Enabling some wasm-bindgen tests in ring

I was recently digging into compiling a rust crate that relies on ring into wasm. It is a small cryptography library with over 7 million downloads to date. While I could compile the code successfully, I ran into some errors that I reproduced in this PR. First I added a few wasm-bindgen tests by adding the appropriate feature flags. Then I ran the tests to get the same errors I was seeing in my own rollup project.

% wasm-pack test --firefox --headless --  --test ed25519_tests
[INFO]: 🎯  Checking for the Wasm target...
   Compiling ring v0.16.19 (/Users/amiyaguchi/Work/ring)
    Finished dev [unoptimized + debuginfo] target(s) in 1.86s
[INFO]: ⬇️  Installing wasm-bindgen...
    Finished test [unoptimized + debuginfo] target(s) in 0.05s
     Running target/wasm32-unknown-unknown/debug/deps/ed25519_tests-af557e71142febbd.wasm
Set timeout to 20 seconds...
Running headless tests in Firefox on `http://127.0.0.1:62602/`
Try find `webdriver.json` for configure browser's capabilities:
Not found
Failed to detect test as having been run. It might have timed out.
output div contained:
    Loading scripts...

driver status: signal: 9
driver stdout:
    1611356824151       geckodriver     INFO    Listening on 127.0.0.1:62602
    1611356824255       mozrunner::runner       INFO    Running command: "/Applications/Firefox.app/Contents/MacOS/firefox-bin" "--marionette" "-headless" "-foreground" "-no-remote" "-profile" "/var/folders/q6/m7bqqf2n05l5dvng72_xvvlw0000gn/T/rust_mozprofileZY7YL3"
    console.warn: SearchSettings: "get: No settings file exists, new profile?" (new Error("", "(unknown module)"))
    1611356825619       Marionette      INFO    Listening on port 62606
    1611356845909       Marionette      INFO    Stopped listening on port 62606

driver stderr:
    *** You are running in headless mode.
    JavaScript error: http://127.0.0.1:62601/wasm-bindgen-test, line 1: TypeError: Error resolving module specifier “env”. Relative module specifiers must start with “./”, “../” or “/”.

Error: some tests failed
error: test failed, to rerun pass '--test ed25519_tests'
Error: Running Wasm tests with wasm-bindgen-test failed
Caused by: failed to execute `cargo test`: exited with exit code: 1
  full command: "cargo" "test" "--target" "wasm32-unknown-unknown" "--test" "ed25519_tests"

To get a better understanding of what the missing imports are, we can take a look at the the textual representation of the generated wasm bytcode (better known as wat). Here we use the wasm2wat utility provided by wabt.

% wasm2wat target/wasm32-unknown-unknown/debug/deps/ed25519_tests-af557e71142febbd.wasm | grep '(import "env"'
  (import "env" "GFp_x25519_ge_scalarmult_base" (func $GFp_x25519_ge_scalarmult_base (type 5)))
  (import "env" "GFp_x25519_sc_muladd" (func $GFp_x25519_sc_muladd (type 4)))
  (import "env" "GFp_x25519_sc_reduce" (func $GFp_x25519_sc_reduce (type 3)))
  (import "env" "GFp_x25519_sc_mask" (func $GFp_x25519_sc_mask (type 3)))
  (import "env" "GFp_x25519_fe_neg" (func $GFp_x25519_fe_neg (type 3)))
  (import "env" "GFp_x25519_ge_frombytes_vartime" (func $GFp_x25519_ge_frombytes_vartime (type 11)))
  (import "env" "GFp_x25519_fe_invert" (func $GFp_x25519_fe_invert (type 5)))
  (import "env" "GFp_x25519_fe_mul_ttt" (func $GFp_x25519_fe_mul_ttt (type 6)))
  (import "env" "GFp_x25519_fe_tobytes" (func $GFp_x25519_fe_tobytes (type 5)))
  (import "env" "GFp_x25519_fe_isnegative" (func $GFp_x25519_fe_isnegative (type 18)))
  (import "env" "GFp_x25519_ge_double_scalarmult_vartime" (func $GFp_x25519_ge_double_scalarmult_vartime (type 4)))
  (import "env" "LIMBS_less_than" (func $LIMBS_less_than (type 12)))
  (import "env" "LIMBS_are_zero" (func $LIMBS_are_zero (type 11)))

These look like they’re missing because the relevant C code is not being built. I changed a line in the build file and added a flag that enables the wasm32 target.

 % wasm-pack test --firefox --headless --  --features wasm32_c --test ed25519_tests
[INFO]: 🎯  Checking for the Wasm target...
   Compiling ring v0.16.19 (/Users/amiyaguchi/Work/ring)
    Finished dev [unoptimized + debuginfo] target(s) in 2.06s
[INFO]: ⬇️  Installing wasm-bindgen...
   Compiling ring v0.16.19 (/Users/amiyaguchi/Work/ring)
    Finished test [unoptimized + debuginfo] target(s) in 1.17s
     Running target/wasm32-unknown-unknown/debug/deps/ed25519_tests-8b475dcb9ffa54de.wasm
Set timeout to 20 seconds...
Running headless tests in Firefox on `http://127.0.0.1:63084/`
Try find `webdriver.json` for configure browser's capabilities:
Not found
running 6 tests

test ed25519_tests::ed25519_test_public_key_coverage ... ok
test ed25519_tests::test_ed25519_from_pkcs8 ... ok
test ed25519_tests::test_ed25519_from_pkcs8_unchecked ... ok
test ed25519_tests::test_ed25519_from_seed_and_public_key_misuse ... ok
test ed25519_tests::test_signature_ed25519_verify ... ok
test ed25519_tests::test_signature_ed25519 ... ok

test result: ok. 6 passed; 0 failed; 0 ignored

With this, the tests pass for this particular modules. Unfortunately, this doesn’t work for other failing tests in the repository because they rely on generated assembly code instead of C. I hear there are side-channel concerns of using cryptography compiled to wasm too, but I’m not too familiar with the details. Regardless, it’s promising to see the progress of wasm as a target for compiled languages like rust.