Validate content

Стаття
08/30/2024

APPLIES TO: All API Management tiers

The validate-content policy validates the size or content of a request or response body against one or more supported schemas.

The following table shows the schema formats and request or response content types that the policy supports. Content type values are case insensitive.

Format	Content types
JSON	Examples: `application/json` `application/hal+json`
XML	Example: `application/xml`
SOAP	Allowed values: `application/soap+xml` for SOAP 1.2 APIs `text/xml` for SOAP 1.1 APIs

Note

The maximum size of the API schema that can be used by this validation policy is 4 MB. If the schema exceeds this limit, validation policies will return errors on runtime. To increase it, please contact support.

What content is validated

The policy validates the following content in the request or response against the schema:

Presence of all required properties.
Presence or absence of additional properties, if the schema has the additionalProperties field set. May be overridden with the allow-additional-properties attribute.
Types of all properties. For example, if a schema specifies a property as an integer, the request (or response) must include an integer and not another type, such as a string.
The format of the properties, if specified in the schema - for example, regex (if the pattern keyword is specified), minimum for integers, and so on.

Tip

For examples of regex pattern constraints that can be used in schemas, see OWASP Validation Regex Repository.

Note

Set the policy's elements and child elements in the order provided in the policy statement. To help you configure this policy, the portal provides a guided, form-based editor. Learn more about how to set or edit API Management policies.

Policy statement

<validate-content unspecified-content-type-action="ignore | prevent | detect" max-size="size in bytes" size-exceeded-action="ignore | prevent | detect" errors-variable-name="variable name">
    <content-type-map any-content-type-value="content type string" missing-content-type-value="content type string">
        <type from | when="content type string" to="content type string" />
    </content-type-map>
    <content type="content type string" validate-as="json | xml | soap" schema-id="schema id" schema-ref="#/local/reference/path" action="ignore | prevent | detect" allow-additional-properties="true | false" case-insensitive-property-names="true | false"/>
</validate-content>

Attributes

Attribute	Description	Required	Default
unspecified-content-type-action	Action to perform for requests or responses with a content type that isn’t specified in the API schema. Policy expressions are allowed.	Yes	N/A
max-size	Maximum length of the body of the request or response in bytes, checked against the `Content-Length` header. If the request body or response body is compressed, this value is the decompressed length. Maximum allowed value: 4 MB. Policy expressions are allowed.	Yes	N/A
size-exceeded-action	Action to perform for requests or responses whose body exceeds the size specified in `max-size`. Policy expressions are allowed.	Yes	N/A
errors-variable-name	Name of the variable in `context.Variables` to log validation errors to. Policy expressions aren't allowed.	No	N/A

Elements

Name	Description	Required
content-type-map	Add this element to map the content type of the incoming request or response to another content type that is used to trigger validation.	No
content	Add one or more of these elements to validate the content type in the request or response, or the mapped content type, and perform the specified action.	No

content-type-map attributes

Attribute	Description	Required	Default
any-content-type-value	Content type used for validation of the body of a request or response, regardless of the incoming content type. Policy expressions aren't allowed.	No	N/A
missing-content-type-value	Content type used for validation of the body of a request or response, when the incoming content type is missing or empty. Policy expressions aren't allowed.	No	N/A

content-type-map-elements

Name	Description	Required
type	Add one or more of these elements to map an incoming content type to a content type used for validation of the body of a request or response. Use `from` to specify a known incoming content type, or use `when` with a policy expression to specify any incoming content type that matches a condition. Overrides the mapping in `any-content-type-value` and `missing-content-type-value`, if specified.	No

content attributes

Attribute	Description	Required	Default
type	Content type to execute body validation for, checked against the content type header or the value mapped in `content-type-mapping`, if specified. If empty, it applies to every content type specified in the API schema. To validate SOAP requests and responses (`validate-as` attribute set to "soap"), set `type` to `application/soap+xml` for SOAP 1.2 APIs or `text/xml` for SOAP 1.1 APIs.	No	N/A
validate-as	Validation engine to use for validation of the body of a request or response with a matching `type`. Supported values: "json", "xml", "soap". When "soap" is specified, the XML from the request or response is extracted from the SOAP envelope and validated against an XML schema.	Yes	N/A
schema-id	Name of an existing schema that was added to the API Management instance for content validation. If not specified, the default schema from the API definition is used.	No	N/A
schema-ref	For a JSON schema specified in `schema-id`, optional reference to a valid local reference path in the JSON document. Example: `#/components/schemas/address`. The attribute should return a JSON object that API Management handles as a valid JSON schema. For an XML schema, `schema-ref` isn't supported, and any top-level schema element can be used as the root of the XML request or response payload. The validation checks that all elements starting from the XML request or response payload root adhere to the provided XML schema.	No	N/A
allow-additional-properties	Boolean. For a JSON schema, specifies whether to implement a runtime override of the `additionalProperties` value configured in the schema: - `true`: allow additional properties in the request or response body, even if the JSON schema's `additionalProperties` field is configured to not allow additional properties. - `false`: do not allow additional properties in the request or response body, even if the JSON schema's `additionalProperties` field is configured to allow additional properties. If the attribute isn't specified, the policy validates additional properties according to configuration of the `additionalProperties` field in the schema.	No	N/A
case-insensitive-property-names	Boolean. For a JSON schema, specifies whether to compare property names of JSON objects without regard to case. - `true`: compare property names case insensitively. - `false`: compare property names case sensitively.	No	false

Actions

The content validation policies include one or more attributes that specify an action, which API Management takes when validating an entity in an API request or response against the API schema.

An action may be specified for elements that are represented in the API schema and, depending on the policy, for elements that aren't represented in the API schema.
An action specified in a policy's child element overrides an action specified for its parent.

Available actions:

Action	Description
ignore	Skip validation.
prevent	Block the request or response processing, log the verbose validation error, and return an error. Processing is interrupted when the first set of errors is detected.
detect	Log validation errors, without interrupting request or response processing.

Usage

Policy sections: inbound, outbound, on-error
Policy scopes: global, workspace, product, API, operation
Gateways: classic, v2, consumption, self-hosted, workspace

Logs

Details about the validation errors during policy execution are logged to the variable in context.Variables specified in the errors-variable-name attribute in the policy's root element. When configured in a prevent action, a validation error blocks further request or response processing and is also propagated to the context.LastError property.

To investigate errors, use a trace policy to log the errors from context variables to Application Insights.

Performance implications

Adding a validation policy may affect API throughput. The following general principles apply:

The larger the API schema size, the lower the throughput will be.
The larger the payload in a request or response, the lower the throughput will be.
The size of the API schema has a larger impact on performance than the size of the payload.
Validation against an API schema that is several megabytes in size may cause request or response timeouts under some conditions. The effect is more pronounced in the Consumption and Developer tiers of the service.

We recommend performing load tests with your expected production workloads to assess the impact of validation policies on API throughput.

Schemas for content validation

By default, validation of request or response content uses JSON or XML schemas from the API definition. These schemas can be specified manually or generated automatically when importing an API from an OpenAPI or WSDL specification into API Management.

Using the validate-content policy, you may optionally validate against one or more JSON or XML schemas that you’ve added to your API Management instance and that aren't part of the API definition. A schema that you add to API Management can be reused across many APIs.

To add a schema to your API Management instance using the Azure portal:

In the portal, navigate to your API Management instance.
In the APIs section of the left-hand menu, select Schemas > + Add.
In the Create schema window, do the following:
1. Enter a Name (ID) for the schema.
2. In Schema type, select JSON or XML.
3. Enter a Description.
4. In Create method, do one of the following:
  - Select Create new and enter or paste the schema.
  - Select Import from file or Import from URL and enter a schema location.
    
    Note
    
    To import a schema from URL, the schema needs to be accessible over the internet from the browser.
5. Select Save.

API Management adds the schema resource at the relative URI /schemas/<schemaId>, and the schema appears in the list on the Schemas page. Select a schema to view its properties or to edit in a schema editor.

Note

A schema may cross-reference another schema that is added to the API Management instance. For example, include an XML schema added to API Management by using an element similar to:

<xs:include schemaLocation="/schemas/myschema" />

Tip

Open-source tools to resolve WSDL and XSD schema references and to batch-import generated schemas to API Management are available on GitHub.

Examples

JSON schema validation

In the following example, API Management interprets requests with an empty content type header or requests with a content type header application/hal+json as requests with the content type application/json. Then, API Management performs the validation in the detection mode against a schema defined for the application/json content type in the API definition. Messages with payloads larger than 100 KB are blocked. Requests containing additional properties are blocked, even if the schema's additionalProperties field is configured to allow additional properties.

<validate-content unspecified-content-type-action="prevent" max-size="102400" size-exceeded-action="prevent" errors-variable-name="requestBodyValidation">
    <content-type-map missing-content-type-value="application/json">
        <type from="application/hal+json" to="application/json" />
    </content-type-map>
    <content type="application/json" validate-as="json" action="detect" allow-additional-properties="false" />
</validate-content>

SOAP schema validation

In the following example, API Management interprets any request as a request with the content type application/soap+xml (the content type that's used by SOAP 1.2 APIs), regardless of the incoming content type. The request could arrive with an empty content type header, content type header of text/xml (used by SOAP 1.1 APIs), or another content type header. Then, API Management extracts the XML payload from the SOAP envelope and performs the validation in prevention mode against the schema named "myschema". Messages with payloads larger than 100 KB are blocked.

<validate-content unspecified-content-type-action="prevent" max-size="102400" size-exceeded-action="prevent" errors-variable-name="requestBodyValidation">
    <content-type-map any-content-type-value="application/soap+xml" />
    <content type="application/soap+xml" validate-as="soap" schema-id="myschema" action="prevent" /> 
</validate-content>

Validation errors

API Management generates content validation errors in the following format:

{
 "Name": string,
 "Type": string,
 "ValidationRule": string,
 "Details": string,
 "Action": string
}

The following table lists all possible errors of the validation policies.

Details: Can be used to investigate errors. Not meant to be shared publicly.
Public response: Error returned to the client. Does not leak implementation details.

When a validation policy specifies the prevent action and produces an error, the response from API management includes an HTTP status code: 400 when the policy is applied in the inbound section, and 502 when the policy is applied in the outbound section.

Name	Type	Validation rule	Details	Public response	Action
validate-content
	RequestBody	SizeLimit	Request's body is {size} bytes long and it exceeds the configured limit of {maxSize} bytes.	Request's body is {size} bytes long and it exceeds the limit of {maxSize} bytes.	detect / prevent
	ResponseBody	SizeLimit	Response's body is {size} bytes long and it exceeds the configured limit of {maxSize} bytes.	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
{messageContentType}	RequestBody	Unspecified	Unspecified content type {messageContentType} is not allowed.	Unspecified content type {messageContentType} is not allowed.	detect / prevent
{messageContentType}	ResponseBody	Unspecified	Unspecified content type {messageContentType} is not allowed.	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
	ApiSchema		API's schema does not exist or it could not be resolved.	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
	ApiSchema		API's schema does not specify definitions.	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
{messageContentType}	RequestBody / ResponseBody	MissingDefinition	API's schema does not contain definition {definitionName}, which is associated with the content type {messageContentType}.	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
{messageContentType}	RequestBody	IncorrectMessage	Body of the request does not conform to the definition {definitionName}, which is associated with the content type {messageContentType}. {valError.Message} Line: {valError.LineNumber}, Position: {valError.LinePosition}	Body of the request does not conform to the definition {definitionName}, which is associated with the content type {messageContentType}. {valError.Message} Line: {valError.LineNumber}, Position: {valError.LinePosition}	detect / prevent
{messageContentType}	ResponseBody	IncorrectMessage	Body of the response does not conform to the definition {definitionName}, which is associated with the content type {messageContentType}. {valError.Message} Line: {valError.LineNumber}, Position: {valError.LinePosition}	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
	RequestBody	ValidationException	Body of the request cannot be validated for the content type {messageContentType}. {exception details}	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
	ResponseBody	ValidationException	Body of the response cannot be validated for the content type {messageContentType}. {exception details}	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
validate-parameters / validate-headers
{paramName} / {headerName}	QueryParameter / PathParameter / RequestHeader	Unspecified	Unspecified {path parameter / query parameter / header} {paramName} is not allowed.	Unspecified {path parameter / query parameter / header} {paramName} is not allowed.	detect / prevent
{headerName}	ResponseHeader	Unspecified	Unspecified header {headerName} is not allowed.	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
	ApiSchema		API's schema doesn't exist or it couldn't be resolved.	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
	ApiSchema		API schema does not specify definitions.	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
{paramName}	QueryParameter / PathParameter / RequestHeader / ResponseHeader	MissingDefinition	API's schema does not contain definition {definitionName}, which is associated with the {query parameter / path parameter / header} {paramName}.	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
{paramName}	QueryParameter / PathParameter / RequestHeader	IncorrectMessage	Request cannot contain multiple values for the {query parameter / path parameter / header} {paramName}.	Request cannot contain multiple values for the {query parameter / path parameter / header} {paramName}.	detect / prevent
{headerName}	ResponseHeader	IncorrectMessage	Response cannot contain multiple values for the header {headerName}.	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
{paramName}	QueryParameter / PathParameter / RequestHeader	IncorrectMessage	Value of the {query parameter / path parameter / header} {paramName} does not conform to the definition. {valError.Message} Line: {valError.LineNumber}, Position: {valError.LinePosition}	The value of the {query parameter / path parameter / header} {paramName} does not conform to the definition. {valError.Message} Line: {valError.LineNumber}, Position: {valError.LinePosition}	detect / prevent
{headerName}	ResponseHeader	IncorrectMessage	Value of the header {headerName} does not conform to the definition. {valError.Message} Line: {valError.LineNumber}, Position: {valError.LinePosition}	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
{paramName}	QueryParameter / PathParameter / RequestHeader	IncorrectMessage	Value of the {query parameter / path parameter / header} {paramName} cannot be parsed according to the definition. {ex.Message}	Value of the {query parameter / path parameter / header} {paramName} couldn't be parsed according to the definition. {ex.Message}	detect / prevent
{headerName}	ResponseHeader	IncorrectMessage	Value of the header {headerName} couldn't be parsed according to the definition.	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
{paramName}	QueryParameter / PathParameter / RequestHeader	ValidationError	{Query parameter / Path parameter / Header} {paramName} cannot be validated. {exception details}	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
{headerName}	ResponseHeader	ValidationError	Header {headerName} cannot be validated. {exception details}	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent
validate-status-code
{status-code}	StatusCode	Unspecified	Response status code {status-code} is not allowed.	The request could not be processed due to an internal error. Contact the API owner.	detect / prevent

The following table lists all the possible Reason values of a validation error along with possible Message values:

Reason	Message
Bad request	{Details} for context variable, {Public response} for client
Response not allowed	{Details} for context variable, {Public response} for client

Content validation

For more information about working with policies, see:

Tutorial: Transform and protect your API
Policy reference for a full list of policy statements and their settings
Policy expressions
Set or edit policies
Reuse policy configurations
Policy snippets repo
Author policies using Microsoft Copilot in Azure

Поділитися через

Validate content

What content is validated

Policy statement

Attributes

Elements

content-type-map attributes

content-type-map-elements

content attributes

Actions

Usage

Logs

Performance implications

Schemas for content validation

Examples

JSON schema validation

SOAP schema validation

Validation errors

Зворотний зв’язок

Додаткові ресурси

Поділитися через

Validate content

What content is validated

Policy statement

Attributes

Elements

content-type-map attributes

content-type-map-elements

content attributes

Actions

Usage

Logs

Performance implications

Schemas for content validation

Examples

JSON schema validation

SOAP schema validation

Validation errors

Related policies

Related content

Зворотний зв’язок

Додаткові ресурси