URLSessionTaskDelegate认证挑战函数未触发，求Digest Auth替代方案

一、替代认证方式：预配置凭证到Session配置 #

不需要等挑战代理触发，直接把用户名密码封装成凭证，提前配置给URLSession：

let username = "你的用户名"
let password = "你的密码"
let credential = URLCredential(user: username, password: password, persistence: .forSession)

let config = URLSessionConfiguration.default
// 指定目标设备的防护空间，匹配Digest认证
config.urlCredentialStorage?.set(credential, for: URLProtectionSpace(
    host: "192.168.1.99",
    port: 80,
    protocol: "http",
    realm: nil,
    authenticationMethod: NSURLAuthenticationMethodHTTPDigest
))

let session = URLSession(configuration: config, delegate: self, delegateQueue: nil)
// 正常发起请求即可

原理是提前告知URLSession对应设备的认证信息，即使设备的Digest响应格式略有偏差，Session也会尝试自动匹配使用该凭证。

二、更低层级设置Authentication头：自定义URLProtocol #

如果上面的方法无效，可以通过自定义URLProtocol绕过URLSession对Auth头的限制，完全手动控制请求头：

1. 实现自定义Protocol子类：

class CustomShellyAuthProtocol: URLProtocol {
    override class func canInit(with request: URLRequest) -> Bool {
        // 只处理Shelly设备的请求
        return request.url?.host == "192.168.1.99"
    }

    override class func canonicalRequest(for request: URLRequest) -> URLRequest {
        return request
    }

    override func startLoading() {
        guard let url = request.url else {
            client?.urlProtocol(self, didFailWithError: NSError(domain: "CustomAuth", code: -1, userInfo: [NSLocalizedDescriptionKey: "无效URL"]))
            return
        }

        var mutableRequest = request
        // 填入你在Playground验证有效的Digest Auth头内容
        let authHeader = "Digest username=\"你的用户名\", realm=\"shelly\", nonce=\"...\", uri=\"/relay/0?turn=on&timer=30\", response=\"...\""
        mutableRequest.setValue(authHeader, forHTTPHeaderField: "Authorization")

        let task = URLSession.shared.dataTask(with: mutableRequest) { [weak self] data, response, error in
            guard let self = self else { return }
            if let error = error {
                self.client?.urlProtocol(self, didFailWithError: error)
                return
            }
            if let response = response {
                self.client?.urlProtocol(self, didReceive: response, cacheStoragePolicy: .notAllowed)
            }
            if let data = data {
                self.client?.urlProtocol(self, didLoad: data)
            }
            self.client?.urlProtocolDidFinishLoading(self)
        }
        task.resume()
    }

    override func stopLoading() {}
}

2. 在App启动时注册这个Protocol：

// 比如在AppDelegate的didFinishLaunchingWithOptions方法中
URLProtocol.registerClass(CustomShellyAuthProtocol.self)

这样所有指向Shelly设备的请求都会走自定义逻辑，你可以完全控制HTTP头的设置，不受URLSession的限制。

三、手动触发认证流程（针对设备响应不规范的情况） #

既然httpbin能正常触发代理，说明Shelly设备的401响应可能不符合标准Digest格式，你可以在请求完成回调里手动检查响应，触发认证：

func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
    if let httpResponse = task.response as? HTTPURLResponse, httpResponse.statusCode == 401 {
        if let authHeader = httpResponse.allHeaderFields["WWW-Authenticate"] as? String, authHeader.starts(with: "Digest") {
            // 手动构造凭证并触发认证
            let credential = URLCredential(user: "你的用户名", password: "你的密码", persistence: .forSession)
            task.authenticate(with: credential) { success, error in
                if success {
                    task.resume()
                }
            }
        }
    }
}

内容的提问来源于stack exchange，提问作者MindSpiker