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ForwardedHeadersMiddleware.cs
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/
ForwardedHeadersMiddleware.cs
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// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpOverrides.Internal;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using Microsoft.Extensions.Primitives;
namespace Microsoft.AspNetCore.HttpOverrides
{
public class ForwardedHeadersMiddleware
{
private const string XForwardedForHeaderName = "X-Forwarded-For";
private const string XForwardedHostHeaderName = "X-Forwarded-Host";
private const string XForwardedProtoHeaderName = "X-Forwarded-Proto";
private const string XOriginalForName = "X-Original-For";
private const string XOriginalHostName = "X-Original-Host";
private const string XOriginalProtoName = "X-Original-Proto";
private readonly ForwardedHeadersOptions _options;
private readonly RequestDelegate _next;
private readonly ILogger _logger;
public ForwardedHeadersMiddleware(RequestDelegate next, ILoggerFactory loggerFactory, IOptions<ForwardedHeadersOptions> options)
{
if (next == null)
{
throw new ArgumentNullException(nameof(next));
}
if (loggerFactory == null)
{
throw new ArgumentNullException(nameof(loggerFactory));
}
if (options == null)
{
throw new ArgumentNullException(nameof(options));
}
_options = options.Value;
_logger = loggerFactory.CreateLogger<ForwardedHeadersMiddleware>();
_next = next;
}
public Task Invoke(HttpContext context)
{
ApplyForwarders(context);
return _next(context);
}
public void ApplyForwarders(HttpContext context)
{
// Gather expected headers. Enabled headers must have the same number of entries.
string[] forwardedFor = null, forwardedProto = null, forwardedHost = null;
bool checkFor = false, checkProto = false, checkHost = false;
int entryCount = 0;
if ((_options.ForwardedHeaders & ForwardedHeaders.XForwardedFor) == ForwardedHeaders.XForwardedFor)
{
checkFor = true;
forwardedFor = context.Request.Headers.GetCommaSeparatedValues(XForwardedForHeaderName);
entryCount = Math.Max(forwardedFor.Length, entryCount);
}
if ((_options.ForwardedHeaders & ForwardedHeaders.XForwardedProto) == ForwardedHeaders.XForwardedProto)
{
checkProto = true;
forwardedProto = context.Request.Headers.GetCommaSeparatedValues(XForwardedProtoHeaderName);
if (_options.RequireHeaderSymmetry && checkFor && forwardedFor.Length != forwardedProto.Length)
{
_logger.LogDebug(1, "Parameter count mismatch between X-Forwarded-For and X-Forwarded-Proto.");
return;
}
entryCount = Math.Max(forwardedProto.Length, entryCount);
}
if ((_options.ForwardedHeaders & ForwardedHeaders.XForwardedHost) == ForwardedHeaders.XForwardedHost)
{
checkHost = true;
forwardedHost = context.Request.Headers.GetCommaSeparatedValues(XForwardedHostHeaderName);
if (_options.RequireHeaderSymmetry
&& ((checkFor && forwardedFor.Length != forwardedHost.Length)
|| (checkProto && forwardedProto.Length != forwardedHost.Length)))
{
_logger.LogDebug(1, "Parameter count mismatch between X-Forwarded-Host and X-Forwarded-For or X-Forwarded-Proto.");
return;
}
entryCount = Math.Max(forwardedHost.Length, entryCount);
}
// Apply ForwardLimit, if any
if (_options.ForwardLimit.HasValue && entryCount > _options.ForwardLimit)
{
entryCount = _options.ForwardLimit.Value;
}
// Group the data together.
var sets = new SetOfForwarders[entryCount];
for (int i = 0; i < sets.Length; i++)
{
// They get processed in reverse order, right to left.
var set = new SetOfForwarders();
if (checkFor && i < forwardedFor.Length)
{
set.IpAndPortText = forwardedFor[forwardedFor.Length - i - 1];
}
if (checkProto && i < forwardedProto.Length)
{
set.Scheme = forwardedProto[forwardedProto.Length - i - 1];
}
if (checkHost && i < forwardedHost.Length)
{
set.Host = forwardedHost[forwardedHost.Length - i - 1];
}
sets[i] = set;
}
// Gather initial values
var connection = context.Connection;
var request = context.Request;
var currentValues = new SetOfForwarders()
{
RemoteIpAndPort = connection.RemoteIpAddress != null ? new IPEndPoint(connection.RemoteIpAddress, connection.RemotePort) : null,
// Host and Scheme initial values are never inspected, no need to set them here.
};
var checkKnownIps = _options.KnownNetworks.Count > 0 || _options.KnownProxies.Count > 0;
bool applyChanges = false;
int entriesConsumed = 0;
for ( ; entriesConsumed < sets.Length; entriesConsumed++)
{
var set = sets[entriesConsumed];
if (checkFor)
{
// For the first instance, allow remoteIp to be null for servers that don't support it natively.
if (currentValues.RemoteIpAndPort != null && checkKnownIps && !CheckKnownAddress(currentValues.RemoteIpAndPort.Address))
{
// Stop at the first unknown remote IP, but still apply changes processed so far.
_logger.LogDebug(1, $"Unknown proxy: {currentValues.RemoteIpAndPort}");
break;
}
IPEndPoint parsedEndPoint;
if (IPEndPointParser.TryParse(set.IpAndPortText, out parsedEndPoint))
{
applyChanges = true;
set.RemoteIpAndPort = parsedEndPoint;
currentValues.IpAndPortText = set.IpAndPortText;
currentValues.RemoteIpAndPort = set.RemoteIpAndPort;
}
else if (_options.RequireHeaderSymmetry)
{
_logger.LogDebug(2, $"Failed to parse forwarded IPAddress: {currentValues.IpAndPortText}");
return;
}
}
if (checkProto)
{
if (!string.IsNullOrEmpty(set.Scheme))
{
applyChanges = true;
currentValues.Scheme = set.Scheme;
}
else if (_options.RequireHeaderSymmetry)
{
_logger.LogDebug(3, $"Failed to parse forwarded scheme: {set.Scheme}");
return;
}
}
if (checkHost)
{
if (!string.IsNullOrEmpty(set.Host))
{
applyChanges = true;
currentValues.Host = set.Host;
}
else if (_options.RequireHeaderSymmetry)
{
_logger.LogDebug(4, $"Failed to parse forwarded host: {set.Host}");
return;
}
}
}
if (applyChanges)
{
if (checkFor && currentValues.RemoteIpAndPort != null)
{
if (connection.RemoteIpAddress != null)
{
// Save the original
request.Headers[XOriginalForName] = new IPEndPoint(connection.RemoteIpAddress, connection.RemotePort).ToString();
}
if (forwardedFor.Length > entriesConsumed)
{
// Truncate the consumed header values
request.Headers[XForwardedForHeaderName] = forwardedFor.Take(forwardedFor.Length - entriesConsumed).ToArray();
}
else
{
// All values were consumed
request.Headers.Remove(XForwardedForHeaderName);
}
connection.RemoteIpAddress = currentValues.RemoteIpAndPort.Address;
connection.RemotePort = currentValues.RemoteIpAndPort.Port;
}
if (checkProto && currentValues.Scheme != null)
{
// Save the original
request.Headers[XOriginalProtoName] = request.Scheme;
if (forwardedProto.Length > entriesConsumed)
{
// Truncate the consumed header values
request.Headers[XForwardedProtoHeaderName] = forwardedProto.Take(forwardedProto.Length - entriesConsumed).ToArray();
}
else
{
// All values were consumed
request.Headers.Remove(XForwardedProtoHeaderName);
}
request.Scheme = currentValues.Scheme;
}
if (checkHost && currentValues.Host != null)
{
// Save the original
request.Headers[XOriginalHostName] = request.Host.ToString();
if (forwardedHost.Length > entriesConsumed)
{
// Truncate the consumed header values
request.Headers[XForwardedHostHeaderName] = forwardedHost.Take(forwardedHost.Length - entriesConsumed).ToArray();
}
else
{
// All values were consumed
request.Headers.Remove(XForwardedHostHeaderName);
}
request.Host = HostString.FromUriComponent(currentValues.Host);
}
}
}
private bool CheckKnownAddress(IPAddress address)
{
if (_options.KnownProxies.Contains(address))
{
return true;
}
foreach (var network in _options.KnownNetworks)
{
if (network.Contains(address))
{
return true;
}
}
return false;
}
private struct SetOfForwarders
{
public string IpAndPortText;
public IPEndPoint RemoteIpAndPort;
public string Host;
public string Scheme;
}
}
}