feat: Phase 12 — P2P crypto material, password split, node Ed25519 auth

Baseline commit capturing in-progress Phase 12 work that was already present
in the working tree (uncommitted) before the Phase 11.5 security remediation
begins. Committed as-is, without review or modification, so that remediation
changes arrive as a separable diff.

Contents: BundleStore (P2P GEK + keypair bundles), password split
(auth_key / bundle_key), node Ed25519 auth (POST /v1/nodes/auth, node-scoped
JWT), GEK-HMAC handshake proof with DTLS channel binding, Ed25519 admin
challenge-response, node local admin UI rewrite, browser key persistence.

Not authored in this session — captured to establish a baseline.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 70 insertions, 1 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/api/nodes.py b/packages/meshbay-hub/src/meshbay_hub/api/nodes.py
index b970aa8..321e43c 100644
--- a/packages/meshbay-hub/src/meshbay_hub/api/nodes.py
+++ b/packages/meshbay-hub/src/meshbay_hub/api/nodes.py
@@ -1,15 +1,84 @@
 """Node endpoints — /v1/nodes/*"""
 
+import base64
+import time
+
+from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PublicKey
+from cryptography.exceptions import InvalidSignature
 from fastapi import APIRouter, Depends, HTTPException, Request
 from pydantic import BaseModel
+from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from meshbay_hub.auth import issue_access_token
 from meshbay_hub.api.deps import get_current_user
+from meshbay_hub.api.middleware import limiter
 from meshbay_hub.db.engine import get_db
-from meshbay_hub.db.models import IPLog, Node, User
+from meshbay_hub.db.models import GroupMember, IPLog, Node, User
 
 router = APIRouter(prefix="/v1/nodes", tags=["nodes"])
 
+NODE_AUTH_TIMESTAMP_WINDOW = 60  # seconds
+
+
+class NodeAuthRequest(BaseModel):
+    username:  str
+    timestamp: int       # unix epoch seconds
+    signature: str       # base64 Ed25519 signature
+
+
+@router.post("/auth")
+@limiter.limit("10/minute")
+async def node_auth(
+    body: NodeAuthRequest,
+    request: Request,
+    db: AsyncSession = Depends(get_db),
+):
+    """Authenticate a node daemon via Ed25519 challenge-response. Returns node-scoped JWT."""
+    now = int(time.time())
+    if abs(now - body.timestamp) > NODE_AUTH_TIMESTAMP_WINDOW:
+        raise HTTPException(status_code=401, detail="Timestamp too old or too far in the future")
+
+    result = await db.execute(select(User).where(User.username == body.username))
+    user = result.scalar_one_or_none()
+    if not user:
+        raise HTTPException(status_code=401, detail="Invalid credentials")
+    if user.status != "active":
+        raise HTTPException(status_code=403, detail=f"Account {user.status}")
+
+    if not user.pk_node_ed25519:
+        raise HTTPException(
+            status_code=401,
+            detail="No node key registered — link your node from the browser first",
+        )
+
+    message = f"meshbay:node_auth:{body.username}:{body.timestamp}".encode()
+    try:
+        pk_raw = base64.b64decode(user.pk_node_ed25519)
+        pk = Ed25519PublicKey.from_public_bytes(pk_raw)
+        sig = base64.b64decode(body.signature)
+        pk.verify(sig, message)
+    except (InvalidSignature, Exception):
+        db.add(IPLog(event="node_auth_fail", ip_address=_ip(request), detail=body.username))
+        await db.commit()
+        raise HTTPException(status_code=401, detail="Invalid signature")
+
+    memberships = await db.execute(
+        select(GroupMember.group_id).where(GroupMember.user_id == user.id))
+    group_ids = [gid for (gid,) in memberships.all()]
+
+    access_token = issue_access_token(
+        user.id, user.pk_node_ed25519, ttl=3600, groups=group_ids, scope="node")
+
+    db.add(IPLog(user_id=user.id, event="node_auth", ip_address=_ip(request)))
+    await db.commit()
+
+    return {
+        "access_token": access_token,
+        "token_type":   "bearer",
+        "expires_in":   3600,
+    }
+
 
 class NodeAnnounceRequest(BaseModel):
     pk_node:       str