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serenity/Userland/Services/LookupServer/LookupServer.cpp
Andreas Kling 5d180d1f99 Everywhere: Rename ASSERT => VERIFY
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)

Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.

We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
2021-02-23 20:56:54 +01:00

319 lines
11 KiB
C++

/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
* 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 "LookupServer.h"
#include "ClientConnection.h"
#include "DNSPacket.h"
#include <AK/ByteBuffer.h>
#include <AK/Debug.h>
#include <AK/HashMap.h>
#include <AK/String.h>
#include <AK/StringBuilder.h>
#include <LibCore/ConfigFile.h>
#include <LibCore/File.h>
#include <LibCore/LocalServer.h>
#include <LibCore/LocalSocket.h>
#include <LibCore/UDPSocket.h>
#include <stdio.h>
#include <sys/time.h>
#include <unistd.h>
namespace LookupServer {
static LookupServer* s_the;
LookupServer& LookupServer::the()
{
VERIFY(s_the);
return *s_the;
}
LookupServer::LookupServer()
{
VERIFY(s_the == nullptr);
s_the = this;
auto config = Core::ConfigFile::get_for_system("LookupServer");
dbgln("Using network config file at {}", config->file_name());
m_nameservers = config->read_entry("DNS", "Nameservers", "1.1.1.1,1.0.0.1").split(',');
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();
if (!socket) {
dbgln("Failed to accept a client connection");
return;
}
static int s_next_client_id = 0;
int client_id = ++s_next_client_id;
IPC::new_client_connection<ClientConnection>(socket.release_nonnull(), client_id);
};
bool ok = m_local_server->take_over_from_system_server();
VERIFY(ok);
}
void LookupServer::load_etc_hosts()
{
// The TTL we return for static data from /etc/hosts.
// The value here is 1 day.
static constexpr u32 static_ttl = 86400;
auto add_answer = [this](const DNSName& name, unsigned short record_type, String data) {
auto it = m_etc_hosts.find(name);
if (it == m_etc_hosts.end()) {
m_etc_hosts.set(name, {});
it = m_etc_hosts.find(name);
}
it->value.empend(name, record_type, (u16)C_IN, static_ttl, data);
};
auto file = Core::File::construct("/etc/hosts");
if (!file->open(Core::IODevice::ReadOnly))
return;
while (!file->eof()) {
auto line = file->read_line(1024);
if (line.is_empty())
break;
auto fields = line.split('\t');
auto sections = fields[0].split('.');
IPv4Address addr {
(u8)atoi(sections[0].characters()),
(u8)atoi(sections[1].characters()),
(u8)atoi(sections[2].characters()),
(u8)atoi(sections[3].characters()),
};
auto raw_addr = addr.to_in_addr_t();
DNSName name = fields[1];
add_answer(name, T_A, String { (const char*)&raw_addr, sizeof(raw_addr) });
IPv4Address reverse_addr {
(u8)atoi(sections[3].characters()),
(u8)atoi(sections[2].characters()),
(u8)atoi(sections[1].characters()),
(u8)atoi(sections[0].characters()),
};
StringBuilder builder;
builder.append(reverse_addr.to_string());
builder.append(".in-addr.arpa");
add_answer(builder.to_string(), T_PTR, name.as_string());
}
}
Vector<DNSAnswer> LookupServer::lookup(const DNSName& name, unsigned short record_type)
{
#if LOOKUPSERVER_DEBUG
dbgln("Got request for '{}'", name.as_string());
#endif
Vector<DNSAnswer> answers;
auto add_answer = [&](const DNSAnswer& answer) {
DNSAnswer answer_with_original_case {
name,
answer.type(),
answer.class_code(),
answer.ttl(),
answer.record_data()
};
answers.append(answer_with_original_case);
};
// First, try local data.
if (auto local_answers = m_etc_hosts.get(name); local_answers.has_value()) {
for (auto& answer : local_answers.value()) {
if (answer.type() == record_type)
add_answer(answer);
}
if (!answers.is_empty())
return answers;
}
// Second, try our cache.
if (auto cached_answers = m_lookup_cache.get(name); cached_answers.has_value()) {
for (auto& answer : cached_answers.value()) {
// TODO: Actually remove expired answers from the cache.
if (answer.type() == record_type && !answer.has_expired()) {
#if LOOKUPSERVER_DEBUG
dbgln("Cache hit: {} -> {}", name.as_string(), answer.record_data());
#endif
add_answer(answer);
}
}
if (!answers.is_empty())
return answers;
}
// Third, ask the upstream nameservers.
for (auto& nameserver : m_nameservers) {
#if LOOKUPSERVER_DEBUG
dbgln("Doing lookup using nameserver '{}'", nameserver);
#endif
bool did_get_response = false;
int retries = 3;
Vector<DNSAnswer> upstream_answers;
do {
upstream_answers = lookup(name, nameserver, did_get_response, record_type);
if (did_get_response)
break;
} while (--retries);
if (!upstream_answers.is_empty()) {
for (auto& answer : upstream_answers)
add_answer(answer);
break;
} else {
if (!did_get_response)
dbgln("Never got a response from '{}', trying next nameserver", nameserver);
else
dbgln("Received response from '{}' but no result(s), trying next nameserver", nameserver);
}
}
if (answers.is_empty()) {
dbgln("Tried all nameservers but never got a response :(");
return {};
}
return move(answers);
}
Vector<DNSAnswer> LookupServer::lookup(const DNSName& name, const String& nameserver, bool& did_get_response, unsigned short record_type, ShouldRandomizeCase should_randomize_case)
{
DNSPacket request;
request.set_is_query();
request.set_id(arc4random_uniform(UINT16_MAX));
DNSName name_in_question = name;
if (should_randomize_case == ShouldRandomizeCase::Yes)
name_in_question.randomize_case();
request.add_question({ name_in_question, record_type, C_IN });
auto buffer = request.to_byte_buffer();
auto udp_socket = Core::UDPSocket::construct();
udp_socket->set_blocking(true);
struct timeval timeout {
1, 0
};
int rc = setsockopt(udp_socket->fd(), SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout));
if (rc < 0) {
perror("setsockopt(SOL_SOCKET, SO_RCVTIMEO)");
return {};
}
if (!udp_socket->connect(nameserver, 53))
return {};
if (!udp_socket->write(buffer))
return {};
u8 response_buffer[4096];
int nrecv = udp_socket->read(response_buffer, sizeof(response_buffer));
if (nrecv == 0)
return {};
did_get_response = true;
auto o_response = DNSPacket::from_raw_packet(response_buffer, nrecv);
if (!o_response.has_value())
return {};
auto& response = o_response.value();
if (response.id() != request.id()) {
dbgln("LookupServer: ID mismatch ({} vs {}) :(", response.id(), request.id());
return {};
}
if (response.code() == DNSPacket::Code::REFUSED) {
if (should_randomize_case == ShouldRandomizeCase::Yes) {
// Retry with 0x20 case randomization turned off.
return lookup(name, nameserver, did_get_response, record_type, ShouldRandomizeCase::No);
}
return {};
}
if (response.question_count() != request.question_count()) {
dbgln("LookupServer: Question count ({} vs {}) :(", response.question_count(), request.question_count());
return {};
}
// Verify the questions in our request and in their response match exactly, including case.
for (size_t i = 0; i < request.question_count(); ++i) {
auto& request_question = request.questions()[i];
auto& response_question = response.questions()[i];
bool exact_match = request_question.class_code() == response_question.class_code()
&& request_question.record_type() == response_question.record_type()
&& request_question.name().as_string() == response_question.name().as_string();
if (!exact_match) {
dbgln("Request and response questions do not match");
dbgln(" Request: name=_{}_, type={}, class={}", request_question.name().as_string(), response_question.record_type(), response_question.class_code());
dbgln(" Response: name=_{}_, type={}, class={}", response_question.name().as_string(), response_question.record_type(), response_question.class_code());
return {};
}
}
if (response.answer_count() < 1) {
dbgln("LookupServer: No answers :(");
return {};
}
Vector<DNSAnswer, 8> answers;
for (auto& answer : response.answers()) {
put_in_cache(answer);
if (answer.type() != record_type)
continue;
answers.append(answer);
}
return move(answers);
}
void LookupServer::put_in_cache(const DNSAnswer& answer)
{
if (answer.has_expired())
return;
// Prevent the cache from growing too big.
// TODO: Evict least used entries.
if (m_lookup_cache.size() >= 256)
m_lookup_cache.remove(m_lookup_cache.begin());
auto it = m_lookup_cache.find(answer.name());
if (it == m_lookup_cache.end())
m_lookup_cache.set(answer.name(), { answer });
else
it->value.append(answer);
}
}