Add Argon2S2K.reloadWasmModule() for manually triggering memory deallocation (#14)

Also, make `ARGON2_WASM_MEMORY_THRESHOLD_RELOAD`
a static class property, to be able to change its value.

openpgp.d.ts

@@ -942,6 +942,8 @@ export namespace enums {
 }
 
 export declare class Argon2S2K {
+  static reloadWasmModule(): void;
+  static ARGON2_WASM_MEMORY_THRESHOLD_RELOAD: number;
   constructor(config: Config);
   salt: Uint8Array;
   /** @throws Argon2OutOfMemoryError */

src/type/s2k/argon2.js

@@ -23,9 +23,26 @@ export class Argon2OutOfMemoryError extends Error {
 let loadArgonWasmModule;
 let argon2Promise;
 // reload wasm module above this treshold, to deallocated used memory
-const ARGON2_WASM_MEMORY_THRESHOLD_RELOAD = 2 << 19;
+// (cannot be declared as a simple `static` field as its not supported by Safari 14)
+let ARGON2_WASM_MEMORY_THRESHOLD_RELOAD = 2 << 19;
 
 class Argon2S2K {
+  static get ARGON2_WASM_MEMORY_THRESHOLD_RELOAD() {
+    return ARGON2_WASM_MEMORY_THRESHOLD_RELOAD;
+  }
+
+  static set ARGON2_WASM_MEMORY_THRESHOLD_RELOAD(memoryThreshold) {
+    ARGON2_WASM_MEMORY_THRESHOLD_RELOAD = memoryThreshold;
+  }
+
+  static reloadWasmModule() {
+    if (!loadArgonWasmModule) return;
+
+    // it will be awaited if needed at the next `produceKey` invocation
+    argon2Promise = loadArgonWasmModule();
+    argon2Promise.catch(() => {});
+  }
+
   /**
   * @param {Object} [config] - Full configuration, defaults to openpgp.config
   */
@@ -125,10 +142,8 @@ class Argon2S2K {
       });
 
       // a lot of memory was used, reload to deallocate
-      if (decodedM > ARGON2_WASM_MEMORY_THRESHOLD_RELOAD) {
-        // it will be awaited if needed at the next `produceKey` invocation
-        argon2Promise = loadArgonWasmModule();
-        argon2Promise.catch(() => {});
+      if (decodedM > Argon2S2K.ARGON2_WASM_MEMORY_THRESHOLD_RELOAD) {
+        Argon2S2K.reloadWasmModule();
       }
       return hash;
     } catch (e) {

test/benchmarks/memory_usage.js

@@ -335,6 +335,20 @@ class MemoryBenchamrkSuite {
     await decryptedData.pipeTo(sink);
   });
 
+  suite.add('openpgp.encrypt/decryptSessionKeys (argon2)', async () => {
+    const config = { s2kType: openpgp.enums.s2k.argon2 };
+    const passwords = 'password';
+    const sessionKey = {
+      algorithm: 'aes128',
+      data: require('crypto').getRandomValues(new Uint8Array(16))
+    };
+    const encrypted = await openpgp.encryptSessionKey({ ...sessionKey, passwords, config, format: 'object' });
+    assert(encrypted.packets.length === 1);
+    const skesk = encrypted.packets[0];
+    assert(skesk.s2k.type === 'argon2');
+    await openpgp.decryptSessionKeys({ message: encrypted, passwords });
+  });
+
   const stats = await suite.run();
   // Print JSON stats to stdout
   console.log(JSON.stringify(stats, null, 4));