GSMA Open Gateway Call Forwarding Signal API

---
openapi: 3.0.3
############################################################################
#                                     API info                             #
############################################################################
info:
  title: Call Forwarding Signal
  description: |
    # Overview
    The Call Forwarding Signal (CFS) API provides the API Consumer with
    information about the status of the Call Forwading Service on a specific
    phone number. The main scope of the CFS API is "anti Fraud" to avoid
    fraudsters to use the Call Forwarding Service to carry on a scam. Other use
    cases are anyway supported by the CFS API that also provides additional
    endpoints to detect the general Call Forwarding Service settings.
    # Introduction
    The Call Forwarding Service is provided by the Network to a phone
    number. This service redirects the incoming call to that phone number
    to an alternative destination such as another phone number or a voice mail
    system. There are two main types of call forwarding settings:
    unconditional and conditional.
    The CFS API can be invoked to detect if the unconditional
    call forwarding service is active. The CSF API can also be invoked to
    get the general status of the Call Forwarding Service (inactive,
    conditional, unconditional). If conditional call forwarding is active,
    the differente type of settings are returned ('conditional_busy',
    'conditional_unavailable', 'conditional_no_reply').\
    \
    **Example use cases:**\
    \
    [**Bank Frauds**](https://github.com/camaraproject/CallForwardingSignal\
    /discussions/3#discussioncomment-8694420)\
    \
    [**Alert Interception**](https://github.com/camaraproject/CallForwarding\
    Signal/discussions/3#discussioncomment-8701847)\
    \
    [**Call Forwading Verification**](https://github.com/camaraproject/\
    CallForwarding\Signal/discussions/3#discussioncomment-8915595)
    # Quick Start
    The CFS API is a REST API based on the CreateCallForwardingSignal resource.
    This resource can be filled during the API invokation, by the API Consumer,
    with the phone number on which the Call Forwarding Service status must be
    verified. Anyway the phone number is also detected, by the API Producer,
    from the access token.\
    \
    Before starting to use the Call Forwarding API, the developer needs to know
    about the below specified details:\
    \
    **phoneNumber**
    This is the end user phone number. The CFS API verifies if a call forwarding
    service is active on this phone number. Note: the value of this optional
    parameter must match the value of the phone number retrieved from the access
    token.\
    \
    **CreateCallForwardingSignal**
    This is the resource the API Consumer uses to define the phone number to
    be verified about the status of the Network Call Forwarding service.\
    \
    **UnconditionalCallForwardingSignal**
    This is the resource the API Consumer gets back, containing the information
    about the Unconditional Call Forwarding Service status for the given phone
    number (PhoneNumber)\
    \
    **CallForwardingSignal**
    This is the resource the API Consumer gets back, containing the information
    about the general status of the Network Call Forwarding service for the
    specified phone number.\
    \
    The CFS API provides two endpoints fulfilling the following intents:
    - **unconditional-call-forwardings**: Is the unconditional call fwd service
    active on a specific phone number?
    - **call-forwardings**: Which is the status of the call forwarding for a
    specific phone number?
    # Authorization and authentication
    The "Camara Security and Interoperability Profile" provides details on how
    a client requests an access token. Please refer to Identify and Consent
    Management (https://github.com/camaraproject/IdentityAndConsentManagement/)
    for the released version of the Profile.\
    \
    Which specific authorization flows are to be used will be determined during
    onboarding process, happening between the API Client and the Telco Operator
    exposing the API, taking into account the declared purpose for accessing the
    API, while also being subject to the prevailing legal framework dictated by
    local legislation.\
    \
    It is important to remark that in cases where personal user data is
    processed by the API, and users can exercise their rights through mechanisms
    such as opt-in and/or opt-out, the use of 3-legged access tokens becomes
    mandatory. This measure ensures that the API remains in strict compliance
    with user privacy preferences and regulatory obligations, upholding the
    principles of transparency and user-centric data control.
    # Identifying the phone number from the access token
    This specification defines the "phoneNumber" field as optional in API
    requests because using a 3-legged access token the phone number can be
    uniquely identified by the token.
    ## Handling of phone number information:
    ### Optional phone number object for 3-legged tokens:
    When using a 3-legged access token, the phone number associated with the
    access token must be considered as the phone number for the API request.
    This means that the "phoneNumber" paramenter is not required in the request,
    and if it is included it must identify the same phone number.
    ### Validation mechanism:
    - The server will extract the phone number identification from the access
    token, if available.
    - If the API request additionally includes a "phoneNumber" parameter when
    using a 3-legged access token, the API will validate that the phone number
    identifier provided matches the one associated with the access token.
    - If there is a mismatch, the API will respond with a
    403 `INVALID_TOKEN_CONTEXT` error, indicating that the device information
    in the request does not match the token.
    ### Error handling for unidentifiable devices:
    - If the "phoneNumber" parameter is not included in the request and the
    phone number information cannot be derived from the 3-legged access token,
    the server will return a 422 `UNIDENTIFIABLE_DEVICE` error.
    # API Documentation
    ## Details
    The CFS API is invoked by an API Consumer after the Consent Management
    flow.\
    The API Consumer can request the API Producer for the status of the
    Unconditional Call Forwarding service using the
    unconditional-call-forwardings POST method. A boolean, with the information
    about the activation status of the call forwarding service, will be
    provided back via the UnconditionalCallForwardingSignal resource.\
    The API Consumer can also request the API Producer for the generic status of
    the Call Forwarding service using the call-forwardings POST method. An array
    of strings with the information of the type of active call forwarding
    services will be provided back via the CallForwardingSignal resource.\
    CFS API have to check the Call Forwarding
    Service status can be optionally defined with resource
    (CreateCallForwardingSignal) containing the phone number (PhoneNumber)
    to be checked.
    # FAQ's
    (FAQs will be added in a later version of the documentation)

  version: 0.2.0
  license:
    name: Apache 2.0
    url: https://www.apache.org/licenses/LICENSE-2.0.html
  x-camara-commonalities: 0.4.0
externalDocs:
  description: Product documentation at CAMARA
  url: https://github.com/camaraproject/CallForwardingSignal
############################################################################
#                                     Servers                              #
############################################################################
servers:
  - url: "{apiRoot}/call-forwarding-signal/v0.2"
    variables:
      apiRoot:
        default: http://localhost:9091
        description: API root, defined by the service provider, e.g. `api.example.com` or `api.example.com/somepath`
############################################################################
#                                     Tags                                #
############################################################################
tags:
  - name: Unconditional Call Forwarding information retrieval
    description: Provides information on Unconditional Call Forwarding
     settings for the provided phone number (PhoneNumber)
  - name: Call Forwarding information retrieval
    description: Provides information on Call Forwarding settings for the
     provided phone number (PhoneNumber).
############################################################################
#                                     Paths                                #
############################################################################
paths:
  /unconditional-call-forwardings:
    post:
      tags:
        - Unconditional Call Forwarding information retrieval
      security:
        - openId:
            - 'call-forwarding-signal:unconditional-call-forwardings:read'
      summary: Retrieve the information about the status of the
       unconditional call forwarding service on a phone number (PhoneNumber)
      description: This endpoint provides information about the status
       of the unconditional call forwarding, beeing active or not.
      operationId: retrieveUnconditionalCallForwarding
      parameters:
        - $ref: '#/components/parameters/x-correlator'
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateCallForwardingSignal'
        required: true
      responses:
        '200':
          description: OK.
          headers:
            x-correlator:
              $ref: '#/components/headers/x-correlator'
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/UnconditionalCallForwardingSignal'
        "400":
          $ref: "#/components/responses/Generic400"
        '404':
          $ref: '#/components/responses/Generic404'
        '500':
          $ref: '#/components/responses/Generic500'
        '504':
          $ref: '#/components/responses/Generic504'
        "401":
          $ref: "#/components/responses/Generic401"
        "403":
          $ref: "#/components/responses/Generic403"
        "409":
          $ref: "#/components/responses/Generic409"
        "415":
          $ref: "#/components/responses/Generic415"
        "422":
          $ref: "#/components/responses/Generic422"
        "429":
          $ref: "#/components/responses/Generic429"
        "503":
          $ref: "#/components/responses/Generic503"
  /call-forwardings:
    post:
      tags:
        - Call Forwarding information retrieval
      security:
        - openId:
            - 'call-forwarding-signal:call-forwardings:read'
      summary: Retrieve the information about the type of call forwarding
       service active on a phone number (PhoneNumber)
      description: This endpoint provides information about wich type of
       call forwarding service is active. More than one service can be
       active, e.g. conditional and unconditional. This endpoint exceeds
       the main scope of the CFS API, for this reason an error code 501
       can be returned.
      operationId: retrieveCallForwarding
      parameters:
        - $ref: '#/components/parameters/x-correlator'
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateCallForwardingSignal'
        required: true
      responses:
        '200':
          description: OK.
          headers:
            x-correlator:
              $ref: '#/components/headers/x-correlator'
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/CallForwardingSignal'
        "400":
          $ref: "#/components/responses/Generic400"
        '404':
          $ref: '#/components/responses/Generic404'
        '500':
          $ref: '#/components/responses/Generic500'
        '504':
          $ref: '#/components/responses/Generic504'
        "401":
          $ref: "#/components/responses/Generic401"
        "403":
          $ref: "#/components/responses/Generic403"
        "409":
          $ref: "#/components/responses/Generic409"
        "415":
          $ref: "#/components/responses/Generic415"
        "422":
          $ref: "#/components/responses/Generic422"
        "429":
          $ref: "#/components/responses/Generic429"
        "501":
          $ref: "#/components/responses/Generic501"
        "503":
          $ref: "#/components/responses/Generic503"
############################################################################
#                                 Components                               #
############################################################################
components:
  securitySchemes:
    openId:
      description: to support Consent Management
      type: openIdConnect
      openIdConnectUrl: https://example.com/.well-known/openid-configuration
  parameters:
    x-correlator:
      name: x-correlator
      in: header
      description: Correlation id for the different services
      schema:
        type: string
  headers:
    x-correlator:
      description: Correlation id for the different services
      schema:
        type: string
  ############################################################################
  #                                 Resources                                #
  ############################################################################
  schemas:
    UnconditionalCallForwardingSignal:
      description: resource containing the information about the Unconditional
       Call Forwarding Service for the given phone number (PhoneNumber)
      type: object
      properties:
        active:
          type: boolean
          description: Indicates if the unconditional call forwarding service
           is active.
    CallForwardingSignal:
      description: resource containing the list of the Call
       Forwarding Services active for the given phone number (PhoneNumber). The
       possible states are, 'inactive' (no call forwarding service activated),
       'unconditional' (call forwarded independently from the device status),
       'conditional_busy' (call forwarded if the device is on an active call),
       'conditional_unavailable' (call forwarded if the device is not available
       on the network), 'conditional_no_reply' (call forwarded if the device
       doesn't answer the incoming call).
      type: array
      items:
        type: string
        enum:
          - 'inactive'
          - 'unconditional'
          - 'conditional_busy'
          - 'conditional_unavailable'
          - 'conditional_no_reply'
      example:
        - 'unconditional'
        - 'conditional_busy'
        - 'conditional_no_reply'
      minItems: 1
    ############################################################################
    #                                 Request                                  #
    ############################################################################
    CreateCallForwardingSignal:
      description: resource containing the phone number (PhoneNumber) regarding
       which the Call Forwarding Service must be checked
      type: object
      properties:
        phoneNumber:
          $ref: "#/components/schemas/PhoneNumber"
    ############################################################################
    #                                 Types                                    #
    ############################################################################
    PhoneNumber:
      description: A public identifier addressing a telephone subscription.
       In mobile networks it corresponds to the MSISDN (Mobile Station
       International Subscriber Directory Number). In order to be globally
       unique it has to be formatted in international format, according to E.164
       standard, prefixed with '+'.
      type: string
      pattern: '^\+[1-9][0-9]{4,14}$'
      example: "+123456789"
    ############################################################################
    #                                 Responces                                #
    ############################################################################
    ErrorInfo:
      description: error information
      type: object
      required:
        - status
        - code
        - message
      properties:
        status:
          type: integer
          description: HTTP status code returned along with this error response
        code:
          type: string
          description: Code given to this error
        message:
          type: string
          description: Detailed error description
  responses:
    Generic400:
      description: Problem with the client request
      headers:
        x-correlator:
          $ref: '#/components/headers/x-correlator'
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorInfo'
          example:
            status: 400
            code: INVALID_ARGUMENT
            message: Client specified an invalid argument, request body or query
             param
    Generic401:
      description: Authentication problem with the client request
      headers:
        x-correlator:
          $ref: '#/components/headers/x-correlator'
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorInfo'
          example:
            status: 401
            code: UNAUTHENTICATED
            message: Request not authenticated due to missing, invalid, or
             expired credentials
    Generic403:
      description: Client does not have sufficient permission
      headers:
        x-correlator:
          $ref: '#/components/headers/x-correlator'
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorInfo'
          examples:
            PermissionDenied:
              value:
                status: 403
                code: PERMISSION_DENIED
                message: Client does not have sufficient permissions to perform
                 this action
            InvalidTokenContext:
              value:
                status: 403
                code: INVALID_TOKEN_CONTEXT
                message: PhoneNumber parameter doesn't match the value from the
                 access token context
    Generic404:
      description: The specified resource was not found
      headers:
        x-correlator:
          $ref: '#/components/headers/x-correlator'
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorInfo'
          example:
            status: 404
            code: CALL_FORWARDING.UNKNOWN_PHONE_NUMBER
            message: Call forwarding check can't be done because the phone
             number is unknown
    Generic409:
      description: Conflict
      headers:
        x-correlator:
          $ref: "#/components/headers/x-correlator"
      content:
        application/json:
          schema:
            $ref: "#/components/schemas/ErrorInfo"
          examples:
            GENERIC_409_ABORTED:
              description: Concurrency of processes of the same nature/scope
              value:
                status: 409
                code: ABORTED
                message: Concurrency conflict.
            GENERIC_409_ALREADY_EXISTS:
              description: Trying to create an existing resource
              value:
                status: 409
                code: ALREADY_EXISTS
                message: The resource that a client tried to create already
                 exists.
            GENERIC_409_CONFLICT:
              description: Duplication of an existing resource
              value:
                status: 409
                code: CONFLICT
                message: A specified resource duplicate entry found.
    Generic415:
      description: Unsupported Media Type
      headers:
        x-correlator:
          $ref: "#/components/headers/x-correlator"
      content:
        application/json:
          schema:
            $ref: "#/components/schemas/ErrorInfo"
          examples:
            GENERIC_415_UNSUPPORTED_MEDIA_TYPE:
              description: Payload format of the request is in an unsupported
               format by the Server.
              value:
                status: 415
                code: UNSUPPORTED_MEDIA_TYPE
                message: The server refuses to accept the request because the
                 payload format is in an unsupported format.
    Generic422:
      description: Unprocessable Content
      headers:
        x-correlator:
          $ref: "#/components/headers/x-correlator"
      content:
        application/json:
          schema:
            $ref: "#/components/schemas/ErrorInfo"
          examples:
            GENERIC_422_DEVICE_IDENTIFIERS_MISMATCH:
              description: Inconsistency between device identifiers not pointing
               to the same device
              value:
                status: 422
                code: DEVICE_IDENTIFIERS_MISMATCH
                message: Provided device identifiers are not consistent.
            GENERIC_422_DEVICE_NOT_APPLICABLE:
              description: Service is not available for the provided device
              value:
                status: 422
                code: DEVICE_NOT_APPLICABLE
                message: The service is not available for the provided device.
            GENERIC_422_UNIDENTIFIABLE_DEVICE:
              description: phone number not available neither from "phoneNumber"
               or from the access token.
              value:
                status: 422
                code: UNIDENTIFIABLE_DEVICE
                message: phone number not defined
    Generic429:
      description: Too Many Requests
      headers:
        x-correlator:
          $ref: "#/components/headers/x-correlator"
      content:
        application/json:
          schema:
            $ref: "#/components/schemas/ErrorInfo"
          examples:
            GENERIC_429_QUOTA_EXCEEDED:
              description: Request is rejected due to exceeding a business quota
               limit.
              value:
                status: 429
                code: QUOTA_EXCEEDED
                message: Either out of resource quota or reaching rate limiting.
            GENERIC_429_TOO_MANY_REQUESTS:
              description: API Server request limit is overpassed
              value:
                status: 429
                code: TOO_MANY_REQUESTS
                message: Either out of resource quota or reaching rate limiting.
    Generic500:
      description: Server error
      headers:
        x-correlator:
          $ref: '#/components/headers/x-correlator'
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorInfo'
          example:
            status: 500
            code: INTERNAL
            message: Server error
    Generic501:
      description: Not Implemented
      headers:
        x-correlator:
          $ref: "#/components/headers/x-correlator"
      content:
        application/json:
          schema:
            $ref: "#/components/schemas/ErrorInfo"
          examples:
            GENERIC_501_NOT_IMPLEMENTED:
              description: Service not implemented. The use of this code should
               be avoided as far as possible to get the objective to reach
               aligned implementations
              value:
                status: 501
                code: NOT_IMPLEMENTED
                message: This functionality is not implemented yet.
    Generic503:
      description: Service unavailable. Typically the server is down
      headers:
        x-correlator:
          $ref: '#/components/headers/x-correlator'
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorInfo'
          example:
            status: 503
            code: UNAVAILABLE
            message: Service unavailable
    Generic504:
      description: Request time exceeded. If it happens repeatedly, consider
       reducing the request complexity
      headers:
        x-correlator:
          $ref: '#/components/headers/x-correlator'
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorInfo'
          example:
            status: 504
            code: TIMEOUT
            message: Request timeout exceeded. Try later