Sandbox::https://github.com/hacl-star/hacl-star/pull/803

msprotz · 2023-04-14T17:21:36Z

Hot on the heels of #800, this PR adds a new instance of the streaming functor specifically for algorithms of the Keccak family.

Background

The streaming functor currently comes in several flavors of agility (the ability to parameterize the code over a choice of algorithm or implementation).

Static agility: the instance is generic, but must be specialized at compile-time before extraction. Examples: Poly1305 (generic of the choice of implementation: 32, 128 and 256), Blake2 (generic over both algorithm and implementation: Blake2b/32, Blake2b/256, Blake2s/32, Blake2s/128), and MD (generic over the choice of algorithm: MD5, SHA1, SHA2). Concretely, you have:

inline_for_extraction noextract
let hacl_md (a:alg)// : block unit =
  =
  Block

and you do:

let update_512 = F.update (hacl_md SHA2_512) (G.hide ()) ((state_t SHA2_512).s ()) (G.erased unit)

Things are done this way because SHA2_512 and SHA2_256 have different state representations, so you can't extract to Low* a type of the form lbuffer (if SHA2_256 then uint32 else if SHA2_512 uint64) -- you have to pick either one at compile time and rely on F* to reduce it to either lbuffer uint32 or lbuffer uint64 before sending it over to krml.

Runtime agility: the state is an inductive, indexed by the agility parameter type state a = | SHA2_256: lbuffer uint32 ... -> state SHA2_256 | SHA2_512: lbuffer uint64 ... -> state SHA2_512. This style compiles to C (as a tagged union), but creates more representation overhead and an extra level of indirection because now you have a reference to a state a that contains an lbuffer. No need to do compile-time specialization: the user picks at run-time which algorithm they want to run with.

This PR

This PR introduces a new style that is somewhat in-between the two, relying on the observation that all algorithms from the Keccak family share the same state representation.

For this streaming functor, the state becomes sha3_alg & lbuffer uint64 25, i.e. no need to have an inductive with different types under each branch.

Making it work required quite some delicate surgery, notably:

using a singleton type for the left component of the pair to tie it to the index, in order to justify that operations like copy really do operate on the same algorithm
judicious use of erasure, to enforce statically the fact that the instance of the streaming functor never requires the user to provide the algorithm at run-time (since it's already stored internally)
a few plays on types in Hacl.Hash.SHA3 to explain to F* that a Low*-compatible, monomorphic type that talks about lbuffer uint64 25 is really a refinement of the generic type expected by callers
a few touch-ups to make sure quality code is generated for the various functions
add a notion of variable output length to the streaming functor (for shake)
and many more little things.

I'm probably going to push a few cleanups but wanted to get this out to start the work of getting it green and gathering feedback. The F* code can be reviewed. ~~The C code needs (obviously) to be fixed up because there are large diffs that shouldn't be there.~~ The C code is ready, too.

This is the second half of the work required for adding SHA3 to python/cpython#99108

If the key is kept all the way until the end, the update_multi and update_last functions may now receive the key, too.

Using a singleton type, I actually managed to pair up the algorithm with a non-agile state type (that extracts to C). Using a few tricks related to erasure (and marking a few more functions erased), I was able to capture statically the fact that many Keccak streaming functions don't need the client to pass the algorithm, as the information is either stored internally, or irrelevant.

msprotz · 2023-04-14T17:59:54Z

+      a, B.malloc r (Lib.IntTypes.u64 0) 25ul)
+    (* free: *) (fun _ (_, s) ->
+      B.free s)
+    (* copy: *) (fun _ (a, s_src) (a', s_dst) ->


this is where the singleton type is needed: because the two types share the same index (as imposed by the type signature of copy), we can conclude that the two values are exactly the same, meaning that a and a' are identical

R1kM

The F* changes look reasonable so far. I'll have a look at the generated C code once you're done with the clean-up.

github-actions · 2023-04-14T22:29:43Z

[CI] Important!
The code in dist/gcc-compatible, dist/msvc-compatible, and dist/wasm
is tested on cryspen/hacl-packages.
dist is not automatically re-generated, be sure to do it manually.
(A fresh snapshot can also be downloaded from CI.)
Then check the following tests before merging this PR.
Always check the latest run, it corresponds to the most recent version of this branch.
All jobs are expected to be successful.
In some cases manual intervention is needed. Please ping the hacl-packages maintainers.

Build, Test, Benchmark: Build on Linux (x86, x64), Windows (x86, x64), MacOS (x64, arm64), s390x, Android (arm64) and test on Linux (x86, x64), Windows (x86, x64), MacOS (x64).
Performance Regression Tests: Navigate to the terminal output in “Run benchmarks”. The comparison with the main branch will be at the bottom. The run fails if the performance regresses too much.
OCaml bindings: Build & Tests
JS bindings: Build & Tests
Rust bindings: Build & Tests

msprotz · 2023-04-15T04:59:04Z

@R1kM I think the C code is where I want it to be. I'm still wrestling with CI.

…st/hacl-star into protz_keccak_streaming

R1kM · 2023-04-17T16:30:23Z

+    uint8_t *block = blocks + i * block_len(a);
+    Hacl_Impl_SHA3_absorb_inner(block_len(a), block, s);
+  }
+  uint8_t *last = blocks + n_blocks * block_len(a);


Why do we need this last statement?

https://github.com/hacl-star/hacl-star/blob/main/lib/Lib.Buffer.fst#L351

Not sure how to get rid of it. Maybe another peephole optimization in krml?

the reason unused variable elimination doesn't kick in is because we don't know that block_len is pure, and therefore can be eliminated

Aymeric and I talked about this, and the conclusion is that we'd need repeat_blocks_multi (with a suitable precondition that length input % block_length == 0). I believe we don't have this combinator yet, but @polubelova can confirm.

that's correct, we don't have loop_blocks_multi in Lib.Buffer.fst

ok no problem let me add it it's not a big deal

msprotz · 2023-04-17T18:08:13Z

I addressed all of the low-hanging fruits. The rest is somewhat longer-ish discussions, so please feel free to file separate issues so that we don't lose track of your remarks. Thanks for the review!

…types

msprotz · 2023-04-18T17:37:39Z

@franziskuskiefer bringing your attention to this as it changes the SHA3 streaming API to a more general one for all Keccak constructions -- you now need to pass your choice of algorithm at initialization-time, and the finish function now has two modes, depending on whether the initial choice of algorithm is shake (variable length output) or not (fixed length output solely dependent on the variant of sha3 picked)$:

finish(st, dst, 0) when not (is_shake st) -- the user MUST pass 0 to indicate that they are aware that this is a non-variable-length algorithm
finish(st, dst, l) whwen is_shake st -- the user MUST pass a non-zero length l

The API is defensive and will return a non-zero error code to indicate failure if the user fails to obey the MUST clauses.

The alternative design is to have two functions, one called finish, and another one called finish_shake, where only the latter takes a length argument. I don't have strong feelings either way, so opinions welcome.

franziskuskiefer · 2023-05-03T11:08:10Z

@franziskuskiefer bringing your attention to this as it changes the SHA3 streaming API to a more general one for all Keccak constructions

Looks like didn't actually respond here 😬 Here my thoughts.

I think the implicit switch in the finish through the argument is not great.
Why do you need an argument in the finish function? When you made your choice in the init, this shouldn't be necessary, i.e. you can put in the length there too.
Using 0/1 arguments are always bad, because the caller doesn't know what they stand for. The better approach would be to define a SHAKE and SHA (or whatever else), that should be used.
Looking at the previous points, adding a separate function might be the easiest though.

msprotz · 2023-05-03T17:32:39Z

I've implemented the requested changes. Can either one of @franziskuskiefer or @karthikbhargavan mark this as approved? I'd like to land this soon, it's been a while

karthikbhargavan

Thanks, much needed changes.

franziskuskiefer

Thanks

msprotz added 6 commits April 12, 2023 13:54

Part 1: extend the streaming functor

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If the key is kept all the way until the end, the update_multi and update_last functions may now receive the key, too.

omg it works

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Most important file

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Fix various files, and try to beef up a proof in HPKE (sigh)

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And all is well that ends well. Verifies & compiles.

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msprotz requested a review from a team as a code owner April 14, 2023 17:21

msprotz added 3 commits April 14, 2023 10:51

C code quality

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C code quality

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Merge remote-tracking branch 'origin/main' into protz_keccak_streaming

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msprotz commented Apr 14, 2023

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Base automatically changed from protz_sha3_agile to main April 14, 2023 18:58

msprotz added 3 commits April 14, 2023 13:49

Prettier C code

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Better naming

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Take into account review comments from #800

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R1kM reviewed Apr 14, 2023

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Comment thread code/hash/Hacl.Hash.SHA3.fsti Outdated

Comment thread code/streaming/Hacl.Streaming.Keccak.fst

Code quality improvements, remarks from Aymeric

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msprotz added 7 commits April 14, 2023 15:43

FUrther C code cleanups

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Further C code improvements

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Final C code quality tweak

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Code quality

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final c code quality tweaks

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hints

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Try to strengthen proof

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R1kM and others added 3 commits April 15, 2023 13:07

Merge branch 'main' into protz_keccak_streaming

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Merge remote-tracking branch 'origin/main' into protz_keccak_streaming

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Merge branch 'protz_keccak_streaming' of pro.github.com:project-evere…

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…st/hacl-star into protz_keccak_streaming

R1kM reviewed Apr 17, 2023

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code quality

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msprotz added 4 commits April 17, 2023 11:28

Add missing function

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Missing function

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Missing function

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Kill several VLAs in SHA3

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msprotz mentioned this pull request Apr 17, 2023

gh-99108: Initial import of HACL-SHA3 into Python python/cpython#103597

Merged

Aymeric's suggestion: hash alg type belongs better in hacl_streaming_…

a41202d

…types

msprotz requested review from franziskuskiefer and karthikbhargavan April 18, 2023 17:34

R1kM approved these changes Apr 19, 2023

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msprotz added 3 commits April 20, 2023 08:37

Unused variable elimination

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Merge remote-tracking branch 'origin/main' into protz_keccak_streaming

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Kick CI

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msprotz added 2 commits May 3, 2023 10:27

Switch to a cleaner API per discussions on the PR

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C dist

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Merge remote-tracking branch 'origin/main' into protz_keccak_streaming

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karthikbhargavan approved these changes May 3, 2023

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franziskuskiefer approved these changes May 3, 2023

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Kick CI

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msprotz enabled auto-merge May 3, 2023 17:45

msprotz added 4 commits May 3, 2023 11:08

Try hints

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Hints & dist

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rlimit

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Try again

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msprotz merged commit ab3499d into main May 3, 2023

msprotz deleted the protz_keccak_streaming branch May 3, 2023 23:30

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