Files
VoCat/internal/pcsc/pcscd_protocol.go

335 lines
11 KiB
Go

package pcsc
import (
"context"
"encoding/binary"
"errors"
"fmt"
"io"
"net"
"time"
)
// pcsc-lite exposes a small, versioned protocol over its local Unix socket.
// Speaking that protocol directly keeps VoCat's Linux binaries fully static;
// loading libpcsclite through dlopen would pull a glibc interpreter into an
// otherwise CGO-free build and make it unusable on musl-based routers.
const (
pcscProtocolMajor = 4
pcscProtocolCurrentMinor = 6
pcscProtocolOldestMinor = 4
pcscCmdEstablishContext = 0x01
pcscCmdReleaseContext = 0x02
pcscCmdConnect = 0x04
pcscCmdDisconnect = 0x06
pcscCmdBeginTransaction = 0x07
pcscCmdEndTransaction = 0x08
pcscCmdTransmit = 0x09
pcscCmdGetAttrib = 0x0f
pcscCmdVersion = 0x11
pcscCmdGetReadersState = 0x12
pcscScopeSystem = 0x0002
pcscProtocolT0 = 0x0001
pcscProtocolT1 = 0x0002
pcscProtocolAny = pcscProtocolT0 | pcscProtocolT1
pcscShareShared = 0x0002
pcscShareDirect = 0x0003
pcscLeaveCard = 0x0000
pcscResetCard = 0x0001
pcscCardPresent = 0x0004
pcscAttrChannelID = 0x00020110
pcscMaxReaderName = 128
pcscMaxATR = 33
pcscMaxReaders = 16
pcscReaderStateSize = 184
pcscGetSetBodySize = 280
pcscMaxAttribute = 264
pcscMaxAPDUResponse = 65548
pcscDefaultIOTimeout = 30 * time.Second
pcscSuccess = uint32(0)
pcscNoSmartcard = uint32(0x8010000c)
pcscNoService = uint32(0x8010001d)
pcscServiceStopped = uint32(0x8010001e)
pcscNoReaders = uint32(0x8010002e)
)
type pcscdClient struct {
conn net.Conn
contextID uint32
serverMinor int32
}
type pcscdReaderState struct {
name string
state uint32
atr []byte
protocol uint32
}
func establishPCSCD(ctx context.Context, conn net.Conn) (*pcscdClient, error) {
client := &pcscdClient{conn: conn}
version := make([]byte, 12)
binary.LittleEndian.PutUint32(version[0:4], pcscProtocolMajor)
binary.LittleEndian.PutUint32(version[4:8], pcscProtocolCurrentMinor)
for {
if err := client.exchange(ctx, pcscCmdVersion, version); err != nil {
return nil, err
}
major := int32(binary.LittleEndian.Uint32(version[0:4]))
client.serverMinor = int32(binary.LittleEndian.Uint32(version[4:8]))
rv := binary.LittleEndian.Uint32(version[8:12])
if rv == pcscSuccess {
break
}
if rv != pcscServiceStopped || major != pcscProtocolMajor || client.serverMinor < pcscProtocolOldestMinor || client.serverMinor >= pcscProtocolCurrentMinor {
return nil, pcscError("negotiate protocol", rv)
}
// pcsc-lite answers a newer client's first probe with its own
// compatible minor version. Retry on the same connection with that
// value, matching libpcsclite's official fallback behavior.
binary.LittleEndian.PutUint32(version[0:4], pcscProtocolMajor)
binary.LittleEndian.PutUint32(version[4:8], uint32(client.serverMinor))
binary.LittleEndian.PutUint32(version[8:12], pcscSuccess)
}
if client.serverMinor < pcscProtocolOldestMinor {
return nil, fmt.Errorf("pcsc: unsupported pcscd protocol %d.%d", pcscProtocolMajor, client.serverMinor)
}
body := make([]byte, 12)
binary.LittleEndian.PutUint32(body[0:4], pcscScopeSystem)
if err := client.exchange(ctx, pcscCmdEstablishContext, body); err != nil {
return nil, err
}
if rv := binary.LittleEndian.Uint32(body[8:12]); rv != pcscSuccess {
return nil, pcscError("establish context", rv)
}
client.contextID = binary.LittleEndian.Uint32(body[4:8])
return client, nil
}
func (client *pcscdClient) exchange(ctx context.Context, command uint32, body []byte) error {
if client == nil || client.conn == nil {
return errors.New("pcsc: pcscd connection is closed")
}
if err := client.setDeadline(ctx); err != nil {
return err
}
header := make([]byte, 8)
binary.LittleEndian.PutUint32(header[0:4], uint32(len(body)))
binary.LittleEndian.PutUint32(header[4:8], command)
if err := writeAll(client.conn, header); err != nil {
return fmt.Errorf("pcsc: send command %02x: %w", command, err)
}
if len(body) > 0 {
if err := writeAll(client.conn, body); err != nil {
return fmt.Errorf("pcsc: send command body %02x: %w", command, err)
}
if _, err := io.ReadFull(client.conn, body); err != nil {
return fmt.Errorf("pcsc: receive command %02x: %w", command, err)
}
}
return nil
}
func (client *pcscdClient) send(ctx context.Context, command uint32, body, extra []byte) error {
if client == nil || client.conn == nil {
return errors.New("pcsc: pcscd connection is closed")
}
if err := client.setDeadline(ctx); err != nil {
return err
}
header := make([]byte, 8)
binary.LittleEndian.PutUint32(header[0:4], uint32(len(body)))
binary.LittleEndian.PutUint32(header[4:8], command)
if err := writeAll(client.conn, header); err != nil {
return err
}
if err := writeAll(client.conn, body); err != nil {
return err
}
return writeAll(client.conn, extra)
}
func (client *pcscdClient) setDeadline(ctx context.Context) error {
if err := ctx.Err(); err != nil {
return err
}
deadline := time.Now().Add(pcscDefaultIOTimeout)
if value, ok := ctx.Deadline(); ok && value.Before(deadline) {
deadline = value
}
return client.conn.SetDeadline(deadline)
}
func (client *pcscdClient) readers(ctx context.Context) ([]pcscdReaderState, error) {
if err := client.setDeadline(ctx); err != nil {
return nil, err
}
header := make([]byte, 8)
binary.LittleEndian.PutUint32(header[4:8], pcscCmdGetReadersState)
if err := writeAll(client.conn, header); err != nil {
return nil, fmt.Errorf("pcsc: request reader states: %w", err)
}
raw := make([]byte, pcscMaxReaders*pcscReaderStateSize)
if _, err := io.ReadFull(client.conn, raw); err != nil {
return nil, fmt.Errorf("pcsc: read reader states: %w", err)
}
result := make([]pcscdReaderState, 0, pcscMaxReaders)
for offset := 0; offset < len(raw); offset += pcscReaderStateSize {
state := raw[offset : offset+pcscReaderStateSize]
name := cString(state[:pcscMaxReaderName])
if name == "" {
continue
}
atrLen := int(binary.LittleEndian.Uint32(state[176:180]))
if atrLen < 0 || atrLen > pcscMaxATR {
atrLen = 0
}
result = append(result, pcscdReaderState{
name: name,
state: binary.LittleEndian.Uint32(state[132:136]),
atr: append([]byte(nil), state[140:140+atrLen]...),
protocol: binary.LittleEndian.Uint32(state[180:184]),
})
}
return result, nil
}
func (client *pcscdClient) connect(ctx context.Context, reader string, share, protocols uint32) (int32, uint32, error) {
if len(reader) >= pcscMaxReaderName {
return 0, 0, errors.New("pcsc: reader name is too long")
}
body := make([]byte, 152)
binary.LittleEndian.PutUint32(body[0:4], client.contextID)
copy(body[4:132], reader)
binary.LittleEndian.PutUint32(body[132:136], share)
binary.LittleEndian.PutUint32(body[136:140], protocols)
if err := client.exchange(ctx, pcscCmdConnect, body); err != nil {
return 0, 0, err
}
if rv := binary.LittleEndian.Uint32(body[148:152]); rv != pcscSuccess {
return 0, 0, pcscError("connect reader", rv)
}
return int32(binary.LittleEndian.Uint32(body[140:144])), binary.LittleEndian.Uint32(body[144:148]), nil
}
func (client *pcscdClient) simpleCardCommand(ctx context.Context, command uint32, card int32, disposition *uint32) error {
size := 8
if disposition != nil {
size = 12
}
body := make([]byte, size)
binary.LittleEndian.PutUint32(body[0:4], uint32(card))
if disposition != nil {
binary.LittleEndian.PutUint32(body[4:8], *disposition)
}
if err := client.exchange(ctx, command, body); err != nil {
return err
}
if rv := binary.LittleEndian.Uint32(body[size-4:]); rv != pcscSuccess {
return pcscError("card command", rv)
}
return nil
}
func (client *pcscdClient) transmit(ctx context.Context, card int32, protocol uint32, command []byte) ([]byte, error) {
body := make([]byte, 32)
binary.LittleEndian.PutUint32(body[0:4], uint32(card))
binary.LittleEndian.PutUint32(body[4:8], protocol)
binary.LittleEndian.PutUint32(body[8:12], 8)
binary.LittleEndian.PutUint32(body[12:16], uint32(len(command)))
binary.LittleEndian.PutUint32(body[16:20], pcscProtocolAny)
binary.LittleEndian.PutUint32(body[20:24], 8)
binary.LittleEndian.PutUint32(body[24:28], pcscMaxAPDUResponse)
if err := client.send(ctx, pcscCmdTransmit, body, command); err != nil {
return nil, fmt.Errorf("pcsc: transmit APDU: %w", err)
}
if _, err := io.ReadFull(client.conn, body); err != nil {
return nil, fmt.Errorf("pcsc: receive APDU result: %w", err)
}
if rv := binary.LittleEndian.Uint32(body[28:32]); rv != pcscSuccess {
return nil, pcscError("transmit APDU", rv)
}
length := binary.LittleEndian.Uint32(body[24:28])
if length > pcscMaxAPDUResponse {
return nil, errors.New("pcsc: pcscd returned an oversized APDU")
}
response := make([]byte, length)
if _, err := io.ReadFull(client.conn, response); err != nil {
return nil, fmt.Errorf("pcsc: receive APDU: %w", err)
}
return response, nil
}
func (client *pcscdClient) getAttrib(ctx context.Context, card int32, attribute uint32) ([]byte, error) {
body := make([]byte, pcscGetSetBodySize)
binary.LittleEndian.PutUint32(body[0:4], uint32(card))
binary.LittleEndian.PutUint32(body[4:8], attribute)
binary.LittleEndian.PutUint32(body[272:276], pcscMaxAttribute)
if err := client.exchange(ctx, pcscCmdGetAttrib, body); err != nil {
return nil, err
}
if rv := binary.LittleEndian.Uint32(body[276:280]); rv != pcscSuccess {
return nil, pcscError("get reader attribute", rv)
}
length := binary.LittleEndian.Uint32(body[272:276])
if length > pcscMaxAttribute {
return nil, errors.New("pcsc: pcscd returned an oversized attribute")
}
return append([]byte(nil), body[8:8+length]...), nil
}
func (client *pcscdClient) closeContext(ctx context.Context) error {
if client == nil || client.conn == nil {
return nil
}
body := make([]byte, 8)
binary.LittleEndian.PutUint32(body[0:4], client.contextID)
err := client.exchange(ctx, pcscCmdReleaseContext, body)
if err == nil {
if rv := binary.LittleEndian.Uint32(body[4:8]); rv != pcscSuccess {
err = pcscError("release context", rv)
}
}
closeErr := client.conn.Close()
client.conn = nil
return errors.Join(err, closeErr)
}
func pcscError(operation string, code uint32) error {
switch code {
case pcscNoSmartcard:
return ErrNoCard
case pcscNoService, pcscServiceStopped:
return fmt.Errorf("%w: %s failed with PC/SC status %08X", ErrUnavailable, operation, code)
case pcscNoReaders:
return ErrReaderNotFound
default:
return fmt.Errorf("pcsc: %s failed with status %08X", operation, code)
}
}
func cString(value []byte) string {
for index, current := range value {
if current == 0 {
return string(value[:index])
}
}
return string(value)
}
func writeAll(writer io.Writer, value []byte) error {
for len(value) > 0 {
written, err := writer.Write(value)
if err != nil {
return err
}
if written == 0 {
return io.ErrUnexpectedEOF
}
value = value[written:]
}
return nil
}