communication/u2fhid: parse frame errors

communication/u2fhid/error.go

@@ -0,0 +1,45 @@
+// Copyright 2018-2019 Shift Cryptosecurity AG
+//
+// 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
+//
+// http://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 u2fhid
+
+import "fmt"
+
+const (
+ errCodeChannelBusy = byte(0x06)
+
+ // errCodeChannelNone = byte(0x00)
+ // errCodeChannelInvalidCmd = byte(0x01)
+ // errCodeChannelInvalidPar = byte(0x02)
+ // errCodeChannelInvalidLen = byte(0x03)
+ // errCodeChannelInvalidSeq = byte(0x04)
+ // errCodeChannelMsgTimeout = byte(0x05)
+ // errCodechannellockRequired = byte(0x0A)
+ // errCodechannelInvalidCid = byte(0x0B)
+ // errCodechannelOther = byte(0x7F)
+)
+
+// FrameError is returned when the frame which is read indicates an error.
+// The value within is the error code.
+type FrameError byte
+
+// Error implements error.
+func (e FrameError) Error() string {
+ return fmt.Sprintf("frame error: %d", e)
+}
+
+// IsErrBusy returns true if the error code indicates a busy channel.
+func (e FrameError) IsErrBusy() bool {
+ return byte(e) == errCodeChannelBusy
+}

communication/u2fhid/u2fhid.go

@@ -27,6 +27,8 @@ import (
 const (
  writeReportSize = 64
  readReportSize = 64
+
+ cmdError = 0x80 | 0x3F
 )
 
 const (
@@ -156,12 +158,22 @@ func (communication *Communication) readFrame() ([]byte, error) {
  if read[0] != 0xff || read[1] != 0 || read[2] != 0 || read[3] != 0 {
  return nil, errp.Newf("USB command ID mismatch %d %d %d %d", read[0], read[1], read[2], read[3])
  }
- if read[4] != communication.cmd {
- return nil, errp.Newf("USB command frame mismatch (%d, expected %d)", read[4], communication.cmd)
- }
+
  data := newBuffer()
  dataLen := int(read[5])*256 + int(read[6])
  data.Write(read[7:readLen])
+
+ cmd := read[4]
+ if cmd == cmdError {
+ errCode := byte(0)
+ if data.Len() > 0 {
+ errCode = data.Bytes()[0]
+ }
+ return nil, errp.WithStack(FrameError(errCode))
+ }
+ if cmd != communication.cmd {
+ return nil, errp.Newf("USB command frame mismatch (%d, expected %d)", cmd, communication.cmd)
+ }
  idx := len(read) - 7
  for idx < dataLen {
  readLen, err = communication.device.Read(read)