Apply consistent redirect-URI validation on AccountController.SignIn#3940
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SignIn was missing the IsPercentEncodedSlashBypass guard that Challenge already had. A redirectUri like /%2fevil.example passes Url.IsLocalUrl (the framework only checks for literal // and /\), but a normalising reverse proxy decodes it to //evil.example; browsers then follow it as a protocol-relative URL after sign-in. Add !IsPercentEncodedSlashBypass(redirectUri) to the SignIn guard, matching the guard on Challenge. Also update the IsPercentEncodedSlashBypass XML doc to note it is a local copy of RedirectUriHelper.HasPercentEncodedSlashPrefix (internal in a separate assembly) so future changes keep both in sync. Tests: two new facts in AccountControllerTests covering the %2f and %5c variants on the SignIn path, using the realistic IsLocalUrl mock so removing either guard breaks the tests. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 00c4f24d-188f-4bd9-926c-a6d0620eb053
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Pinned [Microsoft.Identity.Web](https://github.com/AzureAD/microsoft-identity-web) at 4.13.2. <details> <summary>Release notes</summary> _Sourced from [Microsoft.Identity.Web's releases](https://github.com/AzureAD/microsoft-identity-web/releases)._ ## 4.13.2 ## What's Changed * Apply reserved-header handling on the request-clone path and cover all X-MS-TOKEN- headers by @iNinja in AzureAD/microsoft-identity-web#3915 * Restore independent PR pipeline + pool-aware MI identity + net462/472 unit tests by @iarekk in AzureAD/microsoft-identity-web#3935 * Post-release 4.13.0: changelog and public API shipped move by @neha-bhargava in AzureAD/microsoft-identity-web#3937 * Remove redundant 'Run unit tests' GitHub Action by @iarekk in AzureAD/microsoft-identity-web#3939 * Apply consistent redirect-URI validation on AccountController.SignIn by @iNinja in AzureAD/microsoft-identity-web#3940 * Fix duplicate logging of MsalUiRequiredException (in-repo copy of #3910) by @iarekk in AzureAD/microsoft-identity-web#3941 * Use MSAL's recent UserFIC API for agentic flows by @Avery-Dunn in AzureAD/microsoft-identity-web#3842 * Restore CustomizeHttpRequestMessage to run after the authorization header by @neha-bhargava in AzureAD/microsoft-identity-web#3943 * Bump Microsoft.IdentityModel.Tokens.Saml from 5.7.0 to 8.19.1 by @dependabot[bot] in AzureAD/microsoft-identity-web#3909 * Revert #3909: keep OWIN Saml/WsFederation on 5.7.0 by @iarekk in AzureAD/microsoft-identity-web#3944 * Bump Microsoft.Identity.Abstractions from 12.4.0 to 12.5.0 by @neha-bhargava in AzureAD/microsoft-identity-web#3947 * Add OnBeforeAuthHeaderCreation / OnAfterAuthHeaderCreation hooks to DownstreamApi by @neha-bhargava in AzureAD/microsoft-identity-web#3942 * Update IdentityModelV5Version and SamlPackageVersion to 5.7.1 in proj… by @trwalke in AzureAD/microsoft-identity-web#3950 * Rename retired MSALMSIV2 agent pool to MISEManagedIdentity by @gladjohn with @Copilot in AzureAD/microsoft-identity-web#3949 * Improve IDW10109 error handling for credential loading failures by @Avery-Dunn in AzureAD/microsoft-identity-web#3946 * Bump MSAL dependencies to 4.86.1 in central props by @gladjohn with @Copilot in AzureAD/microsoft-identity-web#3953 * Bump the notsecurity group with 3 updates by @dependabot[bot] in AzureAD/microsoft-identity-web#3954 **Full Changelog**: AzureAD/microsoft-identity-web@4.13.0...4.13.2 Commits viewable in [compare view](AzureAD/microsoft-identity-web@4.13.0...4.13.2). </details> Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
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AccountController.SignIn validated the
redirectUriquery parameter withUrl.IsLocalUrl(redirectUri)only. The siblingChallengeaction already had an additional guard --!IsPercentEncodedSlashBypass(redirectUri)-- that was added in a previous PR but was not applied toSignIn.A
redirectUrivalue of/%2fevil.examplepassesUrl.IsLocalUrlbecause the framework checks only for literal//and/\prefixes. A normalising reverse proxy that decodes percent-encoded path segments can turn that into//evil.exampleon the way out, which browsers treat as a protocol-relative URL.Changes
AccountController.cs: add&& !IsPercentEncodedSlashBypass(redirectUri)to theSignInredirect guard, matching the check onChallenge.AccountController.cs: expand theIsPercentEncodedSlashBypassXML doc to note it is a local copy ofRedirectUriHelper.HasPercentEncodedSlashPrefix(which isinternalin a separate assembly) so future changes keep both in sync.AccountControllerTests.cs: two new tests covering the%2fand%5cvariants on theSignInpath, using the realisticIsLocalUrlmock already present in the test class.