如何使用 OData 身份验证 (OData Client V7)？

如何解决如何使用 OData 身份验证 (OData Client V7)？

如何在 Microsoft (Microsoft.OData.Client) 的 OData 客户端中使用 Kerberos/NTLM 身份验证（就像在 HttpClient 中一样）？

我正在使用包 Microsoft.OData.Client 7.9.0 并且我正在尝试连接到启用了 https 和身份验证的 OData 端点。但是我无法检索任何数据，而是抛出此异常：

Microsoft.OData.Edm.Csdl.EdmParseException: "Encountered the following errors when parsing the CSDL document: 
XmlError : Root element is missing. : (0,0)"

由于缺乏权限，上下文似乎无法找到请求的资源。这是参考实现：

// Simple data class
public class Person
{
    public string Id { get; set; }
    public string UserName { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

// OData service context
public class Container : DataServiceContext
{
    public DataServiceQuery<Person> People { get; }

    public Container(Uri serviceRoot) : base(serviceRoot)
    {
        People = base.CreateQuery<Person>(nameof(People));

        // This is not working ...
        Credentials = new NetworkCredential("user",@"p@ssw0rd!");
    }
}

Container context = new Container(new Uri("https://targetservice.dev/ODataV4/$metadata"));
var result = context.People.Execute() as QueryOperationResponse<Person>;

向 Credentials 属性提供凭据在这里似乎没有任何影响。

解决方法

经过一段时间的研究和测试，我设法让它发挥了作用。由于缺乏权限，确实无法请求请求的资源 (CSDL)。但是最初可以使用 HttpClient 请求 CSDL，这会考虑提供的凭据：

public class Container : DataServiceContext
{

    public override ICredentials Credentials { get => base.Credentials; set => throw new NotSupportedException(); }
    public bool UseDefaultCredentials { get; }

    public DataServiceQuery<Person> People { get; }

    private static IEdmModel? ParsedModel;

    public Container(Uri serviceRoot,ICredentials? credentials = null,bool useDefaultCredentials = false) : base(serviceRoot)
    {
        if (serviceRoot is null) throw new ArgumentNullException(nameof(serviceRoot));
        base.Credentials = useDefaultCredentials ? credentials ?? CredentialCache.DefaultCredentials : credentials;
        UseDefaultCredentials = useDefaultCredentials;

        People = base.CreateQuery<Person>(nameof(People));

        // It is required to load the service model initially.
        Format.LoadServiceModel = () => RequestModel();
        Format.UseJson();
    }

    // This method requets the service model directly from the OData endpoint via HttpClient.
    // It also uses the supplied credentials.
    private IEdmModel RequestModel()
    {
        if (ParsedModel is not null) return ParsedModel;

        // Create http client (+ handler) populated with credentials.
        using HttpClientHandler clientHandler = new()
        {
            Credentials = UseDefaultCredentials ? CredentialCache.DefaultCredentials : Credentials,CheckCertificateRevocationList = true
        };

        using HttpClient httpClient = new(clientHandler)
        {
            BaseAddress = new UriBuilder()
            {
                Scheme = BaseUri.Scheme,Host = BaseUri.Host,Port = BaseUri.Port
            }.Uri
        };

        // Process the response stream via XmlReader and CsdlReader.
        using var responseStream = httpClient.GetStreamAsync(
            new Uri(Path.Combine(BaseUri.AbsolutePath,"$metadata"),UriKind.Relative))
            .ConfigureAwait(false).GetAwaiter().GetResult();
        using var xmlReader = XmlReader.Create(responseStream);

        if (!CsdlReader.TryParse(xmlReader,out var model,out var errors))
        {
            StringBuilder errorMessages = new();
            foreach (var error in errors) errorMessages.Append(error.ErrorMessage).Append("; ");
            throw new InvalidOperationException(errorMessages.ToString());
        }

        // Return and cache the parsed model.
        return ParsedModel = model;
    }
}

到那时它可以用于以下内容：

Container context = new Container(new Uri("https://targetservice.dev/ODataV4/"),useDefaultCredentials: true);

更新

这似乎是实现中的一个错误，未将凭据信息转发到元数据请求。以下堆栈跟踪显示了 LoadServiceModelFromNetwork 方法的调用：

at Microsoft.OData.Edm.Csdl.CsdlReader.Parse(XmlReader reader)
at Microsoft.OData.Client.DataServiceClientFormat.LoadServiceModelFromNetwork()
at Microsoft.OData.Client.DataServiceClientFormat.get_ServiceModel()
at Microsoft.OData.Client.RequestInfo..ctor(DataServiceContext context)
at Microsoft.OData.Client.DataServiceRequest.CreateExecuteResult(Object source,DataServiceContext context,AsyncCallback callback,Object state,String method)
at Microsoft.OData.Client.DataServiceRequest.Execute[TElement](DataServiceContext context,QueryComponents queryComponents)
at Microsoft.OData.Client.DataServiceQuery`1.Execute()

包中的当前实现如下：

internal IEdmModel LoadServiceModelFromNetwork()
{
    DataServiceClientRequestMessage httpRequest;
    BuildingRequestEventArgs requestEventArgs = null;

    // test hook for injecting a network request to use instead of the default
    if (InjectMetadataHttpNetworkRequest != null)
        // ...
    else
    {
        // ...
        httpRequest = new HttpClientRequestMessage(args);
    }

    // ...

    Task<IODataResponseMessage> asyncResponse =
        Task<IODataResponseMessage>.Factory.FromAsync(httpRequest.BeginGetResponse,httpRequest.EndGetResponse,httpRequest);
    IODataResponseMessage response = asyncResponse.GetAwaiter().GetResult();

    // ...

    using (StreamReader streamReader = new StreamReader(response.GetStream()))
    using (XmlReader xmlReader = XmlReader.Create(streamReader))
    {
        return CsdlReader.Parse(xmlReader);
    }
}

事实证明，这里的 httpRequest 变量负责处理实际响应。构造函数实现如下：

public HttpClientRequestMessage(DataServiceClientRequestMessageArgs args) 
    : base(args.ActualMethod)
{
    _messageStream = new MemoryStream();
    _handler = new HttpClientHandler();
    _client = new HttpClient(_handler,disposeHandler: true);
    _contentHeaderValueCache = new Dictionary<string,string>();
    _effectiveHttpMethod = args.Method;
    _requestUrl = args.RequestUri;
    _requestMessage = new HttpRequestMessage(new HttpMethod(this.ActualMethod),_requestUrl);

    // Now set the headers.
    foreach (KeyValuePair<string,string> keyValue in args.Headers)
    {
            this.SetHeader(keyValue.Key,keyValue.Value);
    }
}

凭据和布尔值 UseDefaultCredentials 都不会转发到 HttpClientHandler。但是 args 提供了此信息。此外，在构造之后不会设置凭据，并且不会检查响应是否存在无效状态代码，因此最终会出现这种奇怪的行为。

在第一次使用容器之前，从外部设置凭据。毕竟，您不希望每次凭据更改时都修改您的 Container。您也不想将用于检索这些凭据的机制硬编码到 Container 中。

假设服务器和客户端都在同一个域中，可以使用 Windows 身份验证作为当前用户进行连接，使用 CredentialCache.DefaultNetworkCredentials

var uri=new Uri("https://targetservice.dev/ODataV4/$metadata");
Container context = new Container(uri){
    Credentials = CredentialCache.DefaultNetworkCredentials
};
var result = context.People.Execute() as QueryOperationResponse<Person>;

如果您想从非域计算机连接或使用不同的帐户，则必须创建一个 NetworkCredential 实例：

var credential = new NetworkCredential("MyDomain","UserName","Password");

Container context = new Container(uri){
    Credentials = credential
};

Windows 身份验证的主要优点是您不需要明确指定凭据。任何远程调用都将使用当前帐户进行。这样就无需存储、更改或泄露密码。这当然假设客户端和服务器都在同一个 Windows 域中，否则服务器将无法识别客户端帐户。

网址错误

异常片段抱怨服务器的响应，而不是身份验证失败。 XmlError : Root element is missing. : (0,0) 表示响应不是一个 XML 文档。这也不是错误响应。如果服务器以 4xx 或 5xx 状态响应，则会引发不同的异常。

服务 URL 错误，不应包含 $metadata 后缀。正如构造函数名称所说的 DataServiceContext(Uri serviceRoot)，URL 应该是服务的根。该 URL 存储在 BaseUriResolver 属性中：

internal DataServiceContext(Uri serviceRoot,ODataProtocolVersion maxProtocolVersion,ClientEdmModel model)
{
     Debug.Assert(model != null,"model != null");
   this.model = model;

   this.baseUriResolver = UriResolver.CreateFromBaseUri(serviceRoot,ServiceRootParameterName);

元数据 URL 由 GetMetadataUri 方法创建，其代码为：

public virtual Uri GetMetadataUri()
{
    // TODO: resolve the location of the metadata endpoint for the service by using an HTTP OPTIONS request
    Uri metadataUri = UriUtil.CreateUri(UriUtil.UriToString(
        this.BaseUriResolver.GetBaseUriWithSlash()) + 
        XmlConstants.UriMetadataSegment,UriKind.Absolute);
    return metadataUri;
}

使用 https://targetservice.dev/ODataV4/$metadata 作为服务 URL 会导致无效的 https://targetservice.dev/ODataV4/$metadata/$metadata 元数据 URL

为了解决此类错误，可以使用 Fiddler 或其他调试代理来拦截 HTTP 调用并检查发送的内容以及服务器实际返回的内容。

如何使用 OData 身份验证 (OData Client V7)？

如何解决如何使用 OData 身份验证 (OData Client V7)？

解决方法

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