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 * Should we print (interesting|debug) messages that can happen during
61 #define DEBUG GNUNET_NO
64 * Maximum size of a GNUnet message (GNUNET_SERVER_MAX_MESSAGE_SIZE)
66 #define MAX_SIZE 65536
69 * Path to 'sysctl' binary.
71 static const char *sbin_sysctl;
74 * Path to 'iptables' binary.
76 static const char *sbin_iptables;
81 * This is in linux/include/net/ipv6.h, but not always exported...
85 struct in6_addr ifr6_addr;
86 uint32_t ifr6_prefixlen; /* __u32 in the original */
94 * Run the given command and wait for it to complete.
96 * @param file name of the binary to run
97 * @param cmd command line arguments (as given to 'execv')
98 * @return 0 on success, 1 on any error
101 fork_and_exec (const char *file,
118 /* we are the child process */
119 /* close stdin/stdout to not cause interference
120 with the helper's main protocol! */
123 (void) execv (file, cmd);
124 /* can only get here on error */
126 "exec `%s' failed: %s\n",
131 /* keep running waitpid as long as the only error we get is 'EINTR' */
132 while ( (-1 == (ret = waitpid (pid, &status, 0))) &&
137 "waitpid failed: %s\n",
141 if (! (WIFEXITED (status) && (0 == WEXITSTATUS (status))))
143 /* child process completed and returned success, we're happy */
149 * Creates a tun-interface called dev;
151 * @param dev is asumed to point to a char[IFNAMSIZ]
152 * if *dev == '\\0', uses the name supplied by the kernel;
153 * @return the fd to the tun or -1 on error
167 if (-1 == (fd = open ("/dev/net/tun", O_RDWR)))
169 fprintf (stderr, "Error opening `%s': %s\n", "/dev/net/tun",
174 if (fd >= FD_SETSIZE)
176 fprintf (stderr, "File descriptor to large: %d", fd);
181 memset (&ifr, 0, sizeof (ifr));
182 ifr.ifr_flags = IFF_TUN;
185 strncpy (ifr.ifr_name, dev, IFNAMSIZ);
187 if (-1 == ioctl (fd, TUNSETIFF, (void *) &ifr))
190 "Error with ioctl on `%s': %s\n", "/dev/net/tun",
195 strcpy (dev, ifr.ifr_name);
201 * @brief Sets the IPv6-Address given in address on the interface dev
203 * @param dev the interface to configure
204 * @param address the IPv6-Address
205 * @param prefix_len the length of the network-prefix
208 set_address6 (const char *dev, const char *address, unsigned long prefix_len)
211 struct sockaddr_in6 sa6;
213 struct in6_ifreq ifr6;
216 * parse the new address
218 memset (&sa6, 0, sizeof (struct sockaddr_in6));
219 sa6.sin6_family = AF_INET6;
220 if (1 != inet_pton (AF_INET6, address, &sa6.sin6_addr))
222 fprintf (stderr, "Failed to parse address `%s': %s\n", address,
227 if (-1 == (fd = socket (PF_INET6, SOCK_DGRAM, 0)))
229 fprintf (stderr, "Error creating socket: %s\n", strerror (errno));
233 memset (&ifr, 0, sizeof (struct ifreq));
235 * Get the index of the if
237 strncpy (ifr.ifr_name, dev, IFNAMSIZ);
238 if (-1 == ioctl (fd, SIOGIFINDEX, &ifr))
240 fprintf (stderr, "ioctl failed at %d: %s\n", __LINE__, strerror (errno));
245 memset (&ifr6, 0, sizeof (struct in6_ifreq));
246 ifr6.ifr6_addr = sa6.sin6_addr;
247 ifr6.ifr6_ifindex = ifr.ifr_ifindex;
248 ifr6.ifr6_prefixlen = prefix_len;
253 if (-1 == ioctl (fd, SIOCSIFADDR, &ifr6))
255 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
264 if (-1 == ioctl (fd, SIOCGIFFLAGS, &ifr))
266 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
273 * Add the UP and RUNNING flags
275 ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
276 if (-1 == ioctl (fd, SIOCSIFFLAGS, &ifr))
278 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
286 fprintf (stderr, "close failed: %s\n", strerror (errno));
293 * @brief Sets the IPv4-Address given in address on the interface dev
295 * @param dev the interface to configure
296 * @param address the IPv4-Address
297 * @param mask the netmask
300 set_address4 (const char *dev, const char *address, const char *mask)
303 struct sockaddr_in *addr;
306 memset (&ifr, 0, sizeof (struct ifreq));
307 addr = (struct sockaddr_in *) &(ifr.ifr_addr);
308 addr->sin_family = AF_INET;
313 if (1 != inet_pton (AF_INET, address, &addr->sin_addr.s_addr))
315 fprintf (stderr, "Failed to parse address `%s': %s\n", address,
320 if (-1 == (fd = socket (PF_INET, SOCK_DGRAM, 0)))
322 fprintf (stderr, "Error creating socket: %s\n", strerror (errno));
326 strncpy (ifr.ifr_name, dev, IFNAMSIZ);
331 if (-1 == ioctl (fd, SIOCSIFADDR, &ifr))
333 fprintf (stderr, "ioctl failed at %d: %s\n", __LINE__, strerror (errno));
341 addr = (struct sockaddr_in *) &(ifr.ifr_netmask);
342 if (1 != inet_pton (AF_INET, mask, &addr->sin_addr.s_addr))
344 fprintf (stderr, "Failed to parse address `%s': %s\n", mask,
353 if (-1 == ioctl (fd, SIOCSIFNETMASK, &ifr))
355 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
364 if (-1 == ioctl (fd, SIOCGIFFLAGS, &ifr))
366 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
373 * Add the UP and RUNNING flags
375 ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
376 if (-1 == ioctl (fd, SIOCSIFFLAGS, &ifr))
378 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
386 fprintf (stderr, "close failed: %s\n", strerror (errno));
394 * Start forwarding to and from the tunnel.
396 * @param fd_tun tunnel FD
402 * The buffer filled by reading from fd_tun
404 unsigned char buftun[MAX_SIZE];
405 ssize_t buftun_size = 0;
406 unsigned char *buftun_read = NULL;
409 * The buffer filled by reading from stdin
411 unsigned char bufin[MAX_SIZE];
412 ssize_t bufin_size = 0;
413 size_t bufin_rpos = 0;
414 unsigned char *bufin_read = NULL;
419 /* read refers to reading from fd_tun, writing to stdout */
422 /* write refers to reading from stdin, writing to fd_tun */
425 while ((1 == read_open) || (1 == write_open))
431 * We are supposed to read and the buffer is empty
432 * -> select on read from tun
434 if (read_open && (0 == buftun_size))
435 FD_SET (fd_tun, &fds_r);
438 * We are supposed to read and the buffer is not empty
439 * -> select on write to stdout
441 if (read_open && (0 != buftun_size))
445 * We are supposed to write and the buffer is empty
446 * -> select on read from stdin
448 if (write_open && (NULL == bufin_read))
452 * We are supposed to write and the buffer is not empty
453 * -> select on write to tun
455 if (write_open && (NULL != bufin_read))
456 FD_SET (fd_tun, &fds_w);
458 int r = select (fd_tun + 1, &fds_r, &fds_w, NULL, NULL);
464 fprintf (stderr, "select failed: %s\n", strerror (errno));
470 if (FD_ISSET (fd_tun, &fds_r))
473 read (fd_tun, buftun + sizeof (struct GNUNET_MessageHeader),
474 MAX_SIZE - sizeof (struct GNUNET_MessageHeader));
475 if (-1 == buftun_size)
477 fprintf (stderr, "read-error: %s\n", strerror (errno));
478 shutdown (fd_tun, SHUT_RD);
479 shutdown (1, SHUT_WR);
483 else if (0 == buftun_size)
486 fprintf (stderr, "EOF on tun\n");
488 shutdown (fd_tun, SHUT_RD);
489 shutdown (1, SHUT_WR);
495 buftun_read = buftun;
496 struct GNUNET_MessageHeader *hdr =
497 (struct GNUNET_MessageHeader *) buftun;
498 buftun_size += sizeof (struct GNUNET_MessageHeader);
499 hdr->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
500 hdr->size = htons (buftun_size);
503 else if (FD_ISSET (1, &fds_w))
505 ssize_t written = write (1, buftun_read, buftun_size);
512 fprintf (stderr, "write-error to stdout: %s\n", strerror (errno));
513 shutdown (fd_tun, SHUT_RD);
514 shutdown (1, SHUT_WR);
518 else if (0 == written)
520 fprintf (stderr, "write returned 0!?\n");
525 buftun_size -= written;
526 buftun_read += written;
530 if (FD_ISSET (0, &fds_r))
532 bufin_size = read (0, bufin + bufin_rpos, MAX_SIZE - bufin_rpos);
533 if (-1 == bufin_size)
535 fprintf (stderr, "read-error: %s\n", strerror (errno));
536 shutdown (0, SHUT_RD);
537 shutdown (fd_tun, SHUT_WR);
541 else if (0 == bufin_size)
544 fprintf (stderr, "EOF on stdin\n");
546 shutdown (0, SHUT_RD);
547 shutdown (fd_tun, SHUT_WR);
553 struct GNUNET_MessageHeader *hdr;
556 bufin_rpos += bufin_size;
557 if (bufin_rpos < sizeof (struct GNUNET_MessageHeader))
559 hdr = (struct GNUNET_MessageHeader *) bufin;
560 if (ntohs (hdr->type) != GNUNET_MESSAGE_TYPE_VPN_HELPER)
562 fprintf (stderr, "protocol violation!\n");
565 if (ntohs (hdr->size) > bufin_rpos)
567 bufin_read = bufin + sizeof (struct GNUNET_MessageHeader);
568 bufin_size = ntohs (hdr->size) - sizeof (struct GNUNET_MessageHeader);
569 bufin_rpos -= bufin_size + sizeof (struct GNUNET_MessageHeader);
572 else if (FD_ISSET (fd_tun, &fds_w))
574 ssize_t written = write (fd_tun, bufin_read, bufin_size);
578 fprintf (stderr, "write-error to tun: %s\n", strerror (errno));
579 shutdown (0, SHUT_RD);
580 shutdown (fd_tun, SHUT_WR);
584 else if (0 == written)
586 fprintf (stderr, "write returned 0!?\n");
591 bufin_size -= written;
592 bufin_read += written;
595 memmove (bufin, bufin_read, bufin_rpos);
596 bufin_read = NULL; /* start reading again */
608 * Open VPN tunnel interface.
610 * @param argc must be 6
611 * @param argv 0: binary name ("gnunet-helper-exit")
612 * 1: tunnel interface name ("gnunet-exit")
613 * 2: IPv4 "physical" interface name ("eth0"), or "%" to not do IPv4 NAT
614 * 3: IPv6 address ("::1"), or "-" to skip IPv6
615 * 4: IPv6 netmask length in bits ("64") [ignored if #4 is "-"]
616 * 5: IPv4 address ("1.2.3.4"), or "-" to skip IPv4
617 * 6: IPv4 netmask ("255.255.0.0") [ignored if #4 is "-"]
620 main (int argc, char **argv)
628 fprintf (stderr, "Fatal: must supply 6 arguments!\n");
631 if ( (0 == strcmp (argv[3], "-")) &&
632 (0 == strcmp (argv[5], "-")) )
634 fprintf (stderr, "Fatal: disabling both IPv4 and IPv6 makes no sense.\n");
637 if (0 == access ("/sbin/iptables", X_OK))
638 sbin_iptables = "/sbin/iptables";
639 else if (0 == access ("/usr/sbin/iptables", X_OK))
640 sbin_iptables = "/usr/sbin/iptables";
644 "Fatal: executable iptables not found in approved directories: %s\n",
648 if (0 == access ("/sbin/sysctl", X_OK))
649 sbin_sysctl = "/sbin/sysctl";
650 else if (0 == access ("/usr/sbin/sysctl", X_OK))
651 sbin_sysctl = "/usr/sbin/sysctl";
655 "Fatal: executable sysctl not found in approved directories: %s\n",
660 strncpy (dev, argv[1], IFNAMSIZ);
661 dev[IFNAMSIZ - 1] = '\0';
663 if (-1 == (fd_tun = init_tun (dev)))
666 "Fatal: could not initialize tun-interface `%s' with IPv6 %s/%s and IPv4 %s/%s\n",
675 if (0 != strcmp (argv[3], "-"))
678 const char *address = argv[3];
679 long prefix_len = atol (argv[4]);
681 if ((prefix_len < 1) || (prefix_len > 127))
683 fprintf (stderr, "Fatal: prefix_len out of range\n");
686 set_address6 (dev, address, prefix_len);
689 char *const sysctl_args[] =
691 "sysctl", "-w", "net.ipv6.conf.all.forwarding=1", NULL
693 if (0 != fork_and_exec (sbin_sysctl,
697 "Failed to enable IPv6 forwarding. Will continue anyway.\n");
702 if (0 != strcmp (argv[5], "-"))
705 const char *address = argv[5];
706 const char *mask = argv[6];
708 set_address4 (dev, address, mask);
711 char *const sysctl_args[] =
713 "sysctl", "-w", "net.ipv4.ip_forward=1", NULL
715 if (0 != fork_and_exec (sbin_sysctl,
719 "Failed to enable IPv4 forwarding. Will continue anyway.\n");
722 if (0 != strcmp (argv[2], "%"))
724 char *const iptables_args[] =
726 "iptables", "-t", "nat", "-A", "POSTROUTING", "-o", argv[2], "-j", "MASQUERADE", NULL
728 if (0 != fork_and_exec (sbin_iptables,
732 "Failed to enable IPv4 masquerading (NAT). Will continue anyway.\n");
737 uid_t uid = getuid ();
738 #ifdef HAVE_SETRESUID
739 if (0 != setresuid (uid, uid, uid))
741 fprintf (stderr, "Failed to setresuid: %s\n", strerror (errno));
746 if (0 != (setuid (uid) | seteuid (uid)))
748 fprintf (stderr, "Failed to setuid: %s\n", strerror (errno));
754 if (SIG_ERR == signal (SIGPIPE, SIG_IGN))
756 fprintf (stderr, "Failed to protect against SIGPIPE: %s\n",
758 /* no exit, we might as well die with SIGPIPE should it ever happen */
763 (void) close (fd_tun);
767 /* end of gnunet-helper-exit.c */