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proposal: crypto/tls: make maxHandshake configurable #50773
Comments
Yes: making something configurable is backwards-compatible as long as the default behavior remains the same. (We can be certain that no existing program configures it to anything other than the default.) |
cc @golang/security |
CC @golang/security Looks like this didn't make 1.19. Moving to backlog. Please recategorize as appropriate. Thanks. |
I've found real-world case where I can't connect to development server. The server has some extremely long list of SANs, but the certificate is still valid and works for at least for Also JDK has it's setting |
Is there a concrete API proposal here, It sounds like essentially what is wanted is a new field on tls.Config? i.e.
|
What is the best way to move this forward? I can create an API proposal (similar to this) and provide an implementation if desired. |
What version of Go are you using (
go version
)?Does this issue reproduce with the latest release?
Yes
What operating system and processor architecture are you using (
go env
)?go env
OutputWhat did you do?
What did you expect to see?
I expected the connection to succeed.
What did you see instead?
tls: handshake message of length 110013 bytes exceeds maximum of 65536 bytes
The limit is defined here:
and it says that the protocol max is 16 MB, not 64 KiB. I assume this hard limit is to mitigate resource exhaustion attacks, but it would be preferable if it was configurable.
Context
We dynamically generate certificates for mTLS within and across clusters and configure which services are allowed to open connections between each other using Subject Alternative Names. In extreme cases a service that needs to communicate with many other services could have a certificate that's larger than this limit.
This isn't a problem right now but a limit of 64 KiB provides a fairly small and uncomfortable safety buffer. Is there a reason that this limit is not configurable?
This issue is related to #35153 where @FiloSottile says "Documenting something makes it a backwards compatibility promise". Is making it configurable still possible while preserving backwards compatibility in the future?
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