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90 lines
3.0 KiB
Rust
90 lines
3.0 KiB
Rust
use crate::*;
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use byteorder::{BigEndian, ByteOrder};
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use failure::ensure;
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use std::net::{IpAddr, Ipv6Addr, SocketAddr};
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use std::sync::Arc;
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use tokio::net::UdpSocket;
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pub const ANONYMIZED_DNSCRYPT_QUERY_MAGIC: [u8; 10] =
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[0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x00];
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pub const ANONYMIZED_DNSCRYPT_OVERHEAD: usize = 16 + 2;
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pub async fn handle_anonymized_dns(
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globals: Arc<Globals>,
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client_ctx: ClientCtx,
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encrypted_packet: &[u8],
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) -> Result<(), Error> {
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ensure!(
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encrypted_packet.len() > ANONYMIZED_DNSCRYPT_OVERHEAD,
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"Short packet"
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);
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let ip_bin = &encrypted_packet[..16];
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let ip_v6 = Ipv6Addr::new(
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BigEndian::read_u16(&ip_bin[0..2]),
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BigEndian::read_u16(&ip_bin[2..4]),
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BigEndian::read_u16(&ip_bin[4..6]),
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BigEndian::read_u16(&ip_bin[6..8]),
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BigEndian::read_u16(&ip_bin[8..10]),
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BigEndian::read_u16(&ip_bin[10..12]),
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BigEndian::read_u16(&ip_bin[12..14]),
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BigEndian::read_u16(&ip_bin[14..16]),
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);
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let ip = match ip_v6.to_ipv4() {
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Some(ip_v4) => IpAddr::V4(ip_v4),
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None => IpAddr::V6(ip_v6),
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};
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#[cfg(feature = "metrics")]
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globals.varz.anonymized_queries.inc();
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ensure!(ip.is_global(), "Forbidden upstream address");
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ensure!(
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!globals.anonymized_dns_blacklisted_ips.contains(&ip),
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"Blacklisted upstream IP"
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);
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let port = BigEndian::read_u16(&encrypted_packet[16..18]);
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ensure!(
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globals.anonymized_dns_allowed_ports.contains(&port),
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"Forbidden upstream port"
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);
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let upstream_address = SocketAddr::new(ip, port);
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ensure!(
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!globals.listen_addrs.contains(&upstream_address)
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&& globals.external_addr != upstream_address,
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"Would be relaying to self"
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);
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let encrypted_packet = &encrypted_packet[ANONYMIZED_DNSCRYPT_OVERHEAD..];
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let encrypted_packet_len = encrypted_packet.len();
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ensure!(
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encrypted_packet_len >= DNSCRYPT_UDP_QUERY_MIN_SIZE
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&& encrypted_packet_len <= DNSCRYPT_UDP_QUERY_MAX_SIZE,
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"Unexpected encapsulated query length"
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);
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ensure!(
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encrypted_packet_len > 8 && [0u8, 0, 0, 0, 0, 0, 0, 1] != encrypted_packet[..8],
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"Protocol confusion with QUIC"
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);
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let mut ext_socket = UdpSocket::bind(&globals.external_addr).await?;
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ext_socket.connect(&upstream_address).await?;
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ext_socket.send(&encrypted_packet).await?;
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let mut response = vec![0u8; DNSCRYPT_UDP_RESPONSE_MAX_SIZE];
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loop {
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let fut = ext_socket.recv_from(&mut response[..]);
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let (response_len, response_addr) = fut.await?;
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if response_addr == upstream_address
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&& (DNSCRYPT_UDP_RESPONSE_MIN_SIZE..=DNSCRYPT_UDP_RESPONSE_MAX_SIZE)
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.contains(&response_len)
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&& response[..DNSCRYPT_RESPONSE_MAGIC_SIZE] == DNSCRYPT_RESPONSE_MAGIC
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{
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response.truncate(response_len);
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break;
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}
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}
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#[cfg(feature = "metrics")]
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globals.varz.anonymized_responses.inc();
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respond_to_query(client_ctx, response).await
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}
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