proxy_server: support chunked request bodies (#21)

Teach the incoming HTTP request parser to handle Transfer-Encoding:
chunked instead of only Content-Length-framed bodies.

Also reply with 100 Continue when a client sends Expect:
100-continue before waiting for the request body.

This keeps request framing correct for POST/PUT-style clients and
adds focused tests for chunked decoding and 100-continue handling.

Co-authored-by: freeinternet865 <free@internet865.com>

src/proxy_server.rs

@@ -950,7 +950,6 @@ where
         None => return Ok(false),
     };
 
-    // Read body if content-length is set.
     let body = read_body(stream, &leftover, &headers).await?;
 
     let default_port = if scheme == "https" { 443 } else { 80 };
@@ -1006,36 +1005,178 @@ where
     }
 }
 
+fn header_value<'a>(headers: &'a [(String, String)], name: &str) -> Option<&'a str> {
+    headers
+        .iter()
+        .find(|(k, _)| k.eq_ignore_ascii_case(name))
+        .map(|(_, v)| v.as_str())
+}
+
+fn expects_100_continue(headers: &[(String, String)]) -> bool {
+    header_value(headers, "expect")
+        .map(|v| {
+            v.split(',')
+                .any(|part| part.trim().eq_ignore_ascii_case("100-continue"))
+        })
+        .unwrap_or(false)
+}
+
+fn invalid_body(msg: impl Into<String>) -> std::io::Error {
+    std::io::Error::new(std::io::ErrorKind::InvalidData, msg.into())
+}
+
 async fn read_body<S>(
     stream: &mut S,
     leftover: &[u8],
     headers: &[(String, String)],
 ) -> std::io::Result<Vec<u8>>
 where
-    S: tokio::io::AsyncRead + Unpin,
+    S: tokio::io::AsyncRead + tokio::io::AsyncWrite + Unpin,
 {
-    let cl: Option<usize> = headers
+    let transfer_encoding = header_value(headers, "transfer-encoding");
-        .iter()
+    let is_chunked = transfer_encoding
-        .find(|(k, _)| k.eq_ignore_ascii_case("content-length"))
+        .map(|v| {
-        .and_then(|(_, v)| v.parse().ok());
+            v.split(',')
+                .any(|part| part.trim().eq_ignore_ascii_case("chunked"))
+        })
+        .unwrap_or(false);
 
-    let Some(cl) = cl else {
+    let content_length = match header_value(headers, "content-length") {
+        Some(v) => Some(
+            v.parse::<usize>()
+                .map_err(|_| invalid_body(format!("invalid Content-Length: {}", v)))?,
+        ),
+        None => None,
+    };
+
+    if transfer_encoding.is_some() && !is_chunked {
+        return Err(invalid_body(format!(
+            "unsupported Transfer-Encoding: {}",
+            transfer_encoding.unwrap_or_default()
+        )));
+    }
+
+    if is_chunked && content_length.is_some() {
+        return Err(invalid_body(
+            "both Transfer-Encoding: chunked and Content-Length are present",
+        ));
+    }
+
+    if expects_100_continue(headers) && (is_chunked || content_length.is_some()) {
+        stream.write_all(b"HTTP/1.1 100 Continue\r\n\r\n").await?;
+        stream.flush().await?;
+    }
+
+    if is_chunked {
+        return read_chunked_request_body(stream, leftover.to_vec()).await;
+    }
+
+    let Some(content_length) = content_length else {
         return Ok(Vec::new());
     };
-    let mut body = Vec::with_capacity(cl);
+
-    body.extend_from_slice(&leftover[..leftover.len().min(cl)]);
+    let mut body = Vec::with_capacity(content_length);
+    body.extend_from_slice(&leftover[..leftover.len().min(content_length)]);
     let mut tmp = [0u8; 8192];
-    while body.len() < cl {
+    while body.len() < content_length {
         let n = stream.read(&mut tmp).await?;
         if n == 0 {
-            break;
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::UnexpectedEof,
+                "EOF mid-body",
+            ));
         }
-        let need = cl - body.len();
+        let need = content_length - body.len();
         body.extend_from_slice(&tmp[..n.min(need)]);
     }
     Ok(body)
 }
 
+async fn read_chunked_request_body<S>(stream: &mut S, mut buf: Vec<u8>) -> std::io::Result<Vec<u8>>
+where
+    S: tokio::io::AsyncRead + Unpin,
+{
+    let mut out = Vec::new();
+    let mut tmp = [0u8; 8192];
+
+    loop {
+        let line = read_crlf_line(stream, &mut buf, &mut tmp).await?;
+        if line.is_empty() {
+            continue;
+        }
+
+        let line_str = std::str::from_utf8(&line)
+            .map_err(|_| invalid_body("non-utf8 chunk size line"))?
+            .trim();
+        let size_hex = line_str.split(';').next().unwrap_or("");
+        let size = usize::from_str_radix(size_hex, 16)
+            .map_err(|_| invalid_body(format!("bad chunk size '{}'", line_str)))?;
+
+        if size == 0 {
+            loop {
+                let trailer = read_crlf_line(stream, &mut buf, &mut tmp).await?;
+                if trailer.is_empty() {
+                    return Ok(out);
+                }
+            }
+        }
+
+        fill_buffer(stream, &mut buf, &mut tmp, size + 2).await?;
+        if &buf[size..size + 2] != b"\r\n" {
+            return Err(invalid_body("chunk missing trailing CRLF"));
+        }
+        out.extend_from_slice(&buf[..size]);
+        buf.drain(..size + 2);
+    }
+}
+
+async fn read_crlf_line<S>(
+    stream: &mut S,
+    buf: &mut Vec<u8>,
+    tmp: &mut [u8],
+) -> std::io::Result<Vec<u8>>
+where
+    S: tokio::io::AsyncRead + Unpin,
+{
+    loop {
+        if let Some(idx) = buf.windows(2).position(|w| w == b"\r\n") {
+            let line = buf[..idx].to_vec();
+            buf.drain(..idx + 2);
+            return Ok(line);
+        }
+        let n = stream.read(tmp).await?;
+        if n == 0 {
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::UnexpectedEof,
+                "EOF in chunked body",
+            ));
+        }
+        buf.extend_from_slice(&tmp[..n]);
+    }
+}
+
+async fn fill_buffer<S>(
+    stream: &mut S,
+    buf: &mut Vec<u8>,
+    tmp: &mut [u8],
+    want: usize,
+) -> std::io::Result<()>
+where
+    S: tokio::io::AsyncRead + Unpin,
+{
+    while buf.len() < want {
+        let n = stream.read(tmp).await?;
+        if n == 0 {
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::UnexpectedEof,
+                "EOF in chunked body",
+            ));
+        }
+        buf.extend_from_slice(&tmp[..n]);
+    }
+    Ok(())
+}
+
 // ---------- Plain HTTP proxy ----------
 
 async fn do_plain_http(
@@ -1068,3 +1209,69 @@ async fn do_plain_http(
     sock.flush().await?;
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use tokio::io::{duplex, AsyncReadExt, AsyncWriteExt};
+
+    fn headers(pairs: &[(&str, &str)]) -> Vec<(String, String)> {
+        pairs
+            .iter()
+            .map(|(k, v)| ((*k).to_string(), (*v).to_string()))
+            .collect()
+    }
+
+    #[tokio::test(flavor = "current_thread")]
+    async fn read_body_decodes_chunked_request() {
+        let (mut client, mut server) = duplex(1024);
+        let writer = tokio::spawn(async move {
+            client
+                .write_all(b"llo\r\n6\r\n world\r\n0\r\nFoo: bar\r\n\r\n")
+                .await
+                .unwrap();
+        });
+
+        let body = read_body(
+            &mut server,
+            b"5\r\nhe",
+            &headers(&[("Transfer-Encoding", "chunked")]),
+        )
+        .await
+        .unwrap();
+
+        writer.await.unwrap();
+        assert_eq!(body, b"hello world");
+    }
+
+    #[tokio::test(flavor = "current_thread")]
+    async fn read_body_sends_100_continue_before_waiting_for_body() {
+        let (mut client, mut server) = duplex(1024);
+        let client_task = tokio::spawn(async move {
+            let mut got = Vec::new();
+            let mut tmp = [0u8; 64];
+            loop {
+                let n = client.read(&mut tmp).await.unwrap();
+                assert!(n > 0, "proxy closed before sending 100 Continue");
+                got.extend_from_slice(&tmp[..n]);
+                if got.windows(4).any(|w| w == b"\r\n\r\n") {
+                    break;
+                }
+            }
+            assert_eq!(got, b"HTTP/1.1 100 Continue\r\n\r\n");
+            client.write_all(b"hello").await.unwrap();
+        });
+
+        let body = read_body(
+            &mut server,
+            &[],
+            &headers(&[("Content-Length", "5"), ("Expect", "100-continue")]),
+        )
+        .await
+        .unwrap();
+
+        client_task.await.unwrap();
+        assert_eq!(body, b"hello");
+    }
+
+}