2 This file is part of GNUnet.
3 (C) 2010, 2011, 2012 Christian Grothoff
5 GNUnet is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published
7 by the Free Software Foundation; either version 3, or (at your
8 option) any later version.
10 GNUnet is distributed in the hope that it will be useful, but
11 WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with GNUnet; see the file COPYING. If not, write to the
17 Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 Boston, MA 02111-1307, USA.
22 * @file exit/gnunet-helper-exit.c
24 * @brief the helper for exit nodes. Opens a virtual
25 * network-interface, sends data received on the if to stdout, sends
26 * data received on stdin to the interface. The code also enables
27 * IPv4/IPv6 forwarding and NAT on the current system (the latter on
28 * an interface specified on the command-line); these changes to the
29 * network configuration are NOT automatically undone when the program
30 * is stopped (this is because we cannot be sure that some other
31 * application didn't enable them before or after us; also, these
32 * changes should be mostly harmless as it simply turns the system
35 * @author Philipp Tölke
36 * @author Christian Grothoff
38 * The following list of people have reviewed this code and considered
39 * it safe since the last modification (if you reviewed it, please
40 * have your name added to the list):
45 #include <linux/if_tun.h>
48 * Need 'struct GNUNET_MessageHeader'.
50 #include "gnunet_common.h"
53 * Need VPN message types.
55 #include "gnunet_protocols.h"
58 * Maximum size of a GNUnet message (GNUNET_SERVER_MAX_MESSAGE_SIZE)
60 #define MAX_SIZE 65536
63 * Path to 'sysctl' binary.
65 static const char *sbin_sysctl;
68 * Path to 'iptables' binary.
70 static const char *sbin_iptables;
75 * This is in linux/include/net/ipv6.h, but not always exported...
79 struct in6_addr ifr6_addr;
80 uint32_t ifr6_prefixlen;
81 unsigned int ifr6_ifindex;
88 * Run the given command and wait for it to complete.
90 * @param file name of the binary to run
91 * @param cmd command line arguments (as given to 'execv')
92 * @return 0 on success, 1 on any error
95 fork_and_exec (const char *file,
112 /* we are the child process */
113 /* close stdin/stdout to not cause interference
114 with the helper's main protocol! */
117 (void) execv (file, cmd);
118 /* can only get here on error */
120 "exec `%s' failed: %s\n",
125 /* keep running waitpid as long as the only error we get is 'EINTR' */
126 while ( (-1 == (ret = waitpid (pid, &status, 0))) &&
131 "waitpid failed: %s\n",
135 if (! (WIFEXITED (status) && (0 == WEXITSTATUS (status))))
137 /* child process completed and returned success, we're happy */
143 * Creates a tun-interface called dev;
145 * @param dev is asumed to point to a char[IFNAMSIZ]
146 * if *dev == '\\0', uses the name supplied by the kernel;
147 * @return the fd to the tun or -1 on error
161 if (-1 == (fd = open ("/dev/net/tun", O_RDWR)))
163 fprintf (stderr, "Error opening `%s': %s\n", "/dev/net/tun",
168 if (fd >= FD_SETSIZE)
170 fprintf (stderr, "File descriptor to large: %d", fd);
175 memset (&ifr, 0, sizeof (ifr));
176 ifr.ifr_flags = IFF_TUN;
179 strncpy (ifr.ifr_name, dev, IFNAMSIZ);
181 if (-1 == ioctl (fd, TUNSETIFF, (void *) &ifr))
184 "Error with ioctl on `%s': %s\n", "/dev/net/tun",
189 strcpy (dev, ifr.ifr_name);
195 * @brief Sets the IPv6-Address given in address on the interface dev
197 * @param dev the interface to configure
198 * @param address the IPv6-Address
199 * @param prefix_len the length of the network-prefix
202 set_address6 (const char *dev, const char *address, unsigned long prefix_len)
205 struct in6_ifreq ifr6;
206 struct sockaddr_in6 sa6;
210 * parse the new address
212 memset (&sa6, 0, sizeof (struct sockaddr_in6));
213 sa6.sin6_family = AF_INET6;
214 if (1 != inet_pton (AF_INET6, address, sa6.sin6_addr.s6_addr))
216 fprintf (stderr, "Failed to parse address `%s': %s\n", address,
221 if (-1 == (fd = socket (PF_INET6, SOCK_DGRAM, 0)))
223 fprintf (stderr, "Error creating socket: %s\n", strerror (errno));
227 memset (&ifr, 0, sizeof (struct ifreq));
229 * Get the index of the if
231 strncpy (ifr.ifr_name, dev, IFNAMSIZ);
232 if (-1 == ioctl (fd, SIOGIFINDEX, &ifr))
234 fprintf (stderr, "ioctl failed at %d: %s\n", __LINE__, strerror (errno));
239 memset (&ifr6, 0, sizeof (struct in6_ifreq));
240 ifr6.ifr6_addr = sa6.sin6_addr;
241 ifr6.ifr6_ifindex = ifr.ifr_ifindex;
242 ifr6.ifr6_prefixlen = prefix_len;
247 if (-1 == ioctl (fd, SIOCSIFADDR, &ifr6))
249 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
258 if (-1 == ioctl (fd, SIOCGIFFLAGS, &ifr))
260 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
267 * Add the UP and RUNNING flags
269 ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
270 if (-1 == ioctl (fd, SIOCSIFFLAGS, &ifr))
272 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
280 fprintf (stderr, "close failed: %s\n", strerror (errno));
287 * @brief Sets the IPv4-Address given in address on the interface dev
289 * @param dev the interface to configure
290 * @param address the IPv4-Address
291 * @param mask the netmask
294 set_address4 (const char *dev, const char *address, const char *mask)
297 struct sockaddr_in *addr;
300 memset (&ifr, 0, sizeof (struct ifreq));
301 addr = (struct sockaddr_in *) &(ifr.ifr_addr);
302 addr->sin_family = AF_INET;
307 if (1 != inet_pton (AF_INET, address, &addr->sin_addr.s_addr))
309 fprintf (stderr, "Failed to parse address `%s': %s\n", address,
314 if (-1 == (fd = socket (PF_INET, SOCK_DGRAM, 0)))
316 fprintf (stderr, "Error creating socket: %s\n", strerror (errno));
320 strncpy (ifr.ifr_name, dev, IFNAMSIZ);
325 if (-1 == ioctl (fd, SIOCSIFADDR, &ifr))
327 fprintf (stderr, "ioctl failed at %d: %s\n", __LINE__, strerror (errno));
335 addr = (struct sockaddr_in *) &(ifr.ifr_netmask);
336 if (1 != inet_pton (AF_INET, mask, &addr->sin_addr.s_addr))
338 fprintf (stderr, "Failed to parse address `%s': %s\n", mask,
347 if (-1 == ioctl (fd, SIOCSIFNETMASK, &ifr))
349 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
358 if (-1 == ioctl (fd, SIOCGIFFLAGS, &ifr))
360 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
367 * Add the UP and RUNNING flags
369 ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
370 if (-1 == ioctl (fd, SIOCSIFFLAGS, &ifr))
372 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
380 fprintf (stderr, "close failed: %s\n", strerror (errno));
388 * Start forwarding to and from the tunnel.
390 * @param fd_tun tunnel FD
396 * The buffer filled by reading from fd_tun
398 unsigned char buftun[MAX_SIZE];
399 ssize_t buftun_size = 0;
400 unsigned char *buftun_read = NULL;
403 * The buffer filled by reading from stdin
405 unsigned char bufin[MAX_SIZE];
406 ssize_t bufin_size = 0;
407 size_t bufin_rpos = 0;
408 unsigned char *bufin_read = NULL;
413 /* read refers to reading from fd_tun, writing to stdout */
416 /* write refers to reading from stdin, writing to fd_tun */
419 while ((1 == read_open) || (1 == write_open))
425 * We are supposed to read and the buffer is empty
426 * -> select on read from tun
428 if (read_open && (0 == buftun_size))
429 FD_SET (fd_tun, &fds_r);
432 * We are supposed to read and the buffer is not empty
433 * -> select on write to stdout
435 if (read_open && (0 != buftun_size))
439 * We are supposed to write and the buffer is empty
440 * -> select on read from stdin
442 if (write_open && (NULL == bufin_read))
446 * We are supposed to write and the buffer is not empty
447 * -> select on write to tun
449 if (write_open && (NULL != bufin_read))
450 FD_SET (fd_tun, &fds_w);
452 int r = select (fd_tun + 1, &fds_r, &fds_w, NULL, NULL);
458 fprintf (stderr, "select failed: %s\n", strerror (errno));
464 if (FD_ISSET (fd_tun, &fds_r))
467 read (fd_tun, buftun + sizeof (struct GNUNET_MessageHeader),
468 MAX_SIZE - sizeof (struct GNUNET_MessageHeader));
469 if (-1 == buftun_size)
471 fprintf (stderr, "read-error: %s\n", strerror (errno));
472 shutdown (fd_tun, SHUT_RD);
473 shutdown (1, SHUT_WR);
477 else if (0 == buftun_size)
479 fprintf (stderr, "EOF on tun\n");
480 shutdown (fd_tun, SHUT_RD);
481 shutdown (1, SHUT_WR);
487 buftun_read = buftun;
488 struct GNUNET_MessageHeader *hdr =
489 (struct GNUNET_MessageHeader *) buftun;
490 buftun_size += sizeof (struct GNUNET_MessageHeader);
491 hdr->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
492 hdr->size = htons (buftun_size);
495 else if (FD_ISSET (1, &fds_w))
497 ssize_t written = write (1, buftun_read, buftun_size);
501 fprintf (stderr, "write-error to stdout: %s\n", strerror (errno));
502 shutdown (fd_tun, SHUT_RD);
503 shutdown (1, SHUT_WR);
507 else if (0 == written)
509 fprintf (stderr, "write returned 0!?\n");
514 buftun_size -= written;
515 buftun_read += written;
519 if (FD_ISSET (0, &fds_r))
521 bufin_size = read (0, bufin + bufin_rpos, MAX_SIZE - bufin_rpos);
522 if (-1 == bufin_size)
524 fprintf (stderr, "read-error: %s\n", strerror (errno));
525 shutdown (0, SHUT_RD);
526 shutdown (fd_tun, SHUT_WR);
530 else if (0 == bufin_size)
532 fprintf (stderr, "EOF on stdin\n");
533 shutdown (0, SHUT_RD);
534 shutdown (fd_tun, SHUT_WR);
540 struct GNUNET_MessageHeader *hdr;
543 bufin_rpos += bufin_size;
544 if (bufin_rpos < sizeof (struct GNUNET_MessageHeader))
546 hdr = (struct GNUNET_MessageHeader *) bufin;
547 if (ntohs (hdr->type) != GNUNET_MESSAGE_TYPE_VPN_HELPER)
549 fprintf (stderr, "protocol violation!\n");
552 if (ntohs (hdr->size) > bufin_rpos)
554 bufin_read = bufin + sizeof (struct GNUNET_MessageHeader);
555 bufin_size = ntohs (hdr->size) - sizeof (struct GNUNET_MessageHeader);
556 bufin_rpos -= bufin_size + sizeof (struct GNUNET_MessageHeader);
559 else if (FD_ISSET (fd_tun, &fds_w))
561 ssize_t written = write (fd_tun, bufin_read, bufin_size);
565 fprintf (stderr, "write-error to tun: %s\n", strerror (errno));
566 shutdown (0, SHUT_RD);
567 shutdown (fd_tun, SHUT_WR);
571 else if (0 == written)
573 fprintf (stderr, "write returned 0!?\n");
578 bufin_size -= written;
579 bufin_read += written;
582 memmove (bufin, bufin_read, bufin_rpos);
583 bufin_read = NULL; /* start reading again */
595 * Open VPN tunnel interface.
597 * @param argc must be 6
598 * @param argv 0: binary name ("gnunet-helper-exit")
599 * 1: tunnel interface name ("gnunet-exit")
600 * 2: IPv4 "physical" interface name ("eth0"), or "%" to not do IPv4 NAT
601 * 3: IPv6 address ("::1"), or "-" to skip IPv6
602 * 4: IPv6 netmask length in bits ("64") [ignored if #4 is "-"]
603 * 5: IPv4 address ("1.2.3.4"), or "-" to skip IPv4
604 * 6: IPv4 netmask ("255.255.0.0") [ignored if #4 is "-"]
607 main (int argc, char **argv)
615 fprintf (stderr, "Fatal: must supply 6 arguments!\n");
618 if ( (0 == strcmp (argv[3], "-")) &&
619 (0 == strcmp (argv[5], "-")) )
621 fprintf (stderr, "Fatal: disabling both IPv4 and IPv6 makes no sense.\n");
624 if (0 == access ("/sbin/iptables", X_OK))
625 sbin_iptables = "/sbin/iptables";
626 else if (0 == access ("/usr/sbin/iptables", X_OK))
627 sbin_iptables = "/usr/sbin/iptables";
631 "Fatal: executable iptables not found in approved directories: %s\n",
635 if (0 == access ("/sbin/sysctl", X_OK))
636 sbin_sysctl = "/sbin/sysctl";
637 else if (0 == access ("/usr/sbin/sysctl", X_OK))
638 sbin_sysctl = "/usr/sbin/sysctl";
642 "Fatal: executable sysctl not found in approved directories: %s\n",
647 strncpy (dev, argv[1], IFNAMSIZ);
648 dev[IFNAMSIZ - 1] = '\0';
650 if (-1 == (fd_tun = init_tun (dev)))
652 fprintf (stderr, "Fatal: could not initialize tun-interface\n");
656 if (0 != strcmp (argv[3], "-"))
659 const char *address = argv[3];
660 long prefix_len = atol (argv[4]);
662 if ((prefix_len < 1) || (prefix_len > 127))
664 fprintf (stderr, "Fatal: prefix_len out of range\n");
667 set_address6 (dev, address, prefix_len);
670 char *const sysctl_args[] =
672 "sysctl", "-w", "net.ipv6.conf.all.forwarding=1", NULL
674 if (0 != fork_and_exec (sbin_sysctl,
678 "Failed to enable IPv6 forwarding. Will continue anyway.\n");
683 if (0 != strcmp (argv[5], "-"))
686 const char *address = argv[5];
687 const char *mask = argv[6];
689 set_address4 (dev, address, mask);
692 char *const sysctl_args[] =
694 "sysctl", "-w", "net.ipv4.ip_forward=1", NULL
696 if (0 != fork_and_exec (sbin_sysctl,
700 "Failed to enable IPv4 forwarding. Will continue anyway.\n");
703 if (0 != strcmp (argv[2], "%"))
705 char *const iptables_args[] =
707 "iptables", "-t", "nat", "-A", "POSTROUTING", "-o", argv[2], "-j", "MASQUERADE", NULL
709 if (0 != fork_and_exec (sbin_iptables,
713 "Failed to enable IPv4 masquerading (NAT). Will continue anyway.\n");
718 uid_t uid = getuid ();
719 #ifdef HAVE_SETRESUID
720 if (0 != setresuid (uid, uid, uid))
722 fprintf (stderr, "Failed to setresuid: %s\n", strerror (errno));
727 if (0 != (setuid (uid) | seteuid (uid)))
729 fprintf (stderr, "Failed to setuid: %s\n", strerror (errno));
735 if (SIG_ERR == signal (SIGPIPE, SIG_IGN))
737 fprintf (stderr, "Failed to protect against SIGPIPE: %s\n",
739 /* no exit, we might as well die with SIGPIPE should it ever happen */
748 /* end of gnunet-helper-exit.c */