Would Rust have prevented Heartbleed? Another look
tonyarcieri.com
tonyarcieri.com
Had I been a bit more careful in my claim then there'd have been no question. Ted was technically accurate (the best kind), but a lot of the resulting discussion was of the form "bad coders can always write security holes, therefore a language isn't the fix, so C's OK". Even when major products, like everything MS ships, have critical CVEs almost exclusively due to memory safety, not arbitrary bad logic. Further tptacek likes to point out that memory safety is just one class of sec bugs, and that there's frillions of other bugs in other classes. My suspicion is that this is more of a bias towards app-level stuff (ie command injection in a billion web apps), not systems. I suppose if you get pwnd it doesn't matter how, but a world free of all those MS memsafety RCEs seems like a qualitatively different one.
But hey, I'm just some arbitrary weakling, and I find it hard to challenge people that are both smarter and drastically more experienced than I.
It takes more thought to write Rust programs. If you want to write safer widely-deployed infrastructure, you should learn about it. It may not be your best option right now, but its ideals are those that we absolutely need to strive for. Acting macho about C and the ability to write it safely does not lead to fewer RCE's in the world. It leads to more, because newcomers may see such people who can do so as examples to be emulated, far before they are capable.
Note that there are no familiar critics who say that Rust will not prevent some bugs. Note that there are no familiar proponents who claim that Rust will prevent all bugs. It is an implementation that strives to make progress in an area that we can all agree with - the safety of our programs with minimal performance degradation.
A memory safe language alone isn't enough. Look at Java. Isn't that supposed to be a memory safe language? And yet it's constantly got security issues.
Not to say that Java is going to eliminate all bugs. However, it should eliminate all bugs to do with, e.g., reading/writing out of the bounds of an array and resulting in RCE due to bugs introduced in the application code. Reading/writing out of the bounds of an array will still be a bug, but not one that allows arbitrary code execution (at least not in the same way as it may for a language like C.
In fact, one of the first real security holes I've ever found was in 1.0 version of the CLR. You could load a function pointer to an un-JIT'd function, then later on use that to safely jump to other code. This is technically a RCE, but the user has to be executing your code first anyways. That is, if the CLR and Java didn't set out to run "partially trusted" code with no help from the OS, these wouldn't have been problems at all.
Other languages like C, Ruby, etc. simply don't have this "partially trusted" concept so there's nothing to attack. (Well I guess things like Native Client or VMware qualify, but they're at a better abstraction later than JVM or CLR permissions.)
http://www.cs.cornell.edu/People/egs/kimera/flaws/vacuum/
But most security holes these days are not flaws in the JVM/CLR, but logical errors made in the application; e.g. allocate a buffer and reuse it, this says nothing about memory safety at the VM level at all!
And at that, no one really trusts JVM security anymore, preferring to sandbox the entire operating environment in a heavyweight or lightweight VM.
But most applications are written in memory-safe languages, so it's not surprising that most vulnerabilities are found in non-memory-safety related areas. The more interesting statistic is the number of critical security bugs that are memory-safety related in non-memory-safe languages.
But app level bugs aren't what gives Java a bad name, are they? When someone says, like the GP, that "what about Java, that's got tons of security issues", that's almost certainly from its use as a browser plugin. Otherwise everyone would be saying the same about every language out there.
Ya, when people say Java is insecure, they usually mean the Java plugin has insecure interfaces. As the browser + Java becomes increasingly rare, it fades from our memory. There is nothing insecure or secure about the language, memory safety actually works...but its only one small part in having a secure environment.
I worry about Rust, it pushes the safety card much more aggressively, but in reality without full on aggressive dependent typing, they'll only be able to guarantee a few basic properties. The language won't magically make your code "secure", just a bit easier to secure.
Our analysis of the security benefit of Rust comes from two very simple, empirical facts:
1. Apps written in memory-safe languages do not have nearly the same numbers of memory safety bugs (use after free, heap overflow, etc.) as apps written in C and C++ do.
2. Memory safety issues make up the largest number of critical RCE bugs in browser engines.
> The language won't magically make your code "secure", just a bit easier to secure.
Of course it won't magically make your code secure. Applications written in Rust will have security vulnerabilities, some of them critical. But I'm at a loss as to how you can claim that getting rid of all the use-after-free bugs (just to name one class) inside a multi-million-line browser engine in a language with manual memory management is easy. Nobody has ever succeeded at it, despite over a decade of sustained engineering effort on multiple browser engines.
I didn't claim it was "easy", just that bugs would still exist and the browser's "securedness" would only increase marginally. The problem is not that this isn't an achievement, only in managing expectations (e.g. saying Rust is secure which doesn't make sense).
> Nobody has ever succeeded at it, despite over a decade of sustained engineering effort on multiple browser engines.
It is a nice goal, but the question is where is the world afterwards? Will Firefox all of a sudden become substantially more secure and robust vs. its competition, to the extent that it can out compete them and increase its market share significantly?
My brief experience at Coverity makes me guess that you could be getting rid of one class of bugs without necessarily improving the product in any noticeable way...that ya, those bugs were common but not particularly easy to exploit or hard to fix once found.
Not that the effort isn't worthy at all. I'm just a bit cynical when it comes to seeing the tangible benefits.
I disagree with the latter. Based on our analysis, Rust provides a defense against the majority of critical security bugs in Gecko.
> It is a nice goal, but the question is where is the world afterwards? Will Firefox all of a sudden become substantially more secure and robust vs. its competition, to the extent that it can out compete them and increase its market share significantly?
You've changed the question from "will this increase security" to "is improved security going to result in users choosing Firefox en masse". The latter question is a business question, not a technical question, and not one relevant to Rust or this thread. At the limit, it's asking "why should engineering resources be spent improving the product".
Rust is a tool to defend against memory safety vulnerabilities. It's also a tool to make systems programming more accessible to programmers who aren't long-time C++ experts and to make concurrent and parallel programming in large-scale systems more robust. The combination of those things makes it a significant advance over what we had to work with before, in my mind.
> My brief experience at Coverity makes me guess that you could be getting rid of one class of bugs without necessarily improving the product in any noticeable way...that ya, those bugs were common but not particularly easy to exploit or hard to fix once found.
It is true that exploitation of UAF (for example) is not within the skill level of most programmers and that individual UAFs are easy to fix. But "hard for most programmers to exploit and easy to fix" doesn't seem to be much of a mitigation. For example, the Rails YAML vulnerability was also hard to exploit (requiring knowledge of Ruby serialization internals and vulnerable standard library constructors) and easy to fix (just disable YAML), but it was rightly considered a fire-drill operation across Web sites the world over. The "smart cow" phenomenon ensures that vulnerabilities that start out difficult to exploit become easy to exploit when packaged up into scripts, if the incentives are there to do so. Exploitable use-after-free vulnerabilities in network-facing apps are like the Rails YAML vulnerabilities: "game-over" RCEs (possibly when combined with sandbox escapes).
The developers' claim is that more than half of all security bugs are bugs due to memory safety issues and that Rust will solve these. More than halving the number of bugs doesn't sound marginal to me.
In other words, if we magically went back in time and wrote all MS products in Rust instead of C++, their CVE could for RCEs, their famous worms, etc. would all disappear (except in the cases where they explicitly opted into unsafe features.)
Back in the 90s and early 00s, a lot of the low fruit was buffer overflows or forged pointers. Then we got serious about fuzz testing and static analysis, and now they are picking at other fruit (which is why Heartbleed was so weird).
I'd love to see Rust shown too.
The other Java bugs are ones that'd plague any language: SQL injection, rules-engines-gone-wild, etc.
Web sandboxes are full of holes too. That's why modern browsers have sandboxes within sandboxes. I don't think an HTML5 sandbox is less complicated than the JVM sandbox.
Sure. Nobody is claiming (or should claim) that memory safety is a solution to all security problems. That's independent of the claim that memory safety is an effective defense against common vulnerabilities in C and C++ programs.
Unspecified vulnerability in Oracle Java SE 6u85, 7u72,
and 8u25 allows local users to affect confidentiality,
integrity, and availability via unknown vectors related
to Deployment.Has it? I can't remember the last time I saw a security advisory for Tomcat or Jetty (there are some but they're rare), in stark contrast to Apache or Nginx.
No; you have D for that.
EDIT: Seriously, for the grumpy down voter: I've seen quite a few programmers write that they use D even for things that are normally considered as scripting tasks.
Security is all or nothing. You can't have a little bit of this and a little bit of that. Unless the parts of the web browser that can be "influenced" by external attacker (directly or indirectly) are written 100% in a memory safe language, you simply have no real security but the illusion of such.
And this is how that hypothetical browser fails, and why it will never amount to anything re: security, since it's gonna end up using a gazillion of C libraries, all of them full of bugs and possibly vulnerable to security exploits.
One could say that Rust also fails by allowing "unsafe" code in its core design but it's still too early to see how that will play out.
As an example, I would happily claim that nginx is more secure than wordpress or the average php website written with mysql_query in the 90s. Does nginx have bugs? Probably somewhere in there. Are they as likely to be found, exploited, or (when exploited) lead to as serious issues? I doubt it.
Security is often about many many levels. A good example of this is Chrome, its sandboxing, operating system memory randomization, and user privileges. When someone finds a bug in v8, to turn it into root on the box requires bugs in all those layers (see writeups for pwn2own).
Generally, an improvement in security at any layer will reduce the impact of bugs at other layers. I'd absolutely rather have a browser written 20% in rust than 0% in rust.
Unless we want everything to run as poorly (relatively speaking) as a web-application in a browser on a less-than top of the line computer... User-level applications are written on top of lower-level systems... the lower they are, the more important raw speed, and limited use of memory is.
I like to say that of course Rust prevented Heartbleed, because we don't currently support wrapping malloc ;). That's of course a bit glib.
While it's true that Rust gives you a lot of assistance with writing safe code, given that unsafe exists, and that we, as a systems language, need to give you underlying access to the machine, Rust will allow you to do all kinds of stupid things if you vouch to the compiler that you're going to handle the safety aspect. This means that ultimately, you can do any kind of stupid thing in Rust that you can do in any other language.
An example: a common problem in C code is buffer overflows, which happens when some code thinks that an array has more elements in it than it does. Because C's arrays don't have a length as part of the type, it can be error prone to keep track of the length of the array. Rust's arrays, vectors, and slices all have a length as a part of the type, and so it's more difficult to have this data be out of sync. But Rust will let you be stupid if you want to:
fn bad_stuff(v: Vec<i32>) -> i32 {
unsafe {
*(v.get_unchecked(v.len() + 1))
}
}
fn main() {
let vec = vec![1, 2, 3];
let val = bad_stuff(vec);
println!("{}", val);
}
Now, there's a decent discussion that can be had on this topic: 'usual' Rust code will of course be significantly safer than 'usual' C code, since you have the compiler's assistance. Unfortunately, security is often about the edge cases. While it's true that not wrapping malloc would have prevented Heartbleed from happening, and most C projects don't wrap malloc... it did happen. Once Rust starts getting used in the wild, we'll see Rust with security problems, I'm sure of it. That doesn't mean that Rust has no value, just that we need to be realistic about the tradeoffs that any of our technologies make. Rust is not a panacea, even if it does cure some of your aches and pains.
The key insight about Rust is the set of programming abstractions (linear types to manage resources) that enable one to get systems-like programming tasks done, without needing to fall back on very low-level coding techniques.
I think you mean it's a bit glibc.
Seems like it would be a pretty easy problem to fix if you're not playing fast and loose.
"Half a hole is still a hole," he said smugly.
"But it's a much smaller hole," I replied.
I for one am ready for my daily Rust PR programming.
A key phrase in Ted's article is Hopefully the simulacrum retains the essence of the problem.
What Tedbleed, as your article calls it, demonstrates is a bug similar to Heartbleed: reuse of a buffer in a memory-safe language is susceptible to leakage of secrets.
While I might answer the question are Rust’s memory safety features being oversold by uninformed zealots?, no I don't think so, but I would suggest that thinking that memory safety ends all security issues is a not good plan.
The key is Unless you venture into the (explicitly demarcated) unsafe portion of Rust, you will not see memory exposure vulnerabilities like Heartbleed: the language does not prevent this. Perhaps your post will stimulate Ted to go further with his example and write an erroneous complete TLS stack in Rust, showing how it too can do Heartbleed. Perhaps you agree that this can be done.
Among the scariest mass vulnerabilities relating to total information disclosure, the Padding Oracle Attack, the BEAST attack, the compression flaw CRIME, none have to do with memory safety of languages. Rust there would not have helped one whit.
Memory safety is just one issue in writing secure code.
Edit: typo
Using <$LANG> prevents leakage of secrets!
When put like that, it sounds like a straw-man argument. In my own words, the narrower and stronger claim being made is that the specific and important avenue by which Heartbleed leaked secrets is not possible without unsafe code in Rust.
So if you're going to claim that Ted "isn't wrong", but on terms that no one was originally arguing... I don't even know what to say.
Perhaps I am taking a more general implication of this than "Rust would not have exactly reproduced the Heartbleed problem". I infer the overall meaning of Ted's argument, and the general discussion that "Memory safe languages do not prevent information leakage". To me that is what the argument is about.
If the argument is that you can write a program in Rust that tells someone something they shouldn't know… is that… what's even the argument here? Is that even a question?
But in that case, comparing against Heartbleed is pointless. Why not ask about SQL injection attacks? Or directory traversal attacks? Or OS privilege escalation attacks? Or listening on a port that isn't correctly firewalled? Rust won't prevent any of those either, because none of them have anything to do with the language being used.
Arguing that it's possible to write code that does the wrong thing is so pointless that I can't understand why this article was written other than as some kind of half-assed hatchet job.
Alright. Please clarify. What is the specific and important avenue by which Heartbleed leaked secrets?
In rust, if I write code where I store my secrets in two variables which I pass into my ssl constructor, but retain single ownership of (such that the ssl library may not retain references to them after the constructor exits), there is no way for those exact memory addresses to be read and returned via that library, excepting unsafe.
If you say "ah, but the constructor could take a copy and leak that", then that's a different class of vulnerability. It could, but then it would be leaking its memory, not mine.
However, that completely does not relate to your question. I'm not saying that they both aren't security vulns, they both are.
You asked how heartbleed leaked secrets (implicitly how it was different from the rust code), and I told you how it differs. Where the secrets are stored is different. One is user-supplied secrets only, the other is arbitrary secrets within the process, user-supplied or otherwise. Yes this is different.
Your response here is simply moving the goalposts.
Heartbleed was not just re-using a buffer, it was also blindly copying program memory into that buffer because C allows such memory access.
You're simplifying the problem and wording it in a way where the difference is masked, but as I already explained clearly, it's different. Feel free to tell me how the rust code could access the linking program's process memory without using unsafe and without explicitly taking ownership of data from it, and I'll eat my words.
In ANY case, if you build it(unsafe) they will come. People WILL be writing code using unsafe.
> People WILL be writing code using unsafe.
There would be costs to this - both in runtime performance (presumably you wanted to reuse buffers for a reason) and in program complexity. And of course it's possible to make an error in your type definitions (though you have to make two errors to be exploitable - one in the types and one in the values - and the types are shorter and much easier to audit than the full program code). But it absolutely is possible, and I think that pretty soon we'll reach the point where it becomes worthwhile for security-critical code.
Of course ultimately you can Greenspun any language to do what any other language can. But in practice a language where the vocabulary already exists - where you have higher-kinded types and existing generic libraries for handling when a value has a particular "context" - makes it much more practical.
I think the real key is that in C, this leak can happen with just malloc+forgetting a memset, no explicit buffer reuse required. Whereas in Rust, you'd need to explicitly reuse the buffer.
And, even if you did have such an allocator, you still can't read past the end of the allocation. So if you ask for a 16 byte buffer and attempt to read 17, it'll fail.
In other words: idiomatic C and a sane malloc() implementation could have actually prevented Hearbleed.
It makes sense to assume that un-idiomatic Rust and reusing memory without clearing it would trigger the same bug.
Or did I misunderstand your point about "malloc sanity"?
As someone else pointed out, OpenBSD's malloc() implementation could have supplied a cleared memory area with no discernible performance impact (in fact, I think LibreSSL already does).
There are some other protection mechanism included, too; there's a more in-depth presentation here:
http://www.openbsd.org/papers/eurobsdcon2009/otto-malloc.pdf
> What Tedbleed, as your article calls it, demonstrates is a bug similar to Heartbleed
Similar but very different in the severity.
> but I would suggest that thinking that memory safety ends all security issues is a not good plan.
Nobody said that.
> The key is Unless you venture into the (explicitly demarcated) unsafe portion of Rust, you will not see memory exposure vulnerabilities like Heartbleed: the language does not prevent this.
Sure, if you want to break it, you'll probably can, but you'll have all kinds of warnings before and the few lines where you actually do that, can be proofread the most times.
There's nothing preventing you from writing common bugs the generate vulnerability either, but that's simply not possible.
> Perhaps your post will stimulate Ted to go further with his example and write an erroneous complete TLS stack in Rust, showing how it too can do Heartbleed. Perhaps you agree that this can be done.
Well, Rust may have a memory leak at some point in the future, no software is perfect, but that is one language, that will be review constantly, that is mainly memory safe, the other is one language that is not memory safe where thousands of developers are constantly writing code, inserting lots of heartbleed/memory kind of bugs.
> Among the scariest mass vulnerabilities relating to total information disclosure, the Padding Oracle Attack, the BEAST attack, the compression flaw CRIME, none have to do with memory safety of languages. Rust there would not have helped one whit.
That's not the point of the article, ted tries to say that hearbleed would be possible, author contradicts this as it shows how the vulnerability would be of different severity.
To differentiate these as "very different in severity" is I think quite misleading.
Really? The private key in asymmetric cryptography should never/is assumed to never be known to anyone other than the key-holder. Session keys are understood to be shared, and so are by definition not secure (equivalently, I can log my part of the "conversation" with a server, even if over TLS with PFS). So session keys, session cookies, transmitted data -- is always known by more than one party, a secret key should never be known by more than one party.
It is true that most TLS server deployments don't enforce this -- they don't do the asymmetric operations in a trusted computing module, smart card etc -- but they should. They shouldn't store the key in ram, but they currently do.
If you get the secret key, you can do many more things than merely intercept traffic. You can impersonate and fake traffic (fake evidence).
In addition to all this, being able to read arbitrary memory controlled by the same process is also worse than being able to read stuff that is already being transmitted. This isn't strictly a Rust/other language issue (I imagine, but do not know, that one eg could sanely (if foolishly) share buffers across thread pools, and so potentially leak information across clients -- this would probably be a design error wrt. trust boundaries etc ... but no-one is arguing that any language can prevent design errors).
As mentioned in other comments, privilege separation (a la openssh etc) is a great way to help leverage the os/kernel in order to enforce assumptions about the security primitives used. But that's a little beside the point.
HTTPS is a little different. You need to verify you're talking to the real paypal.com, but that's so you know you're not sending your password to a stranger. paypal doesn't send signed emails, for instance. (maybe they should, but not with the website key, for sure). Stealing passwords and cookies is pretty much the end game for https private key theft.
Is anyone willing to say that a bug which only leaks passwords and cookies is a minor issue?
wrt heartbleed, there seems to be a gap between the "could happen" and "did happen" consequences. Besides the one test server pummeled with millions of requests, were any private keys actually compromised? On the other hand, we know yahoo passwords were compromised because people were doing it within hours of the heartbleed announcement. I'm more concerned with the latter.
Yes, if I'm writing a sort function for vulnerabilities, "read arbitrary memory" is worse than "read some memory", but there should be some accounting for degree of difficulty as well.
What is more important is whether using a language like Rust will prevent some severe security holes, and the answer is quite obviously that it will. Sure, it's possible to create bugs in any language, but it's much harder to prevent bugs in C than in most languages.
I do believe that the right developers, using the right practices, could make a more-secure OpenSSL. But it would be expensive in terms of developer time. Maybe a group with the right experience could crowdfund it?
- Both Go and Rust use bounds checking on arrays/slices (which means out-of-bounds accesses are not allowed).
- Go is garbage collected, so memory leaks cannot occur.
- Rust encourages an ownership/lifetime model, so memory leaks cannot occur.
- Go can still have data races between multiple concurrent threads. To catch them, you must use the race detector _at run time_. Note however that Go encourages communicating information over channels, and if idiomatic code is being written the chance of data races is next to none.
- Rust cannot have data races in most cases, as it's ownership/lifetime model allows for catching them _at compile-time_.
- Both of these assumptions are based on no external C or unsafe code being in the picture.
TL;DR: Very similar.
EDIT: I used the wrong terminology -- sorry. Instead of _memory leak_ I should have said _dangling pointers_ (memory leaks can occur in _any_ language, Go/Rust/Java/JS/etc).
Well it depends on how you define memory leaks. Memory leaks can of course occur logically. Like say you create objects in a cache and never remove them. It is still a memory leak.
But at the level that you define the memory leak, it seems Rust can be just as good as Go because memory ownership is tracked by the compiler. One can say it is even better because of compile time checks and no need to have a GC @ runtime present.
However, in practice most values can be neither Rc nor Gc but single-owner, like unique_ptr in C++, which is easier to reason about than either.
So far so good. But You forget to allocate smaller array (and copy members) when you consume too much memory. So 1000000* push(something) followed by 1000000*pop() keeps plenty allocated memory not in usage.
(It's not as brutal as malloc() and forget the result but still pretty awfull situation in a large project.)
To catch _some of_ them :) No guarantee that they will all be caught.
> The cost of race detection varies by program, but for a
> typical program, memory usage may increase by 5-10x and
> execution time by 2-20x.Rust has one killer feature that Go does not have: the typesystem has semantics for memory sharing. You can declare how a pointer can be used: is it accessed concurrently, is it local to me, &c. This helps the typesystem detect race conditions where two threads access a block of memory in an unsafe way.
Go does not have this. In Go, you "share memory by communicating", instead of "communicating by sharing memory." But if you do want to share memory, you are back to using locks and your own conventions and mechanics to prevent concurrent access. The language doesn't help you.
So it's a different programming paradigm. And if you use Go like you would use Rust (memory sharing), then Go is less safe.
(...right?)
EDIT: This sounds one-sided, but I'm only talking about sharing memory, here. If you don't do that, and stick to communicating, then Go can blow you away. I don't know how Rust deals with coroutines, but Go has super light threads (goroutines) that make concurrent behavior pure joy. All your threads can so easily talk to eachother, and wait for eachother, and it's all so light and native and good!
E.g. you have a handler for a POST, but you only want to close the connection when another thread has finished doing something. And you don't want to tie up an entire OS thread, because it could take a while and that's just too expensive. In go: super easy, just do a blocking channel read. In another language? Wow, where would I start...
(How does rust do that?)
Sometimes, yes, using a mutex makes more sense -- and that does introduce the possibility of a data race.
If you follow effective Go code -- I imagine the code is on average about just as safe as Rust code is. It is partially comparable to using `unsafe` blocks in Rust -- don't do it, unless you know what you're doing. Stick with channels.
That said, channels in Rust are also nice to use, and you shouldn't not choose channels. Rust just enables other use-cases too.
Don't take this the wrong way, I'm not complaining about Go. Just know that sometimes, there are real reasons to share memory. And when you do: Rust has got your back, but in Go you're on your own.
Rust transfers ownership when you send a single-owner reference over a channel. The sender can no longer access the referenced object; the compiler prevents that. That's the safe way to do it. This is a significant advance in multi-thread programming. The rules that make this work are strikingly simple. Somebody should have thought of this 20 or 30 years ago, but as far as I know, nobody did. Rust pushes the single-owner model hard, and it seems to work. The C++ crowd beat their head against the wall on this for decades, through three generations of auto_ptr, then unique_ptr. Really getting it right requires something like the Rust borrow checker, which C++ does not have.
Go does not do anything to prevent sharing data between threads. It's very easy in Go to unwittingly create shared data, because slices are references. After you've sent a reference, the sender still has access to the shared data, as does the receiver, so there's a potential race condition. Go does nothing to prevent this. There's a lot of dancing around this issue in "(In)effective Go", and long discussions of "is this a race condition" in Go forums. Go is a useful language, but it's in spite of Go's concurrency system, not because of it.
The same claim can be made for C++ (with uniqe_ptr<T>), but we know how that faired. It is telling enough that there is a race detector tool for Go.
std::unique_ptr<int> p(new int(1));
std::unique_ptr<int> q = p;
You can strong arm it into break but you can also reuse a pointer locally in Go after it was sent over a channel.
#include <iostream>
auto f() {
int x = 1;
return [&] () { return x; };
}
int main(int, char **) {
std::cout << f()() << std::endl;
}
If you want something particularly involving unique_ptr, consider that best practices are to give non-owning sharing as raw pointers: you could say they're safe as long as you use them correctly but again that misses the point. I can also give an example (stolen from a talk) directly involving shared_ptr even when used with traditional "best practices" although I'm sure the best practices will update themselves to include this.
In some sense, Rust has been described as merely formalizing and automatically enforcing the best practices that people were already using in C++; it's the formality and automaticity that turns it from a dangerous language to a safe one.
My first thought would be to attach the connection object to the data the other thread is working on. When it is done it processing your message it drops the whole thing, closing the connection. If you want to hold it open for multiple workers you could make it an Arc<Connection> so it doesn't close until they all drop it.
(Disclaimer: I'm a Rust developer.)
Go doesn't enforce this on a compiler level -- but instead it encourages the use of sharing by communicating (over channels, where data races cannot occur), instead of sharing memory e.g. via a mutex (where you can run into a data race).
- easily callable from other languages because of the C ABI
- runtime free and not Posix dependent
- portable across CPU architectures.
Rust will provide you memory safety where other languages can't even run.
There's many things I don't like about rust but the above list make it very hard to beat.
Rust on the other hand is a completely different animal to anything I've used before. It has one of the most annoying compilers but that is for a reason, if your code compiles then it's memory safe (with a few exceptions, like 'unsafe' block)
I don't see how the fact that most languages can't be dropped into C programs makes the fact that Rust can not interesting. It seems to me to imply the opposite.
For the security topic, most of the power of Rust come from a strong typing, safety checks (boundaries), ownership checks... Well, a lot of checks at compile time.
As far as I know of Rust by glancing at the doc frequently, C++11/14 also contains these "safe tools": ownership can be dealt with smart pointers (unique, shared), value semantics, move semantics (rvalues) and the rest. Boundaries checks with the correct containers (std::vector, std::array...). Mutability with "const". Atomicity with std::atomic... Type safety by using explicit conversions, templates instead of macros, variadic args...
Heck, all the drama from C++ seems to come from a misusage or some legacy parts from another age (up to C). In order to avoid people to shot themselves in their feets, why couldn't we just introduce a strict compilation mode a la JavaScript to let say Clang: # pragma strict
# pragma unsafe # pragma safe
Nowadays, good C++11 compilers can even deal with such a things like constexpr. This seems a reachable goal.
What are the true drawbacks of a fully modern C++ code compared to a Rust? Is there any true feature that can't be done in C++ due to a deep problem of conception? Don't le me wrong, I do not seek to diminished the amazing work of Mozilla. I am not talking neither about the other cool features from functional languages, switch cases... that Rust has and C++ don't.
C++11/14 lets you assign a std::unique_ptr to another variable then re-use the original variable, causing a null dereference. You can also have a reference to the same std::unique_ptr from two different threads causing a race-condition on the underlying pointer.
There is no bounds checking on std::vector by default. You can bounds check a std::vector (using "at" or various configuration/compiler settings which change the semantics of the standard library) but by default, it is not checked.
Fundamentally, the issue is that C++ lets you have null pointers and references (yes, references can be null). It lets you use before initializing. It lets you run out of bounds. It lets you access the same variable from multiple threads without any safety. Yes, idiomatically, none of these should be an issue but it's not possible to be a perfect programmer.
Rust forces idiomatic memory management and eliminates all these issues. If you make a memory safety mistake, the compiler will force you to fix it.
- For instance, the reuse of the original variable could be deduced by the compiler. - The bound checking for std::vector can effectively be enable. One could imagine an std::strict_vector that do so.
What I am wondering is: does the same idiomatic memory management applied to C++ would require some huge tweaks to the language, some bad tricks, new keywords, or can it be done without changing its design but enforcing some rules?
I, for instance, have no clues how to deal with your "one unique_ptr two threads" problem. Could it be done in an elegant way in C++?
Unfortunately, currently no "sufficiently smart compiler" exists, so that high-level code can be optimized sufficiently to beat what a good micro-optimizing C++ compiler (which can assume that no undefined behavior can occur at runtime) can achieve.
Point being: Underspecification can give you a lot of leeway in how you do something -- and that can be hugely valuable in practice.
Just as an aside: Personally I tend to prefer safety over performance, but I was persuaded that UB is valuable by comments that Chandler Carruth of Clang (and now ISO C++ committee) fame made about UB actually being essential to optimization in C++. Sorry, can't remember where, exactly, those comments were made.
[1] Everybody's probably using two's-complement (for good reasons).
[2] Not nearly as easily as plain buffer overflows, but there have been a fair few of these that have been exploitable.
In any case, I believe Rust retains many of the optimisations made possible via UB in C++ by enforcing things at a compile time. In fact, Rust actually has quite a lot of UB... that is, there are many restrictions/requirements Rust 'assumes' are true. For example, the reference types & and &mut have significantly more restrictions around aliasing and mutability than pointers or references in C++. The key difference between Rust and C++ is that it is only possible to trigger the UB with `unsafe`, as the compiler usually enforces rules that guarantee they can't occur. People saying "Rust has no UB" are usually implicitly meaning "Rust cannot trigger any UB outside `unsafe`".
A simple pointer arithmetic loop over a string in C could lead to very nasty bugs if said string isn't null-terminated (for whatever reason), in rust you wouldn't think of using unsafe code to do that.
How much unsafe code does Servo use ? It seems most of the unsafe code blocks I see have a "TODO" block with some explanation of why it's unsafe, and with the express intent of removing the unsafe block eventually.
Servo use C++ libraries, so it's far from safe code. Try to use Servo - you will see failures in first minute, I've tried.
As for the usage of C++ libraries, this will diminish over time. The history of Servo thus far has included a gradual process of rewriting C++-based components in Rust, and sometime this year Mozilla intends to begin rewriting small components of Firefox in Rust. Reducing the attack surface is always valuable.
I didn't mean to sound aggressive, we really would welcome reports of safety issues. It's hard to know if servo /really/ is safer without the hundreds of people trying to exploit it that chrome & firefox have.
Servo should be safer & I believe it's safer but I don't /know/ it's safer.
Then you have memory leaks that happens because the application has data structures that grow unbounded. The latter one is not really preventable by automatic means, because the memory is still referenced from elsewhere in the application, and a garbage collector can't know that this memory won't be accessed again.
It does help that the most common source of memory leaks is eliminated however. That many Java applications are memory hogs is more a result of typical Java programming style than anything else.
This may be part of it, but typically, the JVM will happily reclaim large chunks of memory from the OS, without necessarily allocating anything internally.
and it should not be possible. Rust has a sound type system that uses linear affine typing. While their implementation is not "proven correct", in practice if the Rust compiler is working properly, leaks will not happen.
EDIT: Box don't leak.
Memory-safe arrays, which is what's at issue here, is precedented in tons of languages. Even GW-BASIC got this right.
It should be an embarrassment to the entire systems programming community that it's 2015 and we're only starting to think of replacing C.
As Dijkstra said: "Program testing can be used to show the presence of bugs, but never to show their absence."