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ykoath.go
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ykoath.go
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package ykoath
import (
"fmt"
"strings"
"time"
"github.com/ebfe/scard"
"github.com/pkg/errors"
)
type card interface {
Disconnect(scard.Disposition) error
Transmit([]byte) ([]byte, error)
}
type context interface {
Release() error
}
type debugger func(string, ...interface{})
// OATH implements most parts of the TOTP portion of the YKOATH specification
// https://developers.yubico.com/OATH/YKOATH_Protocol.html
type OATH struct {
card card
Clock func() time.Time
context context
Debug debugger
}
const (
errFailedToConnect = "failed to connect to reader"
errFailedToDisconnect = "failed to disconnect from reader"
errFailedToEstablishContext = "failed to establish context"
errFailedToListReaders = "failed to list readers"
errFailedToListSuitableReader = "no suitable reader found (out of %d readers)"
errFailedToReleaseContext = "failed to release context"
errFailedToTransmit = "failed to transmit APDU"
errUnknownTag = "unknown tag (%x)"
)
// New initializes a new OATH session
func New() (*OATH, error) {
context, err := scard.EstablishContext()
if err != nil {
return nil, errors.Wrapf(err, errFailedToEstablishContext)
}
readers, err := context.ListReaders()
if err != nil {
return nil, errors.Wrapf(err, errFailedToListReaders)
}
for _, reader := range readers {
if strings.Contains(strings.ToLower(reader), "canokey") {
card, err := context.Connect(reader, scard.ShareShared, scard.ProtocolAny)
if err != nil {
return nil, errors.Wrapf(err, errFailedToConnect)
}
return &OATH{
card: card,
Clock: time.Now,
context: context,
}, nil
}
}
return nil, fmt.Errorf(errFailedToListSuitableReader, len(readers))
}
// Close terminates an OATH session
func (o *OATH) Close() error {
if err := o.card.Disconnect(scard.LeaveCard); err != nil {
return errors.Wrapf(err, errFailedToDisconnect)
}
if err := o.context.Release(); err != nil {
return errors.Wrapf(err, errFailedToReleaseContext)
}
return nil
}
// send sends an APDU to the card
func (o *OATH) send(cla, ins, p1, p2 byte, data ...[]byte) (tvs, error) {
var (
code code
results []byte
send = append([]byte{cla, ins, p1, p2}, write(0x00, data...)...)
)
for {
if o.Debug != nil {
o.Debug("SEND % x (%d)", send, len(send))
}
res, err := o.card.Transmit(send)
if err != nil {
return nil, errors.Wrapf(err, errFailedToTransmit)
}
if o.Debug != nil {
o.Debug("RECV % x (%d)", res, len(res))
}
code = res[len(res)-2:]
results = append(results, res[0:len(res)-2]...)
if code.IsMore() {
send = []byte{0x00, 0xa5, 0x00, 0x00, code[1]}
if o.Debug != nil {
o.Debug("MORE %d", int(code[1]))
}
} else if code.IsSuccess() {
if o.Debug != nil {
o.Debug("DONE")
}
return read(results), nil
} else {
return nil, code
}
}
}