13. Permissions (part II), multifile C project
Permissions. Hard case
DAC (discrete access control): subject-subject model
Reprise: rwx*ugo
- Octal equivalent of attributes
- Directory permissions
x versus r
t-bit (octal?)
- SetUID/setGID
SetGID directory traversal (as seen on TCB)
- How i works
DAC (discrete access control) pitfalls
one type of mutlisubject (e. g. cannot separate groups RO, WO and no access in the same time)
Complexity of exceptional access control (e. g. restrict for one user)
Capabitities (see also insecure.ws docs
root is dangerous
- ⇒ many separate privilege escalations
flexible on execve()
example: ping
Other permission schemes:
Policy Kit: special library for authentificating queries from non-privileged prtocesses to privileged ones. Uses D-Bus.
Mandatory access control
MAC: (mandatory access control): subject-object model
- Table subjects×objects
→ $$\oo$$
- ⇒ almost any combination
- conmplex logic of inheritance
- e. g. windows
Table ACL
Rule-based ACL
Multifile C progect
TODO
H/W
TODO