Create temporary files securely

* A temporary file must have a unique, unpredictable name.
* The name must still be unique when the file is created.
* The file must be opened with exclusive access.
* The file must be opened with appropriate permissions.
* The file must have an unpredictable name.
* The file must be removed before the program exits.
https://www.securecoding.cert.org/confluence/display/seccode/VOID+FI039-C.+Create+temporary+files+securely