drop group privileges before user privileges

[wall-notify/wall-notify.git] / src / wall-notify.c

diff --git a/src/wall-notify.c b/src/wall-notify.c
index bbc783b5e884514ca1f793da674ba22d71bc5415..e7106be07ca58a8cb731d3f7bcdce839bde76b63 100644 (file)
--- a/src/wall-notify.c
+++ b/src/wall-notify.c
@@ -67,7 +67,7 @@ static void setup_signals(void) {
     sigaction(SIGUSR2, &action, NULL);
 }
 
-static int open_tty(void) {
+static int open_tty(int public) {
     int ptm;
     const char *name;
 
@@ -81,12 +81,14 @@ static int open_tty(void) {
 
     /* Prevent write access for other users so they can't use wall to send
      * messages to this program. */
-    name = ptsname(ptm);
-    if (!name) {
-        return -1;
-    }
-    if (chmod(name, S_IRUSR | S_IWUSR) != 0) {
-        return -1;
+    if (!public) {
+        name = ptsname(ptm);
+        if (!name) {
+            return -1;
+        }
+        if (chmod(name, S_IRUSR | S_IWUSR) != 0) {
+            return -1;
+        }
     }
 
     if (unlockpt(ptm) != 0) {
@@ -212,14 +214,14 @@ static void drop_privileges(void) {
     gid = getgid();
 
     /* Drop all privileges. */
-    if (setresuid(uid, uid, uid) != 0) {
-        perror("setresuid");
-        exit(EXIT_FAILURE);
-    }
     if (setresgid(gid, gid, gid) != 0) {
         perror("setresgid");
         exit(EXIT_FAILURE);
     }
+    if (setresuid(uid, uid, uid) != 0) {
+        perror("setresuid");
+        exit(EXIT_FAILURE);
+    }
 
     /* Verify all privileges were dropped. */
     if (getresuid(&ruid, &euid, &suid) != 0) {
@@ -359,10 +361,12 @@ static void *x11_event_loop_thread(void *unused) {
 #endif
 
 static void usage(const char *argv0) {
-    fprintf(stderr, "usage: %s [-X] <cmd args..>\n", argv0);
+    fprintf(stderr, "usage: %s [-X] [-m] [-v] <cmd args..>\n", argv0);
     fprintf(stderr, "Pass wall messages to <cmd args..>.\n");
     fprintf(stderr, "\n");
     fprintf(stderr, "-X quit when the current X session terminates\n");
+    fprintf(stderr, "-m allow messages from normal users (like `mesg y`)\n");
+    fprintf(stderr, "-v display version\n");
 #ifdef DONT_USE_X11
     fprintf(stderr, "\n");
     fprintf(stderr, "compiled without X11 support, -X disabled\n");
@@ -372,7 +376,7 @@ static void usage(const char *argv0) {
 
 
 int main(int argc, char **argv) {
-    int option, enable_x11;
+    int option, enable_x11, mesg_yes;
     int ptm, pts;
     char *name;
 
@@ -380,6 +384,7 @@ int main(int argc, char **argv) {
     opterr = 0;
 
     enable_x11 = 0;
+    mesg_yes = 0;
 
     /*
      * Glibc violates POSIX by default and skips over non-option arguments and
@@ -388,14 +393,23 @@ int main(int argc, char **argv) {
      * the optstring with "+" fixes this behaver. This is not POSIX
      * compatible, but the option should be ignored on other systems.
      */
-    while ((option = getopt(argc, argv, "+Xh")) != -1) {
+    while ((option = getopt(argc, argv, "+Xmhv")) != -1) {
         switch (option) {
             case 'X':
                 enable_x11 = 1;
                 break;
+            case 'm':
+                mesg_yes = 1;
+                break;
             case 'h':
                 usage(argv[0]);
                 break;
+            case 'v':
+                printf("%s%s\n",
+                       PACKAGE_STRING,
+                       strlen(GIT_VERSION) ? " (Git " GIT_VERSION ")" : "");
+                exit(0);
+                break;
             default:
                 fprintf(stderr, "%s: unknown option '%s'!\n\n",
                                 argv[0], argv[optind - 1]);
@@ -411,7 +425,7 @@ int main(int argc, char **argv) {
     /* Arguments for notification program. */
     argv += optind;
 
-    ptm = open_tty();
+    ptm = open_tty(mesg_yes);
     if (ptm < 0) {
         perror("open_tty");
         exit(EXIT_FAILURE);