fix

src/config.rs

@@ -25,6 +25,7 @@ use async_trait::async_trait;
 use bytes::Bytes;
 use derive_builder::Builder;
 use dyn_clone::{clone_trait_object, DynClone};
+use itertools::Itertools;
 use moka::future::Cache;
 use regex::Regex;
 use reqwest::{redirect::Policy, Client, Request};
@@ -186,10 +187,10 @@ impl<T: Clone> FederationConfig<T> {
             // Resolve domain and see if it points to private IP
             // TODO: Use is_global() once stabilized
             //       https://doc.rust-lang.org/std/net/enum.IpAddr.html#method.is_global
-            let invalid_ip =
+            let mut ips = lookup_host((domain.to_owned(), 80)).await?;
-                lookup_host((domain.to_owned(), 80))
+            let allow_local = std::env::var("DANGER_FEDERATION_ALLOW_LOCAL_IP").is_ok();
-                    .await?
+            let invalid_ip = !allow_local
-                    .any(|addr| match addr.ip() {
+                && ips.any(|addr| match addr.ip() {
                     IpAddr::V4(addr) => {
                         addr.is_private()
                             || addr.is_link_local()
@@ -204,9 +205,8 @@ impl<T: Clone> FederationConfig<T> {
                     }
                 });
             if invalid_ip {
-                return Err(Error::UrlVerificationError(
+                let ip_addrs = ips.join(", ");
-                    "Localhost is only allowed in debug mode",
+                return Err(Error::DomainResolveError(domain.to_string(), ip_addrs));
-                ));
             }
         }
 

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 {1}. 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, String),
     /// Incoming activity has invalid digest for body
     #[error("Incoming activity has invalid digest for body")]
     ActivityBodyDigestInvalid,