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Request Validator

By Kong Inc.

Looking for the plugin's configuration parameters? You can find them in the Request Validator configuration reference doc.

Validate requests before they reach their upstream service. Supports validating the schema of the body and the parameters of the request using either Kong’s own schema validator (body only) or a JSON Schema Draft 4 compliant validator.

Content-Type Validation

The request Content-Type header is validated against the plugin’s allowed_content_types setting. If the request Content-Type is not listed, the request will be rejected with an HTTP/400 error: {"message":"specified Content-Type is not allowed"}

The parameter is strictly validated, which means a request with a parameter (for example, application/json; charset=UTF-8) is NOT considered valid for one without the same parameter (for example, application/json). The type, subtype, parameter names, and the value of the charset parameter are not case sensitive based on the RFC explanation.

When setting this configuration, the Content-Type header only gets validated when body_schema is configured.

Body Validation

Request body validation is only performed for requests with application/json Content-Type or when +json is suffixed in the request Content-Type’s subtype (for example, application/merge-patch+json).

For requests with any other allowed Content-Type, body validation is skipped. In that case, the request is proxied to the upstream without validating the body.

Examples

Overview

By applying the plugin to a Service, all requests to that Service will be validated before being proxied.

Use a request like this:

curl -i -X POST http://localhost:8001/services/{service}/plugins \
  --data "name=request-validator" \
  --data "config.version=kong" \
  --data 'config.body_schema=[{\"name\":{\"type\": \"string\", \"required\": true}}]'

Add the following entry to the plugins: section in the declarative configuration file:

plugins:
- name: request-validator
  service: {service}
  config:
    version: kong
    body_schema:
      name:
        type: string
        required: true

In this example, the request body data would have to be valid JSON and conform to the schema specified in body_schema - i.e., it would be required to contain a name field only, which needs to be a string.

In case the validation fails, a 400 Bad Request will be returned as the response.

Schema Definition

For using the JSON Schema Draft 4-compliant validator, see the JSON Schema website for details on the format and examples. The rest of this paragraph will explain the Kong schema.

The config.body_schema field expects a JSON array with the definition of each field expected to be in the request body; for example:

Each field definition contains the following attributes:

Attribute Required Description
type yes The expected type for the field
required no Whether the field is required

Additionally, specific types may have their own required fields:

Map:

Attribute Required Description
keys yes The schema for the map keys
values yes The schema for the map values

Example string-boolean map:

{
  "type": "map",
  "keys": {
    "type": "string"
  },
  "values": {
    "type": "boolean"
  }
}

Array:

Attribute Required Description
elements yes The array’s elements schema

Example integer array schema:

{
  "type": "array",
  "elements": {
    "type": "integer"
  }
}

Record:

Attribute Required Description
fields yes The record schema

Example record schema:

{
  "type": "record",
  "fields": [
    {
      "street": {
        "type": "string",
      }
    },
    {
      "zipcode": {
        "type": "string",
      }
    }
  ]
}

The type field assumes one the following values:

  • string
  • number
  • integer
  • boolean
  • map
  • array
  • record

Each field specification may also contain validators, which perform specific validations:

Validator Applies to Description
between Integers Whether the value is between two integers. Specified as an array; for example, {1, 10}
len_eq Arrays, Maps, Strings Whether an array’s length is a given value
len_min Arrays, Maps, Strings Whether an array’s length is at least a given value
len_max Arrays, Maps, strings Whether an array’s length is at most a given value
match Strings True if the value matches a given Lua pattern **
not_match String True if the value doesn’t match a given Lua pattern **
match_all Arrays True if all strings in the array match the specified Lua pattern **
match_none Arrays True if none of the strings in the array match the specified Lua pattern **
match_any Arrays True if any one of the strings in the array matches the specified Lua pattern **
starts_with Strings True if the string value starts with the specified substring
one_of Strings, Numbers, Integers True if the string field value matches one of the specified values
timestamp Integers True if the field value is a valid timestamp
uuid Strings True if the string is a valid UUID

Note: To learn more, see Lua patterns.

Semantic validation for format attribute

This feature is only supported in JSON Schema Draft 4.

Structural validation alone may be insufficient to validate that an instance meets all the requirements of an application. The format keyword is defined to allow interoperable semantic validation for a fixed subset of values that are accurately described by authoritative resources, be they RFCs or other external specifications. The following attributes are available:

Attribute Description
date defined by RFC 3339, sections 5.6 and further validated by 5.7
date-time defined by RFC 3339, sections 5.6
time defined by RFC 3339, sections 5.6 and further validated by 5.7

Note: The value of the format attribute must be a string.

Example date schema:

{
  "type": "string",
  "format": "date"
}

Kong Schema Example

[
  {
    "name": {
      "type": "string",
      "required": true
    }
  },
  {
    "age": {
      "type": "integer",
      "required": true
    }
  },
  {
    "address": {
      "type": "record",
      "required": true,
      "fields": [
        {
          "street": {
            "type": "string",
            "required": true
          }
        },
        {
          "zipcode": {
            "type": "string",
            "required": true
          }
        }
      ]
    }
  },
  {
    "born": {
      "type": "string",
      "format": "date-time",
      "required": true
    }
  }
]

Such a schema would validate the following request body:

{
  "name": "Gruce The Great",
  "age": 4,
  "address": {
    "street": "251 Post St.",
    "zipcode": "94108"
  },
  "born": "2009-07-20T08:30:37.012Z"
}

Parameter Schema Definition

You can setup definitions for each parameter based on the OpenAPI Specification and the plugin will validate each parameter against it. For more information, see the OpenAPI specification or the OpenAPI examples.

Fixed Fields

Field Name Type Description
name string REQUIRED. The name of the parameter. Parameter names are case sensitive, and corresponds to the parameter name used by the in property. If in is "path", the name field MUST correspond to the named capture group from the configured route.
in string REQUIRED. The location of the parameter. Possible values are query, header, or path.
required boolean REQUIRED Determines whether this parameter is mandatory.
style string REQUIRED when schema and explode are set
Describes how the parameter value will be deserialized depending on the type of the parameter value.
schema string REQUIRED when style and explode are set
The schema defining the type used for the parameter. It is validated using draft4 for JSON Schema draft 4 compliant validator. In addition to being a valid JSON Schema, the parameter schema MUST have a top-level type property to enable proper deserialization before validating.
explode boolean REQUIRED when schema and style are set
When this is true, parameter values of type array or object generate separate parameters for each value of the array or key-value pair of the map. For other types of parameters this property has no effect.

Examples

In this example, use the plugin to validate a request’s path parameter.

  1. Add a Service to Kong:

    curl -i -X POST http://localhost:8001/services \
  --data name=httpbin \
  --data url=https://httpbin.konghq.com

HTTP/1.1 201 Created
..

{
  "host":"httpbin.konghq.com",
  "created_at":1563479714,
  "connect_timeout":60000,
  "id":"0a7f3795-bc92-43b5-aada-258113b7c4ed",
  "protocol":"http",
  "name":"httpbin",
  "read_timeout":60000,
  "port":80,
  "path":null,
  "updated_at":1563479714,
  "retries":5,
  "write_timeout":60000
}

  2. Add a Route with named capture group:

    curl -i -X POST http://localhost:8001/services/httpbin/routes \
  --data paths="~/status/(?<status_code>\d%+)" \
  --data strip_path=false

HTTP/1.1 201 Created
..

{
  "created_at": 1563481399,
  "methods": null,
  "id": "cd78749a-33a3-4bbd-9560-588eaf4116d3",
  "service": {
    "id": "0a7f3795-bc92-43b5-aada-258113b7c4ed"
  },
  "name": null,
  "hosts": null,
  "updated_at": 1563481399,
  "preserve_host": false,
  "regex_priority": 0,
  "paths": [
    "\\/status\\/(?<status_code>\\d+)"
  ],
  "sources": null,
  "destinations": null,
  "snis": null,
  "protocols": [
    "http",
    "https"
  ],
  "strip_path": false
}

  3. Enable request-validator plugin to validate body and parameter:

     curl -i -X POST http://localhost:8001/services/httpbin/plugins \
   --header "Content-Type: application/json" \
   --data @parameter_schema.json

 HTTP/1.1 201 Created
 ..

 {
   "created_at": 1563483059,
   "config": {
     "body_schema": "{\"properties\":{\"name\":{\"type\":\"string\"}},\"required\":[\"name\"]}",
     "parameter_schema": [
       {
         "style": "simple",
         "required": true,
         "in": "path",
         "schema": "{\"type\": \"number\"}",
         "explode": false,
         "name": "status_code"
       }
     ],
     "version": "draft4"
   },
   "id": "ad91a2d4-6217-4d34-9133-4a2508ddda9f",
   "service": {
     "id": "0a7f3795-bc92-43b5-aada-258113b7c4ed"
   },
   "enabled": true,
   "run_on": "first",
   "consumer": null,
   "route": null,
   "name": "request-validator"
 }

    Content of file parameter_schema.json:

     {
   "name": "request-validator",
   "config": {
     "body_schema": "{\"properties\":{\"name\":{\"type\":\"string\"}},\"required\":[\"name\"]}",
     "version": "draft4",
     "parameter_schema": [
       {
         "name": "status_code",
         "in": "path",
         "required": true,
         "schema": "{\"type\": \"number\"}",
         "style": "simple",
         "explode": false
       }
     ]
   }
 }

  4. In these step examples, validation ensures that status_code is a number and the body contains a parameter called name.

    A proxy request with a non-numerical status code is blocked:

     curl -i -X POST \
 --url http://localhost:8000/status/abc \
 --header 'Content-Type: application/json' \
 --data '{ "name": "foo" }'
 HTTP/1.1 400 Bad Request
 ...

 {"message":"request param doesn't conform to schema"}

    A proxy request with a numeric status code is allowed:

     curl -i -X POST \
 --url http://localhost:8000/status/123 \
 --header 'Content-Type: application/json' \
 --data '{ "name": "foo" }'
 HTTP/1.1 200 OK
 X-Kong-Upstream-Latency: 163
 X-Kong-Proxy-Latency: 37
 ...

Further References

The Kong schema validation format is based on the plugin schemas. For more information, see the Kong plugin docs on storing custom entities.