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ASLR is not purely security through obscurity because it is based on a solid security principle: increasing the difficulty of an attack by introducing randomnes

ASLR is not purely security through obscurity because it is based on a solid security principle: increasing the difficulty of an attack by introducing randomness. It doesn't solely rely on the secrecy of the implementation but rather the unpredictability of memory addresses. Think of it this way - if I guess the ASLR address once, a restart of the process renders that knowledge irrelevant implicitly. If I get your IPv6 address once, you’re going to have to redo your network topology to rotate your secret IP. That’s the distinction from ASLR.

fc417fc802 2y ago
I don't like that example because the damaged cause by and the difficulty of recovering from a secret leaking is not what determines the classification. There exist keys that if leaked would be very time consuming to recover from. That doesn't make them security by obscurity. I think the key feature of the IPv6 address example is that you need to expose the address in order to communicate. The entire security model relies on the attacker not having observed legitimate communications. As soon as an attacker witnesses your system operating as intended the entire thing falls apart. Another way to phrase it is that the security depends on the secrecy of the implementation, as opposed to the secrecy of one or more inputs.
- vlovich123 2y ago
  You don’t necessarily need to expose the IPv6 address to untrusted parties though in which case it is indeed quite similar to ASLR in that data leakage of some kind is necessary. I think the main distinguishing factor is that ASLR by design treats the base address as a secret and guards it as such whereas that’s not a mode the IPv6 address can have because by its nature it’s assumed to be something public.
  - fc417fc802 2y ago
    Huh. The IPv6 example is much more confusing that I initially thought. At this point I am entirely unclear as to whether it is actually an example of security through obscurity, regardless of whatever else it might be (a very bad idea to rely on it for one). Rather ironic given that the poster whose claims I was disputing provided it as an example of something that would be universally recognized as such.
    - vlovich123 2y ago
      I think it’s security through obscurity because in ASLR the randomized base address is a protected secret key material whereas in the ipv6 case it’s unprotected key material (eg every hop between two communicating parties sees the secret). It’s close though which is why IPv6 mapping efforts are much more heuristics based than ipv4 which you can just brute force (along with port #) quickly these days.
      - fc417fc802 2y ago
        I'm finding this semantic rabbit hole surprisingly amusing. The problem with that line of reasoning is that it implies that data handling practices can determine whether or not a given scheme is security through obscurity. But that doesn't fit the prototypical example where someone uses a super secret and utterly broken home rolled "encryption" algorithm. Nor does it fit the example of someone being careless with the key material for a well established algorithm. The key defining characteristic of that example is that the security hinges on the secrecy of the blueprints themselves. I think a case can also be made for a slightly more literal interpretation of the term where security depends on part of the design being different from the mainstream. For example running a niche OS making your systems less statistically likely to be targeted in the first place. In that case the secrecy of the blueprints no longer matters - it's the societal scale analogue of the former example. I think the IPv6 example hinges on the semantic question of whether a network address is considered part of the blueprint or part of the input. In the ASLR analogue, the corresponding question is whether a function pointer is part of the blueprint or part of the input.
        vlovich123 2y ago
        > The problem with that line of reasoning is that it implies that data handling practices can determine whether or not a given scheme is security through obscurity Necessary but not sufficient condition. For example, if I’m transmitting secrets across the wire in plain text that’s clearly security through obscurity even if you’re relying on an otherwise secure algorithm. Security is a holistic practice and you can’t ignore secrets management separate from the algorithm blueprint (which itself is also a necessary but not sufficient condition).
ryao 2y ago
If someone can guess the randomization within 1 second using the AnC attack, you can restart as much as you want, but it will not improve security.

fc417fc802 2y ago

I don't like that example because the damaged cause by and the difficulty of recovering from a secret leaking is not what determines the classification. There exist keys that if leaked would be very time consuming to recover from. That doesn't make them security by obscurity. I think the key feature of the IPv6 address example is that you need to expose the address in order to communicate. The entire security model relies on the attacker not having observed legitimate communications. As soon as an attacker witnesses your system operating as intended the entire thing falls apart. Another way to phrase it is that the security depends on the secrecy of the implementation, as opposed to the secrecy of one or more inputs.

vlovich123 2y ago
You don’t necessarily need to expose the IPv6 address to untrusted parties though in which case it is indeed quite similar to ASLR in that data leakage of some kind is necessary. I think the main distinguishing factor is that ASLR by design treats the base address as a secret and guards it as such whereas that’s not a mode the IPv6 address can have because by its nature it’s assumed to be something public.
- fc417fc802 2y ago
  Huh. The IPv6 example is much more confusing that I initially thought. At this point I am entirely unclear as to whether it is actually an example of security through obscurity, regardless of whatever else it might be (a very bad idea to rely on it for one). Rather ironic given that the poster whose claims I was disputing provided it as an example of something that would be universally recognized as such.
  - vlovich123 2y ago
    I think it’s security through obscurity because in ASLR the randomized base address is a protected secret key material whereas in the ipv6 case it’s unprotected key material (eg every hop between two communicating parties sees the secret). It’s close though which is why IPv6 mapping efforts are much more heuristics based than ipv4 which you can just brute force (along with port #) quickly these days.
    - fc417fc802 2y ago
      I'm finding this semantic rabbit hole surprisingly amusing. The problem with that line of reasoning is that it implies that data handling practices can determine whether or not a given scheme is security through obscurity. But that doesn't fit the prototypical example where someone uses a super secret and utterly broken home rolled "encryption" algorithm. Nor does it fit the example of someone being careless with the key material for a well established algorithm. The key defining characteristic of that example is that the security hinges on the secrecy of the blueprints themselves. I think a case can also be made for a slightly more literal interpretation of the term where security depends on part of the design being different from the mainstream. For example running a niche OS making your systems less statistically likely to be targeted in the first place. In that case the secrecy of the blueprints no longer matters - it's the societal scale analogue of the former example. I think the IPv6 example hinges on the semantic question of whether a network address is considered part of the blueprint or part of the input. In the ASLR analogue, the corresponding question is whether a function pointer is part of the blueprint or part of the input.
      - vlovich123 2y ago
        > The problem with that line of reasoning is that it implies that data handling practices can determine whether or not a given scheme is security through obscurity Necessary but not sufficient condition. For example, if I’m transmitting secrets across the wire in plain text that’s clearly security through obscurity even if you’re relying on an otherwise secure algorithm. Security is a holistic practice and you can’t ignore secrets management separate from the algorithm blueprint (which itself is also a necessary but not sufficient condition).

ryao 2y ago

If someone can guess the randomization within 1 second using the AnC attack, you can restart as much as you want, but it will not improve security.