Webshare file download URL generator from file id and name

Program.cs

@@ -3,9 +3,13 @@ using JellyfinCinemaStream.Webshare;
 
 class Program
 {
-  private static void Main(string[] args)
+  public static HttpClient _http = new HttpClient();
+
+  private static async Task Main(string[] args)
   {
-    string a = LinkGenerator.CalculatePassword(downloadId: "12kRBqAYQS2", downloadName: "bIaFGdkvKiiTBo2_S3E", salt: "UX8y8Fpa");
+    CancellationToken cancel = default;
+    //string a = LinkGenerator.CalculatePassword(fileId: "2kRBqAYQS2", fileName: "bIaFGdkvKiiTBo2_S3E1", salt: "UX8y8Fpa");
+    Uri a = await LinkGenerator.GenerateDownloadLinkAsync(fileId: "2kRBqAYQS2", fileName: "bIaFGdkvKiiTBo2_S3E1", cancel);
     Console.WriteLine(a);
   }
 }

Webshare/LinkGenerator.cs

@@ -1,23 +1,86 @@
 using System;
 using System.Security.Cryptography;
 using System.Text;
+using System.Xml;
 
 namespace JellyfinCinemaStream.Webshare;
 
 public class LinkGenerator
 {
   private static readonly BaseEncoding UnixMD5 = new BaseEncoding("./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz", false);
+  private static readonly Uri WebshareApiUri = new Uri("https://webshare.cz/api/");
+  
+  /// <summary>
+  /// Generates a download link for the given Webshare download.
+  /// </summary>
+  /// <param name="fileId">Webshare file identifier.</param>
+  /// <param name="fileName">Webshare file name.</param>
+  /// <param name="cancel">Asynchronous cancellation.</param>
+  /// <returns>Time-limited download link.</returns>
+  public async static Task<Uri> GenerateDownloadLinkAsync(string fileId, string fileName, CancellationToken cancel)
+  {
+    // Obtain the download password salt
+    // Example response: <?xml version="1.0" encoding="UTF-8"?><response><status>OK</status><salt>UX8y8Fpa</salt><app_version>30</app_version></response>
+    Uri saltUri = new Uri(WebshareApiUri, "file_password_salt/");
+    HttpResponseMessage saltRes = await Program._http.PostAsync(saltUri, new FormUrlEncodedContent(new [] { new KeyValuePair<string, string>("ident", fileId) }), cancel);
+    if (!saltRes.IsSuccessStatusCode)
+      throw new IOException("Failed to get password salt from Webshare API.");
+
+    XmlReader saltR = XmlReader.Create(saltRes.Content.ReadAsStream());
+    saltR.ReadStartElement("response");
+    ThrowIfStatusNotOK(saltR);
+    string salt = saltR.ReadElementContentAsString("salt", "");
+    saltR.ReadElementContentAsString("app_version", "");
+    saltR.ReadEndElement(); // response
+
+    // Calculate the download password
+    string password = CalculatePassword(fileId, fileName, salt);
+
+    // Obtain the download link
+    // Example response: <?xml version="1.0" encoding="UTF-8"?><response><status>OK</status><link>https://free.19.dl.wsfiles.cz/9209/...</link><app_version>30</app_version></response>
+    Uri linkUri = new Uri(WebshareApiUri, "file_link/");
+    HttpResponseMessage linkRes = await Program._http.PostAsync(linkUri, new FormUrlEncodedContent(new [] { 
+      new KeyValuePair<string, string>("ident", fileId),
+      new KeyValuePair<string, string>("download_type", "video_stream"),
+      new KeyValuePair<string, string>("device_uuid", Guid.NewGuid().ToString("X")),
+      new KeyValuePair<string, string>("device_res_x", "3840"),
+      new KeyValuePair<string, string>("device_res_y", "2160"),
+      new KeyValuePair<string, string>("password", password),
+      }), cancel
+    );
+    if (!linkRes.IsSuccessStatusCode)
+      throw new IOException("Failed to get download link from Webshare API.");
+
+    XmlReader linkR = XmlReader.Create(linkRes.Content.ReadAsStream());
+    linkR.ReadStartElement("response");
+    ThrowIfStatusNotOK(linkR);
+    string link = linkR.ReadElementContentAsString("link", "");
+    linkR.ReadElementContentAsString("app_version", "");
+    linkR.ReadEndElement(); // response
+
+    return new Uri(link);
+  }
+
+  private static void ThrowIfStatusNotOK(XmlReader r) {
+    string status = r.ReadElementContentAsString("status", "");
+    if (status == "OK")
+      return;
+
+    string code = r.ReadElementContentAsString("code", "");
+    string message = r.ReadElementContentAsString("message", "");
+    throw new IOException(code + ": " + message);
+  }
 
   /// <summary>
-  /// Calculates the Webshare download password from download identifier, name and salt.
+  /// Calculates the Webshare download password from file identifier, name and salt.
   /// </summary>
-  /// <param name="downloadId">Webshare download identifier.</param>
+  /// <param name="fileId">Webshare file identifier.</param>
-  /// <param name="downloadName">Webshare download name.</param>
+  /// <param name="fileName">Webshare file name.</param>
   /// <param name="salt">Download salt obtained from https://webshare.cz/api/file_password_salt/.</param>
   /// <returns>Password to use to obtain a download link using https://webshare.cz/api/file_link/.</returns>
-  public static string CalculatePassword(string downloadId, string downloadName, string salt)
+  private static string CalculatePassword(string fileId, string fileName, string salt)
   {
-    if (downloadId == null || downloadName == null || salt == null)
+    if (fileId == null || fileName == null || salt == null)
       throw new ArgumentNullException();
 
     // Example
@@ -26,7 +89,7 @@ public class LinkGenerator
     //  password = sha256(name + id) = "1e98873b57b7660cba7267c191f2d1fb7d198d062eb2fe0686502883042c4105"
     //  crypt = md5crypt(password, salt: "UX8y8Fpa") = "$1$UX8y8Fpa$stY.bUYGBsmAlc6IIxnHU0"
     //  result = sha1(crypt) = "8ceff8e5abf9aa375a8a5b05871b6cd6fb7fd185")
-    string toHash = downloadName + downloadId;
+    string toHash = fileName + fileId;
     byte[] password = SHA256.HashData(Encoding.UTF8.GetBytes(toHash));
     string passwordS = Convert.ToHexStringLower(password);
     string crypt = MD5Crypt(passwordS, salt);