NSUrlSession NSUrlConnection https连接时证书无效的解决办法

The certificate for this server is invalid
最近公司项目需要从网络端获取部分数据，原来的接口是http的，iOS9引入的ATS机制：
所有的http请求都改成了https，采用TLS 1.2协议，目的是增强数据安全。如果不更新的话，暂时可以在Info.plist中声明，使用不安全的网络请求。首先我们在info.plist中加入以下参数：

<key>NSAppTransportSecuritykey>
<dict>
    <key>NSAllowsArbitraryLoadskey>
    <true/>
dict>

然后使用下面代码可以获取到数据：

- (NSDictionary *)postToserver:(NSURL *)address paramers:(NSDictionary *)param {
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:address];
    [request setHTTPMethod:@"POST"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];

    NSData *data = [NSJSONSerialization dataWithJSONObject:param options:NSJSONWritingPrettyPrinted error:nil];
    [request setHTTPBody:data];

    NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]];

    __block NSDictionary *tempResult = nil;
    dispatch_semaphore_t sem = dispatch_semaphore_create(0);
    NSURLSessionDataTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        if (error == nil) {
            NSDictionary *result = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:nil];
            tempResult = result;
        } 
        dispatch_semaphore_signal(sem);
    }];

    [task resume];
    dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
    return tempResult;
}

这样就项目就支持http了，但是切换到HTTPS又有问题了。

切换到HTTPS

App Transport Security要求TLS 1.2而且它要求站点使用支持forward secrecy协议的密码。证书也要求是符合ATS规格的。因此慎重检查与你的应用交互的服务器是不是符合ATS的要求非常重要。但是有的时候小公司证书(你懂的~~~),所以我们需要在API检测证书是否有效的时候过滤掉我们的server。如果不这样操作，会出现以下错误：

Error Domain=NSURLErrorDomain Code=-1202 "The certificate for this server is invalid. You might be connecting to a server that is pretending to be “s3.amazonaws.com” which could put your confidential information at risk." UserInfo=0x20007030 {NSErrorFailingURLStringKey=https://s3.amazonaws.com/.../test.jpeg, NSLocalizedRecoverySuggestion=Would you like to connect to the server anyway?, NSErrorFailingURLKey=https://s3.amazonaws.com/.../test.jpeg, NSLocalizedDescription=The certificate for this server is invalid. You might be connecting to a server that is pretending to be “s3.amazonaws.com” which could put your confidential information at risk., NSUnderlyingError=0x20014d40 "The certificate for this server is invalid. You might be connecting to a server that is pretending to be “s3.amazonaws.com” which could put your confidential information at risk.", NSURLErrorFailingURLPeerTrustErrorKey=}

解决方法

1： 使用NSURLConnection
如果你使用的是NSURLConnection,需要实现NSURLConnectionDelegate方法:

-(void)connection:(NSURLConnection *)connection willSendRequestForAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
{
   if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust] &&
       [challenge.protectionSpace.host hasSuffix:@"example.com"])
   {
       // 不管证书是否有效都使用
       [challenge.sender useCredential:[NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust] forAuthenticationChallenge:challenge];
   }
   else
   {
       [challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge];
   }
}

2： 使用NSURLSession
如果使用的是NSURLSession进行网络链接，同样需要实现NSURLSessionDelegate方法：

#pragma mark -session delegate
-(void)URLSession:(NSURLSession *)session didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition, NSURLCredential * _Nullable))completionHandler {

    NSURLSessionAuthChallengeDisposition disposition = NSURLSessionAuthChallengePerformDefaultHandling;
    __block NSURLCredential *credential = nil;

    if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust] && [challenge.protectionSpace.host hasSuffix:@"example.com"]) {
        credential = [NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust];
        if (credential) {
            disposition = NSURLSessionAuthChallengeUseCredential;
        } else {
            disposition = NSURLSessionAuthChallengePerformDefaultHandling;
        }
    } else {
        disposition = NSURLSessionAuthChallengePerformDefaultHandling;
    }

    if (completionHandler) {
        completionHandler(disposition, credential);
    }
}

OK，解决问题。

注意

代码里面[challenge.protectionSpace.host hasSuffix:@”example.com”]这句判断是根据实际情况来使用，如果你想过滤掉所有的，去掉这段代码即可。