LibreOffice Solid UCP

C++ implementation of a Universal Content Provider (UCP) for LibreOffice that enables native Solid pod integration with vnd-solid:// URL scheme and DPoP authentication.

What This Is

This repo contains the source code for a LibreOffice UCP that provides native Solid protocol support. When integrated into LibreOffice, users can access Solid pods through the standard "File → Open Remote Files" interface using custom vnd-solid:// URLs that internally map to HTTPS.

Current Status

✅ URL Scheme: Custom vnd-solid:// routing implemented and working
✅ Integration: Successfully integrated into LibreOffice build system
✅ Authentication: Complete OAuth 2.0 + PKCE + DPoP implementation
✅ Build System: All namespace issues resolved, compiles cleanly
🔄 Testing: Ready for runtime testing with Solid pods

Installation

Prerequisites

• LibreOffice 25.2+ source code
• Standard LibreOffice build dependencies (autotools, C++ compiler, etc.)
• libcurl development headers
• OpenSSL development headers

Integration Steps

1. Clone LibreOffice source (if not already done):

   git clone https://git.libreoffice.org/core libreoffice-core
   cd libreoffice-core

2. Clone this repository:

   git clone https://github.com/inrupt/libreoffice-solid.git

3. Copy Solid UCP files to LibreOffice source:

   # Copy UCP implementation
   cp -r libreoffice-solid/ucb/source/ucp/solid/ ucb/source/ucp/
   
   # Copy build configuration
   cp libreoffice-solid/ucb/Library_ucpsolid.mk ucb/
   
   # Copy UCB provider registration
   cp libreoffice-solid/officecfg/registry/data/org/openoffice/ucb/Configuration.xcu \
      officecfg/registry/data/org/openoffice/ucb/
   
   # Copy Remote Files dialog integration
   cp libreoffice-solid/fpicker/source/office/RemoteFilesDialog.cxx \
      fpicker/source/office/
   
   # Copy server details controls
   cp libreoffice-solid/svtools/source/dialogs/ServerDetailsControls.* \
      svtools/source/dialogs/

4. Update LibreOffice build system:

   # Add ucpsolid to UCB module build
   echo "ucpsolid \\" >> ucb/Module_ucb.mk
   
   # Add to repository makefile
   echo "ucb/Library_ucpsolid.mk \\" >> Repository.mk

5. Configure and build LibreOffice:

   ./autogen.sh --enable-debug
   make clean
   make -j$(nproc)

How It Works

1. Custom URL Scheme: Uses vnd-solid:// URLs that get converted to https:// internally
2. UCB Registration: Registers as Provider98 in UCB Configuration.xcu
3. Authentication: Full OAuth 2.0 + PKCE + DPoP authentication flow
4. File Operations: Standard LibreOffice content operations through Solid HTTP API
5. UI Integration: Appears as "Solid Pod" in Remote Files dialog

Key Components

• SolidOAuth.cxx/hxx: OAuth 2.0 + PKCE + DPoP authentication with ECDSA P-256 JWT signing
• solidprovider.cxx/hxx: Main UCP implementation with vnd-solid:// URL scheme handling
• solidcontent.cxx/hxx: Content interface for file operations
• SolidHttpSession.cxx/hxx: HTTP session management with DPoP authentication headers
• SolidConfigDialog.cxx/hxx: Configuration dialog for Solid pod settings
• SolidCallbackServer.cxx/hxx: Local OAuth callback server for browser authentication

Usage

Once installed and LibreOffice is built:

1. Open Remote Files: File → Open Remote Files
2. Select Service: Choose "Solid Pod" from service dropdown
3. Enter Pod URL: Use format vnd-solid://storage.inrupt.com/your-pod-id/
4. Authenticate: Browser will open for OAuth login
5. Access Files: Browse and open files from your Solid pod

Technical Architecture

URL Scheme Resolution

• Input: vnd-solid://storage.inrupt.com/pod/file.odt
• Internal: Converts to https://storage.inrupt.com/pod/file.odt
• UCB Routing: Registered as Provider98 to intercept vnd-solid URLs
• WebDAV Bypass: Prevents WebDAV UCP from claiming HTTPS URLs

Authentication Flow

1. Discovery: OIDC configuration from pod domain
2. Authorization: Browser-based OAuth 2.0 + PKCE flow
3. Token Exchange: Authorization code for access/refresh tokens
4. DPoP Headers: ECDSA P-256 signed JWT tokens per request
5. Request Signing: Each HTTP request gets unique DPoP token

Build Integration

• gbuild System: Uses LibreOffice's standard build macros
• Service Registration: UCB Configuration.xcu registers the provider
• Library Dependencies: Links to curl, openssl, LibreOffice core libraries
• UI Integration: Remote Files dialog shows "Solid Pod" option

Dependencies

• libcurl: HTTP client operations and authentication flows
• openssl: ECDSA P-256 key generation and JWT signing for DPoP
• LibreOffice core: ucbhelper, comphelper, sal, svtools, fpicker libraries

Current Limitations

• Pod Discovery: Limited to manual URL entry (no automatic pod discovery)
• Container Operations: Basic file operations only (no advanced container management)
• ACL Integration: No Access Control List management
• Offline Support: No local caching or offline file access

Development Areas

Priority areas for contribution:

• Runtime Testing: Verify end-to-end authentication and file operations
• Error Handling: Improve network error recovery and user feedback
• Performance: Optimize HTTP request batching and connection reuse
• Pod Compatibility: Test with different Solid pod implementations
• Security Review: Audit DPoP implementation and credential storage

Troubleshooting

Build Issues

• Missing Dependencies: Ensure libcurl and openssl development headers are installed
• Namespace Errors: Code uses libreoffice::solid namespace structure
• Missing Files: Verify all files were copied to correct LibreOffice source locations

Runtime Issues

• No Solid Pod Option: Check UCB Configuration.xcu was updated and LibreOffice restarted
• Authentication Failures: Verify pod URL format and network connectivity
• File Access Errors: Check DPoP token generation and HTTP request headers

Contributing

This project welcomes contributions. Areas of focus:

1. Testing: Verify compatibility across different Solid pod providers
2. Features: Implement advanced Solid protocol features (ACL, containers, etc.)
3. Performance: Optimize authentication flows and HTTP operations
4. Documentation: Improve code documentation and user guides

License

MPL-2.0 (Mozilla Public License 2.0, same as LibreOffice core)