adding Shared access to multiple processes

[rajnikant12345]

Related: #47

[ericchiang]

This probably won't work. Even if you have a shared connection, as soon as you open a transaction you block the card until the transaction is closed:

piv-go/piv/piv.go

Lines 162 to 169 in 4b80d66

	tx, err := h.Begin()
	if err != nil {
	return nil, fmt.Errorf("beginning smart card transaction: %w", err)
	}
	if err := ykSelectApplication(tx, aidPIV[:]); err != nil {
	tx.Close()
	return nil, fmt.Errorf("selecting piv applet: %w", err)
	}

We probably need to replace accesses to the YubiKey.tx field with a function that either reuses the one transaction in exclusive mode, or creates then closes the connection after.

func (yk *YubiKey) withTx(fn func(tx * scTx) error) error {
   // ...
}

Then functions go from

// Serial returns the YubiKey's serial number.
func (yk *YubiKey) Serial() (uint32, error) {
	return ykSerial(yk.tx, yk.version)
}

To

// Serial returns the YubiKey's serial number.
func (yk *YubiKey) Serial() (uint32, error) {
	var serial uint32
	err := yk.withTx(func(tx *scTx) error {
		var err error
		serial, err = ykSerial(tx, yk.version)
		return err
	})
	return serial, err
}

[ericchiang]

@rajnikant12345 would you like me to take over this one?

[rajnikant12345]

@rajnikant12345 would you like me to take over this one?

Yes that would be great, because this issue is moved to November on my side.

Thanks a lot

[rajnikant12345]

@ericchiang , sorry for late checkin. I was busy with other related stories.
I created a pull request.Please review.
Whenever you get time.
Thanks

[rajnikant12345]

@ericchiang is this already checked in from your side?

Thanks
Rajni

[ericchiang]

Thanks for the follow up! Sorry for the delay, but please ping if you need me to run the CI

[rajnikant12345]

Thanks @ericchiang for reviewing
I was busy with my new born 👶🏻, so got a bit delayed.
I tried fixing your review comments, please have a look.
we can run CI as well.
Thanks

[rajnikant12345]

@ericchiang anything needed from my side on this?

[ezekiel]

I see there are now some conflicts on the branch - if conflicts were resolved, could this be tested again and potentially merged?