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CORS

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Updated at March 27, 2025

The x-yc-apigateway-cors-rules and x-yc-apigateway-cors extensions allow you to configure automatic processing of preflight requests based on the CORS feature.

CorsRuleObject

CorsRuleObject contains OpenAPI specification parameters that allow you to define a rule for handling CORS preflight requests.

Parameters

The table below lists the CorsRuleObject parameters.

Parameter Type Required Description
origin boolean, string, string[] Yes Defines the Access-Control-Allow-Origin header contents. If false, there is no CORS processing and the header is not included in the response. If true, the header will include the Origin request header contents. If the value is set as a string or an array of strings, it is inserted into the Access-Control-Allow-Origin response header as is.
methods string, string[] No Defines the contents of the Access-Control-Allow-Methods header. It can be set as a string with a comma-separated list of allowed HTTP methods or as an array of strings with one HTTP method in each. If not specified, the header will include the Access-Control-Request-Headers request header contents.
allowedHeaders string, string[] No Defines the contents of the Access-Control-Allow-Headers header. It can be set as a string with a comma-separated list of allowed headers or as an array of strings with one header in each. If it is not specified, the header is not included in the response.
exposedHeaders string, string[] No Defines the contents of the Access-Control-Expose-Headers header. It can be set as a string with a comma-separated list of allowed headers or as an array of strings with one header in each. If it is not specified, the header is not included in the response.
credentials boolean No Defines the contents of the Access-Control-Allow-Credentials header. If it is not specified, the header is not included in the response.
maxAge integer No Defines the contents of the Access-Control-Max-Age header. If it is not specified, the header is not included in the response.
optionsSuccessStatus integer No Determines the successful response code for a preflight request. The default value is 200.

X-yc-apigateway-cors-rules extension

With x-yc-apigateway-cors-rules, you can describe rules for handling preflight requests in the components section. You can reference the rules set in this way using the $ref parameter in the x-yc-apigateway-cors extension and apply them to different paths or the entire API gateway. For details, see cors for x-yc-apigateway extension.

X-yc-apigateway-cors extension

With x-yc-apigateway-cors, you can apply a rule for handling preflight requests to a specific path. The extension type is CorsRuleObject.

Specification examples

Example of a specification with a rule that allows any HTTP requests with any headers and from any domains

In this example, CORS preflight request processing is set up for the entire API gateway. The rule is set at the top level using the x-yc-apigateway extension's cors parameter.

openapi: "3.0.0"
info:
  version: 1.0.0
  title: Petstore API

x-yc-apigateway:
  cors:
    origin: '*'
    methods: '*'
    allowedHeaders: '*'

paths:
  /pets/{petId}:
    get:
      operationId: petById
      parameters:
        - in: path
          name: petId
          schema:
            type: integer
          required: true
          description: Pet identifier
      responses:
        '200':
          description: Pet
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Pet"
      x-yc-apigateway-integration:
        type: cloud_functions
        function_id: b095c95icn**********

components:
  schemas:
    Pet:
      type: object
      required:
        - id
        - name
      properties:
        id:
          type: integer
        name:
          type: string

Example of a specification that overrides a CORS rule

In this example, a general rule defined at the top level for the entire API gateway is overridden at the level of a specific path. The false value of the origin parameter disables preflight request processing in the API gateway, and the request is sent to an integration function. All CORS headers received in function responses are transmitted as is to a response from the API gateway.

openapi: "3.0.0"
info:
  version: 1.0.0
  title: Petstore API

x-yc-apigateway:
  cors:
    origin: '*'
    methods: '*'
    allowedHeaders: '*'

paths:
  /pets/{petId}:
    x-yc-apigateway-cors:
      origin: false
    options:
      operationId: prefligh********
      parameters:
        - in: path
          name: petId
          schema:
            type: integer
          required: true
          description: Pet identifier
      x-yc-apigateway-integration:
        type: cloud_functions
        function_id: b095c95icn**********

Specification example with a CORS rule that copies the Origin header to a response

openapi: "3.0.0"
info:
  version: 1.0.0
  title: Petstore API

paths:
  /pets/{petId}:
    x-yc-apigateway-cors:
      origin: true
      methods: [GET,POST,DELETE]
      allowedHeaders: x-custom-header
      exposedHeaders: x-custom-header
      maxAge: 3600
    get:
      operationId: petById
      parameters:
        - in: path
          name: petId
          schema:
            type: integer
          required: true
          description: Pet identifier
      responses:
        '200':
          description: Pet
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Pet"
      x-yc-apigateway-integration:
        type: cloud_functions
        function_id: b095c95icn**********

components:
  schemas:
    Pet:
      type: object
      required:
        - id
        - name
      properties:
        id:
          type: integer
        name:
          type: string

Example of a specification with a CORS rule defined in the components section

openapi: "3.0.0"
info:
  version: 1.0.0
  title: Petstore API

paths:
  /pets/{petId}:
    x-yc-apigateway-cors:
      $ref: "#/components/x-yc-apigateway-cors-rules/cors-rule"
    get:
      operationId: petById
      parameters:
        - in: path
          name: petId
          schema:
            type: integer
          required: true
          description: Pet identifier
      responses:
        '200':
          description: Pet
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Pet"
      x-yc-apigateway-integration:
        type: cloud_functions
        function_id: b095c95icn**********

components:
  x-yc-apigateway-cors-rules:
    cors-rule:
      origin:
        - https://foo.bar.org
        - https://foo1.bar2.org
      methods:
        - GET
        - POST
      allowedHeaders:
        - x-header-1
        - x-header-2
      exposedHeaders:
        - x-header-1
        - x-header-2
      credentials: true
      maxAge: 3600
      optionsSuccessStatus: 204

  schemas:
    Pet:
      type: object
      required:
        - id
        - name
      properties:
        id:
          type: integer
        name:
          type: string
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