Switch user ID/root directory with -Z before opening savefiles for output.

[tcpdump] / tcpdump.c

diff --git a/tcpdump.c b/tcpdump.c
index 4e524082ac06e7aef6d3cd790783c967ccea62eb..c8da36baa92592284844e58af56b537a647b3f55 100644 (file)
--- a/tcpdump.c
+++ b/tcpdump.c
@@ -154,7 +154,6 @@ static struct printer printers[] = {
 #ifdef DLT_ARCNET_LINUX
        { arcnet_linux_if_print, DLT_ARCNET_LINUX },
 #endif
-       { ether_if_print,       DLT_EN10MB },
        { token_if_print,       DLT_IEEE802 },
 #ifdef DLT_LANE8023
        { lane_if_print,        DLT_LANE8023 },
@@ -306,6 +305,7 @@ static struct printer printers[] = {
 };
 
 static struct ndo_printer ndo_printers[] = {
+       { ether_if_print,       DLT_EN10MB },
 #ifdef DLT_IPNET
        { ipnet_if_print,       DLT_IPNET },
 #endif
@@ -1258,6 +1258,30 @@ main(int argc, char **argv)
                (void)setsignal(SIGHUP, oldhandler);
 #endif /* WIN32 */
 
+#ifndef WIN32
+       /*
+        * If a user name was specified with "-Z", attempt to switch to
+        * that user's UID.  This would probably be used with sudo,
+        * to allow tcpdump to be run in a special restricted
+        * account (if you just want to allow users to open capture
+        * devices, and can't just give users that permission,
+        * you'd make tcpdump set-UID or set-GID).
+        *
+        * Tcpdump doesn't necessarily write only to one savefile;
+        * the general only way to allow a -Z instance to write to
+        * savefiles as the user under whose UID it's run, rather
+        * than as the user specified with -Z, would thus be to switch
+        * to the original user ID before opening a capture file and
+        * then switch back to the -Z user ID after opening the savefile.
+        * Switching to the -Z user ID only after opening the first
+        * savefile doesn't handle the general case.
+        */
+       if (getuid() == 0 || geteuid() == 0) {
+               if (username || chroot_dir)
+                       droproot(username, chroot_dir);
+       }
+#endif /* WIN32 */
+
        if (pcap_setfilter(pd, &fcode) < 0)
                error("%s", pcap_geterr(pd));
        if (WFileName) {
@@ -1311,16 +1335,7 @@ main(int argc, char **argv)
                callback = print_packet;
                pcap_userdata = (u_char *)&printinfo;
        }
-#ifndef WIN32
-       /*
-        * We cannot do this earlier, because we want to be able to open
-        * the file (if done) for writing before giving up permissions.
-        */
-       if (getuid() == 0 || geteuid() == 0) {
-               if (username || chroot_dir)
-                       droproot(username, chroot_dir);
-       }
-#endif /* WIN32 */
+
 #ifdef SIGINFO
        /*
         * We can't get statistics when reading from a file rather
@@ -1866,7 +1881,7 @@ usage(void)
 #endif /* WIN32 */
 #endif /* HAVE_PCAP_LIB_VERSION */
        (void)fprintf(stderr,
-"Usage: %s [-aAbd" D_FLAG "ef" I_FLAG J_FLAG "KlLnNOpqRStu" U_FLAG "vxX]" B_FLAG_USAGE " [ -c count ]\n", program_name);
+"Usage: %s [-aAbd" D_FLAG "efh" I_FLAG J_FLAG "KlLnNOpqRStu" U_FLAG "vxX]" B_FLAG_USAGE " [ -c count ]\n", program_name);
        (void)fprintf(stderr,
 "\t\t[ -C file_size ] [ -E algo:secret ] [ -F file ] [ -G seconds ]\n");
        (void)fprintf(stderr,