* @brief helper to install firewall rules to hijack all DNS traffic
* and send it to our virtual interface (except for DNS traffic
* that originates on the specified port). We then
- * allow interacting with our virtual interface via stdin/stdout.
+ * allow interacting with our virtual interface via stdin/stdout.
* @author Philipp Tölke
* @author Christian Grothoff
*
* Naturally, neither of these problems can be helped as this is the
* fundamental purpose of the binary. Certifying that this code is
* "safe" thus only means that it doesn't allow anything else (such
- * as local priv. escalation, etc.).
+ * as local priv. escalation, etc.).
*
* The following list of people have reviewed this code and considered
* it safe (within specifications) since the last modification (if you
* reviewed it, please have your name added to the list):
*
- * - Christian Grothoff
+ * - Christian Grothoff
*/
#include "platform.h"
/**
* Need 'struct GNUNET_MessageHeader'.
*/
+#include "gnunet_crypto_lib.h"
#include "gnunet_common.h"
/**
}
+/**
+ * Open '/dev/null' and make the result the given
+ * file descriptor.
+ *
+ * @param target_fd desired FD to point to /dev/null
+ * @param flags open flags (O_RDONLY, O_WRONLY)
+ */
+static void
+open_dev_null (int target_fd,
+ int flags)
+{
+ int fd;
+
+ fd = open ("/dev/null", flags);
+ if (-1 == fd)
+ abort ();
+ if (fd == target_fd)
+ return;
+ if (-1 == dup2 (fd, target_fd))
+ {
+ (void) close (fd);
+ abort ();
+ }
+ (void) close (fd);
+}
+
+
/**
* Run the given command and wait for it to complete.
- *
+ *
* @param file name of the binary to run
* @param cmd command line arguments (as given to 'execv')
* @return 0 on success, 1 on any error
*/
static int
-fork_and_exec (const char *file,
+fork_and_exec (const char *file,
char *const cmd[])
{
int status;
pid = fork ();
if (-1 == pid)
{
- fprintf (stderr,
- "fork failed: %s\n",
+ fprintf (stderr,
+ "fork failed: %s\n",
strerror (errno));
return 1;
}
/* we are the child process */
/* close stdin/stdout to not cause interference
with the helper's main protocol! */
- (void) close (0);
- (void) close (1);
+ (void) close (0);
+ open_dev_null (0, O_RDONLY);
+ (void) close (1);
+ open_dev_null (1, O_WRONLY);
(void) execv (file, cmd);
/* can only get here on error */
- fprintf (stderr,
- "exec `%s' failed: %s\n",
+ fprintf (stderr,
+ "exec `%s' failed: %s\n",
file,
strerror (errno));
_exit (1);
}
/* keep running waitpid as long as the only error we get is 'EINTR' */
while ( (-1 == (ret = waitpid (pid, &status, 0))) &&
- (errno == EINTR) );
+ (errno == EINTR) );
if (-1 == ret)
{
- fprintf (stderr,
- "waitpid failed: %s\n",
+ fprintf (stderr,
+ "waitpid failed: %s\n",
strerror (errno));
return 1;
}
sa6.sin6_family = AF_INET6;
if (1 != inet_pton (AF_INET6, address, sa6.sin6_addr.s6_addr))
{
- fprintf (stderr, "Failed to parse address `%s': %s\n", address,
+ fprintf (stderr,
+ "Failed to parse IPv6 address `%s': %s\n",
+ address,
strerror (errno));
exit (1);
}
if (-1 == (fd = socket (PF_INET6, SOCK_DGRAM, 0)))
{
- fprintf (stderr, "Error creating socket: %s\n", strerror (errno));
- exit (1);
+ fprintf (stderr,
+ "Error creating IPv6 socket: %s (ignored)\n",
+ strerror (errno));
+ /* ignore error, maybe only IPv4 works on this system! */
+ return;
}
memset (&ifr, 0, sizeof (struct ifreq));
*/
if (1 != inet_pton (AF_INET, address, &addr->sin_addr.s_addr))
{
- fprintf (stderr, "Failed to parse address `%s': %s\n", address,
+ fprintf (stderr,
+ "Failed to parse IPv4 address `%s': %s\n",
+ address,
strerror (errno));
exit (1);
}
if (-1 == (fd = socket (PF_INET, SOCK_DGRAM, 0)))
{
- fprintf (stderr, "Error creating socket: %s\n", strerror (errno));
+ fprintf (stderr,
+ "Error creating IPv4 socket: %s\n",
+ strerror (errno));
exit (1);
}
return;
}
buftun_size -= written;
- buftun_read += written;
+ buftun_read += written;
}
if (FD_ISSET (0, &fds_r))
* 25-39 failed to drop privs and then failed to undo some changes to routing table
* 40 failed to regain privs
* 41-55 failed to regain prisv and then failed to undo some changes to routing table
+ * 254 insufficient priviledges
* 255 failed to handle kill signal properly
*/
int
char dev[IFNAMSIZ];
char mygid[32];
int fd_tun;
+ uid_t uid;
if (6 != argc)
{
return 1;
}
+ /* assert privs so we can modify the firewall rules! */
+ uid = getuid ();
+#ifdef HAVE_SETRESUID
+ if (0 != setresuid (uid, 0, 0))
+ {
+ fprintf (stderr, "Failed to setresuid to root: %s\n", strerror (errno));
+ return 254;
+ }
+#else
+ if (0 != seteuid (0))
+ {
+ fprintf (stderr, "Failed to seteuid back to root: %s\n", strerror (errno));
+ return 254;
+ }
+#endif
+
/* verify that the binaries were care about are executable */
if (0 == access ("/sbin/iptables", X_OK))
sbin_iptables = "/sbin/iptables";
sbin_iptables = "/usr/sbin/iptables";
else
{
- fprintf (stderr,
+ fprintf (stderr,
"Fatal: executable iptables not found in approved directories: %s\n",
strerror (errno));
return 3;
/* setup pipe to shutdown nicely on SIGINT */
if (0 != pipe (cpipe))
{
- fprintf (stderr,
+ fprintf (stderr,
"Fatal: could not setup control pipe: %s\n",
strerror (errno));
return 6;
}
}
if ( (SIG_ERR == signal (SIGTERM, &signal_handler)) ||
+#if (SIGTERM != GNUNET_TERM_SIG)
+ (SIG_ERR == signal (GNUNET_TERM_SIG, &signal_handler)) ||
+#endif
(SIG_ERR == signal (SIGINT, &signal_handler)) ||
- (SIG_ERR == signal (SIGHUP, &signal_handler)) )
- {
- fprintf (stderr,
+ (SIG_ERR == signal (SIGHUP, &signal_handler)) )
+ {
+ fprintf (stderr,
"Fatal: could not initialize signal handler: %s\n",
strerror (errno));
(void) close (cpipe[0]);
(void) close (cpipe[1]);
- return 7;
+ return 7;
}
return 5;
}
}
-
-
+
+
/* now open virtual interface (first part that requires root) */
if (-1 == (fd_tun = init_tun (dev)))
{
fprintf (stderr, "Fatal: could not initialize tun-interface\n");
(void) signal (SIGTERM, SIG_IGN);
+#if (SIGTERM != GNUNET_TERM_SIG)
+ (void) signal (GNUNET_TERM_SIG, SIG_IGN);
+#endif
(void) signal (SIGINT, SIG_IGN);
(void) signal (SIGHUP, SIG_IGN);
(void) close (cpipe[0]);
{
fprintf (stderr, "Fatal: prefix_len out of range\n");
(void) signal (SIGTERM, SIG_IGN);
+#if (SIGTERM != GNUNET_TERM_SIG)
+ (void) signal (GNUNET_TERM_SIG, SIG_IGN);
+#endif
(void) signal (SIGINT, SIG_IGN);
(void) signal (SIGHUP, SIG_IGN);
(void) close (cpipe[0]);
set_address4 (dev, address, mask);
}
-
+
/* update routing tables -- next part why we need SUID! */
/* Forward everything from our EGID (which should only be held
by the 'gnunet-service-dns') and with destination
to port 53 on UDP, without hijacking */
r = 8; /* failed to fully setup routing table */
{
- char *const mangle_args[] =
+ char *const mangle_args[] =
{
"iptables", "-m", "owner", "-t", "mangle", "-I", "OUTPUT", "1", "-p",
"udp", "--gid-owner", mygid, "--dport", DNS_PORT, "-j",
};
if (0 != fork_and_exec (sbin_iptables, mangle_args))
goto cleanup_rest;
- }
+ }
/* Mark all of the other DNS traffic using our mark DNS_MARK */
{
char *const mark_args[] =
/* drop privs *except* for the saved UID; this is not perfect, but better
than doing nothing */
- uid_t uid = getuid ();
#ifdef HAVE_SETRESUID
if (0 != setresuid (uid, uid, 0))
{
}
#else
/* Note: no 'setuid' here as we must keep our saved UID as root */
- if (0 != seteuid (uid))
+ if (0 != seteuid (uid))
{
fprintf (stderr, "Failed to seteuid: %s\n", strerror (errno));
r = 24;
/* now forward until we hit a problem */
run (fd_tun);
-
+
/* now need to regain privs so we can remove the firewall rules we added! */
#ifdef HAVE_SETRESUID
if (0 != setresuid (uid, 0, 0))
goto cleanup_route_4;
}
#else
- if (0 != seteuid (0))
+ if (0 != seteuid (0))
{
fprintf (stderr, "Failed to seteuid back to root: %s\n", strerror (errno));
r = 40;
goto cleanup_route_4;
}
#endif
-
+
/* update routing tables again -- this is why we could not fully drop privs */
/* now undo updating of routing tables; normal exit or clean-up-on-error case */
cleanup_route_4:
{
- char *const route_clean_args[] =
+ char *const route_clean_args[] =
{
"ip", "route", "del", "default", "dev", dev,
"table", DNS_TABLE, NULL
(void) close (fd_tun);
/* remove signal handler so we can close the pipes */
(void) signal (SIGTERM, SIG_IGN);
+#if (SIGTERM != GNUNET_TERM_SIG)
+ (void) signal (GNUNET_TERM_SIG, SIG_IGN);
+#endif
(void) signal (SIGINT, SIG_IGN);
(void) signal (SIGHUP, SIG_IGN);
(void) close (cpipe[0]);
projects / oweals / gnunet.git / blobdiff