Problem - Kevin Tafuro

if (!MakeTempFilename(lpszBuffer, dwBuffer)) {
hFile = INVALID_HANDLE_VALUE;
break;
}
hFile = CreateFile(lpszBuffer, GENERIC_READ | GENERIC_WRITE,
FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE,
0, CREATE_NEW,
FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE, 0);
if (hFile = = INVALID_HANDLE_VALUE && GetLastError( ) != ERROR_ALREADY_EXISTS)
break;
} while (hFile = = INVALID_HANDLE_VALUE);
return hFile;
}
See Also
Recipes 2.4, 11.11
2.12 Restricting Filesystem Access on Unix
Problem
You want to restrict your program’s ability to access important parts of the filesystem.
Solution
Unix systems provide a system call known as chroot( ) that will restrict the process’s
access to the filesystem. Specifically, chroot( ) alters a process’s perception of the
filesystem by changing its root directory, which effectively prevents the process from
accessing any part of the filesystem above the new root directory.
Discussion
Normally, a process’s root directory is the actual system root directory, which allows
the process to access any part of the filesystem. However, by using the chroot( ) system
call, a process can alter its view of the filesystem by changing its root directory to
another directory within the filesystem. Once the process’s root directory has been
changed once, it can only be made more restrictive. It is not possible to change the
process’s root directory to another directory outside of its current view of the filesystem.
Using chroot( ) is a simple way to increase security for processes that do not require
access to the filesystem outside of a directory or hierarchy of directories containing
its data files. If an attacker is somehow able to compromise the program and gain
68 | Chapter 2: Access Control
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