Fix missing object-level authorization (IDOR) in C# and ASP.NET Core
====================================================================

Read the user's ID, tenant and role from the ClaimsPrincipal your
authentication scheme builds, never from the request, and scope every invoice
query with tenant_id = $tenant AND (owner_id = $user OR $isBillingAdmin).
Detail, list and export then return only rows the caller may read; answer 404
otherwise. In a resource-based AuthorizationHandler, check the tenant before
the admin role.

Page: https://softwaresecurity.com/fix/missing-authorization/csharp-aspnetcore/

What is in this archive
-----------------------
missing-authorization/csharp-aspnetcore/   the project: three implementations of the same code and one test suite
  src/Invoices/impl/VulnerableInvoiceService.cs   (vulnerable)
  src/Invoices/impl/FixedInvoiceService.cs   (fixed)
  src/Invoices/impl/WrongInvoiceService.cs   (a plausible fix that still fails)
run-all.mjs   runs the tests in all three modes and checks the results (Node.js only)
LICENSE-CODE.txt

Run it
------
  Tested with .NET 10.0.12 (SDK 10.0.112). run-all.mjs needs Node.js 22 or
  later. Supported versions: https://softwaresecurity.com/fix/versions/

  From the missing-authorization/csharp-aspnetcore folder, install the
  dependencies once (this needs network access):

    dotnet restore tests/Invoices.Tests --locked-mode

  Then run the tests. IMPL chooses the implementation the tests load:

    # every test passes
    IMPL=fixed dotnet test --project tests/Invoices.Tests --no-restore --results-directory reports --report-xunit-junit --report-xunit-junit-filename junit.xml
    # an exploit test fails
    IMPL=vulnerable dotnet test --project tests/Invoices.Tests --no-restore --results-directory reports --report-xunit-junit --report-xunit-junit-filename junit.xml
    # a test fails
    IMPL=wrong dotnet test --project tests/Invoices.Tests --no-restore --results-directory reports --report-xunit-junit --report-xunit-junit-filename junit.xml

  The JUnit report is written to reports/junit.xml. To run all three modes and
  check the results in one step, run the harness from this top folder (it needs
  only Node.js; --install runs the install step first):

    node run-all.mjs --install missing-authorization/csharp-aspnetcore
    node run-all.mjs missing-authorization/csharp-aspnetcore

Verified
--------
  11 October 2026 on macOS 27.0 (arm64), with dotnetSdk 10.0.112, dotnetRuntime
  10.0.12, sqlite 3.53.3. Versions and results hold for that date: run the tests
  with your own versions before relying on the fix.

Licence
-------
  The code is MIT licensed (LICENSE-CODE.txt). The page text is CC BY 4.0.
