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udp: optimize/simplify ConnectionValidator

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This commit is contained in:
Joakim Frostegård 2022-04-13 23:40:04 +02:00
parent 059ef495bf
commit 4203e86eca
1 changed files with 19 additions and 25 deletions
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44
aquatic_udp/src/common.rs
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@ -3,7 +3,7 @@ use std::hash::Hash;
use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
use std::sync::atomic::AtomicUsize;
use std::sync::Arc;
use std::time::{Duration, Instant};
use std::time::Instant;
use crossbeam_channel::{Sender, TrySendError};
use getrandom::getrandom;
@ -19,7 +19,7 @@ pub const MAX_PACKET_SIZE: usize = 8192;
#[derive(Clone)]
pub struct ConnectionValidator {
start_time: Instant,
max_connection_age: Duration,
max_connection_age: u32,
hmac: blake3::Hasher,
}
@ -31,21 +31,18 @@ impl ConnectionValidator {
let hmac = blake3::Hasher::new_keyed(&key);
let start_time = Instant::now();
let max_connection_age = Duration::from_secs(config.cleaning.max_connection_age);
Ok(Self {
hmac,
start_time,
max_connection_age,
start_time: Instant::now(),
max_connection_age: config.cleaning.max_connection_age as u32,
})
}
pub fn create_connection_id(&mut self, source_addr: CanonicalSocketAddr) -> ConnectionId {
// Seconds elapsed since server start, as bytes
let elapsed_time_bytes = (self.start_time.elapsed().as_secs() as u32).to_ne_bytes();
let valid_until =
(self.start_time.elapsed().as_secs() as u32 + self.max_connection_age).to_ne_bytes();
self.create_connection_id_inner(elapsed_time_bytes, source_addr)
self.create_connection_id_inner(valid_until, source_addr)
}
pub fn connection_id_valid(
@ -53,34 +50,31 @@ impl ConnectionValidator {
source_addr: CanonicalSocketAddr,
connection_id: ConnectionId,
) -> bool {
let elapsed_time_bytes = connection_id.0.to_ne_bytes()[..4].try_into().unwrap();
let valid_until = connection_id.0.to_ne_bytes()[..4].try_into().unwrap();
// i64 comparison should be constant-time
let hmac_valid =
connection_id == self.create_connection_id_inner(elapsed_time_bytes, source_addr);
if !hmac_valid {
// Check that recreating ConnectionId with same inputs yields identical HMAC.
//
// I expect i64 comparison to be be constant-time.
if connection_id != self.create_connection_id_inner(valid_until, source_addr) {
return false;
}
let connection_elapsed_since_start =
Duration::from_secs(u32::from_ne_bytes(elapsed_time_bytes) as u64);
connection_elapsed_since_start + self.max_connection_age > self.start_time.elapsed()
u32::from_ne_bytes(valid_until) > self.start_time.elapsed().as_secs() as u32
}
fn create_connection_id_inner(
&mut self,
elapsed_time_bytes: [u8; 4],
valid_until: [u8; 4],
source_addr: CanonicalSocketAddr,
) -> ConnectionId {
// The first 4 bytes is the elapsed time since server start in seconds. The last 4 is a
// truncated message authentication code.
// The first 4 bytes is number of seconds since server start until
// connection is no longer valid. The last 4 is the truncated message
// authentication code.
let mut connection_id_bytes = [0u8; 8];
(&mut connection_id_bytes[..4]).copy_from_slice(&elapsed_time_bytes);
(&mut connection_id_bytes[..4]).copy_from_slice(&valid_until);
self.hmac.update(&elapsed_time_bytes);
self.hmac.update(&valid_until);
match source_addr.get().ip() {
IpAddr::V4(ip) => self.hmac.update(&ip.octets()),