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use std::borrow::Cow;use std::collections::BTreeSet;use std::net::SocketAddr;use std::path::Path;use std::sync::Arc;use std::time::Duration;
use knot_atproto::Atproto;use knot_git::{ArchiveLimit, Layout};use knot_index::{Index, KeyTtl};use knot_maintenance::MaintenanceHandle;use knot_pack::{MaxWireBytes, PackLimits};use knot_runtime::{Clock, Entropy, HttpTransport, OsEntropy};use knot_types::{ AccountDid, ActorId, AdmissionPolicy, AppviewEndpoint, CiLogsAddr, KnotHostname,};use russh::keys::ssh_key::rand_core;use russh::keys::{Algorithm, PrivateKey, ssh_key};use russh::server::{Config, Server as _};use russh::{MethodKind, MethodSet, Preferred, compression};use tokio::sync::Semaphore;use tokio_util::sync::CancellationToken;use tokio_util::task::TaskTracker;
use knot_resource::{ Burst, GlobalInflight, LimitConfig, PeerPacer, PerPeerInflight, PreAuthLimiter, RateLimit, RefillMicros, ResolveSlots, Slots, SubjectPacer,};use server::KnotSshServer;
const MAX_INFLIGHT_PER_PEER: usize = 4;const MAX_INFLIGHT_LOOKUPS: usize = 16;const MAX_PREAUTH_LOOKUPS: usize = 4;const LOOKUP_BURST_PER_PEER: u32 = 8;const LOOKUP_REFILL_MICROS: u64 = 500_000;const LOOKUP_INFLIGHT_PER_PEER: usize = 2;const PROBE_BURST_PER_ACCOUNT: u32 = 1;const PROBE_REFILL_MICROS: u64 = 30_000_000;const MISS_BURST_PER_PEER: u32 = 1;const MISS_REFILL_MICROS: u64 = 120_000_000;const INACTIVITY_TIMEOUT: Duration = Duration::from_secs(120);const KEEPALIVE_INTERVAL: Duration = Duration::from_secs(30);const AUTH_REJECTION_TIME: Duration = Duration::from_millis(250);const DRAIN_GRACE: Duration = Duration::from_secs(30);const ACCEPT_BACKOFF: Duration = Duration::from_millis(250);
#[derive(Debug, thiserror::Error)]pub enum SshError { #[error("ssh host key {path}: {message}")] HostKey { path: String, message: String }, #[error("ssh server bind or serve: {0}")] Serve(#[from] std::io::Error),}
pub struct SshState<H, C> { layout: Layout, index: Arc<Index>, atproto: Arc<Atproto<H, C>>, knot_actor: ActorId, hostname: KnotHostname, appview: AppviewEndpoint, admins: BTreeSet<AccountDid>, admission: AdmissionPolicy, limits: PackLimits, max_pack_bytes: MaxWireBytes, archive_limit: ArchiveLimit, ci_logs: Option<CiLogsAddr>, slots: Slots, lookup_slots: ResolveSlots, lookup_peers: Arc<PreAuthLimiter>, probe_pace: SubjectPacer, miss_pace: PeerPacer, key_ttl: KeyTtl, peer_slots: Arc<PreAuthLimiter>, maintenance: MaintenanceHandle, lfs: Option<LfsRuntime>, catalog: Arc<knot_messages::Catalog>, ref_surface: Option<Arc<dyn knot_receive::RefSurface>>,}
#[derive(Clone)]pub(crate) struct LfsRuntime { pub(crate) handle: knot_lfs::LfsHandle, pub(crate) slots: Arc<Semaphore>, pub(crate) peer_slots: Arc<PreAuthLimiter>,}
pub struct SshConfig<H, C> { pub layout: Layout, pub index: Arc<Index>, pub atproto: Arc<Atproto<H, C>>, pub knot_actor: ActorId, pub hostname: KnotHostname, pub appview: AppviewEndpoint, pub admins: BTreeSet<AccountDid>, pub admission: AdmissionPolicy, pub max_pack_bytes: MaxWireBytes, pub archive_limit: ArchiveLimit, pub ci_logs: Option<CiLogsAddr>,}
impl<H: HttpTransport, C: Clock> SshState<H, C> { pub fn new(config: SshConfig<H, C>) -> Self { let SshConfig { layout, index, atproto, knot_actor, hostname, appview, admins, admission, max_pack_bytes, archive_limit, ci_logs, } = config; Self { layout, index, atproto, knot_actor, hostname, appview, admins, admission, limits: PackLimits::default(), max_pack_bytes, archive_limit, ci_logs, slots: Slots::for_machine(), lookup_slots: ResolveSlots::new(MAX_INFLIGHT_LOOKUPS), lookup_peers: Arc::new(PreAuthLimiter::with_config(LimitConfig { rate: Some(RateLimit { burst: Burst::literal(LOOKUP_BURST_PER_PEER), refill: RefillMicros::literal(LOOKUP_REFILL_MICROS), }), per_peer_inflight: Some(PerPeerInflight::new(LOOKUP_INFLIGHT_PER_PEER)), global_inflight: Some(GlobalInflight::new(MAX_PREAUTH_LOOKUPS)), })), probe_pace: SubjectPacer::new(RateLimit { burst: Burst::literal(PROBE_BURST_PER_ACCOUNT), refill: RefillMicros::literal(PROBE_REFILL_MICROS), }), miss_pace: PeerPacer::new(RateLimit { burst: Burst::literal(MISS_BURST_PER_PEER), refill: RefillMicros::literal(MISS_REFILL_MICROS), }), key_ttl: KeyTtl::DEFAULT, peer_slots: Arc::new(PreAuthLimiter::with_config(LimitConfig::per_peer_only( PerPeerInflight::new(MAX_INFLIGHT_PER_PEER), ))), maintenance: MaintenanceHandle::disabled(), lfs: None, catalog: Arc::new(knot_messages::Catalog::defaults()), ref_surface: None, } }
pub fn with_catalog(mut self, catalog: Arc<knot_messages::Catalog>) -> Self { self.catalog = catalog; self }
pub fn with_ref_surface(mut self, surface: Arc<dyn knot_receive::RefSurface>) -> Self { self.ref_surface = Some(surface); self }
pub fn with_slots(mut self, slots: Slots) -> Self { self.slots = slots; self }
pub fn with_key_ttl(mut self, ttl: KeyTtl) -> Self { self.key_ttl = ttl; self }
pub fn with_maintenance(mut self, maintenance: MaintenanceHandle) -> Self { self.maintenance = maintenance; self }
pub fn with_lfs(mut self, handle: knot_lfs::LfsHandle, max_transfers: usize) -> Self { self.lfs = Some(LfsRuntime { handle, slots: Arc::new(Semaphore::new(max_transfers)), peer_slots: Arc::new(PreAuthLimiter::with_config(LimitConfig::per_peer_only( PerPeerInflight::new(max_transfers), ))), }); self }
pub fn with_limits(mut self, limits: PackLimits) -> Self { self.limits = limits; self }}
fn server_config(host_key: PrivateKey) -> Arc<Config> { Arc::new(Config { keys: vec![host_key], methods: MethodSet::from(&[MethodKind::PublicKey][..]), inactivity_timeout: Some(INACTIVITY_TIMEOUT), keepalive_interval: Some(KEEPALIVE_INTERVAL), auth_rejection_time: AUTH_REJECTION_TIME, preferred: Preferred { compression: Cow::Borrowed(&[compression::NONE]), ..Preferred::DEFAULT }, ..Config::default() })}
pub async fn serve<H: HttpTransport, C: Clock>( addr: SocketAddr, host_key: PrivateKey, state: Arc<SshState<H, C>>, shutdown: CancellationToken,) -> Result<(), SshError> { let listener = tokio::net::TcpListener::bind(addr).await?; serve_drained(listener, host_key, state, shutdown).await}
pub async fn serve_on_socket<H: HttpTransport, C: Clock>( listener: tokio::net::TcpListener, host_key: PrivateKey, state: Arc<SshState<H, C>>,) -> Result<(), SshError> { serve_drained(listener, host_key, state, CancellationToken::new()).await}
#[doc(hidden)]pub async fn serve_drained<H: HttpTransport, C: Clock>( listener: tokio::net::TcpListener, host_key: PrivateKey, state: Arc<SshState<H, C>>, shutdown: CancellationToken,) -> Result<(), SshError> { let config = server_config(host_key); let tracker = TaskTracker::new(); let mut server = KnotSshServer { state, tracker: tracker.clone(), }; loop { let accepted = tokio::select! { () = shutdown.cancelled() => break, accepted = listener.accept() => accepted, }; let (stream, peer) = match accepted { Ok(pair) => pair, Err(error) if is_connection_error(&error) => continue, Err(error) => { tracing::warn!("ssh accept failed, backing off: {error}"); tokio::select! { () = shutdown.cancelled() => break, () = tokio::time::sleep(ACCEPT_BACKOFF) => {} } continue; } }; let handler = server.new_client(Some(peer)); let config = Arc::clone(&config); tracker.spawn(async move { if let Ok(session) = russh::server::run_stream(config, stream, handler).await { let _ = session.await; } }); } tracker.close(); let _ = tokio::time::timeout(DRAIN_GRACE, tracker.wait()).await; Ok(())}
fn is_connection_error(error: &std::io::Error) -> bool { matches!( error.kind(), std::io::ErrorKind::ConnectionRefused | std::io::ErrorKind::ConnectionAborted | std::io::ErrorKind::ConnectionReset )}
pub fn load_or_create_host_key(path: &Path) -> Result<PrivateKey, SshError> { let report = |message: String| SshError::HostKey { path: path.display().to_string(), message, }; let load = || { ensure_secure_perms(path).map_err(&report)?; russh::keys::load_secret_key(path, None).map_err(|error| report(error.to_string())) }; if path.exists() { return load(); } let key = PrivateKey::random(&mut EntropyRng, Algorithm::Ed25519) .map_err(|error| report(error.to_string()))?; match persist_host_key(path, &key)? { Claim::Won => Ok(key), Claim::Lost => load(), }}
enum Claim { Won, Lost,}
fn persist_host_key(path: &Path, key: &PrivateKey) -> Result<Claim, SshError> { let report = |message: String| SshError::HostKey { path: path.display().to_string(), message, }; let pem = key .to_openssh(ssh_key::LineEnding::LF) .map_err(|error| report(error.to_string()))?; if let Some(parent) = path.parent() { std::fs::create_dir_all(parent).map_err(|error| report(error.to_string()))?; } let temp = unique_temp(path); write_secret(&temp, pem.as_bytes()).map_err(|error| report(error.to_string()))?; // `hard_link` instead of `rename` so that in case two knots // are booting at the same time they don't get borked // if one clobber's the other's key. here the loser reloads // winner's key. let claim = match std::fs::hard_link(&temp, path) { Ok(()) => Claim::Won, Err(error) if error.kind() == std::io::ErrorKind::AlreadyExists => Claim::Lost, Err(error) => { let _ = std::fs::remove_file(&temp); return Err(report(error.to_string())); } }; let _ = std::fs::remove_file(&temp); if let Some(parent) = path.parent() && let Ok(dir) = std::fs::File::open(parent) { let _ = dir.sync_all(); } Ok(claim)}
#[cfg(unix)]fn ensure_secure_perms(path: &Path) -> Result<(), String> { use std::os::unix::fs::MetadataExt; let mode = std::fs::metadata(path) .map_err(|error| error.to_string())? .mode(); if mode & 0o077 != 0 { return Err(format!( "private host key is group or other accessible at mode {:o}, run chmod 600 on it", mode & 0o777 )); } Ok(())}
#[cfg(not(unix))]fn ensure_secure_perms(_path: &Path) -> Result<(), String> { Ok(())}
fn unique_temp(path: &Path) -> std::path::PathBuf { use std::sync::atomic::{AtomicU64, Ordering}; static COUNTER: AtomicU64 = AtomicU64::new(0); let nonce = COUNTER.fetch_add(1, Ordering::Relaxed); let stem = path .file_name() .and_then(|name| name.to_str()) .unwrap_or("ssh_host_key"); path.with_file_name(format!(".{stem}.{}.{nonce}.tmp", std::process::id()))}
fn write_secret(path: &Path, bytes: &[u8]) -> std::io::Result<()> { use std::io::Write; let mut options = std::fs::OpenOptions::new(); options.write(true).create_new(true); #[cfg(unix)] { use std::os::unix::fs::OpenOptionsExt; options.mode(0o600); } let mut file = options.open(path)?; file.write_all(bytes)?; file.sync_all()}
struct EntropyRng;
impl rand_core::TryRng for EntropyRng { type Error = std::convert::Infallible;
fn try_next_u32(&mut self) -> Result<u32, Self::Error> { let mut bytes = [0u8; 4]; OsEntropy.fill(&mut bytes); Ok(u32::from_le_bytes(bytes)) }
fn try_next_u64(&mut self) -> Result<u64, Self::Error> { let mut bytes = [0u8; 8]; OsEntropy.fill(&mut bytes); Ok(u64::from_le_bytes(bytes)) }
fn try_fill_bytes(&mut self, dst: &mut [u8]) -> Result<(), Self::Error> { OsEntropy.fill(dst); Ok(()) }}
impl rand_core::TryCryptoRng for EntropyRng {}