feat(store-key): Add a feature flag to enable WASM support

crates/matrix-store-key/Cargo.toml

@@ -6,10 +6,14 @@ description = "Helpers for encrypted storage keys for the Matrix SDK"
 repository = "https://github.com/matrix-org/matrix-rust-sdk"
 license = "Apache-2.0"
 
+[features]
+js = ["getrandom/js"]
+
 [dependencies]
 blake3 = "1.3.1"
 chacha20poly1305 = { version = "0.9.0", features = ["std"] }
 displaydoc = "0.2"
+getrandom = { version = "0.2.5", optional = true }
 hmac = "0.12.1"
 pbkdf2 = "0.10.1"
 rand = "0.8.4"

crates/matrix-store-key/README.md

@@ -70,3 +70,12 @@ used for non-Matrix specific data users need to ensure:
 1. That individual values are chunked, otherwise decryption might be succeptible
    to a DOS attack.
 2. The `StoreKey` is periodically rotated/rekeyed.
+
+# WASM support
+
+This crate relies on the `random` and `getrandom` crates which don't support
+WASM automatically.
+
+Either turn the `js` feature on directly on this crate or depend on `getrandom`
+with the `js` feature turned on. More info can be found in the [`getrandom`
+docs](https://docs.rs/getrandom/latest/getrandom/index.html#webassembly-support).