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Archive for August, 2014

How to Patch Drupal Sites

My experience patching Drupal sites is years old and my general ‘policy’ (habit) is to not upgrade unless or until there is a severe security issue. It’s the same with WordPress, which I’ve been patching in several sites for over a decade. Issues like role escalation are not serious if you trust fellow users (authors) or if you are the sole user. In the case of some agencies that use Drupal, it might be safe to say that the risk introduced by change to code outweighs the safety because as far as one can tell, visitors of such sites do not even register for a username. All users are generally quite trusted and they work closely (one must have checked the complete list to be absolutely sure). There is also ‘paper trail’ of who does what, so if one was to exploit a bug internally, e.g. to do something s/he is not authorised to do, it would be recorded, which in itself acts as a deterrent.

If the security issue is trivial to fix with a trivial patch, then I typically apply it manually. When the SQL injection bug surfaced some months back that’s what many people did for the most part. For larger releases (not bug fixes) the same applies, until there is no other alternative. What one needs to worry more about are module updates, especially those that are security updates. One should make a list of all modules used and keep track of news or new releases (watching general FOSS news is usually not enough until it’s too late). Thankfully, detailed information on what the flaws are becomes available, along with associated risks both for core and additional/peripheral modules.

Then there’s testing, which I guess one needs to do for any changes that are made, assuming time permits this. The last major Drupal flaw had a 7-hour window between publication and exploitation in vast numbers (maybe millions). It means one cannot always follow the formal procedure of testing, albeit testing in an ad hoc way or minimising the risk by applying a patch ought to work well. This leads me to suggesting that developers don’t need to have one uniform workflow/process for changing Drupal but a multi-faceted one. Proposal:

If the flaw is

1. severe
2. not back-end (i.e. not related to role management)

consider the complexity of the patch and test immediately on an existing copy of the site, then deploy on ‘live’.

If the patch is a core patch, no alternatives exist. If the patch is to be applied to a module, study the effect of disabling the module (assuming no dependents), consider temporarily keeping it out of reach (public site/s).

For less severe flaws:

1) merge into git on a dedicated branch
2) test on a local vagrant installation
3) schedule for deployment to “development” for testing
4) schedule for deployment to “staging”
5) run regressions (one needs to define these)
6) Client to do any required acceptance testing
7) schedule for deployment to production.

Suffice to say, the changes should not only be made through git (not directly) but a database dump too (or snapshot) should be taken, both for quick fixes and for longer testing purposes because even if changes are revoked (git rollback) the database can be left in a sub-par/inadequate state.

Regressions of interest for Drupal are not just site-specific. There are some nice templates for these and one needs to consider which modules to use in the site. Intuition and general familiarity with the CMS loop/hooks help one predict what impact a change would have on modules, if any. Drupal has good documentation of functions (by names), so these too can be studied before changes are made. To avoid some modules ‘silently’ breaking, following any change to core (or even modules) one may need to go through a list of tests. specified in advance, that help verify no module spits out PHP errors or behaves oddly. It is common to test critical pages first, e.g. finding an authority, research reports, etc. Sometimes it should be possible to also automate the testing by basically making local snapshot of pages of interest and then diff‘ing them after changes are made, using sophisticated tools like Versionista or a manual side-by-side comparison by a human operator. There are browser extensions that further facilitate this, but caching such as Cloudflare, varnish cache etc. can impede this process (even though changes to underlying code may invoke an override, at least for varnish).

Regressions are nice, but in many cases developers don’t have time to run them and a simpler set of manual checks can help gain confidence that changes made have no detrimental effects.

I cannot recall ever having major issues patching (as opposed to upgrading) the core or WordPress and Drupal and I have done this hundreds of times. The quality of testing when it comes to core (not external/additional) is quite high, but another worthy step is, before making any changes, look around forums to see what experience other people have had. There were cases where patches were problematic and this quickly became public knowledge; sometimes workarounds or patches for the patches are circulated within hours.

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