From cb962617311f6258e7213cecc0f64d211479f9e5 Mon Sep 17 00:00:00 2001 From: Brandon Wiley Date: Thu, 31 Mar 2016 12:46:39 -0500 Subject: Move termmon code from main into its own package --- common/termmon/termmon.go | 136 ++++++++++++++++++++++++++++++++++++++++ common/termmon/termmon_linux.go | 49 +++++++++++++++ 2 files changed, 185 insertions(+) create mode 100644 common/termmon/termmon.go create mode 100644 common/termmon/termmon_linux.go (limited to 'common') diff --git a/common/termmon/termmon.go b/common/termmon/termmon.go new file mode 100644 index 0000000..0968817 --- /dev/null +++ b/common/termmon/termmon.go @@ -0,0 +1,136 @@ +/* + * Copyright (c) 2015, Yawning Angel + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * * Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +package termmon + +import ( + "io" + "io/ioutil" + "os" + "os/signal" + "runtime" + "syscall" + "time" + + "github.com/OperatorFoundation/obfs4/common/log" + "github.com/OperatorFoundation/obfs4/common/pt_extras" +) + +var TermMonitorOSInit func(*TermMonitor) error + +type TermMonitor struct { + sigChan chan os.Signal + handlerChan chan int + numHandlers int +} + +func (m *TermMonitor) OnHandlerStart() { + m.handlerChan <- 1 +} + +func (m *TermMonitor) OnHandlerFinish() { + m.handlerChan <- -1 +} + +func (m *TermMonitor) Wait(termOnNoHandlers bool) os.Signal { + // Block until a signal has been received, or (optionally) the + // number of pending handlers has hit 0. In the case of the + // latter, treat it as if a SIGTERM has been received. + for { + select { + case n := <-m.handlerChan: + m.numHandlers += n + case sig := <-m.sigChan: + return sig + } + if termOnNoHandlers && m.numHandlers == 0 { + return syscall.SIGTERM + } + } +} + +func (m *TermMonitor) termOnStdinClose() { + _, err := io.Copy(ioutil.Discard, os.Stdin) + + // io.Copy() will return a nil on EOF, since reaching EOF is + // expected behavior. No matter what, if this unblocks, assume + // that stdin is closed, and treat that as having received a + // SIGTERM. + log.Noticef("Stdin is closed or unreadable: %v", err) + m.sigChan <- syscall.SIGTERM +} + +func (m *TermMonitor) termOnPPIDChange(ppid int) { + // Under most if not all U*IX systems, the parent PID will change + // to that of init once the parent dies. There are several notable + // exceptions (Slowlaris/Android), but the parent PID changes + // under those platforms as well. + // + // Naturally we lose if the parent has died by the time when the + // Getppid() call was issued in our parent, but, this is better + // than nothing. + const ppidPollInterval = 1 * time.Second + for ppid == os.Getppid() { + time.Sleep(ppidPollInterval) + } + + // Treat the parent PID changing as the same as having received + // a SIGTERM. + log.Noticef("Parent pid changed: %d (was %d)", os.Getppid(), ppid) + m.sigChan <- syscall.SIGTERM +} + +func NewTermMonitor() (m *TermMonitor) { + ppid := os.Getppid() + m = new(TermMonitor) + m.sigChan = make(chan os.Signal) + m.handlerChan = make(chan int) + signal.Notify(m.sigChan, syscall.SIGINT, syscall.SIGTERM) + + // If tor supports feature #15435, we can use Stdin being closed as an + // indication that tor has died, or wants the PT to shutdown for any + // reason. + if pt_extras.PtShouldExitOnStdinClose() { + go m.termOnStdinClose() + } else { + // Instead of feature #15435, use various kludges and hacks: + // * Linux - Platform specific code that should always work. + // * Other U*IX - Somewhat generic code, that works unless the + // parent dies before the monitor is initialized. + if TermMonitorOSInit != nil { + // Errors here are non-fatal, since it might still be + // possible to fall back to a generic implementation. + if err := TermMonitorOSInit(m); err == nil { + return + } + } + if runtime.GOOS != "windows" { + go m.termOnPPIDChange(ppid) + } + } + return +} diff --git a/common/termmon/termmon_linux.go b/common/termmon/termmon_linux.go new file mode 100644 index 0000000..5540562 --- /dev/null +++ b/common/termmon/termmon_linux.go @@ -0,0 +1,49 @@ +/* + * Copyright (c) 2015, Yawning Angel + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * * Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +package main + +import ( + "fmt" + "syscall" +) + +func TermMonitorInitLinux(m *TermMonitor) error { + // Use prctl() to have the kernel deliver a SIGTERM if the parent + // process dies. This beats anything else that can be done before + // #15435 is implemented. + _, _, errno := syscall.Syscall(syscall.SYS_PRCTL, syscall.PR_SET_PDEATHSIG, uintptr(syscall.SIGTERM), 0) + if errno != 0 { + var err error = errno + return fmt.Errorf("prctl(PR_SET_PDEATHSIG, SIGTERM) returned: %s", err) + } + return nil +} + +func init() { + TermMonitorOSInit = TermMonitorInitLinux +} -- cgit v1.2.3