feat(client): add keypair generation

plugin/core/runtime.ts

@@ -9,11 +9,12 @@ import {
 } from "../../../Yonexus.Protocol/src/index.js";
 import type { YonexusClientConfig } from "./config.js";
 import {
-  createInitialClientState,
+  ensureClientKeyPair,
   hasClientKeyPair,
   hasClientSecret,
-  type YonexusClientState,
+  createInitialClientState,
-  type YonexusClientStateStore
+  YonexusClientState,
+  YonexusClientStateStore
 } from "./state.js";
 import type { ClientConnectionState, ClientTransport } from "./transport.js";
 
@@ -66,7 +67,12 @@ export class YonexusClientRuntime {
     }
 
     this.phase = "starting";
-    this.clientState = await this.options.stateStore.load(this.options.config.identifier);
+    
+    // Load existing state and ensure key pair exists
+    let state = await this.options.stateStore.load(this.options.config.identifier);
+    const keyResult = await ensureClientKeyPair(state, this.options.stateStore);
+    this.clientState = keyResult.state;
+    
     await this.options.transport.connect();
   }
 

plugin/core/state.ts

@@ -1,5 +1,6 @@
 import { mkdir, readFile, rename, writeFile } from "node:fs/promises";
 import { dirname } from "node:path";
+import { generateKeyPair, type KeyPair } from "../crypto/keypair.js";
 
 export const CLIENT_STATE_VERSION = 1;
 
@@ -132,6 +133,31 @@ export function hasClientKeyPair(state: YonexusClientState): boolean {
   );
 }
 
+/**
+ * Ensure the client state has a valid key pair.
+ * If no key pair exists, generates a new Ed25519 key pair.
+ * Returns the (possibly updated) state and whether a new key was generated.
+ */
+export async function ensureClientKeyPair(
+  state: YonexusClientState,
+  stateStore: YonexusClientStateStore
+): Promise<{ state: YonexusClientState; generated: boolean }> {
+  if (hasClientKeyPair(state)) {
+    return { state, generated: false };
+  }
+
+  const keyPair = await generateKeyPair();
+  const updatedState: YonexusClientState = {
+    ...state,
+    privateKey: keyPair.privateKey,
+    publicKey: keyPair.publicKey,
+    updatedAt: Math.floor(Date.now() / 1000)
+  };
+
+  await stateStore.save(updatedState);
+  return { state: updatedState, generated: true };
+}
+
 function assertClientStateShape(
   value: unknown,
   filePath: string

plugin/crypto/keypair.ts

@@ -0,0 +1,119 @@
+import { randomBytes, sign as signMessageRaw, verify as verifySignatureRaw } from "node:crypto";
+
+/**
+ * Key pair for Yonexus client authentication
+ * Uses Ed25519 for digital signatures
+ */
+export interface KeyPair {
+  /** Base64-encoded Ed25519 private key */
+  readonly privateKey: string;
+  /** Base64-encoded Ed25519 public key */
+  readonly publicKey: string;
+  /** Algorithm identifier for compatibility */
+  readonly algorithm: "Ed25519";
+}
+
+/**
+ * Generate a new Ed25519 key pair for client authentication.
+ * 
+ * In v1, we use Node.js crypto.generateKeyPairSync for Ed25519.
+ * The keys are encoded as base64 for JSON serialization.
+ */
+export async function generateKeyPair(): Promise<KeyPair> {
+  const { generateKeyPair } = await import("node:crypto");
+
+  const { publicKey, privateKey } = await new Promise<{
+    publicKey: string;
+    privateKey: string;
+  }>((resolve, reject) => {
+    generateKeyPair(
+      "ed25519",
+      {
+        publicKeyEncoding: { type: "spki", format: "pem" },
+        privateKeyEncoding: { type: "pkcs8", format: "pem" }
+      },
+      (err, pubKey, privKey) => {
+        if (err) {
+          reject(err);
+          return;
+        }
+        resolve({ publicKey: pubKey, privateKey: privKey });
+      }
+    );
+  });
+
+  return {
+    privateKey,
+    publicKey,
+    algorithm: "Ed25519"
+  };
+}
+
+/**
+ * Sign a message using the client's private key.
+ * 
+ * @param privateKeyPem - PEM-encoded private key
+ * @param message - Message to sign (Buffer or string)
+ * @returns Base64-encoded signature
+ */
+export async function signMessage(
+  privateKeyPem: string,
+  message: Buffer | string
+): Promise<string> {
+  const signature = signMessageRaw(null, typeof message === "string" ? Buffer.from(message) : message, privateKeyPem);
+  return signature.toString("base64");
+}
+
+/**
+ * Verify a signature using the client's public key.
+ * 
+ * @param publicKeyPem - PEM-encoded public key
+ * @param message - Original message (Buffer or string)
+ * @param signature - Base64-encoded signature
+ * @returns Whether the signature is valid
+ */
+export async function verifySignature(
+  publicKeyPem: string,
+  message: Buffer | string,
+  signature: string
+): Promise<boolean> {
+  try {
+    const sigBuffer = Buffer.from(signature, "base64");
+    return verifySignatureRaw(null, typeof message === "string" ? Buffer.from(message) : message, publicKeyPem, sigBuffer);
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Generate a cryptographically secure random pairing code.
+ * Format: XXXX-XXXX-XXXX (12 alphanumeric characters in groups of 4)
+ */
+export function generatePairingCode(): string {
+  const bytes = randomBytes(8);
+  const chars = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789"; // Excludes confusing chars (0, O, 1, I)
+  
+  let code = "";
+  for (let i = 0; i < 12; i++) {
+    code += chars[bytes[i % bytes.length] % chars.length];
+  }
+
+  // Format as XXXX-XXXX-XXXX
+  return `${code.slice(0, 4)}-${code.slice(4, 8)}-${code.slice(8, 12)}`;
+}
+
+/**
+ * Generate a shared secret for client authentication.
+ * This is issued by the server after successful pairing.
+ */
+export function generateSecret(): string {
+  return randomBytes(32).toString("base64url");
+}
+
+/**
+ * Generate a 24-character nonce for authentication.
+ */
+export function generateNonce(): string {
+  const bytes = randomBytes(18);
+  return bytes.toString("base64url").slice(0, 24);
+}