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// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package piv
import (
"fmt"
"syscall"
"unsafe"
)
var (
winscard = syscall.NewLazyDLL("Winscard.dll")
procSCardEstablishContext = winscard.NewProc("SCardEstablishContext")
procSCardListReadersW = winscard.NewProc("SCardListReadersW")
procSCardReleaseContext = winscard.NewProc("SCardReleaseContext")
procSCardConnectW = winscard.NewProc("SCardConnectW")
procSCardDisconnect = winscard.NewProc("SCardDisconnect")
procSCardBeginTransaction = winscard.NewProc("SCardBeginTransaction")
procSCardEndTransaction = winscard.NewProc("SCardEndTransaction")
procSCardTransmit = winscard.NewProc("SCardTransmit")
)
const (
scardScopeSystem = 2
scardShareExclusive = 1
scardLeaveCard = 0
scardProtocolT1 = 2
scardPCIT1 = 0
maxBufferSizeExtended = (4 + 3 + (1 << 16) + 3 + 2)
rcSuccess = 0
)
func scCheck(rc uintptr) error {
if rc == rcSuccess {
return nil
}
return &scErr{int64(rc)}
}
func isRCNoReaders(rc uintptr) bool {
return rc == 0x8010002E
}
type scContext struct {
ctx syscall.Handle
}
func newSCContext() (*scContext, error) {
var ctx syscall.Handle
r0, _, _ := procSCardEstablishContext.Call(
uintptr(scardScopeSystem),
uintptr(0),
uintptr(0),
uintptr(unsafe.Pointer(&ctx)),
)
if err := scCheck(r0); err != nil {
return nil, err
}
return &scContext{ctx: ctx}, nil
}
func (c *scContext) Close() error {
r0, _, _ := procSCardReleaseContext.Call(uintptr(c.ctx))
return scCheck(r0)
}
func (c *scContext) ListReaders() ([]string, error) {
var n uint32
r0, _, _ := procSCardListReadersW.Call(
uintptr(c.ctx),
uintptr(unsafe.Pointer(nil)),
uintptr(unsafe.Pointer(nil)),
uintptr(unsafe.Pointer(&n)),
)
if isRCNoReaders(r0) {
return nil, nil
}
if err := scCheck(r0); err != nil {
return nil, err
}
d := make([]uint16, n)
r0, _, _ = procSCardListReadersW.Call(
uintptr(c.ctx),
uintptr(unsafe.Pointer(nil)),
uintptr(unsafe.Pointer(&d[0])),
uintptr(unsafe.Pointer(&n)),
)
if err := scCheck(r0); err != nil {
return nil, err
}
var readers []string
j := 0
for i := 0; i < len(d); i++ {
if d[i] != 0 {
continue
}
readers = append(readers, syscall.UTF16ToString(d[j:i]))
j = i + 1
if d[i+1] == 0 {
break
}
}
return readers, nil
}
func (c *scContext) Connect(reader string) (*scHandle, error) {
var (
handle syscall.Handle
activeProtocol uint16
)
r0, _, _ := procSCardConnectW.Call(
uintptr(c.ctx),
uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(reader))),
scardShareExclusive,
scardProtocolT1,
uintptr(unsafe.Pointer(&handle)),
uintptr(activeProtocol),
)
if err := scCheck(r0); err != nil {
return nil, err
}
return &scHandle{handle}, nil
}
type scHandle struct {
handle syscall.Handle
}
func (h *scHandle) Close() error {
r0, _, _ := procSCardDisconnect.Call(uintptr(h.handle), scardLeaveCard)
return scCheck(r0)
}
func (h *scHandle) Begin() (*scTx, error) {
r0, _, _ := procSCardBeginTransaction.Call(uintptr(h.handle))
if err := scCheck(r0); err != nil {
return nil, err
}
return &scTx{h.handle}, nil
}
func (t *scTx) Close() error {
r0, _, _ := procSCardEndTransaction.Call(uintptr(t.handle), scardLeaveCard)
return scCheck(r0)
}
type scTx struct {
handle syscall.Handle
}
func (t *scTx) transmit(req []byte) (more bool, b []byte, err error) {
var resp [maxBufferSizeExtended]byte
reqN := len(req)
respN := len(resp)
r0, _, _ := procSCardTransmit.Call(
uintptr(t.handle),
uintptr(scardPCIT1),
uintptr(unsafe.Pointer(&req[0])),
uintptr(reqN),
uintptr(0),
uintptr(unsafe.Pointer(&resp[0])),
uintptr(unsafe.Pointer(&respN)),
)
if err := scCheck(r0); err != nil {
return false, nil, fmt.Errorf("transmitting request: %w", err)
}
if respN < 2 {
return false, nil, fmt.Errorf("scard response too short: %d", respN)
}
sw1 := resp[respN-2]
sw2 := resp[respN-1]
if sw1 == 0x90 && sw2 == 0x00 {
return false, resp[:respN-2], nil
}
if sw1 == 0x61 {
return true, resp[:respN-2], nil
}
return false, nil, &apduErr{sw1, sw2}
}
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