og:image preview bails out if Content-Length header is missing, many image CDNs use streaming or chunked encoding now

[jonsherrard]

• I have searched open and closed issues for duplicates

• I am using Signal-Desktop as provided by the Signal team, not a 3rd-party package.

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Bug Description

Steps to Reproduce

1. step one
   Open a chat
2. step two
   Paste https://vercel.com/docs/functions/edge-functions/og-image-generation
3. step three
   Notice there is no OG image loaded.

Actual Result:

No image preview is laoded in the chat is because vercel's image servers don't set a content-length, so it bails out:

Signal-Desktop/ts/linkPreviews/linkPreviewFetch.ts

Line 539 in 172598b

if (contentLength > MAX_IMAGE_CONTENT_LENGTH) {

Expected Result:

The image preview should load.

Screenshots

Signal:

Other chat app:

Platform Info

Signal Version:

6.34.1
production (Apple silicon)

Operating System:

14.0 (23A344)

Linked Device Version:

[der-eismann]

We just stumbled upon the same issue with our website, where we serve images from CloudFront with compression enabled. Since CloudFront dismisses the Content-Length header on compressed requests, we are not getting any preview images.
Would be great if we could find a solution for this, especially since the mobile app is not affected by this.

FTR these are the headers served by CloudFront:

< HTTP/2 200 
< content-type: image/jpeg
< date: Wed, 09 Oct 2024 16:49:57 GMT
< cache-control: max-age=315360000,public
< etag: "3b0c79e2613…"
< expires: Sat, 07 Oct 2034 16:49:57 GMT
< vary: Accept
< x-cache: Miss from cloudfront
< via: 1.1 ….cloudfront.net (CloudFront)
< x-amz-cf-pop: …
< alt-svc: h3=":443"; ma=86400
< x-amz-cf-id: skD88pp1R…

[ryan-williams]

This issue has driven me crazy, for years(?). OG images for my sites are frequently broken on Signal macOS and Android.

I hope someone reviews #7046 soon, it's been open for over 6 months. cc @scottnonnenberg-signal.

Here's a simple example: https://runsascoded.s3.amazonaws.com/og/test1.html. The og:image works in every service I've tried:

Facebook/X/LinkedIn/Discord ✅

c/o opengraph.xyz:

WhatsApp ✅

Slack ✅

but Signal Desktop or Android are broken ❌:

Last time I hit this (signalapp/Signal-iOS#5559 (comment)), switching PNG to JPG fixed it for some reason, but that's not working for me this time.