keystone/doc/source/advanced-topics/federation/mapping_combinations.rst

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Mapping Combinations

Description

During the authentication process an identity provider (IdP) will present keystone with a set of user attributes about the user that is authenticating. For example, in the SAML2 flow this comes to keystone in the form of a SAML document.

The attributes are typically processed by third-party software and are presented to keystone as environment variables. The original document from the IdP is generally not available to keystone. This is how the Shibboleth and Mellon implementations work.

The mapping format described in this document maps these environment variables to a local keystone user. The mapping may also define group membership for that user and projects the user can access.

An IdP has exactly one mapping specified per protocol. Mappings themselves can be used multiple times by different combinations of IdP and protocol.

Definitions

A mapping looks as follows:

{
    "rules": [
        {
            "local": [
                {
                    <user>
                    [<group>]
                    [<project>]
                }
            ],
            "remote": [
                {
                    <match>
                    [<condition>]
                }
            ]
        }
    ]
}

• `mapping`: a JSON object containing a list of rules.
• `rules`: a property in the mapping that contains the list of rules.
• `rule`: a JSON object containing local and remote properties to define the rule. There is no explicit rule property.
• `local`: a JSON object containing information on what local attributes will be mapped. The mapping engine processes this using the context (defined below) and the result is a representation of the user from keystone's perspective.
  • `<user>`: the local user that will be mapped to the federated user.
  • `<group>`: (optional) the local groups the federated user will be placed in.
  • `<projects>`: (optional) the local projects mapped to the federated user.
• `remote`: a JSON object containing information on what remote attributes will be mapped.
  • `<match>: a JSON object that tells the mapping engine what federated attribute to make available for substitution in the local object. There can be one or more of these objects in the `remote list.
  • `<condition>: a JSON object containing conditions that allow a rule. There can be zero or more of these objects in the `remote list.
• `direct mapping`: the mapping engine keeps track of each match and makes them available to the local rule for substitution.
• `assertion`: data provided to keystone by the IdP to assert facts (name, groups, etc) about the authenticating user. This is an XML document when using the SAML2 protocol.
• `mapping context`: the data, represented as key-value pairs, that is used by the mapping engine to turn the local object into a representation of the user from keystone's perspective. The mapping context contains the environment of the keystone process and any direct mapping values calculated when processing the remote list.

How Mappings Are Processed

A mapping is selected by IdP and protocol. Then keystone takes the mapping and processes each rule sequentially stopping after the first matched rule. A rule is matched when all of its conditions are met.

First keystone evaluates each condition from the rule's remote property to see if the rule is a match. If it is a match, keystone saves the data captured by each of the matches from the rule's remote property in an ordered list. We call these matches direct mappings since they can be used in the next step.

After the rule is found using the rule's conditions and a list of direct mappings is stored, keystone begins processing the rule's local property. Each object in the local property is collapsed into a single JSON object. For example:

{
    "local": [
        {
            "user": {...}
        },
        {
            "projects": [...]
        },
    ]
}

becomes:

{
    "local": {
        "user": {...}
        "projects": [...]
    },
}

when the same property exists in the local multiple times the first occurrence wins:

{
    "local": [
        {
            "user": {#first#}
        },
        {
            "projects": [...]
        },
        {
            "user": {#second#}
        },
    ]
}

becomes:

{
    "local": {
        "user": {#first#}
        "projects": [...]
    },
}

We take this JSON object and then recursively process it in order to apply the direct mappings. This is simply looking for the pattern {#} and substituting it with values from the direct mappings list. The index of the direct mapping starts at zero.

Mapping Rules

Mapping Engine

The mapping engine can be tested before creating a federated setup. It can be tested with the keystone-manage mapping_engine command:

$ keystone-manage mapping_engine --rules <file> --input <file>

Note

Although the rules file is formatted as JSON, the input file of assertion data is formatted as individual lines of key: value pairs, see keystone-manage mapping_engine --help for details.

Mapping Conditions

Mappings support 5 different types of conditions:

empty: The rule is matched to all claims containing the remote attribute type. This condition does not need to be specified.

any_one_of: The rule is matched only if any of the specified strings appear in the remote attribute type. Condition result is boolean, not the argument that is passed as input.

not_any_of: The rule is not matched if any of the specified strings appear in the remote attribute type. Condition result is boolean, not the argument that is passed as input.

blacklist: This rule removes all groups matched from the assertion. It is not intended to be used as a way to prevent users, or groups of users, from accessing the service provider. The output from filtering through a blacklist will be all groups from the assertion that were not listed in the blacklist.

whitelist: This rule explicitly states which groups should be carried over from the assertion. The result is the groups present in the assertion and in the whitelist.

Note

empty, blacklist and whitelist are the only conditions that can be used in direct mapping ({0}, {1}, etc.)

Multiple conditions can be combined to create a single rule.

Mappings Examples

The following are all examples of mapping rule types.

empty condition

{
    "rules": [
        {
            "local": [
                {
                    "user": {
                        "name": "{0} {1}",
                        "email": "{2}"
                    },
                    "group": {
                        "name": "{3}",
                        "domain": {
                            "id": "0cd5e9"
                        }
                    }
                }
            ],
            "remote": [
                {
                    "type": "FirstName"
                },
                {
                    "type": "LastName"
                },
                {
                    "type": "Email"
                },
                {
                    "type": "OIDC_GROUPS"
                }
            ]
        }
    ]
}

Note

The numbers in braces {} are indices, they map in order. For example:

- Mapping to user with the name matching the value in remote attribute FirstName
- Mapping to user with the name matching the value in remote attribute LastName
- Mapping to user with the email matching value in remote attribute Email
- Mapping to a group(s) with the name matching the value(s) in remote attribute OIDC_GROUPS

Groups can have multiple values. Each value must be separated by a ; Example: OIDC_GROUPS=developers;testers

other conditions

In <other_condition> shown below, please supply one of the following: any_one_of, or not_any_of.

{
    "rules": [
        {
            "local": [
                {
                    "user": {
                        "name": "{0}"
                    },
                    "group": {
                        "id": "0cd5e9"
                    }
                }
            ],
            "remote": [
                {
                    "type": "UserName"
                },
                {
                    "type": "HTTP_OIDC_GROUPIDS",
                    "<other_condition>": [
                        "HTTP_OIDC_EMAIL"
                    ]
                }
            ]
        }
    ]
}

In <other_condition> shown below, please supply one of the following: blacklist, or whitelist.

{
    "rules": [
        {
            "local": [
                {
                    "user": {
                        "name": "{0}"
                    }
                },
                {
                    "groups": "{1}",
                    "domain": {
                        "id": "0cd5e9"
                    }
                }
            ],
            "remote": [
                {
                    "type": "UserName"
                },
                {
                    "type": "HTTP_OIDC_GROUPIDS",
                    "<other_condition>": [
                        "me@example.com"
                    ]
                }
            ]
        }
    ]
}

Note

If the user id and name are not specified in the mapping, the server tries to directly map REMOTE_USER environment variable. If this variable is also unavailable the server returns an HTTP 401 Unauthorized error.

Group ids and names can be provided in the local section:

{
    "local": [
        {
            "group": {
                "id":"0cd5e9"
            }
        }
    ]
}

{
    "local": [
        {
            "group": {
                "name": "developer_group",
                "domain": {
                    "id": "abc1234"
                }
            }
        }
    ]
}

{
    "local": [
        {
            "group": {
                "name": "developer_group",
                "domain": {
                    "name": "private_cloud"
                }
            }
        }
    ]
}

Users can be mapped to local users that already exist in keystone's identity backend by setting the type attribute of the user to local and providing the domain to which the local user belongs:

{
    "local": [
        {
            "user": {
                "name": "local_user",
                "type": "local",
                "domain": {
                    "name": "local_domain"
                }
            }
        }
    ]
}

The user is then treated as existing in the local identity backend, and the server will attempt to fetch user details (id, name, roles, groups) from the identity backend. The local user and domain are not generated dynamically, so if they do not exist in the local identity backend, authentication attempts will result in a 401 Unauthorized error.

If you omit the type attribute or set it to ephemeral or do not provide a domain, the user is deemed ephemeral and becomes a member of the identity provider's domain. It will not be looked up in the local keystone backend, so all of its attributes must come from the IdP and the mapping rules.

Note

Domain Federated is a service domain - it cannot be listed, displayed, added or deleted. There is no need to perform any operation on it prior to federation configuration.

Output

If a mapping is valid you will receive the following output:

{
    "group_ids": "[<group-ids>]",
    "user":
        {
            "domain":
                {
                    "id": "Federated" or "<local-domain-id>"
                },
            "type": "ephemeral" or "local",
            "name": "<local-user-name>",
            "id": "<local-user-id>"
        },
    "group_names":
        [
            {
                "domain":
                    {
                        "name": "<domain-name>"
                    },
                "name":
                    {
                        "name": "[<groups-names>]"
                    }
            }
            {
                "domain":
                    {
                        "name": "<domain-name>"
                    },
                "name":
                    {
                        "name": "[<groups-names>]"
                    }
            }
        ]
}

If the mapped user is local, mapping engine will discard further group assigning and return set of roles configured for the user.

Regular Expressions

Regular expressions can be used in a mapping by specifying the regex key, and setting it to true.

{
    "rules": [
        {
            "local": [
                {
                    "user": {
                        "name": "{0}"
                    },
                    "group": {
                        "id": "0cd5e9"
                    }
                },
            ],
            "remote": [
                {
                    "type": "UserName"
                },
                {
                    "type": "HTTP_OIDC_GROUPIDS",
                    "any_one_of": [
                        ".*@yeah.com$"
                    ]
                    "regex": true
                }
            ]
        }
    ]
}

This allows any user with a claim containing a key with any value in HTTP_OIDC_GROUPIDS to be mapped to group with id 0cd5e9.

Condition Combinations

Combinations of mappings conditions can also be done.

empty, any_one_of, and not_any_of can all be used in the same rule, but cannot be repeated within the same condition. any_one_of and not_any_of are mutually exclusive within a condition's scope. So are whitelist and blacklist.

{
    "rules": [
        {
            "local": [
                {
                    "user": {
                        "name": "{0}"
                    },
                    "group": {
                        "id": "0cd5e9"
                    }
                },
            ],
            "remote": [
                {
                    "type": "UserName"
                },
                {
                    "type": "cn=IBM_Canada_Lab",
                    "not_any_of": [
                        ".*@naww.com$"
                    ],
                    "regex": true
                },
                {
                    "type": "cn=IBM_USA_Lab",
                    "any_one_of": [
                        ".*@yeah.com$"
                    ]
                    "regex": true
                }
            ]
        }
    ]
}

As before group names and users can also be provided in the local section.

This allows any user with the following claim information to be mapped to group with id 0cd5e9.

{"UserName":"<any_name>@yeah.com"}
{"cn=IBM_USA_Lab":"<any_name>@yeah.com"}
{"cn=IBM_Canada_Lab":"<any_name>@yeah.com"}

The following claims will be mapped:

• any claim containing the key UserName.
• any claim containing key cn=IBM_Canada_Lab that doesn't have the value <any_name>@naww.com.
• any claim containing key cn=IBM_USA_Lab that has value <any_name>@yeah.com.

Multiple Rules

Multiple rules can also be utilized in a mapping.

{
    "rules": [
        {
            "local": [
                {
                    "user": {
                        "name": "{0}"
                    },
                    "group": {
                        "name": "non-contractors",
                        "domain": {
                            "id": "abc1234"
                        }
                    }
                }
            ],
            "remote": [
                {
                    "type": "UserName"
                },
                {
                    "type": "orgPersonType",
                    "not_any_of": [
                        "Contractor",
                        "SubContractor"
                    ]
                }
            ]
        },
        {
            "local": [
                {
                    "user": {
                        "name": "{0}"
                    },
                    "group": {
                        "name": "contractors",
                        "domain": {
                            "id": "abc1234"
                        }
                    }
                }
            ],
            "remote": [
                {
                    "type": "UserName"
                },
                {
                    "type": "orgPersonType",
                    "any_one_of": [
                        "Contractor",
                        "SubContractor"
                    ]
                }
            ]
        }
    ]
}

The above assigns groups membership basing on orgPersonType values:

• neither Contractor nor SubContractor will belong to the non-contractors group.
• either Contractor orSubContractorwill belong to thecontractors`` group.

Rules are additive, so permissions will only be granted for the rules that succeed. All the remote conditions of a rule must be valid.

When using multiple rules you can specify more than one effective user identification, but only the first match will be considered and the others ignored ordered from top to bottom.

Since rules are additive one can specify one user identification and this will also work. The best practice for multiple rules is to create a rule for just user and another rule for just groups. Below is rules example repeated but with global username mapping.

{
    "rules": [{
        "local": [{
            "user": {
                "id": "{0}"
            }
        }],
        "remote": [{
            "type": "UserType"
        }]
    },
    {
        "local": [{
            "group": {
                "name": "non-contractors",
                "domain": {
                    "id": "abc1234"
                }
            }
        }],
        "remote": [{
            "type": "orgPersonType",
            "not_any_of": [
                "Contractor",
                "SubContractor"
            ]
        }]
    },
    {
        "local": [{
            "group": {
                "name": "contractors",
                "domain": {
                    "id": "abc1234"
                }
            }
        }],
        "remote": [{
            "type": "orgPersonType",
            "any_one_of": [
                "Contractor",
                "SubContractor"
            ]
        }]
    }]
 }

Auto-Provisioning

The mapping engine has the ability to aid in the auto-provisioning of resources when a federated user authenticates for the first time. This can be achieved using a specific mapping syntax that the mapping engine can parse and ultimately make decisions on.

For example, consider the following mapping:

{
    "rules": [
        {
            "local": [
                {
                    "user": {
                        "name": "{0}"
                    }
                },
                {
                    "projects": [
                        {
                            "name": "Production",
                            "roles": [
                                {
                                    "name": "observer"
                                }
                            ]
                        },
                        {
                            "name": "Staging",
                            "roles": [
                                {
                                    "name": "member"
                                }
                            ]
                        },
                        {
                            "name": "Project for {0}",
                            "roles": [
                                {
                                    "name": "admin"
                                }
                            ]
                        }
                    ]
                }
            ],
            "remote": [
                {
                    "type": "UserName"
                }
            ]
        }
    ]
}

The semantics of the remote section have not changed. The difference between this mapping and the other examples is the addition of a projects section within the local rules. The projects list supplies a list of projects that the federated user will be given access to. The projects will be automatically created if they don't exist when the user authenticated and the mapping engine has applied values from the assertion and mapped them into the local rules.

In the above example, an authenticated federated user will be granted the observer role on the Production project, member role on the Staging project, and they will have admin role on the Project for jsmith.

It is important to note the following constraints apply when auto-provisioning:

• Projects are the only resource that will be created dynamically.
• Projects will be created within the domain associated with the Identity Provider.
• The projects section of the mapping must also contain a roles section.
  • Roles within the project must already exist in the deployment or domain.
• Assignments are actually created for the user which is unlike the ephemeral group memberships.

Since the creation of roles typically requires policy changes across other services in the deployment, it is expected that roles are created ahead of time. Federated authentication should also be considered idempotent if the attributes from the SAML assertion have not changed. In the example from above, if the user's name is still jsmith, then no new projects will be created as a result of authentication.

Mappings can be created that mix groups and projects within the local section. The mapping shown in the example above does not contain a groups section in the local rules. This will result in the federated user having direct role assignments on the projects in the projects list. The following example contains local rules comprised of both projects and groups, which allow for direct role assignments and group memberships.

{
    "rules": [
        {
            "local": [
                {
                    "user": {
                        "name": "{0}"
                    }
                },
                {
                    "projects": [
                        {
                            "name": "Marketing",
                            "roles": [
                                {
                                    "name": "member"
                                }
                            ]
                        },
                        {
                            "name": "Development project for {0}",
                            "roles": [
                                {
                                    "name": "admin"
                                }
                            ]
                        }
                    ]
                },
                {
                    "group": {
                        "name": "Finance",
                        "domain": {
                            "id": "6fe767"
                        }
                    }
                }
            ],
            "remote": [
                {
                    "type": "UserName"
                }
            ]
        }
    ]
}

In the above example, a federated user will receive direct role assignments on the Marketing project, as well as a dedicated project specific to the federated user's name. In addition to that, they will also be placed in the Finance group and receive all role assignments that group has on projects and domains.

keystone-to-keystone

keystone-to-keystone federation also utilizes mappings, but has some differences.

An attribute file (e.g. /etc/shibboleth/attribute-map.xml in a Shibboleth implementation) is used to add attributes to the mapping context. Attributes look as follows:

<!-- example from a K2k Shibboleth implementation -->
<Attribute name="openstack_user" id="openstack_user"/>
<Attribute name="openstack_user_domain" id="openstack_user_domain"/>

The service provider must contain a mapping as shown below. openstack_user, and openstack_user_domain match to the attribute names we have in the Identity Provider. It will map any user with the name user1 or admin in the openstack_user attribute and openstack_domain attribute default to a group with id abc1234.

{
    "rules": [
        {
            "local": [
                {
                    "group": {
                        "id": "abc1234"
                    }
                }
            ],
            "remote": [
                {
                    "type": "openstack_user",
                    "any_one_of": [
                        "user1",
                        "admin"
                    ]
                },
                {
                    "type":"openstack_user_domain",
                    "any_one_of": [
                        "Default"
                    ]
                }
            ]
        }
    ]
}

The possible attributes that can be used in a mapping are openstack_user, openstack_user_domain, openstack_roles, openstack_project, and openstack_project_domain.