feat(aws-iam): support maxSessionDuration for Role (#545)

Allow specifying a maximum session duration for roles.

Fixes #543

packages/@aws-cdk/aws-iam/lib/role.ts

@@ -41,6 +41,27 @@ export interface RoleProps {
      * Acknowledging IAM Resources in AWS CloudFormation Templates.
      */
     roleName?: string;
+
+    /**
+     * The maximum session duration (in seconds) that you want to set for the
+     * specified role. If you do not specify a value for this setting, the
+     * default maximum of one hour is applied. This setting can have a value
+     * from 1 hour (3600sec) to 12 (43200sec) hours.
+     *
+     * Anyone who assumes the role from the AWS CLI or API can use the
+     * DurationSeconds API parameter or the duration-seconds CLI parameter to
+     * request a longer session. The MaxSessionDuration setting determines the
+     * maximum duration that can be requested using the DurationSeconds
+     * parameter.
+     *
+     * If users don't specify a value for the DurationSeconds parameter, their
+     * security credentials are valid for one hour by default. This applies when
+     * you use the AssumeRole* API operations or the assume-role* CLI operations
+     * but does not apply when you use those operations to create a console URL.
+     *
+     * @link https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_use.html
+     */
+    maxSessionDurationSec?: number;
 }
 
 /**
@@ -85,11 +106,14 @@ export class Role extends Construct implements IIdentityResource, IPrincipal, ID
         this.assumeRolePolicy = createAssumeRolePolicy(props.assumedBy);
         this.managedPolicies = props.managedPolicyArns || [ ];
 
+        validateMaxSessionDuration(props.maxSessionDurationSec);
+
         const role = new cloudformation.RoleResource(this, 'Resource', {
             assumeRolePolicyDocument: this.assumeRolePolicy as any,
             managedPolicyArns: undefinedIfEmpty(() => this.managedPolicies),
             path: props.path,
             roleName: props.roleName,
+            maxSessionDuration: props.maxSessionDurationSec
         });
 
         this.roleArn = role.roleArn;
@@ -140,3 +164,13 @@ function createAssumeRolePolicy(principal: PolicyPrincipal) {
             .addPrincipal(principal)
             .addAction(principal.assumeRoleAction));
 }
+
+function validateMaxSessionDuration(duration?: number) {
+    if (duration === undefined) {
+        return;
+    }
+
+    if (duration < 3600 || duration > 43200) {
+        throw new Error(`maxSessionDuration is set to ${duration}, but must be >= 3600sec (1hr) and <= 43200sec (12hrs)`);
+    }
+}

packages/@aws-cdk/aws-iam/test/test.role.ts

@@ -117,5 +117,64 @@ export = {
         }));
 
         test.done();
+    },
+
+    'maxSessionDuration': {
+
+        'is not specified by default'(test: Test) {
+            const stack = new Stack();
+            new Role(stack, 'MyRole', { assumedBy: new ServicePrincipal('sns.amazonaws.com') });
+            expect(stack).toMatch({
+                Resources: {
+                  MyRoleF48FFE04: {
+                    Type: "AWS::IAM::Role",
+                    Properties: {
+                      AssumeRolePolicyDocument: {
+                        Statement: [
+                          {
+                            Action: "sts:AssumeRole",
+                            Effect: "Allow",
+                            Principal: {
+                              Service: "sns.amazonaws.com"
+                            }
+                          }
+                        ],
+                        Version: "2012-10-17"
+                      }
+                    }
+                  }
+                }
+            });
+            test.done();
+        },
+
+        'can be used to specify the maximum session duration for assuming the role'(test: Test) {
+            const stack = new Stack();
+
+            new Role(stack, 'MyRole', { maxSessionDurationSec: 3700, assumedBy: new ServicePrincipal('sns.amazonaws.com') });
+
+            expect(stack).to(haveResource('AWS::IAM::Role', {
+                MaxSessionDuration: 3700
+            }));
+
+            test.done();
+        },
+
+        'must be between 3600 and 43200'(test: Test) {
+            const stack = new Stack();
+
+            const assumedBy = new ServicePrincipal('bla');
+
+            new Role(stack, 'MyRole1', { assumedBy, maxSessionDurationSec: 3600 });
+            new Role(stack, 'MyRole2', { assumedBy, maxSessionDurationSec: 43200 });
+
+            const expected = (val: any) => `maxSessionDuration is set to ${val}, but must be >= 3600sec (1hr) and <= 43200sec (12hrs)`;
+            test.throws(() => new Role(stack, 'MyRole3', { assumedBy, maxSessionDurationSec: 60 }), expected(60));
+            test.throws(() => new Role(stack, 'MyRole4', { assumedBy, maxSessionDurationSec: 3599 }), expected(3599));
+            test.throws(() => new Role(stack, 'MyRole5', { assumedBy, maxSessionDurationSec: 43201 }), expected(43201));
+
+            test.done();
+        }
     }
+
 };