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feat(http1): add max_header_size limit for server and client #4183

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59e1fbe
feat(http1): add max_header_size limit for server and client
Aditya-9-6 Sep 6, 2026
61e64dc
style: format integration tests with rustfmt
Aditya-9-6 Sep 9, 2026
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16 changes: 16 additions & 0 deletions src/client/conn/http1.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -131,6 +131,7 @@ pub struct Builder {
h1_title_case_headers: bool,
h1_preserve_header_case: bool,
h1_max_headers: Option<usize>,
h1_max_header_size: Option<usize>,
#[cfg(feature = "ffi")]
h1_preserve_header_order: bool,
h1_read_buf_exact_size: Option<usize>,
Expand Down Expand Up @@ -352,6 +353,7 @@ impl Builder {
h1_title_case_headers: false,
h1_preserve_header_case: false,
h1_max_headers: None,
h1_max_header_size: None,
#[cfg(feature = "ffi")]
h1_preserve_header_order: false,
h1_max_buf_size: None,
Expand Down Expand Up @@ -500,6 +502,17 @@ impl Builder {
self
}

/// Set the maximum size of response headers (including the status line) in bytes.
///
/// If the server sends headers exceeding this limit, the error "message head is too large"
/// is returned.
///
/// Default is `None`.
pub fn max_header_size(&mut self, val: usize) -> &mut Self {
self.h1_max_header_size = Some(val);
self
}

/// Set whether to support preserving original header order.
///
/// Currently, this will record the order in which headers are received, and store this
Expand Down Expand Up @@ -587,6 +600,9 @@ impl Builder {
if let Some(max_headers) = opts.h1_max_headers {
conn.set_http1_max_headers(max_headers);
}
if let Some(max_header_size) = opts.h1_max_header_size {
conn.set_http1_max_header_size(max_header_size);
}
#[cfg(feature = "ffi")]
if opts.h1_preserve_header_order {
conn.set_preserve_header_order();
Expand Down
11 changes: 9 additions & 2 deletions src/proto/h1/conn.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,7 @@ where
method: None,
h1_parser_config: ParserConfig::default(),
h1_max_headers: None,
h1_max_header_size: None,
#[cfg(feature = "server")]
h1_header_read_timeout: None,
#[cfg(feature = "server")]
Expand Down Expand Up @@ -141,6 +142,10 @@ where
self.state.h1_max_headers = Some(val);
}

pub(crate) fn set_http1_max_header_size(&mut self, val: usize) {
self.state.h1_max_header_size = Some(val);
}

#[cfg(feature = "server")]
pub(crate) fn set_http1_header_read_timeout(&mut self, val: Duration) {
self.state.h1_header_read_timeout = Some(val);
Expand Down Expand Up @@ -241,6 +246,7 @@ where
req_method: &mut self.state.method,
h1_parser_config: self.state.h1_parser_config.clone(),
h1_max_headers: self.state.h1_max_headers,
h1_max_header_size: self.state.h1_max_header_size,
preserve_header_case: self.state.preserve_header_case,
#[cfg(feature = "ffi")]
preserve_header_order: self.state.preserve_header_order,
Expand Down Expand Up @@ -309,15 +315,15 @@ where
self.try_keep_alive(cx);
}
} else if msg.expect_continue && msg.head.version.gt(&Version::HTTP_10) {
let h1_max_header_size = None; // TODO: remove this when we land h1_max_header_size support
let h1_max_header_size = self.state.h1_max_header_size;
self.state.reading = Reading::Continue(Decoder::new(
msg.decode,
self.state.h1_max_headers,
h1_max_header_size,
));
wants = wants.add(Wants::EXPECT);
} else {
let h1_max_header_size = None; // TODO: remove this when we land h1_max_header_size support
let h1_max_header_size = self.state.h1_max_header_size;
self.state.reading = Reading::Body(Decoder::new(
msg.decode,
self.state.h1_max_headers,
Expand Down Expand Up @@ -933,6 +939,7 @@ struct State {
method: Option<Method>,
h1_parser_config: ParserConfig,
h1_max_headers: Option<usize>,
h1_max_header_size: Option<usize>,
#[cfg(feature = "server")]
h1_header_read_timeout: Option<Duration>,
#[cfg(feature = "server")]
Expand Down
10 changes: 9 additions & 1 deletion src/proto/h1/io.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -188,6 +188,7 @@ where
req_method: parse_ctx.req_method,
h1_parser_config: parse_ctx.h1_parser_config.clone(),
h1_max_headers: parse_ctx.h1_max_headers,
h1_max_header_size: parse_ctx.h1_max_header_size,
preserve_header_case: parse_ctx.preserve_header_case,
#[cfg(feature = "ffi")]
preserve_header_order: parse_ctx.preserve_header_order,
Expand All @@ -200,8 +201,14 @@ where
self.partial_len = None;
return Poll::Ready(Ok(msg));
} else {
let max = self.read_buf_strategy.max();
let curr_len = self.read_buf.len();
if let Some(max_header_size) = parse_ctx.h1_max_header_size {
if curr_len >= max_header_size {
debug!("max_header_size ({}) reached, closing", max_header_size);
return Poll::Ready(Err(crate::Error::new_too_large()));
}
}
let max = self.read_buf_strategy.max();
if curr_len >= max {
debug!("max_buf_size ({}) reached, closing", max);
return Poll::Ready(Err(crate::Error::new_too_large()));
Expand Down Expand Up @@ -702,6 +709,7 @@ mod tests {
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down
1 change: 1 addition & 0 deletions src/proto/h1/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,7 @@ pub(crate) struct ParseContext<'ctx> {
req_method: &'ctx mut Option<Method>,
h1_parser_config: ParserConfig,
h1_max_headers: Option<usize>,
h1_max_header_size: Option<usize>,
preserve_header_case: bool,
#[cfg(feature = "ffi")]
preserve_header_order: bool,
Expand Down
95 changes: 95 additions & 0 deletions src/proto/h1/role.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -180,6 +180,11 @@ impl Http1Transaction for Server {
) {
Ok(httparse::Status::Complete(parsed_len)) => {
trace!("Request.parse Complete({})", parsed_len);
if let Some(max_header_size) = ctx.h1_max_header_size {
if parsed_len > max_header_size {
return Err(Parse::TooLarge);
}
}
len = parsed_len;
let uri = req.path.expect("httparse completed");
if uri.len() > MAX_URI_LEN {
Expand Down Expand Up @@ -1052,6 +1057,11 @@ impl Http1Transaction for Client {
) {
Ok(httparse::Status::Complete(len)) => {
trace!("Response.parse Complete({})", len);
if let Some(max_header_size) = ctx.h1_max_header_size {
if len > max_header_size {
return Err(Parse::TooLarge);
}
}
let status = StatusCode::from_u16(res.code.expect("httparse completed"))?;

let reason = {
Expand Down Expand Up @@ -1692,6 +1702,7 @@ mod tests {
req_method: &mut method,
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down Expand Up @@ -1720,6 +1731,7 @@ mod tests {
req_method: &mut Some(crate::Method::GET),
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand All @@ -1744,6 +1756,7 @@ mod tests {
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand All @@ -1765,6 +1778,7 @@ mod tests {
req_method: &mut Some(crate::Method::GET),
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand All @@ -1788,6 +1802,7 @@ mod tests {
req_method: &mut Some(crate::Method::GET),
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down Expand Up @@ -1815,6 +1830,7 @@ mod tests {
req_method: &mut Some(crate::Method::GET),
h1_parser_config,
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand All @@ -1839,6 +1855,7 @@ mod tests {
req_method: &mut Some(crate::Method::GET),
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down Expand Up @@ -1867,6 +1884,7 @@ mod tests {
req_method: &mut method,
h1_parser_config,
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down Expand Up @@ -1894,6 +1912,7 @@ mod tests {
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand All @@ -1914,6 +1933,7 @@ mod tests {
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: true,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down Expand Up @@ -1953,6 +1973,7 @@ mod tests {
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand All @@ -1974,6 +1995,7 @@ mod tests {
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down Expand Up @@ -2214,6 +2236,7 @@ mod tests {
req_method: &mut Some(Method::GET),
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand All @@ -2235,6 +2258,7 @@ mod tests {
req_method: &mut Some(m),
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand All @@ -2256,6 +2280,7 @@ mod tests {
req_method: &mut Some(Method::GET),
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down Expand Up @@ -2826,6 +2851,7 @@ mod tests {
req_method: &mut Some(Method::GET),
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down Expand Up @@ -2870,6 +2896,7 @@ mod tests {
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: max_headers,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand All @@ -2894,6 +2921,7 @@ mod tests {
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: max_headers,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down Expand Up @@ -2970,6 +2998,70 @@ mod tests {
parse(Some(200), 210, false);
}

#[test]
fn test_h1_max_header_size() {
let _ = pretty_env_logger::try_init();

let req_str = "GET / HTTP/1.1\r\nHost: example.com\r\n\r\n";
assert_eq!(req_str.len(), 37);
let resp_str = "HTTP/1.1 200 OK\r\nContent-Length: 0\r\n\r\n";
assert_eq!(resp_str.len(), 38);

let parse_req = |max_header_size: Option<usize>| {
let mut bytes = BytesMut::from(req_str);
Server::parse(
&mut bytes,
ParseContext {
cached_headers: &mut None,
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: max_header_size,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
h09_responses: false,
#[cfg(feature = "client")]
on_informational: &mut None,
},
)
};

let parse_resp = |max_header_size: Option<usize>| {
let mut bytes = BytesMut::from(resp_str);
Client::parse(
&mut bytes,
ParseContext {
cached_headers: &mut None,
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: max_header_size,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
h09_responses: false,
#[cfg(feature = "client")]
on_informational: &mut None,
},
)
};

// Server checks
parse_req(None).unwrap().unwrap();
parse_req(Some(37)).unwrap().unwrap();
parse_req(Some(50)).unwrap().unwrap();
assert!(matches!(parse_req(Some(36)), Err(Parse::TooLarge)));
assert!(matches!(parse_req(Some(10)), Err(Parse::TooLarge)));

// Client checks
parse_resp(None).unwrap().unwrap();
parse_resp(Some(38)).unwrap().unwrap();
parse_resp(Some(50)).unwrap().unwrap();
assert!(matches!(parse_resp(Some(37)), Err(Parse::TooLarge)));
assert!(matches!(parse_resp(Some(10)), Err(Parse::TooLarge)));
}

#[test]
fn test_is_complete_fast() {
let s = b"GET / HTTP/1.1\r\na: b\r\n\r\n";
Expand Down Expand Up @@ -3014,6 +3106,7 @@ mod tests {
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down Expand Up @@ -3097,6 +3190,7 @@ mod tests {
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down Expand Up @@ -3142,6 +3236,7 @@ mod tests {
req_method: &mut None,
h1_parser_config: Default::default(),
h1_max_headers: None,
h1_max_header_size: None,
preserve_header_case: false,
#[cfg(feature = "ffi")]
preserve_header_order: false,
Expand Down
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