fix(connlib): use correct constant for truncating DNS responses#7551
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thomaseizinger merged 7 commits intomainfrom Dec 19, 2024
Merged
fix(connlib): use correct constant for truncating DNS responses#7551thomaseizinger merged 7 commits intomainfrom
thomaseizinger merged 7 commits intomainfrom
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Sentry Issue: GUI-CLIENT-IPC-SERVICE-14 |
jamilbk
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Dec 18, 2024
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LGTM, just needs a typo fix I think
| use ip_network::{IpNetwork, Ipv4Network, Ipv6Network}; | ||
| use ip_network_table::IpNetworkTable; | ||
| use ip_packet::{IpPacket, UdpSlice, MAX_DATAGRAM_PAYLOAD}; | ||
| use ip_packet::{IpPacket, UdpSlice, MAX_UPD_PAYLOAD}; |
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| use ip_packet::{IpPacket, UdpSlice, MAX_UPD_PAYLOAD}; | |
| use ip_packet::{IpPacket, UdpSlice, MAX_UDP_PAYLOAD}; |
| tracing::debug!(?message, message_length = %message_bytes.len(), "Too big DNS response, truncating"); | ||
| fn truncate_dns_response(mut message: Message<Vec<u8>>) -> Vec<u8> { | ||
| let message_length = message.as_octets().len(); | ||
| if message_length <= MAX_UPD_PAYLOAD { |
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| if message_length <= MAX_UPD_PAYLOAD { | |
| if message_length <= MAX_UDP_PAYLOAD { |
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| message_bytes = new_message.as_octets().to_vec(); | ||
| let message_truncation = match message.answer() { | ||
| Ok(answer) if answer.pos() <= MAX_UPD_PAYLOAD => answer.pos(), |
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| Ok(answer) if answer.pos() <= MAX_UPD_PAYLOAD => answer.pos(), | |
| Ok(answer) if answer.pos() <= MAX_UDP_PAYLOAD => answer.pos(), |
| Message, MessageBuilder, Record, RecordData, ToName, Ttl, | ||
| }; | ||
| use ip_packet::{IpPacket, MAX_DATAGRAM_PAYLOAD}; | ||
| use ip_packet::{IpPacket, MAX_UPD_PAYLOAD}; |
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| use ip_packet::{IpPacket, MAX_UPD_PAYLOAD}; | |
| use ip_packet::{IpPacket, MAX_UDP_PAYLOAD}; |
| let mut message_bytes = message.as_octets().to_vec(); | ||
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| if message_bytes.len() > MAX_DATAGRAM_PAYLOAD { | ||
| if message_bytes.len() > MAX_UPD_PAYLOAD { |
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| if message_bytes.len() > MAX_UPD_PAYLOAD { | |
| if message_bytes.len() > MAX_UDP_PAYLOAD { |
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| let message_truncation = match message.answer() { | ||
| Ok(answer) if answer.pos() <= MAX_DATAGRAM_PAYLOAD => answer.pos(), | ||
| Ok(answer) if answer.pos() <= MAX_UPD_PAYLOAD => answer.pos(), |
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| Ok(answer) if answer.pos() <= MAX_UPD_PAYLOAD => answer.pos(), | |
| Ok(answer) if answer.pos() <= MAX_UDP_PAYLOAD => answer.pos(), |
| /// The max length of an IPv4 header is > the fixed length of an IPv6 header. | ||
| pub const MAX_IP_PAYLOAD: usize = MAX_IP_SIZE - etherparse::Ipv4Header::MAX_LEN; | ||
| /// The maximum payload a UDP packet can have. | ||
| pub const MAX_UPD_PAYLOAD: usize = MAX_IP_PAYLOAD - etherparse::UdpHeader::LEN; |
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| pub const MAX_UPD_PAYLOAD: usize = MAX_IP_PAYLOAD - etherparse::UdpHeader::LEN; | |
| pub const MAX_UDP_PAYLOAD: usize = MAX_IP_PAYLOAD - etherparse::UdpHeader::LEN; |
jamilbk
approved these changes
Dec 19, 2024
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Sentry Issue: GUI-CLIENT-IPC-SERVICE-2G |
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In case an upstream DNS server responds with a payload that exceeds the available buffer space of an IP packet, we need to truncate the response. Currently, this truncation uses the wrong constant to check for the maximum allowed length. Instead of the
MAX_DATAGRAM_PAYLOAD, we actually need to check against a limit that is less than the MTU as the IP layer and the UDP layer both add an overhead.To fix this, we introduce such a constant and provide additional documentation on the remaining ones to hopefully avoid future errors.