Access Control Flashcards
What are the 3 fundamental categories of security techniques?
proactive, real-time, reactive
What 3 entities underlie the design of secure computer systems?
reference monitor, reference validation mechanism, trusted computing base
What are the principals of a reference monitor?
the users
what is a capability?
communicable, unforgeable token of authority
how do we enforce policies?
reference monitor implemented as controls
Where should you put access control mechanisms?
everywhere
what are the 3 reference monitor placement types?
stacked, sandbox, embedded
What is the stacked placement type? Give an example.
Where the RM is part of the interface between user space and OS.
example: all modern OS
What is the sandbox placement type? Give an example.
the program is executed in an RM-controlled environment.
example: interpreted language (Java)
What is the embedded placement type? Give an example.
the RM is a subcomponent of the program.
example: SQL engine
what are some reasons for a hardware-near security kernel?
- all mechanisms can be compromised from the layer below
- the lower the level, the harder to bypass
- the lower the level, the simpler the code
- hardware offers best performance for specialized checks
- higher level of assurance with smaller overhead
What are the 4 categories for requirements for OS security/
- execution domains
- process separation
- memory protection
- input/output controls
OS is both ___?___ and ___?___
arbitrator of access requests
object of access control
should users ever be able to modify the OS?
no
what is the classic distinction?
user mode vs supervisor mode
what are the principles of the multics protection rings?
each ring has access to itself, and all rings outside of itself, but no ring has access to rings inside itself. So ring 0 has access to everything.
what is TOCTOU?
Time-of-check time-of-use
What are the 2 steps to a TOCTOU attack?
- adversary prepares benign parameters and invokes the call gate
- while that call is processed, the adversary modifies parameters to something malicious
what are interrupts used for?
controlled invocation
what can be used to implement system calls?
software-invoked interrupts
What are 3 examples of malicious use of interrupt redirection?
keyboard logging, virus spreading, network manipulation
what is the memory hierarchy of modern computing systems?
logical memory, segmentation unit, linear memory, paging unit, physical memory
describe logical memory
environment of processes, is what assembler instructions refer to.
describe linear memory
flat addressing model, each byte is one address.
address span reflects register size.
