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I just developed and published a script to clear your pict-rs object storage from potential CSAM. (github.com)

submitted 1 year ago* (last edited 1 year ago) by [email protected] to c/selfhosted

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I noticed a bit of panic around here lately and as I have had to continuously fight against pedos for the past year, I have developed tools to help me detect and prevent this content.

As luck would have it, we recently published one of our anti-csam checker tool as a python library that anyone can use. So I thought I could use this to help lemmy admins feel a bit more safe.

The tool can either go through all your images via your object storage and delete all CSAM, or it canrun continuously and scan and delete all new images as well. Suggested option is to run it using --all once, and then run it as a daemon and leave it running.

Better options would be to be able to retrieve exact images uploaded via lemmy/pict-rs api but we're not there quite yet.

Let me know if you have any issue or improvements.

EDIT: Just to clarify, you should run this on your desktop PC with a GPU, not on your lemmy server!

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[–] rcmaehl 18 points 1 year ago* (last edited 1 year ago) (1 children)

Hi db0, if I could make an additional suggestion.

Add detection of additional content appended or attached to media files. Pict-rs does not reprocess all media types on upload and it's not hard to attach an entire .zip file or other media within an image (https://wiki.linuxquestions.org/wiki/Embed_a_zip_file_into_an_image)

[–] [email protected] 19 points 1 year ago (2 children)

Currently I delete on PIL exceptions. I assume if someone uploaded a .zip to your image storage, you'd want it deleted

[–] Starbuck 11 points 1 year ago (1 children)

The fun part is that it’s still a valid JPEG file if you put more data in it. The file should be fully re-encoded to be sure.

[–] [email protected] 4 points 1 year ago (1 children)

In that case, PIL should be able to read it, so no worries

[–] Starbuck 6 points 1 year ago (1 children)

But I could take ‘flower.jpg’, which is an actual flower, and embed a second image, ‘csam.png’ inside it. Your scanner would scan ‘flower.jpg’, find it to be acceptable, then in turn register ‘csam.png’. Not saying that this isn’t a great start, but this is the reason that a lot of websites that allow uploads re-encode images.

[–] [email protected] 8 points 1 year ago (1 children)

my pict-rs already re-encodes everything. This is already a possibility for lemmy admins

[–] Starbuck 2 points 1 year ago

Good to hear they have that covered already. Looks like a great tool!

[–] rcmaehl 5 points 1 year ago

As @[email protected] stated. They're still valid image files, they just have extra data.