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/*
* Copyright (c) 2018-2020, 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 "DNSResponse.h"
#include "DNSPacket.h"
#include "DNSRequest.h"
#include <AK/IPv4Address.h>
#include <AK/StringBuilder.h>
static String parse_dns_name(const u8* data, size_t& offset, size_t max_offset, size_t recursion_level = 0);
class [[gnu::packed]] DNSRecordWithoutName
{
public:
DNSRecordWithoutName() {}
u16 type() const { return m_type; }
u16 record_class() const { return m_class; }
u32 ttl() const { return m_ttl; }
u16 data_length() const { return m_data_length; }
void* data() { return this + 1; }
const void* data() const { return this + 1; }
private:
NetworkOrdered<u16> m_type;
NetworkOrdered<u16> m_class;
NetworkOrdered<u32> m_ttl;
NetworkOrdered<u16> m_data_length;
};
static_assert(sizeof(DNSRecordWithoutName) == 10);
Optional<DNSResponse> DNSResponse::from_raw_response(const u8* raw_data, size_t raw_size)
{
if (raw_size < sizeof(DNSPacket)) {
dbg() << "DNS response not large enough (" << raw_size << " out of " << sizeof(DNSPacket) << ") to be a DNS packet.";
return {};
}
auto& response_header = *(const DNSPacket*)(raw_data);
dbgprintf("Got response (ID: %u)\n", response_header.id());
dbgprintf(" Question count: %u\n", response_header.question_count());
dbgprintf(" Answer count: %u\n", response_header.answer_count());
dbgprintf(" Authority count: %u\n", response_header.authority_count());
dbgprintf("Additional count: %u\n", response_header.additional_count());
DNSResponse response;
response.m_id = response_header.id();
response.m_code = response_header.response_code();
if (response.code() != DNSResponse::Code::NOERROR)
return response;
size_t offset = sizeof(DNSPacket);
for (u16 i = 0; i < response_header.question_count(); ++i) {
auto name = parse_dns_name(raw_data, offset, raw_size);
struct RawDNSAnswerQuestion {
NetworkOrdered<u16> record_type;
NetworkOrdered<u16> class_code;
};
auto& record_and_class = *(const RawDNSAnswerQuestion*)&raw_data[offset];
response.m_questions.empend(name, record_and_class.record_type, record_and_class.class_code);
auto& question = response.m_questions.last();
offset += 4;
dbg() << "Question #" << i << ": _" << question.name() << "_ type: " << question.record_type() << ", class: " << question.class_code();
}
for (u16 i = 0; i < response_header.answer_count(); ++i) {
auto name = parse_dns_name(raw_data, offset, raw_size);
auto& record = *(const DNSRecordWithoutName*)(&raw_data[offset]);
String data;
offset += sizeof(DNSRecordWithoutName);
if (record.type() == T_PTR) {
size_t dummy_offset = offset;
data = parse_dns_name(raw_data, dummy_offset, raw_size);
} else if (record.type() == T_A) {
auto ipv4_address = IPv4Address((const u8*)record.data());
data = ipv4_address.to_string();
} else {
// FIXME: Parse some other record types perhaps?
dbg() << " data=(unimplemented record type " << record.type() << ")";
}
dbg() << "Answer #" << i << ": name=_" << name << "_, type=" << record.type() << ", ttl=" << record.ttl() << ", length=" << record.data_length() << ", data=_" << data << "_";
response.m_answers.empend(name, record.type(), record.record_class(), record.ttl(), data);
offset += record.data_length();
}
return response;
}
String parse_dns_name(const u8* data, size_t& offset, size_t max_offset, size_t recursion_level)
{
if (recursion_level > 4)
return {};
Vector<char, 128> buf;
while (offset < max_offset) {
u8 ch = data[offset];
if (ch == '\0') {
++offset;
break;
}
if ((ch & 0xc0) == 0xc0) {
if ((offset + 1) >= max_offset)
return {};
size_t dummy = (ch & 0x3f) << 8 | data[offset + 1];
offset += 2;
StringBuilder builder;
builder.append(buf.data(), buf.size());
auto okay = parse_dns_name(data, dummy, max_offset, recursion_level + 1);
builder.append(okay);
return builder.to_string();
}
for (size_t i = 0; i < ch; ++i)
buf.append(data[offset + i + 1]);
buf.append('.');
offset += ch + 1;
}
return String::copy(buf);
}
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