[Fedora-directory-devel] Please Review: Add LDAPI (LDAP over unix domain sockets)

[Pete Rowley]

This is a feature that exists in OpenLDAP (but has no RFC that I am aware of).
Heimdal uses this feature exclusively for its directory interactions (making it
incompatible with other LDAP directories), and Samba testing is often performed
over unix domain sockets (a convenience for them). There are advantages: no TCP
overhead for local connections, the ability to test for the OS level user
credentials, and AFAIK, an unsniffable transport without additional
requirements. On that last point, I welcome arguments to the contrary.

The socket file is created as var/run/fedora-ds/slapd-<instance>.socket by
default, but this can be modified in configuration. I'm actually not sure where
the best place to put this is since access control along the path to the socket
matters. The socket itself is chmodded to give rw to owner, groups, and other by
the server upon creation.

I've added LDAPI auto authentication / bind, which basically means that if you
access the DS over LDAPI it will trust the OS level auth and automatically bind
you at connection open (i.e. the server won't wait for an explicit bind).  There
are several options to this:

1. You can turn auto binding on or off
2. You can specify a dn that root should be bound as (e.g. directory manager, or
perhaps an admin account)
3. You can specify that the user maps to an existing entry via admin specified
attributes - which are probably going to be uidNumber and gidNumber (the
default) - root can be bound this way too, and this method takes precedence over 2.
4. In the event that the other methods are turned off, or do not result in bind
credentials, you can specify that a DN be constructed for the bind DN and supply
a suffix for the DN - this allows non-mapped entries to look sensible, you may
use this feature to specifiy a suffix that works with existing access control
for example.

When auto binding is on, and option 4. is set, or option 2. is set and the unix
user credentials match a single entry in the DIT, users are automatically bound
at connection open and anonymous binds are impossible since an anonymous bind
attempt is modified to the credentials used at connection open. Non-anonymous
binds work as usual. This means that scripts and so on can be "dumb" and
credentials need not be left lying around for snoopers, users on the local
machine not be concerned with credentials either, and yet all connections can be
subject to targetted access control.

All configuration is dynamically observed except for the socket file location
and the LDAPI switch itself - these require a server restart for the same
reasons TCP port modification does - the socket must be created with root
privilege prior to suing to its execution user.

Cross platform code for OS level authentication is currently defined out (other
than linux), I intend to enable that as testing for these platforms progresses.

Diff:

https://bugzilla.redhat.com/bugzilla/attachment.cgi?id=148370&action=diff

Additional files:

getsocketpeer.c: https://bugzilla.redhat.com/bugzilla/attachment.cgi?id=148371
getsocketpeer.h: https://bugzilla.redhat.com/bugzilla/attachment.cgi?id=148372



-- 
Pete

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