From: Arthur Chan <arthur.chan@adalogics.com>
Date: Wed, 17 Jun 2026 17:47:54 +0000 (+0100)
Subject: OSS-Fuzz: Add fuzzer targets dnsdist logic
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=0aa2b907d7b6b7c72cf778960bdbdd3df67fbb48;p=thirdparty%2Fpdns.git

OSS-Fuzz: Add fuzzer targets dnsdist logic

Signed-off-by: Arthur Chan <arthur.chan@adalogics.com>
---

diff --git a/pdns/dnsdistdist/fuzz_dnsdist_ecs.cc b/pdns/dnsdistdist/fuzz_dnsdist_ecs.cc
new file mode 100644
index 0000000000..3521a7cfe8
--- /dev/null
+++ b/pdns/dnsdistdist/fuzz_dnsdist_ecs.cc
@@ -0,0 +1,100 @@
+/*
+ * 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 <limits>
+
+#include "dnsdist-ecs.hh"
+#include "dnsname.hh"
+#include "dns.hh"
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size);
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
+{
+  if (size > std::numeric_limits<uint16_t>::max()) {
+    return 0;
+  }
+
+  const PacketBuffer packet(data, data + size);
+
+  // Wire-format EDNS/OPT parsing on the raw packet.
+  try {
+    EDNS0Record edns0{};
+    getEDNS0Record(packet, edns0);
+  }
+  catch (...) {
+  }
+
+  try {
+    uint16_t optStart = 0;
+    size_t optLen = 0;
+    bool last = false;
+    if (locateEDNSOptRR(packet, &optStart, &optLen, &last) == 0) {
+      size_t optContentStart = 0;
+      uint16_t optContentLen = 0;
+      isEDNSOptionInOpt(packet, optStart, optLen, EDNSOptionCode::ECS,
+                        &optContentStart, &optContentLen);
+    }
+  }
+  catch (...) {
+  }
+
+  try {
+    PacketBuffer newContent;
+    rewriteResponseWithoutEDNS(packet, newContent);
+  }
+  catch (...) {
+  }
+
+  try {
+    PacketBuffer newContent;
+    rewriteResponseWithoutEDNSOption(packet, EDNSOptionCode::ECS, newContent);
+  }
+  catch (...) {
+  }
+
+  // ECS add/replace; needs the question name's wire length.
+  try {
+    uint16_t qtype = 0;
+    uint16_t qclass = 0;
+    unsigned int consumed = 0;
+    const DNSName qname(reinterpret_cast<const char*>(data), size,
+                        sizeof(dnsheader), false, &qtype, &qclass, &consumed);
+
+    uint16_t optRDPosition = 0;
+    size_t remaining = 0;
+    dnsdist::getEDNSOptionsStart(packet, consumed, &optRDPosition, &remaining);
+
+    PacketBuffer mutablePacket(packet);
+    bool ednsAdded = false;
+    bool ecsAdded = false;
+    std::string newECSOption;
+    const ComboAddress source("192.0.2.1");
+    generateECSOption(source, newECSOption, 24);
+    handleEDNSClientSubnet(mutablePacket, mutablePacket.size() + 512, consumed,
+                           ednsAdded, ecsAdded, true, newECSOption);
+  }
+  catch (...) {
+  }
+
+  return 0;
+}
diff --git a/pdns/dnsdistdist/meson.build b/pdns/dnsdistdist/meson.build
index 82cec6f472..775fdfcea0 100644
--- a/pdns/dnsdistdist/meson.build
+++ b/pdns/dnsdistdist/meson.build
@@ -508,6 +508,15 @@ if get_option('fuzz-targets')
        ],
       'fuzzing-target': true,
     },
+    'fuzz-target-dnsdist-ecs' : {
+      'main': src_dir / 'fuzz_dnsdist_ecs.cc',
+      'link-args': fuzzer_ldflags,
+      'files-extra': fuzz_extra_sources,
+      'deps-extra': [
+         dep_libsystemd,
+       ],
+      'fuzzing-target': true,
+    },
   }
   if get_option('xsk').allowed() and dep_libbpf.found() and dep_libxdp.found()
     tools += {