Safer transaction: add End() method and don't use as error #15
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This was referenced Oct 12, 2023
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msteinert
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Nov 29, 2023
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Hi Marco, sorry for the delay in reviewing! I haven't been able to make much time for open source lately.
This looks really good, I'm excited for the 2.0 release. Let me know what you think. I'm willing to make some of the changes I suggested if you're feeling burned out on this project.
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And use them instead of C ones. Given that we have strings for them we can easily implement error interfaces for it too.
Use pam_debug.so to generate pam configurations at test time and check if the returned values expect the ones we want.
If the transaction fails during start, there's no way to get the error detail in a programmatic way, so let's wrap the pam.Error to allow more per-type checks.
…atus All the pam functions return an integer with the status of the operation so instead of duplicating the same code everywhere, that is quite error prone, use an helper function. It would have been nice to make this more dynamic, but cgo doesn't allow us to do much magic here. This is enough though.
Transactions save the status of each operation in a status field, however such field could be written concurrently by various operations, so we need to be sure that: - We always return the status for the current operation - We store the status in a atomic way so that other actions won't create write races In general, in a multi-thread operation one should not rely on Transaction.Error() to get info about the last operation.
While transaction does implement error, it's not a valid error implementer because it may have bogous values since it's not thread-safe and so we may read the result of Error() when it's into an invalid state As per this never return it as an error, while always return the Status unless when not available, where we still return pam.Error.
…more As per previous commit, Transaction can't be used anymore as an error value, but we instead we always return the status code.
A PAM transaction needs to be ended in order to release the associated resources, however this can't be sadly automated as the go finalizers run in goroutines and this could cause problems to modules that we load. In fact a module code may be called back during pam_end (to cleanup data for example) and the module code could not be thread safe. So let's make this more manual, but safer. The transaction status is still preserved in the transaction so end will be automatically called with the last-known status. Closes: msteinert#14
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Check if a transaction is ended in in tests.
…nd Style types We redefined various PAM constant values for items, flags and style, but only few of them were marked as being Item's or Flag's. This caused go to just consider them as generic integers instead of the actual subtype.
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As per discussions we had, Transaction is not fully thread safe and the fact it could be returned as an error makes things worse because its Error() value, that depends on the state could be changed while it's processed.
So:
End()method.These are both breaking changes, but would simplify #13 too.
Closes: #14
Note that this also includes #16