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
|
/*
* 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 "dnsdist-dnsparser.hh"
#include "dnsparser.hh"
namespace dnsdist
{
DNSPacketOverlay::DNSPacketOverlay(const std::string_view& packet)
{
if (packet.size() < sizeof(dnsheader)) {
throw std::runtime_error("Packet is too small for a DNS packet");
}
memcpy(&d_header, packet.data(), sizeof(dnsheader));
uint64_t numRecords = ntohs(d_header.ancount) + ntohs(d_header.nscount) + ntohs(d_header.arcount);
d_records.reserve(numRecords);
try {
PacketReader reader(std::string_view(reinterpret_cast<const char*>(packet.data()), packet.size()));
for (uint16_t n = 0; n < ntohs(d_header.qdcount); ++n) {
reader.xfrName(d_qname);
reader.xfrType(d_qtype);
reader.xfrType(d_qclass);
}
for (uint64_t n = 0; n < numRecords; ++n) {
Record rec;
reader.xfrName(rec.d_name);
rec.d_place = n < ntohs(d_header.ancount) ? DNSResourceRecord::ANSWER : (n < (ntohs(d_header.ancount) + ntohs(d_header.nscount)) ? DNSResourceRecord::AUTHORITY : DNSResourceRecord::ADDITIONAL);
reader.xfrType(rec.d_type);
reader.xfrType(rec.d_class);
reader.xfr32BitInt(rec.d_ttl);
reader.xfr16BitInt(rec.d_contentLength);
rec.d_contentOffset = reader.getPosition();
reader.skip(rec.d_contentLength);
d_records.push_back(std::move(rec));
}
}
catch (const std::exception& e) {
throw std::runtime_error("Unable to parse DNS packet: " + std::string(e.what()));
}
catch (...) {
throw std::runtime_error("Unable to parse DNS packet");
}
}
bool changeNameInDNSPacket(PacketBuffer& initialPacket, const DNSName& from, const DNSName& to)
{
if (initialPacket.size() < sizeof(dnsheader)) {
return false;
}
PacketReader pr(std::string_view(reinterpret_cast<const char*>(initialPacket.data()), initialPacket.size()));
dnsheader dh;
memcpy(&dh, initialPacket.data(), sizeof(dh));
size_t idx = 0;
DNSName rrname;
uint16_t qdcount = ntohs(dh.qdcount);
uint16_t ancount = ntohs(dh.ancount);
uint16_t nscount = ntohs(dh.nscount);
uint16_t arcount = ntohs(dh.arcount);
uint16_t rrtype;
uint16_t rrclass;
string blob;
size_t recordsCount = ancount + nscount + arcount;
struct dnsrecordheader ah;
rrname = pr.getName();
if (rrname == from) {
rrname = to;
}
rrtype = pr.get16BitInt();
rrclass = pr.get16BitInt();
PacketBuffer newContent;
newContent.reserve(initialPacket.size());
GenericDNSPacketWriter<PacketBuffer> pw(newContent, rrname, rrtype, rrclass, dh.opcode);
/* we want to copy the flags and ID but not the counts since we recreate the records below */
pw.getHeader()->id = dh.id;
pw.getHeader()->qr = dh.qr;
pw.getHeader()->aa = dh.aa;
pw.getHeader()->tc = dh.tc;
pw.getHeader()->rd = dh.rd;
pw.getHeader()->ra = dh.ra;
pw.getHeader()->ad = dh.ad;
pw.getHeader()->cd = dh.cd;
pw.getHeader()->rcode = dh.rcode;
/* consume remaining qd if any, but do not copy it */
for (idx = 1; idx < qdcount; idx++) {
rrname = pr.getName();
(void)pr.get16BitInt();
(void)pr.get16BitInt();
}
static const std::unordered_set<QType> nameOnlyTypes{QType::NS, QType::PTR, QType::CNAME, QType::DNAME};
static const std::unordered_set<QType> noNameTypes{QType::A, QType::AAAA, QType::DHCID, QType::TXT, QType::OPT, QType::HINFO, QType::DNSKEY, QType::CDNSKEY, QType::DS, QType::CDS, QType::DLV, QType::SSHFP, QType::KEY, QType::CERT, QType::TLSA, QType::SMIMEA, QType::OPENPGPKEY, QType::NSEC, QType::NSEC3, QType::CSYNC, QType::NSEC3PARAM, QType::LOC, QType::NID, QType::L32, QType::L64, QType::EUI48, QType::EUI64, QType::URI, QType::CAA};
/* copy AN, NS and AR */
for (idx = 0; idx < recordsCount; idx++) {
rrname = pr.getName();
if (rrname == from) {
rrname = to;
}
pr.getDnsrecordheader(ah);
auto place = idx < ancount ? DNSResourceRecord::ANSWER : (idx < (ancount + nscount) ? DNSResourceRecord::AUTHORITY : DNSResourceRecord::ADDITIONAL);
pw.startRecord(rrname, ah.d_type, ah.d_ttl, ah.d_class, place, true);
if (nameOnlyTypes.count(ah.d_type)) {
rrname = pr.getName();
pw.xfrName(rrname);
}
else if (noNameTypes.count(ah.d_type)) {
pr.xfrBlob(blob);
pw.xfrBlob(blob);
}
else if (ah.d_type == QType::RRSIG) {
/* good luck */
pr.xfrBlob(blob);
pw.xfrBlob(blob);
}
else if (ah.d_type == QType::MX) {
auto prio = pr.get16BitInt();
rrname = pr.getName();
pw.xfr16BitInt(prio);
pw.xfrName(rrname);
}
else if (ah.d_type == QType::SOA) {
auto mname = pr.getName();
pw.xfrName(mname);
auto rname = pr.getName();
pw.xfrName(rname);
/* serial */
pw.xfr32BitInt(pr.get32BitInt());
/* refresh */
pw.xfr32BitInt(pr.get32BitInt());
/* retry */
pw.xfr32BitInt(pr.get32BitInt());
/* expire */
pw.xfr32BitInt(pr.get32BitInt());
/* minimal */
pw.xfr32BitInt(pr.get32BitInt());
}
else if (ah.d_type == QType::SRV) {
/* preference */
pw.xfr16BitInt(pr.get16BitInt());
/* weight */
pw.xfr16BitInt(pr.get16BitInt());
/* port */
pw.xfr16BitInt(pr.get16BitInt());
auto target = pr.getName();
pw.xfrName(target);
}
else {
/* sorry, unsafe type */
return false;
}
}
pw.commit();
initialPacket = std::move(newContent);
return true;
}
}
|
