Deprecating fromIntegral

[Vanessa McHale]

I agree! Silently changing semantics under one’s feet may be bad, but one needn’t remove the function itself. That’s just work for library maintainers!

Cheers,
Vanessa McHale

> On Aug 9, 2020, at 10:43 PM, Carter Schonwald <carter.schonwald at gmail.com> wrote:
> 
> The real issue here isn’t fromintrgral, but that everything defaults to wrapping semantics 
> 
> Adding variants that do signaling/exceptions  and clipping Variants Of finite word/Int data types rather than just wrapping is the right path forward. 
> 
> 
> 
> On Sat, Aug 8, 2020 at 2:20 AM Herbert Valerio Riedel <hvriedel at gmail.com <mailto:hvriedel at gmail.com>> wrote:
> Btw, subtle correctness issues hiding throughout the vast monolithic
> codebase like these were part of the reason (other reasons are
> explained in https://old.reddit.com/r/haskell/comments/5lxv75/psa_please_use_unique_module_names_when_uploading/dbzegx3/ <https://old.reddit.com/r/haskell/comments/5lxv75/psa_please_use_unique_module_names_when_uploading/dbzegx3/>)
> why cryptohash/cryptonite/foundation has been banned from our
> codebases not the least because it's hopeless to get something like
> cryptonite through formal certification for security critical
> applications. At the time the author made it clear he didn't welcome
> my bug reports (later I learned the author was merely peculiar as to
> what they consider an actual bug worth reporting). And whenever I
> mentioned this in the past on reddit as a PSA, I got defensive
> reactions and disbelief from certain people who were already invested
> in the cryptonite ecosystem and I was accused of spreading unfounded
> FUD... and so I stopped bringing up this kind of "heresy" publicly.
> 
> However, as you can see in
> 
> https://hackage.haskell.org/package/cryptohash-sha256/changelog <https://hackage.haskell.org/package/cryptohash-sha256/changelog>
> 
> this particular 32-bit overflow issue was one of the critical bugfixes
> I ran into and repaired in the very first release right after the
> initial-fork-release back in 2016. It's astonishing it took over 4
> years for this bug to keep lingering in cryptonite/cryptohash before
> it was detected. You'd expect this to have been detected in code
> audits performed by Haskell companies that actively promote the use of
> cryptonite early on.
> 
> On Sat, Aug 8, 2020 at 5:09 AM Niklas Hambüchen via Libraries
> <libraries at haskell.org <mailto:libraries at haskell.org>> wrote:
> >
> > Today I found another big bug caused by `fromIntegral`:
> >
> >     https://github.com/haskell-crypto/cryptonite/issues/330 <https://github.com/haskell-crypto/cryptonite/issues/330>
> >
> > Incorrect hashes for all hash algorithms beyond 4 GiB of input. SHA hash collisions in my productions system.
> >
> > Restating what I said there:
> >
> > * Until we deprecate fromIntegral, Haskell code will always be subtly wrong and never be secure.
> > * If we don't fix this, people will shy away from using Haskell for serious work (or learn it the hard way). Rust and C both do this better.
> > * If the authors of key crypto libraries fall for these traps (no blame on them), who can get it right? We should remove the traps.
> >
> > The wrong code,
> >
> >     hashInternalUpdate ctx d (fromIntegral $ B.length b)
> >
> > exists because it simply does not look like wrong code. In contrast,
> >
> >     hashInternalUpdate ctx d (fromIntegralWrapping $ B.length b)
> >
> > does look like wrong code and would make anyone scrolling by suspicious.
> >
> > We can look away while continuing to claim that Haskell is a high-correctness language, or fix stuff like this and make it one.
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