X509Chain.Build throwing exception on macOS/iOS 26.4 betas

[filipnavara]

We captured numerous occurrences of this error on the latest beta versions of macOS/iOS:

System.Security.Cryptography.Interop+AppleCrypto+AppleCommonCryptoCryptographicException: Unable to decode the provided data.
    at System.Security.Cryptography.X509Certificates.SecTrustChainPal.Execute(:0)
    at System.Security.Cryptography.X509Certificates.ChainPal.BuildChain(:0)
    at System.Security.Cryptography.X509Certificates.X509Chain.Build(:0)
    at Foundation.NSUrlSessionHandler+ServerCertificateCustomValidationCallbackHelper.EvaluateSslPolicyErrors(:0)
    at Foundation.NSUrlSessionHandler+ServerCertificateCustomValidationCallbackHelper.Invoke(:0)
    at Foundation.NSUrlSessionHandler.TryInvokeServerCertificateCustomValidationCallback(:0)
    at Foundation.NSUrlSessionHandler+NSUrlSessionHandlerDelegate.DidReceiveChallengeImpl(:0)
    at Foundation.NSUrlSessionHandler+NSUrlSessionHandlerDelegate.DidReceiveChallenge(:0)
    at InvokeStub_NSUrlSessionHandlerDelegate.DidReceiveChallenge(:0)
    at System.Reflection.MethodBaseInvoker.InvokeWithFewArgs(:0)
    at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw(:0)
    at ObjCRuntime.Runtime.InvokeMethod(:0)
    at ObjCRuntime.Runtime.InvokeMethod(:0)
    at ObjCRuntime.Runtime.bridge_runtime_invoke_method(:0)

We don't have a repro yet, but I am posting it anyway as a heads up that this is something that may eventually require attention. In our case we are still building with .NET 9 runtime on those platforms.

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[vcsjones]

Thanks, I'll have a go at the beta and see if anything stands out.

Any steps / certificates / etc. you discover that reproduce it would be very helpful.

[filipnavara]

Thanks!

Any steps / certificates / etc. you discover that reproduce it would be very helpful.

We are trying to gather more information, but unfortunately we were not able to reproduce it on our machines/phones yet. I didn't try to run the .NET unit tests on the betas yet, so there's a glimpse of hope that it could be hit on some test data. Aside from that we only have data collected from Sentry, on CoreCLR and NativeAOT builds. The only thing that stands out is that all the reports are from the OS betas. Disproportional amount of the reports is from non-English locales, which I would normally ignore but it strikes me as odd.

[vcsjones]

so there's a glimpse of hope that it could be hit on some test data

I tried, clean test run.

[filipnavara]

I did get the error while running tests on the release/9.0 branch:

      System.Security.Cryptography.X509Certificates.Tests.RevocationTests.AiaTests.AiaAcceptsCertTypesAndIgnoresNonCertTypes(aiaResponseKind: Cert, mustIgnore: False) [FAIL]
        System.AggregateException : One or more errors occurred. (Unable to decode the provided data.) (Unable to decode the provided data.) (Unable to decode the provided data.) (Unable to decode the provided data.) (Unable to decode the provided data.)
        ---- Interop+AppleCrypto+AppleCommonCryptoCryptographicException : Unable to decode the provided data.
        ---- Interop+AppleCrypto+AppleCommonCryptoCryptographicException : Unable to decode the provided data.
        ---- Interop+AppleCrypto+AppleCommonCryptoCryptographicException : Unable to decode the provided data.
        ---- Interop+AppleCrypto+AppleCommonCryptoCryptographicException : Unable to decode the provided data.
        ---- Interop+AppleCrypto+AppleCommonCryptoCryptographicException : Unable to decode the provided data.
        Stack Trace:
          /Users/filipnavara/Projects/runtime/src/libraries/Common/tests/TestUtilities/System/RetryHelper.cs(54,0): at System.RetryHelper.Execute(Action test, Int32 maxAttempts, Func`2 backoffFunc, Predicate`1 retryWhen, String testName)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/tests/X509Certificates/RevocationTests/AiaTests.cs(79,0): at System.Security.Cryptography.X509Certificates.Tests.RevocationTests.AiaTests.AiaAcceptsCertTypesAndIgnoresNonCertTypes(AiaResponseKind aiaResponseKind, Boolean mustIgnore)
             at InvokeStub_AiaTests.AiaAcceptsCertTypesAndIgnoresNonCertTypes(Object, Span`1)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Private.CoreLib/src/System/Reflection/MethodBaseInvoker.cs(136,0): at System.Reflection.MethodBaseInvoker.InvokeWithFewArgs(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
          ----- Inner Stack Trace #1 (Interop+AppleCrypto+AppleCommonCryptoCryptographicException) -----
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/ChainPal.Apple.cs(247,0): at System.Security.Cryptography.X509Certificates.SecTrustChainPal.Execute(DateTime verificationTime, Boolean allowNetwork, OidCollection applicationPolicy, OidCollection certificatePolicy, X509RevocationFlag revocationFlag)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/ChainPal.Apple.cs(624,0): at System.Security.Cryptography.X509Certificates.ChainPal.BuildChain(Boolean useMachineContext, ICertificatePal cert, X509Certificate2Collection extraStore, OidCollection applicationPolicy, OidCollection certificatePolicy, X509RevocationMode revocationMode, X509RevocationFlag revocationFlag, X509Certificate2Collection customTrustStore, X509ChainTrustMode trustMode, DateTime verificationTime, TimeSpan timeout, Boolean disableAia)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/X509Chain.cs(126,0): at System.Security.Cryptography.X509Certificates.X509Chain.Build(X509Certificate2 certificate, Boolean throwOnException)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/X509Chain.cs(91,0): at System.Security.Cryptography.X509Certificates.X509Chain.Build(X509Certificate2 certificate)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/tests/X509Certificates/RevocationTests/AiaTests.cs(88,0): at System.Security.Cryptography.X509Certificates.Tests.RevocationTests.AiaTests.<>c__DisplayClass1_1.<AiaAcceptsCertTypesAndIgnoresNonCertTypes>b__0()
          /Users/filipnavara/Projects/runtime/src/libraries/Common/tests/TestUtilities/System/RetryHelper.cs(45,0): at System.RetryHelper.Execute(Action test, Int32 maxAttempts, Func`2 backoffFunc, Predicate`1 retryWhen, String testName)
          ----- Inner Stack Trace #2 (Interop+AppleCrypto+AppleCommonCryptoCryptographicException) -----
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/ChainPal.Apple.cs(247,0): at System.Security.Cryptography.X509Certificates.SecTrustChainPal.Execute(DateTime verificationTime, Boolean allowNetwork, OidCollection applicationPolicy, OidCollection certificatePolicy, X509RevocationFlag revocationFlag)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/ChainPal.Apple.cs(624,0): at System.Security.Cryptography.X509Certificates.ChainPal.BuildChain(Boolean useMachineContext, ICertificatePal cert, X509Certificate2Collection extraStore, OidCollection applicationPolicy, OidCollection certificatePolicy, X509RevocationMode revocationMode, X509RevocationFlag revocationFlag, X509Certificate2Collection customTrustStore, X509ChainTrustMode trustMode, DateTime verificationTime, TimeSpan timeout, Boolean disableAia)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/X509Chain.cs(126,0): at System.Security.Cryptography.X509Certificates.X509Chain.Build(X509Certificate2 certificate, Boolean throwOnException)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/X509Chain.cs(91,0): at System.Security.Cryptography.X509Certificates.X509Chain.Build(X509Certificate2 certificate)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/tests/X509Certificates/RevocationTests/AiaTests.cs(88,0): at System.Security.Cryptography.X509Certificates.Tests.RevocationTests.AiaTests.<>c__DisplayClass1_1.<AiaAcceptsCertTypesAndIgnoresNonCertTypes>b__0()
          /Users/filipnavara/Projects/runtime/src/libraries/Common/tests/TestUtilities/System/RetryHelper.cs(45,0): at System.RetryHelper.Execute(Action test, Int32 maxAttempts, Func`2 backoffFunc, Predicate`1 retryWhen, String testName)
          ----- Inner Stack Trace #3 (Interop+AppleCrypto+AppleCommonCryptoCryptographicException) -----
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/ChainPal.Apple.cs(247,0): at System.Security.Cryptography.X509Certificates.SecTrustChainPal.Execute(DateTime verificationTime, Boolean allowNetwork, OidCollection applicationPolicy, OidCollection certificatePolicy, X509RevocationFlag revocationFlag)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/ChainPal.Apple.cs(624,0): at System.Security.Cryptography.X509Certificates.ChainPal.BuildChain(Boolean useMachineContext, ICertificatePal cert, X509Certificate2Collection extraStore, OidCollection applicationPolicy, OidCollection certificatePolicy, X509RevocationMode revocationMode, X509RevocationFlag revocationFlag, X509Certificate2Collection customTrustStore, X509ChainTrustMode trustMode, DateTime verificationTime, TimeSpan timeout, Boolean disableAia)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/X509Chain.cs(126,0): at System.Security.Cryptography.X509Certificates.X509Chain.Build(X509Certificate2 certificate, Boolean throwOnException)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/X509Chain.cs(91,0): at System.Security.Cryptography.X509Certificates.X509Chain.Build(X509Certificate2 certificate)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/tests/X509Certificates/RevocationTests/AiaTests.cs(88,0): at System.Security.Cryptography.X509Certificates.Tests.RevocationTests.AiaTests.<>c__DisplayClass1_1.<AiaAcceptsCertTypesAndIgnoresNonCertTypes>b__0()
          /Users/filipnavara/Projects/runtime/src/libraries/Common/tests/TestUtilities/System/RetryHelper.cs(45,0): at System.RetryHelper.Execute(Action test, Int32 maxAttempts, Func`2 backoffFunc, Predicate`1 retryWhen, String testName)
          ----- Inner Stack Trace #4 (Interop+AppleCrypto+AppleCommonCryptoCryptographicException) -----
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/ChainPal.Apple.cs(247,0): at System.Security.Cryptography.X509Certificates.SecTrustChainPal.Execute(DateTime verificationTime, Boolean allowNetwork, OidCollection applicationPolicy, OidCollection certificatePolicy, X509RevocationFlag revocationFlag)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/ChainPal.Apple.cs(624,0): at System.Security.Cryptography.X509Certificates.ChainPal.BuildChain(Boolean useMachineContext, ICertificatePal cert, X509Certificate2Collection extraStore, OidCollection applicationPolicy, OidCollection certificatePolicy, X509RevocationMode revocationMode, X509RevocationFlag revocationFlag, X509Certificate2Collection customTrustStore, X509ChainTrustMode trustMode, DateTime verificationTime, TimeSpan timeout, Boolean disableAia)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/X509Chain.cs(126,0): at System.Security.Cryptography.X509Certificates.X509Chain.Build(X509Certificate2 certificate, Boolean throwOnException)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/X509Chain.cs(91,0): at System.Security.Cryptography.X509Certificates.X509Chain.Build(X509Certificate2 certificate)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/tests/X509Certificates/RevocationTests/AiaTests.cs(88,0): at System.Security.Cryptography.X509Certificates.Tests.RevocationTests.AiaTests.<>c__DisplayClass1_1.<AiaAcceptsCertTypesAndIgnoresNonCertTypes>b__0()
          /Users/filipnavara/Projects/runtime/src/libraries/Common/tests/TestUtilities/System/RetryHelper.cs(45,0): at System.RetryHelper.Execute(Action test, Int32 maxAttempts, Func`2 backoffFunc, Predicate`1 retryWhen, String testName)
          ----- Inner Stack Trace #5 (Interop+AppleCrypto+AppleCommonCryptoCryptographicException) -----
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/ChainPal.Apple.cs(247,0): at System.Security.Cryptography.X509Certificates.SecTrustChainPal.Execute(DateTime verificationTime, Boolean allowNetwork, OidCollection applicationPolicy, OidCollection certificatePolicy, X509RevocationFlag revocationFlag)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/ChainPal.Apple.cs(624,0): at System.Security.Cryptography.X509Certificates.ChainPal.BuildChain(Boolean useMachineContext, ICertificatePal cert, X509Certificate2Collection extraStore, OidCollection applicationPolicy, OidCollection certificatePolicy, X509RevocationMode revocationMode, X509RevocationFlag revocationFlag, X509Certificate2Collection customTrustStore, X509ChainTrustMode trustMode, DateTime verificationTime, TimeSpan timeout, Boolean disableAia)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/X509Chain.cs(126,0): at System.Security.Cryptography.X509Certificates.X509Chain.Build(X509Certificate2 certificate, Boolean throwOnException)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/X509Chain.cs(91,0): at System.Security.Cryptography.X509Certificates.X509Chain.Build(X509Certificate2 certificate)
          /Users/filipnavara/Projects/runtime/src/libraries/System.Security.Cryptography/tests/X509Certificates/RevocationTests/AiaTests.cs(88,0): at System.Security.Cryptography.X509Certificates.Tests.RevocationTests.AiaTests.<>c__DisplayClass1_1.<AiaAcceptsCertTypesAndIgnoresNonCertTypes>b__0()
          /Users/filipnavara/Projects/runtime/src/libraries/Common/tests/TestUtilities/System/RetryHelper.cs(45,0): at System.RetryHelper.Execute(Action test, Int32 maxAttempts, Func`2 backoffFunc, Predicate`1 retryWhen, String testName)

[vcsjones]

Okay, I was able to get something reproducing in .NET 10. Some logs:

  SecTrustEvaluateWithError: The operation couldn’t be completed. (com.apple.security.cfder.error error -4 - Unable to get number from data) (domain: com.apple.security.cfder.error, code: -4)
  SecTrustEvaluateWithError: The operation couldn’t be completed. (com.apple.security.cfder.error error -4 - Unable to get number from data) (domain: com.apple.security.cfder.error, code: -4)
  SecTrustEvaluateWithError: The operation couldn’t be completed. (com.apple.security.cfder.error error -4 - Unable to get number from data) (domain: com.apple.security.cfder.error, code: -4)
  SecTrustEvaluateWithError: The operation couldn’t be completed. (com.apple.security.cfder.error error -4 - Unable to get number from data) (domain: com.apple.security.cfder.error, code: -4)
  SecTrustEvaluateWithError: The operation couldn’t be completed. (com.apple.security.cfder.error error -4 - Unable to get number from data) (domain: com.apple.security.cfder.error, code: -4)

This seems difficult to diagnose without better error output or source from Apple.

[vcsjones]

The domain gives us a hint though: com.apple.security.cfder

That usually indicates a DER parsing error. Apple has in the past tightened down X.509 certificate parsing.

Disproportional amount of the reports is from non-English locales, which I would normally ignore but it strikes me as odd.

I wonder if in this case Apple is starting to get pickier about illegal text encodings. Some OpenSSL versions and other certificate software let you do "not technically correct" encodings like put characters outside the character set supported by VisibleString.

Would you expect a lot of these customers to be using in-house CAs?

[filipnavara]

Would you expect a lot of these customers to be using in-house CAs?

Very unlikely. For a moment I entertained the possibility of a MITM "great firewall" infrastructure but there's no pattern suggesting that. The reports come from various countries (Germany, Switzerland, Poland, Czechia, France, in addition to Spanish locales and couple of crashes with messages in Cyrillic). Overall we got 40+ users with crashes on iOS and 20+ users on macOS, nothing obivously common between them. We don't have data of the servers they connect to but based on the email addresses associated with the crashes there's no pattern there either. I analyzed the associated MX records but they don't point to the same providers and they are scattered all over.

[vcsjones]

Assuming I am seeing the same error that other users are:

https://github.com/apple-oss-distributions/Security/blob/db15acbe6a7f257a859ad9a3bb86097bfe0679d9/OSX/utilities/der_number.c#L114-L123

And yes, the -4 from my log matches kSecDERErrorUnsupportedNumberType https://github.com/apple-oss-distributions/Security/blob/db15acbe6a7f257a859ad9a3bb86097bfe0679d9/OSX/utilities/der_plist.h#L41

The only place this error exists in the existing Apple source code is converting a CFNumber to a long long.

There aren't many "numbers" in certificates.

• The version is 0 - 2, so that will be fine.
• The serial number is technically an integer, but it is required to have at least 64-bits of entropy, to trying to convert it to a long long doesn't make sense.

Very unlikely.

If you have a support ticket going with any of them, are they facing certificate problems with other things that use Apple's X.509 handling? If they have a website with the same or similar cert, are they able to browse to it in Safari or connect to it with nscurl?

[filipnavara]

Assuming I am seeing the same error that other users are:

Based on the error messages from customer reports I assumed that the error returned is errSecDecode. That may very well be an incorrect guess...

The only place this error exists in the existing Apple source code...

Yeah, the trouble is that the sources are not updated for beta versions, and this only happens on beta version.

If you have a support ticket going with any of them.

No support tickets so far. This is still very fresh. We do, however, have contacts for many of them, so I can try to see if any of them would share redacted versions of their account settings which should give us some starting point.