAuthenticationChallenge:challenge];
            }

                break;
            case kSecTrustResultProceed:
            case kSecTrustResultUnspecified: {
                NSLog(@"Successing with result: %lu", result);
                NSURLCredential *cred = [NSURLCredential credentialForTrust:trust];
                [challenge.sender useCredential:cred forAuthenticationChallenge:challenge];
            }
                break;
            default:
                NSAssert(NO,@"Unexpected result from trust evaluation: %d", result);
                break;
        }
    }
    else {
        // Something was broken
        NSLog(@"Complete failure with code: %lu", status);
        [challenge.sender cancelAuthenticationChallenge:challenge];
    }

}

It connects to the server but I always get an error saying "The operation couldn't be completed (NSURLErrorDomain error -1012)". And the console shows "Failing due to result 5", which means I get a kSecTrustResultRecoverableTrustFailure. I suspect this is because I am using self-signed certificate on the server. This leads to the second problem as below.

2) Self-signed certificate is causing problems. So I added these lines

// Self-signed certificates need to be validated manually.
NSArray *anchors = [self serverAnchors];

SecTrustSetAnchorCertificates(trust, (__bridge CFArrayRef)anchors);
SecTrustSetAnchorCertificatesOnly(trust, YES);

just before

OSStatus status = SecTrustEvaluate(trust, &result);

in the above willSendRequestForAuthenticationChallenge method. and I also created a method:

- (NSArray *)serverAnchors
{
    static NSArray *anchors = nil;
    if (!anchors) {
        NSData *caData = [CA_CERTS dataUsingEncoding:NSUTF8StringEncoding];
        SecCertificateRef caRef = SecCertificateCreateWithData(kCFAllocatorDefault, (__bridge CFDataRef) caData);

        anchors = [NSArray arrayWithObjects:(__bridge id)caRef,  nil];

        if (caRef) {
            CFRelease(caRef);   
        }
    }

    return anchors;
}

I defined CA_CERTS as the "der" format certificate data, which is a NSString I got from the server via SecCertificateCopyData. But I still keep getting kSecTrustResultRecoverableTrustFailure. I don't really know if I am doing the right thing here. How can I manually validate the self-signed certificate from the server using its own data? More specifically, how to get its data from iOS?

回答1:

I'd suggest to incorporate OpenSSL into your project for handling certificates and authorization challenges! then in your 'connection:didReceiveAuthenticationChallenge:' method of the 'NSURLConnectionDelegate' protocol do something like this:

- (void) connection:(NSURLConnection*) connection didReceiveAuthenticationChallenge: (NSURLAuthenticationChallenge*) challenge {
if ([[[challenge protectionSpace] authenticationMethod] isEqualToString: NSURLAuthenticationMethodServerTrust]) {
    SecTrustRef trust = [[challenge protectionSpace] serverTrust];

    NSMutableArray* certificates = [NSMutableArray array];

    NSData* certificate2Data = // your certificate data
    NSData* certificate3Data = // even more certificate data if needed
    SecCertificateRef certificate2 = SecCertificateCreateWithData(NULL, (CFDataRef) certificate2Data);
    SecCertificateRef certificate3 = SecCertificateCreateWithData(NULL, (CFDataRef) certificate3Data);
    [certificates addObject: (id) certificate2];
    [certificates addObject: (id) certificate3];
    CFRelease(certificate2);
    CFRelease(certificate3);

    SecTrustSetAnchorCertificates(trust, (CFArrayRef) certificates);
    SecTrustSetAnchorCertificatesOnly(trust, true);

    SecTrustResultType      trust_result;
    SecTrustEvaluate(trust, &trust_result);
    if (trust_result == kSecTrustResultUnspecified) {
        if (SecTrustGetCertificateCount(trust) > 0) {
            SecCertificateRef leafCertificate = SecTrustGetCertificateAtIndex(trust, 0);

            NSData* leafCertificateData = (NSData*) SecCertificateCopyData(leafCertificate);

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

            CFRelease(leafCertificateData);

            X509_NAME *issuerX509Name = X509_get_issuer_name(certificateX509);
            X509_NAME *subjectX509Name = X509_get_subject_name(certificateX509);

            /*
             with issuerX509Name and subjectX509Name you could check some properties of the certificate and cancel the 
             authentication challenge f.e.!

             if ([[self valueWithKey: @"CN" inName: subjectX509Name cert: certificateX509] isEqualToString: @"xxxx"] == NO) {
                [[challenge sender] cancelAuthenticationChallenge: challenge];
                return;
             }


            */

            NSURLCredential* credential = [NSURLCredential credentialForTrust: trust];
            [[challenge sender] useCredential: credential forAuthenticationChallenge: challenge];
        } else {
            [[challenge sender] cancelAuthenticationChallenge: challenge];
        }
    } else {
        [[challenge sender] cancelAuthenticationChallenge: challenge];
    }
}}

来源：https://stackoverflow.com/questions/12049508/in-ios-how-to-connect-to-a-server-using-https-with-self-signed-certificate-on-t