General Upgrade, NEW: WebServers, Better Docs

src/sdk/session.ts

@@ -1,35 +1,5 @@
 import * as bindings from "mtp/raw";
-
-function utf8Encode(text: string): Uint8Array {
-  if (typeof TextEncoder !== "undefined") {
-    return new TextEncoder().encode(text);
-  }
-  if (typeof Buffer !== "undefined") {
-    return new Uint8Array(Buffer.from(text, "utf-8"));
-  }
-  const bytes = new Uint8Array(text.length * 4);
-  let len = 0;
-  for (let i = 0; i < text.length; i += 1) {
-    const code = text.codePointAt(i) as number;
-    if (code < 0x80) {
-      bytes[len++] = code;
-    } else if (code < 0x800) {
-      bytes[len++] = 0xc0 | (code >> 6);
-      bytes[len++] = 0x80 | (code & 0x3f);
-    } else if (code < 0x10000) {
-      bytes[len++] = 0xe0 | (code >> 12);
-      bytes[len++] = 0x80 | ((code >> 6) & 0x3f);
-      bytes[len++] = 0x80 | (code & 0x3f);
-    } else {
-      bytes[len++] = 0xf0 | (code >> 18);
-      bytes[len++] = 0x80 | ((code >> 12) & 0x3f);
-      bytes[len++] = 0x80 | ((code >> 6) & 0x3f);
-      bytes[len++] = 0x80 | (code & 0x3f);
-      i += 1;
-    }
-  }
-  return bytes.subarray(0, len);
-}
+import { concatBytes, utf8Encode, writeU64BE } from "./utils.js";
 
 export const HKDF_SALT_ROOT = "mtp-e2ee-v1-root";
 const HKDF_INITIATOR_SEND = "mtp-e2ee-v1-initiator-send";
@@ -55,10 +25,17 @@ export interface MTPSessionState {
   recvChainKey: Uint8Array;
   sendCount: number;
   recvCount: number;
+  /** Derived receive keys retained for bounded out-of-order delivery. */
+  skippedMessageKeys?: SkippedMessageKey[];
   createdAt: number;
   updatedAt: number;
 }
 
+export interface SkippedMessageKey {
+  messageNumber: number;
+  key: Uint8Array;
+}
+
 export interface MTPSessionStorage {
   getSession(conversationId: string): Promise<MTPSessionState | null>;
   setSession(state: MTPSessionState): Promise<void>;
@@ -68,15 +45,40 @@ export interface MTPSessionStorage {
 export class InMemorySessionStorage implements MTPSessionStorage {
   private store = new Map<string, MTPSessionState>();
 
+  private cloneSession(state: MTPSessionState): MTPSessionState {
+    return {
+      ...state,
+      peerPublicKey: state.peerPublicKey.slice(),
+      sendChainKey: state.sendChainKey.slice(),
+      recvChainKey: state.recvChainKey.slice(),
+      skippedMessageKeys: (state.skippedMessageKeys ?? []).map((skipped) => ({
+        messageNumber: skipped.messageNumber,
+        key: skipped.key.slice(),
+      })),
+    };
+  }
+
+  private zeroizeSession(state: MTPSessionState): void {
+    state.sendChainKey.fill(0);
+    state.recvChainKey.fill(0);
+    for (const skipped of state.skippedMessageKeys ?? []) skipped.key.fill(0);
+  }
+
   async getSession(conversationId: string): Promise<MTPSessionState | null> {
-    return this.store.get(conversationId) ?? null;
+    const state = this.store.get(conversationId);
+    return state ? this.cloneSession(state) : null;
   }
 
   async setSession(state: MTPSessionState): Promise<void> {
-    this.store.set(state.conversationId, { ...state });
+    const replacement = this.cloneSession(state);
+    const previous = this.store.get(state.conversationId);
+    if (previous) this.zeroizeSession(previous);
+    this.store.set(state.conversationId, replacement);
   }
 
   async deleteSession(conversationId: string): Promise<void> {
+    const previous = this.store.get(conversationId);
+    if (previous) this.zeroizeSession(previous);
     this.store.delete(conversationId);
   }
 }
@@ -90,27 +92,6 @@ function writeU32BE(value: number): Uint8Array {
   ]);
 }
 
-function writeU64BE(value: bigint): Uint8Array {
-  if (value < 0n || value > 0xffff_ffff_ffff_ffffn)
-    throw new Error("u64 out of range");
-  const buf = new Uint8Array(8);
-  for (let i = 7; i >= 0; i -= 1) {
-    buf[i] = Number(value & 0xffn);
-    value >>= 8n;
-  }
-  return buf;
-}
-
-function concatBytes(parts: Uint8Array[]): Uint8Array {
-  const out = new Uint8Array(parts.reduce((sum, part) => sum + part.length, 0));
-  let offset = 0;
-  for (const part of parts) {
-    out.set(part, offset);
-    offset += part.length;
-  }
-  return out;
-}
-
 function transcriptField(label: string, value: Uint8Array): Uint8Array {
   const labelBytes = utf8Encode(label);
   return concatBytes([
@@ -240,6 +221,7 @@ export class MTPSessionManager {
       recvChainKey: args.role === "initiator" ? initiatorRecv : initiatorSend,
       sendCount: 0,
       recvCount: 0,
+      skippedMessageKeys: [],
       createdAt: now,
       updatedAt: now,
     };