4
When accessing a remote branch (specified as an URL), it may occur that the
5
server requests an authentication.
7
This authentication can be provided in different ways:
9
1. Embedding the user and password
12
bzr branch <scheme>://<user>:<password>@host:port/path
14
* ``scheme``: Any transport protocol requiring authentication.
15
* ``user``: The login used to authenticate.
16
* ``password``: The associated password.
17
* ``host``: The address of the server.
18
* ``port``: The port the server is listening to.
19
* ``path``: The path on the server.
21
2. Embedding the user in the URL and let bzr find the right password or prompt
24
bzr branch <scheme>://<user>@host/path
26
3. Embedding nothing in the URL and let bzr find user and password or prompt
27
for user and/or password::
29
bzr branch <scheme>://host/path
31
This specification proposes a mechanism that will allow users to
32
just use ``bzr branch <scheme>://host/path`` or ``bzr branch
33
<scheme>://<user>@host/path`` and leaves bzr find the ``user``
34
and ``password`` in its configuration files.
36
When no user is specified for ``FTP``, ``SFTP`` or ``SSH``, the actual behavior
37
of ``bzr`` is to default to ``getpass.get_user()``.
39
Any implementation of this specification should respect that behaviour.
41
This specification also proposes a way to describe credentials so that several
42
remote branches can use the same definition. This is particularily important
43
for users handling a lot of passwords and who need to update them on a regular
49
Embedding user and passwords in the command line is a security
50
hazard (see `bug #34685
51
<https://launchpad.net/products/bzr/+bug/34685>`_).
53
Storing passwords in ``~/.bazaar/bazaar.conf`` or ``~/.bazaar/locations.conf``
54
is also a security risk.
56
Typing user and passwords is error-prone and boring.
58
Yet, a safe way to store passwords, while allowing bzr to retrieve them, when
59
needed, could improve the bzr user experience.
61
This specification describes a way to provide user and passwords to bzr while
62
storing them in a relatively safe way.
64
Note that SSH servers can be configured to use keys instead of (``user``,
65
``password``) and, when used with appropriate agents, provide the same kind of
66
comfort this specification aims to provide for all other schemes. Since SSH
67
agents provide a safer way to secure the passwords, this specification is
68
restricted to providing ``user`` but does not provide ``password`` when used
71
Authentication definitions
72
--------------------------
74
There are two kinds of authentication used by the various schemes supported by
79
``FTP`` and ``SFTP`` needs a (``user``, ``password``) to authenticate against a
80
``host`` (SFTP can use SSH keys too, but we don't talk about that in this
81
specification as SSH agents provide a better solution).
83
2. user, realm and password
85
``HTTP`` and ``HTTPS`` needs a (``user, realm, password``) to authenticate
86
against a host. But, by using ``.htaccess`` files, for example, it is possible
87
to define several (``user, realm, password``) for a given ``host``. So what is
88
really needed is (``user``, ``password``, ``host``, ``path``). The ``realm``
89
can be ignored [#ignored_realm]_ as long as it is still presented to the user
90
when prompting for the password (unless someone found a way to declare two
91
different realms for the same path).
93
``HTTP proxy`` can be handled as ``HTTP`` (or ``HTTPS``) by explicitly
94
specifying the appropriate port.
96
.. [#ignored_realm] The true purpose of realms is to allow the same credentials
97
to be reused for disjoint hierarchies. Ignoring them in this specification
98
aims to simplify the user experience while still allowing to share the same
99
credentials for a whole hierarchy.
101
To take all schemes into account, the password will be deduced from a set of
102
authentication definitions (``scheme``, ``host``, ``port``, ``path``, ``user``,
105
* ``scheme``: can be empty (meaning the rest of the definition can be used
106
for any scheme), ``SFTP`` and ``bzr+ssh`` should not be used here, ``ssh``
107
should be used instead since this is the real scheme regarding
110
* ``host``: can be empty (to act as a default for any host),
112
* ``port`` can be empty (useful when an host provides several servers for the
113
same scheme), only numerical values are allowed, this should be used only
114
when the server uses a port different than the scheme standard port,
116
* ``path``: can be empty (FTP or SFTP will never use it),
118
* ``user``: can be empty (``bzr`` will defaults to Python's
119
``getpass.get_user()`` for FTP, SFTP and SSH),
121
* ``password``: can be empty (for security reasons, a user may use the
122
definitions without storing the passwords but want to be prompted ; or the
123
password will be provided by an external plugin via the
124
``password_encoding`` mechanism decribed below). Must be left empty for
127
* ``password_encoding``: can be empty (default is ``plaintext``).
129
Also note that an optional ``verify_certificates=no`` field will allow the
130
connection to ``HTTPS`` hosts that provides a self certified certificate (the
131
default should be to refuse the connection and inform the user). (Not
134
Multiple definitions can be provided and, for a given URL, bzr will select a
135
(``user`` [, ``password``]) based on the following rules :
137
1. the first match wins,
139
2. empty fields match everything,
141
3. ``scheme`` matches even if decorators are used in the requested URL,
143
4. ``host`` matches exactly or act as a domain if it starts with '.'
144
(``project.bzr.sf.net`` will match ``.bzr.sf.net`` but ``projectbzr.sf.net``
145
will not match ``bzr.sf.net``).
147
5. ``port`` matches if included in the requested URL (exact matches only)
149
6. ``path`` matches if included in the requested URL (and by rule #2 above,
150
empty paths will match any provided path).
152
An optional ``password_encoding`` field may specify how the password is encoded
153
but has no impact on the definition selection.
155
Possible values are ``plaintext`` (no encoding at all) and ``base64``. When the
156
field is absent, ``plaintext`` is assumed. Additional encodings may be added in
159
Encoding passwords in ``base64``, while weak, provides protection against
160
accidental reading (if an administrator have to look into the file, he will not
161
see the passwords in clear).
163
This specification intends to ease the authentication providing, not to secure
164
it in the best possible way.
166
Plugins can provide additional password encodings. The provided
167
``netrc_credential_store`` plugin can be used as an example implementation.
169
Future versions of this specification may provide additional
170
encodings [#password_encoding]_.
172
.. [#password_encoding] Additional password encoding methods may be defined
173
that will rely on external means to store the password which, in these
174
cases, will not appear anymore in the definition. It is assumed that
175
additional password encodings will provide a storage outside of the file
176
described here. The ``netrc`` encoding, for example, provides passwords by
177
retrieving them from the ``.netrc`` file.
182
Even if ``~/.bazaar/bazaar.conf`` and ``~/.bazaar/locations.conf`` seems to
183
provide most of the needed infrastructure, we choose to use a dedicated file
184
for the authentication info ``~/.bazaar/authentication.conf`` for the following
187
* allow the user to protect the content of one file only, relaxing security
188
constraints on the others,
190
* while ``locations.conf`` is organized around *local* branches,
191
``authentication.conf`` is organized around *remote* branches or more
192
generally servers. The same authentification definition can even be used
193
for several schemes for servers providing those schemes.
195
``~/.bazaar/authentication.conf`` will use the same file format as
196
``~/.bazaar/bazaar.conf``.
198
Each section describes an authentication definition.
200
The section name is an arbitrary string, only the ``DEFAULT`` value is reserved
201
and should appear as the *last* section.
203
Each section should define:
205
* ``user``: the login to be used,
207
Each section could define:
209
* ``host``: the remote server,
211
* ``port``: the port the server is listening,
213
* ``verify_certificates``: to control certificate verification (useful
214
for self certified hosts). This applies to HTTPS only. Accepted values
215
are yes and no, default to yes.
217
* ``path``: the branch location,
219
* ``password``: the password,
221
* ``password_encoding``: the method used to encode the password if any,
223
The default content of the file will be::
227
This section could define:
229
* ``user``: default user to be used (if not defined the usual
230
bzr way applies, see below).
232
* ``password_encoding``: default password encoding.
237
The use cases described below use the file format defined above.
239
* all FTP connections to the foo.net domain are done with the same (``user``,
242
# Identity on foo.net
249
will provide ('joe', 'secret-pass') for::
251
bzr branch ftp://foo.net/bzr/branch
252
bzr pull ftp://bzr.foo.net/bzr/product/branch/trunk
254
* all connections are done with the same ``user`` (the remote one for which
255
the default bzr one is not appropriate) and the password is always prompted
256
with some exceptions::
258
# Pet projects on hobby.net
269
# Obtain the base64 encoded password by running 'echo -n "secret-pass" | base64'
270
password='c2VjcmV0LXBhc3M='
271
password_encoding=base64
272
verify_certificates=no # Still searching a free certificate provider
275
# Our local user is barbaz, on all remote sites we're known as foobar
278
* an HTTP server and a proxy::
280
# development branches on dev server
299
host=proxy.company.com
304
* source hosting provider declaring sub-domains for each project::
307
# we use SFTP, but SSH is the scheme used for authentication
309
# The leading '.' ensures that 'sf.net' alone doesn't match
318
Depending on the info provided in the URL, bzr will interact with the user in
321
1. ``user`` and ``password`` given in the URL.
325
2. ``user`` given in the URL.
327
Get a password from ``~/.bazaar/authentication.conf`` or prompt
328
for one if none is found.
330
3. No ``user`` given in the URL (and no ``password``).
332
Get a user from ``~/.bazaar/authentication.conf`` or prompt for one if none is
333
found. Continue as 2. (Not implemented yet)
335
Note: A user will be queried only if the server requires it for ``HTTP`` or
336
``HTTPS``, other protocols always require a user.
338
In any case, if the server refuses the authentication, bzr reports to the user
341
Implementation constraints
342
--------------------------
344
* bzr should be able to prompt for a ``user`` for a given (``scheme``, ``host``
345
[, ``realm``]). Note that ``realm`` is available only after a first
346
connection attempt to the server.
348
* No assumptions should be made about the clients of this service
349
(i.e. Transport is the primary target but plugins must be able to use it as
350
well, the definitions used: (``scheme, host, [port,] path``) are general
351
enough to described credentials for ``svn`` servers or LaunchPad XML-RPC
354
* Policies regarding default users may be taken into account by the
355
implementations, there is no good way to represent that in this specification
356
and stays flexible enough to accommodate various needs (default user policies
357
may differ for different schemes and that may be easier to handle in the code
358
than in the authentication file itself).
360
* If no user can be found by the mechanism described above, bzr should still
361
default to ``getpass.get_user()`` and may attempt a second matching to obtain
364
* As this specification proposes a matching between some credentials
365
definitions and real URLs, the implementation provides an optional UI
366
feedback about which credential definition is used. Using ``-Dauth`` will
367
output some traces in the ``.bzr.log`` file metionning the sections
368
used. This allows the user to validate his definitions.
370
Questions and Answers
371
---------------------
373
* What if a ``.authinfo`` file exists ?
375
* It will be ignored,
377
* Automatic (one-time) conversions may be proposed if sufficient demand
380
* What if a ``.netrc`` file exists ?
382
* It is honored if the definition specifies
383
``password_encoding=netrc``.
385
* What mode should the authentication file use ?
387
* 600 read/write for owner only by default, if another mode (more
388
permissive) is used, a warning will be issued to inform the users of the
389
potential risks.(Not implemented yet)
391
* What about using ``seahorse`` on Ubuntu or ``KeyChain Access`` on Mac OS X ?
393
* plugins can be written and registered to handle the associated
394
``password_encoding``.
396
* Could it be possible to encode the whole authentication file with an SSH key
399
* yes and if the user configure a ssh-agent it will not be queried for
400
pass-phrase every time we want to query the file for a password. But
401
that seems a bit extreme for a first version.(Not implemented yet and
404
* Why can't bzr update the authentication file when it queried the user for a
407
* a future version may address that but:
409
1. The user may want to decide which passwords are stored in the file and
412
2. The user should decide if the passwords are encoded (and how) or not
413
(but we may default to base64).
415
3. The right definition may be hard to get right, but reducing it to
416
(``scheme, host, [port,] user, password``) may be a good start. I.e. no
417
path so that all paths on the host will match. The user will have to
418
modify it for more complex configurations anyway.
added
removed
doc/developers/authentication-ring.txt
