openstack/swift
Code Issues Proposed changes

Document access control lists (ACLs)

Browse Source 
Documents the syntax and meaning of container ACLs. Account ACLs
were already pretty well documented. However the account
ACL text was moved as part of this change.

TempAuth and keystoneauth have diffent ACLs. However, I decided
to describe both in one section/table because there are many
"examples" of ACLs in other documents, and it's better that
someone coming here from those sources become aware that the
specific ACL might not apply to them. In addition, the
referrer and .rlistings is common to both.

Some changes were also made to the api-ref document. The doc
and api-ref documents are published as seperate documents, so
the cross references from the api-ref section will not work
until this patch merges and the documents are rebuilt.

Change-Id: Icd2d6c278050c263b833ae76545c041f54fae68d
This commit is contained in:
Donagh McCabe 2016-09-21 15:23:03 +01:00 committed by donagh-mccabe
parent 71d3ce36b3
commit c0fdc53b49
5 changed files with 400 additions and 84 deletions
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39
api-ref/source/parameters.yaml
View File

@ -259,6 +259,31 @@ Transfer-Encoding:
in: header
required: false
type: string
X-Account-Access-Control_req:
description: |
**Note**: `X-Account-Access-Control` is not supported by Keystone auth.
Sets an account access control list (ACL) that grants access to
containers and objects in the account.
See `Account ACLs
<http://docs.openstack.org/developer/swift/overview_acl.html#account-acls>`_
for more information.
in: header
required: false
type: string
X-Account-Access-Control_resp:
description: |
**Note**: `X-Account-Access-Control` is not supported by Keystone auth.
The account access control list (ACL) that grants access to
containers and objects in the account.
If there is no ACL, this header is not returned by this operation.
See `Account ACLs
<http://docs.openstack.org/developer/swift/overview_acl.html#account-acls>`_
for more information.
in: header
required: false
type: string
X-Account-Bytes-Used:
description: |
The total number of bytes that are stored in
@ -527,7 +552,9 @@ X-Container-Read:
or to perform a GET or HEAD operation on the container itself.
The format and scope of the ACL is dependent on the authorization system
used by the Object Storage service.
used by the Object Storage service. See `Container ACLs
<http://docs.openstack.org/developer/swift/overview_acl.html#container-acls>`_
for more information.
in: header
required: false
type: string
@ -535,6 +562,9 @@ X-Container-Read_resp:
description: |
The ACL that grants read access. If there is no ACL, this
header is not returned by this operation.
See `Container ACLs
<http://docs.openstack.org/developer/swift/overview_acl.html#container-acls>`_
for more information.
in: header
required: false
type: string
@ -582,7 +612,9 @@ X-Container-Write:
metadata.
The format of the ACL is dependent on the authorization system
used by the Object Storage service.
used by the Object Storage service. See `Container ACLs
<http://docs.openstack.org/developer/swift/overview_acl.html#container-acls>`_
for more information.
in: header
required: false
@ -591,6 +623,9 @@ X-Container-Write_resp:
description:
The ACL that grants write access. If there is no ACL,
this header is not returned by this operation.
See `Container ACLs
<http://docs.openstack.org/developer/swift/overview_acl.html#container-acls>`_
for more information.
in: header
required: false
type: string

10
api-ref/source/storage-account-services.inc
View File

@ -109,6 +109,7 @@ Response Parameters
- X-Account-Storage-Policy-name-Container-Count: X-Account-Storage-Policy-name-Container-Count
- X-Account-Storage-Policy-name-Object-Count: X-Account-Storage-Policy-name-Object-Count
- X-Account-Meta-Quota-Bytes: X-Account-Meta-Quota-Bytes_resp
- X-Account-Access-Control: X-Account-Access-Control_resp
- Content-Type: Content-Type_listing_resp
- count: count
- bytes: bytes
@ -257,6 +258,7 @@ Request
- X-Account-Meta-Temp-URL-Key-2: X-Account-Meta-Temp-URL-Key-2_req
- X-Account-Meta-name: X-Account-Meta-name_req
- X-Remove-Account-name: X-Remove-Account-name
- X-Account-Access-Control: X-Account-Access-Control_req
- X-Trans-Id-Extra: X-Trans-Id-Extra
@ -359,9 +361,5 @@ Response Parameters
- X-Account-Storage-Policy-name-Container-Count: X-Account-Storage-Policy-name-Container-Count
- X-Account-Storage-Policy-name-Object-Count: X-Account-Storage-Policy-name-Object-Count
- X-Account-Meta-Quota-Bytes: X-Account-Meta-Quota-Bytes_resp
- Content-Type: Content-Type_cud_resp
- X-Account-Access-Control: X-Account-Access-Control_resp
- Content-Type: Content-Type_cud_resp

1
doc/source/index.rst
View File

@ -48,6 +48,7 @@ Overview and Concepts
overview_policies
overview_reaper
overview_auth
overview_acl
overview_replication
ratelimit
overview_large_objects

300
doc/source/overview_acl.rst Normal file
View File

@ -0,0 +1,300 @@
===========================
Access Control Lists (ACLs)
===========================
Normally to create, read and modify containers and objects, you must have the
appropriate roles on the project associated with the account, i.e., you
must be the owner of the account. However, an owner can grant access to
other users by using an Access Control List (ACL).
There are two types of ACLs:
- :ref:`container_acls`. These are specified on a container and
apply to that container only and the objects in the container.
- :ref:`account_acls`. These are specified at the account level and
apply to all containers and objects in the account.
.. _container_acls:
--------------
Container ACLs
--------------
Container ACLs are stored in the ``X-Container-Write`` and ``X-Container-Read``
metadata. The scope of the ACL is limited to the container where the
metadata is set and the objects in the container. In addition:
- ``X-Container-Write`` grants the ability to perform PUT, POST and DELETE
operations on objects within a container. It does not grant the ability
to perform POST or DELETE operations on the container itself. Some ACL
elements also grant the ability to perform HEAD or GET operations on the
container.
- ``X-Container-Read`` grants the ability to perform GET and HEAD
operations on objects within a container. Some of the ACL elements also grant
the ability to perform HEAD or GET operations on the container itself.
However, a container ACL does not allow access to privileged metadata (such
as ``X-Container-Sync-Key``).
Container ACLs use the "V1" ACL syntax which is a comma separated string
of elements as shown in the following example::
.r:*,.rlistings,7ec59e87c6584c348b563254aae4c221:*
Spaces may occur between elements as shown in the following example::
.r : *, .rlistings, 7ec59e87c6584c348b563254aae4c221:*
However, these spaces are removed from the value stored in the
``X-Container-Write`` and ``X-Container-Read`` metadata. In addition,
the ``.r:`` string can be written as ``.referrer:``, but is stored as ``.r:``.
While all auth systems use
the same syntax, the meaning of some elements
is different because of the different concepts used by different
auth systems as explained in the following sections:
- :ref:`acl_common_elements`
- :ref:`acl_keystone_elements`
- :ref:`acl_tempauth_elements`
.. _acl_common_elements:
Common ACL Elements
-------------------
The following table describes elements of an ACL that are
supported by both Keystone auth and TempAuth. These elements
should only be used with ``X-Container-Read`` (with the exception
of ``.rlistings``, an error will occur if used with
``X-Container-Write``):
============================== ================================================
Element Description
============================== ================================================
``.r:*`` Any user has access to objects. No token is
required in the request.
``.r:<referrer>`` The referrer is granted access to objects. The
referrer is identified by the ``Referer``
request header in the request. No token is
required.
``.r:-<referrer>`` This syntax (with "-" prepended to the
referrer) is supported. However, it does not
deny access if another element (e.g., ``.r:*``)
grants access.
``.rlistings`` Any user can perform a HEAD or GET operation
on the container provided the user also has
read access on objects (e.g., also has ``.r:*``
or ``.r:<referrer>``. No token is required.
============================== ================================================
.. _acl_keystone_elements:
Keystone Auth ACL Elements
--------------------------
The following table describes elements of an ACL that are
supported only by Keystone auth. Keystone auth also supports
the elements described in :ref:`acl_common_elements`.
A token must be included in the request for any of these ACL elements
to take effect.
============================== ================================================
Element Description
============================== ================================================
``<project-id>:<user-id>`` The specified user, provided a token
scoped to the project is included
in the request, is granted access.
Access to the container is also granted
when used in ``X-Container-Read``.
``<project-id>:*`` Any user with a role in the specified Keystone
project has access. A token scoped to the
project must be included in the request.
Access to the container is also granted
when used in ``X-Container-Read``.
``*:<user-id>`` The specified user has access. A token
for the user (scoped to any
project) must be included in the request.
Access to the container is also granted
when used in ``X-Container-Read``.
``*:*`` Any user has access.
Access to the container is also granted
when used in ``X-Container-Read``.
The ``*:*`` element differs from the ``.r:*``
element because
``*:*`` requires that a valid token is
included in the request whereas ``.r:*``
does not require a token. In addition,
``.r:*`` does not grant access to the
container listing.
============================== ================================================
.. note::
Keystone project (tenant) or user *names* (i.e.,
``<project-name>:<user-name``) must no longer be
used because with the introduction
of domains in Keystone, names are not globally unique. You should
use user and project *ids* instead.
For backwards compatibility, ACLs using names will be granted by
keystoneauth when it can be established that
the grantee project, the grantee user and the project being
accessed are either not yet in a domain (e.g. the ``X-Auth-Token`` has
been obtained via the Keystone V2 API) or are all in the default domain
to which legacy accounts would have been migrated.
.. _acl_tempauth_elements:
TempAuth ACL Elements
---------------------
The following table describes elements of an ACL that are
supported only by TempAuth. TempAuth auth also supports
the elements described in :ref:`acl_common_elements`.
============================== ================================================
Element Description
============================== ================================================
``<user-name>`` The named user is granted access. The
wildcard ("*") character is not supported.
A token from the user must be included in the
request.
============================== ================================================
----------------------
Container ACL Examples
----------------------
Container ACLs may be set by including ``X-Container-Write`` and/or
``X-Container-Read`` headers with a PUT or a POST request to the container URL.
The following examples use the ``swift`` command line client which support
these headers being set via its ``--write-acl`` and ``--read-acl`` options.
Example: Public Container
-------------------------
The following allows anybody to list objects in the ``www`` container and
download objects. The users do not need to include a token in
their request. This ACL is commonly referred to as making the
container "public". It is useful when used with :ref:`staticweb`::
swift post www --read-acl ".r:*,.rlistings"
Example: Shared Writable Container
----------------------------------
The following allows anybody to upload or download objects. However, to
download an object, the exact name of the object must be known since
users cannot list the objects in the container.
The users must include a Keystone token in the upload request. However, it does not
need to be scoped to the project associated with the container::
swift post www --read-acl ".r:*" --write-acl "*:*"
Example: Sharing a Container with Project Members
-------------------------------------------------
The following allows any member of the ``77b8f82565f14814bece56e50c4c240f``
project to upload and download objects or to list the contents
of the ``www`` container. A token scoped to the ``77b8f82565f14814bece56e50c4c240f``
project must be included in the request::
swift post www --read-acl "77b8f82565f14814bece56e50c4c240f:*" \
--write-acl "77b8f82565f14814bece56e50c4c240f:*"
Example: Allowing a Referrer Domain to Download Objects
-------------------------------------------------------
The following allows any request from
the ``example.com`` domain to access an object in the container::
swift post www --read-acl ".r:.example.com"
However, the request from the user **must** contain the appropriate
`Referer` header as shown in this example request::
curl -i $publicURL/www/document --head -H "Referer: http://www.example.com/index.html"
.. note::
The `Referer` header is included in requests by many browsers. However,
since it is easy to create a request with any desired value in the
`Referer` header, the referrer ACL has very weak security.
.. _account_acls:
------------
Account ACLs
------------
.. note::
Account ACLs are not currently supported by Keystone auth
The ``X-Account-Access-Control`` header is used to specify
account-level ACLs in a format specific to the auth system.
These headers are visible and settable only by account owners (those for whom
``swift_owner`` is true).
Behavior of account ACLs is auth-system-dependent. In the case of TempAuth,
if an authenticated user has membership in a group which is listed in the
ACL, then the user is allowed the access level of that ACL.
Account ACLs use the "V2" ACL syntax, which is a JSON dictionary with keys
named "admin", "read-write", and "read-only". (Note the case sensitivity.)
An example value for the ``X-Account-Access-Control`` header looks like this,
where ``a``, ``b`` and ``c`` are user names::
{"admin":["a","b"],"read-only":["c"]}
Keys may be absent (as shown in above example).
The recommended way to generate ACL strings is as follows::
from swift.common.middleware.acl import format_acl
acl_data = { 'admin': ['alice'], 'read-write': ['bob', 'carol'] }
acl_string = format_acl(version=2, acl_dict=acl_data)
Using the :func:`format_acl` method will ensure
that JSON is encoded as ASCII (using e.g. '\u1234' for Unicode). While
it's permissible to manually send ``curl`` commands containing
``X-Account-Access-Control`` headers, you should exercise caution when
doing so, due to the potential for human error.
Within the JSON dictionary stored in ``X-Account-Access-Control``, the keys
have the following meanings:
============ ==============================================================
Access Level Description
============ ==============================================================
read-only These identities can read *everything* (except privileged
headers) in the account. Specifically, a user with read-only
account access can get a list of containers in the account,
list the contents of any container, retrieve any object, and
see the (non-privileged) headers of the account, any
container, or any object.
read-write These identities can read or write (or create) any container.
A user with read-write account access can create new
containers, set any unprivileged container headers, overwrite
objects, delete containers, etc. A read-write user can NOT
set account headers (or perform any PUT/POST/DELETE requests
on the account).
admin These identities have "swift_owner" privileges. A user with
admin account access can do anything the account owner can,
including setting account headers and any privileged headers
-- and thus granting read-only, read-write, or admin access
to other users.
============ ==============================================================
For more details, see :mod:`swift.common.middleware.tempauth`. For details
on the ACL format, see :mod:`swift.common.middleware.acl`.

134
doc/source/overview_auth.rst
View File

@ -3,12 +3,11 @@ The Auth System
===============
--------
TempAuth
Overview
--------
The auth system for Swift is loosely based on the auth system from the existing
Rackspace architecture -- actually from a few existing auth systems -- and is
therefore a bit disjointed. The distilled points about it are:
Swift supports a number of auth systems that share the following common
characteristics:
* The authentication/authorization part can be an external system or a
subsystem run within Swift as WSGI middleware
@ -26,91 +25,69 @@ validation.
Swift will make calls to the auth system, giving the auth token to be
validated. For a valid token, the auth system responds with an overall
expiration in seconds from now. Swift will cache the token up to the expiration
expiration time in seconds from now. To avoid the overhead in validating the same
token over and over again, Swift will cache the
token for a configurable time, but no longer than the expiration
time.
The included TempAuth also has the concept of admin and non-admin users
The Swift project includes two auth systems:
- :ref:`temp_auth`
- :ref:`keystone_auth`
It is also possible to write your own auth system as described in
:ref:`extending_auth`.
.. _temp_auth:
--------
TempAuth
--------
The included TempAuth has the concept of admin and non-admin users
within an account. Admin users can do anything within the account.
Non-admin users can only perform operations per container based on the
container's X-Container-Read and X-Container-Write ACLs. Container ACLs
use the "V1" ACL syntax, which looks like this:
``name1, name2, .r:referrer1.com, .r:-bad.referrer1.com, .rlistings``
For more information on ACLs, see :mod:`swift.common.middleware.acl`.
Additionally, if the auth system sets the request environ's swift_owner key to
True, the proxy will return additional header information in some requests,
such as the X-Container-Sync-Key for a container GET or HEAD.
In addition to container ACLs, TempAuth allows account-level ACLs. Any auth
system may use the special header ``X-Account-Access-Control`` to specify
account-level ACLs in a format specific to that auth system. (Following the
TempAuth format is strongly recommended.) These headers are visible and
settable only by account owners (those for whom ``swift_owner`` is true).
Behavior of account ACLs is auth-system-dependent. In the case of TempAuth,
if an authenticated user has membership in a group which is listed in the
ACL, then the user is allowed the access level of that ACL.
Account ACLs use the "V2" ACL syntax, which is a JSON dictionary with keys
named "admin", "read-write", and "read-only". (Note the case sensitivity.)
An example value for the ``X-Account-Access-Control`` header looks like this:
``{"admin":["a","b"],"read-only":["c"]}`` Keys may be absent (as shown).
The recommended way to generate ACL strings is as follows::
from swift.common.middleware.acl import format_acl
acl_data = { 'admin': ['alice'], 'read-write': ['bob', 'carol'] }
acl_string = format_acl(version=2, acl_dict=acl_data)
Using the :func:`format_acl` method will ensure
that JSON is encoded as ASCII (using e.g. '\u1234' for Unicode). While
it's permissible to manually send ``curl`` commands containing
``X-Account-Access-Control`` headers, you should exercise caution when
doing so, due to the potential for human error.
Within the JSON dictionary stored in ``X-Account-Access-Control``, the keys
have the following meanings:
============ ==============================================================
Access Level Description
============ ==============================================================
read-only These identities can read *everything* (except privileged
headers) in the account. Specifically, a user with read-only
account access can get a list of containers in the account,
list the contents of any container, retrieve any object, and
see the (non-privileged) headers of the account, any
container, or any object.
read-write These identities can read or write (or create) any container.
A user with read-write account access can create new
containers, set any unprivileged container headers, overwrite
objects, delete containers, etc. A read-write user can NOT
set account headers (or perform any PUT/POST/DELETE requests
on the account).
admin These identities have "swift_owner" privileges. A user with
admin account access can do anything the account owner can,
including setting account headers and any privileged headers
-- and thus granting read-only, read-write, or admin access
to other users.
============ ==============================================================
For more details, see :mod:`swift.common.middleware.tempauth`. For details
on the ACL format, see :mod:`swift.common.middleware.acl`.
Non-admin users can only perform read operations. However, some
privileged metadata such as X-Container-Sync-Key is not accessible to
non-admin users.
Users with the special group ``.reseller_admin`` can operate on any account.
For an example usage please see :mod:`swift.common.middleware.tempauth`.
If a request is coming from a reseller the auth system sets the request environ
reseller_request to True. This can be used by other middlewares.
Other users may be granted the ability to perform operations on
an account or container via ACLs. TempAuth supports two types of ACL:
- Per container ACLs based on the
container's ``X-Container-Read`` and ``X-Container-Write`` metadata. See
:ref:`container_acls` for more information.
- Per account ACLs based on the account's ``X-Account-Access-Control``
metadata. For more information see :ref:`account_acls`.
TempAuth will now allow OPTIONS requests to go through without a token.
The user starts a session by sending a REST request to the auth system to
receive the auth token and a URL to the Swift system.
The TempAuth middleware is responsible for creating its own tokens. A user
makes a request containing their username and password and TempAuth
responds with a token. This token is then used to perform subsequent
requests on the user's account, containers and objects.
.. _keystone_auth:
-------------
Keystone Auth
-------------
Swift is able to authenticate against OpenStack Keystone_ via the
:ref:`keystoneauth` middleware.
Swift is able to authenticate against OpenStack Keystone_. In this
environment, Keystone is responsible for creating and validating
tokens. The :ref:`keystoneauth` middleware is responsible for
implementing the auth system within Swift as described here.
The :ref:`keystoneauth` middleware supports per container based ACLs on the
container's ``X-Container-Read`` and ``X-Container-Write`` metadata.
For more information see :ref:`container_acls`.
The account-level ACL is not supported by Keystone auth.
In order to use the ``keystoneauth`` middleware the ``auth_token``
middleware from KeystoneMiddleware_ will need to be configured.
@ -383,13 +360,18 @@ keystone with Swift:
If this ``openstack`` command fails then it is likely that there is a problem
with the ``authtoken`` configuration.
.. _extending_auth:
--------------
Extending Auth
--------------
TempAuth is written as wsgi middleware, so implementing your own auth is as
easy as writing new wsgi middleware, and plugging it in to the proxy server.
The Keystone project and the Swauth project are examples of additional auth
services.
The `Swauth <https://github.com/openstack/swauth>`_ project is an example of
an additional auth service.
See :doc:`development_auth` for detailed information on extending the
auth system.
Also, see :doc:`development_auth`.