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LibDNS: Make DNS packet parsing fallible

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Previously, a DNS packet containing an invalid name would be returned
with an empty name. With this change, an error is returned if any error
is encountered during parsing.
This commit is contained in:
Tim Ledbetter 2023-11-13 22:36:34 +00:00 • committed by Andreas Kling
parent 95d62822bf
commit 1793f51bc6
8 changed files with 29 additions and 40 deletions
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18
Userland/Libraries/LibDNS/Packet.cpp
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@ -97,11 +97,11 @@ private:
static_assert(sizeof(DNSRecordWithoutName) == 10);
Optional<Packet> Packet::from_raw_packet(ReadonlyBytes bytes)
ErrorOr<Packet> Packet::from_raw_packet(ReadonlyBytes bytes)
{
if (bytes.size() < sizeof(PacketHeader)) {
dbgln("DNS response not large enough ({} out of {}) to be a DNS packet.", bytes.size(), sizeof(PacketHeader));
return {};
dbgln_if(LOOKUPSERVER_DEBUG, "DNS response not large enough ({} out of {}) to be a DNS packet", bytes.size(), sizeof(PacketHeader));
return Error::from_string_literal("DNS response not large enough to be a DNS packet");
}
auto const& header = *bit_cast<PacketHeader const*>(bytes.data());
@ -123,13 +123,13 @@ Optional<Packet> Packet::from_raw_packet(ReadonlyBytes bytes)
size_t offset = sizeof(PacketHeader);
for (u16 i = 0; i < header.question_count(); i++) {
auto name = Name::parse(bytes, offset);
auto name = TRY(Name::parse(bytes, offset));
struct RawDNSAnswerQuestion {
NetworkOrdered<u16> record_type;
NetworkOrdered<u16> class_code;
};
if (offset >= bytes.size() || bytes.size() - offset < sizeof(RawDNSAnswerQuestion))
return {};
return Error::from_string_literal("Unexpected EOF when parsing DNS packet");
auto const& record_and_class = *bit_cast<RawDNSAnswerQuestion const*>(bytes.offset_pointer(offset));
u16 class_code = record_and_class.class_code & ~MDNS_WANTS_UNICAST_RESPONSE;
@ -141,21 +141,21 @@ Optional<Packet> Packet::from_raw_packet(ReadonlyBytes bytes)
}
for (u16 i = 0; i < header.answer_count(); ++i) {
auto name = Name::parse(bytes, offset);
auto name = TRY(Name::parse(bytes, offset));
if (offset >= bytes.size() || bytes.size() - offset < sizeof(DNSRecordWithoutName))
return {};
return Error::from_string_literal("Unexpected EOF when parsing DNS packet");
auto const& record = *bit_cast<DNSRecordWithoutName const*>(bytes.offset_pointer(offset));
offset += sizeof(DNSRecordWithoutName);
if (record.data_length() > bytes.size() - offset)
return {};
return Error::from_string_literal("Unexpected EOF when parsing DNS packet");
DeprecatedString data;
switch ((RecordType)record.type()) {
case RecordType::PTR: {
size_t dummy_offset = offset;
data = Name::parse(bytes, dummy_offset).as_string();
data = TRY(Name::parse(bytes, dummy_offset)).as_string();
break;
}
case RecordType::CNAME: