System.Security.Cryptography.Rsa.Tests.EncryptDecrypt.Decrypt_Pkcs1_ErrorsForInvalidPadding(Byte[] data)

[lewing]

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=591354
Build error leg or test failing: System.Security.Cryptography.Rsa.Tests.EncryptDecrypt_TrySpan.Decrypt_Pkcs1_ErrorsForInvalidPadding
Pull request: #99287

Error Message

Fill the error message using step by step known issues guidance.

{
  "ErrorMessage": "at System.Security.Cryptography.Rsa.Tests.EncryptDecrypt.Decrypt_Pkcs1_ErrorsForInvalidPadding(Byte[] data)",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=591354
Error message validated: [at System.Security.Cryptography.Rsa.Tests.EncryptDecrypt.Decrypt_Pkcs1_ErrorsForInvalidPadding(Byte[] data)]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 3/6/2024 6:01:33 PM UTC

Report

Build	Definition	Test	Pull Request
591354	dotnet/runtime	System.Security.Cryptography.Rsa.Tests.EncryptDecrypt_TrySpan.Decrypt_Pkcs1_ErrorsForInvalidPadding	#99287
590185	dotnet/runtime	System.Security.Cryptography.Rsa.Tests.EncryptDecrypt_Span.Decrypt_Pkcs1_ErrorsForInvalidPadding	#99263

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
1	2	2

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

Issue Details

---

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=591354
Build error leg or test failing: System.Security.Cryptography.Rsa.Tests.EncryptDecrypt_TrySpan.Decrypt_Pkcs1_ErrorsForInvalidPadding
Pull request: #99287

Error Message

Fill the error message using step by step known issues guidance.

{
  "ErrorMessage": "at System.Security.Cryptography.Rsa.Tests.EncryptDecrypt.Decrypt_Pkcs1_ErrorsForInvalidPadding(Byte[] data)",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Author:	lewing
Assignees:	-
Labels:	area-System.Security, blocking-clean-ci, Known Build Error
Milestone:	-

[bartonjs]

I think this might be a one in a million failure... and we can probably delete the test because it's probably covered by tests added since that one.

Jeremy rambling about probability

OK, for a completely random input; the odds of a successful PKCS1 decryption are

• First byte == 0x00: 1/256 (0.4%)
• Second byte == 0x02: 1/256
• Bytes [2] through [10] not being 0: POWER(255/256, 8) (~97%)
• There's a 0x00 beyond [10]. 1 - POWER(255/256, len - 10).
  • This is a RSA2048 key, so len is 256, so len-10 is 246, so that comes out to about 62%
• 9.14e-6
• Invert that to get the 1-in-a number: 109385

That's for random. This is for derived. That changes the probability to... something. "What are the odds that modpow(x, n, d) and modpow(y, n, d) are both PKCS1-conforming when y2038 = ~x2038, y2037 = ~x2037, ... y2031 = ~x2031; otherwise yi = xi, and modpow(x, n, d) is pkcs-conforming?" Shrug, say one in a million, move on.

Bonus points to anyone who can actually work that out.

[lewing]

happened twice today

[vcsjones]

Clearly my test writing efforts would be better spent on buying lottery tickets.