From 3cd01b932e1c85394272ae64fae67ebeda92fb00 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 13 Apr 2024 23:11:59 +0200 Subject: Adding upstream version 1.8.3. Signed-off-by: Daniel Baumann --- dnsdist-dnsparser.cc | 189 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 189 insertions(+) create mode 100644 dnsdist-dnsparser.cc (limited to 'dnsdist-dnsparser.cc') diff --git a/dnsdist-dnsparser.cc b/dnsdist-dnsparser.cc new file mode 100644 index 0000000..90ce075 --- /dev/null +++ b/dnsdist-dnsparser.cc @@ -0,0 +1,189 @@ +/* + * 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(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(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 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 nameOnlyTypes{QType::NS, QType::PTR, QType::CNAME, QType::DNAME}; + static const std::unordered_set 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; +} + +} -- cgit v1.2.3