From 48a99fd71b11321b85c385245b5f2d36fed22df1 Mon Sep 17 00:00:00 2001
From: Rutger Broekhoff
Date: Thu, 10 Sep 2026 23:10:57 +0200
Subject: Fun with (raw) deflate

---
 server/src/srv.cpp | 141 +++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 131 insertions(+), 10 deletions(-)

(limited to 'server/src/srv.cpp')

diff --git a/server/src/srv.cpp b/server/src/srv.cpp
index adfef18..a901f8e 100644
--- a/server/src/srv.cpp
+++ b/server/src/srv.cpp
@@ -6,6 +6,7 @@ module;
 #include <boost/asio/ip/tcp.hpp>
 #include <boost/beast/core.hpp>
 #include <boost/beast/http.hpp>
+#include <boost/beast/zlib.hpp>
 #include <boost/config.hpp>
 #include <boost/json.hpp>
 #include <boost/locale/generator.hpp>
@@ -156,10 +157,8 @@ struct readable_gpx_body
       auto total = 0uz;
       try
       {
-        for (auto it = net::buffer_sequence_begin(b);
-             it != net::buffer_sequence_end(b); it++)
+        for (auto cur_in_buf : beast::buffers_range(b))
         {
-          auto cur_in_buf = net::const_buffer{*it};
           while (cur_in_buf.size() > 0)
           {
             auto to_read =
@@ -217,6 +216,120 @@ struct readable_gpx_body
 static_assert(bhttp::concepts::body<readable_gpx_body>);
 static_assert(bhttp::concepts::body_reader<readable_gpx_body>);
 
+template <bhttp::concepts::body_reader Inner>
+struct raw_deflate_body
+{
+  using value_type = Inner::value_type;
+
+  class reader
+  {
+    static constexpr auto const chunk_size = 16384;
+
+    Inner::reader r_;
+    bool stream_ended_ = false;
+    beast::zlib::z_params zs_ = {};
+    beast::zlib::inflate_stream inflate_strm_ = {};
+    std::unique_ptr<std::array<char, chunk_size>> in_buf_ = nullptr;
+    std::unique_ptr<std::array<char, chunk_size>> out_buf_ = nullptr;
+
+    auto inflate_chunk(beast::error_code& ec) -> void
+    {
+      assert(zs_.avail_in > 0);
+      zs_.next_in = in_buf_->data();
+
+      do
+      {
+        zs_.avail_out = out_buf_->size();
+        zs_.next_out = out_buf_->data();
+
+        inflate_strm_.write(zs_, beast::zlib::Flush::none, ec);
+        assert(ec != beast::zlib::error::stream_error);
+        if (ec == beast::zlib::error::need_buffers)
+          ec = {};
+        if (ec == beast::zlib::error::end_of_stream)
+        {
+          ec = {};
+          stream_ended_ = true;
+        }
+        if (ec)
+          break;
+
+        auto have = chunk_size - zs_.avail_out;
+        auto cbuf =
+            net::buffer(static_cast<void const*>(out_buf_->data()), have);
+
+        auto inner_ec = beast::error_code{};
+        do
+          cbuf += r_.put(cbuf, inner_ec);
+        while (cbuf.size() > 0 && !inner_ec);
+        if (inner_ec)
+        {
+          ec = inner_ec;
+          break;
+        }
+      }
+      while (zs_.avail_out == 0);
+
+      // In the last case (stream_ended_), the user has sent too much data
+      assert(zs_.avail_in == 0 || ec || stream_ended_);
+    }
+
+  public:
+    template <bool isRequest, bhttp::concepts::fields Fields>
+    explicit reader(bhttp::header<isRequest, Fields>& hdr, value_type& v)
+      : r_{hdr, v}
+    {
+    }
+
+    auto
+    init(boost::optional<std::uint64_t> /* n */, beast::error_code& ec) noexcept
+        -> void
+    {
+      in_buf_.reset(new std::array<char, chunk_size>{});
+      out_buf_.reset(new std::array<char, chunk_size>{});
+      ec = {};
+    }
+
+    auto
+    put(beast::concepts::const_buffer_sequence auto b,
+        beast::error_code& ec) noexcept -> std::size_t
+    {
+      auto in_buf = net::buffer(in_buf_->data(), in_buf_->size());
+      in_buf += zs_.avail_in;
+
+      auto consumed_from_b = net::buffer_copy(in_buf, b);
+      zs_.avail_in += consumed_from_b;
+
+      if (zs_.avail_in == in_buf_->size())
+        inflate_chunk(ec);
+      else
+        ec = {};
+
+      return consumed_from_b;
+    }
+
+    auto finish(beast::error_code& ec) noexcept
+    {
+      ec = {};
+      if (zs_.avail_in > 0)
+        inflate_chunk(ec);
+      if (!ec && !stream_ended_)
+        ec = beast::zlib::error::stream_error;
+      if (stream_ended_ && zs_.avail_in > 0)
+        // client sent data past deflate stream end
+        ec = beast::zlib::error::stream_error;
+
+      in_buf_.reset();
+      out_buf_.reset();
+      inflate_strm_.reset();
+      if (!ec)
+      {
+        r_.finish(ec);
+      }
+    }
+  };
+};
+
 auto handler::handle_process_gpx(l0_ctx ctx, http::readable_request r)
     -> net::awaitable<http::presponse>
 {
@@ -228,23 +341,31 @@ auto handler::handle_process_gpx(l0_ctx ctx, http::readable_request r)
   {
     l.debug("Reading GPX request body");
     auto const before_read_gpx = chrono::steady_clock::now();
-    auto req =
-        co_await http::read_request<readable_gpx_body>(ctx, std::move(r));
+    auto parse_res =
+        r.p->get()[bhttp::field::content_encoding] == "x-deflate-raw"
+            ? std::move(
+                  (co_await http::read_request<raw_deflate_body<readable_gpx_body>>(
+                       ctx, std::move(r)))
+                      .body())
+            : std::move((co_await http::read_request<readable_gpx_body>(
+                             ctx, std::move(r)))
+                            .body());
     l.debug(
         "Read GPX request body in {}; init took {}, actual parsing {}, "
         "finishing {}",
         chrono::duration<double, std::milli>{
           chrono::steady_clock::now() - before_read_gpx
         },
-        chrono::duration<double, std::milli>{req->body().init_parse_duration()},
-        chrono::duration<double, std::milli>{req->body().put_parse_duration()},
+        chrono::duration<double, std::milli>{parse_res.init_parse_duration()},
+        chrono::duration<double, std::milli>{parse_res.put_parse_duration()},
         chrono::duration<double, std::milli>{
-          req->body().finish_parse_duration()
+          parse_res.finish_parse_duration()
         });
-    gpx_file = std::move(req->body().unwrap());
+    gpx_file = std::move(parse_res.unwrap());
   }
   catch (std::exception& ex)
   {
+    l_.warn("Failed to parse GPX file: {}", ex.what());
     // TODO: more detailed problem reporting
     auto tpl = problem::tpl{
       .status = bhttp::status::bad_request,
@@ -280,7 +401,7 @@ auto handler::handle_process_gpx(l0_ctx ctx, http::readable_request r)
 auto handler::handle_sysinfo(l0_ctx ctx, http::readable_request r)
     -> net::awaitable<http::presponse>
 {
-  auto req = co_await http::read_request<bhttp::empty_body>(ctx, std::move(r));
+  auto req = co_await http::read_empty_request(ctx, std::move(r));
   auto info = inner_.sysinfo();
 
   auto rsp = http::make_rsp<bhttp::string_body>(
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