1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
|
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Sergey Bugaev <bugaevc@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 "DNSPacket.h"
#include "DNSPacketHeader.h"
#include <AK/IPv4Address.h>
#include <AK/MemoryStream.h>
#include <AK/StringBuilder.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <stdlib.h>
namespace LookupServer {
void DNSPacket::add_question(const String& name, u16 record_type, ShouldRandomizeCase should_randomize_case)
{
ASSERT(m_questions.size() <= UINT16_MAX);
if (name.is_empty())
return;
StringBuilder builder;
for (size_t i = 0; i < name.length(); ++i) {
u8 ch = name[i];
if (should_randomize_case == ShouldRandomizeCase::Yes) {
// Randomize the 0x20 bit in every ASCII character.
if (isalpha(ch)) {
if (arc4random_uniform(2))
ch |= 0x20;
else
ch &= ~0x20;
}
}
builder.append(ch);
}
m_questions.empend(builder.to_string(), record_type, (u16)C_IN);
}
ByteBuffer DNSPacket::to_byte_buffer() const
{
DNSPacketHeader header;
header.set_id(m_id);
if (is_query())
header.set_is_query();
else
header.set_is_response();
// FIXME: What should this be?
header.set_opcode(0);
header.set_truncated(false); // hopefully...
header.set_recursion_desired(true);
// FIXME: what should the be for requests?
header.set_recursion_available(true);
header.set_question_count(m_questions.size());
header.set_answer_count(m_answers.size());
DuplexMemoryStream stream;
stream << ReadonlyBytes { &header, sizeof(header) };
for (auto& question : m_questions) {
auto parts = question.name().as_string().split('.');
for (auto& part : parts) {
stream << (u8)part.length();
stream << part.bytes();
}
stream << '\0';
stream << htons(question.record_type());
stream << htons(question.class_code());
}
for (auto& answer : m_answers) {
auto parts = answer.name().as_string().split('.');
for (auto& part : parts) {
stream << (u8)part.length();
stream << part.bytes();
}
stream << '\0';
stream << htons(answer.type());
stream << htons(answer.class_code());
stream << htonl(answer.ttl());
stream << htons(answer.record_data().length());
stream << answer.record_data().bytes();
}
return stream.copy_into_contiguous_buffer();
}
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<DNSPacket> DNSPacket::from_raw_packet(const u8* raw_data, size_t raw_size)
{
if (raw_size < sizeof(DNSPacketHeader)) {
dbgln("DNS response not large enough ({} out of {}) to be a DNS packet.", raw_size, sizeof(DNSPacketHeader));
return {};
}
auto& header = *(const DNSPacketHeader*)(raw_data);
#ifdef LOOKUPSERVER_DEBUG
dbgln("Got packet (ID: {})", header.id());
dbgln(" Question count: {}", header.question_count());
dbgln(" Answer count: {}", header.answer_count());
dbgln(" Authority count: {}", header.authority_count());
dbgln("Additional count: {}", header.additional_count());
#endif
DNSPacket packet;
packet.m_id = header.id();
packet.m_query_or_response = header.is_response();
packet.m_code = header.response_code();
// FIXME: Should we parse further in this case?
if (packet.code() != Code::NOERROR)
return packet;
size_t offset = sizeof(DNSPacketHeader);
for (u16 i = 0; i < 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];
packet.m_questions.empend(name, record_and_class.record_type, record_and_class.class_code);
offset += 4;
#ifdef LOOKUPSERVER_DEBUG
auto& question = packet.m_questions.last();
dbgln("Question #{}: name=_{}_, type={}, class={}", i, question.name(), question.record_type(), question.class_code());
#endif
}
for (u16 i = 0; i < 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) {
data = { record.data(), record.data_length() };
} else {
// FIXME: Parse some other record types perhaps?
dbgln("data=(unimplemented record type {})", record.type());
}
#ifdef LOOKUPSERVER_DEBUG
dbgln("Answer #{}: name=_{}_, type={}, ttl={}, length={}, data=_{}_", i, name, record.type(), record.ttl(), record.data_length(), data);
#endif
packet.m_answers.empend(name, record.type(), record.record_class(), record.ttl(), data);
offset += record.data_length();
}
return packet;
}
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);
}
}
|
