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> Its not like you can write JS code with this that runs on browsers that lets you leak arbitrary secrets That's precisely what Spectre and Meltdown were thoug

> Its not like you can write JS code with this that runs on browsers that lets you leak arbitrary secrets That's precisely what Spectre and Meltdown were though. It's unclear whether this attack would work in modern browsers but they did reenable SharedArrayBuffer & it's unclear if the existing mitigations for Spectre/Meltdown stimy this attack. > I personally disable all the mitigations because performance boost is actually noticeable. Congratulations, you are probably susceptible to JS code reading crypto keys on your machine.

nine_k 1y ago
Disabling some mitigations makes sense for an internal box that does not run arbitrary code from the internet, like a build server, or a load balancer, or maybe even a stateless API-serving box, as long as it's not a VM on a physical machine shared with other tenants.
- anyfoo 1y ago
  You run "arbitrary code from the internet" as soon as you use a web browser with JS enabled.
  - dwattttt 1y ago
    Or with JS disabled. HTML isn't as expressive, but it's still "arbitrary code from the internet"
    - anyfoo 1y ago
      There is a difference. JS is turing complete, pure HTML is far from (as far as I'm aware). So HTML might (!) well be restricted enough to not be able to carry out such an attack. But I'd never state to definitively, as I don't know enough about what HTML without JS can do these days. For all I know there's a turing tarpit in there somewhere...
      - nine_k 1y ago
        CSS3 is Turing-complete, but creating an exploit using just it would be... quite a feat. With JS or WASM, it's much more straightforward.
    - vlovich123 1y ago
      HTML doesn’t have the potential to deliver Spectre like attacks because: 1. No timers - timers are generally a required gadget & often they need to be hires or building a suitable timing gadget gets harder & your bandwidth of the attack goes down 2. No loops - you have to do timing stuff in a loop to exploit bugs in the predictor.
  - baobun 1y ago
    Which you wouldn't do on an internal load balancer or database server, right?
    - anyfoo 1y ago
      You are right, I sort of misread the statement I was replying to, but also wanted to reinforce that the large class of personal desktop machines is still very much affected, even if you "think" that you don't run "arbitrary code" on your machine. By the way, you have to be careful on your database server to not actually run arbitrary code as well. If your database supports stored procedures (think PL/SQL), that qualifies, if the clients that are able to create the stored procedures are not supposed to be able to access all data on that server anyway.
      - baobun 1y ago
        Oh yeah. Supply-chain risk is still a thing too and defense-in-depth is not a bad strategy. Physical isolation simplifies a lot of this. This class of attacks isn't (as) relevant for single-tenant single-workload dedicated machines.
        vlovich123 1y ago
        Based on this thread, I think people badly misjudge what “single-tenant” means in the context of susceptibility to exploits.
        baobun 1y ago
        Mind elaborating?
        vlovich123 1y ago
        Your “infrastructure” server could be a CI server - it’s just building “my” code ignoring that many (all?) build systems allow execution of arbitrary code as part of the build process (rust, cmake, bazel, JS ecosystem, Go, etc etc) and many involve 3p dependencies. And CI servers often handle secrets to infrastructure (publishing packages, etc). So you could end up allowing a supply chain attack that reads out various API keys & whatnot. In other words, properly drawing the boundary around “this is safe with meltdown disabled” is very hard, non-intuitive, and you’re one configuration/SW change or a violated assumption away from a Meltdown attack which is cross-process memory access & one notch below remote access. There’s a reason you design for security in depth rather than trying to carefully build a jenga tower where you’re one falling block away from total compromise.
  - nine_k 1y ago
    This is exactly what you won't do on most of your infrastructure boxes, would you? If you can reasonably trust all the software on the whole box, many mitigations that protect against effects of running adversary code on your machine become superfluous. OTOH if an adversary gets a low-privilege RCE on your box, exploiting something like Spectre or RowHammer could help elevate the privilege level, and more easily mount an attack on your other infrastructure.
    - anyfoo 1y ago
      Yeah, as stated in a sibling answer, I misread your comment a little bit. It's true, on at least some classes of infrastructure boxes, you more or less "own all that is on the machine" anyway. But also note my caveat about database servers, for example. A database server shared between accounts of different trust levels will be affected, if the database supports stored procedures for example. Basically, as soon as there's anything on the box that not all users of it should be able to access anyway, you'll have to be very, very careful.
      - vlovich123 1y ago
        While that’s an interesting idea, I’m not sure a side channel attack is actually exploitable by a stored procedure as I don’t believe it has enough gadgets.
        anyfoo 1y ago
        I don't know. PL/SQL (which is separate from SQL) is effectively a general purpose language, and kind of a beast at that. I have not the faintest idea, but at least I wouldn't be surprised to see high enough precision timers, and maybe it even getting JITted down into machine code for performance nowadays. (And I've read that tight loops can be used for timing in side channel attacks as well, although I assume it requires a lot more knowledge about the device you're running on.) A quick search reveals that there is at least a timer mechanism, but I have no idea of any of its properties: https://docs.oracle.com/en/database/oracle/oracle-database/19/sqpug/TIMING.html https://docs.oracle.com/en/database/oracle/oracle-database/1... But what I'm actually trying to say, is: For multiple intents and purposes (which might or might not include relevance to this specific vulnerability), as soon as you allow stored procedures in your database, "not running arbitrary code" is not a generally true statement instead.
gblargg 1y ago
Who these days would trust crypto keys on their machine, given the many hardware wallets available?
- vlovich123 1y ago
  Where do you think the crypto keys for the TLS connection securing your HTTPS browsing are stored? Although from what you said I’m now thinking you’re referring to cryptocurrency & thus aren’t on the same wavelength of the discussion here. Crypto keys —> cryptography keys, not cryptocurrency keys.
- ActorNightly 1y ago
  I think he means crypto as in like tokens, not wallet keys.
ActorNightly 1y ago
>Congratulations, you are probably susceptible to JS code reading crypto keys on your machine. No wonder you guys are scared AI is going to take your job lol. Thats not how it works at all. To grab a key stored in a JS variable, the following would need to happen 1. Attacker needs to find a way to inject arbitrary JS code in a website, which means controlling either an iframe that is loaded or some component. This is a pretty hard thing to do these days with Same-Site strictness 2. The code needs to know specifically what memory address to target. When things like JWT or other tokens are stored in session or local storage, the variable name usually contains a random string. Injected code will have to figure out a way to find what that variable name is. 3. For attack to work, the cache has to get evicted. This is highly processor specific on how well it works, and also, the web app has to be in a state where no other process is referencing that variable. With JS, you also have to infer memory layout (https://security.googleblog.com/2021/03/a-spectre-proof-of-concept-for-spectre.html https://security.googleblog.com/2021/03/a-spectre-proof-of-c...) first, which takes time. Then you have to train the branch predictor, which also takes time. So basically, I have a statistically higher chance of losing my keys to someone who physically robs me rather than a cache timing attack. Generally when an exploit like this drops, people always have failures to update their systems, and you see it being used in the wild. With Spectre/Meltdown, this didn't really happen, because of the nature of how these attacks work and the difficulty of getting the cache timing code to work correctly without specific targeting of a processor and ability to execute arbitrary code on the machine.
- anyfoo 1y ago
  This seems to theorize an attack where you are interested in particularly data of the particularly visited website, and at the same time assuming that the attack would have to be carried out on the same website. The vulnerability however allows arbitrary reading of any memory in the system in at least some circumstances, the presented PoC (https://www.youtube.com/watch?v=jrsOvaN7PaA https://www.youtube.com/watch?v=jrsOvaN7PaA ) demonstrates this by literally searching memory for the system's /etc/shadow and dumping that. Whether the attack is practical using JS instead of a compiled C program is unknown to me, but if it is, it's not clear to me why the attacker would need to inject JS code into other websites or know what addresses to target. (If it is not, the question is moot.)

nine_k 1y ago

Disabling some mitigations makes sense for an internal box that does not run arbitrary code from the internet, like a build server, or a load balancer, or maybe even a stateless API-serving box, as long as it's not a VM on a physical machine shared with other tenants.

anyfoo 1y ago
You run "arbitrary code from the internet" as soon as you use a web browser with JS enabled.
- dwattttt 1y ago
  Or with JS disabled. HTML isn't as expressive, but it's still "arbitrary code from the internet"
  - anyfoo 1y ago
    There is a difference. JS is turing complete, pure HTML is far from (as far as I'm aware). So HTML might (!) well be restricted enough to not be able to carry out such an attack. But I'd never state to definitively, as I don't know enough about what HTML without JS can do these days. For all I know there's a turing tarpit in there somewhere...
    - nine_k 1y ago
      CSS3 is Turing-complete, but creating an exploit using just it would be... quite a feat. With JS or WASM, it's much more straightforward.
  - vlovich123 1y ago
    HTML doesn’t have the potential to deliver Spectre like attacks because: 1. No timers - timers are generally a required gadget & often they need to be hires or building a suitable timing gadget gets harder & your bandwidth of the attack goes down 2. No loops - you have to do timing stuff in a loop to exploit bugs in the predictor.
- baobun 1y ago
  Which you wouldn't do on an internal load balancer or database server, right?
  - anyfoo 1y ago
    You are right, I sort of misread the statement I was replying to, but also wanted to reinforce that the large class of personal desktop machines is still very much affected, even if you "think" that you don't run "arbitrary code" on your machine. By the way, you have to be careful on your database server to not actually run arbitrary code as well. If your database supports stored procedures (think PL/SQL), that qualifies, if the clients that are able to create the stored procedures are not supposed to be able to access all data on that server anyway.
    - baobun 1y ago
      Oh yeah. Supply-chain risk is still a thing too and defense-in-depth is not a bad strategy. Physical isolation simplifies a lot of this. This class of attacks isn't (as) relevant for single-tenant single-workload dedicated machines.
      - vlovich123 1y ago
        Based on this thread, I think people badly misjudge what “single-tenant” means in the context of susceptibility to exploits.
        baobun 1y ago
        Mind elaborating?
        vlovich123 1y ago
        Your “infrastructure” server could be a CI server - it’s just building “my” code ignoring that many (all?) build systems allow execution of arbitrary code as part of the build process (rust, cmake, bazel, JS ecosystem, Go, etc etc) and many involve 3p dependencies. And CI servers often handle secrets to infrastructure (publishing packages, etc). So you could end up allowing a supply chain attack that reads out various API keys & whatnot. In other words, properly drawing the boundary around “this is safe with meltdown disabled” is very hard, non-intuitive, and you’re one configuration/SW change or a violated assumption away from a Meltdown attack which is cross-process memory access & one notch below remote access. There’s a reason you design for security in depth rather than trying to carefully build a jenga tower where you’re one falling block away from total compromise.
- nine_k 1y ago
  This is exactly what you won't do on most of your infrastructure boxes, would you? If you can reasonably trust all the software on the whole box, many mitigations that protect against effects of running adversary code on your machine become superfluous. OTOH if an adversary gets a low-privilege RCE on your box, exploiting something like Spectre or RowHammer could help elevate the privilege level, and more easily mount an attack on your other infrastructure.
  - anyfoo 1y ago
    Yeah, as stated in a sibling answer, I misread your comment a little bit. It's true, on at least some classes of infrastructure boxes, you more or less "own all that is on the machine" anyway. But also note my caveat about database servers, for example. A database server shared between accounts of different trust levels will be affected, if the database supports stored procedures for example. Basically, as soon as there's anything on the box that not all users of it should be able to access anyway, you'll have to be very, very careful.
    - vlovich123 1y ago
      While that’s an interesting idea, I’m not sure a side channel attack is actually exploitable by a stored procedure as I don’t believe it has enough gadgets.
      - anyfoo 1y ago
        I don't know. PL/SQL (which is separate from SQL) is effectively a general purpose language, and kind of a beast at that. I have not the faintest idea, but at least I wouldn't be surprised to see high enough precision timers, and maybe it even getting JITted down into machine code for performance nowadays. (And I've read that tight loops can be used for timing in side channel attacks as well, although I assume it requires a lot more knowledge about the device you're running on.) A quick search reveals that there is at least a timer mechanism, but I have no idea of any of its properties: https://docs.oracle.com/en/database/oracle/oracle-database/19/sqpug/TIMING.html https://docs.oracle.com/en/database/oracle/oracle-database/1... But what I'm actually trying to say, is: For multiple intents and purposes (which might or might not include relevance to this specific vulnerability), as soon as you allow stored procedures in your database, "not running arbitrary code" is not a generally true statement instead.

gblargg 1y ago

Who these days would trust crypto keys on their machine, given the many hardware wallets available?

vlovich123 1y ago
Where do you think the crypto keys for the TLS connection securing your HTTPS browsing are stored? Although from what you said I’m now thinking you’re referring to cryptocurrency & thus aren’t on the same wavelength of the discussion here. Crypto keys —> cryptography keys, not cryptocurrency keys.
ActorNightly 1y ago
I think he means crypto as in like tokens, not wallet keys.

ActorNightly 1y ago

>Congratulations, you are probably susceptible to JS code reading crypto keys on your machine. No wonder you guys are scared AI is going to take your job lol. Thats not how it works at all. To grab a key stored in a JS variable, the following would need to happen 1. Attacker needs to find a way to inject arbitrary JS code in a website, which means controlling either an iframe that is loaded or some component. This is a pretty hard thing to do these days with Same-Site strictness 2. The code needs to know specifically what memory address to target. When things like JWT or other tokens are stored in session or local storage, the variable name usually contains a random string. Injected code will have to figure out a way to find what that variable name is. 3. For attack to work, the cache has to get evicted. This is highly processor specific on how well it works, and also, the web app has to be in a state where no other process is referencing that variable. With JS, you also have to infer memory layout (https://security.googleblog.com/2021/03/a-spectre-proof-of-concept-for-spectre.html https://security.googleblog.com/2021/03/a-spectre-proof-of-c...) first, which takes time. Then you have to train the branch predictor, which also takes time. So basically, I have a statistically higher chance of losing my keys to someone who physically robs me rather than a cache timing attack. Generally when an exploit like this drops, people always have failures to update their systems, and you see it being used in the wild. With Spectre/Meltdown, this didn't really happen, because of the nature of how these attacks work and the difficulty of getting the cache timing code to work correctly without specific targeting of a processor and ability to execute arbitrary code on the machine.

anyfoo 1y ago
This seems to theorize an attack where you are interested in particularly data of the particularly visited website, and at the same time assuming that the attack would have to be carried out on the same website. The vulnerability however allows arbitrary reading of any memory in the system in at least some circumstances, the presented PoC (https://www.youtube.com/watch?v=jrsOvaN7PaA https://www.youtube.com/watch?v=jrsOvaN7PaA ) demonstrates this by literally searching memory for the system's /etc/shadow and dumping that. Whether the attack is practical using JS instead of a compiled C program is unknown to me, but if it is, it's not clear to me why the attacker would need to inject JS code into other websites or know what addresses to target. (If it is not, the question is moot.)