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On 31/01/18 13:17, Martin Vaeth wrote: |
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> Nikos Chantziaras <realnc@×××××.com> wrote: |
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>> |
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>> Well, if you're running a local process that is trying to attack you, |
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>> you've been compromised already, imo. |
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> |
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> By your definition, you are compromised if you surf to the |
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> wrong webpage with enabled javascript. |
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That's not what was said. |
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What was said is that software that executes untrusted code inside a |
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trusted container is affected. You trust the container mechanism, you |
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don't trust the code executing inside of it. So the container needs to |
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be protected. |
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For example, if you don't trust Firefox, don't install Firefox. But you |
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*do* trust Firefox. What you don't trust is the JS code Firefox is |
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executing. So Firefox needs protection. |
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> You misunderstand: For the packages which run the code, the mitigations |
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> like retpoline do not help much. It is the packages which _somehow_ |
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> react (or can be called) by such a code which need the protection by |
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> retpoline built-in. |
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> And this is an awful lot of packages since it includes also all libraries |
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> which are possibly used by these packages, language interpreters used by |
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> these packages, etc. If in doubt, I would re-emerge the |
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> full -e @world with corresponding compiler switches enabled. |
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I was under the impression that it's the function that performs the call |
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that needs protection. The called function doesn't need protection, |
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because if it ends up being actually called, then it's too late already. |
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For example, if sandboxed, untrusted code wants to speculatively execute |
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a memcpy(), then the sandbox would need to call it on behalf of the |
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untrusted code. But if the sandbox is protected, the memcpy() call would |
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never be made speculatively, since retpoline will trap it. So memcpy() |
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itself doesn't need protection. If memcpy() ends up being called, then |
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it's too late. Protecting memcpy() doesn't do anything to prevent |
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memcpy() from being called, as it's been called already. |
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What am I missing here? :-P |
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