Security notes / Glossary: Difference between revisions

This is part of why functional accounts are often created for each such part: It's easier to handle this in broad terms even in simpler DAC setups, with just filesystem permissions.

When you want to crack down on this more thoroughly and more visibly, look at things like SELinux (because it adds MAC).

Note that the isolation in VMs and OS containers, are implicitly least-privilege as well: no connection to the outside unless permitted.

Discretionary Access Control (model)

Discretionary access control (DAC) means access to an object is at the discretion of the object's owner.

...more precisely, the identity of subjects.

Usually that's owner-based for practical reasons, though e.g. capability systems often allow transfer to other parts.

DAC is mainly contrasted with MAC

Examples:

permissions in most filesystems

Mandatory Access Control (model)

Mandatory access control (MAC) means that the system that decides to allow access between objects, instead of the object owners (though some systems apply MAC on top of DAC)

Often means a model applied on top, labeling all objects with particular categories, and having rules based on these categories.

Such (often-broad) labeling is often done for practical reasons: it often makes the rules simpler, which makes it more clear they express what you intended.

MAC usually means design up front. And each large change should probably re-evaluate all implications.

While MAC is good at partitioning off parts of a system in broad terms (e.g. "web server may only read under /var/www regardless of permissions"), it is much less flexible at anything you can't describe fully at the design stage (e.g. people wanting to share files somewhat securely).

This is one reason MAC often assists DAC, using MAC to restrict the broad problems, and DAC for the more everyday things. (While you can sort of implement something much like DAC using MAC, this is often so messy that it may be harder to verify as being correct, and harder to administer in an everyday way)

Role-Based Access Control

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Role-based access control (RBAC) is focused on roles and role hierarchy, subjects and sessions.

It's a moderately detailed abstraction, not yet a system in itself, but may be useful to architect into larger systems where you want to keep overview of what is allowed to happen and what is happening, particularly in larger organisations.

This makes it a potential piece of of DAC, MAC and others - probably replacing a simpler implementation of one of its parts (e.g. the role/account stuff).

https://en.wikipedia.org/wiki/Role-based_access_control

Attribute-based access control

Related notes

If you squint, there is sometimes very little difference between a MAC category and a DAC group (whatever the preferred terms are).

That is, very similar to useand users - the remaining difference may lie largely in who may change the permissions - the admin, or the relevant user.

This is also roughly why there is value in combining MAC and DAC.

Hacking terminology

Passive recon

Attack vector

Attack surface, Attack factor

Attack tree

Red Team

Network stuff

DMZ network

DMZ host

Bastion host

Unsorted

Forward and backward secrecy

Man in the middle

Two generals problem

The bitter ex test

Phishing

Worm, virus, trojan, etc.

Performative security, LARP security, pretend security, cargo cult security, security theater

End to end encryption

Zero knowledge

@@ Line 447: / Line 447: @@
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-Consider that people may record SSL sessions.
-In itself this gives them nothing but noise.
+Forward secrecy is a specific mitigation that can be designed into exchanges.
-But if your encrypted transfers always the same secret long-term secret key,
-then if you find that key twenty years later, ''all'' past exchanges are now immediately readable, and all future ones too.
-{{comment|(And long-term secrets are ''practical'', because as we all know (and all don't do nearly enough),
-you should verify secrets are tied to the identities we think. But identity and MiTM aside...)}}
-Now consider that it most uses of encryption, parties only care about the ability to understand each other during the short-term exchange.
-If you could, say, agree on a unique key for each session, and forget it immediately afterwards, this gives you some extra protection.
+Ask yourself how what happens when someone discovers a shared secret - how screwed are things now?
+(And long-term secrets are ''practical'', for humans to remember, but also technically for stable identities.)
-Finding a session's key does not give you the secret key (by merit of it not being the same thing), so does not
+For example, if an exchange uses a private key or password directly,
+then recording it and attacking it offline may eventually find that key or password.
-But more importantly, you can also build it in a way that even if you find the ''secret'' key,
-it does not help in finding individual session keys.
+If there is something like [[key derivation]] involved, then
+* even if you find that private key/password, it doesn't necessarily break sessions based on it
+* breaking a session doesn't necessarily reveal that private key/password
+Designs ''can'' aim for both of those because that's a good idea if you can,
+but forward secrecy is about the first of those.
@@ Line 486: / Line 481: @@
-Yeah, the names are not very intuitive, because both really talk about both directions in time.
+If you're thining '''the names are not very intuitive''', you are right,
+because both really talk about both directions in time.
 : Also, backwards secrecy is sometimes called "future secrecy" which... yeah.
 : Also, there is a difference between forward secrecy and ''perfect forward secrecy''
+Forward secrecy also has implications about how interesting it is to keep things for later.
+Say someone has recorded a secured exchange (e.g. an SSL/TLS session).
+In the moment, this is noise.
+But if your encrypted transfers always the same secret long-term secret key,
+then if you find that key twenty years later, ''all'' past exchanges are now immediately readable, and any future ones too.
+If you know that, fundamentally, the only thing that exchange can reveal is the contents of that exchange,
+and doesn't help towards any other exchanges, before or after, it becomes almost pointless to store this.
+This also implies a certain peace of mind -- if each message is its own island to break,
+then it is too expensive for someone to break all messages,
+and they probably won't store them,
+or they won't have much value in doing so.
+----
+Now consider that it most uses of encryption, parties only care about the ability to understand each other during the short-term exchange.
+If you could, say, agree on a unique key for each session , and forget it immediately afterwards, this gives you some extra protection.
+(and somehow do that secretly, probably using your shared secret)
+Finding a session's key does not give you the secret key (by merit of it not being the same thing), so does not
+But more importantly, you can also build it in a way that even if you find the ''secret'' key,
+it does not help in finding individual session keys.