crypto is not available inside AudioWorkletGlobalScope

[pioug]

Emscripten generates worklet-targeted bundle that crashes in AudioWorkletGlobalScope when random bytes are requested.

Repro: https://github.com/pioug/emscripten-worklet-randomfill

In the repro, a C call to getentropy() goes through Emscripten’s generic randomFill path, which emits a crypto.getRandomValues(...) call but crypto is not available in the audio worklet, so the generated bundle throws ReferenceError: crypto is not defined.

Might be a duplicate of #13224, but my findings point to a breaking change in 5a8d9e5 from Dec 31, 2024.

Version of emscripten/emsdk:
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 5.0.3-git
clang version 23.0.0git
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /opt/homebrew/Cellar/emscripten/5.0.3/libexec/llvm/bin

[sbc100]

Yes, this is looks like its probably a duplicate of #13224.

I'm curious about your findings pointing to #23247 though since that seems related to generate_uuid. Is your program calling generate_uuid?

[pioug]

@sbc100 Ah yes, my original app uses generate_uuid. The repro highlights the usage of crypto in the worklet. It would be good if generate_uuid works too if it's a different code path.

Thanks for working on it!

[pioug]

@sbc100 Thanks for the quick fix! From what I understand, uuid_generate() won’t work as expected in a worklet unless we override initRandomFill. Is using a shim the recommended solution for now?

[sbc100]

Could you open a new bug for uuid_generate in a wasm worker?

I'm not really sure what the best solution would be there, since uuid_generate itself cannot fail. I guess it we can have it fall back from getentropy to just srand?