iOS https 证书链获取

- (void)URLSession:(NSURLSession *)session

didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge

 completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition disposition, NSURLCredential *credential))completionHandler

{

if ([self.securityPolicy evaluateServerTrust:challenge.protectionSpace.serverTrust forDomain:challenge.protectionSpace.host])

}

- (BOOL)evaluateServerTrust:(SecTrustRef)serverTrust

                  forDomain:(NSString *)domain

{

NSArray *serverCertificates = AFCertificateTrustChainForServerTrust(serverTrust);

}

static NSArray * AFCertificateTrustChainForServerTrust(SecTrustRef serverTrust) {

    CFIndex certificateCount = SecTrustGetCertificateCount(serverTrust);

    NSMutableArray *trustChain = [NSMutableArray arrayWithCapacity:(NSUInteger)certificateCount];

    for (CFIndex i = 0; i < certificateCount; i++) {

        SecCertificateRef certificate = SecTrustGetCertificateAtIndex(serverTrust, i);

        [trustChain addObject:(__bridge_transfer NSData *)SecCertificateCopyData(certificate)];

    }

    return [NSArray arrayWithArray:trustChain];

}