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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.
#nullable enable
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Primitives;
using Microsoft.Net.Http.Headers;
// Keep the type public for Security repo as it would be a breaking change to change the accessor now.
// Make this type internal for other repos as it could be used by multiple projects and having it public causes type conflicts.
#if SECURITY
namespace Microsoft.AspNetCore.Authentication.Cookies
{
/// <summary>
/// This handles cookies that are limited by per cookie length. It breaks down long cookies for responses, and reassembles them
/// from requests.
/// </summary>
public class ChunkingCookieManager : ICookieManager
{
#else
namespace Microsoft.AspNetCore.Internal
{
/// <summary>
/// This handles cookies that are limited by per cookie length. It breaks down long cookies for responses, and reassembles them
/// from requests.
/// </summary>
internal class ChunkingCookieManager
{
#endif
/// <summary>
/// The default maximum size of characters in a cookie to send back to the client.
/// </summary>
public const int DefaultChunkSize = 4050;
private const string ChunkKeySuffix = "C";
private const string ChunkCountPrefix = "chunks-";
/// <summary>
/// Initializes a new instance of <see cref="ChunkingCookieManager"/>.
/// </summary>
public ChunkingCookieManager()
{
// Lowest common denominator. Safari has the lowest known limit (4093), and we leave little extra just in case.
// See http://browsercookielimits.x64.me/.
// Leave at least 40 in case CookiePolicy tries to add 'secure', 'samesite=strict' and/or 'httponly'.
ChunkSize = DefaultChunkSize;
}
/// <summary>
/// The maximum size of cookie to send back to the client. If a cookie exceeds this size it will be broken down into multiple
/// cookies. Set this value to null to disable this behavior. The default is 4090 characters, which is supported by all
/// common browsers.
///
/// Note that browsers may also have limits on the total size of all cookies per domain, and on the number of cookies per domain.
/// </summary>
public int? ChunkSize { get; set; }
/// <summary>
/// Throw if not all chunks of a cookie are available on a request for re-assembly.
/// </summary>
public bool ThrowForPartialCookies { get; set; }
// Parse the "chunks-XX" to determine how many chunks there should be.
private static int ParseChunksCount(string? value)
{
if (value != null && value.StartsWith(ChunkCountPrefix, StringComparison.Ordinal))
{
var chunksCountString = value.Substring(ChunkCountPrefix.Length);
int chunksCount;
if (int.TryParse(chunksCountString, NumberStyles.None, CultureInfo.InvariantCulture, out chunksCount))
{
return chunksCount;
}
}
return 0;
}
/// <summary>
/// Get the reassembled cookie. Non chunked cookies are returned normally.
/// Cookies with missing chunks just have their "chunks-XX" header returned.
/// </summary>
/// <param name="context"></param>
/// <param name="key"></param>
/// <returns>The reassembled cookie, if any, or null.</returns>
public string? GetRequestCookie(HttpContext context, string key)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
var requestCookies = context.Request.Cookies;
var value = requestCookies[key];
var chunksCount = ParseChunksCount(value);
if (chunksCount > 0)
{
var chunks = new List<string>(10); // chunksCount may be wrong, don't trust it.
for (var chunkId = 1; chunkId <= chunksCount; chunkId++)
{
var chunk = requestCookies[key + ChunkKeySuffix + chunkId.ToString(CultureInfo.InvariantCulture)];
if (string.IsNullOrEmpty(chunk))
{
if (ThrowForPartialCookies)
{
var totalSize = 0;
for (int i = 0; i < chunkId - 1; i++)
{
totalSize += chunks[i].Length;
}
throw new FormatException(
string.Format(
CultureInfo.CurrentCulture,
"The chunked cookie is incomplete. Only {0} of the expected {1} chunks were found, totaling {2} characters. A client size limit may have been exceeded.",
chunkId - 1,
chunksCount,
totalSize));
}
// Missing chunk, abort by returning the original cookie value. It may have been a false positive?
return value;
}
chunks.Add(chunk);
}
return string.Join(string.Empty, chunks);
}
return value;
}
/// <summary>
/// Appends a new response cookie to the Set-Cookie header. If the cookie is larger than the given size limit
/// then it will be broken down into multiple cookies as follows:
/// Set-Cookie: CookieName=chunks-3; path=/
/// Set-Cookie: CookieNameC1=Segment1; path=/
/// Set-Cookie: CookieNameC2=Segment2; path=/
/// Set-Cookie: CookieNameC3=Segment3; path=/
/// </summary>
/// <param name="context"></param>
/// <param name="key"></param>
/// <param name="value"></param>
/// <param name="options"></param>
public void AppendResponseCookie(HttpContext context, string key, string? value, CookieOptions options)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
if (options == null)
{
throw new ArgumentNullException(nameof(options));
}
var template = new SetCookieHeaderValue(key)
{
Domain = options.Domain,
Expires = options.Expires,
SameSite = (Net.Http.Headers.SameSiteMode)options.SameSite,
HttpOnly = options.HttpOnly,
Path = options.Path,
Secure = options.Secure,
MaxAge = options.MaxAge,
};
var templateLength = template.ToString().Length;
value = value ?? string.Empty;
// Normal cookie
var responseCookies = context.Response.Cookies;
if (!ChunkSize.HasValue || ChunkSize.Value > templateLength + value.Length)
{
responseCookies.Append(key, value, options);
}
else if (ChunkSize.Value < templateLength + 10)
{
// 10 is the minimum data we want to put in an individual cookie, including the cookie chunk identifier "CXX".
// No room for data, we can't chunk the options and name
throw new InvalidOperationException("The cookie key and options are larger than ChunksSize, leaving no room for data.");
}
else
{
// Break the cookie down into multiple cookies.
// Key = CookieName, value = "Segment1Segment2Segment2"
// Set-Cookie: CookieName=chunks-3; path=/
// Set-Cookie: CookieNameC1="Segment1"; path=/
// Set-Cookie: CookieNameC2="Segment2"; path=/
// Set-Cookie: CookieNameC3="Segment3"; path=/
var dataSizePerCookie = ChunkSize.Value - templateLength - 3; // Budget 3 chars for the chunkid.
var cookieChunkCount = (int)Math.Ceiling(value.Length * 1.0 / dataSizePerCookie);
responseCookies.Append(key, ChunkCountPrefix + cookieChunkCount.ToString(CultureInfo.InvariantCulture), options);
var offset = 0;
for (var chunkId = 1; chunkId <= cookieChunkCount; chunkId++)
{
var remainingLength = value.Length - offset;
var length = Math.Min(dataSizePerCookie, remainingLength);
var segment = value.Substring(offset, length);
offset += length;
responseCookies.Append(key + ChunkKeySuffix + chunkId.ToString(CultureInfo.InvariantCulture), segment, options);
}
}
}
/// <summary>
/// Deletes the cookie with the given key by setting an expired state. If a matching chunked cookie exists on
/// the request, delete each chunk.
/// </summary>
/// <param name="context"></param>
/// <param name="key"></param>
/// <param name="options"></param>
public void DeleteCookie(HttpContext context, string key, CookieOptions options)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
if (options == null)
{
throw new ArgumentNullException(nameof(options));
}
var keys = new List<string>();
keys.Add(key + "=");
var requestCookies = context.Request.Cookies;
var requestCookie = requestCookies[key];
long chunks = ParseChunksCount(requestCookie);
if (chunks > 0)
{
for (int i = 1; i <= chunks + 1; i++)
{
var subkey = key + ChunkKeySuffix + i.ToString(CultureInfo.InvariantCulture);
// Only delete cookies we received. We received the chunk count cookie so we should have received the others too.
if (string.IsNullOrEmpty(requestCookies[subkey]))
{
chunks = i - 1;
break;
}
keys.Add(subkey + "=");
}
}
var domainHasValue = !string.IsNullOrEmpty(options.Domain);
var pathHasValue = !string.IsNullOrEmpty(options.Path);
Func<string, bool> rejectPredicate;
Func<string, bool> predicate = value => keys.Any(k => value.StartsWith(k, StringComparison.OrdinalIgnoreCase));
if (domainHasValue)
{
rejectPredicate = value => predicate(value) && value.IndexOf("domain=" + options.Domain, StringComparison.OrdinalIgnoreCase) != -1;
}
else if (pathHasValue)
{
rejectPredicate = value => predicate(value) && value.IndexOf("path=" + options.Path, StringComparison.OrdinalIgnoreCase) != -1;
}
else
{
rejectPredicate = value => predicate(value);
}
var responseHeaders = context.Response.Headers;
var existingValues = responseHeaders[HeaderNames.SetCookie];
if (!StringValues.IsNullOrEmpty(existingValues))
{
responseHeaders[HeaderNames.SetCookie] = existingValues.Where(value => !rejectPredicate(value)).ToArray();
}
AppendResponseCookie(
context,
key,
string.Empty,
new CookieOptions()
{
Path = options.Path,
Domain = options.Domain,
SameSite = options.SameSite,
Secure = options.Secure,
IsEssential = options.IsEssential,
Expires = DateTimeOffset.UnixEpoch,
HttpOnly = options.HttpOnly,
});
for (int i = 1; i <= chunks; i++)
{
AppendResponseCookie(
context,
key + "C" + i.ToString(CultureInfo.InvariantCulture),
string.Empty,
new CookieOptions()
{
Path = options.Path,
Domain = options.Domain,
SameSite = options.SameSite,
Secure = options.Secure,
IsEssential = options.IsEssential,
Expires = DateTimeOffset.UnixEpoch,
HttpOnly = options.HttpOnly,
});
}
}
}
}
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