[bug] Some pngs give error error decoding image: image: unknown format

[mirabilos]

Describe the bug with a clear and concise description of what the bug is.

I was just looking at logs and:

timestamp="2023-11-07T04:43:39.068Z" func=dereferencing.(*deref).enrichAccount level=ERROR requestID=jzfhfa4b04000c030v60 msg="error fetching remote avatar for account https://social.handlerug.me/users/handlerug: fetchRemoteAccountAvatar: error loading attachment https://social.handlerug.me/fileserver/01QP5CG9VADMWT4Q08PW6CCYX3/attachment/original/01EANG35MK1P379GGQ8CA0XPJB.png: finish: error decoding image: image: unknown format"

Well… file(1) knows it as…

01EANG35MK1P379GGQ8CA0XPJB.png: PNG image data, 256 x 256, 8-bit/color RGB, non-interlaced

… and xloadimage displays it just fine.

What's your GoToSocial Version?

0.12.1 git-5fdc005

GoToSocial Arch

amd64 binary

What happened?

No response

What you expected to happen?

No response

How to reproduce it?

No response

Anything else we need to know?

No response

[tsmethurst]

Ah interesting, yep I can replicate it on latest snapshot. Looks like an issue with the library we use for detecting file formats.

EDIT: actually it looks like the error is coming from Go's image package...

EDIT2: or the file is not being put into storage at all, which is why it can't be decoded afterwards, I'll have to poke at this

[tsmethurst]

Ah interesting, I tried downloading the image to my own computer from that instance, then uploading it as a media attachment on a locally-running GtS instance, and I get the same error...

[mirabilos]

tobi dixit:

Ah interesting, I tried downloading the image to my own computer from that instance, then uploading it as a media attachment on a locally-running GtS instance, and I get the same error...

I also had a video today that wouldn’t show up but was viewable from the remote instance; should I hunt that down so you have more examples of misdetected media? bye, //mirabilos

[tsmethurst]

I also had a video today that wouldn’t show up but was viewable from
the remote instance; should I hunt that down so you have more examples
of misdetected media?

No that's fine, thanks. We've already got a fix for that sort of issue in the works.

[tsmethurst]

Bit more of a writeup on this after looking at it a bit more:

The reason it returns unknown format error during finish is because it's trying to decode an image of 0 bytes.

In other words: the png was not stored, but nor did writing 0 bytes into storage return any errors.

I think the reason it's not being stored is because exif terminator is overzealously terminating the entire image as it's being streamed into storage. I'll have to do a bit more investigation of this to determine why that is the case. Doesn't make a lot of sense for it to do that, so I'm assuming it's a bug either in exif terminator, or in the png structure library that exif terminator depends on.

[tsmethurst]

https://github.com/superseriousbusiness/exif-terminator/issues/5

[tsmethurst]

Got a fix for this in the works now: superseriousbusiness/exif-terminator#6