[swift-server-dev] Crypto Library

Tue Nov 8 10:55:15 CST 2016

> On 8 Nov 2016, at 17:54, Joannis Orlandos <joannis at orlandos.nl> wrote:
> 
> I think option #3 is the most viable but you seem to partially overestimate the amount of work that you'd have to put into a Swift variant to OpenSSL. LibreSSL, which does not contain a lot of legacy code, is ~200K lines of code which is a lot less than your OpenSSL figures. And in Swift we can probably be a lot more expressive in our statements so I think 180K would be a feature complete SSL implementation.
> 
> I think the FIPS compliance certification is going to be the toughest part. The API for the cryptography will have to be designed regardless of point 3 and 4 which I think would result in 150k lines of code that will have to be written specifically for point 4. It's not exactly unthinkable to write Swift Cryptography. The Vapor framework already counts 60k lines of code which is build by two people primarily but I think it's probably not worth the effort/maintenance at this scale to build a pure swift SSL implementation, at least initially.
> 
> Joannis
> 
>> On 8 Nov 2016, at 16:45, Chris Bailey via swift-server-dev <swift-server-dev at swift.org <mailto:swift-server-dev at swift.org>> wrote:
>> 
>> Whilst there's legitimate debate on the use of C vs. Swift for HTTP parsing, I think the situation for the security libraries in general is more clear. 
>> 
>> We've effectively got four choices on how to do the underlying implementation of the security APIs:
>> Use OpenSSL/LibreSSL everywhere
>> The challenge his is iOS devices, where there is no support for OpenSSL/LibreSSL. There's likely also an argument that using OpenSSL/LibreSSL will be a regressive move for macOS users vs. the Apple libraries that have been optimized for the platform. Additionally there may be a granularity issue - we'd the Apple libraries are deliberately broken into three libraries and we'd need to reflect that from OpenSSL/LibreSSL. I think that means we at least have to have a "hybrid" model of using the Apple libraries on macOS/iOS, and OpenSSL/LibreSSL elsewhere
>> Use the Apple security libraries everywhere
>> This three libraries are a significant body of work, and based on the effort required to port libdispatch to Linux, I would estimate that a considerable amount of porting work. There would then be secondary challenges on how we respond to security vulnerabilities on the new platforms, and the effort and cost of trying to get FIPS compliance for the new libraries on each platforms
>> Use a hybrid of Apple security libraries on macOS/iOS and OpenSSL/LibreSSL elsewhere
>> This leverages existing "defacto standard" libraries on each platform, where things like FIPS compliance certification already exists, and teams already have a track record of responding to security vulnerabilities. There is a challenge though on how we isolate/abstract the user away from the differences between the libraries - particularly for things like certificate handling and configuration.
>> Create a pure-Swift implementation
>> The implementation of OpenSSL is ~350K lines of code, which is a sizeable amount of function to implement, and most importantly, to get right and do rigorous security vulnerability testing for. Once done, we will then have to react rapidly to any reported vulnerabilities and do the full set of work and cost to get FIPS compliance certification.
>> 
>> For me, this points to option #3 as the most viable solution - and therefore the first that we should investigate. 
>> 
>> 
>> Chris
>> 
>> 
>> 
>> 
>> From:        Bill Abt via swift-server-dev <swift-server-dev at swift.org <mailto:swift-server-dev at swift.org>> 
>> To:        Swift Server Dev <swift-server-dev at swift.org <mailto:swift-server-dev at swift.org>> 
>> Date:        07/11/2016 18:48 
>> Subject:        Re: [swift-server-dev] Crypto Library 
>> Sent by:        swift-server-dev-bounces at swift.org <mailto:swift-server-dev-bounces at swift.org> 
>> 
>> 
>> 
>> We experimented with various different approaches when doing the lower levels of Kitura.  Ultimately, we chose to use CommonCrypto on macOS and libcrypto (from OpenSSL) on Linux for the crypto portion.  You can see the implementation (which works on both macOS and Linux) at https://github.com/IBM-Swift/BlueCryptor <https://github.com/IBM-Swift/BlueCryptor>.  As far as the securing sockets, we chose to go with Apple Secure Transport on macOS and OpenSSL on Linux.  This implementation can be found at https://github.com/IBM-Swift/BlueSSLService <https://github.com/IBM-Swift/BlueSSLService>.  The BlueCryptor package can be used by virtually Swift application.  The BlueSSLService, however, is an add-on to and dependent on BlueSocket, the underlying network layer for Kitura. 
>> 
>> In my opinion, using the Security framework on macOS is fine but to get the “beast” running on Linux may be very, very problematic.  The underlying codebase is massive and there are bits and pieces that are missing and would have to be re-implemented.  Another factor that led us to not use the Security framework was relatively sparse documentation.  CommonCrypto is a much smaller subset as is Secure Transport and the mapping between them and librcrypto and OpenSSL is much cleaner and straight forward.  Plus, as others have pointed out, an implementation taking this approach doesn’t have to worry so much about FIPS certification since the underlying platform implementation are already certified. 
>> 
>> On Nov 7, 2016, at 10:31 AM, Zach Drayer via swift-server-dev <swift-server-dev at swift.org <mailto:swift-server-dev at swift.org>> wrote: 
>> 
>> 
>> On Nov 7, 2016, at 2:45 PM, Helge Heß via swift-server-dev <swift-server-dev at swift.org <mailto:swift-server-dev at swift.org>> wrote: 
>> 
>> On 07 Nov 2016, at 13:48, Zach Drayer <zachary.drayer at gmail.com <mailto:zachary.drayer at gmail.com>> wrote: 
>> On Nov 7, 2016, at 11:20 AM, Helge Heß via swift-server-dev <swift-server-dev at swift.org <mailto:swift-server-dev at swift.org>> wrote: 
>> P.S.: As a sidenote, can’t someone (hm hm, who would come to mind?) sponsor the CryptoSwift guy to do a java.security like Security standard framework (which includes TLS)? That would be pretty cool :-) 
>> 
>> Instead: while in C, Security.framework, and CommonCrypto.framework from  are both fully open source, and battle-hardened. 
>> 
>> Do they provide a clean Linux story too? (.framework in the name kinda suggests they don’t :-)
>> 
>> Do they work with non-blocking I/O? The API read/write/handshake API suggests that they may not?
>> 
>> Looks like the approach people currently use is either Security.framework on Darwin and Open/LibreSSL on other platforms, or using OpenSSL on both. Some even forking OpenSSL. 
>> 
>> Good question. My assumption was “yes, of course”, but, it looks like that isn’t correct in the way I expected it to be. 
>> 
>> CommonCrypto looks like it makes some assumptions about Darwin (e.g. importing TargetConditionals or Availability.h) but looking one level deeper, we find `corecrypto` at the bottom of https://developer.apple.com/security/ <https://developer.apple.com/security/> that is also open source, is what underlies CommonCrypto + Security, and, has the necessary `#if`s to build on Linux (even if it is lacking a Makefile at the moment). 
>> 
>> This is one of (rare) the cases where practicality and strongly deferring to the thing that already exists seem to be the safe option (and not only in opinion). 
>> 
>> This is all true, but then someone also thought it makes sense to have Security.framework despite OpenSSL being available. Or java.security. Or Windows SChannel/security. Just saying …
>> 
>> The thing which makes a pure-Swift thing attractive is that it would be cross platform and readily available. The C libs are really diverse between the platforms and forking OpenSSL into an embedded module is not exactly 1337 either. 
>> 
>> No disagreement that there are a number of benefits to living in a pure Swift world, but as mentioned earlier: this may not be possible yet. There is little point in providing a security/crypto library that can’t be trusted — and with cryptography, the requirement for trust extends far beyond “does it compile?, or even “do all the tests pass?”. We don’t want another heartbleed, or a predictable PRNG (https://github.com/g0tmi1k/debian-ssh <https://github.com/g0tmi1k/debian-ssh>). 
>> 
>> But, I don’t know. Maybe the solution isn’t corecrypto, but is LibreSSL/OpenSSL, or, something else. Maybe adding compiler support for Crypto tasks is already done (or easy enough to do) and my argument is moot. Thats why we’re having this discussion, right? 
>> 
>> Anyway, (to me) the more interesting questions that we can talk about are over API:
>> - what constructs are needed (bignum? secure random? hmac? checksumming? key derivation? wrapping a socket in a big TLS hug?) 
>> 
>> The thing I need and which is a little awkward to get is async TLS, both client and server. I started working on an OpenSSL BIO and see whether I can get that running on top of GCD, looks like it should be possible.
>> 
>> For the hashes that I needed so far (just MD5 and SHA1) I use CryptoSwift. 
>> 
>> These seem like excellent use cases to consider, thank you for bringing them up! Reading through https://swift.org/server-apis/ <https://swift.org/server-apis/>, the section on "Security and Encryption”, definitely indicates that this is the right place to talk about these needs. 
>> 
>> -z 
>> 
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