Add VALIDATE calls

[ViViDboarder]

My Yubikey Neo is password protected and requires a call to validate the password before listing or performing other actions.

In order to make the magic numbers more readable I added all the ones I found on the Yubico site to constants.go.

Other smaller changes:

• Export CALCULATE as CalculateOne and CALCULATE_ALL as CalculateAll
• Add more error codes to codes.go

This is used as follows:

package main

import (
	"fmt"
	"git.iamthefij.com/iamthefij/slog"
	"github.com/yawn/ykoath"
	"golang.org/x/crypto/ssh/terminal"
	"syscall"
)

func main() {
	oath, err := ykoath.New()
	slog.FatalOnErr(err, "failed to initialize new oath")
	oath.Debug = slog.Debug

	defer oath.Close()

	s, err := oath.Select()
	slog.FatalOnErr(err, "failed to select oath")

	if s.Challenge != nil {
		fmt.Println("Passphrase? ")
		passphrase, err := terminal.ReadPassword(int(syscall.Stdin))
		slog.FatalOnErr(err, "failed reading passphrase")
		key := s.DeriveKey(string(passphrase))

		ok, err := oath.Validate(s, key)
		slog.FatalOnErr(err, "validation failed")
		if !ok {
			panic("could not validate")
		}
	}

	names, err := oath.List()
	slog.FatalOnErr(err, "failed to list names")

	for _, name := range names {
		slog.Log(name.Name)
	}

	otp, err := oath.Calculate(names[0].Name, ykoath.ErrorTouchCallback)
	slog.FatalOnErr(err, "Failed to retrieve otp")
	slog.Log(otp)
}

[yawn]

Awesome PR @ViViDboarder, thanks a lot! Review will be done ~Monday.

[ViViDboarder]

For some reason I started getting 8 digit codes where I was supposed to get 6. I didn't change anything so I wonder if it has something to do with drivers or a dependency. To resolve it, I implemented a similar solution to yubikey-manager

[ViViDboarder]

Any chance of a review in the next week or so? I wrote a cli tool and an Alfred Workflow that depends on this. I can build and distribute binaries using replace in my go.mod for now, but it's easier for others to test and write patches if they can build directly.

[yawn]

Yeah, sorry about that. I'll do the review today / in the afternoon.

[yawn]

Hey @ViViDboarder - are the remaining issues clear? Should we proceed with this PR?

[ViViDboarder]

Thanks @yawn. I'm still a little confused on errors, which I think are the only outstanding items.

The way I understand error handling in Go right now (it seems to change frequently) is that a class should do something like this:

package example

import (
    "errors"
    "fmt"
)

var (
    ErrSomethingNotFound = errors.New("thing not found")
)

func CalledError() error {
    err := maybeHasError()
    if err != nil {
        return fmt.Errorf("error in this thing: %w", err)
    }

    return nil
}

func FindThing(p string) error {
    var b bool
    b = isThingFound(p)
    if !b {
        return fmt.Errorf("error finding %p: %w", p, ErrSomethingNotFound)
    }

    return nil
}

This allows some using the module and function to handle errors from findThing by using the wraps.

package main

import (
    "errors"
    "fmt"

    "example"
)

func main() {
    err = example.FindThing("foo")
    if errors.Is(err, example.ErrSomethingNotFound) {
        fmt.Println("Thing wasn't found")
    } else {
        panic(err)
    }
}

I can definitely do this, but it would be inconsistent with some of the others. I can refactor those as well, but maybe in a different patch.

[yawn]

As an alternative: just add the tests and I'll do the minor / cosmetic changes in your PR? Maybe easier?

[ViViDboarder]

That works for me.

Regarding the tests, I can definitely write some, but I do not have a spare Yubikey to test with. It also looks like I'll need to implement the SET CODE instruction that sets up authentication if a full test is to be written so that auth can be enabled, validated, and disabled.

[yawn]

I can totally live without SET CODE if you can substitute it with a ykman call. For the test environment that's fine. Spare Yubikey, hm - that's an issue of course :-)