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 (void) execv (file, cmd);
114 /* can only get here on error */
116 "exec `%s' failed: %s\n",
121 /* keep running waitpid as long as the only error we get is 'EINTR' */
122 while ( (-1 == (ret = waitpid (pid, &status, 0))) &&
127 "waitpid failed: %s\n",
131 if (! (WIFEXITED (status) && (0 == WEXITSTATUS (status))))
133 /* child process completed and returned success, we're happy */
139 * Creates a tun-interface called dev;
141 * @param dev is asumed to point to a char[IFNAMSIZ]
142 * if *dev == '\\0', uses the name supplied by the kernel;
143 * @return the fd to the tun or -1 on error
157 if (-1 == (fd = open ("/dev/net/tun", O_RDWR)))
159 fprintf (stderr, "Error opening `%s': %s\n", "/dev/net/tun",
164 if (fd >= FD_SETSIZE)
166 fprintf (stderr, "File descriptor to large: %d", fd);
170 memset (&ifr, 0, sizeof (ifr));
171 ifr.ifr_flags = IFF_TUN;
174 strncpy (ifr.ifr_name, dev, IFNAMSIZ);
176 if (-1 == ioctl (fd, TUNSETIFF, (void *) &ifr))
178 fprintf (stderr, "Error with ioctl on `%s': %s\n", "/dev/net/tun",
183 strcpy (dev, ifr.ifr_name);
189 * @brief Sets the IPv6-Address given in address on the interface dev
191 * @param dev the interface to configure
192 * @param address the IPv6-Address
193 * @param prefix_len the length of the network-prefix
196 set_address6 (const char *dev, const char *address, unsigned long prefix_len)
199 struct in6_ifreq ifr6;
200 struct sockaddr_in6 sa6;
204 * parse the new address
206 memset (&sa6, 0, sizeof (struct sockaddr_in6));
207 sa6.sin6_family = AF_INET6;
208 if (1 != inet_pton (AF_INET6, address, sa6.sin6_addr.s6_addr))
210 fprintf (stderr, "Failed to parse address `%s': %s\n", address,
215 if (-1 == (fd = socket (PF_INET6, SOCK_DGRAM, 0)))
217 fprintf (stderr, "Error creating socket: %s\n", strerror (errno));
221 memset (&ifr, 0, sizeof (struct ifreq));
223 * Get the index of the if
225 strncpy (ifr.ifr_name, dev, IFNAMSIZ);
226 if (-1 == ioctl (fd, SIOGIFINDEX, &ifr))
228 fprintf (stderr, "ioctl failed at %d: %s\n", __LINE__, strerror (errno));
233 memset (&ifr6, 0, sizeof (struct in6_ifreq));
234 ifr6.ifr6_addr = sa6.sin6_addr;
235 ifr6.ifr6_ifindex = ifr.ifr_ifindex;
236 ifr6.ifr6_prefixlen = prefix_len;
241 if (-1 == ioctl (fd, SIOCSIFADDR, &ifr6))
243 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
252 if (-1 == ioctl (fd, SIOCGIFFLAGS, &ifr))
254 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
261 * Add the UP and RUNNING flags
263 ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
264 if (-1 == ioctl (fd, SIOCSIFFLAGS, &ifr))
266 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
274 fprintf (stderr, "close failed: %s\n", strerror (errno));
281 * @brief Sets the IPv4-Address given in address on the interface dev
283 * @param dev the interface to configure
284 * @param address the IPv4-Address
285 * @param mask the netmask
288 set_address4 (const char *dev, const char *address, const char *mask)
291 struct sockaddr_in *addr;
294 memset (&ifr, 0, sizeof (struct ifreq));
295 addr = (struct sockaddr_in *) &(ifr.ifr_addr);
296 addr->sin_family = AF_INET;
301 if (1 != inet_pton (AF_INET, address, &addr->sin_addr.s_addr))
303 fprintf (stderr, "Failed to parse address `%s': %s\n", address,
308 if (-1 == (fd = socket (PF_INET, SOCK_DGRAM, 0)))
310 fprintf (stderr, "Error creating socket: %s\n", strerror (errno));
314 strncpy (ifr.ifr_name, dev, IFNAMSIZ);
319 if (-1 == ioctl (fd, SIOCSIFADDR, &ifr))
321 fprintf (stderr, "ioctl failed at %d: %s\n", __LINE__, strerror (errno));
329 addr = (struct sockaddr_in *) &(ifr.ifr_netmask);
330 if (1 != inet_pton (AF_INET, mask, &addr->sin_addr.s_addr))
332 fprintf (stderr, "Failed to parse address `%s': %s\n", mask,
341 if (-1 == ioctl (fd, SIOCSIFNETMASK, &ifr))
343 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
352 if (-1 == ioctl (fd, SIOCGIFFLAGS, &ifr))
354 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
361 * Add the UP and RUNNING flags
363 ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
364 if (-1 == ioctl (fd, SIOCSIFFLAGS, &ifr))
366 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
374 fprintf (stderr, "close failed: %s\n", strerror (errno));
382 * Start forwarding to and from the tunnel.
384 * @param fd_tun tunnel FD
390 * The buffer filled by reading from fd_tun
392 unsigned char buftun[MAX_SIZE];
393 ssize_t buftun_size = 0;
394 unsigned char *buftun_read = NULL;
397 * The buffer filled by reading from stdin
399 unsigned char bufin[MAX_SIZE];
400 ssize_t bufin_size = 0;
401 size_t bufin_rpos = 0;
402 unsigned char *bufin_read = NULL;
407 /* read refers to reading from fd_tun, writing to stdout */
410 /* write refers to reading from stdin, writing to fd_tun */
413 while ((1 == read_open) || (1 == write_open))
419 * We are supposed to read and the buffer is empty
420 * -> select on read from tun
422 if (read_open && (0 == buftun_size))
423 FD_SET (fd_tun, &fds_r);
426 * We are supposed to read and the buffer is not empty
427 * -> select on write to stdout
429 if (read_open && (0 != buftun_size))
433 * We are supposed to write and the buffer is empty
434 * -> select on read from stdin
436 if (write_open && (NULL == bufin_read))
440 * We are supposed to write and the buffer is not empty
441 * -> select on write to tun
443 if (write_open && (NULL != bufin_read))
444 FD_SET (fd_tun, &fds_w);
446 int r = select (fd_tun + 1, &fds_r, &fds_w, NULL, NULL);
452 fprintf (stderr, "select failed: %s\n", strerror (errno));
458 if (FD_ISSET (fd_tun, &fds_r))
461 read (fd_tun, buftun + sizeof (struct GNUNET_MessageHeader),
462 MAX_SIZE - sizeof (struct GNUNET_MessageHeader));
463 if (-1 == buftun_size)
465 fprintf (stderr, "read-error: %s\n", strerror (errno));
466 shutdown (fd_tun, SHUT_RD);
467 shutdown (1, SHUT_WR);
471 else if (0 == buftun_size)
473 fprintf (stderr, "EOF on tun\n");
474 shutdown (fd_tun, SHUT_RD);
475 shutdown (1, SHUT_WR);
481 buftun_read = buftun;
482 struct GNUNET_MessageHeader *hdr =
483 (struct GNUNET_MessageHeader *) buftun;
484 buftun_size += sizeof (struct GNUNET_MessageHeader);
485 hdr->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
486 hdr->size = htons (buftun_size);
489 else if (FD_ISSET (1, &fds_w))
491 ssize_t written = write (1, buftun_read, buftun_size);
495 fprintf (stderr, "write-error to stdout: %s\n", strerror (errno));
496 shutdown (fd_tun, SHUT_RD);
497 shutdown (1, SHUT_WR);
501 else if (0 == written)
503 fprintf (stderr, "write returned 0!?\n");
508 buftun_size -= written;
509 buftun_read += written;
513 if (FD_ISSET (0, &fds_r))
515 bufin_size = read (0, bufin + bufin_rpos, MAX_SIZE - bufin_rpos);
516 if (-1 == bufin_size)
518 fprintf (stderr, "read-error: %s\n", strerror (errno));
519 shutdown (0, SHUT_RD);
520 shutdown (fd_tun, SHUT_WR);
524 else if (0 == bufin_size)
526 fprintf (stderr, "EOF on stdin\n");
527 shutdown (0, SHUT_RD);
528 shutdown (fd_tun, SHUT_WR);
534 struct GNUNET_MessageHeader *hdr;
537 bufin_rpos += bufin_size;
538 if (bufin_rpos < sizeof (struct GNUNET_MessageHeader))
540 hdr = (struct GNUNET_MessageHeader *) bufin;
541 if (ntohs (hdr->type) != GNUNET_MESSAGE_TYPE_VPN_HELPER)
543 fprintf (stderr, "protocol violation!\n");
546 if (ntohs (hdr->size) > bufin_rpos)
548 bufin_read = bufin + sizeof (struct GNUNET_MessageHeader);
549 bufin_size = ntohs (hdr->size) - sizeof (struct GNUNET_MessageHeader);
550 bufin_rpos -= bufin_size + sizeof (struct GNUNET_MessageHeader);
553 else if (FD_ISSET (fd_tun, &fds_w))
555 ssize_t written = write (fd_tun, bufin_read, bufin_size);
559 fprintf (stderr, "write-error to tun: %s\n", strerror (errno));
560 shutdown (0, SHUT_RD);
561 shutdown (fd_tun, SHUT_WR);
565 else if (0 == written)
567 fprintf (stderr, "write returned 0!?\n");
572 bufin_size -= written;
573 bufin_read += written;
576 memmove (bufin, bufin_read, bufin_rpos);
577 bufin_read = NULL; /* start reading again */
589 * Open VPN tunnel interface.
591 * @param argc must be 6
592 * @param argv 0: binary name ("gnunet-helper-vpn")
593 * 1: tunnel interface name ("gnunet-vpn")
594 * 2: IPv4 "physical" interface name ("eth0"), or "%" to not do IPv4 NAT
595 * 3: IPv6 address ("::1"), or "-" to skip IPv6
596 * 4: IPv6 netmask length in bits ("64") [ignored if #4 is "-"]
597 * 5: IPv4 address ("1.2.3.4"), or "-" to skip IPv4
598 * 6: IPv4 netmask ("255.255.0.0") [ignored if #4 is "-"]
601 main (int argc, char **argv)
609 fprintf (stderr, "Fatal: must supply 5 arguments!\n");
612 if ( (0 == strcmp (argv[3], "-")) &&
613 (0 == strcmp (argv[5], "-")) )
615 fprintf (stderr, "Fatal: disabling both IPv4 and IPv6 makes no sense.\n");
618 if (0 == access ("/sbin/iptables", X_OK))
619 sbin_iptables = "/sbin/iptables";
620 else if (0 == access ("/usr/sbin/iptables", X_OK))
621 sbin_iptables = "/usr/sbin/iptables";
625 "Fatal: executable iptables not found in approved directories: %s\n",
629 if (0 == access ("/sbin/sysctl", X_OK))
630 sbin_sysctl = "/sbin/sysctl";
631 else if (0 == access ("/usr/sbin/sysctl", X_OK))
632 sbin_sysctl = "/usr/sbin/sysctl";
636 "Fatal: executable sysctl not found in approved directories: %s\n",
641 strncpy (dev, argv[1], IFNAMSIZ);
642 dev[IFNAMSIZ - 1] = '\0';
644 if (-1 == (fd_tun = init_tun (dev)))
646 fprintf (stderr, "Fatal: could not initialize tun-interface\n");
650 if (0 != strcmp (argv[3], "-"))
653 const char *address = argv[3];
654 long prefix_len = atol (argv[4]);
656 if ((prefix_len < 1) || (prefix_len > 127))
658 fprintf (stderr, "Fatal: prefix_len out of range\n");
661 set_address6 (dev, address, prefix_len);
664 char *const sysctl_args[] =
666 "sysctl", "-w", "net.ipv6.conf.all.forwarding=1", NULL
668 if (0 != fork_and_exec (sbin_sysctl,
672 "Failed to enable IPv6 forwarding. Will continue anyway.\n");
677 if (0 != strcmp (argv[5], "-"))
680 const char *address = argv[5];
681 const char *mask = argv[6];
683 set_address4 (dev, address, mask);
686 char *const sysctl_args[] =
688 "sysctl", "-w", "net.ipv4.ip_forward=1", NULL
690 if (0 != fork_and_exec (sbin_sysctl,
694 "Failed to enable IPv4 forwarding. Will continue anyway.\n");
697 if (0 != strcmp (argv[2], "%"))
699 char *const iptables_args[] =
701 "iptables", "-t", "nat", "-A", "POSTROUTING", "-o", argv[2], "-j", "MASQUERADE", NULL
703 if (0 != fork_and_exec (sbin_iptables,
707 "Failed to enable IPv4 masquerading (NAT). Will continue anyway.\n");
712 uid_t uid = getuid ();
713 #ifdef HAVE_SETRESUID
714 if (0 != setresuid (uid, uid, uid))
716 fprintf (stderr, "Failed to setresuid: %s\n", strerror (errno));
721 if (0 != (setuid (uid) | seteuid (uid)))
723 fprintf (stderr, "Failed to setuid: %s\n", strerror (errno));
729 if (SIG_ERR == signal (SIGPIPE, SIG_IGN))
731 fprintf (stderr, "Failed to protect against SIGPIPE: %s\n",
733 /* no exit, we might as well die with SIGPIPE should it ever happen */
742 /* end of gnunet-helper-exit.c */