fix parsing ambiguities for HTTP/1.0 requests (#2794)

* fix HRS vuln when first CL header is 0

* ignore TE headers in http/1.0 reqs

* update changelog

* disallow HTTP/1.0 requests without a CL header

* fix test

* broken fix for http1.0 post requests

actix-http/CHANGES.md

@@ -1,6 +1,10 @@
 # Changes
 
 ## Unreleased - 2022-xx-xx
+### Fixed
+- Fix parsing ambiguity in Transfer-Encoding and Content-Length headers for HTTP/1.0 requests. [#2794]
+
+[#2794]: https://github.com/actix/actix-web/pull/2794
 
 
 ## 3.2.0 - 2022-06-30

actix-http/src/h1/decoder.rs

@@ -46,6 +46,23 @@ pub(crate) enum PayloadLength {
     None,
 }
 
+impl PayloadLength {
+    /// Returns true if variant is `None`.
+    fn is_none(&self) -> bool {
+        matches!(self, Self::None)
+    }
+
+    /// Returns true if variant is represents zero-length (not none) payload.
+    fn is_zero(&self) -> bool {
+        matches!(
+            self,
+            PayloadLength::Payload(PayloadType::Payload(PayloadDecoder {
+                kind: Kind::Length(0)
+            }))
+        )
+    }
+}
+
 pub(crate) trait MessageType: Sized {
     fn set_connection_type(&mut self, conn_type: Option<ConnectionType>);
 
@@ -59,6 +76,7 @@ pub(crate) trait MessageType: Sized {
         &mut self,
         slice: &Bytes,
         raw_headers: &[HeaderIndex],
+        version: Version,
     ) -> Result<PayloadLength, ParseError> {
         let mut ka = None;
         let mut has_upgrade_websocket = false;
@@ -87,21 +105,23 @@ pub(crate) trait MessageType: Sized {
                         return Err(ParseError::Header);
                     }
 
-                    header::CONTENT_LENGTH => match value.to_str() {
-                        Ok(s) if s.trim().starts_with('+') => {
-                            debug!("illegal Content-Length: {:?}", s);
+                    header::CONTENT_LENGTH => match value.to_str().map(str::trim) {
+                        Ok(val) if val.starts_with('+') => {
+                            debug!("illegal Content-Length: {:?}", val);
                             return Err(ParseError::Header);
                         }
-                        Ok(s) => {
-                            if let Ok(len) = s.parse::<u64>() {
-                                if len != 0 {
+
+                        Ok(val) => {
+                            if let Ok(len) = val.parse::<u64>() {
+                                // accept 0 lengths here and remove them in `decode` after all
+                                // headers have been processed to prevent request smuggling issues
                                 content_length = Some(len);
-                                }
                             } else {
-                                debug!("illegal Content-Length: {:?}", s);
+                                debug!("illegal Content-Length: {:?}", val);
                                 return Err(ParseError::Header);
                             }
                         }
+
                         Err(_) => {
                             debug!("illegal Content-Length: {:?}", value);
                             return Err(ParseError::Header);
@@ -114,22 +134,23 @@ pub(crate) trait MessageType: Sized {
                         return Err(ParseError::Header);
                     }
 
-                    header::TRANSFER_ENCODING => {
+                    header::TRANSFER_ENCODING if version == Version::HTTP_11 => {
                         seen_te = true;
 
-                        if let Ok(s) = value.to_str().map(str::trim) {
-                            if s.eq_ignore_ascii_case("chunked") {
+                        if let Ok(val) = value.to_str().map(str::trim) {
+                            if val.eq_ignore_ascii_case("chunked") {
                                 chunked = true;
-                            } else if s.eq_ignore_ascii_case("identity") {
+                            } else if val.eq_ignore_ascii_case("identity") {
                                 // allow silently since multiple TE headers are already checked
                             } else {
-                                debug!("illegal Transfer-Encoding: {:?}", s);
+                                debug!("illegal Transfer-Encoding: {:?}", val);
                                 return Err(ParseError::Header);
                             }
                         } else {
                             return Err(ParseError::Header);
                         }
                     }
+
                     // connection keep-alive state
                     header::CONNECTION => {
                         ka = if let Ok(conn) = value.to_str().map(str::trim) {
@@ -146,6 +167,7 @@ pub(crate) trait MessageType: Sized {
                             None
                         };
                     }
+
                     header::UPGRADE => {
                         if let Ok(val) = value.to_str().map(str::trim) {
                             if val.eq_ignore_ascii_case("websocket") {
@@ -153,19 +175,23 @@ pub(crate) trait MessageType: Sized {
                             }
                         }
                     }
+
                     header::EXPECT => {
                         let bytes = value.as_bytes();
                         if bytes.len() >= 4 && &bytes[0..4] == b"100-" {
                             expect = true;
                         }
                     }
+
                     _ => {}
                 }
 
                 headers.append(name, value);
             }
         }
+
         self.set_connection_type(ka);
+
         if expect {
             self.set_expect()
         }
@@ -249,7 +275,22 @@ impl MessageType for Request {
         let mut msg = Request::new();
 
         // convert headers
-        let length = msg.set_headers(&src.split_to(len).freeze(), &headers[..h_len])?;
+        let mut length =
+            msg.set_headers(&src.split_to(len).freeze(), &headers[..h_len], ver)?;
+
+        // disallow HTTP/1.0 POST requests that do not contain a Content-Length headers
+        // see https://datatracker.ietf.org/doc/html/rfc1945#section-7.2.2
+        if ver == Version::HTTP_10 && method == Method::POST && length.is_none() {
+            debug!("no Content-Length specified for HTTP/1.0 POST request");
+            return Err(ParseError::Header);
+        }
+
+        // Remove CL value if 0 now that all headers and HTTP/1.0 special cases are processed.
+        // Protects against some request smuggling attacks.
+        // See https://github.com/actix/actix-web/issues/2767.
+        if length.is_zero() {
+            length = PayloadLength::None;
+        }
 
         // payload decoder
         let decoder = match length {
@@ -337,7 +378,15 @@ impl MessageType for ResponseHead {
         msg.version = ver;
 
         // convert headers
-        let length = msg.set_headers(&src.split_to(len).freeze(), &headers[..h_len])?;
+        let mut length =
+            msg.set_headers(&src.split_to(len).freeze(), &headers[..h_len], ver)?;
+
+        // Remove CL value if 0 now that all headers and HTTP/1.0 special cases are processed.
+        // Protects against some request smuggling attacks.
+        // See https://github.com/actix/actix-web/issues/2767.
+        if length.is_zero() {
+            length = PayloadLength::None;
+        }
 
         // message payload
         let decoder = if let PayloadLength::Payload(pl) = length {
@@ -606,14 +655,40 @@ mod tests {
     }
 
     #[test]
-    fn test_parse_post() {
-        let mut buf = BytesMut::from("POST /test2 HTTP/1.0\r\n\r\n");
+    fn parse_h10_post() {
+        let mut buf = BytesMut::from(
+            "POST /test1 HTTP/1.0\r\n\
+            Content-Length: 3\r\n\
+            \r\n\
+            abc",
+        );
+
+        let mut reader = MessageDecoder::<Request>::default();
+        let (req, _) = reader.decode(&mut buf).unwrap().unwrap();
+        assert_eq!(req.version(), Version::HTTP_10);
+        assert_eq!(*req.method(), Method::POST);
+        assert_eq!(req.path(), "/test1");
+
+        let mut buf = BytesMut::from(
+            "POST /test2 HTTP/1.0\r\n\
+            Content-Length: 0\r\n\
+            \r\n",
+        );
 
         let mut reader = MessageDecoder::<Request>::default();
         let (req, _) = reader.decode(&mut buf).unwrap().unwrap();
         assert_eq!(req.version(), Version::HTTP_10);
         assert_eq!(*req.method(), Method::POST);
         assert_eq!(req.path(), "/test2");
+
+        let mut buf = BytesMut::from(
+            "POST /test3 HTTP/1.0\r\n\
+            \r\n",
+        );
+
+        let mut reader = MessageDecoder::<Request>::default();
+        let err = reader.decode(&mut buf).unwrap_err();
+        assert!(err.to_string().contains("Header"))
     }
 
     #[test]
@@ -981,6 +1056,17 @@ mod tests {
         );
 
         expect_parse_err!(&mut buf);
+
+        let mut buf = BytesMut::from(
+            "GET / HTTP/1.1\r\n\
+            Host: example.com\r\n\
+            Content-Length: 0\r\n\
+            Content-Length: 2\r\n\
+            \r\n\
+            ab",
+        );
+
+        expect_parse_err!(&mut buf);
     }
 
     #[test]
@@ -996,6 +1082,40 @@ mod tests {
         expect_parse_err!(&mut buf);
     }
 
+    #[test]
+    fn hrs_te_http10() {
+        // in HTTP/1.0 transfer encoding is ignored and must therefore contain a CL header
+
+        let mut buf = BytesMut::from(
+            "POST / HTTP/1.0\r\n\
+            Host: example.com\r\n\
+            Transfer-Encoding: chunked\r\n\
+            \r\n\
+            3\r\n\
+            aaa\r\n\
+            0\r\n\
+            ",
+        );
+
+        expect_parse_err!(&mut buf);
+    }
+
+    #[test]
+    fn hrs_cl_and_te_http10() {
+        // in HTTP/1.0 transfer encoding is simply ignored so it's fine to have both
+
+        let mut buf = BytesMut::from(
+            "GET / HTTP/1.0\r\n\
+            Host: example.com\r\n\
+            Content-Length: 3\r\n\
+            Transfer-Encoding: chunked\r\n\
+            \r\n\
+            000",
+        );
+
+        parse_ready!(&mut buf);
+    }
+
     #[test]
     fn hrs_unknown_transfer_encoding() {
         let mut buf = BytesMut::from(