fix(http1): protect against overflow in chunked decoder

The HTTP/1 chunked decoder, when decoding the size of a chunk, could
overflow the size if the hex digits were too large. This fixes it by
adding an overflow check in the decoder.

See GHSA-5h46-h7hh-c6x9

src/proto/h1/decode.rs

@@ -208,19 +208,32 @@ impl ChunkedState {
         size: &mut u64,
     ) -> Poll<Result<ChunkedState, io::Error>> {
         trace!("Read chunk hex size");
+
+        macro_rules! or_overflow {
+            ($e:expr) => (
+                match $e {
+                    Some(val) => val,
+                    None => return Poll::Ready(Err(io::Error::new(
+                        io::ErrorKind::InvalidData,
+                        "invalid chunk size: overflow",
+                    ))),
+                }
+            )
+        }
+
         let radix = 16;
         match byte!(rdr, cx) {
             b @ b'0'..=b'9' => {
-                *size *= radix;
+                *size = or_overflow!(size.checked_mul(radix));
-                *size += (b - b'0') as u64;
+                *size = or_overflow!(size.checked_add((b - b'0') as u64));
             }
             b @ b'a'..=b'f' => {
-                *size *= radix;
+                *size = or_overflow!(size.checked_mul(radix));
-                *size += (b + 10 - b'a') as u64;
+                *size = or_overflow!(size.checked_add((b + 10 - b'a') as u64));
             }
             b @ b'A'..=b'F' => {
-                *size *= radix;
+                *size = or_overflow!(size.checked_mul(radix));
-                *size += (b + 10 - b'A') as u64;
+                *size = or_overflow!(size.checked_add((b + 10 - b'A') as u64));
             }
             b'\t' | b' ' => return Poll::Ready(Ok(ChunkedState::SizeLws)),
             b';' => return Poll::Ready(Ok(ChunkedState::Extension)),
@@ -449,7 +462,7 @@ mod tests {
 
     #[tokio::test]
     async fn test_read_chunk_size() {
-        use std::io::ErrorKind::{InvalidInput, UnexpectedEof};
+        use std::io::ErrorKind::{InvalidData, InvalidInput, UnexpectedEof};
 
         async fn read(s: &str) -> u64 {
             let mut state = ChunkedState::Size;
@@ -524,6 +537,8 @@ mod tests {
         read_err("1 invalid extension\r\n", InvalidInput).await;
         read_err("1 A\r\n", InvalidInput).await;
         read_err("1;no CRLF", UnexpectedEof).await;
+        // Overflow
+        read_err("f0000000000000003\r\n", InvalidData).await;
     }
 
     #[tokio::test]

tests/server.rs

@@ -431,6 +431,35 @@ fn post_with_chunked_body() {
     assert_eq!(server.body(), b"qwert");
 }
 
+#[test]
+fn post_with_chunked_overflow() {
+    let server = serve();
+    let mut req = connect(server.addr());
+    req.write_all(
+        b"\
+        POST / HTTP/1.1\r\n\
+        Host: example.domain\r\n\
+        Transfer-Encoding: chunked\r\n\
+        \r\n\
+        f0000000000000003\r\n\
+        abc\r\n\
+        0\r\n\
+        \r\n\
+        GET /sneaky HTTP/1.1\r\n\
+        \r\n\
+    ",
+    )
+    .unwrap();
+    req.read(&mut [0; 256]).unwrap();
+
+    let err = server.body_err().to_string();
+    assert!(
+        err.contains("overflow"),
+        "error should be overflow: {:?}",
+        err
+    );
+}
+
 #[test]
 fn post_with_incomplete_body() {
     let _ = pretty_env_logger::try_init();