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
|
/*
* This file is part of PowerDNS or dnsdist.
* Copyright -- PowerDNS.COM B.V. and its contributors
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of version 2 of the GNU General Public License as
* published by the Free Software Foundation.
*
* In addition, for the avoidance of any doubt, permission is granted to
* link this program with OpenSSL and to (re)distribute the binaries
* produced as the result of such linking.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "config.h"
#include "ednscookies.hh"
#include "dns_random.hh"
#include "iputils.hh"
#ifdef HAVE_CRYPTO_SHORTHASH
#include <sodium.h>
#endif
EDNSCookiesOpt::EDNSCookiesOpt(const std::string& option)
{
getEDNSCookiesOptFromString(option.c_str(), option.length());
}
EDNSCookiesOpt::EDNSCookiesOpt(const char* option, unsigned int len)
{
getEDNSCookiesOptFromString(option, len);
}
bool EDNSCookiesOpt::makeFromString(const std::string& option)
{
getEDNSCookiesOptFromString(option.c_str(), option.length());
return isWellFormed();
}
bool EDNSCookiesOpt::makeFromString(const char* option, unsigned int len)
{
getEDNSCookiesOptFromString(option, len);
return isWellFormed();
}
string EDNSCookiesOpt::makeOptString() const
{
string ret;
if (!isWellFormed()) {
return ret;
}
ret.assign(client);
if (server.length() != 0) {
ret.append(server);
}
return ret;
}
void EDNSCookiesOpt::getEDNSCookiesOptFromString(const char* option, unsigned int len)
{
client.clear();
server.clear();
if (len < 8) {
return;
}
const std::string tmp(option, len);
client = tmp.substr(0, 8);
if (len > 8) {
server = tmp.substr(8);
}
}
bool EDNSCookiesOpt::isValid([[maybe_unused]] const string& secret, [[maybe_unused]] const ComboAddress& source) const
{
#ifdef HAVE_CRYPTO_SHORTHASH
if (server.length() != 16 || client.length() != 8) {
return false;
}
if (server[0] != '\x01') {
// Version is not 1, can't verify
return false;
}
uint32_t timestamp{};
memcpy(×tamp, &server[4], sizeof(timestamp));
timestamp = ntohl(timestamp);
// coverity[store_truncates_time_t]
auto now = static_cast<uint32_t>(time(nullptr));
// RFC 9018 section 4.3:
// The DNS server
// SHOULD allow cookies within a 1-hour period in the past and a
// 5-minute period into the future
if (rfc1982LessThan(now + 300, timestamp) && rfc1982LessThan(timestamp + 3600, now)) {
return false;
}
if (secret.length() != crypto_shorthash_KEYBYTES) {
return false;
}
string toHash = client + server.substr(0, 8) + source.toByteString();
string hashResult;
hashResult.resize(8);
// NOLINTBEGIN(cppcoreguidelines-pro-type-reinterpret-cast)
crypto_shorthash(reinterpret_cast<unsigned char*>(hashResult.data()),
reinterpret_cast<const unsigned char*>(toHash.data()),
toHash.length(),
reinterpret_cast<const unsigned char*>(secret.data()));
// NOLINTEND(cppcoreguidelines-pro-type-reinterpret-cast)
return constantTimeStringEquals(server.substr(8), hashResult);
#else
return false;
#endif
}
bool EDNSCookiesOpt::shouldRefresh() const
{
if (server.size() < 16) {
return true;
}
uint32_t timestamp{};
memcpy(×tamp, &server.at(4), sizeof(timestamp));
timestamp = ntohl(timestamp);
// coverity[store_truncates_time_t]
auto now = static_cast<uint32_t>(time(nullptr));
// RFC 9018 section 4.3:
// The DNS server
// SHOULD allow cookies within a 1-hour period in the past and a
// 5-minute period into the future
// If this is not the case, we need to refresh
if (rfc1982LessThan(now + 300, timestamp) && rfc1982LessThan(timestamp + 3600, now)) {
return true;
}
// RFC 9018 section 4.3:
// The DNS server SHOULD generate a new Server Cookie at least if the
// received Server Cookie from the client is more than half an hour old
return rfc1982LessThan(timestamp + 1800, now);
}
void EDNSCookiesOpt::makeClientCookie()
{
const size_t clientCookieSize = 8;
client.resize(clientCookieSize);
dns_random(client.data(), clientCookieSize);
}
bool EDNSCookiesOpt::makeServerCookie([[maybe_unused]] const string& secret, [[maybe_unused]] const ComboAddress& source)
{
#ifdef HAVE_CRYPTO_SHORTHASH
static_assert(EDNSCookieSecretSize == crypto_shorthash_KEYBYTES * static_cast<size_t>(2), "The EDNSCookieSecretSize is not twice crypto_shorthash_KEYBYTES");
if (isValid(secret, source) && !shouldRefresh()) {
return true;
}
if (secret.length() != crypto_shorthash_KEYBYTES) {
return false;
}
server.clear();
server.reserve(16);
server = "\x01"; // Version
server.resize(4, '\0'); // 3 reserved bytes
// coverity[store_truncates_time_t]
uint32_t now = htonl(static_cast<uint32_t>(time(nullptr)));
// NOLINTBEGIN(cppcoreguidelines-pro-type-reinterpret-cast)
server += string(reinterpret_cast<const char*>(&now), sizeof(now));
server.resize(8);
string toHash = client;
toHash += server;
toHash += source.toByteString();
server.resize(16);
crypto_shorthash(reinterpret_cast<unsigned char*>(&server.at(8)),
reinterpret_cast<const unsigned char*>(toHash.data()),
toHash.length(),
reinterpret_cast<const unsigned char*>(secret.data()));
// NOLINTEND(cppcoreguidelines-pro-type-reinterpret-cast)
return true;
#else
return false;
#endif
}
|
