alpine 3.6
tmpfile weakness #29

4

Weakness Breakdown


Definition:

A temporary file weakness occurs when a temporary file that is created and used by a high-privilege process is accidentally shared with a low-privilege process, on account of it being temporary and generated after all security controls have been applied. This allows the low-privilege process to read data from the high-privilege process (information leakage), or worse, influence the high-privilege process by modifying the shared temporary file.

Warning code(s):

Temporary file race condition.

File Name:

make/src/make-4.2.1/function.c

Context:

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

 
#include <dos/dos.h>
#include <proto/dos.h>

  BPTR child_stdout;
  char tmp_output[FILENAME_MAX];
  unsigned int maxlen = 200, i;
  int cc;
  char * buffer, * ptr;
  char ** aptr;
  int len = 0;
  char* batch_filename = NULL;

  /* Construct the argument list.  */
  command_argv = construct_command_argv (argv[0], NULL, NULL, 0,
                                         &batch_filename);
  if (command_argv == 0)
    return o;

  /* Note the mktemp() is a security hole, but this only runs on Amiga.
     Ideally we would use output_tmpfile(), but this uses a special
     Open(), not fopen(), and I'm not familiar enough with the code to mess
     with it.  */
  strcpy (tmp_output, "t:MakeshXXXXXXXX");
  mktemp (tmp_output);
  child_stdout = Open (tmp_output, MODE_NEWFILE);

  for (aptr=command_argv; *aptr; aptr++)
    len += strlen (*aptr) + 1;

  buffer = xmalloc (len + 1);
  ptr = buffer;

  for (aptr=command_argv; *aptr; aptr++)
    {
      strcpy (ptr, *aptr);
      ptr += strlen (ptr) + 1;
      *ptr ++ = ' ';
      *ptr = 0;
    }

  ptr[-1] = '\n';

  Execute (buffer, NULL, child_stdout);
  free (buffer);

  Close (child_stdout);

  child_stdout = Open (tmp_output, MODE_OLDFILE);
 

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