Customising the phone drop down in Azure AD B2C

There is a sample B2C custom policy to onboard users for MFA and for users to authenticate using MFA.

It uses this flow:

When you run the policy, you select e.g. that you want to use phone for MFA.

And then you get a drop-down for every single country.

But what if you only have users in Australia and New Zealand?

The original list is found in the “Localisation string ID”.

Look under “countryList”:

<LocalizedString ElementType="UxElement" StringId="countryList">{"DEFAULT":"Country/Region","AF":"Afghanistan","AX":"Åland Islands","AL":"Albania","DZ":"Algeria","AS":"American Samoa",..., "GB":"United Kingdom","US":"United States","UY":"Uruguay","UZ":"Uzbekistan","VU":"Vanuatu","VA":"Vatican City","VE":"Venezuela","VN":"Vietnam","WF":"Wallis and Futuna","YE":"Yemen","ZM":"Zambia","ZW":"Zimbabwe"}</LocalizedString>

We want the countryList to look like:

<LocalizedString ElementType="UxElement" StringId="countryList">{"DEFAULT":"Country/Region","AU":"Australia","NZ":"New Zealand"}</LocalizedString>

To do this we use:

<ContentDefinitions>
   <ContentDefinition Id="api.phonefactor">
    <LocalizedResourcesReferences MergeBehavior="ReplaceAll">
     <LocalizedResourcesReference Language="en" LocalizedResourcesReferenceId="api.phonefactor.en"/>
    </LocalizedResourcesReferences>
   </ContentDefinition>
  </ContentDefinitions>
<Localization Enabled="true">
   <SupportedLanguages DefaultLanguage="en" MergeBehavior="ReplaceAll">
    <SupportedLanguage>en</SupportedLanguage>
   </SupportedLanguages>
   <LocalizedResources Id="api.phonefactor.en">
    <LocalizedStrings>
     <!-- Localize the country list -->
     <LocalizedString ElementType="UxElement" StringId="countryList">{"DEFAULT":"Country/Region","AU":"Australia","NZ":"New Zealand"}</LocalizedString>
    </LocalizedStrings>
   </LocalizedResources>
  </Localization>

And the result is:

If you just wanted NZ, you could simply add the country code (+64) to the phone number.

The InputClaim is substituted in the {0} construct.

<ClaimsTransformation Id="AddCountryCodeToPhoneNumber" TransformationMethod="FormatStringClaim">
  <InputClaims>
    <InputClaim ClaimTypeReferenceId="nationalNumber" TransformationClaimType="inputClaim" />
  </InputClaims>
  <InputParameters>
    <InputParameter Id="stringFormat" DataType="string" Value="+64{0}" />
  </InputParameters>
  <OutputClaims>
    <OutputClaim ClaimTypeReferenceId="nationalNumber" TransformationClaimType="outputClaim" />
  </OutputClaims>
</ClaimsTransformation>

In this case, you could use:

<LocalizedString ElementType="UxElement" StringId="countryList">{}</LocalizedString>

All good!