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[Bug] Race condition on ConfigurationManager._syncAfter #2900

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bruno-brant opened this issue Oct 11, 2024 · 5 comments · May be fixed by #2988
Open
1 of 14 tasks

[Bug] Race condition on ConfigurationManager._syncAfter #2900

bruno-brant opened this issue Oct 11, 2024 · 5 comments · May be fixed by #2988
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@brentschmaltz
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Bug Product is not functioning as expected P1 More important, prioritize highly

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@bruno-brant
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Which version of Microsoft.IdentityModel are you using?
Microsoft.IdentityModel 8.1.2

Where is the issue?

  • M.IM.JsonWebTokens
  • M.IM.KeyVaultExtensions
  • M.IM.Logging
  • M.IM.ManagedKeyVaultSecurityKey
  • M.IM.Protocols
  • M.IM.Protocols.OpenIdConnect
  • M.IM.Protocols.SignedHttpRequest
  • M.IM.Protocols.WsFederation
  • M.IM.TestExtensions
  • M.IM.Tokens
  • M.IM.Tokens.Saml
  • M.IM.Validators
  • M.IM.Xml
  • S.IM.Tokens.Jwt
  • Other (please describe)

Description

Every calling thread to ConfigurationManager.GetConfigurationAsync will result in a read to _syncAfter to check if a sync should be started; later, a background thread will update _syncAfter with the new sync time. syncAfter is a DateTimeOffset, a struct, so writes to it aren't atomic, so there's a possibility that the calling thread will read corrupt data.

Possible solution

  • Rewrite _syncAfter so that it can be atomically read/written - we could refactor it to be total seconds (int32) or any other type that is atomic.
  • Rearchitect the metadata refresh to happen completely in the background, to avoid every calling thread having to access the syncAfter variable.

Additional context / logs / screenshots / links to code
@jennyf19 jennyf19 added P1 More important, prioritize highly Bug Product is not functioning as expected and removed needs attention untriaged labels Oct 11, 2024
@jennyf19
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FYI @brentschmaltz

@brentschmaltz
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I like the idea to use Epoch time as a long.

@bruno-brant
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bruno-brant commented Oct 14, 2024 •
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I like the idea to use Epoch time as a long.

Longs can still cause an issue in 32-bit architectures unless we use Interlocked or any other synchronization strategy. A int32 is always atomic.

Given the use case, maybe an int32 would suffice? I know the max time shouldn't larger than an int.MaxValue, not sure if the subtraction is cheaper than an interlocked though.

@keegan-caruso
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@brentschmaltz We don't need to store the epoch time, just the offset, which should always be capturable in an int. I think this is the point @bruno-brant is trying to make.

@brentschmaltz
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@keegan-caruso that makes sense also, hadn't thought about 32bit architectures, that is a good point and should be considered.

@brentschmaltz brentschmaltz self-assigned this Oct 22, 2024
@pmaytak pmaytak linked a pull request Nov 8, 2024 that will close this issue
Use int to guard when metadata update is due #2988
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@bruno-brant @brentschmaltz @jennyf19 @keegan-caruso