unreadable firejail.users database fixes

run firecfg with umask 022 and print a diagnostic message if
the database is not readable.

closes #2225

src/firecfg/main.c

@@ -316,6 +316,9 @@ int main(int argc, char **argv) {
  int i;
  int bindir_set = 0;
 
+ // set umask
+ umask(022);
+
  // user setup
  char *user = get_user();
  assert(user);

src/lib/firejail_user.c

@@ -119,9 +119,13 @@ int firejail_user_check(const char *name) {
  }
 
  FILE *fp = fopen(fname, "r");
+ if (!fp) {
+ fprintf(stderr, "Error: cannot open %s for reading. "
+ "See \"man firejail-users\" for more information about this file.\n", fname);
+ perror("fopen");
+ exit(1);
+ }
  free(fname);
- if (!fp)
- return 0;
 
  char buf[MAXBUF];
  while (fgets(buf, MAXBUF, fp)) {
@@ -165,8 +169,9 @@ void firejail_user_add(const char *name) {
  return;
  }
  }
+ else
+ printf("Creating %s\n", fname);
 
- printf("%s created\n", fname);
  FILE *fp = fopen(fname, "a+");
  if (!fp) {
  fprintf(stderr, "Error: cannot open %s\n", fname);