Problem at use secp256k1 0.22.1 with wasm

[josediegorobles]

Describe the bug
I have the error that i describe later with last release of rust-bitcoin ( no problem with previous versions).

Build environment

OS+version: 20.04.01
Rust/Cargo version: 1.61.0
Rust/Cargo target: wasm32-unknown-unknown

That's the error:

Uncaught (in promise) RuntimeError: unreachable
at __rust_start_panic (67d29ce8a8f7d806078e.module.wasm:0xc6d5d8)
at rust_panic (67d29ce8a8f7d806078e.module.wasm:0xc55f4c)
at std::panicking::rust_panic_with_hook::he2a025723e105e28 (67d29ce8a8f7d806078e.module.wasm:0x960d29)
at std::panicking::begin_panic_handler::{{closure}}::hd9f8c213ec91b9d5 (67d29ce8a8f7d806078e.module.wasm:0xa6ac56)
at std::sys_common::backtrace::__rust_end_short_backtrace::h6efd730283875809 (67d29ce8a8f7d806078e.module.wasm:0xc6c185)
at rust_begin_unwind (67d29ce8a8f7d806078e.module.wasm:0xc16d18)
at core::panicking::panic_fmt::hb02133958c1e7d35 (67d29ce8a8f7d806078e.module.wasm:0xc24531)
at rand::rngs:thread:THREAD_RNG_KEY::__init::{{closure}}::ha2ad45ff6630e75f (67d29ce8a8f7d806078e.module.wasm:0xa55aef)
at core::result::Result<T,E>::unwrap_or_else::hdc727ae752f97c76 (67d29ce8a8f7d806078e.module.wasm:0x73eae4)
at rand::rngs:thread:THREAD_RNG_KEY::__init::hfb75fbbba2c214fb (67d29ce8a8f7d806078e.module.wasm:0x80efe3)

If anyone wants to repro, check out this commit:
bitmask-stack/bitmask-core@76e83c9

[apoelstra]

Hmm, I worry that this grounds out in the rand crate.

Your backtrace doesn't obviously go through our library ... are you able to re-run with RUST_BACKTRACE=1 or something to get more information?

[josediegorobles]

Yeah most probably is in that crate.
It doesn't change anything with RUST_BACKTRACE=1 but i know by debugging that the fail is here:
let secp = Secp256k1::new();

Thanks.

[Kixunil]

I believe you have to enable debug symbols or just avoid --release if debugging speed/size is acceptable.

[apoelstra]

I seem to remember something related to rerandomization and static contexts and wasm...

[josediegorobles]

I'm using wasm-pack build

[Kixunil]

I suspect that wasm (Rust support of wasm?) doesn't support thread locals, but couldn't find anything reasonable on the topic yet.

[apoelstra]

Okay, in #385 we started doing rerandomization on context creation ... this linked to #346 (comment). I need to read further but I think this old discussion is relevant.

[apoelstra]

Okay it looks like this was "resolved" in #407 where we added the global-context-less-secure feature, along with a huge comment in our Cargo.toml saying that you need this for WASM.

@josediegorobles can you try enabling that feature and see if it fixes your problem?

The issue here is that the rand crate panics when trying to obtain randomness, which is insane and antisocial but I guess we decided to live with it.

[josediegorobles]

Ok. The issue is that all is working great with previous versions (bitcoin 0.27 - sec256k1 0.20.2).
I will try global-context-less-secure, thanks

[Kixunil]

which is insane and antisocial

What would you like it to do? It doesn't seem there's an obvious better solution.

[apoelstra]

@Kixunil it could return a result. Or they could provide an alternate method that would just return bad randomness.

I think for now we should disable this line of code when compiling for wasm.

[josediegorobles]

@apoelstra how can i pass the feature to secp256k1 if i'm using it throught the rust-bitcoin crate?