Lemmy Support @lemmy.ml maltfield @monero.town 9 mo. ago

How to purge an image on Lemmy? (GDPR Data Erasure)

webmasters.stackexchange.com How to purge an image on Lemmy? (GDPR Data Erasure)

Given a URL to an image on my lemmy instance, how can I (as an admin) permanently delete the image (and all cache/variants of the image)? I operate a lemmy instance server. One of our users just

Given a URL to an image on my lemmy instance, how can I (as an admin) permanently delete the image (and all cache/variants of the image)?

I operate a lemmy instance server. One of our users just submitted a GDPR Data Erasure request for an image. The image is orphaned, so it is not tied to any post or comment. We have a URL to the image only.

Images in lemmy are handled by the pict-rs service, which is itself distinct from lemmy. As stated in the lemmy documentation, there is a way to purge posts and comments, but there appears to be no way to purge a given image in lemmy through the WUI or lemmy API.

How can I entirely purge the image from my lemmy instance, given only the URL to the image?

5 comments

You can call the delete endpoint with the pictrs token your lemmy instance is using to talk to pictrs.

It's quite well documented: https://crates.io/crates/pict-rs
- Thanks, but I'm asking because I didn't find the reference documentation especially helpful.
  
  It says I need the "delete token" or "alias". How do I get that for a given URL?
  
  I'm looking for an example that describes how to construct the commands for the API calls knowing only the URL of the image.
  
  Token is probably the guide in the url itself
This is a big problem. At the time of writing:

Users cannot delete their images on Lemmy

If a user deletes their account, their images don't get deleted

There is no WUI for admins to delete images on Lemmy

It is very difficult for admins to find & delete images on Lemmy (via the CLI)

The Lemmy team didn't bother documenting how admins can delete images on Lemmy

How to purge images in Lemmy

pict-rs is a third-party simple image hosting service that runs along-side Lemmy for instances that allow users to upload media.

At the time of writing, there is no WUI for admins to find and delete images. You have to manually query the pict-rs database and execute an API call from the command-line. Worse: Lemmy has no documentation telling instance admins how to delete images 🤦

For the purposes of this example, let's assume you're trying to delete the following image

https://monero.town/pictrs/image/001665df-3b25-415f-8a59-3d836bb68dd1.webp

There are two API endpoints in pict-rs that can be used to delete an image

Method One: /image/delete/{delete_token}/{alias}

This API call is publicly-accessible, but it first requires you to obtain the image's `delete_token`

The `delete_token` is first returned by Lemmy when POSTing to the `/pictrs/image` endpoint

{ "msg":"ok", "files":[ { "file":"001665df-3b25-415f-8a59-3d836bb68dd1.webp", "delete_token":"d88b7f32-a56f-4679-bd93-4f334764d381" } ] }

Two pieces of information are returned here:

file (aka the "alias") is the server filename of the uploaded image

delete_token is the token needed to delete the image

Of course, if you didn't capture this image's `delete_token` at upload-time, then you must fetch it from the postgres DB.

First, open a shell on your running postgres container. If you installed Lemmy with docker compose, use `docker compose ps` to get the "SERVICE" name of your postgres host, and then enter it with `docker exec`

docker compose ps --format "table {{.Service}}\t{{.Image}}\t{{.Name}}" docker compose exec <docker_service_name> /bin/bash

For example:

user@host:/home/user/lemmy# docker compose ps --format "table {{.Service}}\t{{.Image}}\t{{.Name}}" SERVICE IMAGE NAME lemmy dessalines/lemmy:0.19.3 lemmy-lemmy-1 lemmy-ui dessalines/lemmy-ui:0.19.3 lemmy-lemmy-ui-1 pictrs docker.io/asonix/pictrs:0.5.4 lemmy-pictrs-1 postfix docker.io/mwader/postfix-relay lemmy-postfix-1 postgres docker.io/postgres:15-alpine lemmy-postgres-1 proxy docker.io/library/nginx lemmy-proxy-1 user@host:/home/user/lemmy# user@host:/home/user/lemmy# docker compose exec postgres /bin/bash postgres:/#

Connect to the database as the `lemmy` user

psql -U lemmy

For example

postgres:/# psql -U lemmy psql (15.5) Type "help" for help. lemmy=#

Query for the image by the "alias" (the filename)

select * from image_upload where pictrs_alias = '<image_filename>';

For example

lemmy=# select * from image_upload where pictrs_alias = '001665df-3b25-415f-8a59-3d836bb68dd1.webp'; local_user_id | pictrs_alias | pictrs_delete_token | published ---------------+--------------+---------------------+----------- 1149 | 001665df-3b25-415f-8a59-3d836bb68dd1.webp | d88b7f32-a56f-4679-bd93-4f334764d381 | 2024-02-07 11:10:17.158741+00 (1 row) lemmy=#

Now, take the `pictrs_delete_token` from the above output, and use it to delete the image.

The following command should be able to be run on any computer connected to the internet.

curl -i "https://<instance_domain>/pictrs/image/delete/<pictrs_delete_token>/<image_filename>"

For example:

user@disp9140:~$ curl -i "https://monero.town/pictrs/image/delete/d88b7f32-a56f-4679-bd93-4f334764d381/001665df-3b25-415f-8a59-3d836bb68dd1.webp" HTTP/2 204 No Content server: nginx date: Fri, 09 Feb 2024 15:37:48 GMT vary: Origin, Access-Control-Request-Method, Access-Control-Request-Headers cache-control: private referrer-policy: same-origin x-content-type-options: nosniff x-frame-options: DENY x-xss-protection: 1; mode=block X-Firefox-Spdy: h2 user@disp9140:~$

ⓘ Note: If you get an `incorrect_login` error, then try [a] logging into the instance in your web browser and then [b] pasting the "https://<instance_domain>/pictrs/image/delete/<pictrs_delete_token>/<image_filename>" URL into your web browser.

The image should be deleted.

Method Two: /internal/purge?alias={alias}

Alternatively, you could execute the deletion directly inside the pictrs container. This eliminates the need to fetch the `delete_token`.

First, open a shell on your running `pictrs` container. If you installed Lemmy with docker compose, use `docker compose ps` to get the "SERVICE" name of your postgres host, and then enter it with `docker exec`

docker compose ps --format "table {{.Service}}\t{{.Image}}\t{{.Name}}" docker compose exec <docker_service_name> /bin/sh

For example:

user@host:/home/user/lemmy# docker compose ps --format "table {{.Service}}\t{{.Image}}\t{{.Name}}" SERVICE IMAGE NAME lemmy dessalines/lemmy:0.19.3 lemmy-lemmy-1 lemmy-ui dessalines/lemmy-ui:0.19.3 lemmy-lemmy-ui-1 pictrs docker.io/asonix/pictrs:0.5.4 lemmy-pictrs-1 postfix docker.io/mwader/postfix-relay lemmy-postfix-1 postgres docker.io/postgres:15-alpine lemmy-postgres-1 proxy docker.io/library/nginx lemmy-proxy-1 user@host:/home/user/lemmy# user@host:/home/user/lemmy# docker compose exec pictrs /bin/sh ~ $

Execute the following command inside the `pictrs` container.

wget --server-response --post-data "" --header "X-Api-Token: ${PICTRS__SERVER__API_KEY}" "http://127.0.0.1:8080/internal/purge?alias=<image_filename>"

For example:

~ $ wget --server-response --post-data "" --header "X-Api-Token: ${PICTRS__SERVER__API_KEY}" "http://127.0.0.1:8080/internal/purge?alias=001665df-3b25-415f-8a59-3d836bb68dd1.webp" Connecting to 127.0.0.1:8080 (127.0.0.1:8080) HTTP/1.1 200 OK content-length: 67 connection: close content-type: application/json date: Wed, 14 Feb 2024 12:56:24 GMT saving to 'purge?alias=001665df-3b25-415f-8a59-3d836bb68dd1.webp' purge?alias=001665df 100% |*****************************************************************************************************************************************************************************************************************************| 67 0:00:00 ETA 'purge?alias=001665df-3b25-415f-8a59-3d836bb68dd1.webp' saved ~ $

ⓘ Note: There's an error in the pict-rs reference documentation. It says you can POST to `/internal/delete`, but that just returns 404 Not Found.

The image should be deleted

Further Reading

Unfortunately, it seems that the Lemmy develoeprs are not taking these moral and legal (GDPR) risks seriously (they said it may take years before they address them), and they threatened to ban me for trying to highlight the severity of this risk, get them to tag GDPR-related bugs, and to prioritize them.

lemmy #4433: Deleted Account should delete uploaded media (pictures) too

lemmy #4441: Users unable to delete their images (pictrs API)

lemmy #4434: Unapproved users cannot delete their accounts/data

lemmy #3973: Banned users cannot delete their accounts/data

lemmy #4445: Create an interface for local users to view and remove images

lemmy-ui #2359: Allow users to delete images they uploaded

lemmy-ui #2360: Allow admins to view & delete uploaded images

lemmy-ui #2361: private_message_disclaimer to include user's matrix handle

jerboa #1361: UI for deleting uploaded files

jerboa #1362: Setting to hide "upload media" button

jerboa #1363: Add "confirm upload" step to UX

lemmy-docs #293: Document image moderation

If GDPR-compliance is important to you on the fediverse, then please provide feedback to the Lemmy developers in the GitHub links above.

Attribution

This comment was copied from the following article: Nightmare on Lemmy Street (A Fediverse GDPR Horror Story)

Nightmare on Lemmy Street (A Fediverse GDPR Horror Story)

https://tech.michaelaltfield.net/2024/03/04/lemmy-fediverse-gdpr/