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/*
* 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-ecs.hh"
#include "dnsdist-edns.hh"
#include "ednsoptions.hh"
#include "ednsextendederror.hh"
namespace dnsdist::edns
{
std::pair<std::optional<uint16_t>, std::optional<std::string>> getExtendedDNSError(const PacketBuffer& packet)
{
uint16_t optStart = 0;
size_t optLen = 0;
bool last = false;
int res = locateEDNSOptRR(packet, &optStart, &optLen, &last);
if (res != 0) {
return {std::nullopt, std::nullopt};
}
size_t optContentStart = 0;
uint16_t optContentLen = 0;
uint16_t infoCode{0};
std::optional<std::string> extraText{std::nullopt};
/* we need at least 2 bytes after the option length (info-code) */
if (!isEDNSOptionInOpt(packet, optStart, optLen, EDNSOptionCode::EXTENDEDERROR, &optContentStart, &optContentLen) || optContentLen < sizeof(infoCode)) {
return {std::nullopt, std::nullopt};
}
memcpy(&infoCode, &packet.at(optContentStart), sizeof(infoCode));
infoCode = ntohs(infoCode);
if (optContentLen > sizeof(infoCode)) {
extraText = std::string();
extraText->resize(optContentLen - sizeof(infoCode));
memcpy(extraText->data(), &packet.at(optContentStart + sizeof(infoCode)), optContentLen - sizeof(infoCode));
}
return {infoCode, std::move(extraText)};
}
bool addExtendedDNSError(PacketBuffer& packet, size_t maximumPacketSize, uint16_t code, const std::string& extraStatus)
{
uint16_t optStart = 0;
size_t optLen = 0;
bool last = false;
int res = locateEDNSOptRR(packet, &optStart, &optLen, &last);
if (res != 0) {
/* no EDNS OPT record in the response, something is not right */
return false;
}
EDNSExtendedError ede{.infoCode = code, .extraText = extraStatus};
auto edeOptionPayload = makeEDNSExtendedErrorOptString(ede);
std::string edeOption;
generateEDNSOption(EDNSOptionCode::EXTENDEDERROR, edeOptionPayload, edeOption);
/* we might have one record after the OPT one, we need to rewrite
the whole packet because of compression */
PacketBuffer newContent;
bool ednsAdded = false;
bool edeAdded = false;
if (!slowRewriteEDNSOptionInQueryWithRecords(packet, newContent, ednsAdded, EDNSOptionCode::EXTENDEDERROR, edeAdded, true, edeOption)) {
return false;
}
if (newContent.size() > maximumPacketSize) {
return false;
}
packet = std::move(newContent);
return true;
}
}
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