Eve-Relay/eventEncryptionDecryption.ts

import type { Database } from '@db/sqlite';
import * as nostrTools from '@nostr/tools';
import { nip44 } from '@nostr/tools';
import { MAX_CHUNK_SIZE, MIN_POW, POW_TO_MINE } from './consts.ts';
import {
  getCCNPrivateKey,
  getCCNPubkey,
  randomTimeUpTo2DaysInThePast,
} from './utils.ts';
import { sql } from './utils/queries.ts';

export class EventAlreadyExistsException extends Error {}
export class ChunkedEventReceived extends Error {}

export async function createEncryptedEvent(
  event: nostrTools.VerifiedEvent,
): Promise<nostrTools.VerifiedEvent | nostrTools.VerifiedEvent[]> {
  if (!event.id) throw new Error('Event must have an ID');
  if (!event.sig) throw new Error('Event must be signed');

  const ccnPubKey = await getCCNPubkey();
  const ccnPrivateKey = await getCCNPrivateKey();

  const eventJson = JSON.stringify(event);
  if (eventJson.length <= MAX_CHUNK_SIZE) {
    const randomPrivateKey = nostrTools.generateSecretKey();
    const randomPrivateKeyPubKey = nostrTools.getPublicKey(randomPrivateKey);
    const conversationKey = nip44.getConversationKey(
      randomPrivateKey,
      ccnPubKey,
    );
    const sealTemplate = {
      kind: 13,
      created_at: randomTimeUpTo2DaysInThePast(),
      content: nip44.encrypt(eventJson, conversationKey),
      tags: [],
    };
    const seal = nostrTools.finalizeEvent(sealTemplate, ccnPrivateKey);
    const giftWrapTemplate = {
      kind: 1059,
      created_at: randomTimeUpTo2DaysInThePast(),
      content: nip44.encrypt(JSON.stringify(seal), conversationKey),
      tags: [['p', ccnPubKey]],
      pubkey: randomPrivateKeyPubKey,
    };
    const minedGiftWrap = nostrTools.nip13.minePow(
      giftWrapTemplate,
      POW_TO_MINE,
    );
    const giftWrap = nostrTools.finalizeEvent(minedGiftWrap, randomPrivateKey);
    return giftWrap;
  }

  const chunks: string[] = [];
  for (let i = 0; i < eventJson.length; i += MAX_CHUNK_SIZE)
    chunks.push(eventJson.slice(i, i + MAX_CHUNK_SIZE));

  const messageId = crypto.randomUUID();
  const totalChunks = chunks.length;

  const encryptedChunks = [];
  for (let i = 0; i < chunks.length; i++) {
    const chunk = chunks[i];
    const randomPrivateKey = nostrTools.generateSecretKey();
    const randomPrivateKeyPubKey = nostrTools.getPublicKey(randomPrivateKey);
    const conversationKey = nip44.getConversationKey(
      randomPrivateKey,
      ccnPubKey,
    );

    const sealTemplate = {
      kind: 13,
      created_at: randomTimeUpTo2DaysInThePast(),
      content: nip44.encrypt(chunk, conversationKey),
      tags: [['chunk', String(i), String(totalChunks), messageId]],
    };

    const seal = nostrTools.finalizeEvent(sealTemplate, ccnPrivateKey);
    const giftWrapTemplate = {
      kind: 1059,
      created_at: randomTimeUpTo2DaysInThePast(),
      content: nip44.encrypt(JSON.stringify(seal), conversationKey),
      tags: [['p', ccnPubKey]],
      pubkey: randomPrivateKeyPubKey,
    };

    const minedGiftWrap = nostrTools.nip13.minePow(
      giftWrapTemplate,
      POW_TO_MINE,
    );
    encryptedChunks.push(
      nostrTools.finalizeEvent(minedGiftWrap, randomPrivateKey),
    );
  }

  return encryptedChunks;
}
export async function decryptEvent(
  db: Database,
  event: nostrTools.Event,
): Promise<nostrTools.VerifiedEvent> {
  const ccnPrivkey = await getCCNPrivateKey();

  if (event.kind !== 1059) {
    throw new Error('Cannot decrypt event -- not a gift wrap');
  }

  const pow = nostrTools.nip13.getPow(event.id);

  if (pow < MIN_POW) {
    throw new Error('Cannot decrypt event -- PoW too low');
  }

  const conversationKey = nip44.getConversationKey(ccnPrivkey, event.pubkey);
  const seal = JSON.parse(nip44.decrypt(event.content, conversationKey));
  if (!seal) throw new Error('Cannot decrypt event -- no seal');
  if (seal.kind !== 13) {
    throw new Error('Cannot decrypt event subevent -- not a seal');
  }

  const chunkTag = seal.tags.find((tag: string[]) => tag[0] === 'chunk');
  if (!chunkTag) {
    const content = JSON.parse(nip44.decrypt(seal.content, conversationKey));
    return content as nostrTools.VerifiedEvent;
  }

  const [_, chunkIndex, totalChunks, messageId] = chunkTag;
  const chunk = nip44.decrypt(seal.content, conversationKey);

  try {
    sql`
      INSERT INTO event_chunks (
        message_id,
        chunk_index,
        total_chunks,
        chunk_data,
        conversation_key,
        created_at
      ) VALUES (
        ${messageId},
        ${Number(chunkIndex)},
        ${Number(totalChunks)},
        ${chunk},
        ${conversationKey},
        ${Math.floor(Date.now() / 1000)}
      )
    `(db);

    const chunks = sql`
      SELECT chunk_data 
      FROM event_chunks 
      WHERE message_id = ${messageId}
      ORDER BY chunk_index ASC
    `(db);

    if (chunks.length === Number(totalChunks)) {
      const completeEventJson = chunks.map((c) => c.chunk_data).join('');

      sql`DELETE FROM event_chunks WHERE message_id = ${messageId}`(db);

      return JSON.parse(completeEventJson) as nostrTools.VerifiedEvent;
    }

    throw new ChunkedEventReceived(
      `Chunked event received (${chunks.length}/${totalChunks}) - messageId: ${messageId}`,
    );
  } catch (e) {
    if (e instanceof Error && e.message.includes('UNIQUE constraint failed'))
      throw new Error(
        `Duplicate chunk received (${Number(chunkIndex) + 1}/${totalChunks}) - messageId: ${messageId}`,
      );
    throw e;
  }
}