Hermes-agent

gateway/pairing.py

@@ -0,0 +1,450 @@
+"""
+DM Pairing System
+
+Code-based approval flow for authorizing new users on messaging platforms.
+Instead of static allowlists with user IDs, unknown users receive a one-time
+pairing code that the bot owner approves via the CLI.
+
+Security features (based on OWASP + NIST SP 800-63-4 guidance):
+  - 8-char codes from 32-char unambiguous alphabet (no 0/O/1/I)
+  - Cryptographic randomness via secrets.choice()
+  - 1-hour code expiry
+  - Max 3 pending codes per platform
+  - Rate limiting: 1 request per user per 10 minutes
+  - Lockout after 5 failed approval attempts (1 hour)
+  - File permissions: chmod 0600 on all data files
+  - Codes are never logged to stdout
+
+Storage: ~/.hermes/pairing/
+"""
+
+import hashlib
+import json
+import os
+import secrets
+import tempfile
+import threading
+import time
+from pathlib import Path
+from typing import Optional
+
+from gateway.whatsapp_identity import (
+    expand_whatsapp_aliases,
+    normalize_whatsapp_identifier,
+)
+from hermes_constants import get_hermes_dir
+from utils import atomic_replace
+
+
+# Unambiguous alphabet -- excludes 0/O, 1/I to prevent confusion
+ALPHABET = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789"
+CODE_LENGTH = 8
+
+# Timing constants
+CODE_TTL_SECONDS = 3600             # Codes expire after 1 hour
+RATE_LIMIT_SECONDS = 600            # 1 request per user per 10 minutes
+LOCKOUT_SECONDS = 3600              # Lockout duration after too many failures
+
+# Limits
+MAX_PENDING_PER_PLATFORM = 3        # Max pending codes per platform
+MAX_FAILED_ATTEMPTS = 5             # Failed approvals before lockout
+
+PAIRING_DIR = get_hermes_dir("platforms/pairing", "pairing")
+
+
+def _secure_write(path: Path, data: str) -> None:
+    """Write data to file with restrictive permissions (owner read/write only).
+
+    Uses a temp-file + atomic rename so readers always see either the old
+    complete file or the new one — never a partial write.
+    """
+    path.parent.mkdir(parents=True, exist_ok=True)
+    fd, tmp_path = tempfile.mkstemp(dir=str(path.parent), suffix=".tmp")
+    try:
+        with os.fdopen(fd, "w", encoding="utf-8") as f:
+            f.write(data)
+            f.flush()
+            os.fsync(f.fileno())
+        atomic_replace(tmp_path, path)
+        try:
+            os.chmod(path, 0o600)
+        except OSError:
+            pass  # Windows doesn't support chmod the same way
+    except BaseException:
+        try:
+            os.unlink(tmp_path)
+        except OSError:
+            pass
+        raise
+
+
+class PairingStore:
+    """
+    Manages pairing codes and approved user lists.
+
+    Data files per platform:
+      - {platform}-pending.json   : pending pairing requests
+      - {platform}-approved.json  : approved (paired) users
+      - _rate_limits.json         : rate limit tracking
+    """
+
+    def __init__(self):
+        PAIRING_DIR.mkdir(parents=True, exist_ok=True)
+        # Protects all read-modify-write cycles. The gateway runs multiple
+        # platform adapters concurrently in threads sharing one PairingStore.
+        self._lock = threading.RLock()
+
+    def _pending_path(self, platform: str) -> Path:
+        return PAIRING_DIR / f"{platform}-pending.json"
+
+    def _approved_path(self, platform: str) -> Path:
+        return PAIRING_DIR / f"{platform}-approved.json"
+
+    def _rate_limit_path(self) -> Path:
+        return PAIRING_DIR / "_rate_limits.json"
+
+    def _load_json(self, path: Path) -> dict:
+        if path.exists():
+            try:
+                return json.loads(path.read_text(encoding="utf-8"))
+            except (json.JSONDecodeError, OSError):
+                return {}
+        return {}
+
+    def _save_json(self, path: Path, data: dict) -> None:
+        _secure_write(path, json.dumps(data, indent=2, ensure_ascii=False))
+
+    def _normalize_user_id(self, platform: str, user_id: str) -> str:
+        """Normalize platform-specific user IDs before persisting them."""
+        raw_user_id = str(user_id or "").strip()
+        if platform == "whatsapp":
+            return normalize_whatsapp_identifier(raw_user_id) or raw_user_id
+        return raw_user_id
+
+    def _user_id_aliases(self, platform: str, user_id: str) -> set[str]:
+        """Return all known equivalent user IDs for auth/rate-limit checks."""
+        raw_user_id = str(user_id or "").strip()
+        if not raw_user_id:
+            return set()
+
+        aliases = {raw_user_id, self._normalize_user_id(platform, raw_user_id)}
+        if platform == "whatsapp":
+            aliases.update(expand_whatsapp_aliases(raw_user_id))
+        aliases.discard("")
+        return aliases
+
+    def _user_ids_match(self, platform: str, left: str, right: str) -> bool:
+        """Return True when two user IDs represent the same principal."""
+        left_aliases = self._user_id_aliases(platform, left)
+        right_aliases = self._user_id_aliases(platform, right)
+        return bool(left_aliases and right_aliases and (left_aliases & right_aliases))
+
+    # ----- Approved users -----
+
+    def is_approved(self, platform: str, user_id: str) -> bool:
+        """Check if a user is approved (paired) on a platform."""
+        approved = self._load_json(self._approved_path(platform))
+        for approved_user_id in approved:
+            if self._user_ids_match(platform, approved_user_id, user_id):
+                return True
+        return False
+
+    def list_approved(self, platform: str = None) -> list:
+        """List approved users, optionally filtered by platform."""
+        results = []
+        platforms = [platform] if platform else self._all_platforms("approved")
+        for p in platforms:
+            approved = self._load_json(self._approved_path(p))
+            for uid, info in approved.items():
+                results.append({"platform": p, "user_id": uid, **info})
+        return results
+
+    def _approve_user(self, platform: str, user_id: str, user_name: str = "") -> None:
+        """Add a user to the approved list. Must be called under self._lock."""
+        approved = self._load_json(self._approved_path(platform))
+        normalized_user_id = self._normalize_user_id(platform, user_id)
+        duplicate_ids = [
+            approved_user_id
+            for approved_user_id in approved
+            if self._user_ids_match(platform, approved_user_id, normalized_user_id)
+        ]
+        for approved_user_id in duplicate_ids:
+            del approved[approved_user_id]
+
+        approved[normalized_user_id] = {
+            "user_name": user_name,
+            "approved_at": time.time(),
+        }
+        self._save_json(self._approved_path(platform), approved)
+
+    def revoke(self, platform: str, user_id: str) -> bool:
+        """Remove a user from the approved list. Returns True if found."""
+        path = self._approved_path(platform)
+        with self._lock:
+            approved = self._load_json(path)
+            matching_ids = [
+                approved_user_id
+                for approved_user_id in approved
+                if self._user_ids_match(platform, approved_user_id, user_id)
+            ]
+            if matching_ids:
+                for approved_user_id in matching_ids:
+                    del approved[approved_user_id]
+                self._save_json(path, approved)
+                return True
+        return False
+
+    # ----- Pending codes -----
+
+    @staticmethod
+    def _hash_code(code: str, salt: bytes) -> str:
+        """Hash a pairing code with the given salt using SHA-256."""
+        return hashlib.sha256(salt + code.encode("utf-8")).hexdigest()
+
+    def generate_code(
+        self, platform: str, user_id: str, user_name: str = ""
+    ) -> Optional[str]:
+        """
+        Generate a pairing code for a new user.
+
+        Returns the code string, or None if:
+          - User is rate-limited (too recent request)
+          - Max pending codes reached for this platform
+          - User/platform is in lockout due to failed attempts
+
+        The code is NOT stored in plaintext.  Only a salted SHA-256 hash is
+        persisted so that reading the pending file does not reveal codes.
+        """
+        with self._lock:
+            self._cleanup_expired(platform)
+            normalized_user_id = self._normalize_user_id(platform, user_id)
+
+            # Check lockout
+            if self._is_locked_out(platform):
+                return None
+
+            # Check rate limit for this specific user
+            if self._is_rate_limited(platform, user_id):
+                return None
+
+            # Check max pending
+            pending = self._load_json(self._pending_path(platform))
+            if len(pending) >= MAX_PENDING_PER_PLATFORM:
+                return None
+
+            # Generate cryptographically random code
+            code = "".join(secrets.choice(ALPHABET) for _ in range(CODE_LENGTH))
+
+            # Hash the code with a random salt before storing
+            salt = os.urandom(16)
+            code_hash = self._hash_code(code, salt)
+
+            # Use a unique entry id as the key (not the code itself)
+            entry_id = secrets.token_hex(8)
+
+            # Store pending request with hashed code
+            pending[entry_id] = {
+                "hash": code_hash,
+                "salt": salt.hex(),
+                "user_id": normalized_user_id,
+                "user_name": user_name,
+                "created_at": time.time(),
+            }
+            self._save_json(self._pending_path(platform), pending)
+
+            # Record rate limit
+            self._record_rate_limit(platform, user_id)
+
+            return code
+
+    def approve_code(self, platform: str, code: str) -> Optional[dict]:
+        """
+        Approve a pairing code. Adds the user to the approved list.
+
+        Returns ``{user_id, user_name}`` on success, ``None`` if the code is
+        invalid/expired OR the platform is currently locked out after
+        ``MAX_FAILED_ATTEMPTS`` failed approvals (#10195). Callers can
+        disambiguate with ``_is_locked_out(platform)``.
+
+        Verification: the user-provided code is hashed with each stored
+        entry's salt and compared to the stored hash using constant-time
+        comparison. Pre-hash entries (legacy plaintext-key format from
+        pre-upgrade pending.json files) are silently ignored — they get
+        pruned at TTL by ``_cleanup_expired``.
+        """
+        with self._lock:
+            self._cleanup_expired(platform)
+            code = code.upper().strip()
+
+            # Lockout check — must run before the pending lookup so a
+            # valid code (e.g. one already sitting in pending) cannot be
+            # accepted once the lockout fires. Without this, the lockout
+            # only blocks `generate_code`, not `approve_code` — nullifying
+            # the brute-force protection for any code already issued.
+            if self._is_locked_out(platform):
+                return None
+
+            pending = self._load_json(self._pending_path(platform))
+
+            # Find the entry whose hash matches the provided code.
+            # Tolerate legacy plaintext-key entries (no salt/hash) and
+            # malformed entries — skip them rather than KeyError, so an
+            # in-place upgrade across an existing pending.json doesn't
+            # crash on the first approve call. Legacy entries get pruned
+            # at their TTL by _cleanup_expired.
+            matched_key = None
+            matched_entry = None
+            for entry_id, entry in pending.items():
+                if not isinstance(entry, dict):
+                    continue
+                if "salt" not in entry or "hash" not in entry:
+                    continue
+                try:
+                    salt = bytes.fromhex(entry["salt"])
+                except ValueError:
+                    continue
+                candidate_hash = self._hash_code(code, salt)
+                if secrets.compare_digest(candidate_hash, entry["hash"]):
+                    matched_key = entry_id
+                    matched_entry = entry
+                    break
+
+            if matched_key is None:
+                self._record_failed_attempt(platform)
+                return None
+
+            del pending[matched_key]
+            self._save_json(self._pending_path(platform), pending)
+
+            # Add to approved list
+            self._approve_user(platform, matched_entry["user_id"],
+                               matched_entry.get("user_name", ""))
+
+            return {
+                "user_id": matched_entry["user_id"],
+                "user_name": matched_entry.get("user_name", ""),
+            }
+
+    def list_pending(self, platform: str = None) -> list:
+        """List pending pairing requests, optionally filtered by platform.
+
+        Codes are stored hashed — the ``code`` field is replaced with the
+        first 8 hex characters of the hash so admins can distinguish entries
+        without revealing the original code. Legacy plaintext-key entries
+        (pre-hash format) are shown with a "legacy" placeholder so admins
+        can see them age out without crashing on a missing ``hash`` field.
+        """
+        results = []
+        with self._lock:
+            platforms = [platform] if platform else self._all_platforms("pending")
+            for p in platforms:
+                self._cleanup_expired(p)
+                pending = self._load_json(self._pending_path(p))
+                for entry_id, info in pending.items():
+                    if not isinstance(info, dict):
+                        continue
+                    created_at = info.get("created_at")
+                    if not isinstance(created_at, (int, float)):
+                        continue
+                    age_min = int((time.time() - created_at) / 60)
+                    hash_val = info.get("hash")
+                    code_display = hash_val[:8] if isinstance(hash_val, str) else "legacy"
+                    results.append({
+                        "platform": p,
+                        "code": code_display,
+                        "user_id": info.get("user_id", ""),
+                        "user_name": info.get("user_name", ""),
+                        "age_minutes": age_min,
+                    })
+        return results
+
+    def clear_pending(self, platform: str = None) -> int:
+        """Clear all pending requests. Returns count removed."""
+        with self._lock:
+            count = 0
+            platforms = [platform] if platform else self._all_platforms("pending")
+            for p in platforms:
+                pending = self._load_json(self._pending_path(p))
+                count += len(pending)
+                self._save_json(self._pending_path(p), {})
+        return count
+
+    # ----- Rate limiting and lockout -----
+
+    def _is_rate_limited(self, platform: str, user_id: str) -> bool:
+        """Check if a user has requested a code too recently."""
+        limits = self._load_json(self._rate_limit_path())
+        for alias in self._user_id_aliases(platform, user_id):
+            key = f"{platform}:{alias}"
+            last_request = limits.get(key, 0)
+            if (time.time() - last_request) < RATE_LIMIT_SECONDS:
+                return True
+        return False
+
+    def _record_rate_limit(self, platform: str, user_id: str) -> None:
+        """Record the time of a pairing request for rate limiting."""
+        limits = self._load_json(self._rate_limit_path())
+        now = time.time()
+        for alias in self._user_id_aliases(platform, user_id):
+            key = f"{platform}:{alias}"
+            limits[key] = now
+        self._save_json(self._rate_limit_path(), limits)
+
+    def _is_locked_out(self, platform: str) -> bool:
+        """Check if a platform is in lockout due to failed approval attempts."""
+        limits = self._load_json(self._rate_limit_path())
+        lockout_key = f"_lockout:{platform}"
+        lockout_until = limits.get(lockout_key, 0)
+        return time.time() < lockout_until
+
+    def _record_failed_attempt(self, platform: str) -> None:
+        """Record a failed approval attempt. Triggers lockout after MAX_FAILED_ATTEMPTS."""
+        limits = self._load_json(self._rate_limit_path())
+        fail_key = f"_failures:{platform}"
+        fails = limits.get(fail_key, 0) + 1
+        limits[fail_key] = fails
+        if fails >= MAX_FAILED_ATTEMPTS:
+            lockout_key = f"_lockout:{platform}"
+            limits[lockout_key] = time.time() + LOCKOUT_SECONDS
+            limits[fail_key] = 0  # Reset counter
+            print(f"[pairing] Platform {platform} locked out for {LOCKOUT_SECONDS}s "
+                  f"after {MAX_FAILED_ATTEMPTS} failed attempts", flush=True)
+        self._save_json(self._rate_limit_path(), limits)
+
+    # ----- Cleanup -----
+
+    def _cleanup_expired(self, platform: str) -> None:
+        """Remove expired pending codes.
+
+        Tolerant of malformed / legacy entries — anything without a numeric
+        ``created_at`` is treated as expired (it's effectively unusable
+        with the new hash-keyed schema anyway).
+        """
+        path = self._pending_path(platform)
+        pending = self._load_json(path)
+        now = time.time()
+        expired = []
+        for entry_id, info in pending.items():
+            if not isinstance(info, dict):
+                expired.append(entry_id)
+                continue
+            created_at = info.get("created_at")
+            if not isinstance(created_at, (int, float)):
+                expired.append(entry_id)
+                continue
+            if (now - created_at) > CODE_TTL_SECONDS:
+                expired.append(entry_id)
+        if expired:
+            for entry_id in expired:
+                del pending[entry_id]
+            self._save_json(path, pending)
+
+    def _all_platforms(self, suffix: str) -> list:
+        """List all platforms that have data files of a given suffix."""
+        platforms = []
+        for f in PAIRING_DIR.iterdir():
+            if f.name.endswith(f"-{suffix}.json"):
+                platform = f.name.replace(f"-{suffix}.json", "")
+                if not platform.startswith("_"):
+                    platforms.append(platform)
+        return platforms