From 373d135e7492d63f14915d989e4e3e97d63f028c Mon Sep 17 00:00:00 2001 From: Sergey Bugaev Date: Sun, 14 Feb 2021 17:24:23 +0300 Subject: [PATCH] LookupServer: Implement a DNS server :^) LookupServer can now itself server as a DNS server! To service DNS clients, it uses the exact same lookup logic as it does for LibIPC clients. Namely, it will synthesize records for data from /etc/hosts on its own (you can use this to configure host names for your domain!), and forward other questions to configured upstream DNS servers. On top of that, it implements its own caching, so once a DNS resource record has been obtained from an upstream server, LookupServer will cache it locally for faster future lookups. The DNS server part of LookupServer is disabled by default, because it requires you to run it as root (for it to bind to the port 53) and on boot, and we don't want either by default. If you want to try it, modify SystemServer.ini like so: [LookupServer] Socket=/tmp/portal/lookup SocketPermissions=666 Priority=low KeepAlive=1 User=root BootModes=text,graphical and enable server mode in LookupServer.ini like so: [DNS] Nameservers=... EnableServer=1 If in the future we implement socket takeover for IP sockets, these limitations may be lifted. --- Base/etc/LookupServer.ini | 1 + Userland/Services/LookupServer/CMakeLists.txt | 1 + Userland/Services/LookupServer/DNSPacket.cpp | 8 ++ Userland/Services/LookupServer/DNSPacket.h | 1 + Userland/Services/LookupServer/DNSServer.cpp | 84 +++++++++++++++++++ Userland/Services/LookupServer/DNSServer.h | 42 ++++++++++ .../Services/LookupServer/LookupServer.cpp | 5 ++ Userland/Services/LookupServer/LookupServer.h | 5 +- 8 files changed, 145 insertions(+), 2 deletions(-) create mode 100644 Userland/Services/LookupServer/DNSServer.cpp create mode 100644 Userland/Services/LookupServer/DNSServer.h diff --git a/Base/etc/LookupServer.ini b/Base/etc/LookupServer.ini index 9fedd22837..b7185e689b 100644 --- a/Base/etc/LookupServer.ini +++ b/Base/etc/LookupServer.ini @@ -1,2 +1,3 @@ [DNS] Nameservers=1.1.1.1,1.0.0.1 +EnableServer=0 diff --git a/Userland/Services/LookupServer/CMakeLists.txt b/Userland/Services/LookupServer/CMakeLists.txt index 5b99be3de8..7831df7481 100644 --- a/Userland/Services/LookupServer/CMakeLists.txt +++ b/Userland/Services/LookupServer/CMakeLists.txt @@ -5,6 +5,7 @@ set(SOURCES DNSAnswer.cpp DNSName.cpp DNSPacket.cpp + DNSServer.cpp LookupServer.cpp LookupServerEndpoint.h LookupClientEndpoint.h diff --git a/Userland/Services/LookupServer/DNSPacket.cpp b/Userland/Services/LookupServer/DNSPacket.cpp index afd2b745b4..0d30ac6761 100644 --- a/Userland/Services/LookupServer/DNSPacket.cpp +++ b/Userland/Services/LookupServer/DNSPacket.cpp @@ -44,6 +44,13 @@ void DNSPacket::add_question(const DNSQuestion& question) ASSERT(m_questions.size() <= UINT16_MAX); } +void DNSPacket::add_answer(const DNSAnswer& answer) +{ + m_answers.empend(answer); + + ASSERT(m_answers.size() <= UINT16_MAX); +} + ByteBuffer DNSPacket::to_byte_buffer() const { DNSPacketHeader header; @@ -54,6 +61,7 @@ ByteBuffer DNSPacket::to_byte_buffer() const header.set_is_response(); // FIXME: What should this be? header.set_opcode(0); + header.set_response_code(m_code); header.set_truncated(false); // hopefully... header.set_recursion_desired(true); // FIXME: what should the be for requests? diff --git a/Userland/Services/LookupServer/DNSPacket.h b/Userland/Services/LookupServer/DNSPacket.h index 41912c9f2d..bfda9cd5e9 100644 --- a/Userland/Services/LookupServer/DNSPacket.h +++ b/Userland/Services/LookupServer/DNSPacket.h @@ -80,6 +80,7 @@ public: } void add_question(const DNSQuestion&); + void add_answer(const DNSAnswer&); enum class Code : u8 { NOERROR = 0, diff --git a/Userland/Services/LookupServer/DNSServer.cpp b/Userland/Services/LookupServer/DNSServer.cpp new file mode 100644 index 0000000000..81ff783a53 --- /dev/null +++ b/Userland/Services/LookupServer/DNSServer.cpp @@ -0,0 +1,84 @@ +/* + * Copyright (c) 2021, Sergey Bugaev + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * 1. Redistributions of source code must retain the above copyright notice, this + * list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR + * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER + * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "DNSServer.h" +#include "DNSPacket.h" +#include "LookupServer.h" +#include + +namespace LookupServer { + +DNSServer::DNSServer(Object* parent) + : Core::UDPServer(parent) +{ + bind(IPv4Address(), 53); + on_ready_to_receive = [this]() { + handle_client(); + }; +} + +void DNSServer::handle_client() +{ + sockaddr_in client_address; + auto buffer = receive(1024, client_address); + auto optional_request = DNSPacket::from_raw_packet(buffer.data(), buffer.size()); + if (!optional_request.has_value()) { + dbgln("Got an invalid DNS packet"); + return; + } + auto& request = optional_request.value(); + + if (!request.is_query()) { + dbgln("It's not a request"); + return; + } + + LookupServer& lookup_server = LookupServer::the(); + + DNSPacket response; + response.set_is_response(); + response.set_id(request.id()); + + for (auto& question : request.questions()) { + if (question.class_code() != C_IN) + continue; + response.add_question(question); + auto answers = lookup_server.lookup(question.name(), question.record_type()); + for (auto& answer : answers) { + response.add_answer(answer); + } + } + + if (response.answer_count() == 0) + response.set_code(DNSPacket::Code::NXDOMAIN); + else + response.set_code(DNSPacket::Code::NOERROR); + + buffer = response.to_byte_buffer(); + sendto(fd(), buffer.data(), buffer.size(), 0, (const sockaddr*)&client_address, sizeof(client_address)); +} + +} diff --git a/Userland/Services/LookupServer/DNSServer.h b/Userland/Services/LookupServer/DNSServer.h new file mode 100644 index 0000000000..24a055e586 --- /dev/null +++ b/Userland/Services/LookupServer/DNSServer.h @@ -0,0 +1,42 @@ +/* + * Copyright (c) 2021, Sergey Bugaev + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * 1. Redistributions of source code must retain the above copyright notice, this + * list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR + * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER + * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#pragma once + +#include + +namespace LookupServer { + +class DNSServer : public Core::UDPServer { + C_OBJECT(DNSServer) + +private: + explicit DNSServer(Object* parent = nullptr); + + void handle_client(); +}; + +} diff --git a/Userland/Services/LookupServer/LookupServer.cpp b/Userland/Services/LookupServer/LookupServer.cpp index 75d9aa124c..2185c4fea1 100644 --- a/Userland/Services/LookupServer/LookupServer.cpp +++ b/Userland/Services/LookupServer/LookupServer.cpp @@ -62,6 +62,11 @@ LookupServer::LookupServer() load_etc_hosts(); + if (config->read_bool_entry("DNS", "EnableServer")) { + m_dns_server = DNSServer::construct(this); + // TODO: drop root privileges here. + } + m_local_server = Core::LocalServer::construct(this); m_local_server->on_ready_to_accept = [this]() { auto socket = m_local_server->accept(); diff --git a/Userland/Services/LookupServer/LookupServer.h b/Userland/Services/LookupServer/LookupServer.h index 7c01a2a432..f19ec7ed09 100644 --- a/Userland/Services/LookupServer/LookupServer.h +++ b/Userland/Services/LookupServer/LookupServer.h @@ -26,8 +26,9 @@ #pragma once -#include "DNSPacket.h" #include "DNSName.h" +#include "DNSPacket.h" +#include "DNSServer.h" #include namespace LookupServer { @@ -49,8 +50,8 @@ private: Vector lookup(const DNSName& hostname, const String& nameserver, bool& did_get_response, unsigned short record_type, ShouldRandomizeCase = ShouldRandomizeCase::Yes); - RefPtr m_local_server; + RefPtr m_dns_server; Vector m_nameservers; HashMap, DNSName::Traits> m_etc_hosts; HashMap, DNSName::Traits> m_lookup_cache;