Problem - Kevin Tafuro

if (!(fd = opendir("."))) break;
if (fstat(dirfd(fd), &f) = = -1) {
closedir(fd);
break;
}
closedir(fd);
if (l.st_mode != f.st_mode || l.st_ino != f.st_ino || l.st_dev != f.st_dev)
break;
if ((f.st_mode & (S_IWOTH | S_IWGRP)) || (f.st_uid && f.st_uid != uid)) {
rc = 0;
break;
}
dir = "..";
if (lstat(dir, &l) = = -1) break;
if (!getcwd(new_dir, PATH_MAX + 1)) break;
} while (new_dir[1]); /* new_dir[0] will always be a slash */
if (!new_dir[1]) rc = 1;
fchdir(dirfd(start));
closedir(start);
return rc;
}
2.5 Erasing Files Securely
Problem
You want to erase a file securely, preventing recovery of any data via “undelete” tools
or any inspection of the disk for data that has been left behind.
Solution
Write over the data in the file multiple times, varying the data written each time. You
should write both random and patterned data for maximum effectiveness.
Discussion
It is extremely difficult, if not outright impossible, to guarantee that
the contents of a file are completely unrecoverable on modern operating
systems that offer logging filesystems, virtual memory, and other
such features.
Securely deleting files from disk is not as simple as issuing a system call to delete the
file from the filesystem. The first problem is that most delete operations do not do
anything to the data; they merely delete any underlying metadata that the filesystem
uses to associate the file contents with the filename. The storage space where the
This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.
Erasing Files Securely | 47