From d14e98b62b866e75c84baa19e36bf2d0bb7d49e7 Mon Sep 17 00:00:00 2001
From: Rob Ede <robjtede@icloud.com>
Date: Mon, 25 Dec 2023 02:27:51 +0000
Subject: [PATCH] prevent hang when compressing Sized(0) bodies

fixes #3229
---
 actix-http/CHANGES.md              |  4 ++++
 actix-http/src/encoding/encoder.rs | 17 ++++++++++++++---
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/actix-http/CHANGES.md b/actix-http/CHANGES.md
index 3068b4ce2..053c4e512 100644
--- a/actix-http/CHANGES.md
+++ b/actix-http/CHANGES.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+## Fixed
+
+- Prevent hang when returning zero-sized response bodies through compression layer.
+
 ## 3.5.0
 
 ### Changed
diff --git a/actix-http/src/encoding/encoder.rs b/actix-http/src/encoding/encoder.rs
index e084aa564..180927ac6 100644
--- a/actix-http/src/encoding/encoder.rs
+++ b/actix-http/src/encoding/encoder.rs
@@ -50,10 +50,21 @@ impl<B: MessageBody> Encoder<B> {
         }
     }
 
+    fn empty() -> Self {
+        Encoder {
+            body: EncoderBody::Full { body: Bytes::new() },
+            encoder: None,
+            fut: None,
+            eof: true,
+        }
+    }
+
     pub fn response(encoding: ContentEncoding, head: &mut ResponseHead, body: B) -> Self {
-        // no need to compress an empty body
-        if matches!(body.size(), BodySize::None | BodySize::Sized(0)) {
-            return Self::none();
+        // no need to compress empty bodies
+        match body.size() {
+            BodySize::None => return Self::none(),
+            BodySize::Sized(0) => return Self::empty(),
+            _ => {}
         }
 
         let should_encode = !(head.headers().contains_key(&CONTENT_ENCODING)