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//! Per-account login lockout — defends against credential stuffing /
//! brute-force attacks that bypass per-IP rate limits.
//!
//! Backed by the cache layer (in-memory or Redis). Each failed login
//! increments a counter; once it crosses the threshold, the account is
//! locked for a configurable duration. Successful logins clear the counter.
//!
//! ## Quick start
//!
//! ```ignore
//! use rustango::account_lockout::Lockout;
//! use rustango::cache::InMemoryCache;
//! use std::sync::Arc;
//! use std::time::Duration;
//!
//! let cache: Arc<dyn rustango::cache::Cache> = Arc::new(InMemoryCache::new());
//! let lockout = Lockout::new(cache)
//! .max_attempts(5)
//! .lockout_duration(Duration::from_secs(900)); // 15 min
//!
//! // Login handler:
//! let username = "alice";
//!
//! if lockout.is_locked(username).await {
//! return Err("account temporarily locked — try again later");
//! }
//!
//! if !verify_credentials(username, password).await? {
//! lockout.record_failure(username).await;
//! return Err("bad credentials");
//! }
//!
//! lockout.clear(username).await; // success → reset counter
//! issue_session(username).await
//! ```
//!
//! ## Why per-account, not per-IP?
//!
//! Per-IP rate limiting (`RateLimitLayer::per_ip`) catches one attacker
//! pounding one endpoint. Per-account lockout catches a botnet trying
//! the same username from thousands of IPs — the *account* is the rate
//! axis. Both belong in your stack.
use std::sync::Arc;
use std::time::Duration;
use crate::cache::Cache;
/// Default attempts before lockout.
pub const DEFAULT_MAX_ATTEMPTS: u32 = 5;
/// Default lockout duration (15 minutes).
pub const DEFAULT_LOCKOUT_DURATION_SECS: u64 = 900;
/// Per-account lockout tracker.
pub struct Lockout {
cache: Arc<dyn Cache>,
max_attempts: u32,
lockout_duration: Duration,
counter_ttl: Duration,
key_prefix: String,
}
impl Lockout {
/// New tracker with default thresholds (5 attempts → 15 min lock,
/// counter expires after 1 hour of inactivity).
#[must_use]
pub fn new(cache: Arc<dyn Cache>) -> Self {
Self {
cache,
max_attempts: DEFAULT_MAX_ATTEMPTS,
lockout_duration: Duration::from_secs(DEFAULT_LOCKOUT_DURATION_SECS),
counter_ttl: Duration::from_secs(3600),
key_prefix: "lockout:".to_owned(),
}
}
/// Override the attempts threshold.
#[must_use]
pub fn max_attempts(mut self, n: u32) -> Self {
self.max_attempts = n.max(1);
self
}
/// Override the lockout duration.
#[must_use]
pub fn lockout_duration(mut self, d: Duration) -> Self {
self.lockout_duration = d;
self
}
/// Override how long the failure counter persists between attempts.
/// Defaults to 1 hour — counters reset themselves if the user goes
/// quiet for a while.
#[must_use]
pub fn counter_ttl(mut self, d: Duration) -> Self {
self.counter_ttl = d;
self
}
/// Override the cache-key prefix. Defaults to `"lockout:"`. Useful
/// when sharing one cache across multiple lockout namespaces (login
/// vs MFA vs API key etc.).
#[must_use]
pub fn key_prefix(mut self, p: impl Into<String>) -> Self {
self.key_prefix = p.into();
self
}
/// Check whether `account` is currently locked. Returns `true` to
/// reject the login attempt; `false` to proceed with verification.
pub async fn is_locked(&self, account: &str) -> bool {
self.cache
.exists(&self.lock_key(account))
.await
.unwrap_or(false)
}
/// Record a failed login attempt. Returns the new attempt count.
/// When the count reaches `max_attempts`, the account is locked
/// for `lockout_duration`.
pub async fn record_failure(&self, account: &str) -> u32 {
let counter_key = self.counter_key(account);
let current: u32 = self
.cache
.get(&counter_key)
.await
.ok()
.flatten()
.and_then(|s| s.parse().ok())
.unwrap_or(0);
let next = current + 1;
let _ = self
.cache
.set(&counter_key, &next.to_string(), Some(self.counter_ttl))
.await;
if next >= self.max_attempts {
// Set the lock flag with TTL = lockout_duration
let _ = self
.cache
.set(&self.lock_key(account), "1", Some(self.lockout_duration))
.await;
}
next
}
/// Clear the failure counter and any active lock. Call on successful
/// authentication.
pub async fn clear(&self, account: &str) {
let _ = self.cache.delete(&self.counter_key(account)).await;
let _ = self.cache.delete(&self.lock_key(account)).await;
}
/// Read the current failure count for an account. 0 when absent.
pub async fn attempt_count(&self, account: &str) -> u32 {
self.cache
.get(&self.counter_key(account))
.await
.ok()
.flatten()
.and_then(|s| s.parse().ok())
.unwrap_or(0)
}
/// Force-lock an account (e.g. by an admin action).
pub async fn force_lock(&self, account: &str) {
let _ = self
.cache
.set(&self.lock_key(account), "1", Some(self.lockout_duration))
.await;
}
fn counter_key(&self, account: &str) -> String {
format!("{}attempts:{}", self.key_prefix, account)
}
fn lock_key(&self, account: &str) -> String {
format!("{}locked:{}", self.key_prefix, account)
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::cache::InMemoryCache;
fn lockout(max: u32) -> Lockout {
let cache: Arc<dyn Cache> = Arc::new(InMemoryCache::new());
Lockout::new(cache)
.max_attempts(max)
.lockout_duration(Duration::from_secs(60))
}
#[tokio::test]
async fn fresh_account_not_locked() {
let l = lockout(5);
assert!(!l.is_locked("alice").await);
assert_eq!(l.attempt_count("alice").await, 0);
}
#[tokio::test]
async fn record_failure_increments_count() {
let l = lockout(5);
assert_eq!(l.record_failure("alice").await, 1);
assert_eq!(l.record_failure("alice").await, 2);
assert_eq!(l.attempt_count("alice").await, 2);
assert!(!l.is_locked("alice").await);
}
#[tokio::test]
async fn locks_at_threshold() {
let l = lockout(3);
for _ in 0..2 {
l.record_failure("alice").await;
}
assert!(!l.is_locked("alice").await);
l.record_failure("alice").await;
assert!(l.is_locked("alice").await);
}
#[tokio::test]
async fn clear_resets_counter_and_lock() {
let l = lockout(2);
l.record_failure("alice").await;
l.record_failure("alice").await;
assert!(l.is_locked("alice").await);
l.clear("alice").await;
assert!(!l.is_locked("alice").await);
assert_eq!(l.attempt_count("alice").await, 0);
}
#[tokio::test]
async fn force_lock_works_without_failures() {
let l = lockout(5);
l.force_lock("alice").await;
assert!(l.is_locked("alice").await);
}
#[tokio::test]
async fn lockout_expires() {
let cache: Arc<dyn Cache> = Arc::new(InMemoryCache::new());
let l = Lockout::new(cache)
.max_attempts(2)
.lockout_duration(Duration::from_millis(100));
l.record_failure("alice").await;
l.record_failure("alice").await;
assert!(l.is_locked("alice").await);
tokio::time::sleep(Duration::from_millis(150)).await;
assert!(!l.is_locked("alice").await);
}
#[tokio::test]
async fn separate_accounts_dont_share_state() {
let l = lockout(2);
l.record_failure("alice").await;
l.record_failure("alice").await;
assert!(l.is_locked("alice").await);
assert!(!l.is_locked("bob").await);
assert_eq!(l.attempt_count("bob").await, 0);
}
#[tokio::test]
async fn key_prefix_isolates_namespaces() {
let cache: Arc<dyn Cache> = Arc::new(InMemoryCache::new());
let l1 = Lockout::new(cache.clone())
.key_prefix("login:")
.max_attempts(2);
let l2 = Lockout::new(cache).key_prefix("mfa:").max_attempts(2);
l1.record_failure("alice").await;
l1.record_failure("alice").await;
assert!(l1.is_locked("alice").await);
assert!(
!l2.is_locked("alice").await,
"MFA namespace shouldn't be locked"
);
}
#[tokio::test]
async fn max_attempts_floors_at_1() {
let l = lockout(0);
l.record_failure("alice").await;
assert!(
l.is_locked("alice").await,
"max_attempts(0) should be treated as 1"
);
}
}