community: friends, two signed answers on one request carried over soulseek, one answer is only ever pending

src-tauri/src/friends.rs

@@ -0,0 +1,546 @@
+//! Friends, product side (F4 §7.5 → the app). A friendship is two
+//! reciprocal signed assertions on one relationship id and request hash;
+//! everything else — one assertion, a declined request, a revocation — is
+//! shown as exactly what it is. Proofs stay on this device; nothing is
+//! published.
+//!
+//! Carry today: the same Soulseek private-message channel the link proof
+//! uses (the encrypted inbox of F5 takes over later). The server can see
+//! that one account wrote to another; it cannot forge who wrote, which is
+//! the one thing these messages need from it.
+//!
+//! Wire: `SSFRIEND1?<b64 request>` asks, `SSFRIEND1!<b64 assertion>`
+//! accepts or revokes, `SSFRIEND1-<b58 relationship id>` declines. An
+//! incoming REQUEST is bound to its sender by the link handshake: the
+//! request names a persona key, and the sender is asked (over PM, with a
+//! fresh nonce) to prove that key is theirs before the request is shown.
+//! That ask waits on a PM, so the pump hands friend messages to a task —
+//! awaiting inline would block the very loop that delivers the answer.
+
+use std::collections::BTreeMap;
+use std::path::PathBuf;
+use std::time::{SystemTime, UNIX_EPOCH};
+
+use persona_state::friend as fr;
+use persona_state::slsk_link::normalize_username;
+use serde::{Deserialize, Serialize};
+use tauri::{Emitter, Manager};
+
+use crate::persona;
+use crate::slsk_link;
+use crate::state::AppState;
+
+const REQ_PREFIX: &str = "SSFRIEND1?";
+const ASSERT_PREFIX: &str = "SSFRIEND1!";
+const DECLINE_PREFIX: &str = "SSFRIEND1-";
+/// A request stays open this long.
+const REQUEST_TTL_SECS: u64 = 7 * 24 * 3600;
+pub const EVENT: &str = "community:friends";
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+struct Relationship {
+    /// Their Soulseek account as the server spelled it when it last spoke.
+    username: String,
+    username_normalized: String,
+    their_key: String,
+    my_key: String,
+    request: fr::FriendRequest,
+    request_from_me: bool,
+    #[serde(default)]
+    assertions: Vec<fr::FriendAssertion>,
+    /// Local-only stances the verifier has no signature for.
+    #[serde(default)]
+    declined_by_me: bool,
+    #[serde(default)]
+    declined_by_them: bool,
+    created_at: u64,
+    updated_at: u64,
+}
+
+#[derive(Default, Serialize, Deserialize)]
+struct Store {
+    #[serde(default)]
+    relationships: BTreeMap<String, Relationship>,
+}
+
+/// What the UI sees: one row per relationship, status from the verifier.
+#[derive(Debug, Serialize)]
+pub struct RelationshipView {
+    pub id: String,
+    pub username: String,
+    pub username_normalized: String,
+    pub persona_key: String,
+    pub direction: &'static str,
+    /// friends | pending-out | pending-in | accepted-waiting | declined |
+    /// revoked | expired | reacceptance-required
+    pub state: String,
+    pub since: u64,
+    pub updated_at: u64,
+    pub expires_at: u64,
+}
+
+fn now_secs() -> u64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map(|d| d.as_secs())
+        .unwrap_or(0)
+}
+fn nonce16() -> [u8; 16] {
+    use rand::RngCore;
+    let mut n = [0u8; 16];
+    rand::thread_rng().fill_bytes(&mut n);
+    n
+}
+fn b58(bytes: &[u8]) -> String {
+    bs58::encode(bytes).into_string()
+}
+fn key_of(b58s: &str) -> Result<[u8; 32], String> {
+    bs58::decode(b58s)
+        .into_vec()
+        .map_err(|e| format!("bad key: {e}"))?
+        .as_slice()
+        .try_into()
+        .map_err(|_| "key is not 32 bytes".to_string())
+}
+
+fn path(app: &tauri::AppHandle) -> Result<PathBuf, String> {
+    Ok(app
+        .path()
+        .app_data_dir()
+        .map_err(|e| e.to_string())?
+        .join("freenet")
+        .join("friends.json"))
+}
+fn load(app: &tauri::AppHandle) -> Store {
+    path(app)
+        .ok()
+        .and_then(|p| std::fs::read(p).ok())
+        .and_then(|b| serde_json::from_slice(&b).ok())
+        .unwrap_or_default()
+}
+fn save(app: &tauri::AppHandle, store: &Store) -> Result<(), String> {
+    let p = path(app)?;
+    if let Some(dir) = p.parent() {
+        std::fs::create_dir_all(dir).map_err(|e| e.to_string())?;
+    }
+    std::fs::write(&p, serde_json::to_vec_pretty(store).map_err(|e| e.to_string())?)
+        .map_err(|e| e.to_string())?;
+    let _ = app.emit(EVENT, ());
+    Ok(())
+}
+
+fn view_of(id: &str, r: &Relationship, now: u64) -> RelationshipView {
+    let (my, their) = (key_of(&r.my_key), key_of(&r.their_key));
+    let status = match (my, their) {
+        (Ok(m), Ok(t)) => fr::friendship_status(
+            &m,
+            &t,
+            &r.request.relationship_id,
+            &fr::request_hash(&r.request),
+            &r.assertions,
+            &[],
+        ),
+        _ => fr::FriendStatus::NotRelated,
+    };
+    let mine_accepted = r
+        .assertions
+        .iter()
+        .any(|a| b58(&a.signer) == r.my_key && a.accepted);
+    let state = match status {
+        fr::FriendStatus::Friends => "friends",
+        fr::FriendStatus::Revoked => "revoked",
+        fr::FriendStatus::ReacceptanceRequired => "reacceptance-required",
+        fr::FriendStatus::PendingOneSided | fr::FriendStatus::NotRelated => {
+            if r.declined_by_me || r.declined_by_them {
+                "declined"
+            } else if now > r.request.expires_at && status == fr::FriendStatus::NotRelated {
+                "expired"
+            } else if mine_accepted {
+                "accepted-waiting"
+            } else if r.request_from_me {
+                "pending-out"
+            } else {
+                "pending-in"
+            }
+        }
+    };
+    let since = r
+        .assertions
+        .iter()
+        .filter(|a| a.accepted)
+        .map(|a| a.seq)
+        .max()
+        .unwrap_or(r.created_at);
+    RelationshipView {
+        id: id.to_string(),
+        username: r.username.clone(),
+        username_normalized: r.username_normalized.clone(),
+        persona_key: r.their_key.clone(),
+        direction: if r.request_from_me { "out" } else { "in" },
+        state: state.to_string(),
+        since,
+        updated_at: r.updated_at,
+        expires_at: r.request.expires_at,
+    }
+}
+
+async fn my_key(app: &tauri::AppHandle) -> Result<[u8; 32], String> {
+    let adapter = app.state::<AppState>().freenet.clone();
+    let info = persona::current(&adapter)
+        .await?
+        .ok_or("create a SoulStream identity first")?;
+    key_of(&info.public_key)
+}
+async fn send_pm(app: &tauri::AppHandle, to: &str, text: &str) -> Result<(), String> {
+    let st = app.state::<AppState>();
+    let guard = st.client.lock().await;
+    guard
+        .as_ref()
+        .ok_or("not connected to Soulseek")?
+        .message_user(to, text)
+        .map_err(|e| e.to_string())
+}
+fn encode<T: Serialize>(prefix: &str, v: &T) -> Result<String, String> {
+    use base64::Engine;
+    let bytes = bincode::serialize(v).map_err(|e| e.to_string())?;
+    Ok(format!("{prefix}{}", base64::engine::general_purpose::STANDARD.encode(bytes)))
+}
+fn decode<T: for<'de> Deserialize<'de>>(b64: &str) -> Option<T> {
+    use base64::Engine;
+    let bytes = base64::engine::general_purpose::STANDARD.decode(b64.trim()).ok()?;
+    bincode::deserialize(&bytes).ok()
+}
+
+async fn sign_assertion(app: &tauri::AppHandle, mut a: fr::FriendAssertion) -> Result<fr::FriendAssertion, String> {
+    let adapter = app.state::<AppState>().freenet.clone();
+    a.sig = persona::sign(&adapter, fr::FRIEND_DOMAIN, fr::assertion_sign_payload(&a)).await?;
+    Ok(a)
+}
+
+// ---------------------------------------------------------------- outgoing
+
+/// Ask `username` to be friends. Needs their verified link (the drawer's
+/// "Ask for their SoulStream ID") — the request is addressed to a KEY.
+pub async fn request(app: &tauri::AppHandle, username: &str) -> Result<RelationshipView, String> {
+    let me = my_key(app).await?;
+    let link = slsk_link::known_link(app, username)
+        .ok_or("verify their SoulStream ID first (the drawer's Ask button)")?;
+    let their = key_of(&link.persona_key)?;
+    let now = now_secs();
+    let mut req = fr::FriendRequest {
+        relationship_id: nonce16(),
+        sender: me,
+        recipient: their,
+        nonce: nonce16(),
+        issued_at: now,
+        expires_at: now + REQUEST_TTL_SECS,
+        sig: vec![],
+    };
+    let adapter = app.state::<AppState>().freenet.clone();
+    req.sig = persona::sign(&adapter, fr::FRIEND_DOMAIN, fr::request_sign_payload(&req)).await?;
+    let id = b58(&req.relationship_id);
+    let rel = Relationship {
+        username: link.username.clone(),
+        username_normalized: link.username_normalized.clone(),
+        their_key: link.persona_key.clone(),
+        my_key: b58(&me),
+        request: req.clone(),
+        request_from_me: true,
+        assertions: vec![],
+        declined_by_me: false,
+        declined_by_them: false,
+        created_at: now,
+        updated_at: now,
+    };
+    send_pm(app, &link.username, &encode(REQ_PREFIX, &req)?).await?;
+    let mut store = load(app);
+    store.relationships.insert(id.clone(), rel);
+    save(app, &store)?;
+    log::info!("friends: request sent to {}", link.username);
+    Ok(view_of(&id, &store.relationships[&id], now))
+}
+
+/// Accept an incoming request: sign our assertion, send it, remember it.
+/// Friendship is still one-sided until their reciprocal assertion arrives.
+pub async fn accept(app: &tauri::AppHandle, id: &str) -> Result<RelationshipView, String> {
+    let me = my_key(app).await?;
+    let mut store = load(app);
+    let rel = store.relationships.get_mut(id).ok_or("no such request")?;
+    if rel.request_from_me {
+        return Err("that request is yours to wait on, not to accept".into());
+    }
+    let their = key_of(&rel.their_key)?;
+    let now = now_secs();
+    let a = sign_assertion(
+        app,
+        fr::FriendAssertion {
+            relationship_id: rel.request.relationship_id,
+            signer: me,
+            peer: their,
+            request_hash: fr::request_hash(&rel.request),
+            accepted: true,
+            seq: now,
+            sig: vec![],
+        },
+    )
+    .await?;
+    send_pm(app, &rel.username, &encode(ASSERT_PREFIX, &a)?).await?;
+    rel.assertions.push(a);
+    rel.declined_by_me = false;
+    rel.updated_at = now;
+    let v = view_of(id, rel, now);
+    save(app, &store)?;
+    Ok(v)
+}
+
+pub async fn decline(app: &tauri::AppHandle, id: &str) -> Result<RelationshipView, String> {
+    let mut store = load(app);
+    let rel = store.relationships.get_mut(id).ok_or("no such request")?;
+    let now = now_secs();
+    rel.declined_by_me = true;
+    rel.updated_at = now;
+    let _ = send_pm(app, &rel.username, &format!("{DECLINE_PREFIX}{id}")).await;
+    let v = view_of(id, rel, now);
+    save(app, &store)?;
+    Ok(v)
+}
+
+/// Unfriend: a signed revocation goes to them; the record stays as
+/// "revoked" — the design's honesty about what a removal can and cannot do.
+pub async fn remove(app: &tauri::AppHandle, id: &str) -> Result<RelationshipView, String> {
+    let me = my_key(app).await?;
+    let mut store = load(app);
+    let rel = store.relationships.get_mut(id).ok_or("no such relationship")?;
+    let their = key_of(&rel.their_key)?;
+    let now = now_secs();
+    let a = sign_assertion(
+        app,
+        fr::FriendAssertion {
+            relationship_id: rel.request.relationship_id,
+            signer: me,
+            peer: their,
+            request_hash: fr::request_hash(&rel.request),
+            accepted: false,
+            seq: now,
+            sig: vec![],
+        },
+    )
+    .await?;
+    let _ = send_pm(app, &rel.username, &encode(ASSERT_PREFIX, &a)?).await;
+    rel.assertions.push(a);
+    rel.updated_at = now;
+    let v = view_of(id, rel, now);
+    save(app, &store)?;
+    Ok(v)
+}
+
+pub fn forget(app: &tauri::AppHandle, id: &str) -> Result<(), String> {
+    let mut store = load(app);
+    store.relationships.remove(id);
+    save(app, &store)
+}
+
+pub fn list(app: &tauri::AppHandle) -> Vec<RelationshipView> {
+    let now = now_secs();
+    let store = load(app);
+    let mut v: Vec<_> = store
+        .relationships
+        .iter()
+        .map(|(id, r)| view_of(id, r, now))
+        .collect();
+    v.sort_by(|a, b| b.updated_at.cmp(&a.updated_at));
+    v
+}
+
+// ---------------------------------------------------------------- incoming
+
+async fn on_request(app: tauri::AppHandle, from: String, req: fr::FriendRequest) {
+    if !fr::verify_request(&req) {
+        log::warn!("friends: request from {from} does not verify");
+        return;
+    }
+    let Ok(me) = my_key(&app).await else {
+        log::debug!("friends: request from {from}, but no persona here to receive it");
+        return;
+    };
+    if req.recipient != me {
+        log::debug!("friends: request from {from} is addressed to another persona");
+        return;
+    }
+    let now = now_secs();
+    if now > req.expires_at {
+        return;
+    }
+    // The request names a key; the sender must prove it is theirs.
+    let bound = match slsk_link::known_link(&app, &from) {
+        Some(l) if l.persona_key == b58(&req.sender) => Some(l),
+        _ => match slsk_link::ask(&app, &from).await {
+            Ok(l) if l.persona_key == b58(&req.sender) => {
+                slsk_link::remember(&app, l.clone());
+                Some(l)
+            }
+            Ok(_) => {
+                log::warn!("friends: {from} proved a different key than the request names");
+                None
+            }
+            Err(e) => {
+                log::warn!("friends: could not bind {from} to the request's key: {e}");
+                None
+            }
+        },
+    };
+    let Some(link) = bound else { return };
+    let id = b58(&req.relationship_id);
+    let mut store = load(&app);
+    if store.relationships.contains_key(&id) {
+        return;
+    }
+    store.relationships.insert(
+        id,
+        Relationship {
+            username: link.username,
+            username_normalized: link.username_normalized,
+            their_key: link.persona_key,
+            my_key: b58(&me),
+            request: req,
+            request_from_me: false,
+            assertions: vec![],
+            declined_by_me: false,
+            declined_by_them: false,
+            created_at: now,
+            updated_at: now,
+        },
+    );
+    if let Err(e) = save(&app, &store) {
+        log::warn!("friends: could not store the request from {from}: {e}");
+    } else {
+        log::info!("friends: request from {from} verified and waiting");
+    }
+}
+
+async fn on_assertion(app: tauri::AppHandle, from: String, a: fr::FriendAssertion) {
+    if !fr::verify_assertion(&a) {
+        log::warn!("friends: assertion from {from} does not verify");
+        return;
+    }
+    let id = b58(&a.relationship_id);
+    let mut store = load(&app);
+    let Some(rel) = store.relationships.get_mut(&id) else {
+        log::debug!("friends: assertion from {from} for an unknown relationship");
+        return;
+    };
+    if normalize_username(&from) != rel.username_normalized
+        || b58(&a.signer) != rel.their_key
+        || b58(&a.peer) != rel.my_key
+        || a.request_hash != fr::request_hash(&rel.request)
+    {
+        log::warn!("friends: assertion from {from} does not belong to its relationship");
+        return;
+    }
+    if rel
+        .assertions
+        .iter()
+        .any(|x| x.signer == a.signer && x.seq == a.seq && x.accepted == a.accepted)
+    {
+        return;
+    }
+    let now = now_secs();
+    rel.assertions.push(a.clone());
+    rel.updated_at = now;
+    // Their acceptance of OUR request completes with our own assertion.
+    let mine_exists = rel.assertions.iter().any(|x| b58(&x.signer) == rel.my_key);
+    if a.accepted && rel.request_from_me && !mine_exists {
+        if let (Ok(me), Ok(their)) = (key_of(&rel.my_key), key_of(&rel.their_key)) {
+            match sign_assertion(
+                &app,
+                fr::FriendAssertion {
+                    relationship_id: rel.request.relationship_id,
+                    signer: me,
+                    peer: their,
+                    request_hash: fr::request_hash(&rel.request),
+                    accepted: true,
+                    seq: now,
+                    sig: vec![],
+                },
+            )
+            .await
+            {
+                Ok(mine) => {
+                    if let Ok(text) = encode(ASSERT_PREFIX, &mine) {
+                        let _ = send_pm(&app, &rel.username, &text).await;
+                    }
+                    rel.assertions.push(mine);
+                }
+                Err(e) => log::warn!("friends: could not sign our assertion: {e}"),
+            }
+        }
+    }
+    let state = view_of(&id, rel, now).state;
+    if let Err(e) = save(&app, &store) {
+        log::warn!("friends: could not store the assertion from {from}: {e}");
+    } else {
+        log::info!("friends: {from} → {state}");
+    }
+}
+
+fn on_decline(app: &tauri::AppHandle, from: &str, id: &str) {
+    let mut store = load(app);
+    let Some(rel) = store.relationships.get_mut(id) else { return };
+    if normalize_username(from) != rel.username_normalized || !rel.request_from_me {
+        return;
+    }
+    rel.declined_by_them = true;
+    rel.updated_at = now_secs();
+    let _ = save(app, &store);
+}
+
+/// The event pump hands every private message here after the link proof.
+/// True means it was ours and must not surface in the Inbox. Requests and
+/// assertions are handled on their own task (see the module note).
+pub fn intercept_pm(app: &tauri::AppHandle, from: &str, message: &str) -> bool {
+    let msg = message.trim();
+    if let Some(rest) = msg.strip_prefix(REQ_PREFIX) {
+        if let Some(req) = decode::<fr::FriendRequest>(rest) {
+            tauri::async_runtime::spawn(on_request(app.clone(), from.to_string(), req));
+        }
+        return true;
+    }
+    if let Some(rest) = msg.strip_prefix(ASSERT_PREFIX) {
+        if let Some(a) = decode::<fr::FriendAssertion>(rest) {
+            tauri::async_runtime::spawn(on_assertion(app.clone(), from.to_string(), a));
+        }
+        return true;
+    }
+    if let Some(rest) = msg.strip_prefix(DECLINE_PREFIX) {
+        on_decline(app, from, rest.trim());
+        return true;
+    }
+    false
+}
+
+// ---------------------------------------------------------------- commands
+
+#[tauri::command]
+pub fn friends_list(app: tauri::AppHandle) -> Vec<RelationshipView> {
+    list(&app)
+}
+#[tauri::command]
+pub async fn friend_request(app: tauri::AppHandle, username: String) -> Result<RelationshipView, String> {
+    request(&app, &username).await
+}
+#[tauri::command]
+pub async fn friend_accept(app: tauri::AppHandle, id: String) -> Result<RelationshipView, String> {
+    accept(&app, &id).await
+}
+#[tauri::command]
+pub async fn friend_decline(app: tauri::AppHandle, id: String) -> Result<RelationshipView, String> {
+    decline(&app, &id).await
+}
+#[tauri::command]
+pub async fn friend_remove(app: tauri::AppHandle, id: String) -> Result<RelationshipView, String> {
+    remove(&app, &id).await
+}
+#[tauri::command]
+pub fn friend_forget(app: tauri::AppHandle, id: String) -> Result<(), String> {
+    forget(&app, &id)
+}