Revert Object trait id() ref

* Accept Public aliases in URL deserializer

Update deserialize_one_or_many to deserialize recipient URL fields while
accepting `Public` and `as:Public` as aliases for the canonical
ActivityStreams public URL.

Add focused tests for single and array inputs, and verify that unrelated
string fields such as `content` are left unchanged.

https://github.com/LemmyNet/lemmy/issues/6465

* Deduplicate deserialized recipients

Drop repeated recipient URLs after deserialization so equivalent public
aliases such as `Public`, `as:Public`, and the canonical public URL do
not produce duplicate entries.

Update the helper documentation and tests to match the deduplicated
result.

.woodpecker.yml

@@ -1,5 +1,5 @@
 variables:
-  - &rust_image "rust:1.81-bullseye"
+  - &rust_image "rust:1.91-bullseye"
 
 steps:
   cargo_fmt:

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "activitypub_federation"
-version = "0.7.0-beta.6"
+version = "0.7.0-beta.11"
 edition = "2021"
 description = "High-level Activitypub framework"
 keywords = ["activitypub", "activitystreams", "federation", "fediverse"]
@@ -14,10 +14,6 @@ actix-web = ["dep:actix-web", "dep:http02"]
 axum = ["dep:axum", "dep:tower"]
 axum-original-uri = ["dep:axum", "axum/original-uri"]
 
-[lints.rust]
-warnings = "deny"
-deprecated = "deny"
-
 [lints.clippy]
 perf = { level = "deny", priority = -1 }
 complexity = { level = "deny", priority = -1 }
@@ -32,69 +28,71 @@ redundant_closure_for_method_calls = "deny"
 unwrap_used = "deny"
 
 [dependencies]
-chrono = { version = "0.4.41", features = ["clock"], default-features = false }
+chrono = { version = "0.4.42", features = ["clock"], default-features = false }
-serde = { version = "1.0.219", features = ["derive"] }
+serde = { version = "1.0.228", features = ["derive"] }
-async-trait = "0.1.88"
+async-trait = "0.1.89"
-url = { version = "2.5.4", features = ["serde"] }
+url = { version = "2.5.8", features = ["serde"] }
-serde_json = { version = "1.0.140", features = ["preserve_order"] }
+serde_json = { version = "1.0.149", features = ["preserve_order"] }
-reqwest = { version = "0.12.18", default-features = false, features = [
+reqwest = { version = "0.13.1", default-features = false, features = [
   "json",
   "stream",
-  "rustls-tls",
 ] }
-reqwest-middleware = "0.4.2"
+reqwest-middleware = "0.5.0"
-tracing = "0.1.41"
+tracing = "0.1.44"
 base64 = "0.22.1"
 rand = "0.8.5"
-rsa = "0.9.8"
+rsa = "0.9.10"
-http = "1.3.1"
+http = "1.4.0"
 sha2 = { version = "0.10.9", features = ["oid"] }
-thiserror = "2.0.12"
+thiserror = "2.0.17"
 derive_builder = "0.20.2"
 itertools = "0.14.0"
-dyn-clone = "1.0.19"
+dyn-clone = "1.0.20"
 enum_delegate = "0.2.0"
 httpdate = "1.0.3"
-http-signature-normalization-reqwest = { version = "0.13.0", default-features = false, features = [
+http-signature-normalization-reqwest = { version = "0.14.0", default-features = false, features = [
   "sha-2",
   "middleware",
   "default-spawner",
 ] }
 http-signature-normalization = "0.7.0"
-bytes = "1.10.1"
+bytes = "1.11.0"
 futures-core = { version = "0.3.31", default-features = false }
 pin-project-lite = "0.2.16"
 activitystreams-kinds = "0.3.0"
-regex = { version = "1.11.1", default-features = false, features = [
+regex = { version = "1.12.2", default-features = false, features = [
   "std",
   "unicode",
 ] }
-tokio = { version = "1.45.0", features = [
+tokio = { version = "1.49.0", features = [
   "sync",
   "rt",
   "rt-multi-thread",
   "time",
 ] }
 futures = "0.3.31"
-moka = { version = "0.12.10", features = ["future"] }
+moka = { version = "0.12.12", features = ["future"] }
 either = "1.15.0"
 
 # Actix-web
-actix-web = { version = "4.11.0", default-features = false, optional = true }
+actix-web = { version = "4.12.1", default-features = false, optional = true }
 http02 = { package = "http", version = "0.2.12", optional = true }
 
 # Axum
-axum = { version = "0.8.4", features = [
+axum = { version = "0.8.8", features = [
   "json",
 ], default-features = false, optional = true }
 tower = { version = "0.5.2", optional = true }
 
 [dev-dependencies]
-anyhow = "1.0.98"
+anyhow = "1.0.100"
-axum = { version = "0.8.4", features = ["macros"] }
+axum = { version = "0.8.8", features = ["macros"] }
-axum-extra = { version = "0.10.1", features = ["typed-header"] }
+axum-extra = { version = "0.12.5", features = ["typed-header"] }
 env_logger = "0.11.8"
-tokio = { version = "1.45.0", features = ["full"] }
+tokio = { version = "1.49.0", features = ["full"] }
+reqwest = { version = "0.13.1",features = [
+  "rustls"
+] }
 
 [profile.dev]
 strip = "symbols"

docs/10_fetching_objects_with_unknown_type.md

@@ -32,10 +32,10 @@ impl Object for SearchableDbObjects {
     type Kind = SearchableObjects;
     type Error = anyhow::Error;
 
-    fn id(&self) -> &Url {
+    fn id(&self) -> Url {
         match self {
-            SearchableDbObjects::User(p) => &p.federation_id,
+            SearchableDbObjects::User(p) => p.federation_id.clone(),
-            SearchableDbObjects::Post(n) => &n.federation_id,
+            SearchableDbObjects::Post(n) => n.federation_id.clone(),
         }
     }
 

examples/live_federation/main.rs

@@ -55,8 +55,8 @@ async fn main() -> Result<(), Error> {
     info!("Listen with HTTP server on {BIND_ADDRESS}");
     let config = config.clone();
     let app = Router::new()
-        .route("/:user", get(http_get_user))
+        .route("/{user}", get(http_get_user))
-        .route("/:user/inbox", post(http_post_user_inbox))
+        .route("/{user}/inbox", post(http_post_user_inbox))
         .route("/.well-known/webfinger", get(webfinger))
         .layer(FederationMiddleware::new(config));
 

examples/live_federation/objects/person.rs

@@ -69,8 +69,8 @@ impl Object for DbUser {
     type Kind = Person;
     type Error = Error;
 
-    fn id(&self) -> &Url {
+    fn id(&self) -> Url {
-        self.ap_id.inner()
+        self.ap_id.inner().clone()
     }
 
     fn last_refreshed_at(&self) -> Option<DateTime<Utc>> {

examples/live_federation/objects/post.rs

@@ -50,8 +50,8 @@ impl Object for DbPost {
     type Kind = Note;
     type Error = Error;
 
-    fn id(&self) -> &Url {
+    fn id(&self) -> Url {
-        self.ap_id.inner()
+        self.ap_id.inner().clone()
     }
 
     async fn read_from_id(

examples/local_federation/objects/person.rs

@@ -134,8 +134,8 @@ impl Object for DbUser {
     type Kind = Person;
     type Error = Error;
 
-    fn id(&self) -> &Url {
+    fn id(&self) -> Url {
-        self.ap_id.inner()
+        self.ap_id.inner().clone()
     }
 
     fn last_refreshed_at(&self) -> Option<DateTime<Utc>> {

examples/local_federation/objects/post.rs

@@ -47,8 +47,8 @@ impl Object for DbPost {
     type Kind = Note;
     type Error = Error;
 
-    fn id(&self) -> &Url {
+    fn id(&self) -> Url {
-        self.ap_id.inner()
+        self.ap_id.inner().clone()
     }
 
     async fn read_from_id(

src/activity_queue.rs

@@ -33,10 +33,10 @@ use url::Url;
 ///
 /// - `activity`: The activity to be sent, gets converted to json
 /// - `private_key`: Private key belonging to the actor who sends the activity, for signing HTTP
-///                  signature. Generated with [crate::http_signatures::generate_actor_keypair].
+///   signature. Generated with [crate::http_signatures::generate_actor_keypair].
 /// - `inboxes`: List of remote actor inboxes that should receive the activity. Ignores local actor
-///              inboxes. Should be built by calling [crate::traits::Actor::shared_inbox_or_inbox]
+///   inboxes. Should be built by calling [crate::traits::Actor::shared_inbox_or_inbox]
-///              for each target actor.
+///   for each target actor.
 pub async fn queue_activity<A, Datatype, ActorType>(
     activity: &A,
     actor: &ActorType,

src/activity_sending.rs

@@ -52,8 +52,8 @@ impl SendActivityTask {
     ///
     /// - `activity`: The activity to be sent, gets converted to json
     /// - `inboxes`: List of remote actor inboxes that should receive the activity. Ignores local actor
-    ///              inboxes. Should be built by calling [crate::traits::Actor::shared_inbox_or_inbox]
+    ///   inboxes. Should be built by calling [crate::traits::Actor::shared_inbox_or_inbox]
-    ///              for each target actor.
+    ///   for each target actor.
     pub async fn prepare<A, Datatype, ActorType>(
         activity: &A,
         actor: &ActorType,
@@ -190,7 +190,7 @@ where
     // PKey is internally like an Arc<>, so cloning is ok
     data.config
         .actor_pkey_cache
-        .try_get_with_by_ref(actor_id, async {
+        .try_get_with_by_ref(&actor_id, async {
             let private_key_pem = actor.private_key_pem().ok_or_else(|| {
                 Error::Other(format!(
                     "Actor {actor_id} does not contain a private key for signing"

src/actix_web/inbox.rs

@@ -22,7 +22,7 @@ pub async fn receive_activity<A, ActorT, Datatype>(
 ) -> Result<HttpResponse, <A as Activity>::Error>
 where
     A: Activity<DataType = Datatype> + DeserializeOwned + Send + 'static,
-    ActorT: Object<DataType = Datatype> + Actor + Send + 'static,
+    ActorT: Object<DataType = Datatype> + Actor + Send + Sync + 'static,
     for<'de2> <ActorT as Object>::Kind: serde::Deserialize<'de2>,
     <A as Activity>::Error: From<Error> + From<<ActorT as Object>::Error>,
     <ActorT as Object>::Error: From<Error>,
@@ -62,7 +62,7 @@ pub async fn receive_activity_with_hook<A, ActorT, Datatype>(
 ) -> Result<HttpResponse, <A as Activity>::Error>
 where
     A: Activity<DataType = Datatype> + DeserializeOwned + Send + Clone + 'static,
-    ActorT: Object<DataType = Datatype> + Actor + Send + Clone + 'static,
+    ActorT: Object<DataType = Datatype> + Actor + Send + Sync + Clone + 'static,
     for<'de2> <ActorT as Object>::Kind: serde::Deserialize<'de2>,
     <A as Activity>::Error: From<Error> + From<<ActorT as Object>::Error>,
     <ActorT as Object>::Error: From<Error>,
@@ -82,7 +82,7 @@ async fn do_stuff<A, ActorT, Datatype>(
 ) -> Result<(A, ActorT), <A as Activity>::Error>
 where
     A: Activity<DataType = Datatype> + DeserializeOwned + Send + 'static,
-    ActorT: Object<DataType = Datatype> + Actor + Send + 'static,
+    ActorT: Object<DataType = Datatype> + Actor + Send + Sync + 'static,
     for<'de2> <ActorT as Object>::Kind: serde::Deserialize<'de2>,
     <A as Activity>::Error: From<Error> + From<<ActorT as Object>::Error>,
     <ActorT as Object>::Error: From<Error>,

src/actix_web/mod.rs

@@ -23,7 +23,7 @@ pub async fn signing_actor<A>(
     data: &Data<<A as Object>::DataType>,
 ) -> Result<A, <A as Object>::Error>
 where
-    A: Object + Actor,
+    A: Object + Actor + Send + Sync,
     <A as Object>::Error: From<Error>,
     for<'de2> <A as Object>::Kind: Deserialize<'de2>,
 {

src/axum/inbox.rs

@@ -26,7 +26,7 @@ pub async fn receive_activity<A, ActorT, Datatype>(
 ) -> Result<(), <A as Activity>::Error>
 where
     A: Activity<DataType = Datatype> + DeserializeOwned + Send + 'static,
-    ActorT: Object<DataType = Datatype> + Actor + Send + 'static,
+    ActorT: Object<DataType = Datatype> + Actor + Send + Sync + 'static,
     for<'de2> <ActorT as Object>::Kind: serde::Deserialize<'de2>,
     <A as Activity>::Error: From<Error> + From<<ActorT as Object>::Error>,
     <ActorT as Object>::Error: From<Error>,

src/config.rs

@@ -20,6 +20,7 @@ use crate::{
     http_signatures::sign_request,
     protocol::verification::verify_domains_match,
     traits::{Activity, Actor},
+    utils::validate_ip,
 };
 use async_trait::async_trait;
 use bytes::Bytes;
@@ -32,7 +33,6 @@ use reqwest_middleware::{ClientWithMiddleware, RequestBuilder};
 use rsa::{pkcs8::DecodePrivateKey, RsaPrivateKey};
 use serde::de::DeserializeOwned;
 use std::{
-    net::IpAddr,
     ops::Deref,
     sync::{
         atomic::{AtomicU32, Ordering},
@@ -41,7 +41,6 @@ use std::{
     },
     time::Duration,
 };
-use tokio::net::lookup_host;
 use url::Url;
 
 /// Configuration for this library, with various federation related settings
@@ -183,30 +182,9 @@ impl<T: Clone> FederationConfig<T> {
                 return Err(Error::UrlVerificationError("Explicit port is not allowed"));
             }
 
-            // Resolve domain and see if it points to private IP
+            let allow_local = std::env::var("DANGER_FEDERATION_ALLOW_LOCAL_IP").is_ok();
-            // TODO: Use is_global() once stabilized
+            if !allow_local && validate_ip(&url).await.is_err() {
-            //       https://doc.rust-lang.org/std/net/enum.IpAddr.html#method.is_global
+                return Err(Error::DomainResolveError(domain.to_string()));
-            let invalid_ip =
-                lookup_host((domain.to_owned(), 80))
-                    .await?
-                    .any(|addr| match addr.ip() {
-                        IpAddr::V4(addr) => {
-                            addr.is_private()
-                                || addr.is_link_local()
-                                || addr.is_loopback()
-                                || addr.is_multicast()
-                        }
-                        IpAddr::V6(addr) => {
-                            addr.is_loopback()
-                        || addr.is_multicast()
-                        || ((addr.segments()[0] & 0xfe00) == 0xfc00) // is_unique_local
-                        || ((addr.segments()[0] & 0xffc0) == 0xfe80) // is_unicast_link_local
-                        }
-                    });
-            if invalid_ip {
-                return Err(Error::UrlVerificationError(
-                    "Localhost is only allowed in debug mode",
-                ));
             }
         }
 
@@ -400,6 +378,15 @@ impl<T: Clone> Data<T> {
         )
         .await
     }
+
+    /// Resolve domain of the url and throw error if it points to local/private IP.
+    pub async fn is_valid_ip(&self, url: &Url) -> Result<(), Error> {
+        if self.config.debug {
+            return Ok(());
+        }
+
+        validate_ip(url).await
+    }
 }
 
 impl<T: Clone> Deref for Data<T> {

src/error.rs

@@ -28,6 +28,9 @@ pub enum Error {
     /// url verification error
     #[error("URL failed verification: {0}")]
     UrlVerificationError(&'static str),
+    /// Resolving domain points to local IP.
+    #[error("Resolving domain {0} points to local IP address. This may indicate an attacker attempting to access internal services. If intentional, you can ignore this error by setting DANGER_FEDERATION_ALLOW_LOCAL_IP=1")]
+    DomainResolveError(String),
     /// Incoming activity has invalid digest for body
     #[error("Incoming activity has invalid digest for body")]
     ActivityBodyDigestInvalid,

src/fetch/object_id.rs

@@ -10,7 +10,7 @@ use url::Url;
 
 impl<T> FromStr for ObjectId<T>
 where
-    T: Object + Send + Debug + 'static,
+    T: Object + Send + Sync + Debug + 'static,
     for<'de2> <T as Object>::Kind: Deserialize<'de2>,
 {
     type Err = url::ParseError;
@@ -61,7 +61,7 @@ where
 
 impl<Kind> ObjectId<Kind>
 where
-    Kind: Object + Send + Debug + 'static,
+    Kind: Object + Send + Sync + Debug + 'static,
     for<'de2> <Kind as Object>::Kind: Deserialize<'de2>,
 {
     /// Construct a new objectid instance
@@ -164,6 +164,7 @@ where
         if let Err(Error::ObjectDeleted(url)) = res {
             if let Some(db_object) = db_object {
                 db_object.delete(data).await?;
+                return Ok(db_object);
             }
             return Err(Error::ObjectDeleted(url).into());
         }

src/fetch/webfinger.rs

@@ -45,7 +45,7 @@ pub async fn webfinger_resolve_actor<T: Clone, Kind>(
     data: &Data<T>,
 ) -> Result<Kind, <Kind as Object>::Error>
 where
-    Kind: Object + Actor + Send + 'static + Object<DataType = T>,
+    Kind: Object + Actor + Send + Sync + 'static + Object<DataType = T>,
     for<'de2> <Kind as Object>::Kind: serde::Deserialize<'de2>,
     <Kind as Object>::Error: From<crate::error::Error> + Send + Sync + Display,
 {
@@ -88,6 +88,7 @@ where
             }
         })
         .filter_map(|l| l.href.clone())
+        .rev()
         .collect();
 
     for l in links {
@@ -222,7 +223,7 @@ pub fn build_webfinger_response_with_type(
 }
 
 /// A webfinger response with information about a `Person` or other type of actor.
-#[derive(Serialize, Deserialize, Debug, Default)]
+#[derive(Serialize, Deserialize, Debug, Default, PartialEq)]
 pub struct Webfinger {
     /// The actor which is described here, for example `acct:LemmyDev@mastodon.social`
     pub subject: String,
@@ -237,7 +238,7 @@ pub struct Webfinger {
 }
 
 /// A single link included as part of a [Webfinger] response.
-#[derive(Serialize, Deserialize, Debug, Default)]
+#[derive(Serialize, Deserialize, Debug, Default, PartialEq)]
 pub struct WebfingerLink {
     /// Relationship of the link, such as `self` or `http://webfinger.net/rel/profile-page`
     pub rel: Option<String>,

src/http_signatures.rs

@@ -149,7 +149,7 @@ pub(crate) async fn signing_actor<'a, A, H>(
     data: &Data<<A as Object>::DataType>,
 ) -> Result<A, <A as Object>::Error>
 where
-    A: Object + Actor,
+    A: Object + Actor + Send + Sync,
     <A as Object>::Error: From<Error>,
     for<'de2> <A as Object>::Kind: Deserialize<'de2>,
     H: IntoIterator<Item = (&'a HeaderName, &'a HeaderValue)>,

src/lib.rs

@@ -23,6 +23,7 @@ pub mod http_signatures;
 pub mod protocol;
 pub(crate) mod reqwest_shim;
 pub mod traits;
+mod utils;
 
 use crate::{
     config::Data,
@@ -46,7 +47,7 @@ async fn parse_received_activity<A, ActorT, Datatype>(
 ) -> Result<(A, ActorT), <A as Activity>::Error>
 where
     A: Activity<DataType = Datatype> + DeserializeOwned + Send + 'static,
-    ActorT: Object<DataType = Datatype> + Actor + Send + 'static,
+    ActorT: Object<DataType = Datatype> + Actor + Send + Sync + 'static,
     for<'de2> <ActorT as Object>::Kind: serde::Deserialize<'de2>,
     <A as Activity>::Error: From<Error> + From<<ActorT as Object>::Error>,
     <ActorT as Object>::Error: From<Error>,

src/protocol/helpers.rs

@@ -1,13 +1,22 @@
 //! Serde deserialization functions which help to receive differently shaped data
 
-use serde::{Deserialize, Deserializer};
+use activitystreams_kinds::public;
+use itertools::Itertools;
+use serde::{de::Error, Deserialize, Deserializer};
+use serde_json::Value;
+use url::Url;
 
-/// Deserialize JSON single value or array into Vec.
+/// Deserialize JSON single value or array into `Vec<Url>`.
 ///
 /// Useful if your application can handle multiple values for a field, but another federated
 /// platform only sends a single one.
 ///
+/// Also accepts common `Public` aliases for recipient fields. Some implementations send `Public`
+/// or `as:Public` instead of the canonical `https://www.w3.org/ns/activitystreams#Public` URL
+/// in fields such as `to` and `cc`.
+///
 /// ```
+/// # use activitypub_federation::kinds::public;
 /// # use activitypub_federation::protocol::helpers::deserialize_one_or_many;
 /// # use url::Url;
 /// #[derive(serde::Deserialize)]
@@ -25,24 +34,39 @@ use serde::{Deserialize, Deserializer};
 ///      "https://lemmy.ml/u/bob"
 /// ]}"#)?;
 /// assert_eq!(multiple.to.len(), 2);
-/// Ok::<(), anyhow::Error>(())
+///
-pub fn deserialize_one_or_many<'de, T, D>(deserializer: D) -> Result<Vec<T>, D::Error>
+/// let note: Note = serde_json::from_str(r#"{"to": ["Public", "as:Public"]}"#)?;
+/// assert_eq!(note.to, vec![public()]);
+/// # Ok::<(), anyhow::Error>(())
+/// ```
+pub fn deserialize_one_or_many<'de, D>(deserializer: D) -> Result<Vec<Url>, D::Error>
 where
-    T: Deserialize<'de>,
     D: Deserializer<'de>,
 {
     #[derive(Deserialize)]
     #[serde(untagged)]
-    enum OneOrMany<T> {
+    enum OneOrMany {
-        One(T),
+        Many(Vec<Value>),
-        Many(Vec<T>),
+        One(Value),
     }
 
-    let result: OneOrMany<T> = Deserialize::deserialize(deserializer)?;
+    let result: OneOrMany = Deserialize::deserialize(deserializer)?;
-    Ok(match result {
+    let values = match result {
-        OneOrMany::Many(list) => list,
         OneOrMany::One(value) => vec![value],
-    })
+        OneOrMany::Many(values) => values,
+    };
+
+    values
+        .into_iter()
+        .map(|value| match value {
+            Value::String(value) if matches!(value.as_str(), "Public" | "as:Public") => {
+                Ok(public())
+            }
+            Value::String(value) => Url::parse(&value).map_err(D::Error::custom),
+            value => Url::deserialize(value).map_err(D::Error::custom),
+        })
+        .collect::<Result<Vec<_>, _>>()
+        .map(|values| values.into_iter().unique().collect())
 }
 
 /// Deserialize JSON single value or single element array into single value.
@@ -127,17 +151,24 @@ where
     enum MaybeArray<T> {
         Simple(T),
         Array(Vec<T>),
+        None,
     }
 
-    let result: MaybeArray<T> = Deserialize::deserialize(deserializer)?;
+    let result = Deserialize::deserialize(deserializer)?;
     Ok(match result {
         MaybeArray::Simple(value) => Some(value),
         MaybeArray::Array(value) => value.into_iter().last(),
+        MaybeArray::None => None,
     })
 }
 
 #[cfg(test)]
 mod tests {
+    use super::deserialize_one_or_many;
+    use activitystreams_kinds::public;
+    use anyhow::Result;
+    use serde::Deserialize;
+
     #[test]
     fn deserialize_one_multiple_values() {
         use crate::protocol::helpers::deserialize_one;
@@ -153,4 +184,70 @@ mod tests {
         );
         assert!(note.is_err());
     }
+
+    #[test]
+    fn deserialize_one_or_many_single_public_aliases() -> Result<()> {
+        use url::Url;
+
+        #[derive(Deserialize)]
+        struct Note {
+            #[serde(deserialize_with = "deserialize_one_or_many")]
+            to: Vec<Url>,
+        }
+
+        for alias in ["Public", "as:Public"] {
+            let note = serde_json::from_str::<Note>(&format!(r#"{{"to": "{alias}"}}"#))?;
+            assert_eq!(note.to, vec![public()]);
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn deserialize_one_or_many_array() -> Result<()> {
+        use url::Url;
+
+        #[derive(Deserialize)]
+        struct Note {
+            #[serde(deserialize_with = "deserialize_one_or_many")]
+            to: Vec<Url>,
+        }
+
+        let note = serde_json::from_str::<Note>(
+            r#"{
+                "to": [
+                    "https://example.com/c/main",
+                    "Public",
+                    "as:Public",
+                    "https://www.w3.org/ns/activitystreams#Public"
+                ]
+            }"#,
+        )?;
+
+        assert_eq!(
+            note.to,
+            vec![Url::parse("https://example.com/c/main")?, public(),]
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn deserialize_one_or_many_leaves_other_strings_unchanged() -> Result<()> {
+        use url::Url;
+
+        #[derive(Deserialize)]
+        struct Note {
+            #[serde(deserialize_with = "deserialize_one_or_many")]
+            to: Vec<Url>,
+            content: String,
+        }
+
+        let note = serde_json::from_str::<Note>(r#"{"to": "Public", "content": "Public"}"#)?;
+
+        assert_eq!(note.to, vec![public()]);
+        assert_eq!(note.content, "Public");
+
+        Ok(())
+    }
 }

src/protocol/verification.rs

@@ -63,7 +63,7 @@ pub fn verify_is_remote_object<Kind, R: Clone>(
     data: &Data<<Kind as Object>::DataType>,
 ) -> Result<(), Error>
 where
-    Kind: Object<DataType = R> + Send + 'static,
+    Kind: Object<DataType = R> + Send + Sync + 'static,
     for<'de2> <Kind as Object>::Kind: Deserialize<'de2>,
 {
     if id.is_local(data) {

src/reqwest_shim.rs

@@ -10,8 +10,8 @@ use std::{
     task::{Context, Poll},
 };
 
-/// 200KB
+/// 1 MB
-const MAX_BODY_SIZE: usize = 204800;
+const MAX_BODY_SIZE: usize = 1024 * 1024;
 
 pin_project! {
     pub struct BytesFuture {
@@ -66,7 +66,7 @@ impl Future for TextFuture {
 /// Reqwest doesn't limit the response body size by default nor does it offer an option to configure one.
 /// Since we have to fetch data from untrusted sources, not restricting the maximum size is a DoS hazard for us.
 ///
-/// This shim reimplements the `bytes`, `json`, and `text` functions and restricts the bodies to 100KB.
+/// This shim reimplements the `bytes`, `json`, and `text` functions and restricts the bodies length.
 ///
 /// TODO: Remove this shim as soon as reqwest gets support for size-limited bodies.
 pub trait ResponseExt {

src/traits/either.rs

@@ -18,8 +18,8 @@ pub enum UntaggedEither<L, R> {
 #[async_trait]
 impl<T, R, E, D> Object for Either<T, R>
 where
-    T: Object + Object<Error = E, DataType = D> + Send,
+    T: Object + Object<Error = E, DataType = D> + Send + Sync,
-    R: Object + Object<Error = E, DataType = D> + Send,
+    R: Object + Object<Error = E, DataType = D> + Send + Sync,
     <T as Object>::Kind: Send + Sync,
     <R as Object>::Kind: Send + Sync,
     D: Sync + Send + Clone,
@@ -30,7 +30,7 @@ where
     type Error = E;
 
     /// `id` field of the object
-    fn id(&self) -> &Url {
+    fn id(&self) -> Url {
         match self {
             Either::Left(l) => l.id(),
             Either::Right(r) => r.id(),
@@ -59,7 +59,7 @@ where
         Ok(None)
     }
 
-    async fn delete(self, data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+    async fn delete(&self, data: &Data<Self::DataType>) -> Result<(), Self::Error> {
         match self {
             Either::Left(l) => l.delete(data).await,
             Either::Right(r) => r.delete(data).await,
@@ -103,8 +103,8 @@ where
 #[async_trait]
 impl<T, R, E, D> Actor for Either<T, R>
 where
-    T: Actor + Object + Object<Error = E, DataType = D> + Send + 'static,
+    T: Actor + Object + Object<Error = E, DataType = D> + Send + Sync + 'static,
-    R: Actor + Object + Object<Error = E, DataType = D> + Send + 'static,
+    R: Actor + Object + Object<Error = E, DataType = D> + Send + Sync + 'static,
     <T as Object>::Kind: Send + Sync,
     <R as Object>::Kind: Send + Sync,
     D: Sync + Send + Clone,

src/traits/mod.rs

@@ -53,7 +53,7 @@ pub mod tests;
 ///     type Kind = Note;
 ///     type Error = anyhow::Error;
 ///
-/// fn id(&self) -> &Url { self.ap_id.inner() }
+/// fn id(&self) -> Url { self.ap_id.inner().clone() }
 ///
 /// async fn read_from_id(object_id: Url, data: &Data<Self::DataType>) -> Result<Option<Self>, Self::Error> {
 ///         // Attempt to read object from local database. Return Ok(None) if not found.
@@ -110,7 +110,7 @@ pub trait Object: Sized + Debug {
     type Error;
 
     /// `id` field of the object
-    fn id(&self) -> &Url;
+    fn id(&self) -> Url;
 
     /// Returns the last time this object was updated.
     ///
@@ -136,7 +136,7 @@ pub trait Object: Sized + Debug {
     /// Mark remote object as deleted in local database.
     ///
     /// Called when a `Delete` activity is received, or if fetch returns a `Tombstone` object.
-    async fn delete(self, _data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+    async fn delete(&self, _data: &Data<Self::DataType>) -> Result<(), Self::Error> {
         Ok(())
     }
 
@@ -194,8 +194,8 @@ pub trait Object: Sized + Debug {
             redirect_remote_object,
         };
         let id = self.id();
-        let res = if !data.config.is_local_url(id) {
+        let res = if !data.config.is_local_url(&id) {
-            redirect_remote_object(id)
+            redirect_remote_object(&id)
         } else if !self.is_deleted() {
             let json = self.into_json(data).await?;
             create_http_response(json, federation_context)?

src/traits/tests.rs

@@ -73,8 +73,8 @@ impl Object for DbUser {
     type Kind = Person;
     type Error = Error;
 
-    fn id(&self) -> &Url {
+    fn id(&self) -> Url {
-        &self.federation_id
+        self.federation_id.clone()
     }
 
     async fn read_from_id(
@@ -179,7 +179,7 @@ impl Object for DbPost {
     type Kind = Note;
     type Error = Error;
 
-    fn id(&self) -> &Url {
+    fn id(&self) -> Url {
         todo!()
     }
 

src/utils.rs

@@ -0,0 +1,78 @@
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
+
+use crate::error::Error;
+use tokio::net::lookup_host;
+use url::{Host, Url};
+
+// TODO: Use is_global() once stabilized
+//       https://doc.rust-lang.org/std/net/enum.IpAddr.html#method.is_global
+pub(crate) async fn validate_ip(url: &Url) -> Result<(), Error> {
+    let mut ip = vec![];
+    let host = url
+        .host()
+        .ok_or(Error::UrlVerificationError("Url must have a domain"))?;
+    match host {
+        Host::Domain(domain) => ip.extend(
+            lookup_host((domain.to_owned(), 80))
+                .await?
+                .map(|s| s.ip().to_canonical()),
+        ),
+        Host::Ipv4(ipv4) => ip.push(ipv4.into()),
+        Host::Ipv6(ipv6) => ip.push(ipv6.into()),
+    };
+
+    let invalid_ip = ip.into_iter().any(|addr| match addr {
+        IpAddr::V4(addr) => v4_is_invalid(addr),
+        IpAddr::V6(addr) => v6_is_invalid(addr),
+    });
+    if invalid_ip {
+        return Err(Error::DomainResolveError(host.to_string()));
+    }
+    Ok(())
+}
+
+fn v4_is_invalid(v4: Ipv4Addr) -> bool {
+    v4.is_private()
+        || v4.is_loopback()
+        || v4.is_link_local()
+        || v4.is_multicast()
+        || v4.is_documentation()
+        || v4.is_unspecified()
+        || v4.is_broadcast()
+}
+
+fn v6_is_invalid(v6: Ipv6Addr) -> bool {
+    v6.is_loopback()
+        || v6.is_multicast()
+        || v6.is_unique_local()
+        || v6.is_unicast_link_local()
+        || v6.is_unspecified()
+        || v6_is_documentation(v6)
+        || v6.to_ipv4_mapped().is_some_and(v4_is_invalid)
+}
+
+fn v6_is_documentation(v6: std::net::Ipv6Addr) -> bool {
+    matches!(
+        v6.segments(),
+        [0x2001, 0xdb8, ..] | [0x3fff, 0..=0x0fff, ..]
+    )
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod test {
+    use super::*;
+
+    #[tokio::test]
+    async fn test_is_valid_ip() -> Result<(), Error> {
+        assert!(validate_ip(&Url::parse("http://example.com")?)
+            .await
+            .is_ok());
+        assert!(validate_ip(&Url::parse("http://172.66.147.243")?)
+            .await
+            .is_ok());
+        assert!(validate_ip(&Url::parse("http://localhost")?).await.is_err());
+        assert!(validate_ip(&Url::parse("http://127.0.0.1")?).await.is_err());
+        Ok(())
+    }
+}