From d63f89c134db12a3efcc09113733e5e85fb126de Mon Sep 17 00:00:00 2001
From: automated-signal <37887102+automated-signal@users.noreply.github.com>
Date: Wed, 17 Dec 2025 13:19:13 -0600
Subject: [PATCH] Minimize processing of forwarded attachments

Co-authored-by: Fedor Indutny <79877362+indutny-signal@users.noreply.github.com>
---
 ts/models/conversations.preload.ts      |  6 ++-
 ts/util/maybeForwardMessages.preload.ts |  2 +-
 ts/util/uploadAttachment.preload.ts     | 62 +++++++++++++++++++++----
 3 files changed, 58 insertions(+), 12 deletions(-)

diff --git a/ts/models/conversations.preload.ts b/ts/models/conversations.preload.ts
index 62da6f376c..4879fc430a 100644
--- a/ts/models/conversations.preload.ts
+++ b/ts/models/conversations.preload.ts
@@ -4100,12 +4100,14 @@ export class ConversationModel {
     },
     {
       dontClearDraft = false,
+      isForwarding = false,
       sendHQImages,
       storyId,
       timestamp,
       extraReduxActions,
     }: {
       dontClearDraft?: boolean;
+      isForwarding?: boolean;
       sendHQImages?: boolean;
       storyId?: string;
       timestamp?: number;
@@ -4176,7 +4178,7 @@ export class ConversationModel {
     // any attachments as well.
     let attachmentsToSend = preview && preview.length ? [] : attachments;
 
-    if (preview && preview.length) {
+    if (preview && preview.length && !isForwarding) {
       attachments.forEach(attachment => {
         if (attachment.path) {
           void deleteAttachmentData(attachment.path);
@@ -4197,7 +4199,7 @@ export class ConversationModel {
      * All draft attachments (with a path or just in-memory) will be written to disk for
      * real in `upgradeMessageSchema`.
      */
-    if (!sendHQImages) {
+    if (!sendHQImages && !isForwarding) {
       attachmentsToSend = await Promise.all(
         attachmentsToSend.map(async attachment => {
           const downscaledAttachment =
diff --git a/ts/util/maybeForwardMessages.preload.ts b/ts/util/maybeForwardMessages.preload.ts
index 36a49d9ad6..6cfacee475 100644
--- a/ts/util/maybeForwardMessages.preload.ts
+++ b/ts/util/maybeForwardMessages.preload.ts
@@ -80,7 +80,7 @@ export async function maybeForwardMessages(
     return false;
   }
 
-  const sendMessageOptions = { dontClearDraft: true };
+  const sendMessageOptions = { dontClearDraft: true, isForwarding: true };
   const baseTimestamp = Date.now();
 
   let timestampOffset = 0;
diff --git a/ts/util/uploadAttachment.preload.ts b/ts/util/uploadAttachment.preload.ts
index e9d09b051a..99cf41b5fa 100644
--- a/ts/util/uploadAttachment.preload.ts
+++ b/ts/util/uploadAttachment.preload.ts
@@ -6,6 +6,8 @@ import type {
   AttachmentWithHydratedData,
   UploadedAttachmentType,
 } from '../types/Attachment.std.js';
+import * as Bytes from '../Bytes.std.js';
+import { createLogger } from '../logging/log.std.js';
 import { MIMETypeToString, supportsIncrementalMac } from '../types/MIME.std.js';
 import { getRandomBytes } from '../Crypto.node.js';
 import { backupsService } from '../services/backups/index.preload.js';
@@ -25,24 +27,66 @@ import {
 } from '../AttachmentCrypto.node.js';
 import { missingCaseError } from './missingCaseError.std.js';
 import { uuidToBytes } from './uuidToBytes.std.js';
+import { DAY } from './durations/index.std.js';
 import { isVisualMedia } from './Attachment.std.js';
 import { getAbsoluteAttachmentPath } from './migrations.preload.js';
+import { isMoreRecentThan } from './timestamp.std.js';
 
 const CDNS_SUPPORTING_TUS = new Set([3]);
 
+const log = createLogger('uploadAttachment');
+
 export async function uploadAttachment(
   attachment: AttachmentWithHydratedData
 ): Promise<UploadedAttachmentType> {
-  const keys = getRandomBytes(64);
-  const needIncrementalMac = supportsIncrementalMac(attachment.contentType);
+  let keys: Uint8Array;
+  let cdnKey: string;
+  let cdnNumber: number;
+  let encrypted: Pick<
+    EncryptedAttachmentV2,
+    'digest' | 'plaintextHash' | 'incrementalMac' | 'chunkSize'
+  >;
+  let uploadTimestamp: number;
 
-  const uploadTimestamp = Date.now();
-  const { cdnKey, cdnNumber, encrypted } = await encryptAndUploadAttachment({
-    keys,
-    needIncrementalMac,
-    plaintext: { data: attachment.data },
-    uploadType: 'standard',
-  });
+  // Recently uploaded attachment
+  if (
+    attachment.cdnKey &&
+    attachment.cdnNumber &&
+    attachment.key &&
+    attachment.size != null &&
+    attachment.digest &&
+    attachment.contentType != null &&
+    attachment.plaintextHash != null &&
+    attachment.uploadTimestamp != null &&
+    isMoreRecentThan(attachment.uploadTimestamp, 3 * DAY)
+  ) {
+    log.info('reusing attachment uploaded at', attachment.uploadTimestamp);
+
+    ({ cdnKey, cdnNumber, uploadTimestamp } = attachment);
+
+    keys = Bytes.fromBase64(attachment.key);
+
+    encrypted = {
+      digest: Bytes.fromBase64(attachment.digest),
+      plaintextHash: attachment.plaintextHash,
+      incrementalMac: attachment.incrementalMac
+        ? Bytes.fromBase64(attachment.incrementalMac)
+        : undefined,
+      chunkSize: attachment.chunkSize,
+    };
+  } else {
+    keys = getRandomBytes(64);
+    uploadTimestamp = Date.now();
+
+    const needIncrementalMac = supportsIncrementalMac(attachment.contentType);
+
+    ({ cdnKey, cdnNumber, encrypted } = await encryptAndUploadAttachment({
+      keys,
+      needIncrementalMac,
+      plaintext: { data: attachment.data },
+      uploadType: 'standard',
+    }));
+  }
 
   const { blurHash, caption, clientUuid, flags, height, width } = attachment;