VB.NET WebRequest 不检索任何内容

Posted 2023-02-15

【中文标题】VB.NET WebRequest 不检索任何内容

【英文标题】：VB.NET WebRequest Retrieves No Content

【发布时间】：2021-12-30 15:23:27

【问题描述】：

我正在处理一个 VB.NET 项目 (Outlook VSTO)，我想通过其API 从 Cisco AMP 获取数据。我面临的问题是，虽然我可以成功验证，并且收到 200 状态码，但响应的内容长度始终为 -1，无论我从 API 请求什么信息，我得到的内容始终是这个:

我知道这是我的 VB.NET 代码的问题，因为我能够使用 Python 请求检索实际信息，只需 2 行代码，绝对没有问题。根据 Cisco AMP 的文档，有两种方法可以访问 api：通过 https://APIGUID:[e-mail]/v1/requestedinformation 或通过http://example.com/v1/requestedinformation 使用 base64 编码的标头中指定的凭据（RFC 1945 ）。我可以从这两种方法中的任何一种方法中使用 Python 获取正确的信息，但到目前为止，它们都不适用于 VB.NET。

这是我在 VB.NET 中尝试过的两个主要解决方案，但请记住，我在我尝试过的每个解决方案中都尝试了这两种连接方法。

尝试 1 使用 WebClient：

    Public Sub Test()
        Dim url As String = "https://" & apiID & ":" & apiKey & "@" & "api.amp.cisco.com/v1/computers"
        MsgBox(url) 'Just to make sure I have the URL properly formatted

        'These two lines are needed to avoid SSL validation. 
        'The network I am working on this from sits behind a proxy for logging reasons,
        'so the certificate will not match the domain. This is 100% necessary.
        Net.ServicePointManager.ServerCertificateValidationCallback = New Net.Security.RemoteCertificateValidationCallback(Function() True)
        Net.ServicePointManager.SecurityProtocol = Net.SecurityProtocolType.Tls12
        
        'I have tried with the Uri data type as well as the url in String format
        Dim uri As Uri = New Uri(url)
        Dim request As Net.WebClient = New Net.WebClient

        'Headers, I copied them verbatim from Python since Python was able to get
        'the response content
        request.Headers.Add("Accept", "*/*") 'I have also tried application/json here
        request.Headers.Add("User-Agent", "python-requests/2.26.0")
        request.Credentials = New Net.NetworkCredential(apiID, apiKey)
        request.Headers.Add("Authorization", "Basic base64string") 'removed the actual base 64 string for privacy reasons, the actual string is in my code.
        request.Headers.Add("Accept-Encoding", "gzip, deflate")

        'I have tried DownloadData as well as DownloadString
        Dim htmlResponse As String = System.Text.Encoding.UTF8.GetString(request.DownloadData(uri))

        'Just using this mail item to display the response content
        Dim mail As Outlook.MailItem = Me.Application.CreateItem(Outlook.OlItemType.olMailItem)
        mail.HTMLBody = htmlResponse

        mail.Display()
    End Sub

尝试 2 使用 HTTPWebRequest：

    Public Sub Test()
        Dim url As String = "https://" & apiID & ":" & apiKey & "@" & "api.amp.cisco.com/v1/computers"
        MsgBox(url)

        'These two lines are needed to avoid SSL validation. 
        'The network I am working on this from sits behind a proxy for logging reasons,
        'so the certificate will not match the domain. This is 100% necessary.
        Net.ServicePointManager.ServerCertificateValidationCallback = New Net.Security.RemoteCertificateValidationCallback(Function() True)
        Net.ServicePointManager.SecurityProtocol = Net.SecurityProtocolType.Tls12

        'Headers, I copied them verbatim from Python since Python was able to get
        'the response content
        Dim uri As Uri = New Uri(url)
        Dim cookies As Net.CookieContainer = New Net.CookieContainer()
        Dim request As Net.HttpWebRequest = Net.HttpWebRequest.Create(uri)
        request.CookieContainer = cookies
        request.ServicePoint.Expect100Continue = False
        request.Accept = "*/*" 'I have also tried application/json here
        request.UserAgent = "python-requests/2.26.0"
        request.KeepAlive = True
        request.Credentials = New Net.NetworkCredential(apiID, apiKey)
        request.PreAuthenticate = True
        request.Headers.Add("Authorization", "Basic base64string")
        request.Headers.Add("Accept-Encoding", "gzip, deflate")

        Dim response As Net.HttpWebResponse = request.GetResponse()
        Dim reader As StreamReader = New StreamReader(response.GetResponseStream())
        Dim htmlResponse As String = reader.ReadToEnd()

        MsgBox(response.StatusCode)

        'Just using this mail item to display the response content
        Dim mail As Outlook.MailItem = Me.Application.CreateItem(Outlook.OlItemType.olMailItem)
        mail.HTMLBody = htmlResponse

        mail.Display()
    End Sub

在过去的几个小时里，我一直在抨击这一点，我现在没有想法。我是在做一些愚蠢的事情，还是有一些我不知道的 VB.NET 限制？

【问题讨论】：

请修剪您的代码，以便更容易找到您的问题。请按照以下指南创建minimal reproducible example。

【参考方案1】：

事实证明，解决方案非常简单。以上任何一种都可以，我只需要删除Accept-Encoding 标头即可。

请注意，我首先添加它是因为：

Cisco AMP 的 API 声明需要 Accept-Encoding: gzip 标头 Python 使用了准确的标头并能够检索数据

真的不知道为什么会这样，但无论如何，它现在可以工作了。