Implement live gossip federation server (5 phases)

Phase 1: RFC 6962 consistency proofs in merkle.py
- Implemented _build_consistency_proof() with recursive subtree
  decomposition algorithm following RFC 6962 Section 2.1.2
- Added _subproof() recursive helper and _compute_root_of()
- Added standalone verify_consistency_proof() function

Phase 2: Federation API endpoints on FastAPI server
- GET /federation/status — merkle root + log size for gossip probes
- GET /federation/records?start=N&count=M — record fetch (cap 100)
- GET /federation/consistency-proof?old_size=N — Merkle proof
- POST /federation/records — accept records with trust filtering
  and SHA-256 deduplication
- Cached storage singleton for concurrent safety
- Added FEDERATION_DIR to paths.py

Phase 3: HttpTransport implementation
- Replaced stub with real aiohttp client (lazy import for optional dep)
- Reusable ClientSession with configurable timeout
- All 4 PeerTransport methods: get_status, get_records,
  get_consistency_proof, push_records
- FederationError wrapping for all network failures
- Added record_filter callback to GossipNode for trust-store filtering

Phase 4: Peer persistence (SQLite)
- New peer_store.py: SQLite-backed peer database + sync history
- Tables: peers (url, fingerprint, health, last_seen) and
  sync_history (timestamp, records_received, success/error)
- PeerStore follows dropbox.py SQLite pattern

Phase 5: CLI commands + Web UI dashboard
- CLI: federation status, peer-add, peer-remove, peer-list,
  sync-now (asyncio), history
- Flask blueprint at /federation/ with peer table, sync history,
  add/remove peer forms, local node info cards
- CSRF tokens on all forms

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontends/web/app.py

@@ -116,8 +116,10 @@ def create_app(config: SoosefConfig | None = None) -> Flask:
     app.register_blueprint(keys_bp)
 
     from frontends.web.blueprints.dropbox import bp as dropbox_bp
+    from frontends.web.blueprints.federation import bp as federation_bp
 
     app.register_blueprint(dropbox_bp)
+    app.register_blueprint(federation_bp)
 
     # Exempt drop box upload from CSRF (sources don't have sessions)
     csrf.exempt(dropbox_bp)

frontends/web/blueprints/federation.py

@@ -0,0 +1,78 @@
+"""
+Federation blueprint — peer status dashboard and management.
+"""
+
+from auth import admin_required, login_required
+from flask import Blueprint, flash, redirect, render_template, request, url_for
+
+bp = Blueprint("federation", __name__, url_prefix="/federation")
+
+
+@bp.route("/")
+@login_required
+def status():
+    """Federation status dashboard."""
+    from soosef.verisoo.peer_store import PeerStore
+
+    store = PeerStore()
+    peers = store.list_peers()
+    history = store.get_sync_history(limit=20)
+
+    # Get local node info
+    node_info = {"root": None, "size": 0}
+    try:
+        from soosef.verisoo.storage import LocalStorage
+
+        import soosef.paths as _paths
+
+        storage = LocalStorage(_paths.ATTESTATIONS_DIR)
+        stats = storage.get_stats()
+        merkle_log = storage.load_merkle_log()
+        node_info = {
+            "root": merkle_log.root_hash[:16] + "..." if merkle_log.root_hash else "empty",
+            "size": merkle_log.size,
+            "record_count": stats.record_count,
+        }
+    except Exception:
+        pass
+
+    return render_template(
+        "federation/status.html",
+        peers=peers,
+        history=history,
+        node_info=node_info,
+    )
+
+
+@bp.route("/peer/add", methods=["POST"])
+@admin_required
+def peer_add():
+    """Add a federation peer."""
+    from soosef.verisoo.peer_store import PeerStore
+
+    url = request.form.get("url", "").strip()
+    fingerprint = request.form.get("fingerprint", "").strip()
+
+    if not url or not fingerprint:
+        flash("URL and fingerprint are required.", "error")
+        return redirect(url_for("federation.status"))
+
+    store = PeerStore()
+    store.add_peer(url, fingerprint)
+    flash(f"Peer added: {url}", "success")
+    return redirect(url_for("federation.status"))
+
+
+@bp.route("/peer/remove", methods=["POST"])
+@admin_required
+def peer_remove():
+    """Remove a federation peer."""
+    from soosef.verisoo.peer_store import PeerStore
+
+    url = request.form.get("url", "").strip()
+    store = PeerStore()
+    if store.remove_peer(url):
+        flash(f"Peer removed: {url}", "success")
+    else:
+        flash(f"Peer not found: {url}", "error")
+    return redirect(url_for("federation.status"))

frontends/web/templates/federation/status.html

@@ -0,0 +1,108 @@
+{% extends "base.html" %}
+{% block title %}Federation — SooSeF{% endblock %}
+{% block content %}
+<h2><i class="bi bi-diagram-3 me-2"></i>Federation</h2>
+<p class="text-muted">Gossip-based attestation sync between SooSeF instances.</p>
+
+<div class="row mb-4">
+    <div class="col-md-4">
+        <div class="card bg-dark">
+            <div class="card-body">
+                <h6 class="card-subtitle text-muted">Local Node</h6>
+                <p class="mb-1">Records: <strong>{{ node_info.size }}</strong></p>
+                <p class="mb-0 text-muted small">Root: {{ node_info.root }}</p>
+            </div>
+        </div>
+    </div>
+    <div class="col-md-4">
+        <div class="card bg-dark">
+            <div class="card-body">
+                <h6 class="card-subtitle text-muted">Peers</h6>
+                <p class="mb-0"><strong>{{ peers|length }}</strong> configured</p>
+            </div>
+        </div>
+    </div>
+    <div class="col-md-4">
+        <div class="card bg-dark">
+            <div class="card-body">
+                <h6 class="card-subtitle text-muted">Last Sync</h6>
+                {% if history %}
+                <p class="mb-0">{{ history[0].synced_at[:16] }}</p>
+                {% else %}
+                <p class="mb-0 text-muted">Never</p>
+                {% endif %}
+            </div>
+        </div>
+    </div>
+</div>
+
+<h5>Peers</h5>
+{% if peers %}
+<table class="table table-dark table-sm">
+    <thead>
+        <tr><th>URL</th><th>Fingerprint</th><th>Records</th><th>Health</th><th>Last Seen</th><th></th></tr>
+    </thead>
+    <tbody>
+        {% for p in peers %}
+        <tr>
+            <td><code>{{ p.url }}</code></td>
+            <td><code>{{ p.fingerprint[:16] }}...</code></td>
+            <td>{{ p.last_size }}</td>
+            <td>{% if p.healthy %}<span class="text-success">OK</span>{% else %}<span class="text-danger">DOWN</span>{% endif %}</td>
+            <td>{{ p.last_seen.strftime('%Y-%m-%d %H:%M') if p.last_seen else 'Never' }}</td>
+            <td>
+                <form method="POST" action="{{ url_for('federation.peer_remove') }}" class="d-inline">
+                    <input type="hidden" name="csrf_token" value="{{ csrf_token() }}"/>
+                    <input type="hidden" name="url" value="{{ p.url }}">
+                    <button type="submit" class="btn btn-sm btn-outline-danger" title="Remove">
+                        <i class="bi bi-trash"></i>
+                    </button>
+                </form>
+            </td>
+        </tr>
+        {% endfor %}
+    </tbody>
+</table>
+{% else %}
+<p class="text-muted">No peers configured. Add one below.</p>
+{% endif %}
+
+<div class="card bg-dark mb-4">
+    <div class="card-body">
+        <h6 class="card-title">Add Peer</h6>
+        <form method="POST" action="{{ url_for('federation.peer_add') }}">
+            <input type="hidden" name="csrf_token" value="{{ csrf_token() }}"/>
+            <div class="row g-2">
+                <div class="col-md-5">
+                    <input type="url" name="url" class="form-control bg-dark text-light" placeholder="https://peer:8000" required>
+                </div>
+                <div class="col-md-5">
+                    <input type="text" name="fingerprint" class="form-control bg-dark text-light" placeholder="Ed25519 fingerprint" required>
+                </div>
+                <div class="col-md-2">
+                    <button type="submit" class="btn btn-primary w-100">Add</button>
+                </div>
+            </div>
+        </form>
+    </div>
+</div>
+
+{% if history %}
+<h5>Sync History</h5>
+<table class="table table-dark table-sm">
+    <thead>
+        <tr><th>Time</th><th>Peer</th><th>Records</th><th>Status</th></tr>
+    </thead>
+    <tbody>
+        {% for h in history %}
+        <tr>
+            <td>{{ h.synced_at[:19] }}</td>
+            <td><code>{{ h.peer_url[:30] }}</code></td>
+            <td>+{{ h.records_received }}</td>
+            <td>{% if h.success %}<span class="text-success">OK</span>{% else %}<span class="text-danger">{{ h.error[:40] if h.error else 'Failed' }}</span>{% endif %}</td>
+        </tr>
+        {% endfor %}
+    </tbody>
+</table>
+{% endif %}
+{% endblock %}