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runfilter.cc
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runfilter.cc
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/** @file runfilter.cc
* @brief Run an external filter and capture its output in a std::string.
*
* Copyright (C) 2003,2006,2007,2009,2010,2011,2013 Olly Betts
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <config.h>
#include "runfilter.h"
#include <iostream>
#include <string>
#include <sys/types.h>
#include "safeerrno.h"
#include "safefcntl.h"
#include <cstdio>
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#ifdef HAVE_SYS_RESOURCE_H
# include <sys/resource.h>
#endif
#include "safesysselect.h"
#ifdef HAVE_SYS_SOCKET_H
# include <sys/socket.h>
#endif
#include "safesyswait.h"
#include "safeunistd.h"
#if defined HAVE_FORK && defined HAVE_SOCKETPAIR
# include <signal.h>
#endif
#include "freemem.h"
#ifdef _MSC_VER
# define popen _popen
# define pclose _pclose
#endif
using namespace std;
#if defined HAVE_FORK && defined HAVE_SOCKETPAIR
static pid_t pid_to_kill_on_signal;
#ifdef HAVE_SIGACTION
static struct sigaction old_hup_handler;
static struct sigaction old_int_handler;
static struct sigaction old_quit_handler;
static struct sigaction old_term_handler;
extern "C" {
static void
handle_signal(int signum)
{
if (pid_to_kill_on_signal) {
kill(pid_to_kill_on_signal, SIGKILL);
pid_to_kill_on_signal = 0;
}
switch (signum) {
case SIGHUP:
sigaction(signum, &old_hup_handler, NULL);
break;
case SIGINT:
sigaction(signum, &old_int_handler, NULL);
break;
case SIGQUIT:
sigaction(signum, &old_quit_handler, NULL);
break;
case SIGTERM:
sigaction(signum, &old_term_handler, NULL);
break;
default:
return;
}
raise(signum);
}
}
void
runfilter_init()
{
struct sigaction sa;
sa.sa_handler = handle_signal;
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sigaction(SIGHUP, &sa, &old_hup_handler);
sigaction(SIGINT, &sa, &old_int_handler);
sigaction(SIGQUIT, &sa, &old_quit_handler);
sigaction(SIGTERM, &sa, &old_term_handler);
}
#else
static sighandler_t old_hup_handler;
static sighandler_t old_int_handler;
static sighandler_t old_quit_handler;
static sighandler_t old_term_handler;
extern "C" {
static void
handle_signal(int signum)
{
if (pid_to_kill_on_signal) {
kill(pid_to_kill_on_signal, SIGKILL);
pid_to_kill_on_signal = 0;
}
switch (signum) {
case SIGHUP:
signal(signum, old_hup_handler);
break;
case SIGINT:
signal(signum, old_int_handler);
break;
case SIGQUIT:
signal(signum, old_quit_handler);
break;
case SIGTERM:
signal(signum, old_term_handler);
break;
default:
return;
}
raise(signum);
}
}
void
runfilter_init()
{
old_hup_handler = signal(SIGHUP, handle_signal);
old_int_handler = signal(SIGINT, handle_signal);
old_quit_handler = signal(SIGQUIT, handle_signal);
old_term_handler = signal(SIGTERM, handle_signal);
}
#endif
#else
void
runfilter_init()
{
}
#endif
string
stdout_to_string(const string &cmd)
{
string out;
#if defined HAVE_FORK && defined HAVE_SOCKETPAIR
// We want to be able to get the exit status of the child process.
signal(SIGCHLD, SIG_DFL);
int fds[2];
if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, fds) < 0)
throw ReadError();
pid_t child = fork();
if (child == 0) {
// We're the child process.
#ifdef HAVE_SETPGID
// Put the child process into its own process group, so that we can
// easily kill it and any children it in turn forks if we need to.
setpgid(0, 0);
pid_to_kill_on_signal = -child;
#else
pid_to_kill_on_signal = child;
#endif
// Close the parent's side of the socket pair.
close(fds[0]);
// Connect stdout to our side of the socket pair.
dup2(fds[1], 1);
#ifdef HAVE_SETRLIMIT
// Impose some pretty generous resource limits to prevent run-away
// filter programs from causing problems.
// Limit CPU time to 300 seconds (5 minutes).
struct rlimit cpu_limit = { 300, RLIM_INFINITY } ;
setrlimit(RLIMIT_CPU, &cpu_limit);
#if defined RLIMIT_AS || defined RLIMIT_VMEM || defined RLIMIT_DATA
// Limit process data to free physical memory.
long mem = get_free_physical_memory();
if (mem > 0) {
struct rlimit ram_limit = {
static_cast<rlim_t>(mem),
RLIM_INFINITY
};
#ifdef RLIMIT_AS
setrlimit(RLIMIT_AS, &ram_limit);
#elif defined RLIMIT_VMEM
setrlimit(RLIMIT_VMEM, &ram_limit);
#else
// Only limits the data segment rather than the total address
// space, but that's better than nothing.
setrlimit(RLIMIT_DATA, &ram_limit);
#endif
}
#endif
#endif
execl("/bin/sh", "/bin/sh", "-c", cmd.c_str(), (void*)NULL);
_exit(-1);
}
// We're the parent process.
// Close the child's side of the socket pair.
close(fds[1]);
if (child == -1) {
// fork() failed.
close(fds[0]);
throw ReadError();
}
int fd = fds[0];
fd_set readfds;
FD_ZERO(&readfds);
while (true) {
// If we wait 300 seconds (5 minutes) without getting data from the
// filter, then give up to avoid waiting forever for a filter which
// has ended up blocked waiting for something which will never happen.
struct timeval tv;
tv.tv_sec = 300;
tv.tv_usec = 0;
FD_SET(fd, &readfds);
int r = select(fd + 1, &readfds, NULL, NULL, &tv);
if (r <= 0) {
if (r < 0) {
if (errno == EINTR) {
// select() interrupted by a signal, so retry.
continue;
}
cerr << "Reading from filter failed (" << strerror(errno) << ")"
<< endl;
} else {
cerr << "Filter inactive for too long" << endl;
}
#ifdef HAVE_SETPGID
kill(-child, SIGKILL);
#else
kill(child, SIGKILL);
#endif
close(fd);
int status = 0;
while (waitpid(child, &status, 0) < 0 && errno == EINTR) { }
pid_to_kill_on_signal = 0;
throw ReadError();
}
char buf[4096];
ssize_t res = read(fd, buf, sizeof(buf));
if (res == 0) break;
if (res == -1) {
if (errno == EINTR) {
// read() interrupted by a signal, so retry.
continue;
}
close(fd);
#ifdef HAVE_SETPGID
kill(-child, SIGKILL);
#endif
int status = 0;
while (waitpid(child, &status, 0) < 0 && errno == EINTR) { }
pid_to_kill_on_signal = 0;
throw ReadError();
}
out.append(buf, res);
}
close(fd);
#ifdef HAVE_SETPGID
kill(-child, SIGKILL);
#endif
int status = 0;
while (waitpid(child, &status, 0) < 0) {
if (errno != EINTR)
throw ReadError();
}
pid_to_kill_on_signal = 0;
#else
FILE * fh = popen(cmd.c_str(), "r");
if (fh == NULL) throw ReadError();
while (!feof(fh)) {
char buf[4096];
size_t len = fread(buf, 1, 4096, fh);
if (ferror(fh)) {
(void)pclose(fh);
throw ReadError();
}
out.append(buf, len);
}
int status = pclose(fh);
#endif
if (status != 0) {
if (WIFEXITED(status) && WEXITSTATUS(status) == 127) {
throw NoSuchFilter();
}
#ifdef SIGXCPU
if (WIFSIGNALED(status) && WTERMSIG(status) == SIGXCPU) {
cerr << "Filter process consumed too much CPU time" << endl;
}
#endif
throw ReadError();
}
return out;
}