SubtleCrypto verify methods accepts mutable reference that should be immutable?

[eric-seppanen]

Describe the Bug

Some of the verify methods on SubtleCrypto take mutable references to the signature bytes. It doesn't seem desirable that a method for verifying signatures would mutate the signature bytes, so I wonder if this is a mistake?

Steps to Reproduce

1. Go to https://docs.rs/web-sys/0.3.67/web_sys/struct.SubtleCrypto.html
2. Note that some of the verify____ methods accept signature: &mut [u8]

Expected Behavior

I would expect that a signature verification would never need to mutate the signature.

Actual Behavior

Parameter is explicitly set to be mutable; git history doesn't indicate a reason why.

wasm-bindgen/crates/web-sys/src/features/gen_SubtleCrypto.rs

Line 540 in 55a7fb8

signature: &mut [u8],

Additional Context

The MDN docs don't suggest that the signature might be mutated. They don't promise it won't, so I'm just going on instinct here.

[eric-seppanen]

I notice a few other uses of &mut in SubtleCrypto methods that seem suspicious, e.g. verify_with_xxx_and_yyy_and_u8_array methods accept data: &mut [u8]. This refers to the data over which a signature should be verified; mutating the data would be quite unexpected.

[daxpedda]

See The wasm-bindgen Guide on "Type Translations in web-sys".

We can add exceptions here:

wasm-bindgen/crates/webidl/src/constants.rs

Lines 43 to 99 in 55a7fb8

	pub(crate) static IMMUTABLE_SLICE_WHITELIST: Lazy<BTreeSet<&'static str>> = Lazy::new(|| {
	BTreeSet::from_iter(vec![
	// ImageData
	"ImageData",
	// WebGlRenderingContext, WebGl2RenderingContext
	"uniform1fv",
	"uniform2fv",
	"uniform3fv",
	"uniform4fv",
	"uniform1iv",
	"uniform2iv",
	"uniform3iv",
	"uniform4iv",
	"uniformMatrix2fv",
	"uniformMatrix3fv",
	"uniformMatrix4fv",
	"uniformMatrix2x3fv",
	"uniformMatrix2x4fv",
	"uniformMatrix3x2fv",
	"uniformMatrix3x4fv",
	"uniformMatrix4x2fv",
	"uniformMatrix4x3fv",
	"vertexAttrib1fv",
	"vertexAttrib2fv",
	"vertexAttrib3fv",
	"vertexAttrib4fv",
	"bufferData",
	"bufferSubData",
	"texImage2D",
	"texSubImage2D",
	"compressedTexImage2D",
	// WebGl2RenderingContext
	"uniform1uiv",
	"uniform2uiv",
	"uniform3uiv",
	"uniform4uiv",
	"texImage3D",
	"texSubImage3D",
	"compressedTexImage3D",
	"clearBufferfv",
	"clearBufferiv",
	"clearBufferuiv",
	// WebSocket
	"send",
	// WebGPU
	"setBindGroup",
	"writeBuffer",
	"writeTexture",
	// AudioBuffer
	"copyToChannel",
	// FontFace
	"FontFace", // TODO: Add another type's functions here. Leave a comment header with the type name
	// FileSystemSyncAccessHandle and FileSystemWritableFileStream
	"write",
	])
	});

I'm happy to review a PR adding exceptions to any SubtleCrypto methods.

[eric-seppanen]

Thanks @daxpedda. I investigated all the SubtleCrypto methods and I believe they can all take shared references.

I opened PR #3797 making the change.