Active Directory (AD) reference

COMMERCIAL FEATURE: Access active directory (AD) authentication for single sign-on (SSO) in the packaged Sensu Go distribution. For more information, read Get started with commercial features.

Sensu requires username and password authentication to access the web UI, API, and sensuctl command line tool.

In addition to the built-in basic authentication, Sensu offers commercial support for using Microsoft Active Directory (AD) for single sign-on (SSO) authentication. The AD authentication provider is based on the LDAP authentication provider.

To use AD authentication for Azure, follow Microsoft’s tutorial to set up secure LDAP in your Azure account and create the host and certificates you need.

For general information about configuring authentication providers, read Configure single sign-on (SSO) authentication.

AD configuration examples

Example AD configuration: Minimum required attributes

---
type: ad
api_version: authentication/v2
metadata:
  name: activedirectory
spec:
  servers:
  - group_search:
      base_dn: dc=acme,dc=org
    host: 127.0.0.1
    user_search:
      base_dn: dc=acme,dc=org
{
  "type": "ad",
  "api_version": "authentication/v2",
  "spec": {
    "servers": [
      {
        "host": "127.0.0.1",
        "group_search": {
          "base_dn": "dc=acme,dc=org"
        },
        "user_search": {
          "base_dn": "dc=acme,dc=org"
        }
      }
    ]
  },
  "metadata": {
    "name": "activedirectory"
  }
}

Example AD configuration: All attributes

---
type: ad
api_version: authentication/v2
metadata:
  name: activedirectory
spec:
  allowed_groups: []
  groups_prefix: ad
  servers:
  - binding:
      password: YOUR_PASSWORD
      user_dn: cn=binder,cn=users,dc=acme,dc=org
    client_cert_file: /path/to/ssl/cert.pem
    client_key_file: /path/to/ssl/key.pem
    default_upn_domain: example.org
    include_nested_groups: true
    group_search:
      attribute: member
      base_dn: dc=acme,dc=org
      name_attribute: cn
      object_class: group
    host: 127.0.0.1
    insecure: false
    port: 636
    security: tls
    trusted_ca_file: /path/to/trusted-certificate-authorities.pem
    user_search:
      attribute: sAMAccountName
      base_dn: dc=acme,dc=org
      name_attribute: displayName
      object_class: person
  username_prefix: ad
{
  "type": "ad",
  "api_version": "authentication/v2",
  "spec": {
    "servers": [
      {
        "host": "127.0.0.1",
        "port": 636,
        "insecure": false,
        "security": "tls",
        "trusted_ca_file": "/path/to/trusted-certificate-authorities.pem",
        "client_cert_file": "/path/to/ssl/cert.pem",
        "client_key_file": "/path/to/ssl/key.pem",
        "default_upn_domain": "example.org",
        "include_nested_groups": true,
        "binding": {
          "user_dn": "cn=binder,cn=users,dc=acme,dc=org",
          "password": "YOUR_PASSWORD"
        },
        "group_search": {
          "base_dn": "dc=acme,dc=org",
          "attribute": "member",
          "name_attribute": "cn",
          "object_class": "group"
        },
        "user_search": {
          "base_dn": "dc=acme,dc=org",
          "attribute": "sAMAccountName",
          "name_attribute": "displayName",
          "object_class": "person"
        }
      }
    ],
    "allowed_groups": [],
    "groups_prefix": "ad",
    "username_prefix": "ad"
  },
  "metadata": {
    "name": "activedirectory"
  }
}

NOTE: If you specify allowed groups, the group names must exactly match the names the authentication provider returns to the Sensu backend.

Example AD configuration: Use memberOf attribute instead of group_search

AD automatically returns a memberOf attribute in users’ accounts. The memberOf attribute contains the user’s group membership, which effectively removes the requirement to look up the user’s groups.

To use the memberOf attribute in your AD implementation, remove the group_search object from your AD config:

---
type: ad
api_version: authentication/v2
metadata:
  name: activedirectory
spec:
  servers:
    host: 127.0.0.1
    user_search:
      base_dn: dc=acme,dc=org
{
  "type": "ad",
  "api_version": "authentication/v2",
  "spec": {
    "servers": [
      {
        "host": "127.0.0.1",
        "user_search": {
          "base_dn": "dc=acme,dc=org"
        }
      }
    ]
  },
  "metadata": {
    "name": "activedirectory"
  }
}

After you configure AD to use the memberOf attribute, the debug log level will include the following log entries:

{"component":"authentication/v2","level":"debug","msg":"using the \"memberOf\" attribute to determine the group membership of user \"user1\"","time":"2020-06-25T14:10:58-04:00"}
{"component":"authentication/v2","level":"debug","msg":"found 1 LDAP group(s): [\"sensu\"]","time":"2020-06-25T14:10:58-04:00"}

AD specification

AD top-level attributes

type
description Top-level attribute that specifies the sensuctl create resource type. For AD definitions, the type should always be ad.
required true
type String
example 
type: ad
{
  "type": "ad"
}
api_version
description Top-level attribute that specifies the Sensu API group and version. For AD definitions, the api_version should always be authentication/v2.
required true
type String
example 
api_version: authentication/v2
{
  "api_version": "authentication/v2"
}
metadata
description Top-level map that contains the AD definition name. Review the metadata attributes for details.
required true
type Map of key-value pairs
example 
metadata:
  name: activedirectory
{
  "metadata": {
    "name": "activedirectory"
  }
}
spec
description Top-level map that includes the AD spec attributes.
required true
type Map of key-value pairs
example 
spec:
  servers:
  - host: 127.0.0.1
    port: 636
    insecure: false
    security: tls
    trusted_ca_file: "/path/to/trusted-certificate-authorities.pem"
    client_cert_file: "/path/to/ssl/cert.pem"
    client_key_file: "/path/to/ssl/key.pem"
    default_upn_domain: example.org
    include_nested_groups: true
    binding:
      user_dn: cn=binder,cn=users,dc=acme,dc=org
      password: YOUR_PASSWORD
    group_search:
      base_dn: dc=acme,dc=org
      attribute: member
      name_attribute: cn
      object_class: group
    user_search:
      base_dn: dc=acme,dc=org
      attribute: sAMAccountName
      name_attribute: displayName
      object_class: person
  allowed_groups: []
  groups_prefix: ad
  username_prefix: ad
{
  "spec": {
    "servers": [
      {
        "host": "127.0.0.1",
        "port": 636,
        "insecure": false,
        "security": "tls",
        "trusted_ca_file": "/path/to/trusted-certificate-authorities.pem",
        "client_cert_file": "/path/to/ssl/cert.pem",
        "client_key_file": "/path/to/ssl/key.pem",
        "default_upn_domain": "example.org",
        "include_nested_groups": true,
        "binding": {
          "user_dn": "cn=binder,cn=users,dc=acme,dc=org",
          "password": "YOUR_PASSWORD"
        },
        "group_search": {
          "base_dn": "dc=acme,dc=org",
          "attribute": "member",
          "name_attribute": "cn",
          "object_class": "group"
        },
        "user_search": {
          "base_dn": "dc=acme,dc=org",
          "attribute": "sAMAccountName",
          "name_attribute": "displayName",
          "object_class": "person"
        }
      }
    ],
    "allowed_groups": [],
    "groups_prefix": "ad",
    "username_prefix": "ad"
  }
}

AD metadata attributes

name
description A unique string used to identify the AD configuration. Names cannot contain special characters or spaces (validated with Go regex \A[\w\.\-]+\z).
required true
type String
example 
name: activedirectory
{
  "name": "activedirectory"
}

AD spec attributes

servers
description The list of AD servers to use. During the authentication process, Sensu attempts to authenticate against each AD server in sequence until authentication is successful or there are no more servers to try.
required true
type Array
example 
servers:
- host: 127.0.0.1
  port: 636
  insecure: false
  security: tls
  trusted_ca_file: "/path/to/trusted-certificate-authorities.pem"
  client_cert_file: "/path/to/ssl/cert.pem"
  client_key_file: "/path/to/ssl/key.pem"
  default_upn_domain: example.org
  include_nested_groups: true
  binding:
    user_dn: cn=binder,cn=users,dc=acme,dc=org
    password: YOUR_PASSWORD
  group_search:
    base_dn: dc=acme,dc=org
    attribute: member
    name_attribute: cn
    object_class: group
  user_search:
    base_dn: dc=acme,dc=org
    attribute: sAMAccountName
    name_attribute: displayName
    object_class: person
{
  "servers": [
    {
      "host": "127.0.0.1",
      "port": 636,
      "insecure": false,
      "security": "tls",
      "trusted_ca_file": "/path/to/trusted-certificate-authorities.pem",
      "client_cert_file": "/path/to/ssl/cert.pem",
      "client_key_file": "/path/to/ssl/key.pem",
      "default_upn_domain": "example.org",
      "include_nested_groups": true,
      "binding": {
        "user_dn": "cn=binder,cn=users,dc=acme,dc=org",
        "password": "YOUR_PASSWORD"
      },
      "group_search": {
        "base_dn": "dc=acme,dc=org",
        "attribute": "member",
        "name_attribute": "cn",
        "object_class": "group"
      },
      "user_search": {
        "base_dn": "dc=acme,dc=org",
        "attribute": "sAMAccountName",
        "name_attribute": "displayName",
        "object_class": "person"
      }
    }
  ]
}

allowed_groups
description An array of allowed AD group strings to include in the tokenized identity claim. Use to specify which groups to encode in the authentication provider’s JSON Web Token (JWT) when the authenticated AD user is a member of many groups and the tokenized identity claim would be too large for correct web client operation.

NOTE: Allowed group names are case-sensitive and must exactly match the group names the authentication provider returns to the Sensu backend.
required false
type Array
example 
allowed_groups:
- Sensu_Viewers
- Sensu_Operators
{
  "allowed_groups": [
    "Sensu_Viewers",
    "Sensu_Operators"
  ]
}

groups_prefix
description The prefix added to all AD groups. Sensu appends the groups_prefix with a colon. For example, for the groups_prefix ad and the group dev, the resulting group name in Sensu is ad:dev. Use the groups_prefix when integrating AD groups with Sensu RBAC role bindings and cluster role bindings.
required false
type String
example 
groups_prefix: ad
{
  "groups_prefix": "ad"
}

username_prefix
description The prefix added to all AD usernames. Sensu appends the username_prefix with a colon. For example, for the username_prefix ad and the user alice, the resulting username in Sensu is ad:alice. Use the username_prefix when integrating AD users with Sensu RBAC role bindings and cluster role bindings. Users do not need to provide the username_prefix when logging in to Sensu.
required false
type String
example 
username_prefix: ad
{
  "username_prefix": "ad"
}

AD server attributes

host
description AD server IP address or fully qualified domain name (FQDN).
required true
type String
example 
host: 127.0.0.1
{
  "host": "127.0.0.1"
}
port
description AD server port.
required true
type Integer
default 389 for insecure connections; 636 for TLS connections
example 
port: 636
{
  "port": 636
}

insecure
description Skips SSL certificate verification when set to true.

WARNING: Do not use an insecure connection in production environments.
required false
type Boolean
default false
example 
insecure: false
{
  "insecure": false
}

security
description Determines the encryption type to be used for the connection to the AD server: insecure (unencrypted connection; not recommended for production), tls (secure encrypted connection), or starttls (unencrypted connection upgrades to a secure connection).
type String
default tls
example 
security: tls
{
  "security": "tls"
}
trusted_ca_file
description Path to an alternative CA bundle file in PEM format to be used instead of the system’s default bundle. This CA bundle is used to verify the server’s certificate.
required false
type String
example 
trusted_ca_file: /path/to/trusted-certificate-authorities.pem
{
  "trusted_ca_file": "/path/to/trusted-certificate-authorities.pem"
}
client_cert_file
description Path to the certificate that should be sent to the server if requested.
required false
type String
example 
client_cert_file: /path/to/ssl/cert.pem
{
  "client_cert_file": "/path/to/ssl/cert.pem"
}
client_key_file
description Path to the key file associated with the client_cert_file.
required false
type String
example 
client_key_file: /path/to/ssl/key.pem
{
  "client_key_file": "/path/to/ssl/key.pem"
}

binding
description The AD account that performs user and group lookups. If your server supports anonymous binding, you can omit the user_dn or password attributes to query the directory without credentials. To use anonymous binding with AD, the ANONYMOUS LOGON object requires read permissions for users and groups. Review the binding attributes for details.
required false
type Map
example 
binding:
  user_dn: cn=binder,cn=users,dc=acme,dc=org
  password: YOUR_PASSWORD
{
  "binding": {
    "user_dn": "cn=binder,cn=users,dc=acme,dc=org",
    "password": "YOUR_PASSWORD"
  }
}
group_search
description Search configuration for groups. Review the group search attributes for more information. Remove the group_search object from your configuration to use the memberOf attribute instead.
required false
type Map
example 
group_search:
  base_dn: dc=acme,dc=org
  attribute: member
  name_attribute: cn
  object_class: group
{
  "group_search": {
    "base_dn": "dc=acme,dc=org",
    "attribute": "member",
    "name_attribute": "cn",
    "object_class": "group"
  }
}

user_search
description Search configuration for users. Review the user search attributes for more information.
required true
type Map
example 
user_search:
  base_dn: dc=acme,dc=org
  attribute: sAMAccountName
  name_attribute: displayName
  object_class: person
{
  "user_search": {
    "base_dn": "dc=acme,dc=org",
    "attribute": "sAMAccountName",
    "name_attribute": "displayName",
    "object_class": "person"
  }
}
default_upn_domain
description Enables UPN authentication when set. The default UPN suffix that will be appended to the username when a domain is not specified during login (for example, user becomes user@defaultdomain.xyz).

WARNING: When using UPN authentication, users must re-authenticate to apply any changes to group membership on the AD server since their last authentication. For example, if you remove a user from a group with administrator permissions for the current session (such as a terminated employee), Sensu will not apply the change until the user logs out and tries to start a new session. Likewise, under UPN, users cannot be forced to log out of Sensu. To apply group membership updates without re-authentication, specify a binding account or enable anonymous binding.
required false
type String
example 
default_upn_domain: example.org
{
  "default_upn_domain": "example.org"
}
include_nested_groups
description If true, the group search includes any nested groups a user is a member of. If false, the group search includes only the top-level groups a user is a member of.
required false
type Boolean
example 
include_nested_groups: true
{
  "include_nested_groups": true
}

AD binding attributes

user_dn
description The AD account that performs user and group lookups. We recommend using a read-only account. Use the distinguished name (DN) format, such as cn=binder,cn=users,dc=domain,dc=tld. If your server supports anonymous binding, you can omit this attribute to query the directory without credentials.
required false
type String
example 
user_dn: cn=binder,cn=users,dc=acme,dc=org
{
  "user_dn": "cn=binder,cn=users,dc=acme,dc=org"
}
password
description Password for the user_dn account. If your server supports anonymous binding, you can omit this attribute to query the directory without credentials.
required false
type String
example 
password: YOUR_PASSWORD
{
  "password": "YOUR_PASSWORD"
}

AD group search attributes

base_dn
description Tells Sensu which part of the directory tree to search. For example, dc=acme,dc=org searches within the acme.org directory.
required true
type String
example 
base_dn: dc=acme,dc=org
{
  "base_dn": "dc=acme,dc=org"
}
attribute
description Used for comparing result entries. Combined with other filters as
"(<Attribute>=<value>)".
required false
type String
default member
example 
attribute: member
{
  "attribute": "member"
}

name_attribute
description Represents the attribute to use as the entry name.
required false
type String
default cn
example 
name_attribute: cn
{
  "name_attribute": "cn"
}
object_class
description Identifies the class of objects returned in the search result. Combined with other filters as "(objectClass=<ObjectClass>)".
required false
type String
default group
example 
object_class: group
{
  "object_class": "group"
}

AD user search attributes

base_dn
description Tells Sensu which part of the directory tree to search. For example, dc=acme,dc=org searches within the acme.org directory.
required true
type String
example 
base_dn: dc=acme,dc=org
{
  "base_dn": "dc=acme,dc=org"
}
attribute
description Used for comparing result entries. Combined with other filters as
"(<Attribute>=<value>)".
required false
type String
default sAMAccountName
example 
attribute: sAMAccountName
{
  "attribute": "sAMAccountName"
}
name_attribute
description Represents the attribute to use as the entry name.
required false
type String
default displayName
example 
name_attribute: displayName
{
  "name_attribute": "displayName"
}
object_class
description Identifies the class of objects returned in the search result. Combined with other filters as "(objectClass=<ObjectClass>)".
required false
type String
default person
example 
object_class: person
{
  "object_class": "person"
}

AD troubleshooting

To troubleshoot any issue with AD authentication, start by increasing the log verbosity of sensu-backend to the debug log level. Most authentication and authorization errors are only displayed on the debug log level to avoid flooding the log files.

NOTE: If you can’t locate any log entries referencing AD authentication, run sensuctl auth list to make sure that you successfully installed the AD provider.

Authentication

This section lists common authentication error messages and describes possible solutions for each of them.

failed to connect: AD Result Code 200 "Network Error"

The AD provider couldn’t establish a TCP connection to the AD server. Verify the host and port attributes. If you are not using AD over TLS/SSL, make sure to set the value of the security attribute to insecure for plaintext communication.

certificate signed by unknown authority

If you are using a self-signed certificate, make sure to set the insecure attribute to true. This will bypass verification of the certificate’s signing authority.

failed to bind: ...

The first step for authenticating a user with the AD provider is to bind to the AD server using the service account specified in the binding object. Make sure the user_dn attribute specifies a valid DN and that its password is correct.

user <username> was not found

The user search failed. No user account could be found with the given username. Check the user_search object and make sure that:

  • The specified base_dn contains the requested user entry DN
  • The specified attribute contains the username as its value in the user entry
  • The object_class attribute corresponds to the user entry object class

ad search for user <username> returned x results, expected only 1

The user search returned more than one user entry, so the provider could not determine which of these entries to use. Change the user_search object so the provided username can be used to uniquely identify a user entry. Here are two methods to try:

  • Adjust the attribute so its value (which corresponds to the username) is unique among the user entries
  • Adjust the base_dn so it only includes one of the user entries

ad entry <DN> missing required attribute <name_attribute>

The user entry returned (identified by <DN>) doesn’t include the attribute specified by name_attribute object, so the AD provider could not determine which attribute to use as the username in the user entry. Adjust the name_attribute so it specifies a human-readable name for the user.

ad group entry <DN> missing <name_attribute> and cn attributes

The group search returned a group entry (identified by <DN>) that doesn’t have the name_attribute object or a cn attribute, so the AD provider could not determine which attribute to use as the group name in the group entry. Adjust the name_attribute so it specifies a human-readable name for the group.

Authorization

Once authenticated, each user needs to be granted permissions via either a ClusterRoleBinding or a RoleBinding.

The way AD users and AD groups can be referred as subjects of a cluster role or role binding depends on the groups_prefix and username_prefix configuration attributes values of the AD provider. For example, for the groups_prefix ad and the group dev, the resulting group name in Sensu is ad:dev.

Permissions are not granted via the AD group(s)

During authentication, the AD provider will print all groups found in AD (for example, found 1 group(s): [dev]) in the logs. Keep in mind that this group name does not contain the groups_prefix at this point.

The Sensu backend logs each attempt made to authorize an RBAC request. This is useful for determining why a specific binding didn’t grant the request. For example:

[...] the user is not a subject of the ClusterRoleBinding cluster-admin [...]
[...] could not authorize the request with the ClusterRoleBinding system:user [...]
[...] could not authorize the request with any ClusterRoleBindings [...]