Each stub is replaced with a thin wrapper over libsodium-wrappers-sumo:
* init() awaits sodium.ready
* toBase64 / toBase64URL / fromBase64 use sodium's base64 variants;
fromBase64 tries all four (standard, standard-no-pad, URL-safe,
URL-safe-no-pad) so callers don't have to know which form Ente
delivered
* deriveKEK is sodium.crypto_pwhash with ALG_ARGON2ID13 and 32-byte
output
* deriveLoginSubkey is sodium.crypto_kdf_derive_from_key(32, 1,
'loginctx', kek).slice(0, 16) per the upstream Ente clients
* decryptBox is sodium.crypto_secretbox_open_easy
* decryptSealed is sodium.crypto_box_seal_open
* initStreamPull / pullStreamChunk wrap the secretstream pull API,
throwing on authentication failure rather than returning false
All 32 tests pass; make check is green.
Tests for the entire crypto/ public surface, written against the API
shape declared in the README. The accompanying src/crypto/ modules are
stubs that throw 'not implemented' so the test files compile and tests
fail with clear errors rather than module-not-found.
Tests cover:
* init() resolves and is idempotent
* fromBase64 / toBase64 / toBase64URL round-trips, including URL-safe
input with stripped padding (the form Ente uses for auth tokens)
* deriveKEK matches sodium.crypto_pwhash with Argon2id parameters
* deriveLoginSubkey matches sodium.crypto_kdf_derive_from_key with
subkey id 1 and ctx 'loginctx', truncated to 16 bytes
* decryptBox round-trips, rejects tampering, wrong key, wrong nonce
* decryptSealed round-trips, rejects wrong keypair and tampering
* Secretstream pull decrypts multi-chunk streams in order, exposes
per-chunk tags, rejects tampering, wrong key, and out-of-order chunks
* Constants STREAM_CHUNK_SIZE (4 MiB) and STREAM_CHUNK_OVERHEAD (17)
Tests are commented to serve as the canonical API documentation per the
README development workflow policy. Verified: 29 tests fail (red), 3
trivial constant tests pass; lint and fmt-check are green.
eslint.config.mjs is updated to honour the leading-underscore convention
for intentionally unused parameters (the stubs).
