1 files changed, 94 insertions, 0 deletions
diff --git a/dnsdist-edns.cc b/dnsdist-edns.cc
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+++ b/dnsdist-edns.cc
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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;
+}
+}