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// Copyright 2021 Northern.tech AS
//
// 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.
//go:build linux || aix || darwin || dragonfly || freebsd || netbsd || opbenbsd
// +build linux aix darwin dragonfly freebsd netbsd opbenbsd
package util
import (
"context"
"os"
"github.com/pkg/errors"
"golang.org/x/sys/unix"
)
// Disable TTY echo of stdin.
func DisableEcho(fd int) (*unix.Termios, error) {
term, err := unix.IoctlGetTermios(fd, ioctlGetTermios)
if err != nil {
return nil, err
}
newTerm := *term
newTerm.Lflag &^= unix.ECHO
newTerm.Lflag |= unix.ICANON | unix.ISIG
newTerm.Iflag |= unix.ICRNL
if err := unix.IoctlSetTermios(fd, ioctlSetTermios, &newTerm); err != nil {
return nil, err
}
return term, nil
}
// Signal handler to re-enable tty echo on interrupt. The signal handler is
// transparent with system default, and immedeately releases the channel and
// calling the system sighandler after termios is set.
func EchoSigHandler(
ctx context.Context,
sigChan chan os.Signal,
errChan chan error,
term *unix.Termios) {
for {
var (
sig os.Signal
sigRecved bool
)
select {
case <-ctx.Done():
errChan <- nil
return
case sig, sigRecved = <-sigChan:
}
if sig == unix.SIGWINCH || sig == unix.SIGURG {
// Though SIGCHLD is ignored by default, in this context
// we want to restore echo state.
continue
}
// Restore Termios
_ = unix.IoctlSetTermios(int(os.Stdin.Fd()), ioctlSetTermios, term)
if sigRecved {
switch sig {
case unix.SIGCHLD:
// SIGCHLD is expected when ssh terminates.
errChan <- nil
default:
errChan <- errors.Errorf("Received signal: %s",
unix.SignalName(sig.(unix.Signal)))
// Relay signal to default handler
_ = unix.Kill(os.Getpid(), sig.(unix.Signal))
}
} else {
errChan <- nil
return
}
}
}
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