103 lines
4.5 KiB
C#
103 lines
4.5 KiB
C#
using System;
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using System.Security.Cryptography;
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using System.Text;
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using System.Xml;
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namespace CinemaLib.Webshare;
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public static class LinkGenerator
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{
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internal static readonly Uri WebshareApiUri = new Uri("https://webshare.cz/api/");
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/// <summary>
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/// Generates a download link for the given Webshare download.
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/// </summary>
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/// <param name="fileId">Webshare file identifier.</param>
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/// <param name="fileName">Webshare file name.</param>
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/// <param name="session">Optional session to get a VIP link.</param>
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/// <param name="cancel">Asynchronous cancellation.</param>
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/// <returns>Time-limited download link.</returns>
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public async static Task<Uri> GenerateDownloadLinkAsync(string fileId, string fileName, Session? session, CancellationToken cancel)
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{
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// Obtain the download password salt
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// Example response: <?xml version="1.0" encoding="UTF-8"?><response><status>OK</status><salt>UX8y8Fpa</salt><app_version>30</app_version></response>
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Uri saltUri = new Uri(WebshareApiUri, "file_password_salt/");
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HttpResponseMessage saltRes = await Program._http.PostAsync(saltUri, new FormUrlEncodedContent(new[] { new KeyValuePair<string, string>("ident", fileId) }), cancel);
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if (!saltRes.IsSuccessStatusCode)
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throw new IOException("Failed to get password salt from Webshare API.");
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XmlReader saltR = XmlReader.Create(saltRes.Content.ReadAsStream());
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saltR.ReadStartElement("response");
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Exception? e = saltR.GetExceptionIfStatusNotOK(out string? code);
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string password;
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if (e != null)
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{
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if (code == "FILE_PASSWORD_SALT_FATAL_2")
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{
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// No password is set
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password = "";
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}
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else
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throw e;
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}
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else
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{
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// Calculate the download password
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string salt = saltR.ReadElementContentAsString("salt", "");
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saltR.ReadElementContentAsString("app_version", "");
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saltR.ReadEndElement(); // response
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password = CalculatePassword(fileId, fileName, salt);
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}
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// Obtain the download link
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// 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>
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Uri linkUri = new Uri(WebshareApiUri, "file_link/");
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HttpResponseMessage linkRes = await Program._http.PostAsync(linkUri, new FormUrlEncodedContent(new[] {
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new KeyValuePair<string, string>("ident", fileId),
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new KeyValuePair<string, string>("download_type", "video_stream"),
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new KeyValuePair<string, string>("device_uuid", Guid.NewGuid().ToString("X")),
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new KeyValuePair<string, string>("device_res_x", "3840"),
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new KeyValuePair<string, string>("device_res_y", "2160"),
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new KeyValuePair<string, string>("password", password),
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new KeyValuePair<string, string>(Session.TokenKeyName, (session != null ? await session.GetTokenAsync(cancel) : null) ?? ""),
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}), cancel
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);
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if (!linkRes.IsSuccessStatusCode)
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throw new IOException("Failed to get download link from Webshare API.");
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XmlReader linkR = XmlReader.Create(linkRes.Content.ReadAsStream());
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linkR.ReadStartElement("response");
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linkR.ThrowIfStatusNotOK();
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string link = linkR.ReadElementContentAsString("link", "");
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linkR.ReadElementContentAsString("app_version", "");
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linkR.ReadEndElement(); // response
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return new Uri(link);
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}
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/// <summary>
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/// Calculates the Webshare download password from file identifier, name and salt.
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/// </summary>
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/// <param name="fileId">Webshare file identifier.</param>
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/// <param name="fileName">Webshare file name.</param>
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/// <param name="salt">Download salt obtained from https://webshare.cz/api/file_password_salt/.</param>
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/// <returns>Password to use to obtain a download link using https://webshare.cz/api/file_link/.</returns>
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private static string CalculatePassword(string fileId, string fileName, string salt)
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{
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if (fileId == null || fileName == null || salt == null)
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throw new ArgumentNullException();
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// Example
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// name = "bIaFGdkvKiiTBo2_S3E"
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// id = "12kRBqAYQS2"
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// password = sha256(name + id) = "1e98873b57b7660cba7267c191f2d1fb7d198d062eb2fe0686502883042c4105"
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// crypt = md5crypt(password, salt: "UX8y8Fpa") = "$1$UX8y8Fpa$stY.bUYGBsmAlc6IIxnHU0"
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// result = sha1(crypt) = "8ceff8e5abf9aa375a8a5b05871b6cd6fb7fd185")
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string toHash = fileName + fileId;
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byte[] password = SHA256.HashData(Encoding.UTF8.GetBytes(toHash));
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string passwordS = Convert.ToHexString(password).ToLowerInvariant();
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return passwordS.HashPassword(salt);
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}
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}
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