使用 NSURLConnection 和 NSURLProtectionSpace 确定信任

Question

我想向 a previously posed question 提出后续问题。我有创建 NSURLRequest/Connection 的代码，运行它并调用用于身份验证的回调方法。具体代码如下：

- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace {
    return [protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust] || [protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodDefault];
}

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

    if ([challenge previousFailureCount] > 0) {
        [[challenge sender] cancelAuthenticationChallenge:challenge];
        NSLog(@"Bad Username Or Password");
        badUsernameAndPassword = YES;
        finished = YES;
        return;
    }

    if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust])
    {
        if (appDelegate._allowInvalidCert)
        {
            // Go ahead...trust me!
            [challenge.sender useCredential:
             [NSURLCredential credentialForTrust: challenge.protectionSpace.serverTrust] 
                 forAuthenticationChallenge: challenge];
        }
        else
        {
            TrustGenerator *tg = [[TrustGenerator alloc] init];

            if ([tg getTrust:challenge.protectionSpace])
            {
                // Go ahead...trust me!
                [challenge.sender useCredential:
                 [NSURLCredential credentialForTrust: challenge.protectionSpace.serverTrust] 
                     forAuthenticationChallenge: challenge];
            }
            else {
                [[challenge sender] cancelAuthenticationChallenge:challenge];
            }
        }
    }
    else if ([[challenge protectionSpace] authenticationMethod] == NSURLAuthenticationMethodDefault) {
        NSURLCredential *newCredential = [NSURLCredential credentialWithUser:_username password:_password persistence:NSURLCredentialPersistenceNone];
        [[challenge sender] useCredential:newCredential forAuthenticationChallenge:challenge];
    }
}

我遇到的是带有“[challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust]”的“didReceiveAuthenticationChallenge”总是被调用，即使我正在尝试服务器上的证书连接到是受信任的（使用 Verisign 证书进行测试）。所以我看到的是我的应用程序总是提示最终用户信任，即使网站是受信任的。考虑到这是一个人在中间攻击时会发生的事情，等等。我真正想要的是这样的代码：

        if (appDelegate._allowInvalidCert)
        {
            // Go ahead...trust me!
            [challenge.sender useCredential:
             [NSURLCredential credentialForTrust: challenge.protectionSpace.serverTrust] 
                 forAuthenticationChallenge: challenge];
        }
        else if(The OS trusts the cert on the server)
        {
             [challenge.sender useCredential:
                 [NSURLCredential credentialForTrust: challenge.protectionSpace.serverTrust] 
                     forAuthenticationChallenge: challenge];
        }
        else{...

Answer 1

所以我花了几天时间研究这个。看起来虽然 NSURLConnection API 无法确定证书是否可信，但安全框架中有一个方法可以处理它。所以这是我想出的代码：

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

    if ([challenge previousFailureCount] > 0) {
        [[challenge sender] cancelAuthenticationChallenge:challenge];
        NSLog(@"Bad Username Or Password");
        badUsernameAndPassword = YES;
        finished = YES;
        return;
    }

    if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust])
    {

        SecTrustResultType result;
        //This takes the serverTrust object and checkes it against your keychain
        SecTrustEvaluate(challenge.protectionSpace.serverTrust, &result);

        if (appDelegate._allowInvalidCert)
        {
            [challenge.sender useCredential:
             [NSURLCredential credentialForTrust: challenge.protectionSpace.serverTrust] 
                 forAuthenticationChallenge: challenge];
        }
        //When testing this against a trusted server I got kSecTrustResultUnspecified every time. But the other two match the description of a trusted server
        else if(result == kSecTrustResultProceed || result == kSecTrustResultConfirm ||  result == kSecTrustResultUnspecified){
            [challenge.sender useCredential:
             [NSURLCredential credentialForTrust: challenge.protectionSpace.serverTrust] 
                 forAuthenticationChallenge: challenge];
        }
        else
        {
            //Asks the user for trust
            TrustGenerator *tg = [[TrustGenerator alloc] init];

            if ([tg getTrust:challenge.protectionSpace])
            {

                //May need to add a method to add serverTrust to the keychain like Firefox's "Add Excpetion"
                [challenge.sender useCredential:
                 [NSURLCredential credentialForTrust: challenge.protectionSpace.serverTrust] 
                     forAuthenticationChallenge: challenge];
            }
            else {
                [[challenge sender] cancelAuthenticationChallenge:challenge];
            }
        }
    }
    else if ([[challenge protectionSpace] authenticationMethod] == NSURLAuthenticationMethodDefault) {
        NSURLCredential *newCredential = [NSURLCredential credentialWithUser:_username password:_password persistence:NSURLCredentialPersistenceNone];
        [[challenge sender] useCredential:newCredential forAuthenticationChallenge:challenge];
    }
}

Answer 2

如果结果是kSecTrustResultConfirm，您实际上应该询问用户它是否是受信任的服务器。

Answer 3

如果您拥有 CA 可信证书，上述答案才有效，因为在这种情况下，您使用的是苹果允许的 CA 证书进行验证。

如果你有自签名证书，你应该使用你自己的 CA 服务器证书来检查它是否有效......

我发现了一个很好的（有点混乱）here。它也涵盖了两次握手....

希望对你有所帮助！