fix(http1): discard content-length header when received before transfer-encoding (#4124)

While hyper currently recognizes the correct message payload semantics when both
content-length and transfer-encoding headers are sent, there are cases where it
doesn't always strip the canceled content-length header.

This fix now correctly removes the header if it was seen before transfer-encoding.

It also now sets the connection to close at the end of the message, as
recommended in the new RFC 9112.

(To be clear, the semantics have always been correct. This reduces the possibility
of forwarding confusing headers to a remote that doesn't know how to act correctly.)

Closes #4123

Author: seanmonstar

src/proto/h1/role.rs

@@ -234,6 +234,7 @@ impl Http1Transaction for Server {
         let mut decoder = DecodedLength::ZERO;
         let mut expect_continue = false;
         let mut con_len = None;
+        let mut is_cl = false;
         let mut is_te = false;
         let mut is_te_chunked = false;
         let mut wants_upgrade = subject.0 == Method::CONNECT;
@@ -272,6 +273,9 @@ impl Http1Transaction for Server {
                         return Err(Parse::transfer_encoding_unexpected());
                     }
                     is_te = true;
+                    if is_cl && con_len.take().is_some() {
+                        headers.remove(header::CONTENT_LENGTH);
+                    }
                     if headers::is_chunked_(&value) {
                         is_te_chunked = true;
                         decoder = DecodedLength::CHUNKED;
@@ -280,6 +284,7 @@ impl Http1Transaction for Server {
                     }
                 }
                 header::CONTENT_LENGTH => {
+                    is_cl = true;
                     if is_te {
                         continue;
                     }
@@ -340,6 +345,10 @@ impl Http1Transaction for Server {
             return Err(Parse::transfer_encoding_invalid());
         }
 
+        if is_te && is_cl {
+            keep_alive = false;
+        }
+
         let mut extensions = http::Extensions::default();
 
         if let Some(header_case_map) = header_case_map {
@@ -2048,45 +2057,55 @@ mod tests {
         );
 
         // transfer-encoding and content-length = chunked
-        assert_eq!(
-            parse(
-                "\
-                 POST / HTTP/1.1\r\n\
-                 content-length: 10\r\n\
-                 transfer-encoding: chunked\r\n\
-                 \r\n\
-                 "
-            )
-            .decode,
-            DecodedLength::CHUNKED
+        let msg = parse(
+            "\
+             POST / HTTP/1.1\r\n\
+             content-length: 10\r\n\
+             transfer-encoding: chunked\r\n\
+             \r\n\
+             ",
         );
+        assert_eq!(msg.decode, DecodedLength::CHUNKED);
+        assert!(!msg.head.headers.contains_key(header::CONTENT_LENGTH));
+        assert!(!msg.keep_alive);
 
-        assert_eq!(
-            parse(
-                "\
-                 POST / HTTP/1.1\r\n\
-                 transfer-encoding: chunked\r\n\
-                 content-length: 10\r\n\
-                 \r\n\
-                 "
-            )
-            .decode,
-            DecodedLength::CHUNKED
+        let msg = parse(
+            "\
+             POST / HTTP/1.1\r\n\
+             transfer-encoding: chunked\r\n\
+             content-length: 10\r\n\
+             \r\n\
+             ",
         );
+        assert_eq!(msg.decode, DecodedLength::CHUNKED);
+        assert!(!msg.head.headers.contains_key(header::CONTENT_LENGTH));
+        assert!(!msg.keep_alive);
 
-        assert_eq!(
-            parse(
-                "\
-                 POST / HTTP/1.1\r\n\
-                 transfer-encoding: gzip\r\n\
-                 content-length: 10\r\n\
-                 transfer-encoding: chunked\r\n\
-                 \r\n\
-                 "
-            )
-            .decode,
-            DecodedLength::CHUNKED
+        let msg = parse(
+            "\
+             POST / HTTP/1.1\r\n\
+             transfer-encoding: gzip\r\n\
+             content-length: 10\r\n\
+             transfer-encoding: chunked\r\n\
+             \r\n\
+             ",
+        );
+        assert_eq!(msg.decode, DecodedLength::CHUNKED);
+        assert!(!msg.head.headers.contains_key(header::CONTENT_LENGTH));
+        assert!(!msg.keep_alive);
+
+        let msg = parse(
+            "\
+             POST / HTTP/1.1\r\n\
+             connection: keep-alive\r\n\
+             content-length: 10\r\n\
+             transfer-encoding: chunked\r\n\
+             \r\n\
+             ",
         );
+        assert_eq!(msg.decode, DecodedLength::CHUNKED);
+        assert!(!msg.head.headers.contains_key(header::CONTENT_LENGTH));
+        assert!(!msg.keep_alive);
 
         // multiple content-lengths of same value are fine
         assert_eq!(