[ci-scan] Test failure: System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext

[github-actions]

Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1563837
Build error leg or test failing: android-arm Release AllSubsets_CoreCLR - System.Security.Cryptography.Tests
Recurs in follow-up build https://dev.azure.com/dnceng-public/public/_build/results?buildId=1564198 (runtime-extra-platforms, def 154).

KBE authoring guidance (ci-failure-scan)

• Error Details is for readers. Paste the full exception, stack trace, or build error excerpt so the failure is understandable without opening the raw log.
• Build Analysis parses only the single JSON block under Error Message.
• ErrorMessage is a case-sensitive ordinal String.Contains substring copied verbatim from the failing log.
• Set BuildRetry to true only for a clear infrastructure retry case. ExcludeConsoleLog disables Helix console-log scanning.

Error Details

[FAIL] System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext
   Test name: System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext(testCase: NIST GCM Spec test cases - 2 (128/96/128/128/0))
   Exception messages: Assert.Throws() Failure: Exception type was not an exact match
Expected: typeof(System.Security.Cryptography.AuthenticationTagMismatchException)
Actual:   typeof(System.Security.Cryptography.CryptographicException)

The AES-GCM tampered-ciphertext test expects an AuthenticationTagMismatchException but the mobile crypto backend throws the base CryptographicException instead.

Error Message

{
  "ErrorMessage": [
    "[FAIL] System.Security.Cryptography.Tests.AesGcmTests",
    "Expected: typeof(System.Security.Cryptography.AuthenticationTagMismatchException)",
    "Actual:   typeof(System.Security.Cryptography.CryptographicException)"
  ],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Agentic workflow metadata (ci-failure-scan)

Workflow artifact: ci-failure-scan
Artifact kind: kbe-verification
Verified match count: 1 hits in failure.log

Generated by CI Outer-Loop Failure Scanner · opus48 · 573.8 AIC · ⌖ 11.3 AIC · ⊞ 20.7K · ◷

Report

Build	Repository	Test	Pull Request
1594486	dotnet/runtime	System.Security.Cryptography.Tests.WorkItemExecution
1580801	dotnet/runtime	System.Security.Cryptography.Tests.WorkItemExecution
1572439	dotnet/runtime	System.Security.Cryptography.Tests.WorkItemExecution	#132887
1571812	dotnet/runtime	System.Security.Cryptography.Tests.WorkItemExecution
1567845	dotnet/runtime	System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext
1566157	dotnet/runtime	System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext
1564198	dotnet/runtime	System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext
1563837	dotnet/runtime	System.Security.Cryptography.Tests.AesGcmTests.AesGcmNistTestsTamperCiphertext

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	0	8

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1563837
Error message validated: [[FAIL] System.Security.Cryptography.Tests.AesGcmTests Expected: typeof(System.Security.Cryptography.AuthenticationTagMismatchException) Actual: typeof(System.Security.Cryptography.CryptographicException)]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 8/28/2026 11:48:29 AM UTC

[vcsjones]

This looks like the same thing as the ChaCha one. Something is polluting Conscrypt's error queue.

Will take a look.

[dotnet-policy-service]

Tagging subscribers to this area: @bartonjs, @vcsjones, @dotnet/area-system-security
See info in area-owners.md if you want to be subscribed.

[dotnet-policy-service]

Tagging subscribers to 'arch-android': @vitek-karas, @simonrozsival, @steveisok, @akoeplinger
See info in area-owners.md if you want to be subscribed.

[github-actions]

Workflow artifact: ci-fix
Artifact kind: handoff
Linked KBE: #132696

Note

AI/Copilot-generated triage note.

This Known Build Error has no producible automated code change (reason: security/platform-crypto behavior decision), so I could not open a best-effort PR without guessing area-owner intent. Looping in owners so it can be fixed forward rather than muted.

Root cause (best analysis)

On Android (android-arm, android-arm64) AllSubsets_CoreCLR, AesGcmTests.AesGcmNistTestsTamperCiphertext expects the tampered-ciphertext decrypt to throw AuthenticationTagMismatchException, but the Android AES-GCM backend throws the base CryptographicException instead. AuthenticationTagMismatchException derives from CryptographicException, so the mismatch is that the Android crypto interop path does not surface the specialized tag-mismatch type on GCM authentication failure. Whether the correct fix is to map the Android provider's authentication-failure result to AuthenticationTagMismatchException (product change in the Android crypto interop) or to relax the test on that platform is a security-area-owner decision, so I am not guessing an expectation change here.

Evidence

• Failing build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1563837 (reproduces in 1564198)
• First build it occurred: source build 1563837 (within the scanned window; may not be the true origin)
• Possible related PR: none identified with sufficient confidence

Suggested reviewers / area contacts

• Area owners (area-System.Security): @bartonjs, @dotnet/area-system-security

A fix likely involves mapping the Android AES-GCM authentication-failure return to AuthenticationTagMismatchException in the platform crypto interop so behavior matches other platforms.

Structured data:

{
  "artifact_kind": "handoff",
  "linked_kbe": 132696,
  "workflow_artifact": "ci-fix"
}

Generated by CI Outer-Loop Failure Fixer · opus48 · 444.8 AIC · ⌖ 28.9 AIC · ⊞ 19.6K · ◷