Adding a new config flag to disable pictrs caching for thumbnails (#3897)

* add logic to prevent downloading remote pictrs images

* apply formatting

* Do not attempt a pictrs fetch if the remote image is also on a pictrs instance

* Do not attempt a pictrs fetch if the remote image is also on a pictrs instance and cache_federated_images is false

* Generalising the no caching option to handle all remote images

* rustfmt

* Return None if the URL is not an image

* Updating defaults.hjson

* fixing typo

* Fixing typo

* Skip cloning the Url unless we need to

* using a HEAD request for checking the content type, saving bandwidth/improving perf

* Removing early returns

* Switching back to GET requests for Content-Type because pictrs does not handle HEAD requests

* Simplifying logic and using metadata_image instead of url if we do not get a pictrs thumbnail

* Removing unused import

* Return None as a thumbnail if caching is disabled

* formatting

---------

Co-authored-by: Djones4822 <david.jones4822@gmail.com>

config/defaults.hjson

@@ -43,6 +43,8 @@
     url: "http://localhost:8080/"
     # Set a custom pictrs API key. ( Required for deleting images )
     api_key: "string"
+    # Cache remote images
+    cache_remote_images: true
   }
   # Email sending configuration. All options except login/password are mandatory
   email: {

crates/api_common/src/request.rs

@@ -123,6 +123,8 @@ pub(crate) async fn fetch_pictrs(
   let pictrs_config = settings.pictrs_config()?;
   is_image_content_type(client, image_url).await?;
 
+  if pictrs_config.cache_remote_images {
+    // fetch remote non-pictrs images for persistent thumbnail link
     let fetch_url = format!(
       "{}image/download?url={}",
       pictrs_config.url,
@@ -142,6 +144,9 @@ pub(crate) async fn fetch_pictrs(
     } else {
       Err(LemmyErrorType::PictrsResponseError(response.msg))?
     }
+  } else {
+    Err(LemmyErrorType::PictrsCachingDisabled)?
+  }
 }
 
 /// Purges an image from pictrs
@@ -185,7 +190,7 @@ pub async fn purge_image_from_pictrs(
 }
 
 /// Both are options, since the URL might be either an html page, or an image
-/// Returns the SiteMetadata, and a Pictrs URL, if there is a picture associated
+/// Returns the SiteMetadata, and an image URL, if there is a picture associated
 #[tracing::instrument(skip_all)]
 pub async fn fetch_site_data(
   client: &ClientWithMiddleware,
@@ -200,50 +205,46 @@ pub async fn fetch_site_data(
       // Warning, this may ignore SSL errors
       let metadata_option = fetch_site_metadata(client, url).await.ok();
       if !include_image {
-        return (metadata_option, None);
+        (metadata_option, None)
+      } else {
+        let thumbnail_url =
+          fetch_pictrs_url_from_site_metadata(client, &metadata_option, settings, url)
+            .await
+            .ok();
+        (metadata_option, thumbnail_url)
       }
-
-      let missing_pictrs_file =
-        |r: PictrsResponse| r.files.first().expect("missing pictrs file").file.clone();
-
-      // Fetch pictrs thumbnail
-      let pictrs_hash = match &metadata_option {
-        Some(metadata_res) => match &metadata_res.image {
-          // Metadata, with image
-          // Try to generate a small thumbnail if there's a full sized one from post-links
-          Some(metadata_image) => fetch_pictrs(client, settings, metadata_image)
-            .await
-            .map(missing_pictrs_file),
-          // Metadata, but no image
-          None => fetch_pictrs(client, settings, url)
-            .await
-            .map(missing_pictrs_file),
-        },
-        // No metadata, try to fetch the URL as an image
-        None => fetch_pictrs(client, settings, url)
-          .await
-          .map(missing_pictrs_file),
-      };
-
-      // The full urls are necessary for federation
-      let pictrs_thumbnail = pictrs_hash
-        .map(|p| {
-          Url::parse(&format!(
-            "{}/pictrs/image/{}",
-            settings.get_protocol_and_hostname(),
-            p
-          ))
-          .ok()
-        })
-        .ok()
-        .flatten();
-
-      (metadata_option, pictrs_thumbnail.map(Into::into))
     }
     None => (None, None),
   }
 }
 
+async fn fetch_pictrs_url_from_site_metadata(
+  client: &ClientWithMiddleware,
+  metadata_option: &Option<SiteMetadata>,
+  settings: &Settings,
+  url: &Url,
+) -> Result<DbUrl, LemmyError> {
+  let pictrs_res = match metadata_option {
+    Some(metadata_res) => match &metadata_res.image {
+      // Metadata, with image
+      // Try to generate a small thumbnail if there's a full sized one from post-links
+      Some(metadata_image) => fetch_pictrs(client, settings, metadata_image).await,
+      // Metadata, but no image
+      None => fetch_pictrs(client, settings, url).await,
+    },
+    // No metadata, try to fetch the URL as an image
+    None => fetch_pictrs(client, settings, url).await,
+  }?;
+
+  Url::parse(&format!(
+    "{}/pictrs/image/{}",
+    settings.get_protocol_and_hostname(),
+    pictrs_res.files.first().expect("missing pictrs file").file
+  ))
+  .map(Into::into)
+  .map_err(Into::into)
+}
+
 #[tracing::instrument(skip_all)]
 async fn is_image_content_type(client: &ClientWithMiddleware, url: &Url) -> Result<(), LemmyError> {
   let response = client.get(url.as_str()).send().await?;

crates/utils/src/error.rs

@@ -87,6 +87,7 @@ pub enum LemmyErrorType {
   SiteMetadataPageIsNotDoctypeHtml,
   PictrsResponseError(String),
   PictrsPurgeResponseError(String),
+  PictrsCachingDisabled,
   ImageUrlMissingPathSegments,
   ImageUrlMissingLastPathSegment,
   PictrsApiKeyNotProvided,

crates/utils/src/settings/structs.rs

@@ -62,6 +62,10 @@ pub struct PictrsConfig {
   /// Set a custom pictrs API key. ( Required for deleting images )
   #[default(None)]
   pub api_key: Option<String>,
+
+  /// Cache remote images
+  #[default(true)]
+  pub cache_remote_images: bool,
 }
 
 #[derive(Debug, Deserialize, Serialize, Clone, SmartDefault, Document)]

docker/lemmy.hjson

@@ -21,6 +21,7 @@
   pictrs: {
     url: "http://pictrs:8080/"
     # api_key: "API_KEY"
+    cache_remote_images: true
   }
 
   #opentelemetry_url: "http://otel:4137"