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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Buffers;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using Microsoft.AspNetCore.Components.Server.Circuits;
using Microsoft.AspNetCore.DataProtection;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.SignalR;
using Microsoft.Extensions.Logging;
namespace Microsoft.AspNetCore.Components.Server;
// Some notes about our expectations for error handling:
//
// In general, we need to prevent any client from interacting with a circuit that's in an unpredictable
// state. This means that when a circuit throws an unhandled exception our top priority is to
// unregister and dispose the circuit. This will prevent any new dispatches from the client
// from making it into application code.
//
// As part of this process, we also notify the client (if there is one) of the error, and we
// *expect* a well-behaved client to disconnect. A malicious client can't be expected to disconnect,
// but since we've unregistered the circuit they won't be able to access it anyway. When a call
// comes into any hub method and the circuit has been disassociated, we will abort the connection.
// It's safe to assume that's the result of a race condition or misbehaving client.
//
// Now it's important to remember that we can only abort a connection as part of a hub method call.
// We can dispose a circuit in the background, but we have to deal with a possible race condition
// any time we try to acquire access to the circuit - because it could have gone away in the
// background - outside of the scope of a hub method.
//
// In general we author our Hub methods as async methods, but we fire-and-forget anything that
// needs access to the circuit/application state to unblock the message loop. Using async in our
// Hub methods allows us to ensure message delivery to the client before we abort the connection
// in error cases.
internal sealed partial class ComponentHub : Hub
{
private static readonly object CircuitKey = new();
private readonly IServerComponentDeserializer _serverComponentSerializer;
private readonly IDataProtectionProvider _dataProtectionProvider;
private readonly ICircuitFactory _circuitFactory;
private readonly CircuitIdFactory _circuitIdFactory;
private readonly CircuitRegistry _circuitRegistry;
private readonly ICircuitHandleRegistry _circuitHandleRegistry;
private readonly ILogger _logger;
private readonly ActivityContext _httpContext;
public ComponentHub(
IServerComponentDeserializer serializer,
IDataProtectionProvider dataProtectionProvider,
ICircuitFactory circuitFactory,
CircuitIdFactory circuitIdFactory,
CircuitRegistry circuitRegistry,
ICircuitHandleRegistry circuitHandleRegistry,
ILogger<ComponentHub> logger)
{
_serverComponentSerializer = serializer;
_dataProtectionProvider = dataProtectionProvider;
_circuitFactory = circuitFactory;
_circuitIdFactory = circuitIdFactory;
_circuitRegistry = circuitRegistry;
_circuitHandleRegistry = circuitHandleRegistry;
_logger = logger;
_httpContext = ComponentsActivitySource.CaptureHttpContext();
}
/// <summary>
/// Gets the default endpoint path for incoming connections.
/// </summary>
public static PathString DefaultPath { get; } = "/_blazor";
public override Task OnDisconnectedAsync(Exception exception)
{
// If the CircuitHost is gone now this isn't an error. This could happen if the disconnect
// if the result of well behaving client hanging up after an unhandled exception.
var circuitHost = _circuitHandleRegistry.GetCircuit(Context.Items, CircuitKey);
if (circuitHost == null)
{
return Task.CompletedTask;
}
return _circuitRegistry.DisconnectAsync(circuitHost, Context.ConnectionId);
}
public async ValueTask<string> StartCircuit(string baseUri, string uri, string serializedComponentRecords, string applicationState)
{
var circuitHost = _circuitHandleRegistry.GetCircuit(Context.Items, CircuitKey);
if (circuitHost != null)
{
// This is an error condition and an attempt to bind multiple circuits to a single connection.
// We can reject this and terminate the connection.
Log.CircuitAlreadyInitialized(_logger, circuitHost.CircuitId);
await NotifyClientError(Clients.Caller, $"The circuit host '{circuitHost.CircuitId}' has already been initialized.");
Context.Abort();
return null;
}
if (baseUri == null ||
uri == null ||
!Uri.TryCreate(baseUri, UriKind.Absolute, out _) ||
!Uri.TryCreate(uri, UriKind.Absolute, out _))
{
// We do some really minimal validation here to prevent obviously wrong data from getting in
// without duplicating too much logic.
//
// This is an error condition attempting to initialize the circuit in a way that would fail.
// We can reject this and terminate the connection.
Log.InvalidInputData(_logger);
await NotifyClientError(Clients.Caller, "The uris provided are invalid.");
Context.Abort();
return null;
}
if (!_serverComponentSerializer.TryDeserializeComponentDescriptorCollection(serializedComponentRecords, out var components))
{
Log.InvalidInputData(_logger);
await NotifyClientError(Clients.Caller, "The list of component records is not valid.");
Context.Abort();
return null;
}
try
{
var circuitClient = new CircuitClientProxy(Clients.Caller, Context.ConnectionId);
var store = !string.IsNullOrEmpty(applicationState) ?
new ProtectedPrerenderComponentApplicationStore(applicationState, _dataProtectionProvider) :
new ProtectedPrerenderComponentApplicationStore(_dataProtectionProvider);
var resourceCollection = Context.GetHttpContext().GetEndpoint()?.Metadata.GetMetadata<ResourceAssetCollection>();
circuitHost = await _circuitFactory.CreateCircuitHostAsync(
components,
circuitClient,
baseUri,
uri,
Context.User,
store,
resourceCollection);
// Fire-and-forget the initialization process, because we can't block the
// SignalR message loop (we'd get a deadlock if any of the initialization
// logic relied on receiving a subsequent message from SignalR), and it will
// take care of its own errors anyway.
_ = circuitHost.InitializeAsync(store, _httpContext, Context.ConnectionAborted);
// It's safe to *publish* the circuit now because nothing will be able
// to run inside it until after InitializeAsync completes.
_circuitRegistry.Register(circuitHost);
_circuitHandleRegistry.SetCircuit(Context.Items, CircuitKey, circuitHost);
// Returning the secret here so the client can reconnect.
//
// Logging the secret and circuit ID here so we can associate them with just logs (if TRACE level is on).
Log.CreatedCircuit(_logger, circuitHost.CircuitId, circuitHost.CircuitId.Secret, Context.ConnectionId);
return circuitHost.CircuitId.Secret;
}
catch (Exception ex)
{
// If the circuit fails to initialize synchronously we can notify the client immediately
// and shut down the connection.
Log.CircuitInitializationFailed(_logger, ex);
await NotifyClientError(Clients.Caller, "The circuit failed to initialize.");
Context.Abort();
return null;
}
}
public async Task UpdateRootComponents(string serializedComponentOperations, string applicationState)
{
var circuitHost = await GetActiveCircuitAsync();
if (circuitHost == null)
{
return;
}
if (!_serverComponentSerializer.TryDeserializeRootComponentOperations(
serializedComponentOperations,
out var operations))
{
// There was an error, so kill the circuit.
await _circuitRegistry.TerminateAsync(circuitHost.CircuitId);
await NotifyClientError(Clients.Caller, "The list of component operations is not valid.");
Context.Abort();
return;
}
var store = !string.IsNullOrEmpty(applicationState) ?
new ProtectedPrerenderComponentApplicationStore(applicationState, _dataProtectionProvider) :
new ProtectedPrerenderComponentApplicationStore(_dataProtectionProvider);
_ = circuitHost.UpdateRootComponents(operations, store, Context.ConnectionAborted);
}
public async ValueTask<bool> ConnectCircuit(string circuitIdSecret)
{
// TryParseCircuitId will not throw.
if (!_circuitIdFactory.TryParseCircuitId(circuitIdSecret, out var circuitId))
{
// Invalid id.
Log.InvalidCircuitId(_logger, circuitIdSecret);
return false;
}
// ConnectAsync will not throw.
var circuitHost = await _circuitRegistry.ConnectAsync(
circuitId,
Clients.Caller,
Context.ConnectionId,
Context.ConnectionAborted);
if (circuitHost != null)
{
_circuitHandleRegistry.SetCircuit(Context.Items, CircuitKey, circuitHost);
circuitHost.SetCircuitUser(Context.User);
circuitHost.SendPendingBatches();
return true;
}
// If we get here the circuit does not exist anymore. This is something that's valid for a client to
// recover from, and the client is not holding any resources right now other than the connection.
return false;
}
public async ValueTask BeginInvokeDotNetFromJS(string callId, string assemblyName, string methodIdentifier, long dotNetObjectId, string argsJson)
{
var circuitHost = await GetActiveCircuitAsync();
if (circuitHost == null)
{
return;
}
_ = circuitHost.BeginInvokeDotNetFromJS(callId, assemblyName, methodIdentifier, dotNetObjectId, argsJson);
}
public async ValueTask EndInvokeJSFromDotNet(long asyncHandle, bool succeeded, string arguments)
{
var circuitHost = await GetActiveCircuitAsync();
if (circuitHost == null)
{
return;
}
_ = circuitHost.EndInvokeJSFromDotNet(asyncHandle, succeeded, arguments);
}
public async ValueTask ReceiveByteArray(int id, byte[] data)
{
var circuitHost = await GetActiveCircuitAsync();
if (circuitHost == null)
{
return;
}
_ = circuitHost.ReceiveByteArray(id, data);
}
public async ValueTask<bool> ReceiveJSDataChunk(long streamId, long chunkId, byte[] chunk, string error)
{
var circuitHost = await GetActiveCircuitAsync();
if (circuitHost == null)
{
return false;
}
// Note: this await will block the circuit. This is intentional.
// The call into the circuitHost.ReceiveJSDataChunk will block regardless as we call into Renderer.Dispatcher.InvokeAsync
// which ensures we're running on the main circuit thread so that the server/client remain in the same
// synchronization context. Additionally, we're utilizing the return value as a heartbeat for the transfer
// process, and without it would likely need to setup a separate endpoint to handle that functionality.
return await circuitHost.ReceiveJSDataChunk(streamId, chunkId, chunk, error);
}
public async IAsyncEnumerable<ArraySegment<byte>> SendDotNetStreamToJS(long streamId)
{
var circuitHost = await GetActiveCircuitAsync();
if (circuitHost == null)
{
yield break;
}
var dotNetStreamReference = await circuitHost.TryClaimPendingStream(streamId);
if (dotNetStreamReference == default)
{
yield break;
}
var buffer = ArrayPool<byte>.Shared.Rent(32 * 1024);
try
{
int bytesRead;
while ((bytesRead = await circuitHost.SendDotNetStreamAsync(dotNetStreamReference, streamId, buffer)) > 0)
{
yield return new ArraySegment<byte>(buffer, 0, bytesRead);
}
}
finally
{
ArrayPool<byte>.Shared.Return(buffer, clearArray: true);
if (!dotNetStreamReference.LeaveOpen)
{
dotNetStreamReference.Stream?.Dispose();
}
}
}
public async ValueTask OnRenderCompleted(long renderId, string errorMessageOrNull)
{
var circuitHost = await GetActiveCircuitAsync();
if (circuitHost == null)
{
return;
}
Log.ReceivedConfirmationForBatch(_logger, renderId);
_ = circuitHost.OnRenderCompletedAsync(renderId, errorMessageOrNull);
}
public async ValueTask OnLocationChanged(string uri, string? state, bool intercepted)
{
var circuitHost = await GetActiveCircuitAsync();
if (circuitHost == null)
{
return;
}
_ = circuitHost.OnLocationChangedAsync(uri, state, intercepted);
}
public async ValueTask OnLocationChanging(int callId, string uri, string? state, bool intercepted)
{
var circuitHost = await GetActiveCircuitAsync();
if (circuitHost == null)
{
return;
}
_ = circuitHost.OnLocationChangingAsync(callId, uri, state, intercepted);
}
// We store the CircuitHost through a *handle* here because Context.Items is tied to the lifetime
// of the connection. It's possible that a misbehaving client could cause disposal of a CircuitHost
// but keep a connection open indefinitely, preventing GC of the Circuit and related application state.
// Using a handle allows the CircuitHost to clear this reference in the background.
//
// See comment on error handling on the class definition.
private async ValueTask<CircuitHost> GetActiveCircuitAsync([CallerMemberName] string callSite = "")
{
var handle = _circuitHandleRegistry.GetCircuitHandle(Context.Items, CircuitKey);
var circuitHost = handle?.CircuitHost;
if (handle != null && circuitHost == null)
{
// This can occur when a circuit host does not exist anymore due to an unhandled exception.
// We can reject this and terminate the connection.
Log.CircuitHostShutdown(_logger, callSite);
await NotifyClientError(Clients.Caller, "Circuit has been shut down due to error.");
Context.Abort();
return null;
}
else if (circuitHost == null)
{
// This can occur when a circuit host does not exist anymore due to an unhandled exception.
// We can reject this and terminate the connection.
Log.CircuitHostNotInitialized(_logger, callSite);
await NotifyClientError(Clients.Caller, "Circuit not initialized.");
Context.Abort();
return null;
}
return circuitHost;
}
private static Task NotifyClientError(IClientProxy client, string error) => client.SendAsync("JS.Error", error);
private static partial class Log
{
[LoggerMessage(1, LogLevel.Debug, "Received confirmation for batch {BatchId}", EventName = "ReceivedConfirmationForBatch")]
public static partial void ReceivedConfirmationForBatch(ILogger logger, long batchId);
[LoggerMessage(2, LogLevel.Debug, "The circuit host '{CircuitId}' has already been initialized", EventName = "CircuitAlreadyInitialized")]
public static partial void CircuitAlreadyInitialized(ILogger logger, CircuitId circuitId);
[LoggerMessage(3, LogLevel.Debug, "Call to '{CallSite}' received before the circuit host initialization", EventName = "CircuitHostNotInitialized")]
public static partial void CircuitHostNotInitialized(ILogger logger, [CallerMemberName] string callSite = "");
[LoggerMessage(4, LogLevel.Debug, "Call to '{CallSite}' received after the circuit was shut down", EventName = "CircuitHostShutdown")]
public static partial void CircuitHostShutdown(ILogger logger, [CallerMemberName] string callSite = "");
[LoggerMessage(5, LogLevel.Debug, "Call to '{CallSite}' received invalid input data", EventName = "InvalidInputData")]
public static partial void InvalidInputData(ILogger logger, [CallerMemberName] string callSite = "");
[LoggerMessage(6, LogLevel.Debug, "Circuit initialization failed", EventName = "CircuitInitializationFailed")]
public static partial void CircuitInitializationFailed(ILogger logger, Exception exception);
[LoggerMessage(7, LogLevel.Debug, "Created circuit '{CircuitId}' with secret '{CircuitIdSecret}' for '{ConnectionId}'", EventName = "CreatedCircuit")]
private static partial void CreatedCircuitCore(ILogger logger, CircuitId circuitId, string circuitIdSecret, string connectionId);
public static void CreatedCircuit(ILogger logger, CircuitId circuitId, string circuitSecret, string connectionId)
{
// Redact the secret unless tracing is on.
if (!logger.IsEnabled(LogLevel.Trace))
{
circuitSecret = "(redacted)";
}
CreatedCircuitCore(logger, circuitId, circuitSecret, connectionId);
}
[LoggerMessage(8, LogLevel.Debug, "ConnectAsync received an invalid circuit id '{CircuitIdSecret}'", EventName = "InvalidCircuitId")]
private static partial void InvalidCircuitIdCore(ILogger logger, string circuitIdSecret);
public static void InvalidCircuitId(ILogger logger, string circuitSecret)
{
// Redact the secret unless tracing is on.
if (!logger.IsEnabled(LogLevel.Trace))
{
circuitSecret = "(redacted)";
}
InvalidCircuitIdCore(logger, circuitSecret);
}
}
}
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