charon-tkm: charon: Avoid potential TOCTOU issues when accessing/writing PID file

Same as the previous commit.

diff --git a/src/charon-tkm/src/charon-tkm.c b/src/charon-tkm/src/charon-tkm.c
index 5f85276ff9fc0b57d08079e5f200af24375050f7..671a043a53db38ce69f27a7ecf99e61da7632e08 100644 (file)
--- a/src/charon-tkm/src/charon-tkm.c
+++ b/src/charon-tkm/src/charon-tkm.c
@@ -174,23 +174,35 @@ static bool lookup_uid_gid()
 static bool check_pidfile()
 {
        struct stat stb;
+       int fd, flags = 0;
 
-       if (stat(pidfile_name, &stb) == 0)
+#ifndef WIN32
+       flags |= O_NOFOLLOW;
+#endif
+       fd = open(pidfile_name, O_RDONLY | flags);
+       if (fd != -1)
        {
-               pidfile = fopen(pidfile_name, "r");
-               if (pidfile)
+               if (fstat(fd, &stb) == 0 && S_ISREG(stb.st_mode))
                {
                        char buf[64];
                        pid_t pid = 0;
 
-                       memset(buf, 0, sizeof(buf));
-                       if (fread(buf, 1, sizeof(buf), pidfile))
+                       pidfile = fdopen(fd, "r");
+                       if (pidfile)
+                       {
+                               memset(buf, 0, sizeof(buf));
+                               if (fread(buf, 1, sizeof(buf), pidfile))
+                               {
+                                       buf[sizeof(buf) - 1] = '\0';
+                                       pid = atoi(buf);
+                               }
+                               fclose(pidfile);
+                               pidfile = NULL;
+                       }
+                       else
                        {
-                               buf[sizeof(buf) - 1] = '\0';
-                               pid = atoi(buf);
+                               close(fd);
                        }
-                       fclose(pidfile);
-                       pidfile = NULL;
                        if (pid && pid != getpid() && kill(pid, 0) == 0)
                        {
                                DBG1(DBG_DMN, "%s already running ('%s' exists)", dmn_name,
@@ -198,39 +210,45 @@ static bool check_pidfile()
                                return TRUE;
                        }
                }
+               else
+               {
+                       close(fd);
+               }
+       }
+
+       if (fd != -1 || errno != ENOENT)
+       {
                DBG1(DBG_DMN, "removing pidfile '%s', process not running", pidfile_name);
                unlink(pidfile_name);
        }
 
-       /* create new pidfile */
-       pidfile = fopen(pidfile_name, "w");
-       if (pidfile)
+       /* create new pidfile securely without following symlinks */
+       fd = open(pidfile_name, O_CREAT | O_EXCL | O_WRONLY, 0644);
+       if (fd == -1)
        {
-               int fd;
-
-               fd = fileno(pidfile);
-               if (fd == -1)
-               {
-                       DBG1(DBG_DMN, "unable to determine fd for '%s'", pidfile_name);
-                       return TRUE;
-               }
-               if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
-               {
-                       DBG1(DBG_LIB, "setting FD_CLOEXEC for '%s' failed: %s",
-                                pidfile_name, strerror(errno));
-               }
-               ignore_result(fchown(fd,
-                                                        lib->caps->get_uid(lib->caps),
-                                                        lib->caps->get_gid(lib->caps)));
-               fprintf(pidfile, "%d\n", getpid());
-               fflush(pidfile);
-               return FALSE;
+               DBG1(DBG_DMN, "unable to create pidfile '%s'", pidfile_name);
+               return TRUE;
        }
-       else
+       if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
        {
-               DBG1(DBG_DMN, "unable to create pidfile '%s'", pidfile_name);
+               DBG1(DBG_LIB, "setting FD_CLOEXEC for '%s' failed: %s",
+                        pidfile_name, strerror(errno));
+       }
+       ignore_result(fchown(fd,
+                                                lib->caps->get_uid(lib->caps),
+                                                lib->caps->get_gid(lib->caps)));
+       pidfile = fdopen(fd, "w");
+       if (!pidfile)
+       {
+               DBG1(DBG_DMN, "unable to open pidfile '%s': %s", pidfile_name,
+                        strerror(errno));
+               close(fd);
+               unlink(pidfile_name);
                return TRUE;
        }
+       fprintf(pidfile, "%d\n", getpid());
+       fflush(pidfile);
+       return FALSE;
 }
 
 /**