open files O_CLOEXEC|O_EXCL

Dumb patch that adds O_CLOEXEC to all open/fopen
calls, even where it is obviously pointless.

While at it, also add O_EXCL where it might be
considered useful, for example to clear Coverity
warnings, or on files that subsequently are used
to configure a join sandbox.

Pure defense in depth, this patch should have no
observable effects.

1 files changed, 5 insertions, 20 deletions

diff --git a/src/firejail/fs_logger.c b/src/firejail/fs_logger.c
index 67ad4b52e..604e297b1 100644
--- a/src/firejail/fs_logger.c
+++ b/src/firejail/fs_logger.c
@@ -92,7 +92,7 @@ void fs_logger_print(void) {
         if (!head)
                 return;
 
-        FILE *fp = fopen(RUN_FSLOGGER_FILE, "a");
+        FILE *fp = fopen(RUN_FSLOGGER_FILE, "ae");
         if (!fp) {
                 perror("fopen");
                 return;
@@ -123,15 +123,8 @@ void fs_logger_print_log(pid_t pid) {
         // in case the pid is that of a firejail process, use the pid of the first child process
         pid = switch_to_child(pid);
 
-        // check privileges for non-root users
-        uid_t uid = getuid();
-        if (uid != 0) {
-                uid_t sandbox_uid = pid_get_uid(pid);
-                if (uid != sandbox_uid) {
-                        fprintf(stderr, "Error: permission denied\n");
-                        exit(1);
-                }
-        }
+        // exit if no permission to join the sandbox
+        check_join_permission(pid);
 
         // print RUN_FSLOGGER_FILE
         char *fname;
@@ -139,24 +132,16 @@ void fs_logger_print_log(pid_t pid) {
                 errExit("asprintf");
 
         EUID_ROOT();
-        struct stat s;
-        if (stat(fname, &s) == -1 || s.st_uid != 0) {
-                fprintf(stderr, "Error: Cannot access filesystem log\n");
-                exit(1);
-        }
-
-        /* coverity[toctou] */
-        FILE *fp = fopen(fname, "r");
+        FILE *fp = fopen(fname, "re");
+        free(fname);
         if (!fp) {
                 fprintf(stderr, "Error: Cannot open filesystem log\n");
                 exit(1);
         }
-
         char buf[MAXBUF];
         while (fgets(buf, MAXBUF, fp))
                 printf("%s", buf);
         fclose(fp);
-        free(fname);
 
         exit(0);
 }