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communication/u2fhid: prepend 0 byte to packet #73

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communication/u2fhid: prepend 0 byte to packet #73

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23f82d1
communication/u2fhid: prepend 0 byte to packet
benma Oct 24, 2022
2549b04
communication/u2fhid: don't hardcode CID check in response
benma Oct 24, 2022
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18 changes: 16 additions & 2 deletions communication/u2fhid/u2fhid.go
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ import (
"bytes"
"encoding/binary"
"io"
"runtime"
"sync"

"github.com/digitalbitbox/bitbox02-api-go/util/errp"
Expand Down Expand Up @@ -103,6 +104,18 @@ func (communication *Communication) sendFrame(msg string) error {
buf.WriteByte(0xee)
}
x := buf.Bytes() // needs to be in a var: https://github.com/golang/go/issues/14210#issuecomment-346402945
if runtime.GOOS != "windows" {
// packets have a 0 byte report ID in front. The karalabe usb library adds it
// automatically for windows, and not for unix, as there, it is stripped by the signal11
// hid library. We have to add it (to be stripped by signal11), otherwise a zero that is
// actually part of the packet would be stripped, leading to a corrupt packet. Our
// packets could start with a zero if e.g. the 4-bytes CID starts with a zero byte
//
// See
// - https://github.com/karalabe/usb/blob/87927bb2c8544d009d8ac7350b1ac892b60c8115/hid_enabled.go#L126-L128.
// - https://github.com/karalabe/usb/blob/87927bb2c8544d009d8ac7350b1ac892b60c8115/hidapi/libusb/hid.c#L1003-L1007
x = append([]byte{0}, x...)
}
_, err := communication.device.Write(x)
return errp.WithMessage(errp.WithStack(err), "Failed to send message")
}
Expand Down Expand Up @@ -153,8 +166,9 @@ func (communication *Communication) readFrame() ([]byte, error) {
if readLen < 7 {
return nil, errp.New("expected minimum read length of 7")
}
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])
replyCid := binary.BigEndian.Uint32(read[:4])
if replyCid != cid {
return nil, errp.Newf("USB command ID mismatch, %v != %v", cid, replyCid)
}
if read[4] != communication.cmd {
return nil, errp.Newf("USB command frame mismatch (%d, expected %d)", read[4], communication.cmd)
Expand Down