Fix CsrfProtectionMiddleware perf degradations - #67488
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DeagleGross merged 6 commits intoJul 2, 2026
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PR dotnet#67119 introduced an unconditional context.Items[MiddlewareInvokedKeys.CsrfProtection] = ... write in CsrfProtectionMiddleware.InvokeAsync, which forces the lazy HttpContext.Items dictionary to allocate on every request. This blew up allocations on hot non-antiforgery paths (~264 B/request extra; ~1.3 GB/s at TechEmpower plaintext throughput). See PR dotnet#67119 comment 4835979504. Gate the marker write on either endpoint == null (re-execute into an antiforgery-required page must still find the marker) or the matched endpoint carrying any IAntiforgeryMetadata (both DisableAntiforgery() for re-execute and the FormFeature backstop for RequiresValidation:true). For endpoints with no antiforgery metadata at all - the hot non-antiforgery path - the marker has no consumer and is now skipped. Adds CsrfProtection_HotPath_NoEndpointMetadata_DoesNotAllocateItemsDictionary as a regression guard using GC.GetAllocatedBytesForCurrentThread(). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
Optimizes the auto-injected CsrfProtectionMiddleware hot path by avoiding unnecessary HttpContext.Items initialization when an endpoint has no antiforgery metadata, while preserving the marker behavior needed for reroute/re-execute scenarios and antiforgery/disable-antiforgery endpoints.
Changes:
- Conditionally stamps the
MiddlewareInvokedKeys.CsrfProtectionmarker only whenendpointisnullor whenIAntiforgeryMetadatais present. - Updates integration tests to assert the marker is not set for endpoints without antiforgery metadata.
Show a summary per file
| File | Description |
|---|---|
| src/DefaultBuilder/src/Internal/CsrfProtectionMiddleware.cs | Avoids HttpContext.Items allocation by not stamping the marker on the no-antiforgery-metadata path. |
| src/DefaultBuilder/test/Microsoft.AspNetCore.Tests/CsrfProtectionIntegrationTests.cs | Adjusts assertions to reflect that the marker is not set when the endpoint has no antiforgery metadata. |
Copilot's findings
- Files reviewed: 2/2 changed files
- Comments generated: 1
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
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Fixes degradation noticed by @BrennanConroy (thanks!) #67119 (comment)
There are several problems:
CsrfProtectionMiddlewarewas unconditionally writingMiddlewareInvokedKeys.CsrfProtectiontocontext.Items. The hot-path where writing tocontext.Itemsis useless is when endpoint is not null, but there is no antiforgeryMetadata. In such case CSRF just skips since endpoint is intentionally not wired with Antiforgery validation mechanisms.CsrfProtectionMiddlewareis useless without Routing (because there is nocontext.GetEndpoint()and obviosly antiforgery metadata. However, we were always registeringCsrfProtectionMiddlewarein the pipeline, when Routing was injected only if_builtApplication.DataSources.Count > 0is true. So I applied same check there.Testing
For current
maincode:and for updated code: