symmetric_state_clone not implemented for wasi-crypto-guest

[rjzak]

proposal_symmetric.witx defines a function symmetric_state_clone which isn't implemented in rust/src/symmetric/low/state.rs in the binding crate. This causes compilation errors for Wasmtime when trying to use the latest wasi-crypto, which would be nice to use to leverage the P384 support and updated RustCrypto dependencies.

I'd work on this myself, but I don't understand how the data types defined in the witx format translate into Rust types, or the members of the raw::SymmetricState object.

I commended it out in the witx file for now, but otherwise it generates this error:

error[E0046]: not all trait items implemented, missing: `symmetric_state_clone`
 --> crates/wasi-crypto/src/wiggle_interfaces/symmetric.rs:6:1
  |
6 |   impl super::wasi_ephemeral_crypto_symmetric::WasiEphemeralCryptoSymmetric for WasiCryptoCtx {
  |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `symmetric_state_clone` in implementation
  |
 ::: crates/wasi-crypto/src/wiggle_interfaces/mod.rs:3:1
  |
3 | / wiggle::from_witx!({
4 | |     witx: ["$CARGO_MANIFEST_DIR/spec/witx/wasi_ephemeral_crypto.witx"],
5 | | });
  | |__- `symmetric_state_clone` from trait

[jedisct1]

That function was recently added to the spec, but implementations may be a little bit behind, so you need to use a previous version of the witx files.

I'm going to update the Rust implementation; looks like sonder-joker will be handling this for wasmedge.

[sonder-joker]

That function was recently added to the spec, but implementations may be a little bit behind, so you need to use a previous version of the witx files.

I'm going to update the Rust implementation; looks like sonder-joker will be handling this for wasmedge.

I was going to implement clone and some other features for wasi-crypto-guest a few hours ago, but delayed due to some things. WasmEdge already implement symmetric_state_clone

[jedisct1]

WasmEdge already implement symmetric_state_clone

Nice!

For the rust implementation of hostcalls, I tried to implement symmetric_state_clone() but miserably lost the battle against the borrow checker. I've no idea how to do it.

Individual primitives are cloneable, but the generic SymmetricStateLike is not and I couldn't find the Rust magical incantation to make it work.

@rjzak can you help here?

[rjzak]

I'm happy to take a shot! I'm reviewing https://github.com/jedisct1/witx-codegen to see how to make sense of witx to learn about the types.

[jedisct1]

This is not really about the generated code. The current one should be fine.

But making SymmetricState or SymmetricStateLike cloneable doesn't look trivial.

[rjzak]

I'm not sure where to start since my IDE isn't able to see into anything generated from the witx files, and the witx files are lacking in data type information.

[jedisct1]

That's the joy of Rust macros. They are write-only.

[rjzak]

For the rust implementation of hostcalls, I tried to implement symmetric_state_clone() but miserably lost the battle against the borrow checker. I've no idea how to do it.

Individual primitives are cloneable, but the generic SymmetricStateLike is not and I couldn't find the Rust magical incantation to make it work.

@jedisct1 Could you submit a draft PR that I could work from? I'm not sure how to get started since it seems to all be pointers, and I'm not sure of the underlying structure.

[rjzak]

deleted

[rjzak]

Why is mutability required? Some the functions don't need to change the state, yet it seems the trait requires it.

error[E0053]: method `symmetric_state_clone` has an incompatible type for trait
   --> crates/wasi-crypto/src/wiggle_interfaces/symmetric.rs:135:30
    |
135 |     fn symmetric_state_clone(&self, state: guest_types::SymmetricState) -> Result<guest_types::SymmetricState, guest_types::CryptoErrno> {
    |                              ^^^^^
    |                              |
    |                              types differ in mutability
    |                              help: change the self-receiver type to match the trait: `self: &mut CryptoCtx`
    |
note: type in trait
   --> crates/wasi-crypto/src/wiggle_interfaces/mod.rs:3:1
    |
3   | / wiggle::from_witx!({
4   | |     witx: ["$CARGO_MANIFEST_DIR/spec/witx/wasi_ephemeral_crypto.witx"],
5   | | });
    | |__^
    = note: expected fn pointer `fn(&mut CryptoCtx, types::SymmetricState) -> Result<_, _>`
               found fn pointer `fn(&CryptoCtx, types::SymmetricState) -> Result<_, _>`
    = note: this error originates in the macro `wiggle::from_witx` (in Nightly builds, run with -Z macro-backtrace for more info)

[jedisct1]

That's what wiggle emits unconditionally. I guess the idea is that the WASI context can change with memory allocations, preemption, etc.

[jedisct1]

This is done.

Not sure why, maybe a bug was fixed in the Rust compiler or in dependencies, but the .clone() method on symmetric states works, so the symmetric_state_clone() function has been added.