Persist encrypted peer approval delivery and bind discovery invite identities

2026-10-05 22:27:43 -04:00
parent e97f958f45
commit 10d31ae13c
8 changed files with 636 additions and 77 deletions
@@ -0,0 +1,199 @@
+//! Durable, node-encrypted approval replies. Relay acknowledgement is not peer
+//! acceptance: keep retrying the same invite until reciprocal membership exists.
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::path::Path;
+use tokio::{fs, io::AsyncWriteExt};
+
+const FILE: &str = "federation/handshake-delivery.enc";
+const DOMAIN: &[u8] = b"archipelago-handshake-delivery-v1";
+static LOCK: tokio::sync::Mutex<()> = tokio::sync::Mutex::const_new(());
+
+#[derive(Clone, Serialize, Deserialize)]
+pub(crate) struct ApprovalReply {
+    pub request_id: String,
+    pub recipient: String,
+    pub expected_did: String,
+    pub invite_code: String,
+    pub attempts: u32,
+    pub next_attempt: i64,
+}
+
+async fn load(data_dir: &Path) -> Result<Vec<ApprovalReply>> {
+    let bytes = match fs::read(data_dir.join(FILE)).await {
+        Ok(bytes) => bytes,
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => return Ok(Vec::new()),
+        Err(e) => return Err(e.into()),
+    };
+    let key = crate::storage_crypto::derive_key(data_dir, DOMAIN).await?;
+    let plaintext = crate::storage_crypto::open(&bytes, &key)?;
+    serde_json::from_slice(&plaintext)
+        .context("Invalid handshake delivery store; preserved for recovery")
+}
+
+async fn save(data_dir: &Path, entries: &[ApprovalReply]) -> Result<()> {
+    let key = crate::storage_crypto::derive_key(data_dir, DOMAIN).await?;
+    let bytes = crate::storage_crypto::seal(&serde_json::to_vec(entries)?, &key)?;
+    let path = data_dir.join(FILE);
+    let parent = path.parent().context("Delivery parent missing")?;
+    fs::create_dir_all(parent).await?;
+    let temporary = parent.join(format!(".delivery-{}.tmp", uuid::Uuid::new_v4()));
+    let result = async {
+        let mut file = fs::OpenOptions::new()
+            .create_new(true)
+            .write(true)
+            .mode(0o600)
+            .open(&temporary)
+            .await?;
+        file.write_all(&bytes).await?;
+        file.sync_all().await?;
+        drop(file);
+        fs::rename(&temporary, &path).await?;
+        fs::File::open(parent).await?.sync_all().await?;
+        Ok::<_, anyhow::Error>(())
+    }
+    .await;
+    if result.is_err() {
+        let _ = fs::remove_file(temporary).await;
+    }
+    result
+}
+
+pub(crate) async fn find(data_dir: &Path, request_id: &str) -> Result<Option<ApprovalReply>> {
+    let _guard = LOCK.lock().await;
+    Ok(load(data_dir)
+        .await?
+        .into_iter()
+        .find(|entry| entry.request_id == request_id))
+}
+
+pub(crate) async fn stage(data_dir: &Path, reply: ApprovalReply) -> Result<ApprovalReply> {
+    let _guard = LOCK.lock().await;
+    let mut entries = load(data_dir).await?;
+    if let Some(existing) = entries
+        .iter()
+        .find(|entry| entry.request_id == reply.request_id)
+    {
+        anyhow::ensure!(
+            existing.recipient == reply.recipient && existing.expected_did == reply.expected_did,
+            "Approval recipient changed; refusing delivery"
+        );
+        return Ok(existing.clone());
+    }
+    anyhow::ensure!(entries.len() < 1024, "Handshake delivery queue is full");
+    entries.push(reply.clone());
+    save(data_dir, &entries).await?;
+    Ok(reply)
+}
+
+/// Claim before sending, including failed sends. Concurrent polls cannot create
+/// retry storms; a crash after this write delays but never loses the reply.
+pub(crate) async fn claim(
+    data_dir: &Path,
+    request_id: &str,
+    now: i64,
+) -> Result<Option<ApprovalReply>> {
+    let _guard = LOCK.lock().await;
+    let mut entries = load(data_dir).await?;
+    let Some(entry) = entries
+        .iter_mut()
+        .find(|entry| entry.request_id == request_id)
+    else {
+        return Ok(None);
+    };
+    if entry.next_attempt > now {
+        return Ok(None);
+    }
+    entry.attempts = entry.attempts.saturating_add(1);
+    let delay = 30_i64
+        .saturating_mul(1_i64 << entry.attempts.min(7))
+        .min(3600);
+    entry.next_attempt = now.saturating_add(delay);
+    let claimed = entry.clone();
+    save(data_dir, &entries).await?;
+    Ok(Some(claimed))
+}
+
+pub(crate) async fn remove(data_dir: &Path, request_id: &str) -> Result<()> {
+    let _guard = LOCK.lock().await;
+    let mut entries = load(data_dir).await?;
+    let before = entries.len();
+    entries.retain(|entry| entry.request_id != request_id);
+    if entries.len() != before {
+        save(data_dir, &entries).await?;
+    }
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    async fn fixture() -> tempfile::TempDir {
+        let dir = tempfile::tempdir().unwrap();
+        fs::create_dir_all(dir.path().join("identity"))
+            .await
+            .unwrap();
+        fs::write(dir.path().join("identity/node_key"), [7; 32])
+            .await
+            .unwrap();
+        dir
+    }
+    fn reply() -> ApprovalReply {
+        ApprovalReply {
+            request_id: "request-1".into(),
+            recipient: "recipient".into(),
+            expected_did: "did:key:peer".into(),
+            invite_code: "secret-invite".into(),
+            attempts: 0,
+            next_attempt: 0,
+        }
+    }
+    #[tokio::test]
+    async fn encrypted_reply_survives_reload_and_retry_claim_is_exclusive() {
+        let dir = fixture().await;
+        stage(dir.path(), reply()).await.unwrap();
+        let raw = fs::read(dir.path().join(FILE)).await.unwrap();
+        assert!(!raw.windows(13).any(|bytes| bytes == b"secret-invite"));
+        assert_eq!(
+            find(dir.path(), "request-1")
+                .await
+                .unwrap()
+                .unwrap()
+                .invite_code,
+            "secret-invite"
+        );
+        let (a, b) = tokio::join!(
+            claim(dir.path(), "request-1", 100),
+            claim(dir.path(), "request-1", 100)
+        );
+        assert_eq!(
+            usize::from(a.unwrap().is_some()) + usize::from(b.unwrap().is_some()),
+            1
+        );
+        assert!(claim(dir.path(), "request-1", 159).await.unwrap().is_none());
+        assert_eq!(
+            claim(dir.path(), "request-1", 160)
+                .await
+                .unwrap()
+                .unwrap()
+                .attempts,
+            2
+        );
+        remove(dir.path(), "request-1").await.unwrap();
+        assert!(find(dir.path(), "request-1").await.unwrap().is_none());
+    }
+    #[tokio::test]
+    async fn corrupt_store_is_not_overwritten_and_recipient_cannot_change() {
+        let dir = fixture().await;
+        stage(dir.path(), reply()).await.unwrap();
+        let mut other = reply();
+        other.recipient = "different-recipient".into();
+        assert!(stage(dir.path(), other).await.is_err());
+        let path = dir.path().join(FILE);
+        let mut raw = fs::read(&path).await.unwrap();
+        raw[20] ^= 1;
+        fs::write(&path, &raw).await.unwrap();
+        assert!(stage(dir.path(), reply()).await.is_err());
+        assert_eq!(fs::read(path).await.unwrap(), raw);
+    }
+}