file_is_legal

SFL
Version 2.11

`file_is_legal`

#include "sflfile.h"
Bool
file_is_legal (
    const char *arg_filename)

Synopsis

Checks whether the specified file is 'legal', which is a system-dependent definition. Under 32-bit Windows, a legal file is one who's name is not a shortened 8.3 version of a long name. This can be used to bypass filename-based security schemes. On other systems, the notion of 'illegal' is not defined. Returns TRUE if the file exists and is legal. Returns FALSE otherwise.

Source Code - (sflfile.c)

{
#if (defined (WIN32))
    static WIN32_FIND_DATA
        found;
    HANDLE
        handle;
    char
        *filename,                      /*  Our copy of arg_filename         */
        *slash,                         /*  Position of '\' in filename      */
        *component;                     /*  Component to compare             */
    Bool
        feedback;                       /*  Function feedback                */

    /*  For each path component of the filename, check that the long form
     *  of the name is the same as the short form.  We scan backwards
     *  from the end of the filename, get the full pathname, and compare
     *  the last component each time:
     *
     *      aaa\bbb\ccc\name.ext    name.ext
     *      aaa\bbb\ccc             ccc
     *      aaa\bbb                 bbb
     *      aaa                     aaa
     */

    if (system_devicename (arg_filename))
        return (FALSE);                 /*  Not allowed on device names      */

    filename = mem_strdup (arg_filename);
    feedback = TRUE;                    /*  Assume we match everything       */
    strconvch (filename, '/', '\\');
    if (strlast (filename) == '\\')
        strlast (filename) = '\0';      /*  Drop any trailing slash          */

    do
      {
        slash     = strrchr (filename, '\\');
        component = slash? slash + 1: filename;
        handle    = FindFirstFile (filename, &found);

        if (handle != INVALID_HANDLE_VALUE
        &&  lexcmp (component, found.cFileName))
          {
            feedback = FALSE;
            break;
          }
        FindClose (handle);
        if (slash)
          {
            *slash = '\0';              /*  Cut filename at slash            */
            if (filename [1] == ':'
            &&  filename [2] == '\0')   /*  We're at a disk specifier        */
                break;                  /*    which is okay by now           */
          }
      }
    while (slash && *filename);
    mem_free (filename);
    return (feedback);

#else
    return (TRUE);               /*  On other OSes, all filenames are legal  */
#endif
}

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