2 This document tries to describe the software layout and design of the library.
3 It should provide some help for contributing code to this package.
5 CONTRIBUTING TO NSS-LDAPD
6 =========================
8 Contributions to nss-ldapd are most welcome. However not all contributions
9 will be automatically integrated. Some notes:
11 * for large changes it is a good idea to send an email first
12 * send your patches in unified diff (diff -u) format
13 * try to use the svn version of the software to develop the patch
14 * clearly state which problem you're trying to solve and how this is
16 * please follow the existing coding conventions
17 * patches will be integrated on a best-effort bases
18 * please test the patch and include information on testing with the patch
19 (platforms tested, etc)
20 * contributions will be acknowledged in the AUTHORS file
21 * include a copyright statement in the patched code if you feel the
22 contribution is significant enough (e.g. more than a few lines)
23 * when including third-party code, retain copyright information (copyright
24 holder and license) and ensure that the license is LGPL compatible
26 Please contact Arthur de Jong <arthur@ch.tudelft.nl> if you want to
27 contribute or use the Debian BTS if you're using the Debian package.
33 For building svn snapshots the following tools are needed:
35 * autoconf (2.61 is used but 2.59 is minimal)
36 * automake (1.10 is used)
37 * check (0.9.5 is used)
39 and of course the usual build tools (gcc/make/etc). Also see debian/control
40 (Build-Depends field) for libraries you need.
42 To build the svn snapshot run the autogen.sh shell script to build the
43 configure script. When developing patches please use --enable-warnings with
44 configure and don't introduce too many new warnings. For building the manual
45 pages docbook2x is used.
51 A new versioning scheme was chosen over the nss_ldap release scheme. The
52 scheme is a simple major.minor numbering starting with 0.1. Until a 1.0
53 release is made the code will be considered work in progress. The interfaces
54 may change and features may be added and removed.
60 The basic design splits the functionality in two parts. The NSS part
61 interfaces with libc and translates the NSS requests into simple generic
62 requests (e.g. "get user with name test", "get group with gid 101" or "get all
63 shadow entries"). Translating these requests into LDAP requests is then the
64 job of the daemon (nslcd) so that the NSS part won't have to know anything
65 about LDAP (in fact replacing it with another lookup method is very simple).
67 nslcd -> OpenLDAP -> LDAP server
69 libc NSS -> libnss_ldap.so
73 * make it as simple as possible
74 * design as specified above
75 * simpler configuration and semantics
76 * simpler, clearer and completer documentation
77 * split source code into directories (src, src/hacks, src/aix, src/irs, etc)
78 * get rid of unneeded code and complexity
79 * split complexity in two parts (LDAP interface in server, NSS interface in
81 * have a stable, easily maintainable piece of quality software
87 The NSS part is implemented in files in the nss directory. The functions are
88 split into files according to the database they support. All functions look
91 _nss_ldap_FUNCTION_r(...)
92 This function opens the connection to the nslcd (with a time-out) builds the
93 correct data structures and does a request (write()) to the nslcd waiting
94 for an answer (again with a time-out)
96 Currently a number of macros are used to build most of the function bodies for
97 these functions. A more elegant solution is welcome.
100 http://mirrors.usc.edu/pub/gnu/Manuals/glibc-2.2.3/html_chapter/libc_28.html#SEC596
101 http://www.gnu.org/software/libc/manual/html_node/index.html
104 THE COMMUNICATIONS PROTOCOL
105 ===========================
107 The protocol used for communicating between the NSS library and the nslcd
108 daemon is very simple and almost fully described in the nslcd.h header file.
109 The nslcd-common.h header file defines some macros that are used for reading
110 and writing protocol entities (strings, 32-bit integers, etc).
112 Some of the protocol handling code is automatically generated from the macros
113 defined in nslcd.h. This cannot be done automatically in every case though so
114 changing the protocol requires manual checking in the relevant source files in
115 both the nss and the nslcd directories.
117 If the protocol is changed in an incompatible way the protocol version should
118 be incremented in nslcd.h. There is currently no versioning scheme available
121 A special module (common/tio.c) was made so we can define simpler semantics
122 for time-out values and buffer sizes. Both tha NSS library and nslcd use this
123 module which means that it includes functionality that is needed for both
124 (e.g. large write buffers for the server part and large resettable read
125 buffers for the NSS part). Maybe building two modules from the same source
126 with different features in them is an option (e.g. the NSS part needs the
127 read buffers and handling of SIGPIPE and the nslcd part needs the write
128 buffers and possibly flushing in the background).
134 At the server end a dispatcher picks up the request and delegates it to one of
135 the database specific functions.
138 This functions fills in the correct parameters from the request. This
139 function should write responses to the stream. Almost all these functions
140 are generated from a macro in common.h.
146 This design does open up the system to more potential security issues as there
147 is now a local interface to a daemon with privileges. Before processes could
148 only potentially exploit bugs in the library and gain the privileges of the
149 process that was doing the name lookups. In this case the privileges of the
150 daemon are potentially exposed.
152 The deamon should be changed to set a specific less-privileged user and
153 group to minimize the riscs. Code for this is already in place. Configuration
154 options should be added and the Debian packaging should use this.