daemon: Prevent new daemon created on same machine

+ Only one daemon on the machine listening to fifo
+ fifo will not be unlinked by the new daemon init
+ Open fd and work with fchown avoiding TOCTOU

Signed-off-by: LUU QUANG MINH <Minh.LuuQuang@vn.bosch.com>
Signed-off-by: andv <fixed-term.An.DuVan@vn.bosch.com>

Author: LUU QUANG MINH

CMakeLists.txt

@@ -380,6 +380,7 @@ if(WITH_GIT_SUBMODULE)
 endif()
 
 if(WITH_DLT_UNIT_TESTS)
+    set(DLT_IPC "UNIX_SOCKET")
     find_package(GTest)
     if(GTEST_FOUND)
         find_package(PkgConfig REQUIRED)

src/daemon/dlt-daemon.c

@@ -1590,9 +1590,13 @@ static int dlt_daemon_init_fifo(DltDaemonLocal *daemon_local)
     /* open named pipe(FIFO) to receive DLT messages from users */
     umask(0);
 
-    /* Try to delete existing pipe, ignore result of unlink */
+    /* Valid fifo means there is a daemon running, stop init phase of the new */
     const char *tmpFifo = daemon_local->flags.daemonFifoName;
-    unlink(tmpFifo);
+    if (access(tmpFifo, F_OK) == 0) {
+        dlt_vlog(LOG_WARNING, "FIFO user %s is in use (%s)!\n",
+                 tmpFifo, strerror(errno));
+        return -1;
+    }
 
     ret = mkfifo(tmpFifo, S_IRUSR | S_IWUSR | S_IWGRP);
 
@@ -1602,13 +1606,21 @@ static int dlt_daemon_init_fifo(DltDaemonLocal *daemon_local)
         return -1;
     } /* if */
 
+    fd = open(tmpFifo, O_RDWR);
+
+    if (fd == -1) {
+        dlt_vlog(LOG_WARNING, "FIFO user %s cannot be opened (%s)!\n",
+                 tmpFifo, strerror(errno));
+        return -1;
+    } /* if */
+
     /* Set group of daemon FIFO */
     if (daemon_local->flags.daemonFifoGroup[0] != 0) {
         errno = 0;
         struct group *group_dlt = getgrnam(daemon_local->flags.daemonFifoGroup);
 
         if (group_dlt) {
-            ret = chown(tmpFifo, -1, group_dlt->gr_gid);
+            ret = fchown(fd, -1, group_dlt->gr_gid);
 
             if (ret == -1)
                 dlt_vlog(LOG_ERR, "FIFO user %s cannot be chowned to group %s (%s)\n",
@@ -1628,14 +1640,6 @@ static int dlt_daemon_init_fifo(DltDaemonLocal *daemon_local)
         }
     }
 
-    fd = open(tmpFifo, O_RDWR);
-
-    if (fd == -1) {
-        dlt_vlog(LOG_WARNING, "FIFO user %s cannot be opened (%s)!\n",
-                 tmpFifo, strerror(errno));
-        return -1;
-    } /* if */
-
 #ifdef __linux__
     /* F_SETPIPE_SZ and F_GETPIPE_SZ are only supported for Linux.
      * For other OSes it depends on its system e.g. pipe manager.