From 0ebeb5aa92cfdeefc7dfd43e94ef1198fe425df9 Mon Sep 17 00:00:00 2001
From: Greyson Parrelli <greyson@signal.org>
Date: Mon, 8 Jun 2026 11:54:38 -0400
Subject: [PATCH] Restrict S3 downloads to ReleaseChannel.

---
 .../contactshare/ContactModelMapper.java          |  9 +++++++--
 .../securesms/jobs/AttachmentDownloadJob.kt       | 15 ++++++++++++++-
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/app/src/main/java/org/thoughtcrime/securesms/contactshare/ContactModelMapper.java b/app/src/main/java/org/thoughtcrime/securesms/contactshare/ContactModelMapper.java
index 8ca512b920..0293a3a759 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/contactshare/ContactModelMapper.java
+++ b/app/src/main/java/org/thoughtcrime/securesms/contactshare/ContactModelMapper.java
@@ -5,6 +5,7 @@ import androidx.annotation.Nullable;
 
 import org.signal.core.util.logging.Log;
 import org.thoughtcrime.securesms.attachments.Attachment;
+import org.thoughtcrime.securesms.attachments.Cdn;
 import org.thoughtcrime.securesms.attachments.PointerAttachment;
 import org.whispersystems.signalservice.api.InvalidMessageStructureException;
 import org.whispersystems.signalservice.api.messages.SignalServiceAttachmentPointer;
@@ -119,9 +120,13 @@ public class ContactModelMapper {
       try {
         SignalServiceAttachmentPointer attachmentPointer = AttachmentPointerUtil.createSignalAttachmentPointer(contact.avatar.avatar);
         Attachment                     attachment        = PointerAttachment.forPointer(Optional.of(attachmentPointer.asPointer())).get();
-        boolean                        isProfile         = Boolean.TRUE.equals(contact.avatar.isProfile);
 
-        avatar = new Avatar(null, attachment, isProfile);
+        if (attachment.cdn == Cdn.S3) {
+          Log.w(TAG, "Ignoring contact avatar that resolves to the internal release-channel CDN.");
+        } else {
+          boolean isProfile = Boolean.TRUE.equals(contact.avatar.isProfile);
+          avatar = new Avatar(null, attachment, isProfile);
+        }
       } catch (InvalidMessageStructureException e) {
         Log.w(TAG, "Unable to create avatar for contact", e);
       }
diff --git a/app/src/main/java/org/thoughtcrime/securesms/jobs/AttachmentDownloadJob.kt b/app/src/main/java/org/thoughtcrime/securesms/jobs/AttachmentDownloadJob.kt
index 1401390f4a..abe179ae68 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/jobs/AttachmentDownloadJob.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/jobs/AttachmentDownloadJob.kt
@@ -235,7 +235,14 @@ class AttachmentDownloadJob private constructor(
     SignalDatabase.attachments.setTransferState(messageId, attachmentId, AttachmentTable.TRANSFER_PROGRESS_STARTED)
 
     when (attachment.cdn) {
-      Cdn.S3 -> retrieveAttachmentForReleaseChannel(messageId, attachmentId, attachment)
+      Cdn.S3 -> {
+        if (!isReleaseChannelMessage(messageId)) {
+          Log.w(TAG, "Refusing to download an S3 attachment for a message that is not from the release channel.")
+          markPermanentlyFailed(messageId, attachmentId)
+          return
+        }
+        retrieveAttachmentForReleaseChannel(messageId, attachmentId, attachment)
+      }
       else -> retrieveAttachment(messageId, attachmentId, attachment)
     }
 
@@ -467,6 +474,12 @@ class AttachmentDownloadJob private constructor(
     }
   }
 
+  private fun isReleaseChannelMessage(messageId: Long): Boolean {
+    val releaseChannelRecipientId = SignalStore.releaseChannel.releaseChannelRecipientId ?: return false
+    val messageRecord = SignalDatabase.messages.getMessageRecordOrNull(messageId) ?: return false
+    return messageRecord.fromRecipient.id == releaseChannelRecipientId
+  }
+
   private fun markFailed(messageId: Long, attachmentId: AttachmentId) {
     SignalDatabase.attachments.setTransferProgressFailed(attachmentId, messageId)
   }