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Simplify LSPS5/validator: drop time checks & custom signature storage #3961

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Merged
merged 1 commit into from
Jul 30, 2025
Merged

Simplify LSPS5/validator: drop time checks & custom signature storage #3961

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9 changes: 1 addition & 8 deletions lightning-liquidity/src/lsps5/msgs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -161,11 +161,6 @@ pub enum LSPS5ClientError {
/// The cryptographic signature from the LSP node doesn't validate.
InvalidSignature,

/// Notification timestamp is too old or too far in the future.
///
/// LSPS5 requires timestamps to be within ±10 minutes of current time.
InvalidTimestamp,

/// Detected a reused notification signature.
///
/// Indicates a potential replay attack where a previously seen
Expand All @@ -183,8 +178,7 @@ impl LSPS5ClientError {
use LSPS5ClientError::*;
match self {
InvalidSignature => Self::BASE + 1,
InvalidTimestamp => Self::BASE + 2,
ReplayAttack => Self::BASE + 3,
ReplayAttack => Self::BASE + 2,
SerializationError => LSPS5_SERIALIZATION_ERROR_CODE,
}
}
Expand All @@ -193,7 +187,6 @@ impl LSPS5ClientError {
use LSPS5ClientError::*;
match self {
InvalidSignature => "Invalid signature",
InvalidTimestamp => "Timestamp out of range",
ReplayAttack => "Replay attack detected",
SerializationError => "Error serializing LSPS5 webhook notification",
}
Expand Down
180 changes: 32 additions & 148 deletions lightning-liquidity/src/lsps5/validator.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,6 @@ use crate::alloc::string::ToString;
use crate::lsps0::ser::LSPSDateTime;
use crate::lsps5::msgs::WebhookNotification;
use crate::sync::Mutex;
use crate::utils::time::TimeProvider;

use lightning::util::message_signing;

Expand All @@ -24,32 +23,8 @@ use bitcoin::secp256k1::PublicKey;
use alloc::collections::VecDeque;
use alloc::string::String;

use core::ops::Deref;
use core::time::Duration;

/// Configuration for signature storage.
#[derive(Clone, Copy, Debug)]
pub struct SignatureStorageConfig {
/// Maximum number of signatures to store.
pub max_signatures: usize,
/// Retention time for signatures in minutes.
pub retention_minutes: Duration,
}

/// Default retention time for signatures in minutes (LSPS5 spec requires min 20 minutes).
pub const DEFAULT_SIGNATURE_RETENTION_MINUTES: u64 = 20;

/// Default maximum number of stored signatures.
pub const DEFAULT_MAX_SIGNATURES: usize = 1000;

impl Default for SignatureStorageConfig {
fn default() -> Self {
Self {
max_signatures: DEFAULT_MAX_SIGNATURES,
retention_minutes: Duration::from_secs(DEFAULT_SIGNATURE_RETENTION_MINUTES * 60),
}
}
}
/// Maximum number of recent signatures to track for replay attack prevention.
pub const MAX_RECENT_SIGNATURES: usize = 5;

/// A utility for validating webhook notifications from an LSP.
///
Expand All @@ -60,66 +35,26 @@ impl Default for SignatureStorageConfig {
///
/// # Core Capabilities
///
/// - `validate(...)` -> Verifies signature, timestamp, and protects against replay attacks.
///
/// # Usage
/// - `validate(...)` -> Verifies signature, and protects against replay attacks.
///
/// The validator requires a `SignatureStore` to track recently seen signatures
/// to prevent replay attacks. You should create a single `LSPS5Validator` instance
/// and share it across all requests.
/// The validator stores a [`small number`] of the most recently seen signatures
/// to protect against replays of the same notification.
///
/// [`small number`]: MAX_RECENT_SIGNATURES
/// [`bLIP-55 / LSPS5 specification`]: https://github.com/lightning/blips/pull/55/files
pub struct LSPS5Validator<TP: Deref, SS: Deref>
where
TP::Target: TimeProvider,
SS::Target: SignatureStore,
{
time_provider: TP,
signature_store: SS,
pub struct LSPS5Validator {
recent_signatures: Mutex<VecDeque<String>>,
}

impl<TP: Deref, SS: Deref> LSPS5Validator<TP, SS>
where
TP::Target: TimeProvider,
SS::Target: SignatureStore,
{
/// Creates a new `LSPS5Validator`.
pub fn new(time_provider: TP, signature_store: SS) -> Self {
Self { time_provider, signature_store }
}

fn verify_notification_signature(
&self, counterparty_node_id: PublicKey, signature_timestamp: &LSPSDateTime,
signature: &str, notification: &WebhookNotification,
) -> Result<(), LSPS5ClientError> {
let now =
LSPSDateTime::new_from_duration_since_epoch(self.time_provider.duration_since_epoch());
let diff = signature_timestamp.abs_diff(&now);
const MAX_TIMESTAMP_DRIFT_SECS: u64 = 600;
if diff > MAX_TIMESTAMP_DRIFT_SECS {
return Err(LSPS5ClientError::InvalidTimestamp);
}

let notification_json = serde_json::to_string(notification)
.map_err(|_| LSPS5ClientError::SerializationError)?;
let message = format!(
"LSPS5: DO NOT SIGN THIS MESSAGE MANUALLY: LSP: At {} I notify {}",
signature_timestamp.to_rfc3339(),
notification_json
);

if message_signing::verify(message.as_bytes(), signature, &counterparty_node_id) {
Ok(())
} else {
Err(LSPS5ClientError::InvalidSignature)
}
impl LSPS5Validator {
/// Create a new LSPS5Validator instance.
pub fn new() -> Self {
Self { recent_signatures: Mutex::new(VecDeque::with_capacity(MAX_RECENT_SIGNATURES)) }
}

/// Parse and validate a webhook notification received from an LSP.
///
/// Verifies the webhook delivery by checking the timestamp is within ±10 minutes,
/// ensuring no signature replay within the retention window, and verifying the
/// zbase32 LN-style signature against the LSP's node ID.
/// Verifies the webhook delivery by verifying the zbase32 LN-style signature against the LSP's node ID and ensuring that the signature is not a replay of a previously seen notification (within the last [`MAX_RECENT_SIGNATURES`] notifications).
///
/// Call this method on your proxy/server before processing any webhook notification
/// to ensure its authenticity.
Expand All @@ -130,91 +65,40 @@ where
/// - `signature`: The zbase32-encoded LN signature over timestamp+body.
/// - `notification`: The [`WebhookNotification`] received from the LSP.
///
/// Returns the validated [`WebhookNotification`] or an error for invalid timestamp,
/// replay attack, or signature verification failure.
/// Returns the validated [`WebhookNotification`] or an error for signature verification failure or replay attack.
///
/// [`WebhookNotification`]: super::msgs::WebhookNotification
/// [`MAX_RECENT_SIGNATURES`]: MAX_RECENT_SIGNATURES
pub fn validate(
&self, counterparty_node_id: PublicKey, timestamp: &LSPSDateTime, signature: &str,
notification: &WebhookNotification,
) -> Result<WebhookNotification, LSPS5ClientError> {
self.verify_notification_signature(
counterparty_node_id,
timestamp,
signature,
notification,
)?;
let notification_json = serde_json::to_string(notification)
.map_err(|_| LSPS5ClientError::SerializationError)?;
let message = format!(
"LSPS5: DO NOT SIGN THIS MESSAGE MANUALLY: LSP: At {} I notify {}",
timestamp.to_rfc3339(),
notification_json
);

if self.signature_store.exists(signature)? {
return Err(LSPS5ClientError::ReplayAttack);
if !message_signing::verify(message.as_bytes(), signature, &counterparty_node_id) {
return Err(LSPS5ClientError::InvalidSignature);
}

self.signature_store.store(signature)?;
self.check_for_replay_attack(signature)?;

Ok(notification.clone())
}
}

/// Trait for storing and checking webhook notification signatures to prevent replay attacks.
pub trait SignatureStore {
/// Checks if a signature already exists in the store.
fn exists(&self, signature: &str) -> Result<bool, LSPS5ClientError>;
/// Stores a new signature.
fn store(&self, signature: &str) -> Result<(), LSPS5ClientError>;
}

/// An in-memory store for webhook notification signatures.
pub struct InMemorySignatureStore<TP: Deref>
where
TP::Target: TimeProvider,
{
recent_signatures: Mutex<VecDeque<(String, LSPSDateTime)>>,
config: SignatureStorageConfig,
time_provider: TP,
}

impl<TP: Deref> InMemorySignatureStore<TP>
where
TP::Target: TimeProvider,
{
/// Creates a new `InMemorySignatureStore`.
pub fn new(config: SignatureStorageConfig, time_provider: TP) -> Self {
Self {
recent_signatures: Mutex::new(VecDeque::with_capacity(config.max_signatures)),
config,
time_provider,
}
}
}

impl<TP: Deref> SignatureStore for InMemorySignatureStore<TP>
where
TP::Target: TimeProvider,
{
fn exists(&self, signature: &str) -> Result<bool, LSPS5ClientError> {
let recent_signatures = self.recent_signatures.lock().unwrap();
for (stored_sig, _) in recent_signatures.iter() {
if stored_sig == signature {
return Ok(true);
}
fn check_for_replay_attack(&self, signature: &str) -> Result<(), LSPS5ClientError> {
let mut signatures = self.recent_signatures.lock().unwrap();
if signatures.contains(&signature.to_string()) {
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@TheBlueMatt TheBlueMatt Jul 29, 2025

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Suggested change
if signatures.contains(&signature.to_string()) {
if signatures.iter().any(|sig| &sig == &signature) {

return Err(LSPS5ClientError::ReplayAttack);
}
Ok(false)
}

fn store(&self, signature: &str) -> Result<(), LSPS5ClientError> {
let now =
LSPSDateTime::new_from_duration_since_epoch(self.time_provider.duration_since_epoch());
let mut recent_signatures = self.recent_signatures.lock().unwrap();

recent_signatures.push_back((signature.to_string(), now.clone()));

let retention_secs = self.config.retention_minutes.as_secs();
recent_signatures.retain(|(_, ts)| now.abs_diff(ts) <= retention_secs);

if recent_signatures.len() > self.config.max_signatures {
let excess = recent_signatures.len() - self.config.max_signatures;
recent_signatures.drain(0..excess);
if signatures.len() == MAX_RECENT_SIGNATURES {
signatures.pop_back();
}
signatures.push_front(signature.to_string());
Ok(())
}
}
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