New password hashing scheme as plugin

[aki.tuomi at dovecot.fi]

> On July 27, 2016 at 2:08 AM Andreas Meyer <luckyfellow42 at gmail.com> wrote:
> 
> 
> Hi,
> 
> 
> I want to add a new password hashing scheme as plugin and provide it for
> the dovecot project, so that it will be included as optional plugin in
> future releases.
> 
> Yet the plugin compiles fine and the .so file gets created.
> 
> My approach is to call the functions password_scheme_register() and
> password_scheme_unregister() (src/auth/password-scheme.c) inside the
> plugin's _init() and _deinit() functions.
> 
> When a client tries to login via imap the log shows an error message:
> 
> Error: Couldn't load required plugin
> /usr/local/lib/dovecot/lib20_newauth_plugin.so: dlopen() failed:
> /usr/local/lib/dovecot/lib20_newauth_plugin.so: undefined symbol:
> password_scheme_unregister
> 
> That error obviously occurs, because the required lib is not linked into
> the plugin.
> 
> 
> Now my problem is to understand, whether this approach (via .so file) can
> be successful at all and if so, how?
> Do I need to link libs into it? Which would that be and how do I specify
> them in the Makefile.am?
> 
> I assume, I don't need to link a lib, but need to use a hook to register
> the new hashing scheme, since the plugin is loaded into an already existing
> process, which needs to get extended. If this is true, which hook would
> that be and how do I register the new scheme?
> 
> Or is there no way to accomplish this via a separated .so plugin? Should I
> extend the sources in /src/auth instead? (separat file for the hashing
> scheme with preprocessor instructions to include it only on demand)
> 
> 
> 
> Thank you very much,
> 
> Andreas

Can you publish your code in, say, github.com and provide link to it?  New password scheme is doable as plugin but it needs to placed in different place and it will be autoloaded.

Aki