1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-07-25 21:27:35 +00:00

LookupServer: Verify that DNS response questions match the request

To protect against DNS spoof attacks, we now check that the questions
in incoming responses match the questions in the request we sent out.

Suggested by @zecke in #10.
This commit is contained in:
Andreas Kling 2020-01-26 13:06:00 +01:00
parent b4d55b16b6
commit 00be9b33b1
4 changed files with 26 additions and 3 deletions

View file

@ -16,6 +16,16 @@ public:
u16 class_code() const { return m_class_code; }
const String& name() const { return m_name; }
bool operator==(const DNSQuestion& other) const
{
return m_name == other.m_name && m_record_type == other.m_record_type && m_class_code == other.m_class_code;
}
bool operator!=(const DNSQuestion& other) const
{
return !(*this == other);
}
private:
String m_name;
u16 m_record_type { 0 };

View file

@ -18,6 +18,8 @@ public:
void add_question(const String& name, u16 record_type);
const Vector<DNSQuestion>& questions() const { return m_questions; }
u16 question_count() const
{
ASSERT(m_questions.size() < UINT16_MAX);

View file

@ -28,7 +28,6 @@ private:
static_assert(sizeof(DNSRecordWithoutName) == 10);
Optional<DNSResponse> DNSResponse::from_raw_response(const u8* raw_data, size_t raw_size)
{
if (raw_size < sizeof(DNSPacket)) {
@ -79,7 +78,7 @@ Optional<DNSResponse> DNSResponse::from_raw_response(const u8* raw_data, size_t
// FIXME: Parse some other record types perhaps?
dbg() << " data=(unimplemented record type " << record.type() << ")";
}
dbg() << "Answer #" << i << ": type=" << record.type() << ", ttl=" << record.ttl() << ", length=" << record.data_length() << ", data=_" << data << "_";
dbg() << "Answer #" << i << ": name=_" << name << "_, type=" << record.type() << ", ttl=" << record.ttl() << ", length=" << record.data_length() << ", data=_" << data << "_";
response.m_answers.empend(name, record.type(), record.record_class(), record.ttl(), data);
offset += record.data_length();
}

View file

@ -216,10 +216,22 @@ Vector<String> LookupServer::lookup(const String& hostname, bool& did_timeout, u
dbgprintf("LookupServer: ID mismatch (%u vs %u) :(\n", response.id(), request.id());
return {};
}
if (response.question_count() != 1) {
if (response.question_count() != request.question_count()) {
dbgprintf("LookupServer: Question count (%u vs %u) :(\n", response.question_count(), request.question_count());
return {};
}
for (size_t i = 0; i < request.question_count(); ++i) {
auto& request_question = request.questions()[i];
auto& response_question = response.questions()[i];
if (request_question != response_question) {
dbg() << "Request and response questions do not match";
dbg() << " Request: {_" << request_question.name() << "_, " << request_question.record_type() << ", " << request_question.class_code() << "}";
dbg() << " Response: {_" << response_question.name() << "_, " << response_question.record_type() << ", " << response_question.class_code() << "}";
return {};
}
}
if (response.answer_count() < 1) {
dbgprintf("LookupServer: Not enough answers (%u) :(\n", response.answer_count());
return {};