Merge branch 'doh-client'.

This adds experimental support for resolving names using DNS over HTTPS (DoH)
for the Origin request mechanism.  To enable it, you must provide the client
with an `--origin-doh-base` option and give it a DoH base URL argument (like
`https://mozilla.cloudflare-dns.com/dns-query` as used by Mozilla, more
options [here](https://github.com/curl/curl/wiki/DNS-over-HTTPS)).

DoH requests are handled internally by the client and follow the usual request
routes, so they heed public/private browsing differences and enabled/disabled
request mechanisms.  This means that requests sent in private browsing mode
can use the Origin and Proxy mechanisms (thus staying private), and requests
sent in public mode can use Origin, Injector or Cache (and thus get retrieved
from others or cached and shared).

Separate DoH requests for both IPv4 and IPv6 addresses are always performed.
Entries cached by other clients can be fetched as long as they use the same
DoH base URL, IP version and stick to the minimal DNS query message (so that
they `GET` URLs match).

**Important note:** Results are not yet privately cached (beyond the
distributed cache), which means that each requested URL triggers a full DoH
request, which makes browsing quite slow.

CMakeLists.txt

@@ -121,6 +121,7 @@ file(GLOB client_sources
     "./src/util/reachability.cpp"
     "./src/util.cpp"
     "./src/util/handler_tracker.cpp"
+    "./src/doh.cpp"
     "./src/http_util.cpp"
     ${VERSION_CPP}
 )
@@ -140,6 +141,7 @@ target_link_libraries(client
         Boost::iostreams
         lib::asio_utp
         cpp_upnp
+        lib::zdnsparser
         lib::gcrypt
         lib::json
         lib::uri

cmake/OuinetDependencies.cmake

@@ -2,6 +2,7 @@
 include(${CMAKE_CURRENT_LIST_DIR}/dependencies/openssl.cmake)
 
 include(${CMAKE_CURRENT_LIST_DIR}/dependencies/boost.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/dependencies/zdnsparser.cmake)
 include(${CMAKE_CURRENT_LIST_DIR}/dependencies/gcrypt.cmake)
 include(${CMAKE_CURRENT_LIST_DIR}/dependencies/golang.cmake)
 include(${CMAKE_CURRENT_LIST_DIR}/dependencies/json.cmake)

cmake/dependencies/zdnsparser.cmake

+include(ExternalProject)
+
+set(ZDNSPARSER_FILENAME
+    "${CMAKE_CURRENT_BINARY_DIR}/zdnsparser/src/zdnsparser-build/lib/${CMAKE_STATIC_LIBRARY_PREFIX}zdnsparser${CMAKE_STATIC_LIBRARY_SUFFIX}"
+)
+
+set(PATCHES
+    ${CMAKE_CURRENT_LIST_DIR}/zdnsparser/disable-tests.patch
+    ${CMAKE_CURRENT_LIST_DIR}/zdnsparser/virtual-destructors.patch
+)
+
+set(PATCH_COMMAND
+    cd ${CMAKE_CURRENT_BINARY_DIR}/zdnsparser/src/zdnsparser
+)
+foreach (patch ${PATCHES})
+    set(PATCH_COMMAND ${PATCH_COMMAND} && patch -p1 -i ${patch})
+endforeach()
+
+externalproject_add(zdnsparser
+    # The specified commit supports answers with QNAME format,
+    # as indicated in <https://github.com/packetzero/dnsparser/pull/3>.
+    # Some DoH servers use the mentioned answer format.
+    GIT_REPOSITORY https://github.com/packetzero/dnsparser
+    GIT_TAG ad79c9b681f6afede9e9af8837159e1b2fbdb836
+    PATCH_COMMAND "${PATCH_COMMAND}"
+    UPDATE_COMMAND ""
+    INSTALL_COMMAND ""
+    CMAKE_ARGS
+        -DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}
+        -DCMAKE_CXX_FLAGS=${CMAKE_CXX_FLAGS}
+        -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
+        -DANDROID_ABI=${ANDROID_ABI}
+        -DANDROID_PLATFORM=${ANDROID_PLATFORM}
+    BUILD_BYPRODUCTS ${ZDNSPARSER_FILENAME}
+    PREFIX "zdnsparser"
+)
+
+add_library(lib_zdnsparser INTERFACE)
+add_dependencies(lib_zdnsparser zdnsparser)
+add_library(lib::zdnsparser ALIAS lib_zdnsparser)
+
+target_include_directories(lib_zdnsparser
+    INTERFACE
+        "${CMAKE_CURRENT_BINARY_DIR}/zdnsparser/src/zdnsparser/include"
+)
+target_link_libraries(lib_zdnsparser
+    INTERFACE ${ZDNSPARSER_FILENAME}
+)

cmake/dependencies/zdnsparser/disable-tests.patch

+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 1fa1462..6e9e8d8 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -24,5 +24,4 @@ include(cmake/cxx_flag_overrides.cmake)
+ # subdirs
+ 
+ add_subdirectory(src)
+-add_subdirectory(test)
+ 

cmake/dependencies/zdnsparser/virtual-destructors.patch

+diff --git a/include/dnsparser.h b/include/dnsparser.h
+index 4d81ea3..5dfaa6c 100644
+--- a/include/dnsparser.h
++++ b/include/dnsparser.h
+@@ -18,6 +18,8 @@
+ class DnsParserListener
+ {
+ public:
++  virtual ~DnsParserListener() = default;
++
+   /**
+    * @param addr Binary IPV4 or IPV6 address in network order.
+    * @param name Domain name requested.
+@@ -30,6 +32,8 @@ public:
+ class DnsParser
+ {
+ public:
++  virtual ~DnsParser() = default;
++
+   /**
+    * parse
+    * When response records are discovered, DnsParserListener.onDnsRec()

scripts/add-licenses-dir.sh

@@ -26,6 +26,7 @@ json;Niels Lohmann;${BUILD}/json/src/json/LICENSE.MIT
 uri;Glyn Matthews;${BUILD}/uri/src/uri/LICENSE_1_0.txt
 asio-utp;Peter Jankuliak;${SRC}/modules/asio-utp/LICENSE.txt
 lampshade;various;${BUILD}/src/ouiservice/lampshade/lampshade-prefix/src/lampshade/LICENSE
+zdnsparser;various;${SRC}/scripts/licenses/Apache-2.0
 "
 
 echo "$LICENSE_DATA" | (

scripts/licenses/Apache-2.0

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src/client.cpp

@@ -15,6 +15,7 @@
 #include <boost/range/adaptor/transformed.hpp>
 #include <boost/range/adaptor/indexed.hpp>
 #include <boost/regex.hpp>
+#include <iterator>
 #include <iostream>
 #include <cstdlib>  // for atexit()
 
@@ -22,6 +23,7 @@
 
 #include "namespaces.h"
 #include "origin_pools.h"
+#include "doh.h"
 #include "http_util.h"
 #include "fetch_http_page.h"
 #include "client_front_end.h"
@@ -85,6 +87,7 @@ namespace bt = ouinet::bittorrent;
 using tcp      = asio::ip::tcp;
 using Request  = http::request<http::string_body>;
 using Response = http::response<http::dynamic_body>;
+using TcpLookup = tcp::resolver::results_type;
 
 static const fs::path OUINET_CA_CERT_FILE = "ssl-ca-cert.pem";
 static const fs::path OUINET_CA_KEY_FILE = "ssl-ca-key.pem";
@@ -123,6 +126,15 @@ struct UserAgentMetaData {
 
         return ret;
     }
+
+    // Apply the metadata to the given request.
+    template<class Req>
+    void apply_to(Req& rq) const {
+        if (is_private && *is_private)
+            rq.set(http_::request_private_hdr, http_::request_private_true);
+        if (dht_group)
+            rq.set(http_::request_group_hdr, *dht_group);
+    }
 };
 
 //------------------------------------------------------------------------------
@@ -232,8 +244,14 @@ private:
                           , Cancel& cancel
                           , Yield yield);
 
+    template<class Rq>
+    Session fetch_via_self( Rq, const UserAgentMetaData&
+                          , Cancel&, Yield);
+
     Response fetch_fresh_from_front_end(const Request&, Yield);
-    Session fetch_fresh_from_origin(const Request&, Cancel, Yield);
+    Session fetch_fresh_from_origin( const Request&
+                                   , const UserAgentMetaData&
+                                   , Cancel, Yield);
 
     Session fetch_fresh_through_connect_proxy(const Request&, Cancel&, Yield);
 
@@ -282,7 +300,17 @@ private:
                                        , Request&
                                        , Yield);
 
-    GenericStream connect_to_origin(const Request&, Cancel&, Yield);
+    // Resolve host and port strings.
+    TcpLookup resolve_tcp_dns( const std::string&, const std::string&
+                             , Cancel&, Yield);
+    TcpLookup resolve_tcp_doh( const std::string&, const std::string&
+                             , const UserAgentMetaData&
+                             , const doh::Endpoint&
+                             , Cancel&, Yield);
+
+    GenericStream connect_to_origin( const Request&
+                                   , const UserAgentMetaData&
+                                   , Cancel&, Yield);
 
     unique_ptr<OuiServiceImplementationClient>
     maybe_wrap_tls(unique_ptr<OuiServiceImplementationClient>);
@@ -373,6 +401,7 @@ private:
     // For debugging
     uint64_t _next_connection_id = 0;
     ConnectionPool<Endpoint> _injector_connections;
+    ConnectionPool<bool> _self_connections;  // stored value is unused
     OriginPools _origin_pools;
 
     asio::ssl::context ssl_ctx;
@@ -538,8 +567,195 @@ Client::State::fetch_stored_in_dcache( const Request& request
 }
 
 //------------------------------------------------------------------------------
+template<class Rq>
+Session
+Client::State::fetch_via_self( Rq request, const UserAgentMetaData& meta
+                             , Cancel& cancel, Yield yield)
+{
+    sys::error_code ec;
+
+    // Connect to the client proxy port.
+    // TODO: Maybe refactor with `fetch_fresh_through_simple_proxy`.
+    ConnectionPool<bool>::Connection con;
+    if (_self_connections.empty()) {
+        if (log_transactions()) {
+            yield.log("Connecting to self");
+        }
+
+        // TODO: Keep lookup object or allow connecting to endpoint.
+        auto epl = TcpLookup::create(_config.local_endpoint(), "dummy", "dummy");
+        auto c = connect_to_host(epl, _ctx.get_executor(), cancel, yield[ec]);
+
+        assert(!cancel || ec == asio::error::operation_aborted);
+
+        if (ec) {
+            if (log_transactions()) {
+                yield.log("Failed to connect to self ec:", ec.message());
+            }
+            return or_throw<Session>(yield, ec);
+        }
+
+        con = _self_connections.wrap(std::move(c));
+    } else {
+        if (log_transactions()) {
+            yield.log("Reusing existing self connection");
+        }
+
+        con = _self_connections.pop_front();
+    }
+
+    auto cancel_slot = cancel.connect([&] {
+        con.close();
+    });
+
+    // Build the actual request to send to self.
+    if (!_config.client_credentials().empty())
+        request = authorize(request, _config.client_credentials());
+    request.keep_alive(true);
+    meta.apply_to(request);
+
+    if (log_transactions()) {
+        yield.log("Sending a request to self");
+    }
+    // Send request
+    http::async_write(con, request, yield[ec].tag("self-request"));
+
+    if (cancel_slot) {
+        ec = asio::error::operation_aborted;
+    }
+
+    if (ec && log_transactions()) {
+        yield.log("Failed to send request to self");
+    }
+
+    if (ec) return or_throw<Session>(yield, ec);
+
+    return Session::create(move(con), cancel, yield);
+}
+
+// Transforms addresses to endpoints with the given port.
+template<class Addrs, class Endpoint>
+class AddrsAsEndpoints {
+public:
+    using value_type = Endpoint;
+    using addrs_iterator = typename Addrs::const_iterator;
+
+    AddrsAsEndpoints(const Addrs& addrs, unsigned short port)
+        : _addrs(addrs), _port(port)
+    {}
+
+    class const_iterator : public std::iterator<std::input_iterator_tag, value_type> {
+    public:
+        const_iterator(const addrs_iterator& it, unsigned short port)
+            : _it(it), _port(port)
+        {}
+
+        value_type operator*() const { return {*_it, _port}; }
+        const_iterator& operator++() { ++_it; return *this; }
+        bool operator==(const const_iterator& other) const { return _it == other._it; }
+        bool operator!=(const const_iterator& other) const { return _it != other._it; }
+    private:
+        addrs_iterator _it;
+        unsigned short _port;
+    };
+
+    const_iterator begin() const { return {_addrs.begin(), _port}; };
+    const_iterator end() const { return {_addrs.end(), _port}; };
+
+private:
+    const Addrs& _addrs;
+    unsigned short _port;
+};
+
+TcpLookup
+Client::State::resolve_tcp_doh( const std::string& host
+                              , const std::string& port
+                              , const UserAgentMetaData& meta
+                              , const doh::Endpoint& ep
+                              , Cancel& cancel
+                              , Yield yield)
+{
+    using TcpEndpoint = typename TcpLookup::endpoint_type;
+
+    boost::string_view portsv(port);
+    auto portn_o = parse::number<unsigned short>(portsv);
+    if (!portn_o) return or_throw<TcpLookup>(yield, asio::error::invalid_argument);
+
+    // Build and return lookup if `host` is already a network address.
+    {
+        sys::error_code e;
+        auto addr = asio::ip::make_address(host, e);
+        if (!e) return TcpLookup::create(TcpEndpoint{move(addr), *portn_o}, host, port);
+    }
+
+    // TODO: When to disable queries for IPv4 or IPv6 addresses?
+    auto rq4_o = doh::build_request_ipv4(host, ep);
+    auto rq6_o = doh::build_request_ipv6(host, ep);
+    if (!rq4_o || !rq6_o) return or_throw<TcpLookup>(yield, asio::error::invalid_argument);
+
+    sys::error_code ec4, ec6;
+    doh::Response rs4, rs6;
+
+    WaitCondition wc(_ctx);
+
+    // By passing user agent metadata as is,
+    // we ensure that the DoH request is done with the same browsing mode
+    // as the content request that triggered it,
+    // and is announced under the same group.
+    // TODO: Handle redirects.
+#define SPAWN_QUERY(VER) \
+    TRACK_SPAWN(_ctx, ([ \
+        this, \
+        rq = move(*rq##VER##_o), &meta, &ec##VER, &rs##VER, \
+        &cancel, &yield, lock = wc.lock() \
+    ] (asio::yield_context y_) { \
+        sys::error_code ec; \
+        auto y = yield.detach(y_); \
+        auto s = fetch_via_self(move(rq), meta, cancel, y[ec].tag("fetch##VER")); \
+        if (ec) { ec##VER = ec; return; } \
+        rs##VER = http_response::slurp_response<doh::Response::body_type> \
+            (s, doh::payload_size, cancel, y[ec].tag("slurp##VER")); \
+        if (ec) { ec##VER = ec; return; } \
+    }));
+    SPAWN_QUERY(4);
+    SPAWN_QUERY(6);
+
+    wc.wait(yield.tag("wait"));
+
+    if (log_transactions())
+        yield.log("DoH query ip4_ec:", ec4.message(), " ip6_ec:", ec6.message());
+    if (ec4 && ec6) return or_throw<TcpLookup>(yield, ec4 /* arbitrary */);
+
+    doh::Answers answers4, answers6;
+    if (!ec4) answers4 = doh::parse_response(rs4, host, ec4);
+    if (!ec6) answers6 = doh::parse_response(rs6, host, ec6);
+
+    if (log_transactions())
+        yield.log("DoH parse ip4_ec:", ec4.message(), " ip6_ec:", ec6.message());
+    if (ec4 && ec6) return or_throw<TcpLookup>(yield, ec4 /* arbitrary */);
+
+    answers4.insert( answers4.end()
+                   , std::make_move_iterator(answers6.begin())
+                   , std::make_move_iterator(answers6.end()));
+    AddrsAsEndpoints<doh::Answers, TcpEndpoint> eps{answers4, *portn_o};
+    return TcpLookup::create(eps.begin(), eps.end(), host, port);
+}
+
+TcpLookup
+Client::State::resolve_tcp_dns( const std::string& host
+                              , const std::string& port
+                              , Cancel& cancel
+                              , Yield yield)
+{
+    return util::tcp_async_resolve( host, port
+                                  , _ctx.get_executor()
+                                  , cancel
+                                  , yield);
+}
+
 GenericStream
 Client::State::connect_to_origin( const Request& rq
+                                , const UserAgentMetaData& meta
                                 , Cancel& cancel
                                 , Yield yield)
 {
@@ -548,11 +764,15 @@ Client::State::connect_to_origin( const Request& rq
 
     sys::error_code ec;
 
-    auto lookup = util::tcp_async_resolve( host, port
-                                         , _ctx.get_executor()
-                                         , cancel
-                                         , yield[ec]);
-
+    // Resolve using DoH if configured and not resolving the resolver's address itself.
+    auto doh_ep_o = _config.origin_doh_endpoint();
+    bool do_doh = doh_ep_o && !rq.target().starts_with(*doh_ep_o);
+    auto lookup = do_doh
+        ? resolve_tcp_doh(host, port, meta, *doh_ep_o, cancel, yield[ec].tag("resolve_doh"))
+        : resolve_tcp_dns(host, port, cancel, yield[ec].tag("resolve_dns"));
+    if (log_transactions())
+        yield.log( do_doh ? "DoH name resolution: " : "DNS name resolution: "
+                 , host, " naddrs=", lookup.size(), " ec:", ec.message());
     return_or_throw_on_error(yield, cancel, ec, GenericStream());
 
     auto sock = connect_to_host(lookup, _ctx.get_executor(), cancel, yield[ec]);
@@ -603,7 +823,9 @@ Response Client::State::fetch_fresh_from_front_end(const Request& rq, Yield yiel
 }
 
 //------------------------------------------------------------------------------
-Session Client::State::fetch_fresh_from_origin(const Request& rq, Cancel cancel, Yield yield)
+Session Client::State::fetch_fresh_from_origin( const Request& rq
+                                              , const UserAgentMetaData& meta