main: replace paniclog with logger(1)

Instead of redirecting stdout and stderr to /tmp/gocryptfs_paniclog,
where it is hard to find, redirect them to a newly spawned logger(1)
instance that forwards the messages to syslog.

See https://github.com/rfjakob/gocryptfs/issues/109 for an example
where the paniclog was lost due to a reboot.

Also, instead of closing stdin, redirect it to /dev/null, like most
daemons seem to do.
This commit is contained in:
Jakob Unterwurzacher 2017-05-24 19:57:45 +02:00
parent e827763f2e
commit 70c16fde4c

View File

@ -2,7 +2,7 @@ package main
import (
"encoding/json"
"io/ioutil"
"fmt"
"log/syslog"
"net"
"os"
@ -107,7 +107,6 @@ func doMount(args *argContainer) int {
// Initialize FUSE server
srv := initFuseFrontend(masterkey, args, confFile)
tlog.Info.Println(tlog.ColorGreen + "Filesystem mounted and ready." + tlog.ColorReset)
var paniclog *os.File
// We have been forked into the background, as evidenced by the set
// "notifypid".
if args.notifypid > 0 {
@ -115,38 +114,13 @@ func doMount(args *argContainer) int {
os.Chdir("/")
// Switch to syslog
if !args.nosyslog {
paniclog, err = ioutil.TempFile("", "gocryptfs_paniclog.")
if err != nil {
tlog.Warn.Printf("Failed to create paniclog: %v."+
" Carrying on, but fatal errors will not be logged.", err)
}
// Switch all of our logs and the generic logger to syslog
tlog.Info.SwitchToSyslog(syslog.LOG_USER | syslog.LOG_INFO)
tlog.Debug.SwitchToSyslog(syslog.LOG_USER | syslog.LOG_DEBUG)
tlog.Warn.SwitchToSyslog(syslog.LOG_USER | syslog.LOG_WARNING)
tlog.SwitchLoggerToSyslog(syslog.LOG_USER | syslog.LOG_WARNING)
// Daemons should close all fds (and we don't want to get killed by
// SIGPIPE if any of those get closed on the other end)
os.Stdin.Close()
// Redirect stdout and stderr to /tmp/gocryptfs_paniclog.NNNNNN
// instead of closing them so users have a chance to get the
// backtrace on a panic.
// https://github.com/golang/go/issues/325#issuecomment-66049178
if paniclog != nil {
err = syscall.Dup2(int(paniclog.Fd()), 1)
if err != nil {
tlog.Warn.Printf("paniclog stdout dup error: %v\n", err)
}
syscall.Dup2(int(paniclog.Fd()), 2)
if err != nil {
tlog.Warn.Printf("paniclog stderr dup error: %v\n", err)
}
// No need for the extra FD anymore, we have copies in Stdout and Stderr
err = paniclog.Close()
if err != nil {
tlog.Warn.Printf("paniclog close error: %v\n", err)
}
}
// Daemons should redirect stdin, stdout and stderr
redirectStdFds()
}
// Disconnect from the controlling terminal by creating a new session.
// This prevents us from getting SIGINT when the user presses Ctrl-C
@ -167,23 +141,50 @@ func doMount(args *argContainer) int {
handleSigint(srv, args.mountpoint)
// Jump into server loop. Returns when it gets an umount request from the kernel.
srv.Serve()
// Delete empty paniclogs
if paniclog != nil {
// The paniclog FD is saved in Stdout and Stderr
fi, err := os.Stderr.Stat()
if err != nil {
tlog.Warn.Printf("paniclog fstat error: %v", err)
} else if fi.Size() > 0 {
tlog.Warn.Printf("paniclog at %q is not empty (size %d). Not deleting it.",
paniclog.Name(), fi.Size())
return exitcodes.PanicLogNotEmpty
} else {
syscall.Unlink(paniclog.Name())
}
}
return 0
}
// redirectStdFds redirects stderr and stdout to syslog; stdin to /dev/null
func redirectStdFds() {
// stderr and stdout
pr, pw, err := os.Pipe()
if err != nil {
tlog.Warn.Printf("redirectStdFds: could not create pipe: %v\n", err)
return
}
tag := fmt.Sprintf("gocryptfs-%d-logger", os.Getpid())
cmd := exec.Command("logger", "-t", tag)
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
cmd.Stdin = pr
err = cmd.Start()
if err != nil {
tlog.Warn.Printf("redirectStdFds: could not start logger: %v\n", err)
}
pr.Close()
err = syscall.Dup2(int(pw.Fd()), 1)
if err != nil {
tlog.Warn.Printf("redirectStdFds: stdout dup error: %v\n", err)
}
syscall.Dup2(int(pw.Fd()), 2)
if err != nil {
tlog.Warn.Printf("redirectStdFds: stderr dup error: %v\n", err)
}
pw.Close()
// stdin
nullFd, err := os.Open("/dev/null")
if err != nil {
tlog.Warn.Printf("redirectStdFds: could not open /dev/null: %v\n", err)
return
}
err = syscall.Dup2(int(nullFd.Fd()), 0)
if err != nil {
tlog.Warn.Printf("redirectStdFds: stdin dup error: %v\n", err)
}
nullFd.Close()
}
// setOpenFileLimit tries to increase the open file limit to 4096 (the default hard
// limit on Linux).
func setOpenFileLimit() {