signal-desktop/app/attachment_channel.ts

// Copyright 2018 Signal Messenger, LLC
// SPDX-License-Identifier: AGPL-3.0-only

import { ipcMain, protocol } from 'electron';
import { createReadStream } from 'node:fs';
import { join, normalize } from 'node:path';
import { PassThrough, type Writable } from 'node:stream';
import { pipeline } from 'node:stream/promises';
import { randomBytes } from 'node:crypto';
import { once } from 'node:events';
import z from 'zod';
import * as rimraf from 'rimraf';
import LRU from 'lru-cache';
import {
  inferChunkSize,
  DigestingWritable,
} from '@signalapp/libsignal-client/dist/incremental_mac';
import { RangeFinder, DefaultStorage } from '@indutny/range-finder';
import {
  getAllAttachments,
  getAllDownloads,
  getAvatarsPath,
  getPath,
  getStickersPath,
  getTempPath,
  getDraftPath,
  getDownloadsPath,
  deleteAll as deleteAllAttachments,
  deleteAllBadges,
  deleteAllDownloads,
  deleteStaleDownloads,
  getAllStickers,
  deleteAllStickers,
  getAllDraftAttachments,
  deleteAllDraftAttachments,
} from './attachments';
import type { MainSQL } from '../ts/sql/main';
import type { MessageAttachmentsCursorType } from '../ts/sql/Interface';
import * as Errors from '../ts/types/errors';
import {
  APPLICATION_OCTET_STREAM,
  MIMETypeToString,
  stringToMIMEType,
} from '../ts/types/MIME';
import { sleep } from '../ts/util/sleep';
import { isPathInside } from '../ts/util/isPathInside';
import { missingCaseError } from '../ts/util/missingCaseError';
import { safeParseInteger } from '../ts/util/numbers';
import { SECOND } from '../ts/util/durations';
import { drop } from '../ts/util/drop';
import { strictAssert } from '../ts/util/assert';
import { ValidatingPassThrough } from '../ts/util/ValidatingPassThrough';
import { toWebStream } from '../ts/util/toWebStream';
import {
  isImageTypeSupported,
  isVideoTypeSupported,
} from '../ts/util/GoogleChrome';
import { decryptAttachmentV2ToSink } from '../ts/AttachmentCrypto';

let initialized = false;

const ERASE_ATTACHMENTS_KEY = 'erase-attachments';
const ERASE_STICKERS_KEY = 'erase-stickers';
const ERASE_TEMP_KEY = 'erase-temp';
const ERASE_DRAFTS_KEY = 'erase-drafts';
const ERASE_DOWNLOADS_KEY = 'erase-downloads';
const CLEANUP_DOWNLOADS_KEY = 'cleanup-downloads';
const CLEANUP_ORPHANED_ATTACHMENTS_KEY = 'cleanup-orphaned-attachments';

const INTERACTIVITY_DELAY = 50;

type RangeFinderContextType = Readonly<
  (
    | {
        type: 'ciphertext';
        keysBase64: string;
        size: number;
      }
    | {
        type: 'plaintext';
      }
  ) & {
    path: string;
  }
>;

type DigestLRUEntryType = Readonly<{
  key: Buffer;
  digest: Buffer;
}>;

const digestLRU = new LRU<string, DigestLRUEntryType>({
  // The size of each entry is roughgly 8kb per digest + 32 bytes per key. We
  // mostly need this cache for range requests, so keep it low.
  max: 100,
});

async function safeDecryptToSink(
  ctx: RangeFinderContextType,
  sink: Writable
): Promise<void> {
  strictAssert(ctx.type === 'ciphertext', 'Cannot decrypt plaintext');

  const options = {
    ciphertextPath: ctx.path,
    idForLogging: 'attachment_channel',
    keysBase64: ctx.keysBase64,
    type: 'local' as const,
    size: ctx.size,
  };

  try {
    const chunkSize = inferChunkSize(ctx.size);
    let entry = digestLRU.get(ctx.path);
    if (!entry) {
      const key = randomBytes(32);
      const writable = new DigestingWritable(key, chunkSize);

      const controller = new AbortController();

      await Promise.race([
        // Just use a non-existing event name to wait for an 'error'. We want
        // to handle errors on `sink` while generating digest in case whole
        // request get cancelled early.
        once(sink, 'non-error-event', { signal: controller.signal }),
        decryptAttachmentV2ToSink(options, writable),
      ]);

      // Stop handling errors on sink
      controller.abort();

      entry = {
        key,
        digest: writable.getFinalDigest(),
      };
      digestLRU.set(ctx.path, entry);
    }

    const validator = new ValidatingPassThrough(
      entry.key,
      chunkSize,
      entry.digest
    );
    await Promise.all([
      decryptAttachmentV2ToSink(options, validator),
      pipeline(validator, sink),
    ]);
  } catch (error) {
    // These errors happen when canceling fetch from `attachment://` urls,
    // ignore them to avoid noise in the logs.
    if (
      error.name === 'AbortError' ||
      error.code === 'ERR_STREAM_PREMATURE_CLOSE'
    ) {
      return;
    }

    console.error(
      'handleAttachmentRequest: decryption error',
      Errors.toLogFormat(error)
    );
  }
}

const storage = new DefaultStorage<RangeFinderContextType>(
  ctx => {
    if (ctx.type === 'plaintext') {
      return createReadStream(ctx.path);
    }

    if (ctx.type === 'ciphertext') {
      const plaintext = new PassThrough();
      drop(safeDecryptToSink(ctx, plaintext));
      return plaintext;
    }

    throw missingCaseError(ctx);
  },
  {
    maxSize: 10,
    ttl: SECOND,
    cacheKey: ctx => {
      if (ctx.type === 'ciphertext') {
        return `${ctx.type}:${ctx.path}:${ctx.size}:${ctx.keysBase64}`;
      }
      if (ctx.type === 'plaintext') {
        return `${ctx.type}:${ctx.path}`;
      }
      throw missingCaseError(ctx);
    },
  }
);
const rangeFinder = new RangeFinder<RangeFinderContextType>(storage, {
  noActiveReuse: true,
});

const dispositionSchema = z.enum([
  'attachment',
  'temporary',
  'draft',
  'sticker',
  'avatarData',
]);

type DeleteOrphanedAttachmentsOptionsType = Readonly<{
  orphanedAttachments: Set<string>;
  orphanedDownloads: Set<string>;
  sql: MainSQL;
  userDataPath: string;
}>;

type CleanupOrphanedAttachmentsOptionsType = Readonly<{
  sql: MainSQL;
  userDataPath: string;
}>;

async function cleanupOrphanedAttachments({
  sql,
  userDataPath,
}: CleanupOrphanedAttachmentsOptionsType): Promise<void> {
  await deleteAllBadges({
    userDataPath,
    pathsToKeep: await sql.sqlRead('getAllBadgeImageFileLocalPaths'),
  });

  const allStickers = await getAllStickers(userDataPath);
  const orphanedStickers = await sql.sqlWrite(
    'removeKnownStickers',
    allStickers
  );
  await deleteAllStickers({
    userDataPath,
    stickers: orphanedStickers,
  });

  const allDraftAttachments = await getAllDraftAttachments(userDataPath);
  const orphanedDraftAttachments = await sql.sqlWrite(
    'removeKnownDraftAttachments',
    allDraftAttachments
  );
  await deleteAllDraftAttachments({
    userDataPath,
    attachments: orphanedDraftAttachments,
  });

  // Delete orphaned attachments from conversations and messages.

  const orphanedAttachments = new Set(await getAllAttachments(userDataPath));
  console.log(
    'cleanupOrphanedAttachments: found ' +
      `${orphanedAttachments.size} attachments on disk`
  );

  const orphanedDownloads = new Set(await getAllDownloads(userDataPath));
  console.log(
    'cleanupOrphanedAttachments: found ' +
      `${orphanedDownloads.size} downloads on disk`
  );

  {
    const attachments: Array<string> = await sql.sqlRead(
      'getKnownConversationAttachments'
    );

    let missing = 0;
    for (const known of attachments) {
      if (!orphanedAttachments.delete(known)) {
        missing += 1;
      }
    }

    console.log(
      `cleanupOrphanedAttachments: found ${attachments.length} conversation ` +
        `attachments (${missing} missing), ${orphanedAttachments.size} remain`
    );
  }

  {
    const downloads: Array<string> = await sql.sqlRead('getKnownDownloads');

    let missing = 0;
    for (const known of downloads) {
      if (!orphanedDownloads.delete(known)) {
        missing += 1;
      }
    }

    console.log(
      `cleanupOrphanedAttachments: found ${downloads.length} downloads ` +
        `(${missing} missing), ${orphanedDownloads.size} remain`
    );
  }

  // This call is intentionally not awaited. We block the app while running
  // all fetches above to ensure that there are no in-flight attachments that
  // are saved to disk, but not put into any message or conversation model yet.
  deleteOrphanedAttachments({
    orphanedAttachments,
    orphanedDownloads,
    sql,
    userDataPath,
  });
}

function deleteOrphanedAttachments({
  orphanedAttachments,
  orphanedDownloads,
  sql,
  userDataPath,
}: DeleteOrphanedAttachmentsOptionsType): void {
  // This function *can* throw.
  async function runWithPossibleException(): Promise<void> {
    let cursor: MessageAttachmentsCursorType | undefined;
    let totalFound = 0;
    let totalMissing = 0;
    let totalDownloadsFound = 0;
    let totalDownloadsMissing = 0;
    try {
      do {
        let attachments: ReadonlyArray<string>;
        let downloads: ReadonlyArray<string>;

        // eslint-disable-next-line no-await-in-loop
        ({ attachments, downloads, cursor } = await sql.sqlRead(
          'getKnownMessageAttachments',
          cursor
        ));

        totalFound += attachments.length;
        totalDownloadsFound += downloads.length;

        for (const known of attachments) {
          if (!orphanedAttachments.delete(known)) {
            totalMissing += 1;
          }
        }

        for (const known of downloads) {
          if (!orphanedDownloads.delete(known)) {
            totalDownloadsMissing += 1;
          }
        }

        if (cursor === undefined) {
          break;
        }

        // Let other SQL calls come through. There are hundreds of thousands of
        // messages in the database and it might take time to go through them all.
        // eslint-disable-next-line no-await-in-loop
        await sleep(INTERACTIVITY_DELAY);
      } while (cursor !== undefined && !cursor.done);
    } finally {
      if (cursor !== undefined) {
        await sql.sqlRead('finishGetKnownMessageAttachments', cursor);
      }
    }

    console.log(
      `cleanupOrphanedAttachments: found ${totalFound} message ` +
        `attachments, (${totalMissing} missing) ` +
        `${orphanedAttachments.size} remain`
    );

    await deleteAllAttachments({
      userDataPath,
      attachments: Array.from(orphanedAttachments),
    });

    console.log(
      `cleanupOrphanedAttachments: found ${totalDownloadsFound} downloads ` +
        `(${totalDownloadsMissing} missing) ` +
        `${orphanedDownloads.size} remain`
    );
    await deleteAllDownloads({
      userDataPath,
      downloads: Array.from(orphanedDownloads),
    });
  }

  async function runSafe() {
    const start = Date.now();
    try {
      await runWithPossibleException();
    } catch (error) {
      console.error(
        'deleteOrphanedAttachments: error',
        Errors.toLogFormat(error)
      );
    } finally {
      const duration = Date.now() - start;
      console.log(`deleteOrphanedAttachments: took ${duration}ms`);
    }
  }

  // Intentionally not awaiting
  void runSafe();
}

let attachmentsDir: string | undefined;
let stickersDir: string | undefined;
let tempDir: string | undefined;
let draftDir: string | undefined;
let downloadsDir: string | undefined;
let avatarDataDir: string | undefined;

export function initialize({
  configDir,
  sql,
}: {
  configDir: string;
  sql: MainSQL;
}): void {
  if (initialized) {
    throw new Error('initialize: Already initialized!');
  }
  initialized = true;

  attachmentsDir = getPath(configDir);
  stickersDir = getStickersPath(configDir);
  tempDir = getTempPath(configDir);
  draftDir = getDraftPath(configDir);
  downloadsDir = getDownloadsPath(configDir);
  avatarDataDir = getAvatarsPath(configDir);

  ipcMain.handle(ERASE_TEMP_KEY, () => {
    strictAssert(tempDir != null, 'not initialized');
    rimraf.sync(tempDir);
  });
  ipcMain.handle(ERASE_ATTACHMENTS_KEY, () => {
    strictAssert(attachmentsDir != null, 'not initialized');
    rimraf.sync(attachmentsDir);
  });
  ipcMain.handle(ERASE_STICKERS_KEY, () => {
    strictAssert(stickersDir != null, 'not initialized');
    rimraf.sync(stickersDir);
  });
  ipcMain.handle(ERASE_DRAFTS_KEY, () => {
    strictAssert(draftDir != null, 'not initialized');
    rimraf.sync(draftDir);
  });
  ipcMain.handle(ERASE_DOWNLOADS_KEY, () => {
    strictAssert(downloadsDir != null, 'not initialized');
    rimraf.sync(downloadsDir);
  });

  ipcMain.handle(CLEANUP_ORPHANED_ATTACHMENTS_KEY, async () => {
    const start = Date.now();
    await cleanupOrphanedAttachments({ sql, userDataPath: configDir });
    const duration = Date.now() - start;
    console.log(`cleanupOrphanedAttachments: took ${duration}ms`);
  });

  ipcMain.handle(CLEANUP_DOWNLOADS_KEY, async () => {
    const start = Date.now();
    await deleteStaleDownloads(configDir);
    const duration = Date.now() - start;
    console.log(`cleanupDownloads: took ${duration}ms`);
  });

  protocol.handle('attachment', handleAttachmentRequest);
}

export async function handleAttachmentRequest(req: Request): Promise<Response> {
  const url = new URL(req.url);
  if (url.host !== 'v1' && url.host !== 'v2') {
    return new Response('Unknown host', { status: 404 });
  }

  // Disposition
  let disposition: z.infer<typeof dispositionSchema> = 'attachment';
  const dispositionParam = url.searchParams.get('disposition');
  if (dispositionParam != null) {
    disposition = dispositionSchema.parse(dispositionParam);
  }

  strictAssert(attachmentsDir != null, 'not initialized');
  strictAssert(tempDir != null, 'not initialized');
  strictAssert(draftDir != null, 'not initialized');
  strictAssert(stickersDir != null, 'not initialized');
  strictAssert(avatarDataDir != null, 'not initialized');

  let parentDir: string;
  switch (disposition) {
    case 'attachment':
      parentDir = attachmentsDir;
      break;
    case 'temporary':
      parentDir = tempDir;
      break;
    case 'draft':
      parentDir = draftDir;
      break;
    case 'sticker':
      parentDir = stickersDir;
      break;
    case 'avatarData':
      parentDir = avatarDataDir;
      break;
    default:
      throw missingCaseError(disposition);
  }

  // Remove first slash
  const path = normalize(
    join(parentDir, ...url.pathname.slice(1).split(/\//g))
  );
  if (!isPathInside(path, parentDir)) {
    return new Response('Access denied', { status: 401 });
  }

  // Get attachment size to trim the padding
  const sizeParam = url.searchParams.get('size');
  let maybeSize: number | undefined;
  if (sizeParam != null) {
    const intValue = safeParseInteger(sizeParam);
    if (intValue != null) {
      maybeSize = intValue;
    }
  }

  let context: RangeFinderContextType;

  // Legacy plaintext attachments
  if (url.host === 'v1') {
    context = {
      type: 'plaintext',
      path,
    };
  } else {
    // Encrypted attachments

    // Get AES+MAC key
    const maybeKeysBase64 = url.searchParams.get('key');
    if (maybeKeysBase64 == null) {
      return new Response('Missing key', { status: 400 });
    }

    // Size is required for trimming padding
    if (maybeSize == null) {
      return new Response('Missing size', { status: 400 });
    }

    context = {
      type: 'ciphertext',
      path,
      keysBase64: maybeKeysBase64,
      size: maybeSize,
    };
  }

  try {
    return handleRangeRequest({
      request: req,
      size: maybeSize,
      context,
    });
  } catch (error) {
    console.error('handleAttachmentRequest: error', Errors.toLogFormat(error));
    throw error;
  }
}

type HandleRangeRequestOptionsType = Readonly<{
  request: Request;
  size: number | undefined;
  context: RangeFinderContextType;
}>;

function handleRangeRequest({
  request,
  size,
  context,
}: HandleRangeRequestOptionsType): Response {
  const url = new URL(request.url);

  // Get content-type
  const contentTypeParam = url.searchParams.get('contentType');
  let contentType = MIMETypeToString(APPLICATION_OCTET_STREAM);
  if (contentTypeParam) {
    const mime = stringToMIMEType(contentTypeParam);
    if (isImageTypeSupported(mime) || isVideoTypeSupported(mime)) {
      contentType = MIMETypeToString(mime);
    }
  }

  const headers: HeadersInit = {
    'cache-control': 'no-cache, no-store',
    'content-type': contentType,
  };

  if (size != null) {
    headers['content-length'] = size.toString();
  }

  const create200Response = (): Response => {
    const plaintext = rangeFinder.get(0, context);
    return new Response(toWebStream(plaintext), {
      status: 200,
      headers,
    });
  };

  const range = request.headers.get('range');
  if (range == null) {
    return create200Response();
  }

  // Chromium only sends open-ended ranges: "start-"
  const match = range.match(/^bytes=(\d+)-$/);
  if (match == null) {
    console.error(`attachment_channel: invalid range header: ${range}`);
    return create200Response();
  }

  const startParam = safeParseInteger(match[1]);
  if (startParam == null) {
    console.error(`attachment_channel: invalid range header: ${range}`);
    return create200Response();
  }

  const start = Math.min(startParam, size || Infinity);

  headers['content-range'] = `bytes ${start}-/${size ?? '*'}`;

  if (size !== undefined) {
    headers['content-length'] = (size - start).toString();
  }

  const stream = rangeFinder.get(start, context);
  return new Response(toWebStream(stream), {
    status: 206,
    headers,
  });
}