From 6eca5ee9401f106225de5a782804623e5e3a0b9e Mon Sep 17 00:00:00 2001
From: Daniel Gasienica <daniel@signal.org>
Date: Mon, 30 Apr 2018 15:57:45 -0400
Subject: [PATCH] Document that JPEG auto-orient strips EXIF metadata

---
 js/modules/types/attachment.js | 2 ++
 js/modules/types/message.js    | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/js/modules/types/attachment.js b/js/modules/types/attachment.js
index 1a92cd8f0..5010f87fc 100644
--- a/js/modules/types/attachment.js
+++ b/js/modules/types/attachment.js
@@ -47,6 +47,8 @@ exports.isValid = rawAttachment => {
 };
 
 // Upgrade steps
+// NOTE: This step strips all EXIF metadata from JPEG images as
+// part of re-encoding the image:
 exports.autoOrientJPEG = async attachment => {
   if (!MIME.isJPEG(attachment.contentType)) {
     return attachment;
diff --git a/js/modules/types/message.js b/js/modules/types/message.js
index 79f3abf90..1c5ddb89a 100644
--- a/js/modules/types/message.js
+++ b/js/modules/types/message.js
@@ -16,6 +16,8 @@ const PRIVATE = 'private';
 //   - Schema initialized
 // Version 1
 //   - Attachments: Auto-orient JPEG attachments using EXIF `Orientation` data.
+//     N.B. The process of auto-orient for JPEGs strips (loses) all existing
+//     EXIF metadata improving privacy, e.g. geolocation, camera make, etc.
 // Version 2
 //   - Attachments: Sanitize Unicode order override characters.
 // Version 3