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SVN Pilot Implementation for Secure Version Control System Transition

This document outlines the motivation, objectives, performance tests, security aspects, and implementation details of the SVN Pilot project aiming to replace CVS system with improved features and secure infrastructures. It highlights the benefits, features, and successful implementation of Subversion for version control management.

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SVN Pilot Implementation for Secure Version Control System Transition

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  1. SVN Pilot: CVS Replacement Manuel Guijarro Jonatan Hugo Hugosson Artur Wiecek David Horat Jonathan Brugge Michel Manent September 2008

  2. Outline • Introduction • Motivation • Subversion • Objectives • Performance Tests • Security • Implementation • Questions 2

  3. Version Control Systems • Maintain current and historical versions of files and data (source code) • There are many commercial and Open Source VC Systems: • (Centralised) CVS/SVN • (Distributed) GIT, Bazaar, Darcs, GNU arch, Mercurial, Monotone, etc • But subversion seems to be the most popular one (used by GCC, Phyton, PuTTY, Apache, GNOME, KDE, etc) • Physics User Community: (IN2P3, ROOT, Totem..) 3

  4. CERN Central CVS Service • Hosts over 330 Software Projects • 29 for Atlas • 46 for CMS • 8 for LHCb,….. • Over 3000 developers registered • Over 90 GBytes of source code • Creates 250 Remedy tickets per year • Over 100000 commits per month 4

  5. CERN Central CVS Service

  6. Central CVS service features • High Availability and Load Balancing • Web interface to repositories • Usage Statistics • Repository Remote Replication + Mirroring • Daily archive of Repositories and DR • Developers Mailing list • Pre/Post Commit Actions (such us e-mail notification, etc) • Various access method (ssh/kerberos) • Role split (CVS Admin/Librarian/Developer) 6

  7. Motivation for SVN Pilot • Originally designed to host less than 100 projects • Requests to provide a central SVN service: • From CMS • From ATLAS (case study in 2006) • And from many others • CVS is over 20 years old while SVN is this millennium technology • Requests for Read Access control

  8. SVN vs. CVS 8

  9. New Features (SVN 1.5) • Automatic update of working copy • Merge tracking • Subversion keeps track of what changes have been merged where • Sparse checkouts • Interactive conflict resolution 9

  10. Pilot Objectives • Provide current CVS service features • Add new features (available with SVN) • Control Read access per path (module) • Authenticated Web access • Binary files handling • Ease CVS to SVN migration • Improved usage statistics (SVN Stats) • Handling of first line support via the Help Desk • Delegate administrative tasks to Software Librarians of each project • Prevent uncontrolled setup of SVN servers • Manpower: 1.2 FTE project

  11. Timetable 11

  12. SVN Pilot study • Access methods • https • ssh • Shared storage • NFS 3/4 • AFS • Securing service • Restricted Shell • Chrooted hooks (commit scripts) • Infrastructure: • Librarian tools, Statistics, Web Interface,… 12

  13. Performance Tests • SVN check out of a 110 Mb project • Parameters • AFS/NFS3/NFS4 • HTTPS/SSH 13

  14. AFS vs NFS3 (1 server) 14

  15. AFS vs NFS4 (1 server) 15

  16. AFS vs NFS4 (3 servers) 16

  17. Preliminary Conclusions • AFS much faster than NFS • SSH much faster than https • SSH scales very well with high load • … • New tests ongoing (with mixture of read and write operations) 17

  18. Security • Project Isolation • Windows/Linux clients • Worldwide access • Shared file system independent • Hooks executed on servers • Librarians may put any script into the hooks • Librarians might need file system level access to repository – being studied Security risk!! 18

  19. Hooks (scripts) Client Server Svn commit Pre-commit hook is executed Post commit hook is executed SVN: Commit OK Email notification recieved 19

  20. Hook scripts chrooted: Server svnserer Librarian hooks: jailed hooks/post-commit hook Usr-hooks/post-commit hook Repository (1) Repositories System files 20

  21. Architecture • svn.cern.ch (rw) • Secured subversion server (only ssh) • Read and write access to repository • svnweb.cern.ch (ro) • User documentation • Project request • SVN web interface • Usage statistics 21

  22. Pilot Implementation Summary • SSH access for SVN clients • Restricted shell for all SVN clients • Hooks chrooted • SVN web (ro) • Web interfaces: websvn, trac • SSO Authenticated access • Administration delegated to librarian • Access rights • Hooks • Admin tools 22

  23. Conclusions • Secure service • This will replace CVS by end of 2009 • The service is supported (pre-production) • Pilot setup may differ from final setup • Access method, Web interface, shared file system, etc. • Changes will be transparent to the users 23

  24. Support http://cern.ch/svn • Try the pilot • Documentation Svn.support@cern.ch 24

  25. Questions? Thanks For Listening…. M. Guijarro, A. Wiecek, David Horat, Jonathan Bugge, M. Manent, H. Hugosson 25

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