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Truncate inbound Peers response further #3007

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merged 2 commits into from
Nov 2, 2021
Merged

Truncate inbound Peers response further #3007

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7f80f62
truncate `Peers` response further
oxarbitrage Nov 2, 2021
07f0367
Merge branch 'main' into issue1889
oxarbitrage Nov 2, 2021
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21 changes: 15 additions & 6 deletions zebrad/src/components/inbound.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,13 @@ type InboundBlockDownloads = BlockDownloads<Timeout<Outbound>, Timeout<BlockVeri

pub type NetworkSetupData = (Outbound, Arc<std::sync::Mutex<AddressBook>>, Mempool);

/// A bitcoin protocol constant that will hold the max number of peers
/// we can return in response to a `Peers` request.
const MAX_ADDR: usize = 1000; // bitcoin protocol constant
/// A security parameter to return only 1/3 of available addresses as a
/// response to a `Peers` request.
const FRAC_OF_AVAILABLE_ADDRESS: f64 = 1. / 3.;

/// Tracks the internal state of the [`Inbound`] service during network setup.
pub enum Setup {
/// Waiting for network setup to complete.
Expand Down Expand Up @@ -248,10 +255,9 @@ impl Service<zn::Request> for Inbound {
if let Setup::Initialized { address_book, .. } = &self.network_setup {
// # Security
//
// We could truncate the list to try to not reveal our entire
// peer set. But because we don't monitor repeated requests,
// this wouldn't actually achieve anything, because a crawler
// could just repeatedly query it.
// We truncate the list to not reveal our entire peer set in one call.
// But we don't monitor repeated requests and the results are shuffled,
// a crawler could just send repeated queries and get the full list.
//
// # Correctness
//
Expand All @@ -262,8 +268,11 @@ impl Service<zn::Request> for Inbound {

// Send a sanitized response
let mut peers = peers.sanitized();
const MAX_ADDR: usize = 1000; // bitcoin protocol constant
peers.truncate(MAX_ADDR);

// Truncate the list
let truncate_at = MAX_ADDR
.min((peers.len() as f64 * FRAC_OF_AVAILABLE_ADDRESS).ceil() as usize);
peers.truncate(truncate_at);

if !peers.is_empty() {
async { Ok(zn::Response::Peers(peers)) }.boxed()
Expand Down