Prefer Group actor when doing webfinger query on Lemmy server

CHANGELOG.md

@@ -15,12 +15,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Deprecated
 
-- Deprecated `proxy_url` configuration paramter (replaced by `federation.proxy_url`).
+- Deprecated `proxy_url` configuration parameter (replaced by `federation.proxy_url`).
 
 ### Fixed
 
 - Prevent `delete-extraneous-posts` command from removing locally-linked posts.
 - Make webfinger response compatible with GNU Social account lookup.
+- Prefer `Group` actor when doing webfinger query on Lemmy server.
 
 ## [1.14.0] - 2023-02-22
 

src/activitypub/fetcher/fetchers.rs

@@ -12,9 +12,10 @@ use mitra_utils::{
 
 use crate::activitypub::{
     actors::types::Actor,
-    constants::AP_MEDIA_TYPE,
+    constants::{AP_CONTEXT, AP_MEDIA_TYPE},
     identifiers::{local_actor_key_id, local_instance_actor_id},
     types::Object,
+    vocabulary::GROUP,
 };
 use crate::http_signatures::create::{
     create_http_signature,
@@ -183,11 +184,28 @@ pub async fn perform_webfinger_query(
         .error_for_status()?
         .text().await?;
     let jrd: JsonResourceDescriptor = serde_json::from_str(&webfinger_data)?;
-    let link = jrd.links.into_iter()
-        .find(|link| link.rel == "self")
-        .ok_or(FetchError::OtherError("self link not found"))?;
-    let actor_url = link.href
-        .ok_or(FetchError::OtherError("account href not found"))?;
+    // Lemmy servers can have Group and Person actors with the same name
+    // https://github.com/LemmyNet/lemmy/issues/2037
+    let ap_type_property = format!("{}#type", AP_CONTEXT);
+    let group_link = jrd.links.iter()
+        .find(|link| {
+            link.rel == "self" &&
+            link.properties
+                .get(&ap_type_property)
+                .map(|val| val.as_str()) == Some(GROUP)
+        });
+    let link = if let Some(link) = group_link {
+        // Prefer Group if the actor type is provided
+        link
+    } else {
+        // Otherwise take first "self" link
+        jrd.links.iter()
+            .find(|link| link.rel == "self")
+            .ok_or(FetchError::OtherError("self link not found"))?
+    };
+    let actor_url = link.href.as_ref()
+        .ok_or(FetchError::OtherError("account href not found"))?
+        .to_string();
     Ok(actor_url)
 }
 

src/activitypub/vocabulary.rs

@@ -18,6 +18,7 @@ pub const UNDO: &str = "Undo";
 pub const UPDATE: &str = "Update";
 
 // Actor types
+pub const GROUP: &str = "Group";
 pub const PERSON: &str = "Person";
 pub const SERVICE: &str = "Service";
 

src/nodeinfo/views.rs

@@ -22,6 +22,7 @@ pub async fn get_nodeinfo(
         rel: "http://nodeinfo.diaspora.software/ns/schema/2.0".to_string(),
         media_type: None,
         href: Some(nodeinfo_2_0_url),
+        properties: Default::default(),
     };
     let jrd = JsonResourceDescriptor {
         subject: config.instance_url(),

src/webfinger/types.rs

@@ -1,6 +1,9 @@
 /// https://webfinger.net/
-use std::fmt;
-use std::str::FromStr;
+use std::{
+    collections::HashMap,
+    fmt,
+    str::FromStr,
+};
 
 use regex::Regex;
 use serde::{Serialize, Deserialize};
@@ -63,6 +66,9 @@ pub struct Link {
     pub media_type: Option<String>,
 
     pub href: Option<String>,
+
+    #[serde(default, skip_serializing_if = "HashMap::is_empty")]
+    pub properties: HashMap<String, String>,
 }
 
 // https://datatracker.ietf.org/doc/html/rfc7033#section-4.4

src/webfinger/views.rs

@@ -62,11 +62,13 @@ async fn get_jrd(
         rel: "http://webfinger.net/rel/profile-page".to_string(),
         media_type: Some("text/html".to_string()),
         href: Some(actor_id.clone()),
+        properties: Default::default(),
     };
     let link_actor = Link {
         rel: "self".to_string(),
         media_type: Some(AP_MEDIA_TYPE.to_string()),
         href: Some(actor_id),
+        properties: Default::default(),
     };
     let jrd = JsonResourceDescriptor {
         subject: format!("acct:{}", actor_address),