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Chris Coutinho 08d37a6597 docs: clean up astrolabe references after extraction

Remove astrolabe-specific docs and sections that belong in the
astrolabe repo. Update remaining references to point to the
astrolabe repo where appropriate.

- Fix .gitmodules SSH → HTTPS URL for astrolabe submodule
- Remove bump-version.yml stale "astrolabe" scope comment
- Delete blog-introducing-astrolabe.md (moved to astrolabe repo)
- Remove "Astrolabe Background Token Refresh" section from auth-flows.md
- Replace "Astrolabe User Setup" section in authentication.md with link
- Remove "Astrolabe Internal URL" section from configuration.md
- Remove "Webhook Presets (via Astrolabe UI)" from webhook guide

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

2026-02-12 23:16:50 +01:00

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Authentication Flows by Deployment Mode

This document provides a unified reference for authentication flows across all deployment modes. For configuration details, see Authentication. For OAuth protocol details, see OAuth Architecture.

Quick Reference Matrix

Mode	Client → MCP → NC	Background Sync	Astrolabe → MCP
Single-User BasicAuth	Embedded credentials	Same credentials	N/A
Multi-User BasicAuth	Header pass-through	App password (optional)	Bearer token
OAuth Single-Audience	Multi-audience token	Refresh token exchange	Bearer token
OAuth Token Exchange	RFC 8693 exchange	Refresh token exchange	Bearer token
Smithery Stateless	Session parameters	Not supported	N/A

Communication Patterns

This document covers three distinct communication patterns:

MCP Client → MCP Server → Nextcloud: Interactive tool calls initiated by users through MCP clients (Claude Desktop, etc.)
MCP Server → Nextcloud: Background operations like vector sync that run without user interaction
Astrolabe → MCP Server: Nextcloud app backend communication for settings UI and unified search

Deployment Modes

1. Single-User BasicAuth

Use Case: Personal Nextcloud instance, local development, single-user deployments.

MCP Client → MCP Server → Nextcloud

MCP Client                    MCP Server                   Nextcloud
    │                             │                            │
    │── MCP Request ─────────────▶│                            │
    │   (no auth required)        │                            │
    │                             │── HTTP + BasicAuth ───────▶│
    │                             │   Authorization: Basic     │
    │                             │   (embedded credentials)   │
    │                             │◀── API Response ───────────│
    │◀── Tool Result ─────────────│                            │

Key characteristics:

Credentials embedded in server configuration (NEXTCLOUD_USERNAME, NEXTCLOUD_PASSWORD)
Single shared NextcloudClient created at startup
No MCP-level authentication required (server trusts local clients)
All requests use the same Nextcloud user

Implementation: context.py:78-79 - Returns shared client from lifespan context

Background Sync

Uses the same embedded credentials as interactive requests. The background job accesses Nextcloud with the configured username/password.

Implementation: Background jobs use get_settings() to access credentials

Astrolabe Integration

Not applicable - Astrolabe is only used in multi-user deployments where users need personal settings and token management.

2. Multi-User BasicAuth

Use Case: Internal deployment where users provide their own credentials via HTTP headers.

MCP Client → MCP Server → Nextcloud

MCP Client                    MCP Server                   Nextcloud
    │                             │                            │
    │── MCP Request ─────────────▶│                            │
    │   Authorization: Basic      │                            │
    │   (user credentials)        │                            │
    │                             │── BasicAuthMiddleware ────▶│
    │                             │   Extracts credentials     │
    │                             │                            │
    │                             │── HTTP + BasicAuth ───────▶│
    │                             │   (pass-through)           │
    │                             │◀── API Response ───────────│
    │◀── Tool Result ─────────────│                            │

Key characteristics:

BasicAuthMiddleware extracts credentials from Authorization: Basic header
Credentials passed through to Nextcloud (not stored)
Client created per-request from extracted credentials
Stateless - no credential storage between requests

Implementation: context.py:187-248 - _get_client_from_basic_auth() extracts credentials from request state

Background Sync (Optional)

Requires ENABLE_OFFLINE_ACCESS=true. Users can store app passwords via Astrolabe for background operations.

Astrolabe                     MCP Server                   Nextcloud
    │                             │                            │
    │── Store App Password ──────▶│                            │
    │   (via management API)      │                            │
    │                             │── Store in SQLite ────────▶│
    │                             │   (encrypted)              │
    │◀── Confirmation ────────────│                            │
    │                             │                            │
    │         [Background Job]    │                            │
    │                             │── Retrieve app password ──▶│
    │                             │   (from encrypted storage) │
    │                             │── HTTP + BasicAuth ───────▶│
    │                             │   (stored app password)    │
    │                             │◀── API Response ───────────│

Requirements:

ENABLE_OFFLINE_ACCESS=true
TOKEN_ENCRYPTION_KEY for credential encryption
TOKEN_STORAGE_DB for SQLite storage path

Astrolabe → MCP Server

Astrolabe                     MCP Server                   Nextcloud OIDC
    │                             │                            │
    │── OAuth Flow ──────────────▶│◀── Token from IdP ────────▶│
    │   (user initiates)          │                            │
    │                             │                            │
    │── Bearer Token ────────────▶│                            │
    │   (management API calls)    │                            │
    │                             │── Validate via JWKS ──────▶│
    │                             │   (or introspection)       │
    │◀── API Response ────────────│                            │

Key characteristics:

Astrolabe has its own OAuth client (astrolabe_client_id in Nextcloud config)
Tokens are validated by MCP server using Nextcloud OIDC JWKS
Authorization check: token.sub == requested_resource_owner
Any valid Nextcloud OIDC token accepted (relaxed audience validation per ADR-018)

Implementation: unified_verifier.py:120-183 - verify_token_for_management_api() validates without strict audience check

3. OAuth Single-Audience (Default)

Use Case: Multi-user deployment with OAuth authentication. Tokens work for both MCP and Nextcloud.

This is the default mode when NEXTCLOUD_USERNAME/NEXTCLOUD_PASSWORD are not set.

MCP Client → MCP Server → Nextcloud

MCP Client                    MCP Server                   Nextcloud
    │                             │                            │
    │── Bearer Token ────────────▶│                            │
    │   aud: ["mcp-server",       │                            │
    │         "nextcloud"]        │                            │
    │                             │── Validate MCP audience ──▶│
    │                             │   (UnifiedTokenVerifier)   │
    │                             │                            │
    │                             │── HTTP + Same Token ──────▶│
    │                             │   Authorization: Bearer    │
    │                             │   (multi-audience token)   │
    │                             │                            │
    │                             │   NC validates its own aud │
    │                             │◀── API Response ───────────│
    │◀── Tool Result ─────────────│                            │

Key characteristics:

Token contains both audiences: aud: ["mcp-server", "nextcloud"]
MCP server validates only MCP audience (per RFC 7519)
Nextcloud independently validates its own audience
No token exchange needed - same token used throughout
Stateless operation for interactive requests

Token validation flow:

UnifiedTokenVerifier.verify_token() validates MCP audience
Token passed directly to Nextcloud via get_client_from_context()
Nextcloud validates its own audience when receiving API calls

Implementation:

unified_verifier.py:185-252 - _verify_mcp_audience() validates MCP audience only
context.py:96-99 - Uses token directly in multi-audience mode

Background Sync

Requires ENABLE_OFFLINE_ACCESS=true. Uses stored refresh tokens to obtain access tokens for background operations.

                              MCP Server                   Nextcloud OIDC
                                  │                            │
    [Background Job starts]       │                            │
                                  │── Get refresh token ──────▶│
                                  │   (from encrypted storage) │
                                  │                            │
                                  │── Token refresh request ──▶│
                                  │   grant_type=refresh_token │
                                  │   scope=openid profile ... │
                                  │◀── New access + refresh ───│
                                  │   (rotation)               │
                                  │                            │
                                  │── Store rotated refresh ──▶│
                                  │   (encrypted)              │
                                  │                            │
                                  │── HTTP + Access Token ────▶│
                                  │   Authorization: Bearer    │
                                  │◀── API Response ───────────│

Key characteristics:

Refresh tokens stored encrypted in SQLite (TOKEN_STORAGE_DB)
Nextcloud OIDC rotates refresh tokens on every use (one-time use)
TokenBrokerService handles token lifecycle
Per-user locking prevents race conditions during concurrent refresh

Implementation:

token_broker.py:269-362 - get_background_token() handles refresh with locking
token_broker.py:428-509 - _refresh_access_token_with_scopes() exchanges refresh token

Astrolabe → MCP Server

Same as Multi-User BasicAuth. See Astrolabe → MCP Server above.

4. OAuth Token Exchange (RFC 8693)

Use Case: Multi-user deployment where MCP tokens are separate from Nextcloud tokens. Provides stronger security boundaries.

Enabled by ENABLE_TOKEN_EXCHANGE=true.

MCP Client → MCP Server → Nextcloud

MCP Client                    MCP Server                   Nextcloud OIDC
    │                             │                            │
    │── Bearer Token ────────────▶│                            │
    │   aud: "mcp-server"         │                            │
    │   (MCP audience only)       │                            │
    │                             │── Validate MCP audience ──▶│
    │                             │                            │
    │                             │── RFC 8693 Exchange ──────▶│
    │                             │   grant_type=              │
    │                             │     urn:ietf:params:oauth: │
    │                             │     grant-type:token-exchange
    │                             │   subject_token=<mcp-token>│
    │                             │   requested_audience=      │
    │                             │     "nextcloud"            │
    │                             │◀── Delegated Token ────────│
    │                             │   aud: "nextcloud"         │
    │                             │                            │
    │                             │── HTTP + Delegated Token ─▶│
    │                             │   Authorization: Bearer    │
    │                             │◀── API Response ───────────│
    │◀── Tool Result ─────────────│                            │

Key characteristics:

Strict audience separation: MCP token has aud: "mcp-server" only
Server exchanges for Nextcloud-audience token on each request
Ephemeral delegated tokens (not cached by default)
Strongest security boundary between MCP and Nextcloud access

Token exchange details:

Uses RFC 8693 "urn:ietf:params:oauth:grant-type:token-exchange"
Subject token: MCP access token
Requested audience: Nextcloud resource URI
Result: Short-lived token scoped for Nextcloud

Implementation:

token_broker.py:220-267 - get_session_token() performs on-demand exchange
token_exchange.py - exchange_token_for_delegation() implements RFC 8693
context.py:88-94 - Routes to session client in exchange mode

Background Sync

Same as OAuth Single-Audience. Uses stored refresh tokens from Flow 2 provisioning.

                              MCP Server                   Nextcloud OIDC
                                  │                            │
    [User provisions access]      │                            │
                                  │── Flow 2 OAuth ───────────▶│
                                  │   client_id="mcp-server"   │
                                  │   scope=offline_access ... │
                                  │◀── Refresh Token ──────────│
                                  │   (stored encrypted)       │
                                  │                            │
    [Background Job runs later]   │                            │
                                  │── Refresh for background ─▶│
                                  │   (same as single-audience)│

Key difference from interactive:

Interactive: On-demand token exchange per request
Background: Uses pre-provisioned refresh tokens (Flow 2)

Astrolabe → MCP Server

Same as Multi-User BasicAuth. See Astrolabe → MCP Server above.

5. Smithery Stateless

Use Case: Multi-tenant SaaS deployment via Smithery platform. Fully stateless.

Enabled by SMITHERY_DEPLOYMENT=true.

MCP Client → MCP Server → Nextcloud

MCP Client                    MCP Server                   Nextcloud
    │                             │                            │
    │── SSE Connect ─────────────▶│                            │
    │   ?nextcloud_url=...        │                            │
    │   &username=...             │                            │
    │   &app_password=...         │                            │
    │                             │── SmitheryConfigMiddleware │
    │                             │   Extract URL params       │
    │                             │                            │
    │── MCP Request ─────────────▶│                            │
    │   (no Authorization header) │                            │
    │                             │── Create per-request ─────▶│
    │                             │   NextcloudClient          │
    │                             │                            │
    │                             │── HTTP + BasicAuth ───────▶│
    │                             │   (from session params)    │
    │                             │◀── API Response ───────────│
    │◀── Tool Result ─────────────│                            │

Key characteristics:

Configuration passed via URL query parameters (Smithery configSchema)
No persistent state - client created fresh per request
No OAuth infrastructure
No background sync support (stateless)
No admin UI available

Required session parameters:

nextcloud_url: Nextcloud instance URL
username: Nextcloud username
app_password: Nextcloud app password

Implementation: context.py:108-184 - _get_client_from_session_config() creates client from session params

Background Sync

Not supported. Smithery mode is fully stateless with no credential storage.

Astrolabe Integration

Not applicable. Smithery deployments don't integrate with Astrolabe.

Configuration Quick Reference

Single-User BasicAuth

NEXTCLOUD_HOST=http://localhost:8080
NEXTCLOUD_USERNAME=admin
NEXTCLOUD_PASSWORD=password

Multi-User BasicAuth

NEXTCLOUD_HOST=http://nextcloud.example.com
ENABLE_MULTI_USER_BASIC_AUTH=true

# Optional: For background sync
ENABLE_OFFLINE_ACCESS=true
TOKEN_ENCRYPTION_KEY=<32-byte-key>
TOKEN_STORAGE_DB=/data/tokens.db

OAuth Single-Audience (Default)

NEXTCLOUD_HOST=http://nextcloud.example.com
# No username/password triggers OAuth mode

# Optional: Static client credentials (instead of DCR)
NEXTCLOUD_OIDC_CLIENT_ID=<client-id>
NEXTCLOUD_OIDC_CLIENT_SECRET=<client-secret>

# Optional: For background sync
ENABLE_OFFLINE_ACCESS=true
TOKEN_ENCRYPTION_KEY=<32-byte-key>
TOKEN_STORAGE_DB=/data/tokens.db

OAuth Token Exchange

NEXTCLOUD_HOST=http://nextcloud.example.com
ENABLE_TOKEN_EXCHANGE=true
NEXTCLOUD_OIDC_CLIENT_ID=<client-id>
NEXTCLOUD_OIDC_CLIENT_SECRET=<client-secret>

# Optional: For background sync
ENABLE_OFFLINE_ACCESS=true
TOKEN_ENCRYPTION_KEY=<32-byte-key>
TOKEN_STORAGE_DB=/data/tokens.db

Smithery Stateless

SMITHERY_DEPLOYMENT=true
# All other config comes from session URL parameters

Authentication - Configuration details and setup guides
OAuth Architecture - Deep OAuth protocol details
ADR-004: Progressive Consent - Dual OAuth flow architecture
ADR-005: Token Audience Validation - Audience validation strategy
ADR-018: Nextcloud PHP App - Astrolabe integration
ADR-020: Deployment Modes - Mode detection and validation

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Authentication Flows by Deployment Mode

Quick Reference Matrix

Communication Patterns

Deployment Modes

1. Single-User BasicAuth

MCP Client → MCP Server → Nextcloud

Background Sync

Astrolabe Integration

2. Multi-User BasicAuth

MCP Client → MCP Server → Nextcloud

Background Sync (Optional)

Astrolabe → MCP Server

3. OAuth Single-Audience (Default)

MCP Client → MCP Server → Nextcloud

Background Sync

Astrolabe → MCP Server

4. OAuth Token Exchange (RFC 8693)

MCP Client → MCP Server → Nextcloud

Background Sync

Astrolabe → MCP Server

5. Smithery Stateless

MCP Client → MCP Server → Nextcloud

Background Sync

Astrolabe Integration

Configuration Quick Reference

Single-User BasicAuth

Multi-User BasicAuth

OAuth Single-Audience (Default)

OAuth Token Exchange

Smithery Stateless

Related Documentation

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