Now I'd like to have a link to that patch in code used by Apple that also appeared as a typo. Anybody remembers?
Xz: Can you spot the single character that disabled Linux landlock?
191–200 of 322 posts
Re: Xz: Can you spot the single character that disabled Linux landlock?
#192Earlier quoted context omitted.
Sure; but so long as the compiler error is silently discarded (as it is here), the configure script will assume landlock isn't available and never use it.
A misplaced punctuation has some plausible deniability. Like the author could say he was distracted and fat fingered nonsense, honest mistake. A utf character from a language that has zero chance of being mapped to your programmer's keyboard in the middle of a code line, that would be obvious intentional tampering or at the very least raise some eyebrows.
> A utf character from a language that has zero chance of being mapped to your programmer's keyboard in the middle of a code line, that would be obvious intentional tampering or at the very least raise some eyebrows.
I accidentally get Cyrillic "с" in my code few times a year. It's on the same key as Latin "c", so if I switch keyboard layout, I don't notice until the compiler warns me. Easy to do if I switch between chats and coding. Now my habit is to always type a few characters in addition to "c" to check what layout I'm _really_ using.
Granted, it's easier with a one-letter variable called "c", but with longer names I can easily see myself not typing "c" the first time (e.g. not pressing hard enough), starting build, chatting in some windows, getting back, facepalming, "fixing" the error by adding "c" or "с" depending on my keyboard layout.
Re: Xz: Can you spot the single character that disabled Linux landlock?
#193Earlier quoted context omitted.
He had unfettered access to xz’s git?
Isn’t it a bit ironic with how much code everyone depends on that can freely be altered by some unknown party, while so much time goes into code reviews to verify internal changes at most companies.
> while so much time goes into code reviews to verify internal changes at most companies
Very easy claim to make. Difficult to verify.
Re: Xz: Can you spot the single character that disabled Linux landlock?
#194Earlier quoted context omitted.
So that function checked if the following C code compiled, and only in that situation enabled the landlock? Except that lone period, hard to recognize because of its small size and proximity to the left edge of the diff, caused the C code to become always invalid, hence keeping the landlock always disabled? That's both vilely impressive and impressively vile. I didn't even spot it on my first read-through.
Even more evil would have been to replace this line (void)SYS_landlock_create_ruleset; with this: (void)SYS_landloсk_create_ruleset;
After the concept of such attacks had blow up idk. 1?2?3? years ago a lot of places now warn at least when mixing "languages"/ranges or sometimes on any usage of non us-ascii printable characters.
So stuff like that is increasingly more reliable caught.
Including by 3rd parties doing any ad-hoc scanning.
Through adding `compiles check` fail with syntax errors definitely should be added tot he list of auto scan checks, at least in C/C++ (it's not something you would do in most languages tbh. even in C it seems to be an antipatters).
Re: Xz: Can you spot the single character that disabled Linux landlock?
#195Earlier quoted context omitted.
Huh, the code with a dot is not legal C. It is CMake issue that the test breaks here.
That’s what makes this so clever: these systems were born in the era where you couldn’t trust anything - compilers sometimes emitted buggy code, operating systems would claim to be Unix but had weird inconsistencies on everything from system calls to command line tool arguments, etc. - so they just try to compile a test script and if it fails assume that the feature isn’t supported. This is extremely easy to miss sin…
You could just run tests for the feature detection on a known system or a dozen(VMs are cheap). The big problem is that most code is not tested at all or test errors are flat out ignored.
Re: Xz: Can you spot the single character that disabled Linux landlock?
#196Earlier quoted context omitted.
It may be hard for him to re-establish trust. Maintaining xz for more than a decade then doing this would be quite a "long con" but if HN threads are any indication, many will still be suspicious. His commits on these links look legit to me. It's a sad situation for him if he wasn't involved.
The fact GitHub suspended his account too suggests that they might have info saying he is involved.
Personally, I doubt that. I would assume that GitHub just banned all accounts that were directly associated with the project as a precaution.
Re: Xz: Can you spot the single character that disabled Linux landlock?
#197Earlier quoted context omitted.
A misplaced punctuation has some plausible deniability. Like the author could say he was distracted and fat fingered nonsense, honest mistake. A utf character from a language that has zero chance of being mapped to your programmer's keyboard in the middle of a code line, that would be obvious intentional tampering or at the very least raise some eyebrows.
> A utf character from a language that has zero chance of being mapped to your programmer's keyboard in the middle of a code line, that would be obvious intentional tampering or at the very least raise some eyebrows. I accidentally get Cyrillic "с" in my code few times a year. It's on the same key as Latin "c", so if I switch keyboard layout, I don't notice until the compiler warns me. Easy to do if I switch between…
even worse, I have Punto switcher that automatically switches language when I start typing. With default config, it changes latin c to russian one because russian language includes word "c" while it's non-sense in English.
and since it's the only Cyrillic character that's placed on the same key as the same-looking english character, I don't even see the problem with my eyes when the autoreplacement fires
Re: Xz: Can you spot the single character that disabled Linux landlock?
#198Earlier quoted context omitted.
So that function checked if the following C code compiled, and only in that situation enabled the landlock? Except that lone period, hard to recognize because of its small size and proximity to the left edge of the diff, caused the C code to become always invalid, hence keeping the landlock always disabled? That's both vilely impressive and impressively vile. I didn't even spot it on my first read-through.
It's also iffy tbh. that the compilation check functionality: - doesn't force users to differentiate between syntax errors and other errors (e.g. symbols not found). Partially you can't even make it work properly if you want due to C macros. - it seems sensible, tbh. if "does compile" checks for compatibility seems sensible then there is so much wrong with the ecosystem in so many ways
It's standard autoconf stuff, BUT... the right thing to do for a security option should be to throw an error at the configure stage If the Option is requested but can't be supported, And not to silently turn it off.
That is because a human should have to Look at the build and manually make the decision to switch off a security feature from the build.
Re: Xz: Can you spot the single character that disabled Linux landlock?
#199Earlier quoted context omitted.
Sure; but so long as the compiler error is silently discarded (as it is here), the configure script will assume landlock isn't available and never use it.
A misplaced punctuation has some plausible deniability. Like the author could say he was distracted and fat fingered nonsense, honest mistake. A utf character from a language that has zero chance of being mapped to your programmer's keyboard in the middle of a code line, that would be obvious intentional tampering or at the very least raise some eyebrows.
I mean, I agree that the punctuation mishap is a better cover story, but why would any particular language have “zero chance” of being mapped to the programmer’s keyboard?
Re: Xz: Can you spot the single character that disabled Linux landlock?
#200Earlier quoted context omitted.
Yeah, if anything, python worsens the situation. I had a friend DOS our server because he accidentally inserted a tab, causing the illusion that one statement was inside a block but was actually outside it. He swore off python at that point. I personally avoid the language, but I understand due to issues like that these days mixing tabs and spaces is an error (or is it just a warning?) by default. Regardless, still p…
white space as a delimiter is why i never use python.
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