2 This file is part of GNUnet.
3 Copyright (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., 51 Franklin Street, Fifth Floor,
18 Boston, MA 02110-1301, USA.
22 * @file dns/gnunet-helper-dns.c
23 * @brief helper to install firewall rules to hijack all DNS traffic
24 * and send it to our virtual interface (except for DNS traffic
25 * that originates on the specified port). We then
26 * allow interacting with our virtual interface via stdin/stdout.
27 * @author Philipp Tölke
28 * @author Christian Grothoff
30 * This program alters the Linux firewall rules so that DNS traffic
31 * that ordinarily exits the system can be intercepted and managed by
32 * a virtual interface. In order to achieve this, DNS traffic is
33 * marked with the DNS_MARK given in below and re-routed to a custom
34 * table with the DNS_TABLE ID given below. Systems and
35 * administrators must take care to not cause conflicts with these
36 * values (it was deemed safest to hardcode them as passing these
37 * values as arguments might permit messing with arbitrary firewall
38 * rules, which would be dangerous). Traffic coming from the same
39 * group ID as the effective group ID that this process is running
40 * as is not intercepted.
42 * The code first sets up the virtual interface, then begins to
43 * redirect the DNS traffic to it, and then on errors or SIGTERM shuts
44 * down the virtual interface and removes the rules for the traffic
48 * Note that having this binary SUID is only partially safe: it will
49 * allow redirecting (and intercepting / mangling) of all DNS traffic
50 * originating from this system by any user who is able to run it.
51 * Furthermore, this code will make it trivial to DoS all DNS traffic
52 * originating from the current system, simply by sending it to
53 * nowhere (redirect stdout to /dev/null).
55 * Naturally, neither of these problems can be helped as this is the
56 * fundamental purpose of the binary. Certifying that this code is
57 * "safe" thus only means that it doesn't allow anything else (such
58 * as local priv. escalation, etc.).
60 * The following list of people have reviewed this code and considered
61 * it safe (within specifications) since the last modification (if you
62 * reviewed it, please have your name added to the list):
64 * - Christian Grothoff
68 #include <linux/if_tun.h>
71 * Need 'struct GNUNET_MessageHeader'.
73 #include "gnunet_crypto_lib.h"
74 #include "gnunet_common.h"
77 * Need DNS message types.
79 #include "gnunet_protocols.h"
82 * Maximum size of a GNUnet message (GNUNET_SERVER_MAX_MESSAGE_SIZE)
84 #define MAX_SIZE 65536
88 * This is in linux/include/net/ipv6.h, but not always exported...
92 struct in6_addr ifr6_addr;
93 uint32_t ifr6_prefixlen;
94 unsigned int ifr6_ifindex;
99 * Name and full path of IPTABLES binary.
101 static const char *sbin_iptables;
104 * Name and full path of IPTABLES binary.
106 static const char *sbin_ip6tables;
109 * Name and full path of sysctl binary
111 static const char *sbin_sysctl;
114 * Name and full path of IPTABLES binary.
116 static const char *sbin_ip;
119 * Port for DNS traffic.
121 #define DNS_PORT "53"
124 * Marker we set for our hijacked DNS traffic. We use GNUnet's
125 * port (2086) plus the DNS port (53) in HEX to make a 32-bit mark
126 * (which is hopefully long enough to not collide); so
127 * 0x08260035 = 136708149 (hopefully unique enough...).
129 #define DNS_MARK "136708149"
132 * Table we use for our DNS rules. 0-255 is the range and
133 * 0, 253, 254 and 255 are already reserved. As this is about
134 * DNS and as "53" is likely (fingers crossed!) high enough to
135 * not usually conflict with a normal user's setup, we use 53
136 * to give a hint that this has something to do with DNS.
138 #define DNS_TABLE "53"
142 * Control pipe for shutdown via signal. [0] is the read end,
143 * [1] is the write end.
149 * Signal handler called to initiate "nice" shutdown. Signals select
150 * loop via non-bocking pipe 'cpipe'.
152 * @param signal signal number of the signal (not used)
155 signal_handler (int signal)
157 /* ignore return value, as the signal handler could theoretically
158 be called many times before the shutdown can actually happen */
159 (void) write (cpipe[1], "K", 1);
164 * Open '/dev/null' and make the result the given
167 * @param target_fd desired FD to point to /dev/null
168 * @param flags open flags (O_RDONLY, O_WRONLY)
171 open_dev_null (int target_fd,
176 fd = open ("/dev/null", flags);
181 if (-1 == dup2 (fd, target_fd))
191 * Run the given command and wait for it to complete.
193 * @param file name of the binary to run
194 * @param cmd command line arguments (as given to 'execv')
195 * @return 0 on success, 1 on any error
198 fork_and_exec (const char *file,
215 /* we are the child process */
216 /* close stdin/stdout to not cause interference
217 with the helper's main protocol! */
219 open_dev_null (0, O_RDONLY);
221 open_dev_null (1, O_WRONLY);
222 (void) execv (file, cmd);
223 /* can only get here on error */
225 "exec `%s' failed: %s\n",
230 /* keep running waitpid as long as the only error we get is 'EINTR' */
231 while ( (-1 == (ret = waitpid (pid, &status, 0))) &&
236 "waitpid failed: %s\n",
240 if (! (WIFEXITED (status) && (0 == WEXITSTATUS (status))))
242 /* child process completed and returned success, we're happy */
248 * Creates a tun-interface called @a dev;
250 * @param dev is asumed to point to a char[IFNAMSIZ]
251 * if *dev == '\\0', uses the name supplied by the kernel;
252 * @return the fd to the tun or -1 on error
266 if (-1 == (fd = open ("/dev/net/tun", O_RDWR)))
268 fprintf (stderr, "Error opening `%s': %s\n", "/dev/net/tun",
273 if (fd >= FD_SETSIZE)
275 fprintf (stderr, "File descriptor to large: %d", fd);
280 memset (&ifr, 0, sizeof (ifr));
281 ifr.ifr_flags = IFF_TUN;
284 strncpy (ifr.ifr_name, dev, IFNAMSIZ);
286 if (-1 == ioctl (fd, TUNSETIFF, (void *) &ifr))
288 fprintf (stderr, "Error with ioctl on `%s': %s\n", "/dev/net/tun",
293 strcpy (dev, ifr.ifr_name);
299 * @brief Sets the IPv6-Address given in @a address on the interface @a dev
301 * @param dev the interface to configure
302 * @param address the IPv6-Address
303 * @param prefix_len the length of the network-prefix
306 set_address6 (const char *dev, const char *address, unsigned long prefix_len)
309 struct in6_ifreq ifr6;
310 struct sockaddr_in6 sa6;
314 * parse the new address
316 memset (&sa6, 0, sizeof (struct sockaddr_in6));
317 sa6.sin6_family = AF_INET6;
318 if (1 != inet_pton (AF_INET6, address, sa6.sin6_addr.s6_addr))
321 "Failed to parse IPv6 address `%s': %s\n",
327 if (-1 == (fd = socket (PF_INET6, SOCK_DGRAM, 0)))
330 "Error creating IPv6 socket: %s (ignored)\n",
332 /* ignore error, maybe only IPv4 works on this system! */
336 memset (&ifr, 0, sizeof (struct ifreq));
338 * Get the index of the if
340 strncpy (ifr.ifr_name, dev, IFNAMSIZ);
341 if (-1 == ioctl (fd, SIOGIFINDEX, &ifr))
343 fprintf (stderr, "ioctl failed at %d: %s\n", __LINE__, strerror (errno));
348 memset (&ifr6, 0, sizeof (struct in6_ifreq));
349 ifr6.ifr6_addr = sa6.sin6_addr;
350 ifr6.ifr6_ifindex = ifr.ifr_ifindex;
351 ifr6.ifr6_prefixlen = prefix_len;
356 if (-1 == ioctl (fd, SIOCSIFADDR, &ifr6))
358 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
367 if (-1 == ioctl (fd, SIOCGIFFLAGS, &ifr))
369 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
376 * Add the UP and RUNNING flags
378 ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
379 if (-1 == ioctl (fd, SIOCSIFFLAGS, &ifr))
381 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
389 fprintf (stderr, "close failed: %s\n", strerror (errno));
396 * @brief Sets the IPv4-Address given in @a address on the interface @a dev
398 * @param dev the interface to configure
399 * @param address the IPv4-Address
400 * @param mask the netmask
403 set_address4 (const char *dev, const char *address, const char *mask)
406 struct sockaddr_in *addr;
409 memset (&ifr, 0, sizeof (struct ifreq));
410 addr = (struct sockaddr_in *) &(ifr.ifr_addr);
411 addr->sin_family = AF_INET;
416 if (1 != inet_pton (AF_INET, address, &addr->sin_addr.s_addr))
419 "Failed to parse IPv4 address `%s': %s\n",
425 if (-1 == (fd = socket (PF_INET, SOCK_DGRAM, 0)))
428 "Error creating IPv4 socket: %s\n",
433 strncpy (ifr.ifr_name, dev, IFNAMSIZ);
438 if (-1 == ioctl (fd, SIOCSIFADDR, &ifr))
440 fprintf (stderr, "ioctl failed at %d: %s\n", __LINE__, strerror (errno));
448 addr = (struct sockaddr_in *) &(ifr.ifr_netmask);
449 if (1 != inet_pton (AF_INET, mask, &addr->sin_addr.s_addr))
451 fprintf (stderr, "Failed to parse address `%s': %s\n", mask,
460 if (-1 == ioctl (fd, SIOCSIFNETMASK, &ifr))
462 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
471 if (-1 == ioctl (fd, SIOCGIFFLAGS, &ifr))
473 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
480 * Add the UP and RUNNING flags
482 ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
483 if (-1 == ioctl (fd, SIOCSIFFLAGS, &ifr))
485 fprintf (stderr, "ioctl failed at line %d: %s\n", __LINE__,
493 fprintf (stderr, "close failed: %s\n", strerror (errno));
501 * Start forwarding to and from the tunnel. This function runs with
502 * "reduced" priviledges (saved UID is still 0, but effective UID is
505 * @param fd_tun tunnel FD
511 * The buffer filled by reading from fd_tun
513 unsigned char buftun[MAX_SIZE];
514 ssize_t buftun_size = 0;
515 unsigned char *buftun_read = NULL;
518 * The buffer filled by reading from stdin
520 unsigned char bufin[MAX_SIZE];
521 ssize_t bufin_size = 0;
522 size_t bufin_rpos = 0;
523 unsigned char *bufin_read = NULL;
534 * We are supposed to read and the buffer is empty
535 * -> select on read from tun
537 if (0 == buftun_size)
538 FD_SET (fd_tun, &fds_r);
541 * We are supposed to read and the buffer is not empty
542 * -> select on write to stdout
548 * We are supposed to write and the buffer is empty
549 * -> select on read from stdin
551 if (NULL == bufin_read)
555 * We are supposed to write and the buffer is not empty
556 * -> select on write to tun
558 if (NULL != bufin_read)
559 FD_SET (fd_tun, &fds_w);
561 FD_SET (cpipe[0], &fds_r);
562 max = (fd_tun > cpipe[0]) ? fd_tun : cpipe[0];
564 int r = select (max + 1, &fds_r, &fds_w, NULL, NULL);
570 fprintf (stderr, "select failed: %s\n", strerror (errno));
576 if (FD_ISSET (cpipe[0], &fds_r))
577 return; /* aborted by signal */
579 if (FD_ISSET (fd_tun, &fds_r))
582 read (fd_tun, buftun + sizeof (struct GNUNET_MessageHeader),
583 MAX_SIZE - sizeof (struct GNUNET_MessageHeader));
584 if (-1 == buftun_size)
586 if ( (errno == EINTR) ||
592 fprintf (stderr, "read-error: %s\n", strerror (errno));
595 if (0 == buftun_size)
597 fprintf (stderr, "EOF on tun\n");
600 buftun_read = buftun;
602 struct GNUNET_MessageHeader *hdr =
603 (struct GNUNET_MessageHeader *) buftun;
604 buftun_size += sizeof (struct GNUNET_MessageHeader);
605 hdr->type = htons (GNUNET_MESSAGE_TYPE_DNS_HELPER);
606 hdr->size = htons (buftun_size);
609 else if (FD_ISSET (1, &fds_w))
611 ssize_t written = write (1, buftun_read, buftun_size);
615 if ( (errno == EINTR) ||
618 fprintf (stderr, "write-error to stdout: %s\n", strerror (errno));
623 fprintf (stderr, "write returned 0\n");
626 buftun_size -= written;
627 buftun_read += written;
630 if (FD_ISSET (0, &fds_r))
632 bufin_size = read (0, bufin + bufin_rpos, MAX_SIZE - bufin_rpos);
633 if (-1 == bufin_size)
636 if ( (errno == EINTR) ||
639 fprintf (stderr, "read-error: %s\n", strerror (errno));
645 fprintf (stderr, "EOF on stdin\n");
649 struct GNUNET_MessageHeader *hdr;
652 bufin_rpos += bufin_size;
653 if (bufin_rpos < sizeof (struct GNUNET_MessageHeader))
655 hdr = (struct GNUNET_MessageHeader *) bufin;
656 if (ntohs (hdr->type) != GNUNET_MESSAGE_TYPE_DNS_HELPER)
658 fprintf (stderr, "protocol violation!\n");
661 if (ntohs (hdr->size) > bufin_rpos)
663 bufin_read = bufin + sizeof (struct GNUNET_MessageHeader);
664 bufin_size = ntohs (hdr->size) - sizeof (struct GNUNET_MessageHeader);
665 bufin_rpos -= bufin_size + sizeof (struct GNUNET_MessageHeader);
668 else if (FD_ISSET (fd_tun, &fds_w))
670 ssize_t written = write (fd_tun, bufin_read, bufin_size);
674 if ( (errno == EINTR) ||
677 fprintf (stderr, "write-error to tun: %s\n", strerror (errno));
682 fprintf (stderr, "write returned 0\n");
686 bufin_size -= written;
687 bufin_read += written;
690 memmove (bufin, bufin_read, bufin_rpos);
691 bufin_read = NULL; /* start reading again */
703 * Main function of "gnunet-helper-dns", which opens a VPN tunnel interface,
704 * redirects all outgoing DNS traffic (except from the specified port) to that
705 * interface and then passes traffic from and to the interface via stdin/stdout.
707 * Once stdin/stdout close or have other errors, the tunnel is closed and the
708 * DNS traffic redirection is stopped.
710 * @param argc number of arguments
711 * @param argv 0: binary name (should be "gnunet-helper-vpn")
712 * 1: tunnel interface name (typically "gnunet-dns")
713 * 2: IPv6 address for the tunnel ("FE80::1")
714 * 3: IPv6 netmask length in bits ("64")
715 * 4: IPv4 address for the tunnel ("1.2.3.4")
716 * 5: IPv4 netmask ("255.255.0.0")
717 * 6: skip sysctl, routing and iptables setup ("0")
718 * @return 0 on success, otherwise code indicating type of error:
719 * 1 wrong number of arguments
720 * 2 invalid arguments (i.e. port number / prefix length wrong)
721 * 3 iptables not executable
722 * 4 ip not executable
723 * 5 failed to initialize tunnel interface
724 * 6 failed to initialize control pipe
725 * 8 failed to change routing table, cleanup successful
726 * 9-23 failed to change routing table and failed to undo some changes to routing table
727 * 24 failed to drop privs
728 * 25-39 failed to drop privs and then failed to undo some changes to routing table
729 * 40 failed to regain privs
730 * 41-55 failed to regain prisv and then failed to undo some changes to routing table
731 * 254 insufficient priviledges
732 * 255 failed to handle kill signal properly
735 main (int argc, char *const*argv)
746 fprintf (stderr, "Fatal: must supply 6 arguments!\n");
750 /* assert privs so we can modify the firewall rules! */
752 #ifdef HAVE_SETRESUID
753 if (0 != setresuid (uid, 0, 0))
755 fprintf (stderr, "Failed to setresuid to root: %s\n", strerror (errno));
759 if (0 != seteuid (0))
761 fprintf (stderr, "Failed to seteuid back to root: %s\n", strerror (errno));
765 if (0 == strncmp (argv[6], "1", 2))
770 /* verify that the binaries we care about are executable */
771 if (0 == access ("/sbin/iptables", X_OK))
772 sbin_iptables = "/sbin/iptables";
773 else if (0 == access ("/usr/sbin/iptables", X_OK))
774 sbin_iptables = "/usr/sbin/iptables";
778 "Fatal: executable iptables not found in approved directories: %s\n",
782 if (0 == access ("/sbin/ip6tables", X_OK))
783 sbin_ip6tables = "/sbin/ip6tables";
784 else if (0 == access ("/usr/sbin/ip6tables", X_OK))
785 sbin_ip6tables = "/usr/sbin/ip6tables";
789 "Fatal: executable ip6tables not found in approved directories: %s\n",
793 if (0 == access ("/sbin/ip", X_OK))
794 sbin_ip = "/sbin/ip";
795 else if (0 == access ("/usr/sbin/ip", X_OK))
796 sbin_ip = "/usr/sbin/ip";
800 "Fatal: executable ip not found in approved directories: %s\n",
804 if (0 == access ("/sbin/sysctl", X_OK))
805 sbin_sysctl = "/sbin/sysctl";
806 else if (0 == access ("/usr/sbin/sysctl", X_OK))
807 sbin_sysctl = "/usr/sbin/sysctl";
811 "Fatal: executable sysctl not found in approved directories: %s\n",
817 /* setup 'mygid' string */
818 snprintf (mygid, sizeof (mygid), "%d", (int) getegid());
820 /* do not die on SIGPIPE */
821 if (SIG_ERR == signal (SIGPIPE, SIG_IGN))
823 fprintf (stderr, "Failed to protect against SIGPIPE: %s\n",
828 /* setup pipe to shutdown nicely on SIGINT */
829 if (0 != pipe (cpipe))
832 "Fatal: could not setup control pipe: %s\n",
836 if (cpipe[0] >= FD_SETSIZE)
838 fprintf (stderr, "Pipe file descriptor to large: %d", cpipe[0]);
839 (void) close (cpipe[0]);
840 (void) close (cpipe[1]);
844 /* make pipe non-blocking, as we theoretically could otherwise block
845 in the signal handler */
846 int flags = fcntl (cpipe[1], F_GETFL);
849 fprintf (stderr, "Failed to read flags for pipe: %s", strerror (errno));
850 (void) close (cpipe[0]);
851 (void) close (cpipe[1]);
855 if (0 != fcntl (cpipe[1], F_SETFL, flags))
857 fprintf (stderr, "Failed to make pipe non-blocking: %s", strerror (errno));
858 (void) close (cpipe[0]);
859 (void) close (cpipe[1]);
863 if ( (SIG_ERR == signal (SIGTERM, &signal_handler)) ||
864 #if (SIGTERM != GNUNET_TERM_SIG)
865 (SIG_ERR == signal (GNUNET_TERM_SIG, &signal_handler)) ||
867 (SIG_ERR == signal (SIGINT, &signal_handler)) ||
868 (SIG_ERR == signal (SIGHUP, &signal_handler)) )
871 "Fatal: could not initialize signal handler: %s\n",
873 (void) close (cpipe[0]);
874 (void) close (cpipe[1]);
879 /* get interface name */
880 strncpy (dev, argv[1], IFNAMSIZ);
881 dev[IFNAMSIZ - 1] = '\0';
883 /* Disable rp filtering */
886 char *const sysctl_args[] = {"sysctl", "-w",
887 "net.ipv4.conf.all.rp_filter=0", NULL};
888 char *const sysctl_args2[] = {"sysctl", "-w",
889 "net.ipv4.conf.default.rp_filter=0", NULL};
890 if ((0 != fork_and_exec (sbin_sysctl, sysctl_args)) ||
891 (0 != fork_and_exec (sbin_sysctl, sysctl_args2)))
894 "Failed to disable rp filtering.\n");
900 /* now open virtual interface (first part that requires root) */
901 if (-1 == (fd_tun = init_tun (dev)))
903 fprintf (stderr, "Fatal: could not initialize tun-interface\n");
904 (void) signal (SIGTERM, SIG_IGN);
905 #if (SIGTERM != GNUNET_TERM_SIG)
906 (void) signal (GNUNET_TERM_SIG, SIG_IGN);
908 (void) signal (SIGINT, SIG_IGN);
909 (void) signal (SIGHUP, SIG_IGN);
910 (void) close (cpipe[0]);
911 (void) close (cpipe[1]);
915 /* now set interface addresses */
917 const char *address = argv[2];
918 long prefix_len = atol (argv[3]);
920 if ((prefix_len < 1) || (prefix_len > 127))
922 fprintf (stderr, "Fatal: prefix_len out of range\n");
923 (void) signal (SIGTERM, SIG_IGN);
924 #if (SIGTERM != GNUNET_TERM_SIG)
925 (void) signal (GNUNET_TERM_SIG, SIG_IGN);
927 (void) signal (SIGINT, SIG_IGN);
928 (void) signal (SIGHUP, SIG_IGN);
929 (void) close (cpipe[0]);
930 (void) close (cpipe[1]);
933 set_address6 (dev, address, prefix_len);
937 const char *address = argv[4];
938 const char *mask = argv[5];
940 set_address4 (dev, address, mask);
944 /* update routing tables -- next part why we need SUID! */
945 /* Forward everything from our EGID (which should only be held
946 by the 'gnunet-service-dns') and with destination
947 to port 53 on UDP, without hijacking */
950 r = 8; /* failed to fully setup routing table */
952 char *const mangle_args[] =
954 "iptables", "-m", "owner", "-t", "mangle", "-I", "OUTPUT", "1", "-p",
955 "udp", "--gid-owner", mygid, "--dport", DNS_PORT, "-j",
958 if (0 != fork_and_exec (sbin_iptables, mangle_args))
962 char *const mangle_args[] =
964 "ip6tables", "-m", "owner", "-t", "mangle", "-I", "OUTPUT", "1", "-p",
965 "udp", "--gid-owner", mygid, "--dport", DNS_PORT, "-j",
968 if (0 != fork_and_exec (sbin_ip6tables, mangle_args))
969 goto cleanup_mangle_1b;
971 /* Mark all of the other DNS traffic using our mark DNS_MARK,
972 unless it is on a link-local IPv6 address, which we cannot support. */
974 char *const mark_args[] =
976 "iptables", "-t", "mangle", "-I", "OUTPUT", "2", "-p",
977 "udp", "--dport", DNS_PORT,
978 "-j", "MARK", "--set-mark", DNS_MARK,
981 if (0 != fork_and_exec (sbin_iptables, mark_args))
982 goto cleanup_mangle_1;
985 char *const mark_args[] =
987 "ip6tables", "-t", "mangle", "-I", "OUTPUT", "2", "-p",
988 "udp", "--dport", DNS_PORT,
989 "!", "-s", "fe80::/10", /* this line excludes link-local traffic */
990 "-j", "MARK", "--set-mark", DNS_MARK,
993 if (0 != fork_and_exec (sbin_ip6tables, mark_args))
994 goto cleanup_mark_2b;
996 /* Forward all marked DNS traffic to our DNS_TABLE */
998 char *const forward_args[] =
1000 "ip", "rule", "add", "fwmark", DNS_MARK, "table", DNS_TABLE, NULL
1002 if (0 != fork_and_exec (sbin_ip, forward_args))
1003 goto cleanup_mark_2;
1006 char *const forward_args[] =
1008 "ip", "-6", "rule", "add", "fwmark", DNS_MARK, "table", DNS_TABLE, NULL
1010 if (0 != fork_and_exec (sbin_ip, forward_args))
1011 goto cleanup_forward_3b;
1013 /* Finally, add rule in our forwarding table to pass to our virtual interface */
1015 char *const route_args[] =
1017 "ip", "route", "add", "default", "dev", dev,
1018 "table", DNS_TABLE, NULL
1020 if (0 != fork_and_exec (sbin_ip, route_args))
1021 goto cleanup_forward_3;
1024 char *const route_args[] =
1026 "ip", "-6", "route", "add", "default", "dev", dev,
1027 "table", DNS_TABLE, NULL
1029 if (0 != fork_and_exec (sbin_ip, route_args))
1030 goto cleanup_route_4b;
1034 /* drop privs *except* for the saved UID; this is not perfect, but better
1035 than doing nothing */
1036 #ifdef HAVE_SETRESUID
1037 if (0 != setresuid (uid, uid, 0))
1039 fprintf (stderr, "Failed to setresuid: %s\n", strerror (errno));
1041 goto cleanup_route_4;
1044 /* Note: no 'setuid' here as we must keep our saved UID as root */
1045 if (0 != seteuid (uid))
1047 fprintf (stderr, "Failed to seteuid: %s\n", strerror (errno));
1049 goto cleanup_route_4;
1053 r = 0; /* did fully setup routing table (if nothing else happens, we were successful!) */
1055 /* now forward until we hit a problem */
1058 /* now need to regain privs so we can remove the firewall rules we added! */
1059 #ifdef HAVE_SETRESUID
1060 if (0 != setresuid (uid, 0, 0))
1062 fprintf (stderr, "Failed to setresuid back to root: %s\n", strerror (errno));
1064 goto cleanup_route_4;
1067 if (0 != seteuid (0))
1069 fprintf (stderr, "Failed to seteuid back to root: %s\n", strerror (errno));
1071 goto cleanup_route_4;
1075 /* update routing tables again -- this is why we could not fully drop privs */
1076 /* now undo updating of routing tables; normal exit or clean-up-on-error case */
1080 char *const route_clean_args[] =
1082 "ip", "-6", "route", "del", "default", "dev", dev,
1083 "table", DNS_TABLE, NULL
1085 if (0 != fork_and_exec (sbin_ip, route_clean_args))
1091 char *const route_clean_args[] =
1093 "ip", "route", "del", "default", "dev", dev,
1094 "table", DNS_TABLE, NULL
1096 if (0 != fork_and_exec (sbin_ip, route_clean_args))
1102 char *const forward_clean_args[] =
1104 "ip", "-6", "rule", "del", "fwmark", DNS_MARK, "table", DNS_TABLE, NULL
1106 if (0 != fork_and_exec (sbin_ip, forward_clean_args))
1112 char *const forward_clean_args[] =
1114 "ip", "rule", "del", "fwmark", DNS_MARK, "table", DNS_TABLE, NULL
1116 if (0 != fork_and_exec (sbin_ip, forward_clean_args))
1122 char *const mark_clean_args[] =
1124 "ip6tables", "-t", "mangle", "-D", "OUTPUT", "-p", "udp",
1125 "--dport", DNS_PORT,
1126 "!", "-s", "fe80::/10", /* this line excludes link-local traffic */
1127 "-j", "MARK", "--set-mark", DNS_MARK, NULL
1129 if (0 != fork_and_exec (sbin_ip6tables, mark_clean_args))
1135 char *const mark_clean_args[] =
1137 "iptables", "-t", "mangle", "-D", "OUTPUT", "-p", "udp",
1138 "--dport", DNS_PORT, "-j", "MARK", "--set-mark", DNS_MARK, NULL
1140 if (0 != fork_and_exec (sbin_iptables, mark_clean_args))
1146 char *const mangle_clean_args[] =
1148 "ip6tables", "-m", "owner", "-t", "mangle", "-D", "OUTPUT", "-p", "udp",
1149 "--gid-owner", mygid, "--dport", DNS_PORT, "-j", "ACCEPT",
1152 if (0 != fork_and_exec (sbin_ip6tables, mangle_clean_args))
1158 char *const mangle_clean_args[] =
1160 "iptables", "-m", "owner", "-t", "mangle", "-D", "OUTPUT", "-p", "udp",
1161 "--gid-owner", mygid, "--dport", DNS_PORT, "-j", "ACCEPT",
1164 if (0 != fork_and_exec (sbin_iptables, mangle_clean_args))
1169 /* close virtual interface */
1170 (void) close (fd_tun);
1171 /* remove signal handler so we can close the pipes */
1172 (void) signal (SIGTERM, SIG_IGN);
1173 #if (SIGTERM != GNUNET_TERM_SIG)
1174 (void) signal (GNUNET_TERM_SIG, SIG_IGN);
1176 (void) signal (SIGINT, SIG_IGN);
1177 (void) signal (SIGHUP, SIG_IGN);
1178 (void) close (cpipe[0]);
1179 (void) close (cpipe[1]);
1183 /* end of gnunet-helper-dns.c */