User Access, Authentication, and Accounting

This chapter contains the following sections:

User Access, Authorization, and Accounting

Application Policy Infrastructure Controller (APIC) policies manage the authentication, authorization, and accounting (AAA) functions of the Cisco Application Centric Infrastructure (ACI) fabric. The combination of user privileges, roles, and domains with access rights inheritance enables administrators to configure AAA functions at the managed object level in a granular fashion. These configurations can be implemented using the REST API, the CLI, or the GUI.


Note

There is a known limitation where you cannot have more than 32 characters for the login domain name. In addition, the combined number of characters for the login domain name and the user name cannot exceed 64 characters.

Multiple Tenant Support

A core Application Policy Infrastructure Controller (APIC) internal data access control system provides multitenant isolation and prevents information privacy from being compromised across tenants. Read/write restrictions prevent any tenant from seeing any other tenant's configuration, statistics, faults, or event data. Unless the administrator assigns permissions to do so, tenants are restricted from reading fabric configuration, policies, statistics, faults, or events.

User Access: Roles, Privileges, and Security Domains

The APIC provides access according to a user’s role through role-based access control (RBAC). An Cisco Application Centric Infrastructure (ACI) fabric user is associated with the following:

  • A predefined or custom role, which is a set of one or more privileges assigned to a user

  • A set of privileges, which determine the managed objects (MOs) to which the user has access

  • For each role, a privilege type: no access, read-only, or read-write

  • One or more security domain tags that identify the portions of the management information tree (MIT) that a user can access

Roles and Privileges

A privilege controls access to a particular function within the system. The ACI fabric manages access privileges at the managed object (MO) level. Every object holds a list of the privileges that can read from it and a list of the privileges that can write to it. All objects that correspond to a particular function will have the privilege for that function in its read or write list. Because an object might correspond to additional functions, its lists might contain multiple privileges. When a user is assigned a role that contains a privilege, the user is given read access to the associated objects whose read list specifies read access, and write access to those whose write list specifies write access.

As an example, 'fabric-equipment' is a privilege that controls access to all objects that correspond to equipment in the physical fabric. An object corresponding to equipment in the physical fabric, such as 'eqptBoard,' will have 'fabric-equipment' in its list of privileges. The 'eqptBoard' object allows read-only access for the 'fabric-equipment' privilege. When a user is assigned a role such as 'fabric-admin' that contains the privilege 'fabric-equipment,' the user will have access to those equipment objects, including read-only access to the 'eqptBoard' object.


Note

Some roles contain other roles. For example, '-admin' roles such as tenant-admin, fabric-admin, access-admin are groupings of roles with the same base name. For example, ‘access-admin’ is a grouping of 'access-connectivity', 'access-equipment', 'access-protocol', and 'access-qos.' Similarly, tenant-admin is a grouping of roles with a ‘tenant‘ base, and fabric-admin is a grouping of roles with a ‘fabric‘ base.

The 'admin' role contains all privileges.

For more details about roles and privileges see APIC Roles and Privileges Matrix.

Security Domains

A security domain is a tag associated with a certain subtree in the ACI MIT object hierarchy. For example, the default tenant “common” has a domain tag common. Similarly, the special domain tag all includes the entire MIT object tree. An administrator can assign custom domain tags to the MIT object hierarchy. For example, an administrator could assign the “solar” domain tag to the tenant named solar. Within the MIT, only certain objects can be tagged as security domains. For example, a tenant can be tagged as a security domain but objects within a tenant cannot.


Note

Security Domain password strength parameters can be configured by creating Custom Conditions or by selecting Any Three Conditions that are provided.

Creating a user and assigning a role to that user does not enable access rights. It is necessary to also assign the user to one or more security domains. By default, the ACI fabric includes two special pre-created domains:

  • All—allows access to the entire MIT

  • Infra— allows access to fabric infrastructure objects/subtrees, such as fabric access policies


Note

For read operations to the managed objects that a user's credentials do not allow, a "DN/Class Not Found" error is returned, not "DN/Class Unauthorized to read." For write operations to a managed object that a user's credentials do not allow, an HTTP 401 Unauthorized error is returned. In the GUI, actions that a user's credentials do not allow, either they are not presented, or they are grayed out.

A set of predefined managed object classes can be associated with domains. These classes should not have overlapping containment. Examples of classes that support domain association are as follows:

  • Layer 2 and Layer 3 network managed objects

  • Network profiles (such as physical, Layer 2, Layer 3, management)

  • QoS policies

When an object that can be associated with a domain is created, the user must assign domain(s) to the object within the limits of the user's access rights. Domain assignment can be modified at any time.

If a virtual machine management (VMM) domain is tagged as a security domain, the users contained in the security domain can access the correspondingly tagged VMM domain. For example, if a tenant named solar is tagged with the security domain called sun and a VMM domain is also tagged with the security domain called sun, then users in the solar tenant can access the VMM domain according to their access rights.

Accounting

Cisco Application Centric Infrastructure (ACI) fabric accounting is handled by these two managed objects that are processed by the same mechanism as faults and events:

  • The aaaSessionLR managed object tracks user account login and logout sessions on the Cisco Application Policy Infrastructure Controller (APIC) and switches, and token refresh. The Cisco ACI fabric session alert feature stores information such as the following:

    • Username

    • IP address initiating the session

    • Type (telnet, HTTPS, REST, and so on)

    • Session time and length

    • Token refresh: A user account login event generates a valid active token which is required in order for the user account to exercise its rights in the Cisco ACI fabric.


      Note
      Token expiration is independent of login; a user could log out but the token expires according to the duration of the timer value it contains.

  • The aaaModLR managed object tracks the changes users make to objects and when the changes occurred.

  • If the AAA server is not pingable, it is marked unavailable and a fault is seen.

Both the aaaSessionLR and aaaModLR event logs are stored in Cisco APIC shards. After the data exceeds the pre-set storage allocation size, it overwrites records on a first-in first-out basis.


Note
In the event of a destructive event such as a disk crash or a fire that destroys a Cisco APIC cluster node, the event logs are lost; event logs are not replicated across the cluster.

The aaaModLR and aaaSessionLR managed objects can be queried by class or by distinguished name (DN). A class query provides all the log records for the whole fabric. All aaaModLR records for the whole fabric are available from the GUI at the Fabric > Inventory > POD > History > Audit Log section, The Cisco APIC GUI History > Audit Log options enable viewing event logs for a specific object identified in the GUI.

The standard syslog, callhome, REST query, and CLI export mechanisms are fully supported for aaaModLR and aaaSessionLR managed object query data. There is no default policy to export this data.

There are no pre-configured queries in the Cisco APIC that report on aggregations of data across a set of objects or for the entire system. A fabric administrator can configure export policies that periodically export aaaModLR and aaaSessionLR query data to a syslog server. Exported data can be archived periodically and used to generate custom reports from portions of the system or across the entire set of system logs.

Routed Connectivity to External Networks as a Shared Service Billing and Statistics

The Cisco Application Policy Infrastructure Controller (APIC) can be configured to collect byte count and packet count billing statistics from a port configured for routed connectivity to external networks as a shared service. The external networks are represented as external L3Out endpoint group (l3extInstP managed object) in Cisco Application Centric Infrastructure (ACI). Any EPG in any tenant can share an external L3Out EPG for routed connectivity to external networks. Billing statistics can be collected for each EPG in any tenant that uses an external L3Out EPG as a shared service. The leaf switch where the external L3Out EPG is provisioned forwards the billing statistics to the Cisco APIC where they are aggregated. Accounting policies can be configured to export these billing statics periodically to a server.

Custom RBAC Rules

RBAC rules enable a fabric-wide administrator to provide access across security domains that would otherwise be blocked. Use RBAC rules to expose physical resources or share services that otherwise are inaccessible because they are in a different security domain. RBAC rules provide read access only to their target resources. The GUI RBAC rules page is located under Admin => AAA => Security Management. RBAC rules can be created prior to the existence of a resource. Descriptions of RBAC rules, roles, and privileges (and their dependencies) are documented in the Management Information Model reference.

Used for viewing the policies configured including troubleshooting policies.

Note that ops role cannot be used for creating new monitoring and troubleshooting policies. They need to be done using the admin privilege, just like any other configurations in the APIC.

Selectively Expose Physical Resources across Security Domains

A fabric-wide administrator uses RBAC rules to selectively expose physical resources to users that otherwise are inaccessible because they are in a different security domain.

For example, if a user in tenant Solar needs access to a virtual machine management (VMM) domain, the fabric-wide admin could create an RBAC rule to allow this. The RBAC rule is comprised of these two parts: the distinguished name (DN) that locates the object to be accessed plus the name of the security domain that contains the user who will access the object. So, in this example, when designated users in the security domain Solar are logged in, this rule gives them access to the VMM domain as well as all its child objects in the tree. To give users in multiple security domains access to the VMM domain, the fabric-wide administrator would create an RBAC rule for each security domain that contains the DN for the VMM domain plus the security domain.


Note
While an RBAC rule exposes an object to a user in a different part of the management information tree, it is not possible to use the CLI to navigate to such an object by traversing the structure of the tree. However, as long as the user knows the DN of the object included in the RBAC rule, the user can use the CLI to locate it via an MO find command.

Enable Sharing of Services across Security Domains

A fabric-wide administrator uses RBAC rules to provision trans-tenant EPG communications that enable shared services across tenants.

APIC Local Users

An administrator can choose not to use external AAA servers but rather configure users on the APIC itself. These users are called APIC-local users.

At the time a user sets their password, the APIC validates it against the following criteria:

  • Minimum password length is 8 characters.

  • Maximum password length is 64 characters.

  • Has fewer than three consecutive repeated characters.

  • Must have characters from at least three of the following characters types: lowercase, uppercase, digit, symbol.

  • Does not use easily guessed passwords.

  • Cannot be the username or the reverse of the username.

  • Cannot be any variation of cisco, isco or any permutation of these characters or variants obtained by changing the capitalization of letters therein.

Cisco ACI uses a crypt library with a SHA256 one-way hash for storing passwords. At rest hashed passwords are stored in an encrypted filesystem. The key for the encrypted filesystem is protected using the Trusted Platform Module (TPM).

The APIC also enables administrators to grant access to users configured on externally managed authentication Lightweight Directory Access Protocol (LDAP), RADIUS, TACACS+, or SAML servers. Users can belong to different authentication systems and can log in simultaneously to the APIC.

The following figure shows how the process works for configuring an admin user in the local APIC authentication database who has full access to the entire ACI fabric.

Figure 1. APIC Local User Configuration Process



Note
The security domain "all" represents the entire Managed Information Tree (MIT). This domain includes all policies in the system and all nodes managed by the APIC. Tenant domains contain all the users and managed objects of a tenant. Tenant administrators should not be granted access to the "all" domain.

The following figure shows the access that the admin user Joe Stratus has to the system.

Figure 2. Result of Configuring Admin User for "all" Domain


The user Joe Stratus with read-write "admin" privileges is assigned to the domain "all" which gives him full access to the entire system.

Externally Managed Authentication Server Users

The following figure shows how the process works for configuring an admin user in an external RADIUS server who has full access to the tenant Solar.
Figure 3. Process for Configuring Users on External Authentication Servers


The following figure shows the access the admin user Jane Cirrus has to the system.
Figure 4. Result of Configuring Admin User for Tenant Solar


In this example, the Solar tenant administrator has full access to all the objects contained in the Solar tenant as well as read-only access to the tenant Common. Tenant admin Jane Cirrus has full access to the tenant Solar, including the ability to create new users in tenant Solar. Tenant users are able to modify configuration parameters of the ACI fabric that they own and control. They also are able to read statistics and monitor faults and events for the entities (managed objects) that apply to them such as endpoints, endpoint groups (EPGs) and application profiles.

In the example above, the user Jane Cirrus was configured on an external RADIUS authentication server. To configure an AV Pair on an external authentication server, add a Cisco AV Pair to the existing user record. The Cisco AV Pair specifies the Role-Based Access Control (RBAC) roles and privileges for the user on the APIC. The RADIUS server then propagates the user privileges to the APIC controller.

In the example above, the configuration for an open radius server (/etc/raddb/users) is as follows: 

janecirrus Cleartext-Password := "<password>"
Cisco-avpair = "shell:domains = solar/admin/,common//read-all(16001)"

This example includes the following elements:

  • janecirrus is the tenant administrator

  • solar is the tenant

  • admin is the role with write privileges

  • common is the tenant-common subtree that all users should have read-only access to

  • read-all is the role with read privileges

Cisco AV Pair Format

The Cisco APIC requires that an administrator configure a Cisco AV Pair on an external authentication server and only looks for one AV pair string. To do so, an administrator adds a Cisco AV pair to the existing user record. The Cisco AV pair specifies the APIC required RBAC roles and privileges for the user.

In order for the AV pair string to work, it must be formatted as follows: 

shell:domains = 
ACI_Security_Domain_1/ACI_Write_Role_1|ACI_Write_Role_2|ACI_Write_Role_3/ACI_Read_Role_1|ACI_Read_Role_2,
ACI_Security_Domain_2/ACI_Write_Role_1|ACI_Write_Role_2|ACI_Write_Role_3/ACI_Read_Role_1|ACI_Read_Role_2,
ACI_Security_Domain_3/ACI_Write_Role_1|ACI_Write_Role_2|ACI_Write_Role_3/ACI_Read_Role_1|ACI_Read_Role_2

  • shell:domains= - Required so that ACI reads the string correctly. This must always prepend the shell string.

  • ACI_Security_Domain_1//admin - Grants admin read only access to the tenants in this security domain.

  • ACI_Security_Domain_2/admin - Grants admin write access to the tenants in this security domain.

  • ACI_Security_Domain_3/read-all - Grants read-all write access to the tenants in this security domain.


Note

/'s separate the security domain, write, read sections of the string. |’s separate multiple write or read roles within the same security domain.


Note

Starting with Cisco APIC release 2.1, if no UNIX ID is provided in AV Pair, the APIC allocates the unique UNIX user ID internally.

The APIC supports the following regexes: 

shell:domains\\s*[=:]\\s*((\\S+?/\\S*?/\\S*?)(,\\S+?/\\S*?/\\S*?){0,31})(\\(\\d+\\))$
shell:domains\\s*[=:]\\s*((\\S+?/\\S*?/\\S*?)(,\\S+?/\\S*?/\\S*?){0,31})$

Examples:

  • Example 1: A Cisco AV Pair that contains a single Login domain with only writeRoles:
    

shell:domains=ACI_Security_Domain_1/Write_Role_1|Write_Role_2/
  • Example 2: A Cisco AV Pair that contains a single Login domain with only readRoles:
    

shell:domains=Security_Domain_1//Read_Role_1|Read_Role_2

Note

The "/" character is a separator between writeRoles and readRoles per Login domain and is required even if only one type of role is to be used.

The Cisco AVpair string is case sensitive. Although a fault may not be seen, using mismatching cases for the domain name or roles could lead to unexpected privileges being given.

AV Pair GUI Configuration

The security domain is defined in the ACI GUI under Admin > AAA > Security Management > Security Domains and assigned to a tenant under Tenants > Tenant_Name > Policy.

A security domain must have either a read or write role. These roles are defined in APIC > Admin > Security Management > Roles. If a role is input into the write section it automatically grants read privileges of the same level so there is no need to have ACI_Security_Domain_1/admin/admin.

RADIUS

To configure users on RADIUS servers, the APIC administrator must configure the required attributes (shell:domains) using the cisco-av-pair attribute. The default user role is network-operator.

The SNMPv3 authentication protocol options are SHA and MD5. The privacy protocol options are AES-128 and DES. If these options are not specified in the cisco-av-pair attribute, MD5 and DES are the default authentication protocols.

For example, SNMPv3 authentication and privacy protocol attributes can be specified as follows: 

snmpv3:auth=SHA priv=AES-128

Similarly, the list of domains would be as follows: 

shell:domains="domainA domainB …"

TACACS+ Authentication

Terminal Access Controller Access Control System Plus (TACACS+) is another remote AAA protocol that is supported by Cisco devices. TACACS+ has the following advantages over RADIUS authentication:

  • Provides independent AAA facilities. For example, the Cisco Application Policy Infrastructure Controller (APIC) can authorize access without authenticating.

  • Uses TCP to send data between the AAA client and server, enabling reliable transfers with a connection-oriented protocol.

  • Encrypts the entire protocol payload between the switch and the AAA server to ensure higher data confidentiality. RADIUS encrypts passwords only.

  • Uses the av-pairs that are syntactically and configurationally different than RADIUS but the Cisco APIC supports shell:domains.

The following XML example configures the Cisco Application Centric Infrastructure (ACI) fabric to work with a TACACS+ provider at IP address 10.193.208.9: 

<aaaTacacsPlusProvider name="10.193.208.9"
           key="test123"
           authProtocol="pap"/>

Note

While the examples provided here use IPv4 addresses, IPv6 addresses could also be used.

The following guidelines and limitations apply when using TACACS+:

  • The TACACS server and TACACs ports must be reachable by ping.

  • The TACACS server with the highest priority is considered first to be the primary server.

LDAP/Active Directory Authentication

Similar to RADIUS and TACACS+, LDAP allows a network element to retrieve AAA credentials that can be used to authenticate and then authorize the user to perform certain actions. An added certificate authority configuration can be performed by an administrator to enable LDAPS (LDAP over SSL) trust and prevent man-in-the-middle attacks.

The XML example below configures the ACI fabric to work with an LDAP provider at IP address 10.30.12.128.


Note

While the examples provided here use IPv4 addresses, IPv6 addresses could also be used.

 
<aaaLdapProvider name="10.30.12.128" 
          rootdn="CN=Manager,DC=ifc,DC=com" 
          basedn="DC=ifc,DC=com" 
          SSLValidationLevel="strict" 
          attribute="CiscoAVPair" 
          enableSSL="yes" 
          filter="cn=$userid" 
          port="636" />

Note

For LDAP configurations, best practice is to use CiscoAVPair as the attribute string. If customer faces the issue using Object ID 1.3.6.1.4.1.9.22.1, an additional Object ID 1.3.6.1.4.1.9.2742.1-5 can also be used in the LDAP server.

Instead of configuring the Cisco AVPair, you have the option to create LDAP group maps in the APIC.

User IDs in the APIC Bash Shell

User IDs on the APIC for the Linux shell are generated within the APIC for local users. Users whose authentication credential is managed on external servers, the user ID for the Linux shell can be specified in the cisco-av-pair. Omitting the (16001) in the above cisco-av-pair is legal, in which case the remote user gets a default Linux user ID of 23999. Linux User IDs are used during bash sessions, allowing standard Linux permissions enforcement. Also, all managed objects created by a user are marked as created-by that user’s Linux user ID.

The following is an example of a user ID as seen in the APIC Bash shell: 

admin@ifav17-ifc1:~> touch myfile
admin@ifav17-ifc1:~> ls -l myfile
-rw-rw-r-- 1 admin admin 0 Apr 13 21:43 myfile
admin@ifav17-ifc1:~> ls -ln myfile
-rw-rw-r-- 1 15374 15374 0 Apr 13 21:43 myfile
admin@ifav17-ifc1:~> id
uid=15374(admin) gid=15374(admin) groups=15374(admin)

Login Domains

A login domain defines the authentication domain for a user. Login domains can be set to the Local, LDAP, RADIUS, or TACACS+ authentication mechanisms. When accessing the system from REST, the CLI, or the GUI, the APIC enables the user to select the correct authentication domain.

For example, in the REST scenario, the username is prefixed with a string so that the full login username looks as follows: 

apic:<domain>\<username>

If accessing the system from the GUI, the APIC offers a drop-down list of domains for the user to select. If no apic: domain is specified, the default authentication domain servers are used to look up the username.

Starting in ACI version 1.0(2x), the login domain fallback of the APIC defaults local. If the default authentication is set to a non-local method and the console authentication method is also set to a non-local method and both non-local methods do not automatically fall back to local authentication, the APIC can still be accessed via local authentication.

To access the APIC fallback local authentication, use the following strings:

  • From the GUI, use apic:fallback\\username.

  • From the REST API, use apic#fallback\\username.


Note

Do not change the fallback login domain. Doing so could result in being locked out of the system.

About SAML

SAML is an XML-based open standard data format that enables administrators to access a defined set of Cisco collaboration applications seamlessly after signing into one of those applications. SAML describes the exchange of security related information between trusted business partners. It is an authentication protocol used by service providers to authenticate a user. SAML enables exchange of security authentication information between an Identity Provider (IdP) and a service provider.

SAML SSO uses the SAML 2.0 protocol to offer cross-domain and cross-product single sign-on for Cisco collaboration solutions. SAML 2.0 enables SSO across Cisco applications and enables federation between Cisco applications and an IdP. SAML 2.0 allows Cisco administrative users to access secure web domains to exchange user authentication and authorization data, between an IdP and a Service Provider while maintaining high security levels. The feature provides secure mechanisms to use common credentials and relevant information across various applications.

The authorization for SAML SSO Admin access is based on Role-Based Access Control (RBAC) configured locally on Cisco collaboration applications.

SAML SSO establishes a Circle of Trust (CoT) by exchanging metadata and certificates as part of the provisioning process between the IdP and the Service Provider. The Service Provider trusts the IdP's user information to provide access to the various services or applications.


Note

Service providers are no longer involved in authentication. SAML 2.0 delegates authentication away from the service providers and to the IdPs.

The client authenticates against the IdP, and the IdP grants an Assertion to the client. The client presents the Assertion to the Service Provider. Since there is a CoT established, the Service Provider trusts the Assertion and grants access to the client.

Enabling SAML SSO results in several advantages:

  • It reduces password fatigue by removing the need for entering different user name and password combinations.

  • It transfers the authentication from your system that hosts the applications to a third party system. UsingSAML SSO, you can create a circle of trust between an IdP and a service provider. The service provider trusts and relies on the IdP to authenticate the users.

  • It protects and secures authentication information. It provides encryption functions to protect authentication information passed between the IdP, service provider, and user. SAML SSO can also hide authentication messages passed between the IdP and the service provider from any external user.

  • It improves productivity because you spend less time re-entering credentials for the same identity.

  • It reduces costs as fewer help desk calls are made for password reset, thereby leading to more savings.