CAMARA Call Forwarding Signal 0.4.0 as certified under GSMA Open Gateway. Exposes whether unconditional or conditional call forwarding is active on a subscriber line, a signal used to detect social-engineering and call-diversion fraud.
---
openapi: 3.0.3
############################################################################
# API info #
############################################################################
info:
title: Call Forwarding Signal
description: |
# Overview
The Call Forwarding Signal API provides the API Consumer with
information about the status of the Call Forwarding Service on a specific
phone number. The main scope of the Call Forwarding Signal 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 Call Forwarding
Signal 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 Call Forwarding Signal API can be invoked to detect if the unconditional
call forwarding service is active. The Call Forwarding Signal 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 different type of settings are returned ('conditional_busy',
'conditional_not_reachable', 'conditional_no_answer').
**Example use cases:**
[**Bank Frauds**](https://github.com/camaraproject/CallForwardingSignal/discussions/3#discussioncomment-8694420)
[**Alert Interception**](https://github.com/camaraproject/CallForwardingSignal/discussions/3#discussioncomment-8701847)
[**Call Forwarding Verification**](https://github.com/camaraproject/CallForwarding\Signal/discussions/3#discussioncomment-8915595)
# Quick Start
The Call Forwarding Signal API is a REST API based on the
CreateCallForwardingSignal resource.
This resource can be used, by the API Consumer, to specify the phone number
on which the Call Forwarding Service status must be verified, in case of
two-legged authentication. If three-legged authentication is used the phone
number is instead 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 Call Forwarding Signal API verifies
if a call forwarding
service is active on this phone number. Note: this parameter must be
must be provided/valued only in case of two-legged authentication.
In case of three-legged authentication the phone number is retrieved by
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 Call Forwarding Signal 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?
# API Documentation
## Details
The Call Forwarding Signal 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.
# Authorization and authentication
The "Camara Security and Interoperability Profile" provides details of how
an API consumer requests an access token. Please refer to Identity and
Consent Management
(https://github.com/camaraproject/IdentityAndConsentManagement/)
for the released version of the profile.
The specific authorization flows to be used will be agreed upon during the
onboarding process, happening between the API consumer and the API
provider, taking into account the declared purpose for accessing the API,
whilst also being subject to the prevailing legal framework dictated by
local legislation.
In cases where personal 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 three-legged access tokens is mandatory. This ensures that
the API remains in compliance with privacy regulations, upholding the
principles of transparency and user-centric privacy-by-design.
# Identifying the phone number from the access token
This API requires the API consumer to identify a phone number as the
subject of the API as follows:
- When the API is invoked using a two-legged access token, the subject
will be identified from the optional `phoneNumber` object field, which
therefore MUST be provided.
- When a three-legged access token is used however, this optional
identifier MUST NOT be provided, as the subject will be uniquely
identified from the access token.
This approach simplifies API usage for API consumers using a
three-legged access token to invoke the API by relying on the
information that is associated with the access token and was
identified during the authentication process.
## Error handling:
- If the subject cannot be identified from the access token and the
optional `phoneNumber` object field is not included in the request, then
the server will return an error with the
`422 MISSING_IDENTIFIER` error code.
- If the subject can be identified from the access token and the
optional `phoneNumber` object field is also included in the request, then
the server will return an error with the `422 UNNECESSARY_IDENTIFIER`
error code. This will be the case even if the same device is
identified by these two methods, as the server is unable to make
this comparison.
# Additional CAMARA error responses
The list of error codes in this API specification is not exhaustive.
Therefore the API specification may not document some non-mandatory error
statuses as indicated in `CAMARA API Design Guide`.
Please refer to the `CAMARA_common.yaml` of the Commonalities Release
associated to this API version for a complete list of error responses.
The applicable Commonalities Release can be identified in the
`API Readiness Checklist` document associated to this API version.
As a specific rule, error `501 - NOT_IMPLEMENTED` can be only a possible
error response if it is explicitly documented in the API.
# FAQ's
(FAQs will be added in a later version of the documentation)
version: 0.4.0
license:
name: Apache 2.0
url: https://www.apache.org/licenses/LICENSE-2.0.html
x-camara-commonalities: 0.6
externalDocs:
description: Product documentation at CAMARA
url: https://github.com/camaraproject/CallForwardingSignal
############################################################################
# Servers #
############################################################################
servers:
- url: "{apiRoot}/call-forwarding-signal/v0.4"
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, being 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'
"401":
$ref: "#/components/responses/Generic401"
"403":
$ref: "#/components/responses/Generic403"
"422":
$ref: "#/components/responses/Generic422"
"429":
$ref: "#/components/responses/Generic429"
/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 which 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 Call Forwarding Signal 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'
"401":
$ref: "#/components/responses/Generic401"
"403":
$ref: "#/components/responses/Generic403"
"422":
$ref: "#/components/responses/Generic422"
"429":
$ref: "#/components/responses/Generic429"
"501":
$ref: "#/components/responses/Generic501"
############################################################################
# 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:
$ref: "#/components/schemas/XCorrelator"
headers:
x-correlator:
description: Correlation id for the different services
schema:
$ref: "#/components/schemas/XCorrelator"
############################################################################
# Resources #
############################################################################
schemas:
UnconditionalCallForwardingSignal:
description: resource containing the information about the Unconditional
Call Forwarding Service for the given phone number (PhoneNumber)
type: object
properties:
active:
type: boolean
description: Indicates if the unconditional call forwarding service
is active.
CallForwardingSignal:
description: resource containing the list of the Call
Forwarding Services active for the given phone number (PhoneNumber). The
possible states are, 'inactive' (no call forwarding service activated),
'unconditional' (call forwarded independently from the device status),
'conditional_busy' (call forwarded if the device is on an active call),
'conditional_not_reachable' (call forwarded if the device is not
reachable), 'conditional_no_answer' (call forwarded if the device doesn't
answer the incoming call).
type: array
items:
type: string
enum:
- 'inactive'
- 'unconditional'
- 'conditional_busy'
- 'conditional_not_reachable'
- 'conditional_no_answer'
example:
- 'unconditional'
- 'conditional_busy'
- 'conditional_no_answer'
minItems: 1
XCorrelator:
type: string
pattern: ^[a-zA-Z0-9-_:;.\/<>{}]{0,256}$
example: "b4333c46-49c0-4f62-80d7-f0ef930f1c46"
############################################################################
# Request #
############################################################################
CreateCallForwardingSignal:
description: resource containing the phone number (PhoneNumber) regarding
which the Call Forwarding Service must be checked. To be provided/valued
only in case of two-legged authentication. If provided/valued with
three-legged authentication a 422-UNNECESSARY_IDENTIFIER error code is
returned.
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:
type: object
required:
- status
- code
- message
properties:
status:
type: integer
description: HTTP response status code
code:
type: string
description: A human-readable code to describe the error
message:
type: string
description: A human-readable description of what the event represents
responses:
Generic400:
description: Bad Request
headers:
x-correlator:
$ref: "#/components/headers/x-correlator"
content:
application/json:
schema:
allOf:
- $ref: "#/components/schemas/ErrorInfo"
- type: object
properties:
status:
enum:
- 400
code:
enum:
- INVALID_ARGUMENT
examples:
GENERIC_400_INVALID_ARGUMENT:
description: Invalid Argument. Generic Syntax Exception
value:
status: 400
code: INVALID_ARGUMENT
message: Client specified an invalid argument, request body or
query param.
Generic401:
description: Unauthorized
headers:
x-correlator:
$ref: "#/components/headers/x-correlator"
content:
application/json:
schema:
allOf:
- $ref: "#/components/schemas/ErrorInfo"
- type: object
properties:
status:
enum:
- 401
code:
enum:
- UNAUTHENTICATED
examples:
GENERIC_401_UNAUTHENTICATED:
description: Request cannot be authenticated and a new authentication
is required
value:
status: 401
code: UNAUTHENTICATED
message: Request not authenticated due to missing, invalid, or expired
credentials. A new authentication is required.
Generic403:
description: Forbidden
headers:
x-correlator:
$ref: "#/components/headers/x-correlator"
content:
application/json:
schema:
allOf:
- $ref: "#/components/schemas/ErrorInfo"
- type: object
properties:
status:
enum:
- 403
code:
enum:
- PERMISSION_DENIED
examples:
GENERIC_403_PERMISSION_DENIED:
description: Permission denied. OAuth2 token access does not have
the required scope or when the user fails operational security
value:
status: 403
code: PERMISSION_DENIED
message: Client does not have sufficient permissions to perform
this action.
Generic404:
description: Not found
headers:
x-correlator:
$ref: "#/components/headers/x-correlator"
content:
application/json:
schema:
allOf:
- $ref: "#/components/schemas/ErrorInfo"
- type: object
properties:
status:
enum:
- 404
code:
enum:
- NOT_FOUND
- IDENTIFIER_NOT_FOUND
examples:
GENERIC_404_NOT_FOUND:
description: Resource is not found
value:
status: 404
code: NOT_FOUND
message: The specified resource is not found.
GENERIC_404_IDENTIFIER_NOT_FOUND:
description: Call forwarding check can't be done because the
phone number is unknown.
value:
status: 404
code: IDENTIFIER_NOT_FOUND
message: Device identifier not found.
Generic422:
description: Unprocessable Content
headers:
x-correlator:
$ref: "#/components/headers/x-correlator"
content:
application/json:
schema:
allOf:
- $ref: "#/components/schemas/ErrorInfo"
- type: object
properties:
status:
enum:
- 422
code:
enum:
- SERVICE_NOT_APPLICABLE
- MISSING_IDENTIFIER
- UNNECESSARY_IDENTIFIER
examples:
GENERIC_422_SERVICE_NOT_APPLICABLE:
description: Service not applicable for the provided
identifier
value:
status: 422
code: SERVICE_NOT_APPLICABLE
message: The service is not available for the
provided identifier.
GENERIC_422_MISSING_IDENTIFIER:
description: An identifier is not included in the
request and the device or phone number identification
cannot be derived from the 3-legged access token
value:
status: 422
code: MISSING_IDENTIFIER
message: The phone number cannot be identified.
GENERIC_422_UNNECESSARY_IDENTIFIER:
description: An explicit identifier is provided when
a device or phone number has already been identified
from the access token
value:
status: 422
code: UNNECESSARY_IDENTIFIER
message: The phone number is already identified by the
access token.
Generic429:
description: Too Many Requests
headers:
x-correlator:
$ref: "#/components/headers/x-correlator"
content:
application/json:
schema:
allOf:
- $ref: "#/components/schemas/ErrorInfo"
- type: object
properties:
status:
enum:
- 429
code:
enum:
- QUOTA_EXCEEDED
- TOO_MANY_REQUESTS
examples:
GENERIC_429_QUOTA_EXCEEDED:
description: Request is rejected due to exceeding a
business quota limit
value:
status: 429
code: QUOTA_EXCEEDED
message: Out of resource quota.
GENERIC_429_TOO_MANY_REQUESTS:
description: Access to the API has been temporarily
blocked due to rate or spike arrest limits being reached
value:
status: 429
code: TOO_MANY_REQUESTS
message: Rate limit reached.
Generic501:
description: Not Implemented
headers:
x-correlator:
$ref: "#/components/headers/x-correlator"
content:
application/json:
schema:
allOf:
- $ref: "#/components/schemas/ErrorInfo"
- type: object
properties:
status:
enum:
- 501
code:
enum:
- NOT_IMPLEMENTED
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.