breez style passkey derivationstaging

2 files changed, 116 insertions, 11 deletions

diff --git a/src/lib/keyWrapping.ts b/src/lib/keyWrapping.ts
index 31cb1e5c..cd68947f 100644
--- a/src/lib/keyWrapping.ts
+++ b/src/lib/keyWrapping.ts
@@ -28,9 +28,20 @@ export async function resolveCanonicalKey(
   oldPrfKey: ArrayBuffer,
 ): Promise<{ canonicalKey: ArrayBuffer; encryptedKeys: Record<string, string> }> {
   if (encryptedKeys && encryptedKeys[methodId]) {
-    const canonicalKey = await unwrapCanonicalKey(wrappingKey, encryptedKeys[methodId]);
-    rememberPrfKey(canonicalKey, defaultRememberForMs);
-    return { canonicalKey, encryptedKeys };
+    try {
+      // Try new wrapping key first (e.g. PRF-derived)
+      const canonicalKey = await unwrapCanonicalKey(wrappingKey, encryptedKeys[methodId]);
+      rememberPrfKey(canonicalKey, defaultRememberForMs);
+      return { canonicalKey, encryptedKeys };
+    } catch {
+      // Fallback: try old key (e.g. SHA-256(credentialId)) and re-wrap with new key
+      const canonicalKey = await unwrapCanonicalKey(oldPrfKey, encryptedKeys[methodId]);
+      const wrapped = await wrapCanonicalKey(wrappingKey, canonicalKey);
+      const updated = { ...encryptedKeys, [methodId]: wrapped };
+      await saveEncryptedKeys(updated);
+      rememberPrfKey(canonicalKey, defaultRememberForMs);
+      return { canonicalKey, encryptedKeys: updated };
+    }
   }
 
   // Migration: old PRF key becomes canonical key
diff --git a/src/lib/passkey.ts b/src/lib/passkey.ts
index 3d7b7272..8e73144b 100644
--- a/src/lib/passkey.ts
+++ b/src/lib/passkey.ts
@@ -1,35 +1,129 @@
-import { startRegistration, startAuthentication } from "@simplewebauthn/browser";
+import { startRegistration } from "@simplewebauthn/browser";
 import { post } from "$lib/utils";
 
-async function deriveKey(credentialId: string): Promise<ArrayBuffer> {
+const PRF_SALT = new TextEncoder().encode("coinos-wallet-key");
+
+function bufferToBase64url(buffer: ArrayBuffer): string {
+  const bytes = new Uint8Array(buffer);
+  let binary = "";
+  for (const b of bytes) binary += String.fromCharCode(b);
+  return btoa(binary).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
+}
+
+function base64urlToBuffer(base64url: string): ArrayBuffer {
+  const padded =
+    base64url.replace(/-/g, "+").replace(/_/g, "/") +
+    "==".slice(0, (4 - (base64url.length % 4)) % 4);
+  const binary = atob(padded);
+  const bytes = new Uint8Array(binary.length);
+  for (let i = 0; i < binary.length; i++) bytes[i] = binary.charCodeAt(i);
+  return bytes.buffer as ArrayBuffer;
+}
+
+async function deriveKeyLegacy(credentialId: string): Promise<ArrayBuffer> {
   const data = new TextEncoder().encode("coinos-wallet-key:" + credentialId);
   return crypto.subtle.digest("SHA-256", data);
 }
 
+async function evaluatePrf(credentialId: string): Promise<ArrayBuffer | null> {
+  try {
+    const assertion = (await navigator.credentials.get({
+      publicKey: {
+        challenge: crypto.getRandomValues(new Uint8Array(32)),
+        allowCredentials: [
+          { id: base64urlToBuffer(credentialId), type: "public-key" as const },
+        ],
+        extensions: { prf: { eval: { first: PRF_SALT } } } as any,
+        userVerification: "required",
+      },
+    })) as PublicKeyCredential;
+
+    const results = (assertion.getClientExtensionResults() as any).prf?.results;
+    return results?.first || null;
+  } catch {
+    return null;
+  }
+}
+
 function authHeader(token: string) {
   return { authorization: `Bearer ${token}` };
 }
 
 export async function registerPasskey(
   token?: string,
-): Promise<{ prfKey: ArrayBuffer; credentialId: string }> {
+): Promise<{ prfKey: ArrayBuffer; credentialId: string; prfSupported: boolean }> {
   const headers = token ? authHeader(token) : undefined;
   const origin = window.location.origin;
   const options = await post("/passkey/register/options", { origin }, headers);
   const registration = await startRegistration({ optionsJSON: options });
   await post("/passkey/register/verify", { ...registration, origin }, headers);
-  const prfKey = await deriveKey(registration.id);
-  return { prfKey, credentialId: registration.id };
+
+  // Try PRF evaluation with an immediate get() after registration
+  const prfResult = await evaluatePrf(registration.id);
+  if (prfResult) {
+    return { prfKey: prfResult, credentialId: registration.id, prfSupported: true };
+  }
+
+  // Fallback to legacy SHA-256(credentialId)
+  const legacyKey = await deriveKeyLegacy(registration.id);
+  return { prfKey: legacyKey, credentialId: registration.id, prfSupported: false };
 }
 
 export async function loginWithPasskey(): Promise<{
   credential: any;
   challengeId: string;
   prfKey: ArrayBuffer;
+  legacyKey: ArrayBuffer;
 }> {
   const origin = window.location.origin;
   const { challengeId, ...options } = await post("/passkey/login/options", { origin });
-  const authentication = await startAuthentication({ optionsJSON: options });
-  const prfKey = await deriveKey(authentication.id);
-  return { credential: authentication, challengeId, prfKey };
+
+  // Convert options from JSON to WebAuthn API format
+  const publicKeyOptions: PublicKeyCredentialRequestOptions = {
+    challenge: base64urlToBuffer(options.challenge),
+    rpId: options.rpId,
+    timeout: options.timeout,
+    userVerification: (options.userVerification as UserVerificationRequirement) || "required",
+    allowCredentials: options.allowCredentials?.map((c: any) => ({
+      id: base64urlToBuffer(c.id),
+      type: c.type as PublicKeyCredentialType,
+      transports: c.transports,
+    })),
+    extensions: {
+      prf: { eval: { first: PRF_SALT } },
+    } as any,
+  };
+
+  const assertion = (await navigator.credentials.get({
+    publicKey: publicKeyOptions,
+  })) as PublicKeyCredential;
+
+  const response = assertion.response as AuthenticatorAssertionResponse;
+
+  // Serialize response in the format the server expects (same as simplewebauthn)
+  const credential = {
+    id: assertion.id,
+    rawId: bufferToBase64url(assertion.rawId),
+    response: {
+      authenticatorData: bufferToBase64url(response.authenticatorData),
+      clientDataJSON: bufferToBase64url(response.clientDataJSON),
+      signature: bufferToBase64url(response.signature),
+      userHandle: response.userHandle ? bufferToBase64url(response.userHandle) : null,
+    },
+    type: assertion.type,
+    clientExtensionResults: {},
+    authenticatorAttachment: (assertion as any).authenticatorAttachment || null,
+  };
+
+  // Extract PRF result
+  const prfResults = (assertion.getClientExtensionResults() as any).prf?.results;
+  const prfOutput: ArrayBuffer | null = prfResults?.first || null;
+
+  // Compute legacy key for migration
+  const legacyKey = await deriveKeyLegacy(assertion.id);
+
+  // Use PRF output if available, otherwise fall back to legacy
+  const prfKey = prfOutput || legacyKey;
+
+  return { credential, challengeId, prfKey, legacyKey };
 }