feat: Implement ADR-004 Progressive Consent foundation (partial)
Implements Progressive Consent architecture with dual OAuth flows: - Flow 1: Direct client authentication (aud: "mcp-server") - Flow 2: Resource provisioning with refresh tokens Components added: - Client registry with validation (client_registry.py) - Progressive token verifier (progressive_token_verifier.py) - Token broker service integration - Provisioning decorator for MCP tools - OAuth provisioning tools (provision_nextcloud_access, etc.) Configuration: - Progressive Consent enabled by default (ENABLE_PROGRESSIVE_CONSENT=true) - Client validation with pre-registered clients - Audience separation framework KNOWN ISSUE - Token Exchange Pattern Incorrect: The current implementation does NOT properly implement token exchange. MCP session tokens should be EXCHANGED for delegated Nextcloud tokens during tool calls, not stored/reused. Critical corrections needed: 1. Session tokens: Flow 1 token → exchange → ephemeral Nextcloud token - Generated on-demand per tool call - Short-lived, not stored - Scopes limited to tool requirements 2. Background tokens: Flow 2 refresh token → background Nextcloud token - Only for offline/background jobs - Potentially different scopes than session tokens - Must NOT be used for MCP session tool calls The token exchange mechanism needs to be implemented to properly separate session-time delegation from background job authorization. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
This commit is contained in:
Chris Coutinho
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"""
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Token Verifier for ADR-004 Progressive Consent Architecture.
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This module implements token verification with strict audience separation:
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- Flow 1 tokens have aud: "mcp-server" for MCP authentication
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- Flow 2 tokens have aud: "nextcloud" for resource access
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- Token Broker manages the exchange between audiences
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"""
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import logging
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import os
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from datetime import datetime, timezone
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from typing import Optional
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import jwt
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from mcp.server.auth.provider import AccessToken
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from nextcloud_mcp_server.auth.refresh_token_storage import RefreshTokenStorage
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from nextcloud_mcp_server.auth.token_broker import TokenBrokerService
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logger = logging.getLogger(__name__)
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class ProgressiveConsentTokenVerifier:
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"""
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Token verifier for Progressive Consent dual OAuth flows.
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This verifier:
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1. Validates Flow 1 tokens (aud: "mcp-server") for MCP authentication
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2. Checks if user has provisioned Nextcloud access (Flow 2)
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3. Uses Token Broker to obtain aud: "nextcloud" tokens when needed
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"""
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def __init__(
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self,
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token_storage: RefreshTokenStorage,
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token_broker: Optional[TokenBrokerService] = None,
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oidc_discovery_url: Optional[str] = None,
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nextcloud_host: Optional[str] = None,
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encryption_key: Optional[str] = None,
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):
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"""
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Initialize the Progressive Consent token verifier.
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Args:
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token_storage: Storage for refresh tokens
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token_broker: Token broker service (created if not provided)
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oidc_discovery_url: OIDC provider discovery URL
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nextcloud_host: Nextcloud server URL
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encryption_key: Fernet key for token encryption
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"""
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self.storage = token_storage
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self.oidc_discovery_url = oidc_discovery_url or os.getenv(
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"OIDC_DISCOVERY_URL",
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f"{os.getenv('NEXTCLOUD_HOST')}/.well-known/openid-configuration",
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)
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self.nextcloud_host = nextcloud_host or os.getenv("NEXTCLOUD_HOST")
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self.encryption_key = encryption_key or os.getenv("TOKEN_ENCRYPTION_KEY")
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# Create token broker if not provided
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if token_broker:
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self.token_broker = token_broker
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elif self.encryption_key:
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self.token_broker = TokenBrokerService(
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storage=token_storage,
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oidc_discovery_url=self.oidc_discovery_url,
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nextcloud_host=self.nextcloud_host,
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encryption_key=self.encryption_key,
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)
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else:
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self.token_broker = None
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logger.warning("Token broker not available - encryption key missing")
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async def verify_token(self, token: str) -> Optional[AccessToken]:
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"""
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Verify a Flow 1 token (aud: "mcp-server").
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This validates that:
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1. Token has correct audience for MCP server
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2. Token is not expired
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3. Token has valid signature (if verification enabled)
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Args:
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token: JWT access token from Flow 1
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Returns:
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AccessToken if valid, None otherwise
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"""
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try:
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# Decode without signature verification (IdP handles that)
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# In production, would verify signature with IdP public key
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payload = jwt.decode(token, options={"verify_signature": False})
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# CRITICAL: Verify audience is for MCP server (Flow 1)
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audiences = payload.get("aud", [])
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if isinstance(audiences, str):
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audiences = [audiences]
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# Check for correct audience
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if "mcp-server" not in audiences:
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logger.warning(f"Token rejected: wrong audience {audiences}")
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# Check if this is a Nextcloud token (wrong flow)
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if "nextcloud" in audiences:
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logger.error(
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"Received Nextcloud token in MCP context - "
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"client may be using wrong token"
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)
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return None
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# Check expiry
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exp = payload.get("exp", 0)
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if exp < datetime.now(timezone.utc).timestamp():
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logger.debug("Token expired")
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return None
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# Extract user info
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user_id = payload.get("sub", "unknown")
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client_id = payload.get("client_id", "unknown")
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scopes = payload.get("scope", "").split()
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exp = payload.get("exp", None)
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# Create AccessToken for MCP framework
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return AccessToken(
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token=token,
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client_id=client_id,
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scopes=scopes,
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expires_at=exp,
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resource=f"user:{user_id}", # Store user_id in resource field
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)
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except jwt.InvalidTokenError as e:
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logger.debug(f"Invalid token: {e}")
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return None
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except Exception as e:
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logger.error(f"Token verification failed: {e}")
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return None
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async def check_provisioning(self, user_id: str) -> bool:
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"""
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Check if user has provisioned Nextcloud access (Flow 2).
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Args:
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user_id: User identifier from Flow 1 token
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Returns:
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True if user has completed Flow 2, False otherwise
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"""
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if not self.storage:
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return False
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refresh_data = await self.storage.get_refresh_token(user_id)
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return refresh_data is not None
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async def get_nextcloud_token(self, user_id: str) -> Optional[str]:
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"""
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Get a Nextcloud access token (aud: "nextcloud") for the user.
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This uses the Token Broker to:
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1. Check for cached Nextcloud token
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2. If expired, refresh using stored master refresh token
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3. Return token with aud: "nextcloud" for API access
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Args:
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user_id: User identifier from Flow 1 token
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Returns:
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Nextcloud access token if provisioned, None otherwise
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"""
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if not self.token_broker:
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logger.error("Token broker not available")
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return None
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# Check if user has provisioned access
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if not await self.check_provisioning(user_id):
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logger.info(f"User {user_id} has not provisioned Nextcloud access")
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return None
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# Get or refresh Nextcloud token
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try:
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nextcloud_token = await self.token_broker.get_nextcloud_token(user_id)
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if nextcloud_token:
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logger.debug(f"Obtained Nextcloud token for user {user_id}")
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return nextcloud_token
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except Exception as e:
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logger.error(f"Failed to get Nextcloud token: {e}")
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return None
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async def validate_scopes(
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self, token: AccessToken, required_scopes: list[str]
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) -> bool:
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"""
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Validate that token has required scopes.
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Args:
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token: The access token
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required_scopes: List of required scopes
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Returns:
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True if all required scopes present, False otherwise
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"""
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token_scopes = set(token.scopes) if token.scopes else set()
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required = set(required_scopes)
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missing = required - token_scopes
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if missing:
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logger.debug(f"Token missing required scopes: {missing}")
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return False
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return True
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async def close(self):
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"""Clean up resources."""
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if self.token_broker:
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await self.token_broker.close()
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