I’ve seen a few comments on the interwebs that “even a [good/half decent/other adjatiave] static analysis tool would have caught this”. I’ll note that infer, one of the best open source tools out there, does not catch this. It’s an ugly bit of code that discourages human readers and analysis tools - not surprising it lived for a long while.
Hello, I am here to derail the Rust discussion before it gets started. The culprit behind sudo’s vast repertoire of vulnerabilities, and more broadly of bugs in general, is accountable almost entirely to one matter: its runaway complexity.
We have another tool which does something very similar to sudo which we can compare with: doas. The portable version clocks in at about 500 lines of code, its man pages are a combined 157 lines long, and it has had two CVEs (only one of which Rust would have prevented), or approximately one every 30 months.
sudo is about 120,000 lines of code (100x more), its had 140 CVEs, or about one every 2 months since the CVE database came into being 21 years ago. Its man pages are about 10,000 lines and include the following:
$ man sudoers | grep -C1 despair
The sudoers file grammar will be described below in Extended Backus-Naur
Form (EBNF). Don't despair if you are unfamiliar with EBNF; it is fairly
simple, and the definitions below are annotated.
If you want programs to be more secure, stable, and reliable, the key metric to address is complexity. Rewriting it in Rust is not the main concern.
Did you even look at that list? Most of those are not sudo vulnerabilities but issues in sudo configurations distros ship with. The actual list is more like 39, and a number of them are “disputed” and most are low-impact. I didn’t do a full detailed analysis of the issues, but the implication that it’s had “140 security problems” is simply false.
sudo is about 120,000 lines of code
More like 60k if you exclude the regress (tests) and lib directories, and 15k if you exclude the plugins (although the sudoers plugin is 40k lines, which most people use). Either way, it’s at least half of 120k.
Its man pages are about 10,000 lines and include the following:
12k, but this also includes various technical documentation (like the plugin API); the main documentation in sudoers(1) is 741 lines, and sudoers(5) is 3,255 lines. Well under half of 10,000.
We have another tool which does something very similar to sudo which we can compare with: doas.
Except that it only has 10% of the features, or less. This is good if you don’t use them, and bad if you do. But I already commented on this at HN so no need to repeat that here.
You’re right about these numbers being a back-of-the-napkin analysis. But even your more detailed analysis shows that the situation is much graver with sudo. I am going to include plugins, becuase if they ship, they’re a liability. And their docs, because they felt the need to write them. You can’t just shove the complexity you don’t use and/or like under the rug. Heartbleed brought the internet to its knees because of a vulnerability in a feature no one uses.
And yes, doas has 10% of the features by count - but it has 99% of the features by utility. If you need something in the 1%, what right do you have to shove it into my system? Go make your own tool! Your little feature which is incredibly useful to you is incredibly non-useful to everyone else, which means fewer eyes on it, and it’s a security liability to 99% of systems as such. Not every feature idea is meritous. Scope management is important.
what right do you have to shove it into my system?
Nobody is shoving anything into your system. The sudo maintainers have the right to decide to include features, and they’ve been exercising that right. You have the right to skip sudo and write your own - and you’ve been exercising that right too.
Go make your own tool!
You’re asking people to undergo the burden of forking or re-writing all of the common functionality of an existing tool just so they can add their one feature. This imposes a great cost on them. Meanwhile, including that code or feature into an existing tool imposes only a small (or much smaller) cost, if done correctly - the incremental cost of adding a new feature to an existing system.
The key phrase here is “if done correctly”. The consensus seems to be that sudo is suffering from poor engineering practices - few or no tests, including with the patch that (ostensibly) fixes this bug. If your software engineering practices are bad, then simpler programs will have fewer bugs only because there’s less code to have bugs in. This is not a virtue. Large, complex programs can be built to be (relatively) safe by employing tests, memory checkers, good design practices, good architecture (which also reduces accidental complexity) code reviews, and technologies that help mitigate errors (whether that be a memory-safe GC-less language like Rust or a memory-safe GC’ed language like Python). Most features can (and should) be partitioned off from the rest of the design, either through compile-time flags or runtime architecture, which prevents them from incurring security or performance penalties.
Software is meant to serve the needs of users. Users have varied use-cases. Distinct use-cases require more code to implement, and thereby incur complexity (although, depending on how good of an engineer one is, additional accidental complexity above the base essential complexity may be added). If you want to serve the majority of your users, you must incur some complexity. If you want to still serve them, then start by removing the accidental complexity. If you want to remove the essential complexity, then you are no longer serving your users.
The sudo project is probably designed to serve the needs of the vast majority of the Linux user-base, and it succeeds at that, for the most part. doas very intentionally does not serve the needs of the vast majority of the linux user-base. Don’t condemn a project for trying to serve more users than you are.
Heartbleed brought the internet to its knees because of a vulnerability in a feature no one uses.
Yes, but the difference is that these are features people actually use, which wasn’t the case with Heartleed. Like I mentioned, I think doas is great – I’ve been using it for years and never really used (or liked) sudo because I felt it was far too complex for my needs, before doas I just used su. But I can’t deny that for a lot of other people (mainly organisations, which is the biggest use-case for sudo in the first place) these features are actually useful.
Go make your own tool! Your little feature which is incredibly useful to you is incredibly non-useful to everyone else
A lot of these things aren’t “little” features, and many interact with other features. What if I want doas + 3 flags from sudo + LDAP + auditing? There are many combinations possible, and writing a separate tool for every one of them isn’t really realistic, and all of this also required maintenance and reliable consistent long-term maintainers are kind of rare.
Scope management is important.
Yes, I’m usually pretty explicit about which use cases I want to solve and which I don’t want to solve. But “solving all the use cases” is also a valid scope. Is this a trade-off? Sure. But everything here is.
The real problem isn’t so much sudo; but rather that sudo is the de-facto default in almost all Linux distros (often installed by default, too). Ideally, the default should be the simplest tool which solves most of the common use cases (i.e. doas), and people with more complex use cases can install sudo if they need it. I don’t know why there aren’t more distros using doas by default (probably just inertia?)
What if I want doas + 3 flags from sudo + LDAP + auditing?
Tough shit? I want a pony, and a tuba, and barbie doll…
But “solving all the use cases” is also a valid scope.
My entire thesis is that it’s not a valid scope. This fallacy leads to severe and present problems like the one we’re discussing today. You’re begging the question here.
Tough shit? I want a pony, and a tuba, and barbie doll…
This is an extremely user-hostile attitude to have (and don’t try claiming that telling users with not-even-very-obscure use-cases to write their own tools isn’t user-hostile).
I’ve noticed that some programmers are engineers that try to build tools to solve problems for users, and some are artists that build programs that are beautiful or clever, or just because they can. You appear to be one of the latter, with your goal being crafting simple, beautiful systems. This is fine. However, this is not the mindset that allows you to build either successful systems (in a marketshare sense) or ones that are useful for many people other than yourself, for previously-discussed reasons. The sudo maintainers are trying to build software for people to use. Sure, there’s more than one way to do that (integration vs composition), but there are ways to do both poorly, and claiming the moral high ground for choosing simplicity (composition) is not only poor form but also kind of bad optics when you haven’t even begun to demonstrate that it’s a better design strategy.
My entire thesis is that it’s not a valid scope.
A thesis which you have not adequately defended. Your statements have amounted to “This bug is due to sudo’s complexity which is driven by the target scope/number of features that it has”, while both failing to provide any substantial evidence that this is the case (e.g. showing that sudo’s bugs are due to feature-driven essential complexity alone, and not use of a memory-unsafe language, poor software engineering practices (which could lead to either accidental complexity or directly to bugs themselves), or simple chance/statistics) and not actually providing any defense for the thesis as stated. Assume that @arp242 didn’t mean “all” the usecases, but instead “the vast majority” of them - say, enough that it works for 99.9% of users. Why is this “invalid”, exactly? It’s easy for me to imagine the argument being “this is a bad idea”, but I can’t imagine why you would think that it’s logically incoherent.
Finally, you have repeatedly conflated “complexity” and “features”. Your entire argument is, again, invalid if you can’t show that sudo’s complexity is purely (or even mostly) essential complexity, as opposed to accidental complexity coming from being careless etc.
I dont’t think “users (distros) make a lot of configuration mistakes” is a good defence when arguing if complexity is the issue.
But I do agree about feature set. And I feel like arguing against complexity for safety is wrong (like ddevault was doing), because systems inevitably grow complex. We should still be able to build safe, complex systems. (Hence why I’m a proponent of language innovation and ditching C.)
I dont’t think “users (distros) make a lot of configuration mistakes” is a good defence when arguing if complexity is the issue.
It’s silly stuff like (ALL : ALL) NOPASSWD: ALL. “Can run sudo without a password” seems like a common theme: some shell injection is found in the web UI and because the config is really naïve (which is definitely not the sudo default) it’s escalated to root.
Others aren’t directly related to sudo configuration as such; for example this one has a Perl script which is run with sudo that can be exploited to run arbitrary shell commands. This is also a common theme: some script is run with sudo, but the script has some vulnerability and is now escalated to root as it’s run with sudo.
I didn’t check all of the issues, but almost all that I checked are one of the above; I don’t really see any where the vulnerability is caused directly by the complexity of sudo or its configuration; it’s just that running anything as root is tricky: setuid returns 432 results, three times that of sudo, and I don’t think that anyone can argue that setuid is complex or that setuid implementations have been riddled with security bugs.
Other just mention sudo in passing by the way; this one is really about an unrelated remote exec vulnerability, and just mentions “If QCMAP_CLI can be run via sudo or setuid, this also allows elevating privileges to root”. And this one isn’t even about sudo at all, but about a “sudo mode” plugin for TYPO3, presumably to allow TYPO3 users some admin capabilities without giving away the admin password. And who knows why this one is even returned in a search for “sudo” as it’s not mentioned anywhere.
it’s just that running anything as root is tricky: setuid returns 432 results, three times that of sudo
This is comparing apples to oranges. setuid affects many programs, so obviously it would have more results than a single program would. If you’re going to attack my numbers than at least run the same logic over your own.
Well, whatever we’re comparing, it’s not making much sense.
If sudo is hard to use and that leads to security problems through its misusage, that’s sudo’s fault. Or do you think that the footguns in C are not C’s fault, either? I thought you liked Rust for that very reason. For this reason the original CVE count stands.
But fine, let’s move on on the presumption that the original CVE count is not appropriate to use here, and instead reference your list of 39 Ubuntu vulnerabilities. 39 > 2, Q.E.D. At this point we are comparing programs to programs.
You now want to compare this with 432 setuid results. You are comparing programs with APIs. Apples to oranges.
But, if you’re trying to bring this back and compare it with my 140 CVE number, it’s still pretty damning for sudo. setuid is an essential and basic feature of Unix, which cannot be made any smaller than it already is without sacrificing its essential nature. It’s required for thousands of programs to carry out their basic premise, including both sudo and doas! sudo, on the other hand, can be made much simpler and still address its most common use-cases, as demonstrated by doas’s evident utility. It also has a much smaller exposure: one non-standard tool written in the 80’s and shunted along the timeline of Unix history every since, compared to a standardized Unix feature introduced by DMR himself in the early 70’s. And setuid somehow has only 4x the number of footgun incidents? sudo could do a hell of a lot better, and it can do so by trimming the fat - a lot of it.
If sudo is hard to use and that leads to security problems through its misusage, that’s sudo’s fault.
It’s not because it’s hard to use, it’s just that its usage can escalate other more (relatively) benign security problems, just like setuid can. This is my point, as a reply to stephank’s comment. This is inherent to running anything as root, with setuid, sudo, or doas, and why we have capabilities on Linux now. I bet that if doas would be the default instead of sudo we’d have a bunch of CVEs about improper doas usage now, because people do stupid things like allowing anyone to run anything without password and then write a shitty web UI in front of that. That particular problem is not doas’s (or sudo’s) fault, just as cutting myself with the kitchen knife isn’t the knife’s fault.
reference your list of 39 Ubuntu vulnerabilities. 39 > 2, Q.E.D.
Yes, sudo has had more issues in total; I never said it doesn’t. It’s just a lot lower than what you said, and quite a number are very low-impact, so I just disputed the implication that sudo is a security nightmare waiting to happen: it’s track record isn’t all that bad. As always, more features come with more (security) bugs, but use cases do need solving somehow. As I mentioned, it’s a trade-off.
sudo, on the other hand, can be made much simpler and still address its most common use-cases, as demonstrated by doas’s evident utility
We already agreed on this yesterday on HN, which I repeated here as well; all I’m adding is “but sudo is still useful, as it solves many more use cases” and “sudo isn’t that bad”.
Interesting thing to note: sudo was removed from OpenBSD by millert@openbsd.org; who is also the sudo maintainer. I think he’ll agree that “sudo is too complex for it to the default”, which we already agree on, but not that sudo is “too complex to exist”, which is where we don’t agree.
Could sudo be simpler or better architectured to contain its complexity? Maybe. I haven’t looked at the source or use cases in-depth, and I’m not really qualified to make this judgement.
I think arguing against complexity is one of the core principles of UNIX philosophy, and it’s gotten us quite far on the operating system front.
If simplicity was used in sudo, this particular vulnerability would not have been possible to trigger it: why have sudoedit in the first place, which just implies the -e flag? This statement is a guarantee.
If it would’ve ditched C, there is no guarantee that this issue wouldn’t have happened.
There can be logic bugs in basically any language, of course. However, the following classes of bugs tend to be steps in major exploits:
Bounds checking issues on arrays
Messing around with C strings at an extremely low level
It is hard to deny that, in a universe where nobody ever messed up those two points, there are a lot less nasty exploits in the world in systems software in particular.
Many other toolchains have decided to make the above two issues almost non-existent through various techniques. A bunch of old C code doesn’t handle this. Is there not something that can be done here to get the same productivity and safety advantages found in almost every other toolchain for tools that form the foundation of operating computers? Including a new C standard or something?
I can have a bunch of spaghetti code in Python, but turning that spaghetti into “oh wow argv contents ran over some other variables and messed up the internal state machine” is a uniquely C problem, but if everyone else can find solutions, I feel like C could as well (including introducing new mechanisms to the language. We are not bound by what is printed in some 40-year-old books, and #ifdef is a thing).
EDIT: forgot to mention this, I do think that sudo is a bit special given that its default job is to take argv contents and run them. I kinda agree that sudo is a bit special in terms of exploitability. But hey, the logic bugs by themselves weren’t enough to trigger the bug. When you have a multi-step exploit, anything on the path getting stopped is sufficient, right?
+1. Lost in the noise of “but not all CVEs…” is the simple fact that this CVE comes from an embarrassing C string fuckup that would be impossible, or at least caught by static analysis, or at very least caught at runtime, in most other languages. If “RWIIR” is flame bait, then how about “RWIIP” or at least “RWIIC++”?
Probably Python, given the content of the comment by @rtpg. Python is also memory-safe, while it’s unclear to me whether Pascal is (a quick search reveals that at least FreePascal is not memory-safe).
Were it not for the relative (accidental, non-feature-providing) complexity of Python to C, I would support RWIIP. Perhaps Lua would be a better choice - it has a tiny memory and disk footprint while also being memory-safe.
Probably Python, given the content of the comment by @rtpg. Python is
also memory-safe, while it’s unclear to me whether Pascal is (a quick
search reveals that at least FreePascal is not memory-safe).
That’s possibly it.
Perhaps Lua would be a better choice - it has a tiny memory and disk
footprint while also being memory-safe.
Not to mention that Lua – even when used without LuaJIT – is simply
blazingly fast compared to other scripting languages (Python, Perl, &c)!
For instance, see this benchmark I did sometime ago:
https://0x0.st/--3s.txt. I had implemented Ackermann’s function in
various languages (the “./ack” file is the one in C) to get a rough idea
on their execution speed, and lo and behold Lua turned out to be second
only to the C implementation.
I agree that rewriting things in Rust is not always the answer, and I also agree that simpler software makes for more secure software. However, I think it is disingenuous to compare the overall CVE count for the two programs. Would you agree that sudo is much more widely installed than doas (and therefore is a larger target for security researchers)? Additionally, most of the 140 CVEs linked were filed before October 2015, which is when doas was released. Finally, some of the linked CVEs aren’t even related to code vulnerabilities in sudo, such as the six Quest DR Series Disk Backup CVEs (example).
I would agree that sudo has a bigger target painted on its back, but it’s also important to acknowledge that it has a much bigger back - 100× bigger. However, I think the comparison is fair. doas is the default in OpenBSD and very common in NetBSD and FreeBSD systems as well, which are at the heart of a lot of high-value operations. I think it’s over the threshold where we can consider it a high-value target for exploitation. We can also consider the kinds of vulnerabilities which have occured internally within each project, without comparing their quantity to one another, to characterize the sorts of vulnerabilities which are common to each project, and ascertain something interesting while still accounting for differences in prominence. Finally, there’s also a bias in the other direction: doas is a much simpler tool, shipped by a team famed for its security prowess. Might this not dissuade it as a target for security researchers just as much?
Bonus: if for some reason we believed that doas was likely to be vulnerable, we could conduct a thorough audit on its 500-some lines of code in an hour or two. What would the same process look like for sudo?
Another missing point is that Rust is only one of many memory safe languages. Sudo doesn’t need to be particularly performant or free of garbage collection pauses. It could be written in your favorite GCed language like Go, Java, Scheme, Haskell, etc. Literally any memory safe language would be better than C for something security-critical like sudo, whether we are trying to build a featureful complex version like sudo or a simpler one like doas.
I’m not a security expert, so I’m be happy to be corrected, but if I remember correctly, using secrets safely in a garbage collected language is not trivial. Once you’ve finished working with some secret, you don’t necessarily know how long it will remain in memory before it’s garbage collected, or whether it will be securely deleted or just ‘deallocated’ and left in RAM for the next program to read. There are ways around this, such as falling back to manual memory control for sensitive data, but as I say, it’s not trivial.
That is true, but you could also do the secrets handling in a small library written in C or Rust and FFI with that, while the rest of your bog-standard logic not beholden to the issues that habitually plague every non-trivial C codebase.
Besides these capabilities, ideally a language would also have ways of expressing important security properties of code. For example, ways to specify that a certain piece of data is secret and ensure that it can’t escape and is properly overwritten when going out of scope instead of simply being dropped, and ways to specify a requirement for certain code to use constant time to prevent timing side channels. Some languages are starting to include things like these.
Meanwhile when you try to write code with these invariants in, say, C, the compiler might optimize these desired constraints away (overwriting secrets is a dead store that can be eliminated, the password checker can abort early when the Nth character of the hash is wrong, etc) because there is no way to actually express those invariants in the language. So I understand that some of these security-critical things are written in inline assembly to prevent these problems.
It looks like it was added to glibc in 2017. I’m not sure if I haven’t looked at this since then, if the resources I was reading were just not up to date, or if I just forgot about this function.
I do think high complexity is the source of many problems in sudo and that doas is a great alternative to avoid many of those issues.
I also think sudo will continue being used by many people regardless. If somebody is willing to write an implementation in Rust which might be just as complex but ensures some level of safety, I don’t see why that wouldn’t be an appropriate solution to reducing the attack surface. I certainly don’t see why we should avoid discussing Rust just because an alternative to sudo exists.
Talking about Rust as an alternative is missing the forest for the memes. Rust is a viral language (in the sense of internet virality), and a brain worm that makes us all want to talk about it. But in actual fact, C is not the main reason why anything is broken - complexity is. We could get much more robust and reliable software if we focused on complexity, but instead everyone wants to talk about fucking Rust. Rust has its own share of problems, chief among them its astronomical complexity. Rust is not a moral imperative, and not even the best way of solving these problems, but it does have a viral meme status which means that anyone who sees through its bullshit has to proactively fend off the mob.
I don’t understand why you hate Rust so much but it seems as irrational as people’s love for it.
Rust’s main value proposition is that it allows you to write more complex software that has fewer bugs, and your point is that this is irrelevant because the software should just be less complex. Well I have news for you, software is not going to lose any of its complexity. That’s because we want software to do stuff, the less stuff it does the less useful it becomes, or you have to replace one tool with two tools. The ecosystem hasn’t actually become less complex when you do that, you’re just dividing the code base into two chunks that don’t really do what you want.
I don’t know why you hate Rust so much to warrant posting anywhere the discussion might come up, but I would suggest if you truly cannot stand it that you use some of your non-complex software to filter out related keywords in your web browser.
Agree with what you’ve wrote, but just to pick at a theme that’s bothering me on this thread…
I don’t understand why you hate Rust so much but it seems as irrational as people’s love for it.
This is obviously very subjective, and everything below is anecdotal, but I don’t agree with this equivalence.
In my own experience, everyone I’ve met who “loves” or is at least excited about rust seems to feel so for pretty rational reasons: they find the tech interesting (borrow checking, safety, ML-inspired type system), or they enjoy the community (excellent documentation, lots of development, lots of online community). Or maybe it’s their first foray into open source, and they find that gratifying for a number of reasons. I’ve learned from some of these people, and appreciate the passion for what they’re doing. Not to say they don’t exist, but I haven’t really seen anyone “irrationally” enjoy rust - what would that mean? I’ve seen floating around a certain spiteful narrative of the rust developer as some sort of zealous online persona that engages in magical thinking around the things rust can do for them, but I haven’t really seen this type of less-than-critical advocacy any more for rust than I have seen for other technologies.
On the other hand I’ve definitely seen solid critiques of rust in terms of certain algorithms being tricky to express within the constraints of the borrow checker, and I’ve also seen solid pushback against some of the guarantees that didn’t hold up in specific cases, and to me that all obviously falls well within the bounds of “rational”. But I do see a fair amount of emotionally charged language leveled against not just rust (i.e. “bullshit” above) but the rust community as well (“the mob”), and I don’t understand what that’s aiming to accomplish.
I agree with you, and I apologize if it came across that I think rust lovers are irrational - I for one am a huge rust proselytizer. I intended for the irrationality I mentioned to be the perceived irrationality DD attributes to the rust community
Definitely no apology needed, and to be clear I think the rust bashing was coming from elsewhere, I just felt like calling it to light on a less charged comment.
I think the criticism isn’t so much that people are irrational in their fondness of Rust, but rather that there are some people who are overly zealous in their proselytizing, as well as a certain disdain for everyone who is not yet using Rust.
Here’s an example comment from the HN thread on this:
Another question is who wants to maintain four decades old GNU C soup? It was written at a different time, with different best practices.
In some point someone will rewrite all GNU/UNIX user land in modern Rust or similar and save the day. Until this happens these kind of incidents will happen yearly.
There are a lot of things to say about this comment, and it’s entirely false IMO, but it’s not exactly a nice comment, and why Rust? Why not Go? Or Python? Or Zig? Or something else.
Here’s another one:
Rust is modernized C. You are looking for something that already exists. If C programmers would be looking for tools to help catch bugs like this and a better culture of testing and accountability they would be using Rust.
The disdain is palatable in this one, and “Rust is modernized C” really misses the mark IMO; Rust has a vastly different approach. You can consider this a good or bad thing, but it’s really not the only approach towards memory-safe programming languages.
Of course this is not representative for the entire community; there are plenty of Rust people that I like and have considerably more nuanced views – which are also expressed in that HN thread – but these comments certainly are frequent enough to give a somewhat unpleasant taste.
While I don’t approve of the deliberately inflammatory form of the comments, and don’t agree with the general statement that all complexity is eliminateable, I personally agree that, in this particular case, simplicity > Rust.
As a thought experiment, world 1 uses sudo-rs as a default implementation of sudo, while world 2 uses 500 lines of C which is doas. I do think that world 2 would be generally more secure. Sure, it’ll have more segfaults, but fewer logical bugs.
I also think that the vast majority of world 2 populace wouldn’t notice the absence of advanced sudo features. To be clear, the small fraction that needs those features would have to install sudo, and they’ll use the less tested implementation, so they will be less secure. But that would be more than offset by improved security of all the rest.
Adding a feature to a program always has a cost for those who don’t use this feature. If the feature is obscure, it might be overall more beneficial to have a simple version which is used by the 90% of the people, and a complex for the rest 10%. The 10% would be significantly worse off in comparison to the unified program. The 90% would be slightly better off. But 90% >> 10%.
Rust’s main value proposition is that it allows you to write more complex software that has fewer bugs
I argue that it’s actually that it allows you to write fast software with fewer bugs. I’m not entirely convinced that Rust allows you to manage complexity better than, say, Common Lisp.
That’s because we want software to do stuff, the less stuff it does the less useful it becomes
Exactly. Software is written for people to use. (technically, only some software - other software (such as demoscenes) is written for the beauty of it, or the enjoyment of the programmer; but in this discussion we only care about the former)
The ecosystem hasn’t actually become less complex when you do that
Even worse - it becomes more complex. Now that you have two tools, you have two userbases, two websites, two source repositories, two APIs, two sets of file formats, two packages, and more. If the designs of the tools begin to differ substantially, you have significantly more ecosystem complexity.
You’re right about Rust value proposition, I should have added performance to that sentence. Or, I should have just said managed language, because as another commenter pointed out Rust is almost irrelevant to this whole conversation when it comes to preventing these type of CVEs
The other issue is that it is a huge violation of principle of least privilege. Those other features are fine, but do they really need to be running as root?
Plugins, integrated log server, TLS support… none of that are things I’d want in a tool that should be simple and is installed as suid root.
(Though I don’t think complexity vs. memory safety are necessarily opposed solutions. You could easily imagine a sudo-alike too that is written in rust and does not come with unnecessary complexity.)
There’s nothing wrong with EBNF, but there is something wrong with relying on it to explain an end-user-facing domain-specific configuration file format for a single application. It speaks to the greater underlying complexity, which is the point I’m making here. Also, if you ever have to warn your users not to despair when reading your docs, you should probably course correct instead.
Rewrite: The point that you made in your original comment is that sudo has too many features (disguising it as a point about complexity). The manpage snippet that you’re referring to has nothing to do with features - it’s a mix between (1) the manpage being written poorly and (2) a bad choice of configuration file format resulting in accidental complexity increase (with no additional features added).
Taking Drew’s statement at face value: There’s about to be another protracted, pointless argument about rewriting things in rust, and he’d prefer to talk about something more practically useful?
I don’t understand why you would care about preventing a protracted, pointless argument on the internet. Seems to me like trying to nail jello to a tree.
This is a great opportunity to promote doas. I use it everywhere these days, and though I don’t consider myself any sort of Unix philosophy purist, it’s a good example of “do one thing well”. I’ll call out Ted Unangst for making great software. Another example is signify. Compared to other signing solutions, there is much less complexity, much less attack surface, and a far shallower learning curve.
I’m also a fan of tinyssh. It has almost no knobs to twiddle, making it hard to misconfigure. This is what I want in security-critical software.
All of the above is orthogonal to choice of implementation language. You might have gotten a better response in the thread by praising doas and leaving iron oxide out of the discussion. ‘Tis better to draw flies with honey than with vinegar. Instead, you stirred up the hornets’ nest by preemptively attacking Rust.
PS. I’m a fan of your work, especially Sourcehut. I’m not starting from a place of hostility.
Sudo was first conceived and implemented by Bob Coggeshall and Cliff Spencer around 1980 at the Department of Computer Science at SUNY/Buffalo. It ran on a VAX-11/750 running 4.1BSD. An updated version, credited to Phil Betchel, Cliff Spencer, Gretchen Phillips, John LoVerso and Don Gworek, was posted to the net.sources Usenet newsgroup in December of 1985.
The current maintainer is also an OpenBSD contributor, but he started maintaining sudo in the early 90s, before OpenBSD forked from NetBSD. I don’t know when he started contributing to OpenBSD.
So I don’t think it’s fair to say that sudo originated in OpenBSD :)
I think at this point it’s reasonable to assume that all systems have privilege escalation vulnerabilities: OS’s attack surfaces are just too big to defend. I would not ever feel confident in assuming that a system is only partially breached once it’s had any hostile code running on it at all.
Privilege separation as a defense-in-depth mechanism still make sense, of course, but in dealing with a breach I would prefer to proceed as though it hadn’t worked.
There are systems like GenodeOS that are purposefully designed in an attempt to reduce the attack surfaces by compartmentalization & minimizing the trusted computing base (TCB), aiming to make it robust enough that it won’t have privilege escalation vulnerabilities.
Disclosure seems a bit rushed to me, given the high impact (and availability of sudo) of this thing. the authors also offer three different way of exploitation, and number 1 and number 3 are quite easy to implement without too much reverse engineering challenge.
As a friend pointed out to me, once sudo is patched, anyone can look at the diff and guess that there was a vulnerability patched, so once the patches are out there’s not much lost by full disclosure and you get a gain in awareness of the already-present threat.
There is no published POC for the exploit yet. The disclosure timeline is completely fine as the distro-list prefer short embargo periods. That means most distros knew about it at the time of disclosure and could prepare patched packages. This exploit isn’t really special.
So anyways back on track to the obvious rust question - it’s been a while since I’ve looked at rust and I’m not too familiar with heap-based overflow (as opposed to stack). Would safe rust have prevented this CVE? What other systems languages or tooling can catch this type of bug, whether it’s at compile time or runtime?
I’ve seen a few comments on the interwebs that “even a [good/half decent/other adjatiave] static analysis tool would have caught this”. I’ll note that infer, one of the best open source tools out there, does not catch this. It’s an ugly bit of code that discourages human readers and analysis tools - not surprising it lived for a long while.
Hello, I am here to derail the Rust discussion before it gets started. The culprit behind sudo’s vast repertoire of vulnerabilities, and more broadly of bugs in general, is accountable almost entirely to one matter: its runaway complexity.
We have another tool which does something very similar to sudo which we can compare with: doas. The portable version clocks in at about 500 lines of code, its man pages are a combined 157 lines long, and it has had two CVEs (only one of which Rust would have prevented), or approximately one every 30 months.
sudo is about 120,000 lines of code (100x more), its had 140 CVEs, or about one every 2 months since the CVE database came into being 21 years ago. Its man pages are about 10,000 lines and include the following:
If you want programs to be more secure, stable, and reliable, the key metric to address is complexity. Rewriting it in Rust is not the main concern.
Did you even look at that list? Most of those are not sudo vulnerabilities but issues in sudo configurations distros ship with. The actual list is more like 39, and a number of them are “disputed” and most are low-impact. I didn’t do a full detailed analysis of the issues, but the implication that it’s had “140 security problems” is simply false.
More like 60k if you exclude the regress (tests) and lib directories, and 15k if you exclude the plugins (although the sudoers plugin is 40k lines, which most people use). Either way, it’s at least half of 120k.
12k, but this also includes various technical documentation (like the plugin API); the main documentation in
sudoers(1)is 741 lines, andsudoers(5)is 3,255 lines. Well under half of 10,000.Except that it only has 10% of the features, or less. This is good if you don’t use them, and bad if you do. But I already commented on this at HN so no need to repeat that here.
You’re right about these numbers being a back-of-the-napkin analysis. But even your more detailed analysis shows that the situation is much graver with sudo. I am going to include plugins, becuase if they ship, they’re a liability. And their docs, because they felt the need to write them. You can’t just shove the complexity you don’t use and/or like under the rug. Heartbleed brought the internet to its knees because of a vulnerability in a feature no one uses.
And yes, doas has 10% of the features by count - but it has 99% of the features by utility. If you need something in the 1%, what right do you have to shove it into my system? Go make your own tool! Your little feature which is incredibly useful to you is incredibly non-useful to everyone else, which means fewer eyes on it, and it’s a security liability to 99% of systems as such. Not every feature idea is meritous. Scope management is important.
Citation needed.
Nobody is shoving anything into your system. The sudo maintainers have the right to decide to include features, and they’ve been exercising that right. You have the right to skip sudo and write your own - and you’ve been exercising that right too.
You’re asking people to undergo the burden of forking or re-writing all of the common functionality of an existing tool just so they can add their one feature. This imposes a great cost on them. Meanwhile, including that code or feature into an existing tool imposes only a small (or much smaller) cost, if done correctly - the incremental cost of adding a new feature to an existing system.
The key phrase here is “if done correctly”. The consensus seems to be that sudo is suffering from poor engineering practices - few or no tests, including with the patch that (ostensibly) fixes this bug. If your software engineering practices are bad, then simpler programs will have fewer bugs only because there’s less code to have bugs in. This is not a virtue. Large, complex programs can be built to be (relatively) safe by employing tests, memory checkers, good design practices, good architecture (which also reduces accidental complexity) code reviews, and technologies that help mitigate errors (whether that be a memory-safe GC-less language like Rust or a memory-safe GC’ed language like Python). Most features can (and should) be partitioned off from the rest of the design, either through compile-time flags or runtime architecture, which prevents them from incurring security or performance penalties.
Software is meant to serve the needs of users. Users have varied use-cases. Distinct use-cases require more code to implement, and thereby incur complexity (although, depending on how good of an engineer one is, additional accidental complexity above the base essential complexity may be added). If you want to serve the majority of your users, you must incur some complexity. If you want to still serve them, then start by removing the accidental complexity. If you want to remove the essential complexity, then you are no longer serving your users.
The sudo project is probably designed to serve the needs of the vast majority of the Linux user-base, and it succeeds at that, for the most part. doas very intentionally does not serve the needs of the vast majority of the linux user-base. Don’t condemn a project for trying to serve more users than you are.
Serving users is meritous - or do you disagree?
Yes, but the difference is that these are features people actually use, which wasn’t the case with Heartleed. Like I mentioned, I think doas is great – I’ve been using it for years and never really used (or liked) sudo because I felt it was far too complex for my needs, before doas I just used
su. But I can’t deny that for a lot of other people (mainly organisations, which is the biggest use-case for sudo in the first place) these features are actually useful.A lot of these things aren’t “little” features, and many interact with other features. What if I want doas + 3 flags from sudo + LDAP + auditing? There are many combinations possible, and writing a separate tool for every one of them isn’t really realistic, and all of this also required maintenance and reliable consistent long-term maintainers are kind of rare.
Yes, I’m usually pretty explicit about which use cases I want to solve and which I don’t want to solve. But “solving all the use cases” is also a valid scope. Is this a trade-off? Sure. But everything here is.
The real problem isn’t so much sudo; but rather that sudo is the de-facto default in almost all Linux distros (often installed by default, too). Ideally, the default should be the simplest tool which solves most of the common use cases (i.e. doas), and people with more complex use cases can install sudo if they need it. I don’t know why there aren’t more distros using doas by default (probably just inertia?)
Tough shit? I want a pony, and a tuba, and barbie doll…
My entire thesis is that it’s not a valid scope. This fallacy leads to severe and present problems like the one we’re discussing today. You’re begging the question here.
This is an extremely user-hostile attitude to have (and don’t try claiming that telling users with not-even-very-obscure use-cases to write their own tools isn’t user-hostile).
I’ve noticed that some programmers are engineers that try to build tools to solve problems for users, and some are artists that build programs that are beautiful or clever, or just because they can. You appear to be one of the latter, with your goal being crafting simple, beautiful systems. This is fine. However, this is not the mindset that allows you to build either successful systems (in a marketshare sense) or ones that are useful for many people other than yourself, for previously-discussed reasons. The sudo maintainers are trying to build software for people to use. Sure, there’s more than one way to do that (integration vs composition), but there are ways to do both poorly, and claiming the moral high ground for choosing simplicity (composition) is not only poor form but also kind of bad optics when you haven’t even begun to demonstrate that it’s a better design strategy.
A thesis which you have not adequately defended. Your statements have amounted to “This bug is due to sudo’s complexity which is driven by the target scope/number of features that it has”, while both failing to provide any substantial evidence that this is the case (e.g. showing that sudo’s bugs are due to feature-driven essential complexity alone, and not use of a memory-unsafe language, poor software engineering practices (which could lead to either accidental complexity or directly to bugs themselves), or simple chance/statistics) and not actually providing any defense for the thesis as stated. Assume that @arp242 didn’t mean “all” the usecases, but instead “the vast majority” of them - say, enough that it works for 99.9% of users. Why is this “invalid”, exactly? It’s easy for me to imagine the argument being “this is a bad idea”, but I can’t imagine why you would think that it’s logically incoherent.
Finally, you have repeatedly conflated “complexity” and “features”. Your entire argument is, again, invalid if you can’t show that sudo’s complexity is purely (or even mostly) essential complexity, as opposed to accidental complexity coming from being careless etc.
I dont’t think “users (distros) make a lot of configuration mistakes” is a good defence when arguing if complexity is the issue.
But I do agree about feature set. And I feel like arguing against complexity for safety is wrong (like ddevault was doing), because systems inevitably grow complex. We should still be able to build safe, complex systems. (Hence why I’m a proponent of language innovation and ditching C.)
It’s silly stuff like
(ALL : ALL) NOPASSWD: ALL. “Can run sudo without a password” seems like a common theme: some shell injection is found in the web UI and because the config is really naïve (which is definitely not the sudo default) it’s escalated to root.Others aren’t directly related to sudo configuration as such; for example this one has a Perl script which is run with sudo that can be exploited to run arbitrary shell commands. This is also a common theme: some script is run with sudo, but the script has some vulnerability and is now escalated to root as it’s run with sudo.
I didn’t check all of the issues, but almost all that I checked are one of the above; I don’t really see any where the vulnerability is caused directly by the complexity of sudo or its configuration; it’s just that running anything as root is tricky: setuid returns 432 results, three times that of sudo, and I don’t think that anyone can argue that setuid is complex or that setuid implementations have been riddled with security bugs.
Other just mention sudo in passing by the way; this one is really about an unrelated remote exec vulnerability, and just mentions “If QCMAP_CLI can be run via sudo or setuid, this also allows elevating privileges to root”. And this one isn’t even about sudo at all, but about a “sudo mode” plugin for TYPO3, presumably to allow TYPO3 users some admin capabilities without giving away the admin password. And who knows why this one is even returned in a search for “sudo” as it’s not mentioned anywhere.
This is comparing apples to oranges. setuid affects many programs, so obviously it would have more results than a single program would. If you’re going to attack my numbers than at least run the same logic over your own.
It is comparing apples to apples, because many of the CVEs are about other program’s improper sudo usage, similar to improper/insecure setuid usage.
Well, whatever we’re comparing, it’s not making much sense.
But, if you’re trying to bring this back and compare it with my 140 CVE number, it’s still pretty damning for sudo. setuid is an essential and basic feature of Unix, which cannot be made any smaller than it already is without sacrificing its essential nature. It’s required for thousands of programs to carry out their basic premise, including both sudo and doas! sudo, on the other hand, can be made much simpler and still address its most common use-cases, as demonstrated by doas’s evident utility. It also has a much smaller exposure: one non-standard tool written in the 80’s and shunted along the timeline of Unix history every since, compared to a standardized Unix feature introduced by DMR himself in the early 70’s. And setuid somehow has only 4x the number of footgun incidents? sudo could do a hell of a lot better, and it can do so by trimming the fat - a lot of it.
It’s not because it’s hard to use, it’s just that its usage can escalate other more (relatively) benign security problems, just like setuid can. This is my point, as a reply to stephank’s comment. This is inherent to running anything as root, with setuid, sudo, or doas, and why we have capabilities on Linux now. I bet that if doas would be the default instead of sudo we’d have a bunch of CVEs about improper doas usage now, because people do stupid things like allowing anyone to run anything without password and then write a shitty web UI in front of that. That particular problem is not doas’s (or sudo’s) fault, just as cutting myself with the kitchen knife isn’t the knife’s fault.
Yes, sudo has had more issues in total; I never said it doesn’t. It’s just a lot lower than what you said, and quite a number are very low-impact, so I just disputed the implication that sudo is a security nightmare waiting to happen: it’s track record isn’t all that bad. As always, more features come with more (security) bugs, but use cases do need solving somehow. As I mentioned, it’s a trade-off.
We already agreed on this yesterday on HN, which I repeated here as well; all I’m adding is “but sudo is still useful, as it solves many more use cases” and “sudo isn’t that bad”.
Interesting thing to note: sudo was removed from OpenBSD by millert@openbsd.org; who is also the sudo maintainer. I think he’ll agree that “sudo is too complex for it to the default”, which we already agree on, but not that sudo is “too complex to exist”, which is where we don’t agree.
Could sudo be simpler or better architectured to contain its complexity? Maybe. I haven’t looked at the source or use cases in-depth, and I’m not really qualified to make this judgement.
I think arguing against complexity is one of the core principles of UNIX philosophy, and it’s gotten us quite far on the operating system front.
If simplicity was used in
sudo, this particular vulnerability would not have been possible to trigger it: why havesudoeditin the first place, which just implies the-eflag? This statement is a guarantee.If it would’ve ditched C, there is no guarantee that this issue wouldn’t have happened.
If even the distros can’t understand the configuration well enough to get it right, what hope do I have?
OK maybe here’s a more specific discussion point:
There can be logic bugs in basically any language, of course. However, the following classes of bugs tend to be steps in major exploits:
It is hard to deny that, in a universe where nobody ever messed up those two points, there are a lot less nasty exploits in the world in systems software in particular.
Many other toolchains have decided to make the above two issues almost non-existent through various techniques. A bunch of old C code doesn’t handle this. Is there not something that can be done here to get the same productivity and safety advantages found in almost every other toolchain for tools that form the foundation of operating computers? Including a new C standard or something?
I can have a bunch of spaghetti code in Python, but turning that spaghetti into “oh wow
argvcontents ran over some other variables and messed up the internal state machine” is a uniquely C problem, but if everyone else can find solutions, I feel like C could as well (including introducing new mechanisms to the language. We are not bound by what is printed in some 40-year-old books, and #ifdef is a thing).EDIT: forgot to mention this, I do think that
sudois a bit special given that its default job is to takeargvcontents and run them. I kinda agree thatsudois a bit special in terms of exploitability. But hey, the logic bugs by themselves weren’t enough to trigger the bug. When you have a multi-step exploit, anything on the path getting stopped is sufficient, right?+1. Lost in the noise of “but not all CVEs…” is the simple fact that this CVE comes from an embarrassing C string fuckup that would be impossible, or at least caught by static analysis, or at very least caught at runtime, in most other languages. If “RWIIR” is flame bait, then how about “RWIIP” or at least “RWIIC++”?
I be confused… what does the P in RWIIP mean?
Pascal?
Python? Perl? Prolog? PL/I?
Probably Python, given the content of the comment by @rtpg. Python is also memory-safe, while it’s unclear to me whether Pascal is (a quick search reveals that at least FreePascal is not memory-safe).
Were it not for the relative (accidental, non-feature-providing) complexity of Python to C, I would support RWIIP. Perhaps Lua would be a better choice - it has a tiny memory and disk footprint while also being memory-safe.
That’s possibly it.
Not to mention that Lua – even when used without LuaJIT – is simply blazingly fast compared to other scripting languages (Python, Perl, &c)!
For instance, see this benchmark I did sometime ago: https://0x0.st/--3s.txt. I had implemented Ackermann’s function in various languages (the “./ack” file is the one in C) to get a rough idea on their execution speed, and lo and behold Lua turned out to be second only to the C implementation.
I agree that rewriting things in Rust is not always the answer, and I also agree that simpler software makes for more secure software. However, I think it is disingenuous to compare the overall CVE count for the two programs. Would you agree that
sudois much more widely installed thandoas(and therefore is a larger target for security researchers)? Additionally, most of the 140 CVEs linked were filed before October 2015, which is whendoaswas released. Finally, some of the linked CVEs aren’t even related to code vulnerabilities in sudo, such as the six Quest DR Series Disk Backup CVEs (example).I would agree that sudo has a bigger target painted on its back, but it’s also important to acknowledge that it has a much bigger back - 100× bigger. However, I think the comparison is fair. doas is the default in OpenBSD and very common in NetBSD and FreeBSD systems as well, which are at the heart of a lot of high-value operations. I think it’s over the threshold where we can consider it a high-value target for exploitation. We can also consider the kinds of vulnerabilities which have occured internally within each project, without comparing their quantity to one another, to characterize the sorts of vulnerabilities which are common to each project, and ascertain something interesting while still accounting for differences in prominence. Finally, there’s also a bias in the other direction: doas is a much simpler tool, shipped by a team famed for its security prowess. Might this not dissuade it as a target for security researchers just as much?
Bonus: if for some reason we believed that doas was likely to be vulnerable, we could conduct a thorough audit on its 500-some lines of code in an hour or two. What would the same process look like for sudo?
[Comment from banned user removed]
What?
So you’re saying that 50% of the CVEs in doas would have been prevented by writing it in Rust? Seems like a good reason to write it in Rust.
Another missing point is that Rust is only one of many memory safe languages. Sudo doesn’t need to be particularly performant or free of garbage collection pauses. It could be written in your favorite GCed language like Go, Java, Scheme, Haskell, etc. Literally any memory safe language would be better than C for something security-critical like
sudo, whether we are trying to build a featureful complex version likesudoor a simpler one likedoas.Indeed. And you know, Unix in some ways have been doing this for years anyway with Perl, python and shell scripts.
I’m not a security expert, so I’m be happy to be corrected, but if I remember correctly, using secrets safely in a garbage collected language is not trivial. Once you’ve finished working with some secret, you don’t necessarily know how long it will remain in memory before it’s garbage collected, or whether it will be securely deleted or just ‘deallocated’ and left in RAM for the next program to read. There are ways around this, such as falling back to manual memory control for sensitive data, but as I say, it’s not trivial.
That is true, but you could also do the secrets handling in a small library written in C or Rust and FFI with that, while the rest of your bog-standard logic not beholden to the issues that habitually plague every non-trivial C codebase.
Agreed.
Besides these capabilities, ideally a language would also have ways of expressing important security properties of code. For example, ways to specify that a certain piece of data is secret and ensure that it can’t escape and is properly overwritten when going out of scope instead of simply being dropped, and ways to specify a requirement for certain code to use constant time to prevent timing side channels. Some languages are starting to include things like these.
Meanwhile when you try to write code with these invariants in, say, C, the compiler might optimize these desired constraints away (overwriting secrets is a dead store that can be eliminated, the password checker can abort early when the Nth character of the hash is wrong, etc) because there is no way to actually express those invariants in the language. So I understand that some of these security-critical things are written in inline assembly to prevent these problems.
I believe that
explicit_bzero(3)largely solves this particular issue in C.Ah, yes, thanks!
It looks like it was added to glibc in 2017. I’m not sure if I haven’t looked at this since then, if the resources I was reading were just not up to date, or if I just forgot about this function.
I do think high complexity is the source of many problems in
sudoand thatdoasis a great alternative to avoid many of those issues.I also think
sudowill continue being used by many people regardless. If somebody is willing to write an implementation in Rust which might be just as complex but ensures some level of safety, I don’t see why that wouldn’t be an appropriate solution to reducing the attack surface. I certainly don’t see why we should avoid discussing Rust just because an alternative tosudoexists.Talking about Rust as an alternative is missing the forest for the memes. Rust is a viral language (in the sense of internet virality), and a brain worm that makes us all want to talk about it. But in actual fact, C is not the main reason why anything is broken - complexity is. We could get much more robust and reliable software if we focused on complexity, but instead everyone wants to talk about fucking Rust. Rust has its own share of problems, chief among them its astronomical complexity. Rust is not a moral imperative, and not even the best way of solving these problems, but it does have a viral meme status which means that anyone who sees through its bullshit has to proactively fend off the mob.
Offering opinions as facts. The irony of going on to talk about seeing through bullshit.
I don’t understand why you hate Rust so much but it seems as irrational as people’s love for it. Rust’s main value proposition is that it allows you to write more complex software that has fewer bugs, and your point is that this is irrelevant because the software should just be less complex. Well I have news for you, software is not going to lose any of its complexity. That’s because we want software to do stuff, the less stuff it does the less useful it becomes, or you have to replace one tool with two tools. The ecosystem hasn’t actually become less complex when you do that, you’re just dividing the code base into two chunks that don’t really do what you want. I don’t know why you hate Rust so much to warrant posting anywhere the discussion might come up, but I would suggest if you truly cannot stand it that you use some of your non-complex software to filter out related keywords in your web browser.
Agree with what you’ve wrote, but just to pick at a theme that’s bothering me on this thread…
This is obviously very subjective, and everything below is anecdotal, but I don’t agree with this equivalence.
In my own experience, everyone I’ve met who “loves” or is at least excited about rust seems to feel so for pretty rational reasons: they find the tech interesting (borrow checking, safety, ML-inspired type system), or they enjoy the community (excellent documentation, lots of development, lots of online community). Or maybe it’s their first foray into open source, and they find that gratifying for a number of reasons. I’ve learned from some of these people, and appreciate the passion for what they’re doing. Not to say they don’t exist, but I haven’t really seen anyone “irrationally” enjoy rust - what would that mean? I’ve seen floating around a certain spiteful narrative of the rust developer as some sort of zealous online persona that engages in magical thinking around the things rust can do for them, but I haven’t really seen this type of less-than-critical advocacy any more for rust than I have seen for other technologies.
On the other hand I’ve definitely seen solid critiques of rust in terms of certain algorithms being tricky to express within the constraints of the borrow checker, and I’ve also seen solid pushback against some of the guarantees that didn’t hold up in specific cases, and to me that all obviously falls well within the bounds of “rational”. But I do see a fair amount of emotionally charged language leveled against not just rust (i.e. “bullshit” above) but the rust community as well (“the mob”), and I don’t understand what that’s aiming to accomplish.
I agree with you, and I apologize if it came across that I think rust lovers are irrational - I for one am a huge rust proselytizer. I intended for the irrationality I mentioned to be the perceived irrationality DD attributes to the rust community
Definitely no apology needed, and to be clear I think the rust bashing was coming from elsewhere, I just felt like calling it to light on a less charged comment.
I think the criticism isn’t so much that people are irrational in their fondness of Rust, but rather that there are some people who are overly zealous in their proselytizing, as well as a certain disdain for everyone who is not yet using Rust.
Here’s an example comment from the HN thread on this:
There are a lot of things to say about this comment, and it’s entirely false IMO, but it’s not exactly a nice comment, and why Rust? Why not Go? Or Python? Or Zig? Or something else.
Here’s another one:
The disdain is palatable in this one, and “Rust is modernized C” really misses the mark IMO; Rust has a vastly different approach. You can consider this a good or bad thing, but it’s really not the only approach towards memory-safe programming languages.
Of course this is not representative for the entire community; there are plenty of Rust people that I like and have considerably more nuanced views – which are also expressed in that HN thread – but these comments certainly are frequent enough to give a somewhat unpleasant taste.
While I don’t approve of the deliberately inflammatory form of the comments, and don’t agree with the general statement that all complexity is eliminateable, I personally agree that, in this particular case, simplicity > Rust.
As a thought experiment, world 1 uses sudo-rs as a default implementation of sudo, while world 2 uses 500 lines of C which is doas. I do think that world 2 would be generally more secure. Sure, it’ll have more segfaults, but fewer logical bugs.
I also think that the vast majority of world 2 populace wouldn’t notice the absence of advanced sudo features. To be clear, the small fraction that needs those features would have to install sudo, and they’ll use the less tested implementation, so they will be less secure. But that would be more than offset by improved security of all the rest.
Adding a feature to a program always has a cost for those who don’t use this feature. If the feature is obscure, it might be overall more beneficial to have a simple version which is used by the 90% of the people, and a complex for the rest 10%. The 10% would be significantly worse off in comparison to the unified program. The 90% would be slightly better off. But 90% >> 10%.
I argue that it’s actually that it allows you to write fast software with fewer bugs. I’m not entirely convinced that Rust allows you to manage complexity better than, say, Common Lisp.
Exactly. Software is written for people to use. (technically, only some software - other software (such as demoscenes) is written for the beauty of it, or the enjoyment of the programmer; but in this discussion we only care about the former)
Even worse - it becomes more complex. Now that you have two tools, you have two userbases, two websites, two source repositories, two APIs, two sets of file formats, two packages, and more. If the designs of the tools begin to differ substantially, you have significantly more ecosystem complexity.
You’re right about Rust value proposition, I should have added performance to that sentence. Or, I should have just said managed language, because as another commenter pointed out Rust is almost irrelevant to this whole conversation when it comes to preventing these type of CVEs
The other issue is that it is a huge violation of principle of least privilege. Those other features are fine, but do they really need to be running as root?
Just to add to that: In addition to having already far too much complexity, it seems the sudo developers have a tendency to add even more features: https://computingforgeeks.com/better-secure-new-sudo-release/
Plugins, integrated log server, TLS support… none of that are things I’d want in a tool that should be simple and is installed as suid root.
(Though I don’t think complexity vs. memory safety are necessarily opposed solutions. You could easily imagine a sudo-alike too that is written in rust and does not come with unnecessary complexity.)
What’s wrong with EBNF and how is it related to security? I guess you think EBNF is something the user shouldn’t need to concern themselves with?
There’s nothing wrong with EBNF, but there is something wrong with relying on it to explain an end-user-facing domain-specific configuration file format for a single application. It speaks to the greater underlying complexity, which is the point I’m making here. Also, if you ever have to warn your users not to despair when reading your docs, you should probably course correct instead.
Rewrite: The point that you made in your original comment is that sudo has too many features (disguising it as a point about complexity). The manpage snippet that you’re referring to has nothing to do with features - it’s a mix between (1) the manpage being written poorly and (2) a bad choice of configuration file format resulting in accidental complexity increase (with no additional features added).
EBNF as a concept aside; the sudoers manpage is terrible.
I am not sure what you are trying to say, let me guess with runaway complexity.
Something else maybe?
Technically I agree with both, though my arguments for the former are most decidedly off-topic.
Taking Drew’s statement at face value: There’s about to be another protracted, pointless argument about rewriting things in rust, and he’d prefer to talk about something more practically useful?
I don’t understand why you would care about preventing a protracted, pointless argument on the internet. Seems to me like trying to nail jello to a tree.
This is a great opportunity to promote doas. I use it everywhere these days, and though I don’t consider myself any sort of Unix philosophy purist, it’s a good example of “do one thing well”. I’ll call out Ted Unangst for making great software. Another example is signify. Compared to other signing solutions, there is much less complexity, much less attack surface, and a far shallower learning curve.
I’m also a fan of tinyssh. It has almost no knobs to twiddle, making it hard to misconfigure. This is what I want in security-critical software.
Relevant link: Features Are Faults.
All of the above is orthogonal to choice of implementation language. You might have gotten a better response in the thread by praising doas and leaving iron oxide out of the discussion. ‘Tis better to draw flies with honey than with vinegar. Instead, you stirred up the hornets’ nest by preemptively attacking Rust.
PS. I’m a fan of your work, especially Sourcehut. I’m not starting from a place of hostility.
Why can’t we have the best of both worlds? Essentially a program copying the simplicity of doas, but written in Rust.
Note that both sudo and doas originated in OpenBSD. :)
Got a source for the former? I’m pretty sure sudo well pre-dates OpenBSD.
The current maintainer is also an OpenBSD contributor, but he started maintaining sudo in the early 90s, before OpenBSD forked from NetBSD. I don’t know when he started contributing to OpenBSD.
So I don’t think it’s fair to say that sudo originated in OpenBSD :)
Ah, looks like I was incorrect. I misinterpreted OpenBSD’s innovations page. Thanks for the clarification!
A little tangential:
I think at this point it’s reasonable to assume that all systems have privilege escalation vulnerabilities: OS’s attack surfaces are just too big to defend. I would not ever feel confident in assuming that a system is only partially breached once it’s had any hostile code running on it at all.
Privilege separation as a defense-in-depth mechanism still make sense, of course, but in dealing with a breach I would prefer to proceed as though it hadn’t worked.
There are systems like GenodeOS that are purposefully designed in an attempt to reduce the attack surfaces by compartmentalization & minimizing the trusted computing base (TCB), aiming to make it robust enough that it won’t have privilege escalation vulnerabilities.
Disclosure seems a bit rushed to me, given the high impact (and availability of
sudo) of this thing. the authors also offer three different way of exploitation, and number 1 and number 3 are quite easy to implement without too much reverse engineering challenge.As a friend pointed out to me, once sudo is patched, anyone can look at the diff and guess that there was a vulnerability patched, so once the patches are out there’s not much lost by full disclosure and you get a gain in awareness of the already-present threat.
There is no published POC for the exploit yet. The disclosure timeline is completely fine as the distro-list prefer short embargo periods. That means most distros knew about it at the time of disclosure and could prepare patched packages. This exploit isn’t really special.
So anyways back on track to the obvious rust question - it’s been a while since I’ve looked at rust and I’m not too familiar with heap-based overflow (as opposed to stack). Would safe rust have prevented this CVE? What other systems languages or tooling can catch this type of bug, whether it’s at compile time or runtime?
Yes any language with bounds checking (including Rust) would have panicked/raised an exception at the out of bound read and crashed.