CONTRIBUTING.md 15.5 KB
Newer Older
1
2
# Contributing to dbus

3
4
5
6
The guidelines in this file are the ideals; it's better to send a
not-fully-following-guidelines patch than no patch at all, though.  We
can always polish it up.

7
## Source code and issue tracking
8

9
10
11
Source code and issue tracking for the D-Bus specification and its
reference implementation 'dbus' are provided by freedesktop.org Gitlab:
<https://gitlab.freedesktop.org/dbus/dbus>.
12

13
## Reporting security vulnerabilities
14

15
16
If you find a security vulnerability that is not known to the public,
please report it privately to dbus-security@lists.freedesktop.org
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
or by reporting a Gitlab issue at
https://gitlab.freedesktop.org/dbus/dbus/issues/new and marking it
as "confidential".

## Mailing list

The D-Bus mailing list is dbus@lists.freedesktop.org; discussion of
protocol enhancements, new implementations, etc. should go there.

## Code of Conduct

As a freedesktop.org project, dbus follows the Contributor Covenant,
found at: https://www.freedesktop.org/wiki/CodeOfConduct

Please conduct yourself in a respectful and civilised manner when
interacting with community members on mailing lists, IRC, or bug
trackers. The community represents the project as a whole, and abusive
or bullying behaviour is not tolerated by the project.

## Development

D-Bus uses Git as its version control system. The main repository is
hosted on freedesktop.org Gitlab. To clone D-Bus, execute one of the
following commands:

    git clone https://gitlab.freedesktop.org/dbus/dbus.git
    git clone git@gitlab.freedesktop.org:dbus/dbus.git

The second form is the one that allows pushing, but it also requires
an SSH account on the server. The first form allows anonymous
checkouts.

### Branches

D-Bus development happens in multiple branches in parallel. The main
branches are the current stable branch, with an even minor number (like
1.0, 1.2 and 1.4), and the next development branch, with the next odd
number. At the time of writing, the stable branch is dbus 1.12.x and
the development branch is dbus 1.13.x, leading to a new 1.14.x stable
branch in future.

Stable branches are named after the version number itself (`dbus-1.2`,
`dbus-1.4`), whereas the development branch is simply known as
`master`.

New features, enhancements, minor bug fixes, and bug fixes that are
unusually intrusive should always be based on the `master` branch.

Fixes for significant bugs should be developed on the `master` branch
and cherry-picked to the most recent stable branch.

Depending on the release cycles of various Linux distributions, some
older stable branches might continue to receive fixes for security
vulnerabilities (and sometimes major non-security bugs) for a time.
These are announced on the D-Bus mailing list.

Old development branches are not supported at all, and will not receive
any bug fixes - not even for security vulnerabilities. Please do not
use a development branch like 1.13.x in your OS distribution, unless
you can guarantee that you will upgrade to the next stable branch such
as 1.14.x when it becomes available.

### Commits

If you are making changes that you wish to be incorporated upstream,
please do as small commits to your local git tree that are individually
correct, so there is a good history of your changes.

The first line of the commit message should be a single sentence that
describes the change, optionally with a prefix that identifies the
area of the code that is affected.

The body of the commit message should describe what the patch changes
and why, and also note any particular side effects. This shouldn't be
empty on most of the cases. It shouldn't take a lot of effort to write a
commit message for an obvious change, so an empty commit message body is
only acceptable if the questions "What?" and "Why?" are already answered
on the one-line summary.

The lines of the commit message should have at most 76 characters,
to cope with the way git log presents them.

See [notes on commit messages](https://who-t.blogspot.com/2009/12/on-commit-messages.html),
[A Note About Git Commit Messages](https://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html)
or [How to Write a Git Commit Message](https://chris.beams.io/posts/git-commit/)
for recommended reading on writing high-quality commit messages.

Your patches should also include a Signed-off-by line with your name and
email address, indicating that your contribution follows the [Developer's
Certificate of Origin](https://developercertificate.org/). If you're
not the patch's original author, you should also gather S-o-b's by
them (and/or whomever gave the patch to you.) The significance of this
is that it certifies that you created the patch, that it was created
under an appropriate open source license, or provided to you under those
terms. This lets us indicate a chain of responsibility for the copyright
status of the code.

We won't reject patches that lack S-o-b, but it is strongly recommended.

### Sending a merge request

When you consider your changes to be ready for merging to mainline:

* create a personal fork of <https://gitlab.freedesktop.org/dbus/dbus>
  on freedesktop.org Gitlab
* push your changes to your personal fork as a branch
* create a merge request at
  <https://gitlab.freedesktop.org/dbus/dbus/merge_requests>

### Security guidelines
127

John Palmieri's avatar
John Palmieri committed
128
Most of D-Bus is security sensitive.  Guidelines related to that:
129

130
131
132
133
 - avoid `memcpy()`, `sprintf()`, `strlen()`, `snprintf()`, `strlcat()`,
   `strstr()`, `strtok()`, or any of this stuff. Use `DBusString`.
   If `DBusString` doesn't have the feature you need, add it
   to `DBusString`.
134
135

   There are some exceptions, for example
136
   if your strings are just used to index a hash table
137
   and you don't do any parsing/modification of them, perhaps
138
139
   `DBusString` is wasteful and wouldn't help much. But definitely
   if you're doing any parsing, reallocation, etc. use `DBusString`.
140

141
142
 - do not include system headers outside of `dbus-memory.c`,
   `dbus-sysdeps.c`, and other places where they are already
143
   included. This gives us one place to audit all external
144
145
   dependencies on features in libc, etc.

146
 - do not use libc features that are "complicated"
147
   and may contain security holes. For example, you probably shouldn't
148
   try to use `regcomp()` to compile an untrusted regular expression.
149
   Regular expressions are just too complicated, and there are many
150
   different libc implementations out there.
151
152
153
154
155
156

 - we need to design the message bus daemon (and any similar features)
   to use limited privileges, run in a chroot jail, and so on.

http://vsftpd.beasts.org/ has other good security suggestions.

157
### Coding Style
158

159
160
161
162
 - Please follow the coding style and indentation of nearby code.

 - C code uses GNU coding conventions (approximately "gnu" style in
   Emacs), with GLib-like extensions (e.g. lining up function arguments).
163
164

 - Write docs for all non-static functions and structs and so on. try
165
166
   `doxygen Doxyfile` prior to commit and try not to cause any new
   warnings.
167
168
169
170
171
172
173
174
175

 - All external interfaces (network protocols, file formats, etc.)
   should have documented specifications sufficient to allow an
   alternative implementation to be written. Our implementation should
   be strict about specification compliance (should not for example
   heuristically parse a file and accept not-well-formed
   data). Avoiding heuristics is also important for security reasons;
   if it looks funny, ignore it (or exit, or disconnect).

176
### Licensing
177

178
179
180
181
182
Please match the existing licensing (a dual-license: AFL-2.1 or GPL-2+,
recipient's choice). Entirely new modules can be placed under a more
permissive license: to avoid license proliferation, our preferred
permissive license is the variant of the MIT/X11 license used by the
Expat XML library (for example see the top of tools/ci-build.sh).
183

184
### Build systems
185

186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
The primary build system for dbus uses the GNU Autotools suite (Autoconf,
Automake and Libtool). This build system is strongly recommended for
Unix OS integrators. It can also be used to compile dbus for Windows
using the mingw-w64 compiler suite, either by cross-compiling on a Unix
system or by using an environment like MSYS2 on Windows.

There is also a CMake build system. This is primarily there to make it
easier to build dbus on Windows, using either a MSYS2/mingw environment
or the MSVC compiler from Microsoft Visual Studio. It can also be used
on a GNU/Linux system, but this is not recommended for OS integrators.

Changes contributed to dbus must not break the build for either of these
build systems. It is OK for the CMake build system to support fewer
options, support fewer operating systems, have less test coverage or
build fewer non-essential programs, but it must continue to work on at
least GNU/Linux and Windows.

### Environment variables

These are some of the environment variables that are used by the D-Bus
client library.

* `DBUS_VERBOSE=1`

  Turns on printing verbose messages. This only works if D-Bus has been
  compiled with `--enable-verbose-mode`.
212

213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
* `DBUS_MALLOC_FAIL_NTH=n`

  Can be set to a number, causing every *n*th call to `dbus_alloc` or
  `dbus_realloc` to fail. This only works if D-Bus has been compiled with
  `--enable-embedded-tests`.

* `DBUS_MALLOC_FAIL_GREATER_THAN=n`

  Can be set to a number, causing every call to `dbus_alloc` or
  `dbus_realloc` to fail if the number of bytes to be allocated is greater
  than the specified number. This only works if D-Bus has been compiled with
  `--enable-embedded-tests`.

* `DBUS_TEST_MALLOC_FAILURES=n`

  Many of the D-Bus tests will run over and over, once for each `malloc`
  involved in the test. Each run will fail a different `malloc`, plus some
  number of `malloc`s following that malloc (because a fair number of bugs
  only happen if two or more `malloc`s fail in a row, e.g. error recovery
  that itself involves `malloc`).  This environment variable sets the
  number of consecutive `malloc`s to fail.

  Here's why you care: If set to 0, then the `malloc` checking is skipped,
  which makes the test suite a lot faster. Just run with this
  environment variable unset before you commit.

### Tests

Please try to write test coverage for all new functionality.
We have two broad categories of tests.

The *modular tests* are enabled by configuring with
`--enable-modular-tests`. These mostly use GLib's GTest framework,
and are standalone programs that do not affect the contents of the
production dbus library and programs. Most of them can be installed
alongside the library and programs by configuring with
`--enable-installed-tests`.

The *embedded tests* are enabled by configuring with
`--enable-embedded-tests`. Unlike the modular tests, enabling the
embedded tests adds special code to libdbus and dbus-daemon, some of
which may harm performance or security. A production version of dbus
that will be included in an operating system should never have the
embedded tests enabled.

If possible, new test coverage should be provided via modular tests,
preferably using GLib's GTest framework. `test/dbus-daemon.c` is a good
example.

## Information for maintainers

This section is not directly relevant to infrequent contributors.

### Releasing
267

John Palmieri's avatar
John Palmieri committed
268
To make a release of D-Bus, do the following:
269

270
 - check out a fresh copy from Git
271

272
 - verify that the libtool versioning/library soname is
273
274
   changed if it needs to be, or not changed if not

Simon McVittie's avatar
Simon McVittie committed
275
 - update the file NEWS based on the git history
276

277
278
279
280
 - verify that the version number of dbus-specification.xml is
   changed if it needs to be; if changes have been made, update the
   release date in that file

Simon McVittie's avatar
Simon McVittie committed
281
 - update the AUTHORS file with "make update-authors" if necessary
282

Simon McVittie's avatar
Simon McVittie committed
283
284
285
 - the version number should have major.minor.micro, even
   if micro is 0, i.e. "1.0.0" and "1.2.0" not "1.0"/"1.2"; the micro
   version should be even for releases, and odd for intermediate snapshots
286

287
288
289
290
 - "make distcheck" (DO NOT just "make dist" - pass the check!)

 - if make distcheck fails, fix it.

291
 - once distcheck succeeds, "git commit -a".  This is the version
292
   of the tree that corresponds exactly to the released tarball.
293

294
 - tag the tree with "git tag -s -m 'Released X.Y.Z' dbus-X.Y.Z"
295
   where X.Y.Z is the version of the release.  If you can't sign
Thiago Macieira's avatar
Thiago Macieira committed
296
297
   then simply created an unsigned annotated tag:
   "git tag -a -m 'Released X.Y.Z' dbus-X.Y.Z".
298

299
 - bump the version number up in configure.ac (so the micro version is odd),
Simon McVittie's avatar
Simon McVittie committed
300
   and commit it.  Make sure you do this *after* tagging the previous
301
   release! The idea is that git has a newer version number
302
303
   than anything released. Similarly, bump the version number of
   dbus-specification.xml and set the release date to "(not finalized)".
304

305
306
 - merge the branch you've released to the chronologically-later
   branch (usually "master"). You'll probably have to fix a merge
307
   conflict in configure.ac (the version number).
308

309
310
 - push your changes and the tag to the central repository with
     git push origin master dbus-X.Y dbus-X.Y.Z
311

Thiago Macieira's avatar
Thiago Macieira committed
312
 - scp your tarball to freedesktop.org server and copy it to
313
   dbus.freedesktop.org:/srv/dbus.freedesktop.org/www/releases/dbus/dbus-X.Y.Z.tar.xz.
Thiago Macieira's avatar
Thiago Macieira committed
314
   This should be possible if you're in group "dbus"
315

316
317
 - Update the online documentation with `make -C doc maintainer-upload-docs`.

Joe Shaw's avatar
Joe Shaw committed
318
 - update the wiki page http://www.freedesktop.org/Software/dbus by
319
320
321
   adding the new release under the Download heading. Then, cut the
   link and changelog for the previous that was there.

322
 - post to dbus@lists.freedesktop.org announcing the release.
323

324
### Making a ".0" stable release
325

326
327
328
We create a branch for each stable release. The branch name should be
dbus-X.Y which is a branch that has releases versioned X.Y.Z;
changes on a stable branch should be limited to significant bug fixes.
329

330
331
332
333
334
335
Because we won't make minor changes like keeping up with the latest
deprecations on a stable branch, stable branches should turn off the
gcc warning for deprecated declarations (e.g. see commit 4ebb275ab7).

Be extra-careful not to merge master (or any branch based on master) into a
stable branch.
336

337
To branch:
338
339
340

    git branch dbus-X.Y

341
and upload the branch tag to the server:
342
343

    git push origin dbus-X.Y
344

345
To develop in this branch:
346

347
348
    git checkout dbus-X.Y

349
### Code reviews
350

351
The commit rules are approximately these:
352

353
 - Fixes that don't affect API or protocol can be committed
354
355
356
   if any one qualified reviewer other than patch author
   reviews and approves

357
358
 - For fixes that do affect API or protocol, two people
   in the reviewer group have to review and approve the commit.
359

360
 - If there's a live unresolved controversy about a change,
361
362
   don't commit it while the argument is still raging.

363
 - At their discretion, members of the reviewer group may also commit
364
365
366
367
368
369
370
   branches/patches under these conditions:

   - the branch does not add or change API, ABI or wire-protocol

   - the branch solves a known problem and is covered by the regression tests

   - there are no objections from the rest of the review group within
371
     a week of the merge request being opened
372

373
374
   - the committer gets a positive review on the merge request from someone
     they consider qualified to review the change (e.g. a colleague with D-Bus
375
376
     experience; not necessarily a member of the reviewer group)

377
378
379
 - Regardless of reviews, to commit a patch:

    - `make check` must pass
380
    - the test suite must be extended to cover the new code
381
      as much as reasonably feasible (see Tests above)
382
    - the patch has to follow the portability, security, and
383
      style guidelines
384
    - the patch should as much as reasonable do one thing,
385
      not many unrelated changes
386

387
388
389
   No reviewer should approve a patch without these attributes, and
   failure on these points is grounds for reverting the patch.

390
391
392
The reviewer group that can approve patches consists of the members
of <https://gitlab.freedesktop.org/dbus/dbus/project_members> with
"Maintainer" or "Owner" status.