feat(pairing): chat-native DM sender approval

Replace the file-editing onboarding workflow with a chat-native pairing flow:

- New pairing store (nanobot/pairing/store.py) persists approved senders
  and pending codes in ~/.nanobot/pairing.json.
- DM messages from unknown senders receive a short pairing code instead of
  silent denial. Group chats remain silently ignored.
- Existing allowFrom semantics are fully preserved; approved pairing users
  are merged at runtime so no config migration is needed.
- nanobot pairing list/approve/deny/revoke CLI commands for bootstrap and
  emergency management.
- /pairing slash commands intercepted in-channel so owners can approve
  senders without leaving the chat.
- is_dm flag added to BaseChannel._handle_message; Telegram, Discord and
  WebSocket updated to pass it.

Closes #3768

nanobot/channels/base.py

@@ -10,6 +10,14 @@ from loguru import logger
 
 from nanobot.bus.events import InboundMessage, OutboundMessage
 from nanobot.bus.queue import MessageBus
+from nanobot.pairing import (
+    approve_code,
+    deny_code,
+    generate_code,
+    is_approved,
+    list_pending,
+    revoke,
+)
 
 
 class BaseChannel(ABC):
@@ -176,7 +184,14 @@ class BaseChannel(ABC):
         return bool(streaming) and type(self).send_delta is not BaseChannel.send_delta
 
     def is_allowed(self, sender_id: str) -> bool:
-        """Check if *sender_id* is permitted.  Empty list → deny all; ``"*"`` → allow all."""
+        """Check if *sender_id* is permitted.
+
+        Priority:
+        1. ``allowFrom: ["*"]`` → allow all.
+        2. ``allowFrom`` list → allow if sender_id is present.
+        3. Pairing store approved list → allow if previously approved.
+        4. Otherwise deny.
+        """
         if isinstance(self.config, dict):
             if "allow_from" in self.config:
                 allow_list = self.config.get("allow_from")
@@ -184,12 +199,13 @@ class BaseChannel(ABC):
                 allow_list = self.config.get("allowFrom", [])
         else:
             allow_list = getattr(self.config, "allow_from", [])
-        if not allow_list:
-            self.logger.warning("allow_from is empty — all access denied")
-            return False
         if "*" in allow_list:
             return True
-        return str(sender_id) in allow_list
+        if str(sender_id) in allow_list:
+            return True
+        if is_approved(self.name, str(sender_id)):
+            return True
+        return False
 
     async def _handle_message(
         self,
@@ -199,11 +215,14 @@ class BaseChannel(ABC):
         media: list[str] | None = None,
         metadata: dict[str, Any] | None = None,
         session_key: str | None = None,
+        is_dm: bool = False,
     ) -> None:
         """
         Handle an incoming message from the chat platform.
 
         This method checks permissions and forwards to the bus.
+        For DM messages from unrecognised senders, a pairing code is
+        issued instead of silently dropping the message.
 
         Args:
             sender_id: The sender's identifier.
@@ -212,13 +231,39 @@ class BaseChannel(ABC):
             media: Optional list of media URLs.
             metadata: Optional channel-specific metadata.
             session_key: Optional session key override (e.g. thread-scoped sessions).
+            is_dm: Whether the message is a direct / private message.
         """
         if not self.is_allowed(sender_id):
-            self.logger.warning(
-                "Access denied for sender {}. "
-                "Add them to allowFrom list in config to grant access.",
-                sender_id,
-            )
+            if is_dm:
+                code = generate_code(self.name, str(sender_id))
+                reply = (
+                    "This assistant requires approval before it can respond.\n"
+                    f"Your pairing code is: `{code}`\n"
+                    f"Ask the owner to run: `nanobot pairing approve {code}`"
+                )
+                await self.send(
+                    OutboundMessage(
+                        channel=self.name,
+                        chat_id=str(chat_id),
+                        content=reply,
+                        metadata={"_pairing_code": code},
+                    )
+                )
+                self.logger.info(
+                    "Sent pairing code {} to sender {} in chat {}",
+                    code, sender_id, chat_id,
+                )
+            else:
+                self.logger.warning(
+                    "Access denied for sender {}. "
+                    "Add them to allowFrom list in config to grant access.",
+                    sender_id,
+                )
+            return
+
+        # Intercept /pairing slash commands before they reach the agent loop
+        if content.strip().startswith("/pairing"):
+            await self._handle_pairing_command(sender_id, chat_id, content.strip())
             return
 
         meta = metadata or {}
@@ -237,6 +282,77 @@ class BaseChannel(ABC):
 
         await self.bus.publish_inbound(msg)
 
+    async def _handle_pairing_command(
+        self, sender_id: str, chat_id: str, content: str
+    ) -> None:
+        """Execute a ``/pairing`` slash command and reply directly to the user."""
+        parts = content.split()
+        sub = parts[1] if len(parts) > 1 else "list"
+        arg = parts[2] if len(parts) > 2 else None
+
+        if sub in ("list",):
+            pending = list_pending()
+            if not pending:
+                reply = "No pending pairing requests."
+            else:
+                lines = ["Pending pairing requests:"]
+                import time
+
+                for item in pending:
+                    remaining = int(item.get("expires_at", 0) - time.time())
+                    expiry = f"{remaining}s" if remaining > 0 else "expired"
+                    lines.append(
+                        f"- `{item['code']}` | {item['channel']} | {item['sender_id']} | {expiry}"
+                    )
+                reply = "\n".join(lines)
+
+        elif sub == "approve":
+            if arg is None:
+                reply = "Usage: `/pairing approve <code>`"
+            else:
+                result = approve_code(arg)
+                if result is None:
+                    reply = f"Invalid or expired pairing code: `{arg}`"
+                else:
+                    channel, sid = result
+                    reply = (
+                        f"Approved pairing code `{arg}` — "
+                        f"{sid} can now access {channel}"
+                    )
+
+        elif sub == "deny":
+            if arg is None:
+                reply = "Usage: `/pairing deny <code>`"
+            else:
+                if deny_code(arg):
+                    reply = f"Denied pairing code `{arg}`"
+                else:
+                    reply = f"Pairing code `{arg}` not found or already expired"
+
+        elif sub == "revoke":
+            if arg is None:
+                reply = "Usage: `/pairing revoke <user_id>`"
+            else:
+                if revoke(self.name, arg):
+                    reply = f"Revoked {arg} from {self.name}"
+                else:
+                    reply = f"{arg} was not in the approved list for {self.name}"
+
+        else:
+            reply = (
+                "Unknown pairing command.\n"
+                "Usage: `/pairing [list|approve <code>|deny <code>|revoke <user_id>]`"
+            )
+
+        await self.send(
+            OutboundMessage(
+                channel=self.name,
+                chat_id=str(chat_id),
+                content=reply,
+                metadata={"_pairing_command": True},
+            )
+        )
+
     @classmethod
     def default_config(cls) -> dict[str, Any]:
         """Return default config for onboard. Override in plugins to auto-populate config.json."""

nanobot/channels/discord.py

@@ -577,6 +577,7 @@ class DiscordChannel(BaseChannel):
                 media=media_paths,
                 metadata=metadata,
                 session_key=session_key,
+                is_dm=message.guild is None,
             )
         except Exception:
             await self._clear_reactions(channel_id)

nanobot/channels/telegram.py

@@ -1011,6 +1011,7 @@ class TelegramChannel(BaseChannel):
             content=content,
             metadata=self._build_message_metadata(message, user),
             session_key=self._derive_topic_session_key(message),
+            is_dm=message.chat.type == "private",
         )
 
     async def _on_message(self, update: Update, context: ContextTypes.DEFAULT_TYPE) -> None:

nanobot/channels/websocket.py

@@ -1254,6 +1254,7 @@ class WebSocketChannel(BaseChannel):
                     chat_id=default_chat_id,
                     content=content,
                     metadata={"remote": getattr(connection, "remote_address", None)},
+                    is_dm=True,
                 )
         except Exception as e:
             self.logger.debug("connection ended: {}", e)
@@ -1399,6 +1400,7 @@ class WebSocketChannel(BaseChannel):
                 content=content,
                 media=media_paths or None,
                 metadata=metadata,
+                is_dm=True,
             )
             return
         await self._send_event(connection, "error", detail=f"unknown type: {t!r}")

nanobot/cli/commands.py

@@ -1620,5 +1620,94 @@ def _login_github_copilot() -> None:
         raise typer.Exit(1)
 
 
+# ============================================================================
+# Pairing Commands
+# ============================================================================
+
+pairing_app = typer.Typer(help="Manage DM pairing approvals")
+app.add_typer(pairing_app, name="pairing")
+
+
+@pairing_app.command("list")
+def pairing_list():
+    """Show pending pairing requests."""
+    from nanobot.pairing import list_pending
+
+    pending = list_pending()
+    if not pending:
+        console.print("[dim]No pending pairing requests.[/dim]")
+        return
+
+    table = Table(title="Pending Pairing Requests")
+    table.add_column("Code", style="cyan")
+    table.add_column("Channel", style="magenta")
+    table.add_column("Sender ID", style="yellow")
+    table.add_column("Expires", style="green")
+
+    import time
+
+    for item in pending:
+        remaining = int(item.get("expires_at", 0) - time.time())
+        expiry = f"{remaining}s" if remaining > 0 else "expired"
+        table.add_row(
+            item["code"],
+            item["channel"],
+            item["sender_id"],
+            expiry,
+        )
+
+    console.print(table)
+
+
+@pairing_app.command("approve")
+def pairing_approve(
+    code: str = typer.Argument(..., help="Pairing code to approve"),
+):
+    """Approve a pending pairing code."""
+    from nanobot.pairing import approve_code
+
+    result = approve_code(code)
+    if result is None:
+        console.print(f"[red]✗[/red] Invalid or expired pairing code: {code}")
+        raise typer.Exit(1)
+
+    channel, sender_id = result
+    console.print(
+        f"[green]✓[/green] Approved pairing code {code} — "
+        f"{sender_id} can now access {channel}"
+    )
+
+
+@pairing_app.command("deny")
+def pairing_deny(
+    code: str = typer.Argument(..., help="Pairing code to deny"),
+):
+    """Deny and discard a pending pairing code."""
+    from nanobot.pairing import deny_code
+
+    if deny_code(code):
+        console.print(f"[green]✓[/green] Denied pairing code {code}")
+    else:
+        console.print(f"[yellow]! Pairing code {code} not found or already expired[/yellow]")
+
+
+@pairing_app.command("revoke")
+def pairing_revoke(
+    channel: str = typer.Argument(..., help="Channel name (e.g. telegram)"),
+    user_id: str = typer.Argument(..., help="User ID to revoke"),
+):
+    """Revoke an approved sender from a channel."""
+    from nanobot.pairing import revoke
+
+    if revoke(channel, user_id):
+        console.print(
+            f"[green]✓[/green] Revoked {user_id} from {channel}"
+        )
+    else:
+        console.print(
+            f"[yellow]! {user_id} was not in the approved list for {channel}[/yellow]"
+        )
+
+
 if __name__ == "__main__":
     app()

nanobot/pairing/__init__.py

@@ -0,0 +1,21 @@
+"""Pairing module for DM sender approval."""
+
+from nanobot.pairing.store import (
+    approve_code,
+    deny_code,
+    generate_code,
+    get_approved,
+    is_approved,
+    list_pending,
+    revoke,
+)
+
+__all__ = [
+    "approve_code",
+    "deny_code",
+    "generate_code",
+    "get_approved",
+    "is_approved",
+    "list_pending",
+    "revoke",
+]

nanobot/pairing/store.py

@@ -0,0 +1,175 @@
+"""Pairing store for DM sender approval.
+
+Persistent storage at ``~/.nanobot/pairing.json`` keeps approved senders
+and pending pairing codes per channel.  The store is designed for
+private-assistant scale: small JSON file, simple locking, no external DB.
+"""
+
+from __future__ import annotations
+
+import json
+import secrets
+import string
+import threading
+import time
+from pathlib import Path
+from typing import Any
+
+from loguru import logger
+
+from nanobot.config.paths import get_data_dir
+
+_LOCK = threading.Lock()
+_ALPHABET = string.ascii_uppercase + string.digits
+_CODE_LENGTH = 6  # e.g. XK9-42F
+_TTL_DEFAULT_S = 600  # 10 minutes
+
+
+def _store_path() -> Path:
+    return get_data_dir() / "pairing.json"
+
+
+def _load() -> dict[str, Any]:
+    path = _store_path()
+    if not path.exists():
+        return {"approved": {}, "pending": {}}
+    try:
+        with open(path, encoding="utf-8") as f:
+            return json.load(f)
+    except (json.JSONDecodeError, OSError):
+        logger.warning("Corrupted pairing store, resetting")
+        return {"approved": {}, "pending": {}}
+
+
+def _save(data: dict[str, Any]) -> None:
+    path = _store_path()
+    path.parent.mkdir(parents=True, exist_ok=True)
+    tmp = path.with_suffix(".tmp")
+    with open(tmp, "w", encoding="utf-8") as f:
+        json.dump(data, f, indent=2, ensure_ascii=False)
+        f.flush()
+    tmp.replace(path)
+
+
+def _gc_pending(data: dict[str, Any]) -> None:
+    """Remove expired pending entries in-place."""
+    now = time.time()
+    pending: dict[str, Any] = data.get("pending", {})
+    expired = [code for code, info in pending.items() if info.get("expires_at", 0) < now]
+    for code in expired:
+        del pending[code]
+
+
+def generate_code(
+    channel: str,
+    sender_id: str,
+    ttl: int = _TTL_DEFAULT_S,
+) -> str:
+    """Create a new pairing code for *sender_id* on *channel*.
+
+    Returns the code (e.g. ``"XK9-42F"``).
+    """
+    with _LOCK:
+        data = _load()
+        _gc_pending(data)
+        # Ensure uniqueness
+        for _ in range(100):
+            raw = "".join(secrets.choice(_ALPHABET) for _ in range(_CODE_LENGTH))
+            code = f"{raw[:3]}-{raw[3:]}"
+            if code not in data.get("pending", {}):
+                break
+        else:  # pragma: no cover
+            raise RuntimeError("Failed to generate unique pairing code")
+
+        data.setdefault("pending", {})[code] = {
+            "channel": channel,
+            "sender_id": sender_id,
+            "created_at": time.time(),
+            "expires_at": time.time() + ttl,
+        }
+        _save(data)
+        logger.info("Generated pairing code {} for {}@{}", code, sender_id, channel)
+        return code
+
+
+def approve_code(code: str) -> tuple[str, str] | None:
+    """Approve a pending pairing code.
+
+    Returns ``(channel, sender_id)`` on success, or ``None`` if the code
+    does not exist or has expired.
+    """
+    with _LOCK:
+        data = _load()
+        _gc_pending(data)
+        pending: dict[str, Any] = data.get("pending", {})
+        info = pending.pop(code, None)
+        if info is None:
+            return None
+        channel = info["channel"]
+        sender_id = info["sender_id"]
+        data.setdefault("approved", {}).setdefault(channel, []).append(sender_id)
+        _save(data)
+        logger.info("Approved pairing code {} for {}@{}", code, sender_id, channel)
+        return channel, sender_id
+
+
+def deny_code(code: str) -> bool:
+    """Reject and discard a pending pairing code.
+
+    Returns ``True`` if the code existed and was removed.
+    """
+    with _LOCK:
+        data = _load()
+        _gc_pending(data)
+        pending: dict[str, Any] = data.get("pending", {})
+        if code in pending:
+            del pending[code]
+            _save(data)
+            logger.info("Denied pairing code {}", code)
+            return True
+        return False
+
+
+def is_approved(channel: str, sender_id: str) -> bool:
+    """Check whether *sender_id* has been approved on *channel*."""
+    with _LOCK:
+        data = _load()
+        approved: dict[str, list[str]] = data.get("approved", {})
+        return str(sender_id) in approved.get(channel, [])
+
+
+def list_pending() -> list[dict[str, Any]]:
+    """Return all non-expired pending pairing requests."""
+    with _LOCK:
+        data = _load()
+        _gc_pending(data)
+        return [
+            {"code": code, **info}
+            for code, info in data.get("pending", {}).items()
+        ]
+
+
+def revoke(channel: str, sender_id: str) -> bool:
+    """Remove an approved sender from *channel*.
+
+    Returns ``True`` if the sender was present and removed.
+    """
+    with _LOCK:
+        data = _load()
+        approved: dict[str, list[str]] = data.get("approved", {})
+        lst = approved.get(channel, [])
+        if sender_id in lst:
+            lst.remove(sender_id)
+            if not lst:
+                del approved[channel]
+            _save(data)
+            logger.info("Revoked {} from {}", sender_id, channel)
+            return True
+        return False
+
+
+def get_approved(channel: str) -> list[str]:
+    """Return all approved sender IDs for *channel*."""
+    with _LOCK:
+        data = _load()
+        return list(data.get("approved", {}).get(channel, []))