LDAP Authentication
New in version Jewel.
You can delegate the Ceph Object Gateway authentication to an LDAP server.
How it works
The Ceph Object Gateway extracts the users LDAP credentials from a token. A search filter is constructed with the user name. The Ceph Object Gateway uses the configured service account to search the directory for a matching entry. If an entry is found, the Ceph Object Gateway attempts to bind to the found distinguished name with the password from the token. If the credentials are valid, the bind will succeed, and the Ceph Object Gateway will grant access and radosgw-user will be created with the provided username.
You can limit the allowed users by setting the base for the search to a specific organizational unit or by specifying a custom search filter, for example requiring specific group membership, custom object classes, or attributes.
The LDAP credentials must be available on the server to perform the LDAP
authentication. Make sure to set the rgw
log level low enough to hide the
base-64-encoded credentials / access tokens.
Requirements
LDAP or Active Directory: A running LDAP instance accessible by the Ceph Object Gateway
Service account: LDAP credentials to be used by the Ceph Object Gateway with search permissions
User account: At least one user account in the LDAP directory
Do not overlap LDAP and local users: You should not use the same user names for local users and for users being authenticated by using LDAP. The Ceph Object Gateway cannot distinguish them and it treats them as the same user.
Sanity checks
Use the ldapsearch
utility to verify the service account or the LDAP connection:
# ldapsearch -x -D "uid=ceph,ou=system,dc=example,dc=com" -W \
-H ldaps://example.com -b "ou=users,dc=example,dc=com" 'uid=*' dn
Note
Make sure to use the same LDAP parameters like in the Ceph configuration file to eliminate possible problems.
Configuring the Ceph Object Gateway to use LDAP authentication
The following parameters in the Ceph configuration file are related to the LDAP authentication:
rgw_s3_auth_use_ldap
: Set this totrue
to enable S3 authentication with LDAPrgw_ldap_uri
: Specifies the LDAP server to use. Make sure to use theldaps://<fqdn>:<port>
parameter to not transmit clear text credentials over the wire.rgw_ldap_binddn
: The Distinguished Name (DN) of the service account used by the Ceph Object Gatewayrgw_ldap_secret
: Path to file containing credentials forrgw_ldap_binddn
rgw_ldap_searchdn
: Specifies the base in the directory information tree for searching users. This might be your users organizational unit or some more specific Organizational Unit (OU).rgw_ldap_dnattr
: The attribute being used in the constructed search filter to match a username. Depending on your Directory Information Tree (DIT) this would probably beuid
orcn
. The generated filter string will be, e.g.,cn=some_username
.rgw_ldap_searchfilter
: If not specified, the Ceph Object Gateway automatically constructs the search filter with thergw_ldap_dnattr
setting. Use this parameter to narrow the list of allowed users in very flexible ways. Consult the Using a custom search filter to limit user access section for details
Using a custom search filter to limit user access
There are two ways to use the rgw_search_filter
parameter:
Specifying a partial filter to further limit the constructed search filter
An example for a partial filter:
"objectclass=inetorgperson"
The Ceph Object Gateway will generate the search filter as usual with the
user name from the token and the value of rgw_ldap_dnattr
. The constructed
filter is then combined with the partial filter from the rgw_search_filter
attribute. Depending on the user name and the settings the final search filter
might become:
"(&(uid=hari)(objectclass=inetorgperson))"
So user hari
will only be granted access if he is found in the LDAP
directory, has an object class of inetorgperson
, and did specify a valid
password.
Specifying a complete filter
A complete filter must contain a @USERNAME@
token which will be substituted
with the user name during the authentication attempt. The rgw_ldap_dnattr
parameter is not used anymore in this case. For example, to limit valid users
to a specific group, use the following filter:
"(&(uid=@USERNAME@)(memberOf=cn=ceph-users,ou=groups,dc=mycompany,dc=com))"
Note
Using the memberOf
attribute in LDAP searches requires server side
support from you specific LDAP server implementation.
Generating an access token for LDAP authentication
The radosgw-token
utility generates the access token based on the LDAP
user name and password. It will output a base-64 encoded string which is the
access token.
# export RGW_ACCESS_KEY_ID="<username>"
# export RGW_SECRET_ACCESS_KEY="<password>"
# radosgw-token --encode
Important
The access token is a base-64 encoded JSON struct and contains the LDAP credentials as a clear text.
Alternatively, users can also generate the token manually by base-64-encoding
this JSON snippet, if they do not have the radosgw-token
tool installed.
{
"RGW_TOKEN": {
"version": 1,
"type": "ldap",
"id": "your_username",
"key": "your_clear_text_password_here"
}
}
Using the access token
Use your favorite S3 client and specify the token as the access key in your client or environment variables.
# export AWS_ACCESS_KEY_ID=<base64-encoded token generated by radosgw-token>
# export AWS_SECRET_ACCESS_KEY="" # define this with an empty string, otherwise tools might complain about missing env variables.
Important
The access token is a base-64 encoded JSON struct and contains the LDAP credentials as a clear text. DO NOT share it unless you want to share your clear text password!