feat(apigateway): add lambda request authorizer construct

This creates a common LambdaAuthorizer base class so that the
token and request authorizers can share common functionality.

.gitignore

@@ -32,3 +32,5 @@ cdk.out/
 
 # Yarn error log
 yarn-error.log
+
+.nycrc

packages/@aws-cdk/aws-apigateway/README.md

@@ -370,8 +370,8 @@ API Gateway interacts with the authorizer Lambda function handler by passing inp
 The event object that the handler is called with contains the `authorizationToken` and the `methodArn` from the request to the
 API Gateway endpoint. The handler is expected to return the `principalId` (i.e. the client identifier) and a `policyDocument` stating
 what the client is authorizer to perform.
-See https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-use-lambda-authorizer.html for a detailed specification on
-inputs and outputs of the lambda handler.
+See [here](https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-use-lambda-authorizer.html) for a detailed specification on
+inputs and outputs of the Lambda handler.
 
 The following code attaches a token-based Lambda authorizer to the 'GET' Method of the Book resource:
 
@@ -397,6 +397,44 @@ Authorizers can also be passed via the `defaultMethodOptions` property within th
 explicitly overridden, the specified defaults will be applied across all `Method`s across the `RestApi` or across all `Resource`s,
 depending on where the defaults were specified.
 
+#### Lambda-based request authorizer
+
+This module provides support for request-based Lambda authorizers. When a client makes a request to an API's methods configured with such
+an authorizer, API Gateway calls the Lambda authorizer, which takes the caller's identity as input and returns an IAM policy as output. 
+A request-based Lambda authorizer (also called a request authorizer) receives the caller's identity in a series of values pulled from
+the request, from the headers, query strings, etc.
+
+API Gateway interacts with the authorizer Lambda function handler by passing input and expecting the output in a specific format.
+The event object that the handler is called with contains the body of the request and the `methodArn` from the request to the
+API Gateway endpoint. The handler is expected to return the `principalId` (i.e. the client identifier) and a `policyDocument` stating
+what the client is authorizer to perform.
+See [here](https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-use-lambda-authorizer.html) for a detailed specification on
+inputs and outputs of the Lambda handler.
+
+The following code attaches a request-based Lambda authorizer to the 'GET' Method of the Book resource:
+
+```ts
+const authFn = new lambda.Function(this, 'booksAuthorizerLambda', {
+  // ...
+  // ...
+});
+
+const auth = new apigateway.RequestAuthorizer(this, 'booksAuthorizer', {
+  function: authFn,
+});
+
+books.addMethod('GET', new apigateway.HttpIntegration('http://amazon.com'), {
+  authorizer: auth
+});
+```
+
+By default, the `RequestAuthorizer` does not pass any kind of information from the request. This can,
+however, be modified by changing the `identitySource` property, and is required when specifying a value for caching.
+
+Authorizers can also be passed via the `defaultMethodOptions` property within the `RestApi` construct or the `Method` construct. Unless
+explicitly overridden, the specified defaults will be applied across all `Method`s across the `RestApi` or across all `Resource`s,
+depending on where the defaults were specified.
+
 ### Deployments
 
 By default, the `RestApi` construct will automatically create an API Gateway
@@ -539,7 +577,8 @@ running at one origin, access to selected resources from a different origin. A
 web application executes a cross-origin HTTP request when it requests a resource
 that has a different origin (domain, protocol, or port) from its own.
 
-You can add the CORS [preflight](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#Preflighted_requests) OPTIONS HTTP method to any API resource via the `defaultCorsPreflightOptions` option or by calling the `addCorsPreflight` on a specific resource.
+You can add the CORS [preflight](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#Preflighted_requests) OPTIONS 
+HTTP method to any API resource via the `defaultCorsPreflightOptions` option or by calling the `addCorsPreflight` on a specific resource.
 
 The following example will enable CORS for all methods and all origins on all resources of the API:
 

packages/@aws-cdk/aws-apigateway/lib/authorizers/lambda.ts

@@ -5,11 +5,7 @@ import { CfnAuthorizer } from '../apigateway.generated';
 import { Authorizer, IAuthorizer } from '../authorizer';
 import { RestApi } from '../restapi';
 
-/**
- * Properties for TokenAuthorizer
- */
-export interface TokenAuthorizerProps {
-
+export interface LambdaAuthorizerProps {
   /**
    * An optional human friendly name for the authorizer. Note that, this is not the primary identifier of the authorizer.
    *
@@ -27,14 +23,6 @@ export interface TokenAuthorizerProps {
    */
   readonly handler: lambda.IFunction;
 
-  /**
-   * The request header mapping expression for the bearer token. This is typically passed as part of the header, in which case
-   * this should be `method.request.header.Authorizer` where Authorizer is the header containing the bearer token.
-   * @see https://docs.aws.amazon.com/apigateway/api-reference/link-relation/authorizer-create/#identitySource
-   * @default 'method.request.header.Authorization'
-   */
-  readonly identitySource?: string;
-
   /**
    * How long APIGateway should cache the results. Max 1 hour.
    * Disable caching by setting this to 0.
@@ -43,14 +31,6 @@ export interface TokenAuthorizerProps {
    */
   readonly resultsCacheTtl?: Duration;
 
-  /**
-   * An optional regex to be matched against the authorization token. When matched the authorizer lambda is invoked,
-   * otherwise a 401 Unauthorized is returned to the client.
-   *
-   * @default - no regex filter will be applied.
-   */
-  readonly validationRegex?: string;
-
   /**
    * An optional IAM role for APIGateway to assume before calling the Lambda-based authorizer. The IAM role must be
    * assumable by 'apigateway.amazonaws.com'.
@@ -60,14 +40,7 @@ export interface TokenAuthorizerProps {
   readonly assumeRole?: iam.IRole;
 }
 
-/**
- * Token based lambda authorizer that recognizes the caller's identity as a bearer token,
- * such as a JSON Web Token (JWT) or an OAuth token.
- * Based on the token, authorization is performed by a lambda function.
- *
- * @resource AWS::ApiGateway::Authorizer
- */
-export class TokenAuthorizer extends Authorizer implements IAuthorizer {
+export abstract class LambdaAuthorizer extends Authorizer implements IAuthorizer {
 
   /**
    * The id of the authorizer.
@@ -78,11 +51,11 @@ export class TokenAuthorizer extends Authorizer implements IAuthorizer {
   /**
    * The ARN of the authorizer to be used in permission policies, such as IAM and resource-based grants.
    */
-  public readonly authorizerArn: string;
+  public authorizerArn: string;
 
-  private restApiId?: string;
+  protected restApiId?: string;
 
-  constructor(scope: Construct, id: string, props: TokenAuthorizerProps) {
+  protected constructor(scope: Construct, id: string, props: LambdaAuthorizerProps) {
     super(scope, id);
 
     if (props.resultsCacheTtl && props.resultsCacheTtl.toSeconds() > 3600) {
@@ -91,18 +64,7 @@ export class TokenAuthorizer extends Authorizer implements IAuthorizer {
 
     const restApiId = Lazy.stringValue({ produce: () => this.restApiId });
 
-    const resource = new CfnAuthorizer(this, 'Resource', {
-      name: props.authorizerName ?? this.node.uniqueId,
-      restApiId,
-      type: 'TOKEN',
-      authorizerUri: `arn:aws:apigateway:${Stack.of(this).region}:lambda:path/2015-03-31/functions/${props.handler.functionArn}/invocations`,
-      authorizerCredentials: props.assumeRole ? props.assumeRole.roleArn : undefined,
-      authorizerResultTtlInSeconds: props.resultsCacheTtl && props.resultsCacheTtl.toSeconds(),
-      identitySource: props.identitySource || 'method.request.header.Authorization',
-      identityValidationExpression: props.validationRegex,
-    });
-
-    this.authorizerId = resource.ref;
+    this.authorizerId = this.getResource(props).ref;
 
     this.authorizerArn = Stack.of(this).formatArn({
       service: 'execute-api',
@@ -138,4 +100,101 @@ export class TokenAuthorizer extends Authorizer implements IAuthorizer {
 
     this.restApiId = restApi.restApiId;
   }
-}
+
+  protected abstract getResource<T extends LambdaAuthorizerProps>(props: T): CfnAuthorizer;
+}
+
+/**
+ * Properties for TokenAuthorizer
+ */
+export interface TokenAuthorizerProps extends LambdaAuthorizerProps {
+  /**
+   * An optional regex to be matched against the authorization token. When matched the authorizer lambda is invoked,
+   * otherwise a 401 Unauthorized is returned to the client.
+   *
+   * @default - no regex filter will be applied.
+   */
+  readonly validationRegex?: string;
+
+  /**
+   * The request header mapping expression for the bearer token. This is typically passed as part of the header, in which case
+   * this should be `method.request.header.Authorizer` where Authorizer is the header containing the bearer token.
+   * @see https://docs.aws.amazon.com/apigateway/api-reference/link-relation/authorizer-create/#identitySource
+   * @default 'method.request.header.Authorization'
+   */
+  readonly identitySource?: string;
+}
+
+/**
+ * Token based lambda authorizer that recognizes the caller's identity as a bearer token,
+ * such as a JSON Web Token (JWT) or an OAuth token.
+ * Based on the token, authorization is performed by a lambda function.
+ *
+ * @resource AWS::ApiGateway::Authorizer
+ */
+export class TokenAuthorizer extends LambdaAuthorizer {
+
+  constructor(scope: Construct, id: string, props: TokenAuthorizerProps) {
+    super(scope, id, props);
+  }
+
+  protected getResource(props: TokenAuthorizerProps): CfnAuthorizer {
+    const restApiId = Lazy.stringValue({ produce: () => this.restApiId });
+
+    return new CfnAuthorizer(this, 'Resource', {
+      name: props.authorizerName ?? this.node.uniqueId,
+      restApiId,
+      type: 'TOKEN',
+      authorizerUri: `arn:aws:apigateway:${Stack.of(this).region}:lambda:path/2015-03-31/functions/${props.handler.functionArn}/invocations`,
+      authorizerCredentials: props.assumeRole ? props.assumeRole.roleArn : undefined,
+      authorizerResultTtlInSeconds: props.resultsCacheTtl && props.resultsCacheTtl.toSeconds(),
+      identitySource: props.identitySource || 'method.request.header.Authorization',
+      identityValidationExpression: props.validationRegex,
+    });
+  }
+}
+
+/**
+ * Properties for RequestAuthorizerProps
+ */
+export interface RequestAuthorizerProps extends LambdaAuthorizerProps {
+  /**
+   * An array of request header mapping expressions for identities. This is typically passed as part of the header,
+   * in which case this should be `method.request.header.Authorizer` where Authorizer is the header containing the
+   * bearer token.
+   * @see https://docs.aws.amazon.com/apigateway/api-reference/link-relation/authorizer-create/#identitySource
+   */
+  readonly identitySource?: string[];
+}
+
+/**
+ * Request-based lambda authorizer that recognizes the caller's identity via request parameters,
+ * such as headers, paths, query strings, stage variables, or context variables.
+ * Based on the request, authorization is performed by a lambda function.
+ *
+ * @resource AWS::ApiGateway::Authorizer
+ */
+export class RequestAuthorizer extends LambdaAuthorizer {
+
+  constructor(scope: Construct, id: string, props: RequestAuthorizerProps) {
+    super(scope, id, props);
+
+    if (props.resultsCacheTtl && props.identitySource?.length === 0) {
+      throw new Error(`At least one Identity Source is required for a REQUEST-based Lambda authorizer.`);
+    }
+  }
+
+  protected getResource(props: RequestAuthorizerProps): CfnAuthorizer {
+    const restApiId = Lazy.stringValue({ produce: () => this.restApiId });
+
+    return new CfnAuthorizer(this, 'Resource', {
+      name: props.authorizerName ?? this.node.uniqueId,
+      restApiId,
+      type: 'REQUEST',
+      authorizerUri: `arn:aws:apigateway:${Stack.of(this).region}:lambda:path/2015-03-31/functions/${props.handler.functionArn}/invocations`,
+      authorizerCredentials: props.assumeRole ? props.assumeRole.roleArn : undefined,
+      authorizerResultTtlInSeconds: props.resultsCacheTtl && props.resultsCacheTtl.toSeconds(),
+      identitySource: props.identitySource?.join(','),
+    });
+  }
+}