Web-based file systems and WebDAV gateway services to CERN DFS file system

1. Web-based file systems and WebDAV gateway services to CERN DFS file system Alexandre Lossent, Alberto Pace

2. Agenda • Cross platform File sharing issues • (from 2 years ago) • What is WebDAV ? • WebDAV software overview • Servers • Clients • WebDAV at CERN

3. Agenda • Cross platform File sharing issues • (from 2 years ago) • What is WebDAV ? • WebDAV software overview • Servers • Clients • WebDAV at CERN

4. Introductory reminder:a slide from a presentation made 2 years ago (June 2001)

5. A web based solution ( ) Difficult to have both … An AFS/DFS-like solution ( ) What we would like for the future • Native access, including … • Shell access, Access Control, Source control , versioning, offline files • Global internet sharing • Consolidated Standard • Multiple vendors, strong support, interoperability, outsourceable … • Cross platform • Windows, Linux, Mac OS X • Free • At least the client software • Better if source code is available June 2001

6. A good news • A web based solution does no longer imply non-native • If the web based file system is implemented at the OS level, applications can access it natively ! Back to October 2003

7. The “Web” is part of the solution • Standard extensions to the HTTP protocol allow managing files on web servers as if these would be part of the local file system • HTTP Extensions for Distributed Authoring (WebDAV IETF RFC 2518) have been widely adopted on all major OS • Several commercial and public-domain implementations exists

8. Agenda • Cross platform File sharing issues • (from 2 years ago) • What is WebDAV ? • WebDAV software overview • Servers • Clients • WebDAV at CERN

9. WebDAV • Web Distributed Authoring and Versioning • IETF RFC 2518 (February 1999) • http://ietf.org/rfc/rfc2518.txt • An extension to the HTTP protocol • New verbs (PROPFIND, MKCOL, LOCK...), headers and status codes • Uses XML to format information • Initially designed as a way to author web sites • Redundant with FPSE in the Windows world • Versioning is limited to file locking (check in/out) • Can be used as a low-end network filesystem • WebDAV Home page • http://webdav.org • See it also for related open-source projects

10. WebDAV today • File access: • Create / delete files and folders • Read / write files • Copy / Move / Delete / rename files and folders • Document locking • prevent the overwrite problem, where two or more collaborators write to the same resource without first merging changes • Allow implementation of offline folders • Properties • XML properties provide storage for arbitrary metadata

11. On Windows Nautilus- Gnome On Linux

12. Windows Console SSH session On Linux

13. WebDAV tomorrow ? • Access control • Set / View / Modify Access Control lists using http • Versioning and Configuration Management • The V in WebDAV means “Versioning” • Document check-out, check-in • Retrieval of the history list • Offline files and folders • Other advanced features • Symbolic links • Ordered collections • Aggregated operations

14. For the “advanced features” … • The standard is being discussed since few years • Without real consensus on a common standard • Proprietary implementations already available • Example: Microsoft Sharepoint services

15. Agenda • Cross platform File sharing issues • (from 2 years ago) • What is WebDAV ? • WebDAV software overview • Servers • Clients • WebDAV at CERN

16. WebDAV servers • Supported by all common web servers • Apache module mod_dav • WebDAV package in PHP PEAR • Built-in support in IIS 5 and 6 • Need to activate appropriate HTTP verbs: PUT (write setting), PROPFIND (directory browsing setting) • Permissions are managed by NTFS ACLs • Microsoft adds a header to the WebDAV protocol for a HTTP GET to return a script’s output or its source (source access setting)

17. WebDAV clients • Clients exist on all major platforms • See again http://webdav.org • 3 flavors of clients with different usage: • Basic WebDAV clients or libraries • GUI or command-line to browse/download/upload files (but not edit them in-place); similar to FTP • E.g. IE5+, Nautilus, Perl / Java libraries... • WebDAV-enabled applications • Can access and edit files over WebDAV • E.g. Adobe, Macromedia, MS Office... • Operating system drivers • Allow to mount a WebDAV resource in a file system • Enables in-place edition for all applications • E.g. WinXP’s mini-redirector, Mac OS X built-in client, Linux davfs...

18. WebDAV clients: Windows (1) • Office Web Folders (msdaipp.dll) • Included in Office 2000/XP and Windows 2000 but NOT in XP/2003 (unless Office is installed) • Allows in-place edition of Office documents on web servers • Allows Internet Explorer to browse WebDAV and FPSE-enabled web sites (like FTP sites) • Supports HTTPS and all authentication methods • Implemented as an OLE DB data provider

19. WebDAV clients: Windows (2) • WinXP/2003 WebClient (WebDAV redirector) • You’ll find it in “Administrative Tools” – “Services” • A network file system driver • WebDAV folders transparently mounted as file system and made available to all applications using UNC paths ! • Folders are viewed in Windows Explorer like usual folders, with same functionality • Limited to HTTP on port 80 and basic or Kerberos authentication (!) • We are in discussion with MS to void the http limitation

20. WebDAV clients: Windows (3) MS Office Internet Explorer Other applications... Office Web Folders / MSDAIPPShips with MS Office and W2k WebClient / WebDAV redirectorShips with Windows XP/2003 FPSE server WebDAV server Windows XP/2003 only

21. WebDAV clients: Windows (4) WebDAV client used by Internet Explorer when a WebDAV location is opened

22. WebDAV clients: Macintosh • Built-in filesystem driver in OS X • Similar to XP’s WebDAV redirector • Supports only HTTP and basic authentication (!) • Works ok will all Mac Applications tested so far, including Office • Open-source Goliath project (Mac OS > 8.6) • Supports HTTPS • GUI interface to check in/out files • Files are edited in a local folder • Then use the GUI to check out modified version • Plus an wide number of commercial applications with built-in WebDAV support (as for Windows) • Example: Adobe, Macromedia, …

23. WebDAV clients: Linux • Command-line and GUI utilities (FTP-like) • E.g. Cadaver is available in standard CERN distributions • Filesystem driver • Davfs (again, limited to HTTP and basic authentication) (!) • But source code available and HTTPS prototype exists • Many open-source libraries • KDE, PerlDAV, Jakarta Slide Project... • Plus all commercial applications with built-in WebDAV support (as for Macintosh and Windows) • Generally, not well integrated yet • The Davfs filesystem being the exception • This might change with KDE/Gnome projects

24. WebDAV on Windows

25. WebDAV on Macintosh (1)

26. WebDAV on Macintosh (2)

27. WebDAV on Linux

28. Agenda • Cross platform File sharing issues • (from 2 years ago) • What is WebDAV ? • WebDAV software overview • Servers • Clients • WebDAV at CERN

29. The WebDAV–DFS gateway • Built using IIS 6 / Windows 2003 • Basically a WebDAV-enabled virtual folder that points to \\cern.ch\dfs • All script mappings are disabled • no need for the Microsoft-specific SourceAccess flag • Basic authentication • The only method widely supported • http[s]://dfs.cern.ch/dfs

30. The WebDAV–DFS gateway (2) • Current issues and limitations: • Files Locked in WebDAV are also locked in DFS • If the client does not explicitly unlock them,restart IIS to free the lock (!!) • Some clients abusively create additional files/folders • Mac OS X • Permissions cannot be managed – not an issue for CERN – see below • Internet access limited to https • A web interface has been added • https://dfs.cern.ch/dfsExplorer • Enables access to the DFS from any browser • Complete file management capabilities • including permission management • Aggregate operations

31. Future: web site editing • Replace insecure FTP by a WebDAV service for web site editing • May Run on different port so that the security of the main site is not compromised • Remember the “source access setting” ? • Configuration similar to the gateway • Authentication mandatory • No script mappings • Or … cross mount local Web storage into DFS

32. WebDAV access to Exchange • WebDAV is “the” protocol for exchange / mail workflow automation • Many native Exchange clients use http instead of MAPI • Ximian connector on Linux • Outlook 2003 uses http instead of MAPI • After the “Blaster Worm” MAPI on the internet is dead (port 135 closed everywhere) • At CERN, prototype project to integrate Official Leave requests automatically in the Exchange calendar using WebDAV

33. WebDAV access to Exchange

34. Summary • Use of WebDAV as interoperable network filesystem possible today • Can be applied to collaborative tools as well (Exchange) • Takes advantage of HTTP and XML ubiquity • Excellent level of interoperability for file access • Really reachable from any device / anywhere • Very simple to implement • But... • Still few implementation glitches • https support is still limited • Not a high-performance file system • Not a replacement for native file system (eg NTFS) • Permission management still require custom implementations