oping: Temporarily drop privileges if supported by the system.

[liboping.git] / src / oping.c

diff --git a/src/oping.c b/src/oping.c
index 0ef6ec6..d27f187 100644 (file)
--- a/src/oping.c
+++ b/src/oping.c
@@ -31,6 +31,10 @@
 # error "You don't have the standard C99 header files installed"
 #endif /* STDC_HEADERS */
 
+#if HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+
 #if HAVE_MATH_H
 # include <math.h>
 #endif
@@ -54,8 +58,16 @@
 # include <signal.h>
 #endif
 
+#if HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+
 #include "oping.h"
 
+#ifndef _POSIX_SAVED_IDS
+# define _POSIX_SAVED_IDS 0
+#endif
+
 typedef struct ping_context
 {
        char host[NI_MAXHOST];
@@ -73,6 +85,7 @@ typedef struct ping_context
 static double  opt_interval   = 1.0;
 static int     opt_addrfamily = PING_DEF_AF;
 static char   *opt_srcaddr    = NULL;
+static char   *opt_device     = NULL;
 static char   *opt_filename   = NULL;
 static int     opt_count      = -1;
 static int     opt_send_ttl   = 64;
@@ -107,7 +120,7 @@ static void context_destroy (ping_context_t *context)
        free (context);
 }
 
-static void usage_exit (const char *name)
+static void usage_exit (const char *name, int status)
 {
        int name_length;
 
@@ -122,13 +135,14 @@ static void usage_exit (const char *name)
                        "  -i interval  interval with which to send ICMP packets\n"
                        "  -t ttl       time to live for each ICMP packet\n"
                        "  -I srcaddr   source address\n"
+                       "  -D device    outgoing interface name\n"
                        "  -f filename  filename to read hosts from\n"
 
                        "\noping "PACKAGE_VERSION", http://verplant.org/liboping/\n"
                        "by Florian octo Forster <octo@verplant.org>\n"
                        "for contributions see `AUTHORS'\n",
                        name);
-       exit (1);
+       exit (status);
 }
 
 static int read_options (int argc, char **argv)
@@ -137,7 +151,7 @@ static int read_options (int argc, char **argv)
 
        while (1)
        {
-               optchar = getopt (argc, argv, "46c:hi:I:t:f:");
+               optchar = getopt (argc, argv, "46c:hi:I:t:f:D:");
 
                if (optchar == -1)
                        break;
@@ -188,6 +202,10 @@ static int read_options (int argc, char **argv)
                                }
                                break;
 
+                       case 'D':
+                               opt_device = optarg;
+                               break;
+
                        case 't':
                        {
                                int new_send_ttl;
@@ -201,8 +219,10 @@ static int read_options (int argc, char **argv)
                        }
 
                        case 'h':
+                               usage_exit (argv[0], 0);
+                               break;
                        default:
-                               usage_exit (argv[0]);
+                               usage_exit (argv[0], 1);
                }
        }
 
@@ -325,17 +345,42 @@ int main (int argc, char **argv)
 
        int optind;
        int i;
+       int status;
+#if _POSIX_SAVED_IDS
+       uid_t saved_set_uid;
+
+       /* Save the old effective user id */
+       saved_set_uid = geteuid ();
+       /* Set the effective user ID to the real user ID without changing the
+        * saved set-user ID */
+       status = seteuid (getuid ());
+       if (status != 0)
+       {
+               fprintf (stderr, "Temporarily dropping privileges "
+                               "failed: %s\n", strerror (errno));
+               exit (EXIT_FAILURE);
+       }
+#endif
 
        optind = read_options (argc, argv);
 
-       if ((optind >= argc) && (opt_filename == NULL)) {
-               usage_exit (argv[0]);
+#if !_POSIX_SAVED_IDS
+       /* Cannot temporarily drop privileges -> reject every file but "-". */
+       if ((opt_filename != NULL)
+                       && (strcmp ("-", opt_filename) != 0)
+                       && (getuid () != geteuid ()))
+       {
+               fprintf (stderr, "Your real and effective user IDs don't "
+                               "match. Reading from a file (option '-f')\n"
+                               "is therefore too risky. You can still read "
+                               "from STDIN using '-f -' if you like.\n"
+                               "Sorry.\n");
+               exit (EXIT_FAILURE);
        }
+#endif
 
-       if (geteuid () != 0)
-       {
-               fprintf (stderr, "Need superuser privileges to open a RAW socket. Sorry.\n");
-               return (1);
+       if ((optind >= argc) && (opt_filename == NULL)) {
+               usage_exit (argv[0], 1);
        }
 
        if ((ping = ping_construct ()) == NULL)
@@ -373,6 +418,15 @@ int main (int argc, char **argv)
                }
        }
 
+       if (opt_device != NULL)
+       {
+               if (ping_setopt (ping, PING_OPT_DEVICE, (void *) opt_device) != 0)
+               {
+                       fprintf (stderr, "Setting device failed: %s\n",
+                                       ping_get_error (ping));
+               }
+       }
+
        if (opt_filename != NULL)
        {
                FILE *infile;
@@ -394,6 +448,17 @@ int main (int argc, char **argv)
                        return (1);
                }
 
+#if _POSIX_SAVED_IDS
+               /* Regain privileges */
+               status = seteuid (saved_set_uid);
+               if (status != 0)
+               {
+                       fprintf (stderr, "Temporarily re-gaining privileges "
+                                       "failed: %s\n", strerror (errno));
+                       exit (EXIT_FAILURE);
+               }
+#endif
+
                while (fgets(line, sizeof(line), infile))
                {
                        /* Strip whitespace */
@@ -412,9 +477,31 @@ int main (int argc, char **argv)
                        }
                }
 
+#if _POSIX_SAVED_IDS
+               /* Drop privileges */
+               status = seteuid (getuid ());
+               if (status != 0)
+               {
+                       fprintf (stderr, "Temporarily dropping privileges "
+                                       "failed: %s\n", strerror (errno));
+                       exit (EXIT_FAILURE);
+               }
+#endif
+
                fclose(infile);
        }
 
+#if _POSIX_SAVED_IDS
+       /* Regain privileges */
+       status = seteuid (saved_set_uid);
+       if (status != 0)
+       {
+               fprintf (stderr, "Temporarily re-gaining privileges "
+                               "failed: %s\n", strerror (errno));
+               exit (EXIT_FAILURE);
+       }
+#endif
+
        for (i = optind; i < argc; i++)
        {
                if (ping_host_add (ping, argv[i]) < 0)
@@ -426,8 +513,18 @@ int main (int argc, char **argv)
                }
        }
 
-       /* Drop root privileges if we're setuid-root. */
-       setuid (getuid ());
+       /* Permanently drop root privileges if we're setuid-root. */
+       status = setuid (getuid ());
+       if (status != 0)
+       {
+               fprintf (stderr, "Dropping privileges failed: %s\n",
+                               strerror (errno));
+               exit (EXIT_FAILURE);
+       }
+
+#if _POSIX_SAVED_IDS
+       saved_set_uid = (uid_t) -1;
+#endif
 
        i = 0;
        for (iter = ping_iterator_get (ping);