Merge pull request #4 from Franciskid/server-minted-guest-sessions

Stop storing guest passwords, mint sessions server side

Jellyfin.Plugin.ShareLinks/Models/ShareLinkRecord.cs

@@ -56,9 +56,6 @@ public sealed class ShareLinkRecord
     /// <summary>Gets or sets a value indicating whether the link may be used once only.</summary>
     public bool OneUse { get; set; } = true;
 
-    /// <summary>Gets or sets the encrypted guest password, if one has been generated.</summary>
-    public string? GuestPasswordEncrypted { get; set; }
-
     /// <summary>Gets or sets a value indicating whether metadata was touched during cleanup.</summary>
     public bool MetadataTouched { get; set; }
 

Jellyfin.Plugin.ShareLinks/Services/ShareLinkRedemptionService.cs

@@ -4,8 +4,10 @@ using System.Threading;
 using System.Threading.Tasks;
 using Jellyfin.Plugin.ShareLinks.Models;
 using Jellyfin.Plugin.ShareLinks.Storage;
+using MediaBrowser.Controller.Authentication;
 using MediaBrowser.Controller.Entities;
 using MediaBrowser.Controller.Library;
+using MediaBrowser.Controller.Session;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Logging;
 
@@ -20,6 +22,7 @@ public sealed class ShareLinkRedemptionService
     private readonly ItemTagService _itemTagService;
     private readonly JellyfinGuestUserService _guestUserService;
     private readonly ShareLinkCleanupService _cleanupService;
+    private readonly ISessionManager _sessionManager;
     private readonly ILogger<ShareLinkRedemptionService> _logger;
 
     /// <summary>Initializes a new instance of the <see cref="ShareLinkRedemptionService"/> class.</summary>
@@ -30,6 +33,7 @@ public sealed class ShareLinkRedemptionService
         ItemTagService itemTagService,
         JellyfinGuestUserService guestUserService,
         ShareLinkCleanupService cleanupService,
+        ISessionManager sessionManager,
         ILogger<ShareLinkRedemptionService> logger)
     {
         _libraryManager = libraryManager;
@@ -38,6 +42,7 @@ public sealed class ShareLinkRedemptionService
         _itemTagService = itemTagService;
         _guestUserService = guestUserService;
         _cleanupService = cleanupService;
+        _sessionManager = sessionManager;
         _logger = logger;
     }
 
@@ -101,17 +106,33 @@ public sealed class ShareLinkRedemptionService
         record.CleanupError = null;
         await _store.UpdateAsync(record, cancellationToken).ConfigureAwait(false);
 
-        var password = await GetOrCreatePasswordAsync(record, cancellationToken).ConfigureAwait(false);
+        // The account still needs a password so it can never be authenticated with a blank
+        // login; it is generated fresh on every redemption and is never stored or sent
+        // anywhere. The browser only ever receives a server-minted session token.
+        var password = JellyfinGuestUserService.GeneratePassword();
         if (string.IsNullOrWhiteSpace(record.GuestUserName))
         {
             record.GuestUserName = JellyfinGuestUserService.BuildGuestUsername(record);
         }
 
+        AuthenticationResult authResult;
         try
         {
             var user = await _guestUserService.EnsureGuestUserAsync(record, password, cancellationToken).ConfigureAwait(false);
             record.GuestUserId = user.Id;
             record.GuestUserName = user.Username;
+
+            authResult = await _sessionManager.AuthenticateDirect(new AuthenticationRequest
+            {
+                Username = record.GuestUserName,
+                UserId = record.GuestUserId.Value,
+                App = "ShareLinks",
+                AppVersion = "1.0.0",
+                DeviceId = record.DeviceId,
+                DeviceName = "ShareLinks",
+                RemoteEndPoint = request.HttpContext.Connection.RemoteIpAddress?.ToString()
+            }).ConfigureAwait(false);
+
             record.RedeemedAtUtc ??= now;
             record.Status = ShareLinkStatus.Redeemed;
             record.CleanupError = null;
@@ -127,29 +148,7 @@ public sealed class ShareLinkRedemptionService
             return null;
         }
 
-        return BuildBootstrapHtml(request, record, password, itemId);
+        return BuildBootstrapHtml(request, authResult, itemId);
-    }
-
-    private async Task<string> GetOrCreatePasswordAsync(ShareLinkRecord record, CancellationToken cancellationToken)
-    {
-        if (!string.IsNullOrWhiteSpace(record.GuestPasswordEncrypted))
-        {
-            try
-            {
-                return await _tokenService.UnprotectStringAsync(record.GuestPasswordEncrypted, cancellationToken).ConfigureAwait(false);
-            }
-            catch (Exception ex)
-            {
-                _logger.LogWarning(ex, "ShareLinks: stored guest password could not be decrypted for record {RecordId}; generating a replacement.", record.Id);
-            }
-        }
-
-        var password = JellyfinGuestUserService.GeneratePassword();
-        record.GuestPasswordEncrypted = await _tokenService.ProtectStringAsync(password, cancellationToken).ConfigureAwait(false);
-        record.Status = ShareLinkStatus.Redeeming;
-        record.CleanupError = null;
-        await _store.UpdateAsync(record, cancellationToken).ConfigureAwait(false);
-        return password;
     }
 
     private async Task HandleTerminalRecordAsync(ShareLinkRecord record, ShareLinkStatus terminalStatus, string reason, CancellationToken cancellationToken)
@@ -180,24 +179,14 @@ public sealed class ShareLinkRedemptionService
         }
     }
 
-    private static string BuildBootstrapHtml(HttpRequest request, ShareLinkRecord record, string password, Guid itemId)
+    private static string BuildBootstrapHtml(HttpRequest request, AuthenticationResult authResult, Guid itemId)
     {
         var pathBase = request.PathBase.Value ?? string.Empty;
-        var authUrl = $"{pathBase}/Users/AuthenticateByName";
         var redirectUrl = $"{pathBase}/web/index.html#/details?id={Uri.EscapeDataString(itemId.ToString("D"))}";
-        var username = record.GuestUserName ?? JellyfinGuestUserService.BuildGuestUsername(record);
-        var deviceId = record.DeviceId ?? string.Empty;
 
-        var authJson = JsonSerializer.Serialize(new
+        var accessTokenJson = JsonSerializer.Serialize(authResult.AccessToken);
-        {
+        var userIdJson = JsonSerializer.Serialize(authResult.User.Id.ToString("N"));
-            Username = username,
-            Pw = password
-        });
-
-        var authUrlJson = JsonSerializer.Serialize(authUrl);
         var redirectUrlJson = JsonSerializer.Serialize(redirectUrl);
-        var usernameJson = JsonSerializer.Serialize(username);
-        var deviceIdJson = JsonSerializer.Serialize(deviceId);
         var infoUrlJson = JsonSerializer.Serialize($"{pathBase}/System/Info/Public");
         var pathBaseJson = JsonSerializer.Serialize(pathBase);
 
@@ -221,31 +210,11 @@ public sealed class ShareLinkRedemptionService
 </main>
 <script>
 (async () => {
-  const authUrl = {{authUrlJson}};
   const redirectUrl = {{redirectUrlJson}};
-  const username = {{usernameJson}};
+  const accessToken = {{accessTokenJson}};
-  const deviceId = {{deviceIdJson}} || crypto.randomUUID().replace(/-/g, "");
+  const userId = {{userIdJson}};
 
-  document.getElementById("status").textContent = "Authenticating " + username + ".";
+  document.getElementById("status").textContent = "Opening your title.";
-
-  const response = await fetch(authUrl, {
-    method: "POST",
-    credentials: "same-origin",
-    headers: {
-      "Content-Type": "application/json",
-      "Accept": "application/json",
-      "X-Emby-Authorization": `MediaBrowser Client="ShareLinks", Device="ShareLinks", DeviceId="${deviceId}", Version="1.0.0"`
-    },
-    body: JSON.stringify({{authJson}})
-  });
-
-  if (!response.ok) {
-    throw new Error(`Authentication failed (${response.status})`);
-  }
-
-  const auth = await response.json();
-  const accessToken = auth.AccessToken ?? auth.accessToken ?? "";
-  const userId = auth.User?.Id ?? auth.user?.Id ?? auth.UserId ?? auth.userId ?? "";
 
   const info = await fetch({{infoUrlJson}}, {
     credentials: "same-origin",

Jellyfin.Plugin.ShareLinks/Services/ShareTokenService.cs

@@ -88,61 +88,6 @@ public sealed class ShareTokenService
             Encoding.UTF8.GetBytes(expectedHash));
     }
 
-    /// <summary>Encrypts sensitive text using the shared plugin secret.</summary>
-    public async Task<string> ProtectStringAsync(string value, CancellationToken cancellationToken = default)
-    {
-        if (value is null)
-        {
-            throw new ArgumentNullException(nameof(value));
-        }
-
-        var secret = await GetSecretAsync(cancellationToken).ConfigureAwait(false);
-        var plaintext = Encoding.UTF8.GetBytes(value);
-        var nonce = new byte[12];
-        RandomNumberGenerator.Fill(nonce);
-        var cipher = new byte[plaintext.Length];
-        var tag = new byte[16];
-
-        using (var aes = new AesGcm(secret, 16))
-        {
-            aes.Encrypt(nonce, plaintext, cipher, tag);
-        }
-
-        var payload = new byte[nonce.Length + cipher.Length + tag.Length];
-        Buffer.BlockCopy(nonce, 0, payload, 0, nonce.Length);
-        Buffer.BlockCopy(cipher, 0, payload, nonce.Length, cipher.Length);
-        Buffer.BlockCopy(tag, 0, payload, nonce.Length + cipher.Length, tag.Length);
-        return Base64UrlEncode(payload);
-    }
-
-    /// <summary>Decrypts a sensitive string protected by <see cref="ProtectStringAsync"/>.</summary>
-    public async Task<string> UnprotectStringAsync(string protectedValue, CancellationToken cancellationToken = default)
-    {
-        if (string.IsNullOrWhiteSpace(protectedValue))
-        {
-            throw new ArgumentException("Protected value cannot be empty.", nameof(protectedValue));
-        }
-
-        var payload = Base64UrlDecode(protectedValue);
-        if (payload.Length < 12 + 16)
-        {
-            throw new CryptographicException("Protected payload is invalid.");
-        }
-
-        var secret = await GetSecretAsync(cancellationToken).ConfigureAwait(false);
-        var nonce = payload[..12];
-        var tag = payload[^16..];
-        var cipher = payload[12..^16];
-        var plaintext = new byte[cipher.Length];
-
-        using (var aes = new AesGcm(secret, 16))
-        {
-            aes.Decrypt(nonce, cipher, tag, plaintext);
-        }
-
-        return Encoding.UTF8.GetString(plaintext);
-    }
-
     private async Task<byte[]> GetSecretAsync(CancellationToken cancellationToken)
     {
         if (_secretKey is not null)

Jellyfin.Plugin.ShareLinks/Tasks/CleanupShareLinksScheduledTask.cs

@@ -8,7 +8,8 @@ using MediaBrowser.Model.Tasks;
 namespace Jellyfin.Plugin.ShareLinks.Tasks;
 
 /// <summary>
-/// Scheduled cleanup shell for later link-expiry and guest-account teardown work.
+/// Scheduled task that expires share links past their <c>ExpiresAtUtc</c> and tears down
+/// the associated guest users and tags.
 /// </summary>
 public sealed class CleanupShareLinksScheduledTask : IScheduledTask, IConfigurableScheduledTask
 {
@@ -27,7 +28,7 @@ public sealed class CleanupShareLinksScheduledTask : IScheduledTask, IConfigurab
     public string Key => "ShareLinksCleanup";
 
     /// <inheritdoc />
-    public string Description => "Removes expired share links and performs future guest-account cleanup.";
+    public string Description => "Expires share links past their expiry time and removes their guest users and tags.";
 
     /// <inheritdoc />
     public string Category => "ShareLinks";
@@ -53,8 +54,8 @@ public sealed class CleanupShareLinksScheduledTask : IScheduledTask, IConfigurab
     {
         yield return new TaskTriggerInfo
         {
-            Type = TaskTriggerInfoType.DailyTrigger,
+            Type = TaskTriggerInfoType.IntervalTrigger,
-            TimeOfDayTicks = TimeSpan.FromHours(4).Ticks,
+            IntervalTicks = TimeSpan.FromMinutes(30).Ticks,
         };
     }
 }

README.md

@@ -87,6 +87,13 @@ up the link. So:
 6. the real access boundary is the server-side tag policy; the web-client
    lockdown is convenience on top of it
 
+The same applies to the guest's login. The plugin mints the guest session itself
+on the server, using Jellyfin's own session manager. No password is ever stored
+anywhere, not even encrypted, and no password ever appears in the page sent to
+the guest. The only thing the guest's browser receives is a session token
+scoped to that one guest account, and that token dies the moment the guest
+account is cleaned up.
+
 ## Configuration
 
 All of these live on the plugin's dashboard page: