feat: integrate webcrypto-liner for legacy algorithm support in S/MIME handling

2026-03-18 14:29:29 +01:00
parent 84abfe79dd
commit 8a2ef5a6c5
6 changed files with 281 additions and 12 deletions
@@ -0,0 +1,76 @@
+/**
+ * Crypto engine backed by webcrypto-liner for legacy algorithm support.
+ *
+ * webcrypto-liner extends the native Web Crypto API with algorithms
+ * like DES-EDE3-CBC (3DES) that are commonly found in S/MIME messages
+ * and PKCS#12 files produced by legacy clients (Outlook, Thunderbird, etc.).
+ *
+ * Native Web Crypto calls are passed through to the real implementation;
+ * liner only intercepts algorithms that the browser doesn't natively support.
+ */
+
+import * as pkijs from 'pkijs';
+
+// webcrypto-liner exports a Crypto constructor at runtime that extends native
+// Web Crypto with legacy algorithms (3DES, etc.). Its type declarations only
+// expose the type alias, so we import the module dynamically and cast.
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+const liner = require('webcrypto-liner') as {
+  Crypto: { new (): Crypto };
+  setCrypto: (subtle: SubtleCrypto) => void;
+  nativeCrypto: Crypto | Record<string, never>;
+};
+
+let linerEngine: pkijs.CryptoEngine | null = null;
+let linerCryptoInstance: Crypto | null = null;
+
+function ensureLiner() {
+  if (!linerCryptoInstance) {
+    // In Node.js, webcrypto-liner can't auto-detect the native crypto
+    // (it looks for self.crypto which doesn't exist). Feed it manually
+    // so that native algorithms (RSA, AES, etc.) stay hardware-accelerated
+    // and only truly missing algorithms (3DES) use the software fallback.
+    if (
+      typeof liner.nativeCrypto?.getRandomValues !== 'function' &&
+      typeof globalThis.crypto?.subtle !== 'undefined'
+    ) {
+      liner.setCrypto(globalThis.crypto.subtle);
+    }
+    linerCryptoInstance = new liner.Crypto();
+  }
+  if (!linerEngine) {
+    linerEngine = new pkijs.CryptoEngine({
+      crypto: linerCryptoInstance,
+      subtle: linerCryptoInstance.subtle,
+      name: 'webcrypto-liner',
+    });
+  }
+}
+
+/** Get a PKI.js CryptoEngine with 3DES (and other legacy algorithm) support. */
+export function getLinerCryptoEngine(): pkijs.CryptoEngine {
+  ensureLiner();
+  return linerEngine!;
+}
+
+/**
+ * Run an async operation with the global PKI.js engine set to webcrypto-liner,
+ * then restore the previous engine afterwards.
+ *
+ * Required for operations that use the global engine internally
+ * (e.g. PFX.parseInternalValues for PKCS#12 import).
+ */
+export async function withLinerEngine<T>(fn: () => Promise<T>): Promise<T> {
+  ensureLiner();
+
+  // Save the current global engine so we can restore it
+  const prev = pkijs.getEngine();
+
+  pkijs.setEngine('webcrypto-liner', linerCryptoInstance!, linerEngine!);
+  try {
+    return await fn();
+  } finally {
+    // Restore the previous engine
+    pkijs.setEngine(prev.name, prev.crypto as unknown as pkijs.CryptoEngine);
+  }
+}