Hi all, The PR [1] has now been extended taking much of the feedback into account and adding docs and tests. I have also added a validator for common passwords, based on a list of 1000 most common passwords. So I think the PR is ready for another round of review - I’m sure there is still room for improvement. Only current open task is to add release notes.
We now have three validators, all enabled by default in new projects: the common password validator, a validator that simply checks whether the password meets a minimum length, and one that compares the password to the user’s attributes, such as their name or e-mail address. The latter has limits in it’s comparison - a more thorough method is provided, for example, by zxcvbn [2]. However, I think vendoring a Python port of zxcvbn is a little too much - I do intend to create a third party package with a validator that ties to zxcvbn. There was a suggestion for a character class validator, e.g. requiring that the password contains digits or uppercase characters. I’m not very fond of that. Although quite common, I have strong doubts about whether it actually improves passwords: my impression is that requiring users to add a number will often mean they’ll add a 1 to the end, and requiring them to add an uppercase character will mean they uppercase the first character. If that is true, such a requirement would actually reduce password entropy, as one could assume that the last character of a password is almost always 1, etc. Unfortunately, I haven’t been able to find any research to support that (or the contrary), so I can’t back this up with anything solid. For clarity, by default we do not enable any validators in existing projects when they upgrade, as that would be breaking backwards compatibility. Erik [1] https://github.com/django/django/pull/4276 <https://github.com/django/django/pull/4276> [2] https://github.com/dropbox/zxcvbn <https://github.com/dropbox/zxcvbn> > On 14 Mar 2015, at 15:26, Erik Romijn <[email protected]> wrote: > > Hi all, > > Thanks for all the feedback. Good to see this seems to be heading in the > right direction. The suggestions make sense to me and I’ll work on those. > > There were two particular design suggestions: instead of tying the validator > to the password field, tying this to the authentication backend, which would > prevent having to add a setting, and allow different security requirements > for different backends. Another suggestion was to add configurable password > fields instead, which could also include other functionality. > > My concern with tying the validator to the auth backend instead, is that it > would mean there is absolutely no way to circumvent the validation, whereas > in the current scenario I’ve intentionally not included validation in > User.set_password() by default - but only in the user-facing elements. I > think it will be easier to get wider adoption of password validation, if we > still leave an opportunity open to avoid it in special cases. Also, I’m not > sure whether we could still easily and cleanly provide the appropriate help > text to the user. > > If someone would want validation that depends on the auth backend, this is > possible with undocumented APIs. If my memory serves me right, the user > object that the validator has access to will have an attribute that > identifies the backend used to authenticate the user. The validator could > make different choices based on that, or even call a method on a backend. > That’s not with a currently documented API though. > > Replaceable password fields are themselves interesting, but I think it would > be too limited for password validation in general. A specific wish was to > also be able to tie validation into a REST API, for example. The current > validator design allows trivial integration of a validator into absolutely > anything. Custom password fields are already not too hard - all you have to > do is create your own form, override the password fields and pass that form > to the appropriate views. It’s not even necessary to write your own views. We > could make that process simpler if the other benefits of custom password > fields are relevant enough, but I don’t think they’re the best design for the > validation problem. > > Erik > >> On 11 Mar 2015, at 09:52, Tino de Bruijn <[email protected] >> <mailto:[email protected]>> wrote: >> >> Hi Erik, I like the way this is going! >> >> I do want to emphasise the point that Josh made: you have to be able to >> aggregate all ValidationErrors, otherwise things can become quite >> frustrating. (Try to change your Skype password and you know why...) >> >> Tino >> >> On Wed, Mar 11, 2015 at 1:44 AM, Josh Smeaton <[email protected] >> <mailto:[email protected]>> wrote: >> Great stuff Erik. This will greatly simplify how we validate passwords! >> >> One thing I'd like to note is that it is extremely frustrating when a form >> fails validation with an error message, you fix that particular problem, and >> you're given the next error message. Ideally, all validators would run and >> spit out all of the error messages in one go. Then the user is given a >> chance to correct all problems at once rather than a submit and hope game. I >> took a look at the implementation and I don't think this is supported. Would >> it be possible to aggregate all of the ValidationErrors? >> >> Cheers >> >> >> On Monday, 9 March 2015 01:48:00 UTC+11, Erik Romijn wrote: >> Hello all, >> >> I've taken another stab at 16860[1]: having a password validation/policy in >> Django. I've made an initial simple PR[2] to show the approach I'd like to >> use - no tests or documentation yet, the example validators are not very >> nice, possibly bad naming, etc. But this should be sufficient to show how I >> would like to tackle this. There's quite a few decisions to take, >> influencing the later possibilities, which I'll try to outline below. >> >> Users choosing awful passwords is a serious security issue. Although >> password validation can only go so far - especially to the extent that we >> can implement in Django itself - to me it seems part of our responsibility >> in helping Django developers to build safer websites. >> >> First, let me briefly describe my approach: we add a new setting to define >> zero or more password validator classes. Optionally, a class can be provided >> with custom arguments to it's constructor. Each validator class has a >> help_text() method and a validate(password, user) method. The former >> produces a translatable sentence to be included in the form field's help >> text. The validate method validates a certain password, optionally taking >> the context of a user into account and passes its judgement on the password. >> If a validator considers a password insufficient, it raises a >> ValidationError. >> >> This is tied to the validation and form field setup in SetPasswordForm and >> AdminPasswordChangeForm. An obvious choice seems to be to tie this to >> User.set_password(). However, I intentionally did not include that step, as >> I feel this validation should primarily take place on the user frontend site >> with forms. This mirrors the way we typically handle this in Django. Should >> someone feel different, and want to tie this to set_password() as well, this >> is possible with a custom user object. Tying this validation into any other >> place is also trivial: just adding a single line. >> >> I decided not to go for standard Django validators, as I felt this would >> offer insufficient flexibility and configurability - as was already raised >> in previous discussions on this issue. >> >> In the ticket, Shai described a few particular goals for this feature: >> >> - Informing the user of the various password requirements: this is possible >> by each validator providing a description, which can be dependent on it's >> configuration, of it's requirements. Independent sentences from different >> validators are now concatenated, an approach which will not always yield the >> prettiest language. >> - Allowing policies to chain together smoothly: multiple validators can be >> run sequentially, stopping after the first failure. >> - Provide flexibility for complex requirements (some may include their own >> models): this is entirely possible within the design. >> - Backwards compatibility: the default setting is to have no validators, >> which means no change and no modifications in help text. I do suggest we >> include some reasonable defaults in the standard project template. >> - Javascript validation assistance or HTML5 support: not implemented >> currently, but this could be added in a similar way as help texts. >> - Prevent using email, username or other user attributes as (part of) >> passwords: where possible, the user object is passed to the validator. >> There's a (not pretty) example of this in the PR. >> - Prevent reuse of old passwords: it is possible in the design for a >> validator to store all passwords it saw. I have doubts on whether this would >> be a good approach though. >> >> So I think this design makes it simple to have sane defaults for new >> projects, extensive configurability while keeping simple scenarios simple to >> configure, and easy extensibility with third party password validators >> (zxcvbn comes to mind). I'd love to hear any feedback and ideas you may have. >> >> Erik >> >> >> [1] https://code.djangoproject.com/ticket/16860 >> <https://code.djangoproject.com/ticket/16860> >> [2] https://github.com/django/django/pull/4276 >> <https://github.com/django/django/pull/4276> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Django developers (Contributions to Django itself)" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected] >> <mailto:[email protected]>. >> To post to this group, send email to [email protected] >> <mailto:[email protected]>. >> Visit this group at http://groups.google.com/group/django-developers >> <http://groups.google.com/group/django-developers>. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/django-developers/3a0b87ad-5073-4af1-8a7a-cd91705e287a%40googlegroups.com >> >> <https://groups.google.com/d/msgid/django-developers/3a0b87ad-5073-4af1-8a7a-cd91705e287a%40googlegroups.com?utm_medium=email&utm_source=footer>. >> >> For more options, visit https://groups.google.com/d/optout >> <https://groups.google.com/d/optout>. >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Django developers (Contributions to Django itself)" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected] >> <mailto:[email protected]>. >> To post to this group, send email to [email protected] >> <mailto:[email protected]>. >> Visit this group at http://groups.google.com/group/django-developers >> <http://groups.google.com/group/django-developers>. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/django-developers/CANQFsQATUqV1CfsnAdjrvAQgHs0eQ-zx7pVC%2Bg9KvDiQ7mFbYQ%40mail.gmail.com >> >> <https://groups.google.com/d/msgid/django-developers/CANQFsQATUqV1CfsnAdjrvAQgHs0eQ-zx7pVC%2Bg9KvDiQ7mFbYQ%40mail.gmail.com?utm_medium=email&utm_source=footer>. >> For more options, visit https://groups.google.com/d/optout >> <https://groups.google.com/d/optout>. > > > -- > You received this message because you are subscribed to the Google Groups > "Django developers (Contributions to Django itself)" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at http://groups.google.com/group/django-developers > <http://groups.google.com/group/django-developers>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-developers/24FEB9D0-03ED-4CD6-81D4-E5A981C6BFE3%40solidlinks.nl > > <https://groups.google.com/d/msgid/django-developers/24FEB9D0-03ED-4CD6-81D4-E5A981C6BFE3%40solidlinks.nl?utm_medium=email&utm_source=footer>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. 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