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18.11. Defining Bind Rules
The bind rules in an ACI define the required bind parameters that must meet so that Directory Server applies the ACI. For example, you can set bind rules based on:
- DNs
- Group memberships or assigned roles
- Locations from which an entry must bind
- Types of authentication that must be in use during the bind
- Times or days on which the bind occurs
In an ACI, the following highlighted part is the bind rule:
(target_rule) (version 3.0; acl "ACL_name"; permission_rule bind_rules;)
(target_rule) (version 3.0; acl "ACL_name"; permission_rule bind_rules;)Syntax
The general syntax of a bind rule is:
keyword comparison_operator "expression"
keyword comparison_operator "expression"keyword: Sets the type of the bind operation. See Section 18.11.1, “Frequently Used Bind Rules”.comparison_operator: Valid values are=and!=and indicate whether or not the target is the object specified in the expression. If a keyword supports additional comparison operators, it is mentioned in the corresponding section.expression: Sets the expression and must be surrounded by quotation marks. The expression itself depends on the keyword you use.
18.11.1. Frequently Used Bind Rules
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Administrators frequently use the following bind keywords:
userdn: See Section 18.11.1.1, “Defining User-based Access”.groupdn: See Section 18.11.1.2, “Defining Group-based Access”.
Additionally, bind rules are frequently combined using Boolean operators. For details, see Section 18.11.3, “Combining Bind Rules Using Boolean Operators”.
18.11.1.1. Defining User-based Access
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The
userdn keyword enables you to grant or deny access based on one or multiple DNs and uses the following syntax:
userdn comparison_operator "ldap:///distinguished_name || ldap:///distinguished_name || ..."
userdn comparison_operator "ldap:///distinguished_name || ldap:///distinguished_name || ..."
Set the DN in the expression to:
- An LDAP filter: See Section 18.11.1.1.2, “Using the
userdnKeyword with an LDAP Filter”. - The
anyonealias: See Section 18.11.1.1.3, “Granting Anonymous Access”. - The
allalias: See Section 18.11.1.1.4, “Granting Access to Authenticated Users”. - The
selfalias: See Section 18.11.1.1.5, “Enabling Users to Access Their Own Entries”. - The
parentalias: See Section 18.11.1.1.6, “Setting Access for Child Entries of a User”.
Note
Do not specify a host name or port number within the LDAP URL. The URL always applies to the local server.
18.11.1.1.1. Using a DN with the userdn Keyword
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Set the
userdn keyword to a DN to apply the ACI only to the matching entry. To match multiple entries, use the * wildcard in the DN.
Using the
userdn keyword with a DN must match the following syntax:
userdn comparison_operator ldap:///distinguished_name
userdn comparison_operator ldap:///distinguished_nameExample 18.12. Using a DN with the userdn Keyword
To enable the
uid=admin,ou=People,dc=example,dc=com user to read the manager attribute of all other users in the ou=People,dc=example,dc=com entry:
18.11.1.1.2. Using the userdn Keyword with an LDAP Filter
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If you want to dynamically allow or deny permissions to users, use the
userdn keyword with an LDAP filter:
userdn comparison_operator "ldap:///distinguished_name??scope?(filter)"
userdn comparison_operator "ldap:///distinguished_name??scope?(filter)"Note
The LDAP filter supports the
* wildcard.
Example 18.13. Using the userdn Keyword with an LDAP Filter
To enable users who have the
department attribute set to Human Resources to update the homePostalAddress attribute of users in the ou=People,dc=example,dc=com entry:
18.11.1.1.3. Granting Anonymous Access
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In certain situations, administrators want to configure anonymous access to data in the directory. Anonymous access means that it is possible to bind to the directory by providing:
- No bind DN and password
- A valid bind DN and password
To configure anonymous access, use the
ldap:///anyone expression with the userdn keyword in a bind rule:
userdn comparison_operator "ldap:///anyone"
userdn comparison_operator "ldap:///anyone"Example 18.14. Granting Anonymous Access
To enable anyone without authentication to read and search the
sn, givenName, and telephoneNumber attributes in the ou=People,dc=example,dc=com entry:
18.11.1.1.4. Granting Access to Authenticated Users
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In certain situations, administrators want to grant permission to any user who is able to successfully bind to Directory Server, except anonymous binds. To configure this feature, use the
ldap:///all expression with the userdn keyword in a bind rule:
userdn comparison_operator "ldap:///all"
userdn comparison_operator "ldap:///all"Example 18.15. Granting Access to Authenticated Users
To enable authenticated users to add and remove themselves as a member to or from the
ou=example,ou=groups,dc=example,dc=com group:
18.11.1.1.5. Enabling Users to Access Their Own Entries
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To set ACIs which allow or deny access to users to their own entry, use the
ldap:///self expression with the userdn keyword in a bind rule:
userdn comparison_operator "ldap:///self"
userdn comparison_operator "ldap:///self"Example 18.16. Enabling Users to Access Their Own Entries
To enable users in the
ou=People,dc=example,dc=com entry to update their own userPassword attribute:
18.11.1.1.6. Setting Access for Child Entries of a User
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To specify that users are granted or denied access to an entry only if their bind DN is the parent of the targeted entry, use the
self:///parent expression with the userdn keyword in a bind rule:
userdn comparison_operator "ldap:///parent"
userdn comparison_operator "ldap:///parent"Example 18.17. Setting Access for Child Entries of a User
To enable the
cn=user,ou=People,dc=example,dc=com user to update the manager attribute of its own sub-entries, such as cn=example,cn=user,ou=People,dc=example,dc=com:
18.11.1.2. Defining Group-based Access
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Group-based ACIs enable you to manage access by adding or removing users to or from a group. To configure an ACI that is based on a group membership, use the
groupdn keyword. If the user is a member of one or multiple of the specified groups, the ACI matches.
When using the
groupdn keyword, Directory Server verifies the group membership based on the following attributes:
memberuniqueMembermemberURLmemberCertificateDescription
Bind rules with the
groupdn keyword use the following syntax:
groupdn comparison_operator "ldap:///distinguished_name || ldap:///distinguished_name || ..."
groupdn comparison_operator "ldap:///distinguished_name || ldap:///distinguished_name || ..."
Set the DN in the expression to:
- An LDAP filter. See Section 18.11.1.2.2, “Using the
groupdnKeyword with an LDAP Filter”.
If you set multiple DNs in one bind rule, Directory Server applies the ACI if the authenticated user is a member of one of these groups. To set the user as a member of multiple groups, use multiple
groupdn keywords and combine them using the Boolean and operator. For details, see Section 18.11.3, “Combining Bind Rules Using Boolean Operators”.
Note
Do not specify a host name or port number within the LDAP URL. The URL always applies to the local server.
18.11.1.2.1. Using a DN with the groupdn Keyword
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To apply an ACI to members of a group, set the
groupdn keyword to the group's DN.
The
groupdn keyword set to a DN uses the following syntax:
groupdn comparison_operator ldap:///distinguished_name
groupdn comparison_operator ldap:///distinguished_nameExample 18.18. Using a DN with the groupdn Keyword
To enable members of the
cn=example,ou=Groups,dc=example,dc=com group to search and read the manager attribute of entries in ou=People,dc=example,dc=com:
18.11.1.2.2. Using the groupdn Keyword with an LDAP Filter
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Using an LDAP filter with the
groupdn keyword, you can define that the authenticated user must be a member of at least one of the groups that the filter search returns, to match the ACI.
The
groupdn keyword with an LDAP filter uses the following syntax:
groupdn comparison_operator "ldap:///distinguished_name??scope?(filter)"
groupdn comparison_operator "ldap:///distinguished_name??scope?(filter)"Note
The LDAP filter supports the
* wildcard.
Example 18.19. Using the groupdn Keyword with an LDAP Filter
To enable members of groups in
dc=example,dc=com and subtrees, which have the manager attribute set to example, update the homePostalAddress of entries in ou=People,dc=example,dc=com:
18.11.2. Further Bind Rules
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This section describes bind rules that are less-frequently used.
18.11.2.1. Defining Access Based on Value Matching
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Use the
userattr keyword in a bind rule to specify which attribute must match between the entry used to bind to the directory and the targeted entry.
The
userattr keyword uses the following syntax:
userattr comparison_operator "attribute_name#bind_type_or_attribute_value
userattr comparison_operator "attribute_name#bind_type_or_attribute_value
For further details, see:
Important
By default, Directory Server evaluates access rights on the entry they are created. However, to prevent user objects on the same level, Directory Server does not grant
add permissions to the entry where you set the ACI, when using the userattr keyword. To configure this behavior, use the userattr keyword in conjunction with the parent keyword and grant the permission additionally on level 0.
For details about inheritance, see Section 18.11.2.1.6, “Using the
userattr Keyword with Inheritance”.
18.11.2.1.1. Using the USERDN Bind Type
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To apply an ACI when the binding user DN matches the DN stored in an attribute, use the
USERDN bind type.
The
userattr keyword with the USERDN bind type requires the following syntax:
userattr comparison_operator "attribute_name#USERDN"
userattr comparison_operator "attribute_name#USERDN"Example 18.20. Using the USERDN Bind Type
To grant a manager all permissions to the
telephoneNumber attribute of its own associates:
The previous ACI is evaluated to be true if the DN of the user who performs the operation on an entry in
ou=People,dc=example,dc=com, matches the DN stored in the manager attribute of this entry.
18.11.2.1.2. Using the GROUPDN Bind Type
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To apply an ACI when the binding user DN is a member of a group set in an attribute, use the
GROUPDN bind type.
The
userattr keyword with the GROUPDN bind type requires the following syntax:
userattr comparison_operator "attribute_name#GROUPDN"
userattr comparison_operator "attribute_name#GROUPDN"Example 18.21. Using the GROUPDN Bind Type
To grant users the permission to delete a group entry which they own under the
ou=Social Committee,ou=Groups,dc=example,dc=com entry:
The previous ACI is evaluated to be true if the DN of the user who performs the operation is a member of the group specified in the
owner attribute.
The specified group can be a dynamic group, and the DN of the group can be under any suffix in the database. However, the evaluation of this type of ACI by the server is very resource-intensive.
If you are using static groups that are under the same suffix as the targeted entry, use the following expression for better performance:
userattr comparison_operator "ldap:///distinguished_name?attribute_name#GROUPDN"
userattr comparison_operator "ldap:///distinguished_name?attribute_name#GROUPDN"18.11.2.1.3. Using the ROLEDN Bind Type
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To apply an ACI when the binding user belongs to a role specified in an attribute, use the
ROLEDN bind type.
The
userattr keyword with the ROLEDN bind type requires the following syntax:
userattr comparison_operator "attribute_name#ROLEDN"
userattr comparison_operator "attribute_name#ROLEDN"Example 18.22. Using the ROLEDN Bind Type
To enable users with the
cn=Administrators,dc=example,dc=com role to search and read the manager attribute of entries in ou=People,dc=example,dc=com:
The specified role can be under any suffix in the database. If you are also using filtered roles, the evaluation of this type of ACI uses a lot of resources on the server.
If you are using a static role definition and the role entry is under the same suffix as the targeted entry, use the following expression for better performance:
18.11.2.1.4. Using the SELFDN Bind Type
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The
SELFDN bind type enables you to grant permissions, when the bound user's DN is set in a single-value attribute of the entry.
The
userattr keyword with the SELFDN bind type requires the following syntax:
userattr comparison_operator "attribute_name#SELFDN"
userattr comparison_operator "attribute_name#SELFDN"Example 18.23. Using the SELFDN Bind Type
To enable a user to add
ipatokenuniqueid=*,cn=otp,dc=example,dc=com entries that have the bind user's DN set in the ipatokenOwner attribute:
18.11.2.1.5. Using the LDAPURL Bind Type
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To apply an ACL when the bind DN matches the filter specified in an attribute of the targeted entry, use the
LDAPURL bind type.
The
userattr keyword with the LDAPURL bind type requires the following syntax:
userattr comparison_operator "attribute_name#LDAPURL"
userattr comparison_operator "attribute_name#LDAPURL"Example 18.24. Using the LDAPURL Bind Type
To grant read and search permissions to user objects which contain the
aciurl attribute set to ldap:///ou=People,dc=example,dc=com??one?(uid=user*):
18.11.2.1.6. Using the userattr Keyword with Inheritance
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When you use the
userattr keyword to associate the entry used to bind with the target entry, the ACI applies only to the target specified and not to the entries below it. In certain situations, administrators want to extend the application of the ACI several levels below the targeted entry. This is possible by using the parent keyword and specifying the number of levels below the target that should inherit the ACI.
When using the
userattr keyword with the parent keyword, the syntax is as follows:
userattr comparison_operator "parent[inheritance_level].attribute_name#bind_type_or_attribute_value
userattr comparison_operator "parent[inheritance_level].attribute_name#bind_type_or_attribute_value- inheritance_level: Comma-separated list that indicates how many levels below the target inherit the ACI. You can include five levels (
0,1,2,3,4) below the targeted entry. Zero (0) indicates the targeted entry. - attribute_name: The attribute targeted by the
userattrorgroupattrkeyword. - bind_type_or_attribute_value: Sets the attribute value or a bind type, such as
USERDN.
For example:
userattr = "parent[0,1].manager#USERDN"
userattr = "parent[0,1].manager#USERDN"
This bind rule is evaluated to be true if the bind DN matches the manager attribute of the targeted entry. The permissions granted when the bind rule is evaluated to be true apply to the target entry and to all entries immediately below it.
Example 18.25. Using the userattr Keyword with Inheritance
To enable a user to read and search the
cn=Profiles,dc=example,dc=com entry where the user's DN is set in the owner attribute, as well as the first level of child entries which includes cn=mail,cn=Profiles,dc=example,dc=com and cn=news,cn=Profiles,dc=example,dc=com:
18.11.2.2. Defining Access from Specific IP Addresses or Ranges
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The
ip keyword in a bind rule enables you to grant or deny access from a specific IP address or a range of IP addresses.
Bind rules with the
ip keyword use the following syntax:
ip comparison_operator "IP_address_or_range"
ip comparison_operator "IP_address_or_range"Example 18.26. Using IPv4 Address Ranges in Bind Rules
To deny access from the
192.0.2.0/24 network to the dc=example,dc=com entry:
Example 18.27. Using IPv6 Address Ranges in Bind Rules
To deny access from the
2001:db8::/64 network to the dc=example,dc=com entry:
18.11.2.3. Defining Access from a Specific Host or Domain
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The
dns keyword in a bind rule enables you to grant or deny access from a specific host or domain.
Warning
If Directory Server cannot resolve a connecting IP address to its Fully Qualified Domain Name (FQDN) using DNS, the server does not apply ACIs with the
dns bind rule for this client.
If client IP addresses are not resolvable using DNS, use the
ip keyword and IP addresses instead. See Section 18.11.2.2, “Defining Access from Specific IP Addresses or Ranges”.
Bind rules with the
dns keyword use the following syntax:
dns comparison_operator "host_name_or_domain_name"
dns comparison_operator "host_name_or_domain_name"Example 18.28. Defining Access from a Specific Host
To deny access from the
client.example.com host to the dc=example,dc=com entry:
Example 18.29. Defining Access from a Specific Domain
To deny access from all hosts within the
example.com domain to the dc=example,dc=com entry:
18.11.2.4. Requiring a Certain Level of Security in Connections
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The security of a connection is determined by its Security Strength Factor (SSF), which sets the minimum key strength required to process operations. Using the
ssf keyword in a bind rule, you can set that a connection must use a certain level of security. This enables you to force operations, for example password changes, to be performed over an encrypted connection.
The value for the SSF for any operation is the higher of the values between a TLS connection and a SASL bind. This means that if a server is configured to run over TLS and a replication agreement is configured for SASL/GSSAPI, the SSF for the operation is whichever available encryption type is more secure.
Bind rules with the
ssf keyword use the following syntax:
ssf comparison_operator key_strength
ssf comparison_operator key_strength
You can use the following comparison operators:
=(equal to)!(not equal to)<(less than)>(greater than)<=(less than or equal to)>=(greater than or equal to)
If the
key_strength parameter is set to 0, no secure operation is required for the LDAP operation.
Example 18.30. Requiring a Certain Level of Security in Connections
To configure that users in the
dc=example,dc=com entry can only update their userPassword attribute when the SSF is 128 or higher:
18.11.2.5. Defining Access at a Specific Day of the Week
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The
dayofweek keyword in a bind rule enables you to grant or deny access based on the day of the week.
Note
Directory Server uses the time on the server to evaluate the ACI; not the time on the client.
Bind rules with the
dayofweek keyword use the following syntax:
dayofweek comparison_operator "comma-separated_list_of_days"
dayofweek comparison_operator "comma-separated_list_of_days"Example 18.31. Granting Access on Specific Days of the Week
To deny access for the
uid=user,ou=People,dc=example,dc=com user entry to bind to the server on Saturdays and Sundays:
18.11.2.6. Defining Access at a Specific Time of Day
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The
timeofday keyword in a bind rule enables you to grant or deny access based on the time of day.
Note
Directory Server uses the time on the server to evaluate the ACI; not the time on the client.
Bind rules with the
timeofday keyword use the following syntax:
timeofday comparison_operator "time"
timeofday comparison_operator "time"
You can use the following comparison operators:
=(equal to)!(not equal to)<(less than)>(greater than)<=(less than or equal to)>=(greater than or equal to)
Important
The
timeofday keyword requires that you specify the time in 24-hour format.
Example 18.32. Defining Access at a Specific Time of a Day
To deny access for the
uid=user,ou=People,dc=example,dc=com user entry to bind to the server between 6pm and 0am:
18.11.2.7. Defining Access Based on the Authentication Method
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The
authmethod keyword in a bind rule sets what authentication method a client must use when connecting to the server, to apply the ACI.
Bind rules with the
authmethod keyword use the following syntax:
authmethod comparison_operator "authentication_method"
authmethod comparison_operator "authentication_method"
You can set the following authentication methods:
none: Authentication is not required and represents anonymous access. This is the default.simple: The client must provide a user name and password to bind to the directory.SSL: The client must bind to the directory using a TLS certificate either in a database, smart card, or other device. For details about certificate-based authentication, see Section 9.9, “Using Certificate-based Client Authentication”.SASL: The client must bind to the directory over a Simple Authentication and Security Layer (SASL) connection. When you use this authentication method in a bind rule, additionally specify the SASL mechanism, such asEXTERNAL.
Example 18.33. Enabling Access Only for Connections Using the EXTERNAL SASL Authentication Method
To deny access to the server if the connection does not use a certificate-based authentication method or SASL:
18.11.2.8. Defining Access Based on Roles
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The
roledn keyword in a bind rule enables you to grant or deny access to users having one or multiple role sets.
Note
Red Hat recommends using groups instead of roles. For further details about roles and limitations, see Section 8.2.1, “About Roles”.
Bind rules with the
roledn keyword use the following syntax:
roledn comparison_operator "ldap:///distinguished_name || ldap:///distinguished_name || ..."
roledn comparison_operator "ldap:///distinguished_name || ldap:///distinguished_name || ..."Note
If a DN contains a comma, escape the comma with a backslash.
Example 18.34. Defining Access Based on Roles
To enable users that have the
cn=Human Resources,ou=People,dc=example,dc=com role set in the nsRole attribute to search and read the manager attribute of entries in ou=People,dc=example,dc=com:
18.11.3. Combining Bind Rules Using Boolean Operators
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When creating complex bind rules, the
AND, OR, and NOT Boolean operators enable you to combine multiple keywords.
Bind rules combined with Boolean operators have the following syntax:
bind_rule_1 boolean_operator bind_rule_2...
bind_rule_1 boolean_operator bind_rule_2...Example 18.35. Combining Bind Rules Using Boolean Operators
To configure that users which are member of both the
cn=Administrators,ou=Groups,dc=example,com and cn=Operators,ou=Groups,dc=example,com group can read, search, add, update, and delete entries in ou=People,dc=example,dc=com:
How Directory Server Evaluates Boolean Operators
Directory Server evaluates Boolean operators by using the following rules:
- All expressions from left to right.In the following example,
bind_rule_1is evaluated first:(bind_rule_1) OR (bind_rule_2)
(bind_rule_1) OR (bind_rule_2)Copy to Clipboard Copied! Toggle word wrap Toggle overflow - From innermost to outermost parenthetical expressions first.In the following example,
bind_rule_2is evaluated first andbind_rule_3second:(bind_rule_1) OR ((bind_rule_2) AND (bind_rule_3))
(bind_rule_1) OR ((bind_rule_2) AND (bind_rule_3))Copy to Clipboard Copied! Toggle word wrap Toggle overflow NOTbeforeANDorORoperators.In the following example,bind_rule_2is evaluated first:(bind_rule_1) AND NOT (bind_rule_2)
(bind_rule_1) AND NOT (bind_rule_2)Copy to Clipboard Copied! Toggle word wrap Toggle overflow TheANDandORoperators have no order of precedence.
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