7 ms·

Hey @dochtmann :) Isn't rustls [1] also built on very unsafe groundwork? Namely ring [2], which, according to github, contains 47.3% Assembly and some C as wel

by erdii 5y ago

Hey @dochtmann :) Isn't rustls [1] also built on very unsafe groundwork? Namely ring [2], which, according to github, contains 47.3% Assembly and some C as well. I'm not trolling here - we were discussing this a lot in my peer group lately. [1] https://github.com/ctz/rustls https://github.com/ctz/rustls [2] https://github.com/briansmith/ring https://github.com/briansmith/ring

volta83 5y ago
Also, ring enforces everyone to use the latest version by pruning older versions from crates.io, which means your builds will fail every time they update. Main reason I stopped using it.
- dochtman 5y ago
  That issue should be fixed in the next release. It is definitely a nuisance, but fixing it is not easy due to the assembly code involved.
- tialaramex 5y ago
  Of course, if our claim is that we want to avoid security bugs, and we accept the principle that (without some more specific definition) all bugs are security bugs, then any time ring fixes a bug we want to avoid using the old version... Now for all I know, ring has never fixed any bugs and it just loves adding new API features so that this pruning has no desirable security properties at all, but in principle I can see that this is the equivalent of the standard boilerplate Linux release text which tells you that you should update to the latest kernel because they fixed bugs. If you have a complete threat model and if you are capable of the insight needed to examine all changes and determine how they impact that model, you could successfully choose whether to upgrade based on whether a new version fixes a bug you care about. But chances are you don't have such a model and even if you did you aren't capable of the inhuman levels of insight needed, even in a language like Rust (and forgetting that we're talking about this because large parts of ring aren't even in Rust).
  - volta83 5y ago
    crates.io and the Rust community adheres to semantic versioning. If ring wants to notify me that I should update, they should send an email to a security mailing list, open a CVE, register the cve in any of the rust services to notify users with those dependencies (there are some, like crev), etc. Pruning your releases from crates.io just means that I am going to be annoyed the first time it happens, will start looking for a solution the second time it happens, and it won't happen a third time (and it didn't). If you want to wake me up a Saturday at 4 am, the world better be on fire. This is probably the only dependency I can remember as being... more than annoying, toxic. I still prevent any of my dependencies from ending up with ring as a dependency. If that shows up in our dependency tree, CI fails, and that change cannot be committed. Unfortunately, this pruning of old releases was only one of the issues with ring (there were others, like cross-compiling it wasn't easy, etc.). All in all it was a no brainer to drop it as a dependency. I don't think I've ever met a rust dev with something nice to say about `ring`. In a meetup a couple of years ago another rustacean said: "`ring` is so secure that it protects you from using it in your projects". Sums it pretty well. The library has couple of thousands of daily downloads so for the latest version, and like 25k daily downloads for other versions, so maybe things changed now.
    - briansmith 5y ago
      When I merged security fixes from BoringSSL/OpenSSL, I yanked the old versions of ring that didn't have the security fixes. I thought that was a pretty reasonable policy, however people who like to comment in these forums disagreed very loudly, so I stopped doing that. Not sure that's better, but there's less complaining. In general, my initial thinking was based too much on the assumption that people would help maintain the things that depend on ring to update them to the latest release. It turns out there's less cooperative maintenance like that than I expected.
      - jzoch 5y ago
        I loved your policy and appreciated how principled it was. People here are too harsh and most of them don't write code in Rust where regular updates are much more the norm than other communities.
- briansmith 5y ago
  That hasn't been the case for a long time, a year or more.
- CodesInChaos 5y ago
  I thought crates.io doesn't allow removal? You can yank crate versions, but that doesn't affect builds which lock a version via cargo.lock so failing builds shouldn't be an issue.
  - steveklabnik 5y ago
    They meant yanking.
- Arnavion 5y ago
  Your builds will only fail if you don't check in your lockfile.
dochtman 5y ago
It uses ring for cryptographic operations, yes. However, note that all the ASM in ring is meticulously kept up to date with BoringSSL upstream, which ring was derived from. Plus, there was pretty successful third-party security audit last year. Also, the goal is definitely to bring all of that code into Rust, unfortunately Rust lacked the features to do that safely (things like const generics).
- CameronNemo 5y ago
  >Plus, there was pretty successful third-party security audit last year. The security audit referenced by the post suggests offering EverCrypt as an optional alternative to ring. Are you going to act on the audit's recommendation, or continue to only offer ring?
- birktj 5y ago
  Could I ask why const generics would be a blocker? I see how it would help facilitate more elegant APIs as well as better stack allocated structures. However is it not possible to live without this, possibly with a slightly more clumsy design?
steveklabnik 5y ago
> Isn't rustls [1] also built on very unsafe groundwork? Depending on what you mean by "groundwork" literally everything is. Hardware doesn't obey Rust's rules, and you need to interface with hardware to get input, and do output, so literally every program will have unsafe code at the base. The key difference is that Rust gives you the tools to explicitly demarcate what is safe, and what is not, and build safe abstractions on top of (hopefully validated) unsafe foundations.
- scoutt 5y ago
  > Hardware doesn't obey Rust's rules Neither does the OS where rustls is running. I think Rust will have more adoption and more libraries like Rustls will be developed. I also think that when this happens, also more exploits targeting Rust code will exist too. I guess the excuse (sorry for using this word) will be: "In fact, the Rust code is still safe. What happened is that a pointer returned by (or used in) an underlying C library got messed up with a very clever timing attack, and somehow the pointer emerged into Rust code... etc.".
oconnor663 5y ago
One thing to keep in mind is that the low level building blocks of crypto algorithms can be relatively easy to test, compared to higher level protocol and application code. For example, a block cipher takes simple inputs, usually a couple of fixed-length arrays and maybe some integer flags. There might be a ton of assembly under the covers, but that assembly isn't responsible for reasoning about pointer lifetimes or parsing data formats or any of the usual things that tend to trip up unsafe code. (Like a TLS implementation!) Instead, the block cipher is a pure mathematical function of those inputs, and that makes it relatively easy to come up with a set of test vectors that cover the function. This also means that the C code and Rust code for the same block cipher tend to look very similar. Now there definitely are some tricky requirements in crypto code that application code doesn't need to deal with, like constant-time requirements. But auditing for those isn't really any harder in assembly or C than it is in Rust. In the end, porting these sorts of core crypto algorithms from C to Rust tends to be more interesting from a build systems and tooling perspective than from a correctness perspective.
briansmith 5y ago
The goal of the ring project is to be much safer than OpenSSL without any notable decrease in performance. That is, my goal is to give you memory safety "for free" if you switch from OpenSSL/BoringSSL to ring. In some cases it is better than free because we end up being faster. The assembly code in ring is some of the most heavily-tested code in the world. It's fuzzed pretty much continuously in various projects that use it, and a bunch of testing has been done on it. It is from BoringSSL, and much of it is shared with OpenSSL and/or Linux kernel. As we are able to replace the assembly code with safer code, we'll continue to do so, just like we've replaced most of the C code with which we started.
- fnord77 5y ago
  thank you for your work in this. we've been using rust-tls/ ring for some time now in our product.
baby 5y ago
Had the same thought the other day: https://cryptologie.net/article/520/cryptography-and-assembly-code/ https://cryptologie.net/article/520/cryptography-and-assembl... Not a fan of assembly for cryptographic code.

by erdii 5y ago

volta83 5y ago

Also, ring enforces everyone to use the latest version by pruning older versions from crates.io, which means your builds will fail every time they update. Main reason I stopped using it.

dochtman 5y ago
That issue should be fixed in the next release. It is definitely a nuisance, but fixing it is not easy due to the assembly code involved.
tialaramex 5y ago
Of course, if our claim is that we want to avoid security bugs, and we accept the principle that (without some more specific definition) all bugs are security bugs, then any time ring fixes a bug we want to avoid using the old version... Now for all I know, ring has never fixed any bugs and it just loves adding new API features so that this pruning has no desirable security properties at all, but in principle I can see that this is the equivalent of the standard boilerplate Linux release text which tells you that you should update to the latest kernel because they fixed bugs. If you have a complete threat model and if you are capable of the insight needed to examine all changes and determine how they impact that model, you could successfully choose whether to upgrade based on whether a new version fixes a bug you care about. But chances are you don't have such a model and even if you did you aren't capable of the inhuman levels of insight needed, even in a language like Rust (and forgetting that we're talking about this because large parts of ring aren't even in Rust).
- volta83 5y ago
  crates.io and the Rust community adheres to semantic versioning. If ring wants to notify me that I should update, they should send an email to a security mailing list, open a CVE, register the cve in any of the rust services to notify users with those dependencies (there are some, like crev), etc. Pruning your releases from crates.io just means that I am going to be annoyed the first time it happens, will start looking for a solution the second time it happens, and it won't happen a third time (and it didn't). If you want to wake me up a Saturday at 4 am, the world better be on fire. This is probably the only dependency I can remember as being... more than annoying, toxic. I still prevent any of my dependencies from ending up with ring as a dependency. If that shows up in our dependency tree, CI fails, and that change cannot be committed. Unfortunately, this pruning of old releases was only one of the issues with ring (there were others, like cross-compiling it wasn't easy, etc.). All in all it was a no brainer to drop it as a dependency. I don't think I've ever met a rust dev with something nice to say about `ring`. In a meetup a couple of years ago another rustacean said: "`ring` is so secure that it protects you from using it in your projects". Sums it pretty well. The library has couple of thousands of daily downloads so for the latest version, and like 25k daily downloads for other versions, so maybe things changed now.
  - briansmith 5y ago
    When I merged security fixes from BoringSSL/OpenSSL, I yanked the old versions of ring that didn't have the security fixes. I thought that was a pretty reasonable policy, however people who like to comment in these forums disagreed very loudly, so I stopped doing that. Not sure that's better, but there's less complaining. In general, my initial thinking was based too much on the assumption that people would help maintain the things that depend on ring to update them to the latest release. It turns out there's less cooperative maintenance like that than I expected.
    - jzoch 5y ago
      I loved your policy and appreciated how principled it was. People here are too harsh and most of them don't write code in Rust where regular updates are much more the norm than other communities.
briansmith 5y ago
That hasn't been the case for a long time, a year or more.
CodesInChaos 5y ago
I thought crates.io doesn't allow removal? You can yank crate versions, but that doesn't affect builds which lock a version via cargo.lock so failing builds shouldn't be an issue.
- steveklabnik 5y ago
  They meant yanking.
Arnavion 5y ago
Your builds will only fail if you don't check in your lockfile.

dochtman 5y ago

It uses ring for cryptographic operations, yes. However, note that all the ASM in ring is meticulously kept up to date with BoringSSL upstream, which ring was derived from. Plus, there was pretty successful third-party security audit last year. Also, the goal is definitely to bring all of that code into Rust, unfortunately Rust lacked the features to do that safely (things like const generics).

CameronNemo 5y ago
>Plus, there was pretty successful third-party security audit last year. The security audit referenced by the post suggests offering EverCrypt as an optional alternative to ring. Are you going to act on the audit's recommendation, or continue to only offer ring?
birktj 5y ago
Could I ask why const generics would be a blocker? I see how it would help facilitate more elegant APIs as well as better stack allocated structures. However is it not possible to live without this, possibly with a slightly more clumsy design?

steveklabnik 5y ago

> Isn't rustls [1] also built on very unsafe groundwork? Depending on what you mean by "groundwork" literally everything is. Hardware doesn't obey Rust's rules, and you need to interface with hardware to get input, and do output, so literally every program will have unsafe code at the base. The key difference is that Rust gives you the tools to explicitly demarcate what is safe, and what is not, and build safe abstractions on top of (hopefully validated) unsafe foundations.

scoutt 5y ago
> Hardware doesn't obey Rust's rules Neither does the OS where rustls is running. I think Rust will have more adoption and more libraries like Rustls will be developed. I also think that when this happens, also more exploits targeting Rust code will exist too. I guess the excuse (sorry for using this word) will be: "In fact, the Rust code is still safe. What happened is that a pointer returned by (or used in) an underlying C library got messed up with a very clever timing attack, and somehow the pointer emerged into Rust code... etc.".

oconnor663 5y ago

One thing to keep in mind is that the low level building blocks of crypto algorithms can be relatively easy to test, compared to higher level protocol and application code. For example, a block cipher takes simple inputs, usually a couple of fixed-length arrays and maybe some integer flags. There might be a ton of assembly under the covers, but that assembly isn't responsible for reasoning about pointer lifetimes or parsing data formats or any of the usual things that tend to trip up unsafe code. (Like a TLS implementation!) Instead, the block cipher is a pure mathematical function of those inputs, and that makes it relatively easy to come up with a set of test vectors that cover the function. This also means that the C code and Rust code for the same block cipher tend to look very similar. Now there definitely are some tricky requirements in crypto code that application code doesn't need to deal with, like constant-time requirements. But auditing for those isn't really any harder in assembly or C than it is in Rust. In the end, porting these sorts of core crypto algorithms from C to Rust tends to be more interesting from a build systems and tooling perspective than from a correctness perspective.

briansmith 5y ago

The goal of the ring project is to be much safer than OpenSSL without any notable decrease in performance. That is, my goal is to give you memory safety "for free" if you switch from OpenSSL/BoringSSL to ring. In some cases it is better than free because we end up being faster. The assembly code in ring is some of the most heavily-tested code in the world. It's fuzzed pretty much continuously in various projects that use it, and a bunch of testing has been done on it. It is from BoringSSL, and much of it is shared with OpenSSL and/or Linux kernel. As we are able to replace the assembly code with safer code, we'll continue to do so, just like we've replaced most of the C code with which we started.

fnord77 5y ago
thank you for your work in this. we've been using rust-tls/ ring for some time now in our product.

baby 5y ago

Had the same thought the other day: https://cryptologie.net/article/520/cryptography-and-assembly-code/ https://cryptologie.net/article/520/cryptography-and-assembl... Not a fan of assembly for cryptographic code.