Predicates and PredicateValidations

Άρθρο
01/11/2024

Note

In Azure Active Directory B2C, custom policies are designed primarily to address complex scenarios. For most scenarios, we recommend that you use built-in user flows. If you've not done so, learn about custom policy starter pack in Get started with custom policies in Active Directory B2C.

The Predicates and PredicateValidations elements enable you to perform a validation process to ensure that only properly formed data is entered into your Azure Active Directory B2C (Azure AD B2C) tenant.

The following diagram shows the relationship between the elements:

Diagram showing Predicates and Predicate Validations relationship

Predicates

The Predicate element defines a basic validation to check the value of a claim type and returns true or false. The validation is done by using a specified Method element and a set of Parameter elements relevant to the method. For example, a predicate can check whether the length of a string claim value is within the range of minimum and maximum parameters specified, or whether a string claim value contains a character set. The UserHelpText element provides an error message for users if the check fails. The value of UserHelpText element can be localized using language customization.

The Predicates element must appear directly following the ClaimsSchema element within the BuildingBlocks element.

The Predicates element contains the following element:

Element	Occurrences	Description
Predicate	1:n	A list of predicates.

The Predicate element contains the following attributes:

Attribute	Required	Description
Id	Yes	An identifier that's used for the predicate. Other elements can use this identifier in the policy.
Method	Yes	The method type to use for validation. Possible values: IsLengthRange, MatchesRegex, IncludesCharacters, or IsDateRange.
HelpText	No	An error message for users if the check fails. This string can be localized using the language customization

The Predicate element contains the following elements:

Element	Occurrences	Description
UserHelpText	0:1	(Deprecated) An error message for users if the check fails.
Parameters	1:1	The parameters for the method type of the string validation.

The Parameters element contains the following elements:

Element	Occurrences	Description
Parameter	1:n	The parameters for the method type of the string validation.

The Parameter element contains the following attributes:

Element	Occurrences	Description
Id	1:1	The identifier of the parameter.

Predicate methods

IsLengthRange

The IsLengthRange method checks whether the length of a string claim value is within the range of minimum and maximum parameters specified. Check out the Live demo of this predicate method. The predicate element supports the following parameters:

Parameter	Required	Description
Maximum	Yes	The maximum number of characters that can be entered.
Minimum	Yes	The minimum number of characters that must be entered.

The following example shows an IsLengthRange method with the parameters Minimum and Maximum that specify the length range of the string:

<Predicate Id="IsLengthBetween8And64" Method="IsLengthRange" HelpText="The password must be between 8 and 64 characters.">
  <Parameters>
    <Parameter Id="Minimum">8</Parameter>
    <Parameter Id="Maximum">64</Parameter>
  </Parameters>
</Predicate>

MatchesRegex

The MatchesRegex method checks whether a string claim value matches a regular expression. Check out the Live demo of this predicate method. The predicate element supports the following parameters:

Parameter	Required	Description
RegularExpression	Yes	The regular expression pattern to match.

The following example shows a MatchesRegex method with the parameter RegularExpression that specifies a regular expression:

<Predicate Id="PIN" Method="MatchesRegex" HelpText="The password must be numbers only.">
  <Parameters>
    <Parameter Id="RegularExpression">^[0-9]+$</Parameter>
  </Parameters>
</Predicate>

IncludesCharacters

The IncludesCharacters method checks whether a string claim value contains a character set. Check out the Live demo of this predicate method. The predicate element supports the following parameters:

Parameter	Required	Description
CharacterSet	Yes	The set of characters that can be entered. For example, lowercase characters `a-z`, uppercase characters `A-Z`, digits `0-9`, or a list of symbols, such as `@#$%^&*\-_+=[]{}\|\\:',?/~"();!`.

The following example shows a IncludesCharacters method with the parameter CharacterSet that specifies the set of characters:

<Predicate Id="Lowercase" Method="IncludesCharacters" HelpText="a lowercase letter">
  <Parameters>
    <Parameter Id="CharacterSet">a-z</Parameter>
  </Parameters>
</Predicate>

IsDateRange

The IsDateRange method checks whether a date claim value is between a range of minimum and maximum parameters specified. Check out the Live demo of this predicate method. The predicate element supports the following parameters:

Parameter	Required	Description
Maximum	Yes	The largest possible date that can be entered. The format of the date follows `yyyy-mm-dd` convention, or `Today`.
Minimum	Yes	The smallest possible date that can be entered. The format of the date follows `yyyy-mm-dd` convention, or `Today`.

The following example shows a IsDateRange method with the parameters Minimum and Maximum that specify the date range with a format of yyyy-mm-dd and Today.

<Predicate Id="DateRange" Method="IsDateRange" HelpText="The date must be between 1970-01-01 and today.">
  <Parameters>
    <Parameter Id="Minimum">1970-01-01</Parameter>
    <Parameter Id="Maximum">Today</Parameter>
  </Parameters>
</Predicate>

PredicateValidations

While the predicates define the validation to check against a claim type, the PredicateValidations group a set of predicates to form a user input validation that can be applied to a claim type. Each PredicateValidation element contains a set of PredicateGroup elements that contain a set of PredicateReference elements that points to a Predicate. To pass the validation, the value of the claim should pass all of the tests of any predicate under all of the PredicateGroup with their set of PredicateReference elements.

The PredicateValidations element must appear directly following the Predicates element within the BuildingBlocks element.

<PredicateValidations>
  <PredicateValidation Id="">
    <PredicateGroups>
      <PredicateGroup Id="">
        <UserHelpText></UserHelpText>
        <PredicateReferences MatchAtLeast="">
          <PredicateReference Id="" />
          ...
        </PredicateReferences>
      </PredicateGroup>
      ...
    </PredicateGroups>
  </PredicateValidation>
...
</PredicateValidations>

The PredicateValidations element contains the following element:

Element	Occurrences	Description
PredicateValidation	1:n	A list of predicate validation.

The PredicateValidation element contains the following attribute:

Attribute	Required	Description
Id	Yes	An identifier that's used for the predicate validation. The ClaimType element can use this identifier in the policy.

The PredicateValidation element contains the following element:

Element	Occurrences	Description
PredicateGroups	1:n	A list of predicate groups.

The PredicateGroups element contains the following element:

Element	Occurrences	Description
PredicateGroup	1:n	A list of predicates.

The PredicateGroup element contains the following attribute:

Attribute	Required	Description
Id	Yes	An identifier that's used for the predicate group.

The PredicateGroup element contains the following elements:

Element	Occurrences	Description
UserHelpText	0:1	A description of the predicate that can be helpful for users to know what value they should type.
PredicateReferences	1:n	A list of predicate references.

The PredicateReferences element contains the following attributes:

Attribute	Required	Description
MatchAtLeast	No	Specifies that the value must match at least that many predicate definitions for the input to be accepted. If not specified, the value must match all predicate definitions.

The PredicateReferences element contains the following elements:

Element	Occurrences	Description
PredicateReference	1:n	A reference to a predicate.

The PredicateReference element contains the following attributes:

Attribute	Required	Description
Id	Yes	An identifier that's used for the predicate validation.

Configure password complexity

With Predicates and PredicateValidationsInput you can control the complexity requirements for passwords provided by a user when creating an account. By default, Azure AD B2C uses strong passwords. Azure AD B2C also supports configuration options to control the complexity of passwords that customers can use. You can define password complexity by using these predicate elements:

IsLengthBetween8And64 using the IsLengthRange method, validates that the password must be between 8 and 64 characters.
Lowercase using the IncludesCharacters method, validates that the password contains a lowercase letter.
Uppercase using the IncludesCharacters method, validates that the password contains an uppercase letter.
Number using the IncludesCharacters method, validates that the password contains a digit.
Symbol using the IncludesCharacters method, validates that the password contains one of several symbol characters.
PIN using the MatchesRegex method, validates that the password contains numbers only.
AllowedAADCharacters using the MatchesRegex method, validates that the password only invalid character was provided.
DisallowedWhitespace using the MatchesRegex method, validates that the password doesn't begin or end with a whitespace character.

<Predicates>
  <Predicate Id="IsLengthBetween8And64" Method="IsLengthRange" HelpText="The password must be between 8 and 64 characters.">
    <Parameters>
      <Parameter Id="Minimum">8</Parameter>
      <Parameter Id="Maximum">64</Parameter>
    </Parameters>
  </Predicate>

  <Predicate Id="Lowercase" Method="IncludesCharacters" HelpText="a lowercase letter">
    <Parameters>
      <Parameter Id="CharacterSet">a-z</Parameter>
    </Parameters>
  </Predicate>

  <Predicate Id="Uppercase" Method="IncludesCharacters" HelpText="an uppercase letter">
    <Parameters>
      <Parameter Id="CharacterSet">A-Z</Parameter>
    </Parameters>
  </Predicate>

  <Predicate Id="Number" Method="IncludesCharacters" HelpText="a digit">
    <Parameters>
      <Parameter Id="CharacterSet">0-9</Parameter>
    </Parameters>
  </Predicate>

  <Predicate Id="Symbol" Method="IncludesCharacters" HelpText="a symbol">
    <Parameters>
      <Parameter Id="CharacterSet">@#$%^&amp;*\-_+=[]{}|\\:',.?/`~"();!</Parameter>
    </Parameters>
  </Predicate>

  <Predicate Id="PIN" Method="MatchesRegex" HelpText="The password must be numbers only.">
    <Parameters>
      <Parameter Id="RegularExpression">^[0-9]+$</Parameter>
    </Parameters>
  </Predicate>

  <Predicate Id="AllowedAADCharacters" Method="MatchesRegex" HelpText="An invalid character was provided.">
    <Parameters>
      <Parameter Id="RegularExpression">(^([0-9A-Za-z\d@#$%^&amp;*\-_+=[\]{}|\\:',?/`~"();! ]|(\.(?!@)))+$)|(^$)</Parameter>
    </Parameters>
  </Predicate>

  <Predicate Id="DisallowedWhitespace" Method="MatchesRegex" HelpText="The password must not begin or end with a whitespace character.">
    <Parameters>
      <Parameter Id="RegularExpression">(^\S.*\S$)|(^\S+$)|(^$)</Parameter>
    </Parameters>
  </Predicate>

After you define the basic validations, you can combine them together and create a set of password policies that you can use in your policy:

SimplePassword validates the DisallowedWhitespace, AllowedAADCharacters, and IsLengthBetween8And64
StrongPassword validates the DisallowedWhitespace, AllowedAADCharacters, IsLengthBetween8And64. The last group CharacterClasses runs an additional set of predicates with MatchAtLeast set to 3. The user password must be between 8 and 16 characters, and three of the following characters: Lowercase, Uppercase, Number, or Symbol.
CustomPassword validates only DisallowedWhitespace, AllowedAADCharacters. So, user can provide any password with any length, as long as the characters are valid.

<PredicateValidations>
  <PredicateValidation Id="SimplePassword">
    <PredicateGroups>
      <PredicateGroup Id="DisallowedWhitespaceGroup">
        <PredicateReferences>
          <PredicateReference Id="DisallowedWhitespace" />
        </PredicateReferences>
      </PredicateGroup>
      <PredicateGroup Id="AllowedAADCharactersGroup">
        <PredicateReferences>
          <PredicateReference Id="AllowedAADCharacters" />
        </PredicateReferences>
      </PredicateGroup>
      <PredicateGroup Id="LengthGroup">
        <PredicateReferences>
          <PredicateReference Id="IsLengthBetween8And64" />
        </PredicateReferences>
      </PredicateGroup>
    </PredicateGroups>
  </PredicateValidation>

  <PredicateValidation Id="StrongPassword">
    <PredicateGroups>
      <PredicateGroup Id="DisallowedWhitespaceGroup">
        <PredicateReferences>
          <PredicateReference Id="DisallowedWhitespace" />
       </PredicateReferences>
      </PredicateGroup>
      <PredicateGroup Id="AllowedAADCharactersGroup">
        <PredicateReferences>
          <PredicateReference Id="AllowedAADCharacters" />
        </PredicateReferences>
      </PredicateGroup>
      <PredicateGroup Id="LengthGroup">
        <PredicateReferences>
          <PredicateReference Id="IsLengthBetween8And64" />
        </PredicateReferences>
      </PredicateGroup>
      <PredicateGroup Id="CharacterClasses">
        <UserHelpText>The password must have at least 3 of the following:</UserHelpText>
        <PredicateReferences MatchAtLeast="3">
          <PredicateReference Id="Lowercase" />
          <PredicateReference Id="Uppercase" />
          <PredicateReference Id="Number" />
          <PredicateReference Id="Symbol" />
        </PredicateReferences>
      </PredicateGroup>
    </PredicateGroups>
  </PredicateValidation>

  <PredicateValidation Id="CustomPassword">
    <PredicateGroups>
      <PredicateGroup Id="DisallowedWhitespaceGroup">
        <PredicateReferences>
          <PredicateReference Id="DisallowedWhitespace" />
        </PredicateReferences>
      </PredicateGroup>
      <PredicateGroup Id="AllowedAADCharactersGroup">
        <PredicateReferences>
          <PredicateReference Id="AllowedAADCharacters" />
        </PredicateReferences>
      </PredicateGroup>
    </PredicateGroups>
  </PredicateValidation>
</PredicateValidations>

In your claim type, add the PredicateValidationReference element and specify the identifier as one of the predicate validations, such as SimplePassword, StrongPassword, or CustomPassword.

<ClaimType Id="password">
  <DisplayName>Password</DisplayName>
  <DataType>string</DataType>
  <AdminHelpText>Enter password</AdminHelpText>
  <UserHelpText>Enter password</UserHelpText>
  <UserInputType>Password</UserInputType>
  <PredicateValidationReference Id="StrongPassword" />
</ClaimType>

The following shows how the elements are organized when Azure AD B2C displays the error message:

Diagram of Predicate and PredicateGroup password complexity example

Configure a date range

With the Predicates and PredicateValidations elements you can control the minimum and maximum date values of the UserInputType by using a DateTimeDropdown. To do this, create a Predicate with the IsDateRange method and provide the minimum and maximum parameters.

<Predicates>
  <Predicate Id="DateRange" Method="IsDateRange" HelpText="The date must be between 01-01-1980 and today.">
    <Parameters>
      <Parameter Id="Minimum">1980-01-01</Parameter>
      <Parameter Id="Maximum">Today</Parameter>
    </Parameters>
  </Predicate>
</Predicates>

Add a PredicateValidation with a reference to the DateRange predicate.

<PredicateValidations>
  <PredicateValidation Id="CustomDateRange">
    <PredicateGroups>
      <PredicateGroup Id="DateRangeGroup">
        <PredicateReferences>
          <PredicateReference Id="DateRange" />
        </PredicateReferences>
      </PredicateGroup>
    </PredicateGroups>
  </PredicateValidation>
</PredicateValidations>

In your claim type, add PredicateValidationReference element and specify the identifier as CustomDateRange.

<ClaimType Id="dateOfBirth">
  <DisplayName>Date of Birth</DisplayName>
  <DataType>date</DataType>
  <AdminHelpText>The user's date of birth.</AdminHelpText>
  <UserHelpText>Your date of birth.</UserHelpText>
  <UserInputType>DateTimeDropdown</UserInputType>
  <PredicateValidationReference Id="CustomDateRange" />
</ClaimType>

Next steps

Learn how to Configure password complexity using custom policies in Azure Active Directory B2C using predicate validations.

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