alpine 3.6
access weakness #512


Weakness Breakdown


An access weakness occurs when software does not properly implement permissions that could have unintended consequences if exploited by malicious actors. An example of this weakness is when a default username and password are set by the developer but do not get changed by the system administrator.

Warning code(s):

Ensure that umask is given most restrictive possible setting.

File Name:



The highlighted line of code below is the trigger point of this particular Alpine 3.6 access weakness.

 #include <sys/stat.h>
#include <sys/un.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include "mruby.h"
#include "mruby/array.h"
#include "mruby/string.h"
#include "mruby/variable.h"

static mrb_value
mrb_io_test_io_setup(mrb_state *mrb, mrb_value self)
  char rfname[]      = "tmp.mruby-io-test.XXXXXXXX";
  char wfname[]      = "tmp.mruby-io-test.XXXXXXXX";
  char symlinkname[] = "tmp.mruby-io-test.XXXXXXXX";
  char socketname[]  = "tmp.mruby-io-test.XXXXXXXX";
  char msg[] = "mruby io test\n";
  mode_t mask;
  int fd0, fd1, fd2, fd3;
  FILE *fp;
  struct sockaddr_un sun0;

  mask = umask(077);
  fd0 = mkstemp(rfname);
  fd1 = mkstemp(wfname);
  fd2 = mkstemp(symlinkname);
  fd3 = mkstemp(socketname);
  if (fd0 == -1 || fd1 == -1 || fd2 == -1 || fd3 == -1) {
    mrb_raise(mrb, E_RUNTIME_ERROR, "can't create temporary file");
    return mrb_nil_value();

  mrb_gv_set(mrb, mrb_intern_cstr(mrb, "$ mrbtest_io_rfname"), mrb_str_new_cstr(mrb, rfname));
  mrb_gv_set(mrb, mrb_intern_cstr(mrb, "$ mrbtest_io_wfname"), mrb_str_new_cstr(mrb, wfname));
  mrb_gv_set(mrb, mrb_intern_cstr(mrb, "$ mrbtest_io_symlinkname"), mrb_str_new_cstr(mrb, symlinkname));
  mrb_gv_set(mrb, mrb_intern_cstr(mrb, "$ mrbtest_io_socketname"), mrb_str_new_cstr(mrb, socketname));
  mrb_gv_set(mrb, mrb_intern_cstr(mrb, "$ mrbtest_io_msg"), mrb_str_new_cstr(mrb, msg));

  fp = fopen(rfname, "w");
  if (fp == NULL) {
    mrb_raise(mrb, E_RUNTIME_ERROR, "can't open temporary file");
    return mrb_nil_value();
  fputs(msg, fp);

  fp = fopen(wfname, "w"); 

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