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Define a CAPTCHA technical profile in an Azure Active Directory B2C custom policy

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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.

A Completely Automated Public Turing Tests to Tell Computer and Human Apart (CAPTCHA) technical profiles enables Azure Active Directory B2C (Azure AD B2C) to prevent automated attacks. Azure AD B2C's CAPTCHA technical profile supports both audio and visual CAPTCHA challenges types.

Protocol

The Name attribute of the Protocol element needs to be set to Proprietary. The handler attribute must contain the fully qualified name of the protocol handler assembly that is used by Azure AD B2C, for CAPTCHA: Web.TPEngine.Providers.CaptchaProvider, Web.TPEngine, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null

Note

This feature is in public preview

The following example shows a self-asserted technical profile for email sign-up:

<TechnicalProfile Id="HIP-GetChallenge">
  <DisplayName>Email signup</DisplayName>
  <Protocol Name="Proprietary" Handler="Web.TPEngine.Providers.CaptchaProvider, Web.TPEngine, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />

CAPTCHA technical profile operations

CAPTCHA technical profile operations have two operations:

  • Get challenge operation generates the CAPTCHA code string, then displays it on the user interface by using a CAPTCHA display control. The display includes an input textbox. This operation directs the user to input the characters they see or hear into the input textbox. The user can switch between visual and audio challenge types as needed.

  • Verify code operation verifies the characters input by the user.

Get challenge

The first operation generates the CAPTCHA code string, then displays it on the user interface.

Input claims

The InputClaims element contains a list of claims to send to Azure AD B2C's CAPTCHA service.

ClaimReferenceId Required Description
challengeType No The CAPTCHA challenge type, Audio or Visual (default).
azureregion Yes The service region that serves the CAPTCHA challenge request.

Display claims

The DisplayClaims element contains a list of claims to be presented on the screen for the user to see. For example, the user is presented with the CAPTCHA challenge code to read.

ClaimReferenceId Required Description
challengeString Yes The CAPTCHA challenge code.

Output claims

The OutputClaims element contains a list of claims returned by the CAPTCHA technical profile.

ClaimReferenceId Required Description
challengeId Yes A unique identifier for CAPTCHA challenge code.
challengeString Yes The CAPTCHA challenge code.
azureregion Yes The service region that serves the CAPTCHA challenge request.

Metadata

Attribute Required Description
Operation Yes Value must be GetChallenge.
Brand Yes Value must be HIP.

Example: Generate CAPTCHA code

The following example shows a CAPTCHA technical profile that you use to generate a code:

<TechnicalProfile Id="HIP-GetChallenge">
  <DisplayName>GetChallenge</DisplayName>
  <Protocol Name="Proprietary" Handler="Web.TPEngine.Providers.CaptchaProvider, Web.TPEngine, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />

  <Metadata>
    <Item Key="Operation">GetChallenge</Item>
    <Item Key="Brand">HIP</Item>
  </Metadata>

  <InputClaims>
    <InputClaim ClaimTypeReferenceId="challengeType" />
  </InputClaims>

  <DisplayClaims>
    <DisplayClaim ClaimTypeReferenceId="challengeString" />
  </DisplayClaims>

  <OutputClaims>
    <OutputClaim ClaimTypeReferenceId="challengeId" />
    <OutputClaim ClaimTypeReferenceId="challengeString" PartnerClaimType="ChallengeString" />
    <OutputClaim ClaimTypeReferenceId="azureregion" />
  </OutputClaims>

</TechnicalProfile>

Verify challenge

The second operation verifies the CAPTCHA challenge.

Input claims

The InputClaims element contains a list of claims to send to Azure AD B2C's CAPTCHA service.

ClaimReferenceId Required Description
challengeType No The CAPTCHA challenge type, Audio or Visual (default).
challengeId Yes A unique identifier for CAPTCHA used for session verification. Populated from the GetChallenge call.
captchaEntered Yes The challenge code that the user inputs into the challenge textbox on the user interface.
azureregion Yes The service region that serves the CAPTCHA challenge request. Populated from the GetChallenge call.

Display claims

The DisplayClaims element contains a list of claims to be presented on the screen for collecting an input from the user.

ClaimReferenceId Required Description
captchaEntered Yes The CAPTCHA challenge code entered by the user.

Output claims

The OutputClaims element contains a list of claims returned by the captcha technical profile.

ClaimReferenceId Required Description
challengeId Yes A unique identifier for CAPTCHA used for session verification.
isCaptchaSolved Yes A flag indicating whether the CAPTCHA challenge is successfully solved.
reason Yes Used to communicate to the user whether the attempt to solve the challenge is successful or not.

Metadata

Attribute Required Description
Operation Yes Value must be VerifyChallenge.
Brand Yes Value must be HIP.

Example: Verify CAPTCHA code

The following example shows a CAPTCHA technical profile that you use to verify a CAPTCHA code:

  <TechnicalProfile Id="HIP-VerifyChallenge">
    <DisplayName>Verify Code</DisplayName>
    <Protocol Name="Proprietary" Handler="Web.TPEngine.Providers.CaptchaProvider, Web.TPEngine, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
    <Metadata>
      <Item Key="Brand">HIP</Item>
      <Item Key="Operation">VerifyChallenge</Item>
    </Metadata>

    <InputClaims>
      <InputClaim ClaimTypeReferenceId="challengeType" DefaultValue="Visual" />
      <InputClaim ClaimTypeReferenceId="challengeId" />
      <InputClaim ClaimTypeReferenceId="captchaEntered" PartnerClaimType="inputSolution" Required="true" />
      <InputClaim ClaimTypeReferenceId="azureregion" />
    </InputClaims>

    <DisplayClaims>
      <DisplayClaim ClaimTypeReferenceId="captchaEntered" />
    </DisplayClaims>

    <OutputClaims>
      <OutputClaim ClaimTypeReferenceId="challengeId" />
      <OutputClaim ClaimTypeReferenceId="isCaptchaSolved" PartnerClaimType="solved" />
      <OutputClaim ClaimTypeReferenceId="reason" PartnerClaimType="reason" />
    </OutputClaims>

  </TechnicalProfile>

Next steps