Multi-Realm Authentication and Authorization

Introduction

Shiro can use multi-realm authentication and authorization - for example, authentication and authorization against a shiro.ini account and one or more LDAP accounts or against one or more LDAP accounts. Realms can also be grouped together and logical operators used to regulate authentication.

Scope

This article describes multi-realm authentication in detail - simple configurations showing multi-realm authentication and authorization have already been presented in the Authentication and Authorization - Configuration and LDAP Configuration articles.

A Basic Multi-Realm Example

Consider the case of a user account that is configured for both the Shiro ini and an LDAP realms. Such a simple example configuration is shown in the listing below. A publicly accessible LDAP server (here, the server from forumsys.com) is used in this example to allow the configuration to be implemented by 'cut and paste' and a minimum of modification.

Both the realms in the example have an account with the name newton. In the Shiro ini realm this account is assigned the administrator role and in the LDAP realm it is assigned the it_operator role by way of the realm group roles mapping  publicLdapRealm.groupRolesMap = scientists : it_operator (The newton account is configured as a member of the scientists group on the LDAP server.)

[users]
newton = $shiro1$SHA-512$500000$wsJJJJ7cbBpoVi0C...JJ5U5pter6Q==,administrator

[main]
publicLdapRealm = com.sos.auth.shiro.SOSLdapAuthorizingRealm
 
publicLdapRealm.userDnTemplate = uid={0},dc=example,dc=com
publicLdapRealm.searchBase = dc=example,dc=com
publicLdapRealm.contextFactory.url = ldap://ldap.forumsys.com:389
 
publicLdapRealm.groupNameAttribute = ou
publicLdapRealm.userNameAttribute = uid
 
publicLdapRealm.rolePermissionResolver = $rolePermissionResolver
publicLdapRealm.userSearchFilter = (uniqueMember=uid=%s,dc=example,dc=com)
publicLdapRealm.groupRolesMap = \
  scientists : it_operator, \
  mathematicians: all
 
rolePermissionResolver = com.sos.auth.shiro.SOSPermissionResolverAdapter
rolePermissionResolver.ini = $iniRealm
 
securityManager.realms = $publicLdapRealm, $iniRealm
cacheManager = org.apache.shiro.cache.MemoryConstrainedCacheManager
securityManager.cacheManager = $cacheManager

Realm Selection

In the example above:

• If the securityManager.realms parameter is specified ( Explicit realm ordering):
  • The authorization information provided by the user logging in will be only be checked against the realms listed in the securityManager.realms parameter. Realms configured in the [main] section but not listed in the securityManager.realms parameter will be ignored. 
  • The authorization information provided by the user logging in will be checked against each realm account in the order in which realms are specified in the securityManager.realms parameter. In the example, this would be first the publicLdapRealm and then the iniRealm.
• If the securityManager.realms parameter had not been specified ( implicit realm ordering):
  • The authorization information provided by the user logging in would have been checked against each realm account in the order in which realms were listed in the [main] section of the shiro.ini file. In the example, this would be first the iniRealm and then the publicLdapRealm.

Note that Explicit and implicit realm ordering is described in more detail in the 'Realm Authentication' section on the Shiro Authentication web site.

Alternative Authentication Behavior Strategies

Shiro allows a number of Authentication Behavior Strategies to be followed. These are configured with the authcStrategy parameter and are:

• org.apache.shiro.authc.pam.AtLeastOneSuccessfulStrategy
  
  • If one (or more) Realms authenticate successfully, the overall attempt is considered successful. If none authenticate successfully, the attempt fails.
  • Roles from all authenticated realms are merged.
• org.apache.shiro.authc.pam.FirstSuccessfulStrategy
  • Only the information returned from the first successfully authenticated Realm will be used. All further Realms will be ignored. If none authenticate successfully, the attempt fails.
  • Roles from the first authenticated realm are used.

• org.apache.shiro.authc.pam.AllSuccessfulStrategy

  • All Realms listed in the securityManager.realms parameter must authenticate successfully for the overall attempt to be considered successful. If any one does not authenticate successfully, the attempt fails.
  • Roles from all realms are merged.

By default, Shiro authentication uses the authcStrategy = org.apache.shiro.authc.pam.AtLeastOneSuccessfulStrategy . This strategy causes a login to be attempted for all the realms listed in the securityManager.realms parameter or, if this is not set, in all the realms listen in the shiro.ini configuration file. However, note the behavior described below if one of the realms configured is the iniRealm.

The authcStrategy is configured as follows:

authcStrategy = org.apache.shiro.authc.pam.AtLeastOneSuccessful
securityManager.authenticator.authenticationStrategy = $authcStrategy

Authentication and Authorization with the FirstSuccessfulStrategy configured

The FirstSuccessfulStrategy strategy is incorrectly implemented in Shiro and a login will be attempted for all the realms, even after a successful login has been noted. In addition login attempts carried out after a successful login has been noted will be logged at the [error] level. See issue JOC-437 for more information.

A new (SOS) authenticator is included in release 1.12.4 onwards to replace the default Shiro authenticator. This authenticator stops the authentication process once a successful login has taken place when the First Successful strategy has been configured.. The SOS authenticator is configured using the following lines of code:

authenticator = com.sos.auth.shiro.SOSAuthenticator
securityManager.authenticator=$authenticator

The SOS authenticator can be used with all three behavior strategies but it only causes the behavior of the First Successful strategy to be modified,

Passive Authentication and Authorization

When an LDAP realm user account is authenticated and there is an iniRealm with the same user name but this realm is not listed in the  securityManager.realms parameter, then by default, role(s) configured for the ini realm account will be merged together with those of the LDAP realm account. Note that this will occur regardless of whether or not the same password is used for both realm accounts.

The roleAssignmentFromIni = false LDAP realm parameter (default setting is true) can be used to suppress this behavior, In the example listed above this parameter would then be configured for the publicLdapRealm as:

• publicLdapRealm.roleAssignmentFromIni = false

Note that this parameter has to be defined for each realm individually.

Behavior for Accounts with Differing Passwords

The following points apply for a multi-realm environment, where one of the realms is the ini realm and when the user accounts have a common name but different passwords:

When the SOS Authenticator is used with the First Successful strategy:

• If the authorization occurs through the ini realm then the user account will only be assigned the roles specified for the ini realm. The LDAP realm(s) will be ignored.
• If the authorization occurs through an LDAP realm then, regardless of whether or not the same password is used in each realm:
  • The user account will be assigned the role(s) specified for the account in the (first) authorizing realm.
  • The user account will also be assigned the role(s) specified for the account in the ini realm.
    • This behavior ensures that a login is possible in the event of problems with the LDAP realm(s).
  • The order in which the realms are specified in the securityManager.realms parameter is not significant here.
  • The roleAssignmentFromIni=false setting (default true) can be used to modify the behavior of the First Successful strategy so that roles from the ini realm are not assigned. See the Suppressing assignment of the ini Realm section below.

Suppressing assignment of the ini Realm

FEATURE AVAILABILITY STARTING FROM RELEASE 1.12.4

When the First Successful strategy is used when an ini realm and one or more LDAP realms have accounts with common user names and separate passwords, the roles for the ini realm will be assigned by default when the login is carried out for one of the LDAP realms. This behavior can be suppressed by setting the roleAssignmentFromIni parameter to false for the  LDAP realms in the environment. This is shown in the code example below: 

[users]
newton = $shiro1$SHA-512$500000$wsJJJJ7cbBpoVi0C...JJ5U5pter6Q==,administrator

[main]
publicLdapRealm = com.sos.auth.shiro.SOSLdapAuthorizingRealm
 
publicLdapRealm.userDnTemplate = uid={0},dc=example,dc=com
publicLdapRealm.searchBase = dc=example,dc=com
publicLdapRealm.contextFactory.url = ldap://ldap.forumsys.com:389
 
publicLdapRealm.groupNameAttribute = ou
publicLdapRealm.userNameAttribute = uid
 
publicLdapRealm.rolePermissionResolver = $rolePermissionResolver
publicLdapRealm.userSearchFilter = (uniqueMember=uid=%s,dc=example,dc=com)
publicLdapRealm.groupRolesMap = \
  scientists : it_operator, \
  mathematicians: all
publicLdapRealm.roleAssignmentFromIni = false
 
rolePermissionResolver = com.sos.auth.shiro.SOSPermissionResolverAdapter
rolePermissionResolver.ini = $iniRealm
 
authcStrategy = org.apache.shiro.authc.pam.SOSFirstSuccessfulGroupStrategy
securityManager.authenticator.authenticationStrategy = $authcStrategy
securityManager.realms = $publicLdapRealm, $iniRealm
cacheManager = org.apache.shiro.cache.MemoryConstrainedCacheManager
securityManager.cacheManager = $cacheManager

With the above configuration:

• When the user name newton is used together with the password for the ini realm then the account will be assigned the administrator role.
• When the user name newton is used together with the password for the LDAP realm then the account will be assigned the it_operator role.

Realm Group/Role Mappings

FEATURE AVAILABILITY STARTING FROM RELEASE 1.12.4

Logical selection of realm group strategies can also be implemented. These strategies determine, for example, that an account will only be authenticated for one realm when it can also be authenticated for all the realms in that group.

Configuration

This feature is activated by inserting the following line of code in the [main] section of the Shiro ini file:

• securityManager.authenticator.authenticationStrategy = $authcStrategy

In addition a logical strategy has to be implemented - the following four strategies are available:

• SOSFirstSuccessfulGroupStrategy
• SOSAllSuccessfulGroupStrategy
• SOSAllSuccessfulFirstGroupStrategy
• SOSAtLeastOneSuccessfulGroupStrategy

The strategy to be followed is specified by adding, for example, the following to the [main] section of the Shiro ini file:

• authcStrategy = com.sos.auth.shiro.SOSFirstSuccessfulGroupStrategy

Finally all group realms are to be named following the syntax:

• group#name

Example

The following example uses two Groups, each with two realms. An account with a common User Name and Password is configured for all Realms

A#ldap1
roles = a1

A#ldap2
roles = a2

B#ldap1
roles = b1

B#ldap2
roles = b2

Here is an example main section for this szenario

[main]
A#Ldap1 = com.sos.auth.shiro.SOSLdapAuthorizingRealm
 
A#Ldap1.userDnTemplate = uid={0},dc=example,dc=com
A#Ldap1.searchBase = dc=example,dc=com
A#Ldap1.contextFactory.url = ldap://ldap.forumsys.com:389
 
A#Ldap1.groupNameAttribute = ou
A#Ldap1.userNameAttribute = uid
 
A#Ldap1.rolePermissionResolver = $rolePermissionResolver
A#Ldap1.userSearchFilter = (uniqueMember=uid=%s,dc=example,dc=com)
A#Ldap1.groupRolesMap = \
  scientists : it_operator, \
  mathematicians: all
A#Ldap1.roleAssignmentFromIni = false
 
A#Ldap2 = com.sos.auth.shiro.SOSLdapAuthorizingRealm
...


B#Ldap1 = com.sos.auth.shiro.SOSLdapAuthorizingRealm
...


B#Ldap2 = com.sos.auth.shiro.SOSLdapAuthorizingRealm
...

rolePermissionResolver = com.sos.auth.shiro.SOSPermissionResolverAdapter
rolePermissionResolver.ini = $iniRealm
 
authcStrategy = org.apache.shiro.authc.pam.SOSFirstSuccessfulGroupStrategy
securityManager.authenticator.authenticationStrategy = $authcStrategy
 
securityManager.realms = $A#Ldap1,$A#Ldap2,$B#Ldap1,$B#Ldap2
cacheManager = org.apache.shiro.cache.MemoryConstrainedCacheManager
securityManager.cacheManager = $cacheManager

Example Behavior with Different Strategies

SOSFirstSuccessfulGroupStrategy

authcStrategy = org.apache.shiro.authc.pam.SOSFirstSuccessfulGroupStrategy
securityManager.authenticator.authenticationStrategy = $authcStrategy

All realms with the same group will be checked group-wise.

In every group there must be one realm that can be authenticated.

If none of the realms in at least one group authenticate then authentication will fail for all groups.

The roles from the first realm per group will be merged to the roles the user has.

Example:

• If A#ldap1, A#ldap2 and B#ldap2 can authenticate than the user will have the roles a1 and b2.
• If A#ldap2 and B#ldap1 can authenticate than authentication will fail.

SOSAllSuccessfulGroupStrategy

authcStrategy = org.apache.shiro.authc.pam.SOSAllSuccessfulGroupStrategy
securityManager.authenticator.authenticationStrategy = $authcStrategy

All realms with the same group will be checked group-wise.
In at least one group all realms must be authenticated.
The roles from realms in groups where all realms can be authenticated will be merged to the roles the user has.

Examples:

• If A#ldap1, A#ldap2 and B#ldap1, B#ldap2 can authenticate than the user will have the roles a1,a2,b1,b2.
• If A#ldap1, A#ldap2 and B#ldap1 can authenticate than the user will have the roles a1,a2.
• If A#ldap2 and B#ldap1 can authenticate than authentication will fail.

SOSAllSuccessfulFirstGroupStrategy

authcStrategy = org.apache.shiro.authc.pam.SOSAllSuccessfulFirstGroupStrategy
securityManager.authenticator.authenticationStrategy = $authcStrategy

All realms with the same group will be checked group-wise.
In at least one group all realms must be authenticated.
The roles from realms in the first group where all realms can be authenticated will be merged with other roles the user may have.

Example:

• If A#ldap1, and B#ldap1, B#ldap2 can authenticate than the user will have the roles b1,b2
• If A#ldap1, A#ldap2 and B#ldap2 can authenticate than the user will have the roles a1,a2
• If A#ldap1 and B#ldap2 can authenticate than authentication will fail.

SOSAtLeastOneSuccessfulGroupStrategy

authcStrategy = org.apache.shiro.authc.pam.SOSAtLeastOneSuccessfulGroupStrategy
securityManager.authenticator.authenticationStrategy = $authcStrategy

All realms with the same group will be checked group-wise.
At least one realm must be authenticate in every group.
The roles from realms that have authenticated will be merged with other roles the user may have.

Example:

• If A#ldap1, B#ldap1, B#ldap2 can authenticate than the user will have the roles a1,b1,b2
• If B#ldap1 and B#ldap2 can authenticate than authentication will fail.