SCardGetStatusChange: Race condition when attaching multiple readers at the same time about pcsc HOT 8 CLOSED

Fixed in pcsc-lite 2.3.0.

See https://blog.apdu.fr/posts/2024/08/improved-scardgetstatuschange-for-pnpnotification-special-reader/

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Does it solve the problem for you?

yes it does! thank you 👍

from pcsc.

Yes, it is a known limitation of SCardGetStatusChange(). You can't detect a reader connection/disconnection between 2 calls of SCardGetStatusChange().

One solution would be to use dwEventState for the special reader \\?PnP?\Notification to store the number of reader events. If that number has changed between two calls of SCardGetStatusChange() then we return.

This field is already used by Windows to store the number of readers. I could not find the documentation for that.
See https://salsa.debian.org/rousseau/PCSC/-/issues/5

from pcsc.

Thank you for your response. IMHO an event count would be better as the number of readers may loose events if a reader is detached and another is attached between two calls of SCardGetStatusChange(). However, that seems rather theoretic and I cannot oversee the Windows / macOS situation.

I read your comment I don't think it is a good idea to implement something that would work for pcsc-lite only, and not for Windows or macOS. so that this will not / cannot be fixed any time soon, sadly. Feel free to close this ticket if you like.

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I may implement the idea I presented. It will only work on GNU/Linux but at least it would be possible to have a "safe" SCardGetStatusChange() on this platform.

I do not expect Apple or Microsoft to do anything on their own implementation of WinSCard.

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I think I fixed the issue in a beta version.
See http://lists.infradead.org/pipermail/pcsclite-muscle/2024-June/001498.html

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Hello @kgraefe
Have you had a chance to test my proposed code?
Does it solve the problem for you?

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It's on my list. I could not find the time yet.

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