Post on 26-Dec-2015
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Web-based file systems and WebDAV Web-based file systems and WebDAV gateway services to CERN DFS file systemgateway services to CERN DFS file system
Alexandre Lossent, Alberto Pace
AgendaAgenda
Cross platform File sharing issues (from 2 years ago)
What is WebDAV ? WebDAV software overview
Servers Clients
WebDAV at CERN
AgendaAgenda
Cross platform File sharing issues (from 2 years ago)
What is WebDAV ? WebDAV software overview
Servers Clients
WebDAV at CERN
Introductory reminder:Introductory reminder:a slide from a presentation a slide from a presentation
made 2 years ago (June 2001)made 2 years ago (June 2001)
What we would like for the futureWhat 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
An AFS/DFS-likesolution
( )
A web based solution( )
Difficult to have both …
June 2001June 2001
A good newsA 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 2003Back to October 2003
The “Web” is part of the solutionThe “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
AgendaAgenda
Cross platform File sharing issues (from 2 years ago)
What is WebDAV ? WebDAV software overview
Servers Clients
WebDAV at CERN
WebDAVWebDAV
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
WebDAVWebDAV today 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
On Windows
Nautilus-GnomeOn Linux
WindowsConsole
SSH sessionOn Linux
WebDAV tomorrow ?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
For the “advanced For the “advanced features” …features” …
The standard is being discussed since few years Without real consensus on a common standard
Proprietary implementations already available Example: Microsoft Sharepoint services
AgendaAgenda
Cross platform File sharing issues (from 2 years ago)
What is WebDAV ? WebDAV software overview
Servers Clients
WebDAV at CERN
WebDAV serversWebDAV 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)
WebDAV clientsWebDAV 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...
WebDAV clients: Windows (1)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
WebDAV clients: Windows (2)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
WebDAV clients: Windows (3)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
WebDAV clients: Windows (4)WebDAV clients: Windows (4)
Windows 2000
Windows XP/2003
Windows XP/2003 with Office
HTTP WebFolders Redirector Redirector
HTTPS or custom port
WebFolders N/A WebFolders
WebDAV client used by Internet Explorer when a WebDAV location is opened
WebDAV clients: MacintoshWebDAV 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, …
WebDAV clients: LinuxWebDAV 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
WebDAV on WindowsWebDAV on Windows
WebDAV on Macintosh (1)WebDAV on Macintosh (1)
WebDAV on Macintosh (2)WebDAV on Macintosh (2)
WebDAV on LinuxWebDAV on Linux
AgendaAgenda
Cross platform File sharing issues (from 2 years ago)
What is WebDAV ? WebDAV software overview
Servers Clients
WebDAV at CERN
The WebDAV–DFS gatewayThe 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
The WebDAV–DFS gateway (2)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
Future: web site editingFuture: 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
WebDAV access to ExchangeWebDAV 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
WebDAV access to ExchangeWebDAV access to Exchange
SummarySummary
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