fix(codebuild): correctly handle permissions for Projects inside VPC.

A CodeBuild Project needs to have appropriate EC2 permissions on creation
when it uses a VPC. However, the default Policy that a Project Role has
depends on the Project itself (for CloudWatch Logs permissions).
Because of that, add a dependency between the Policy containing the EC2
permissions and the Project.

Also correctly handle the case when the Project's Role is imported.

Fixes #2651
Fixes #2652

packages/@aws-cdk/aws-codebuild/lib/project.ts

@@ -6,7 +6,7 @@ import ecr = require('@aws-cdk/aws-ecr');
 import events = require('@aws-cdk/aws-events');
 import iam = require('@aws-cdk/aws-iam');
 import kms = require('@aws-cdk/aws-kms');
-import { Aws, Construct, IResource, Resource, Token } from '@aws-cdk/cdk';
+import { Aws, CfnResource, Construct, IResource, Resource, Token } from '@aws-cdk/cdk';
 import { BuildArtifacts, CodePipelineBuildArtifacts, NoBuildArtifacts } from './artifacts';
 import { Cache } from './cache';
 import { CfnProject } from './codebuild.generated';
@@ -707,6 +707,8 @@ export class Project extends ProjectBase {
       vpcConfig: this.configureVpc(props),
     });
 
+    this.addVpcRequiredPermissions(props);
+
     this.projectArn = resource.projectArn;
     this.projectName = resource.projectName;
 
@@ -727,20 +729,6 @@ export class Project extends ProjectBase {
     }
   }
 
-  /**
-   * Add a permission only if there's a policy attached.
-   * @param statement The permissions statement to add
-   */
-  public addToRoleInlinePolicy(statement: iam.PolicyStatement) {
-    if (this.role) {
-      const policy = new iam.Policy(this, 'PolicyDocument', {
-        policyName: 'CodeBuildEC2Policy',
-        statements: [statement]
-      });
-      this.role.attachInlinePolicy(policy);
-    }
-  }
-
   /**
    * Adds a secondary source to the Project.
    *
@@ -882,7 +870,29 @@ export class Project extends ProjectBase {
       });
       this._securityGroups = [securityGroup];
     }
-    this.addToRoleInlinePolicy(new iam.PolicyStatement()
+
+    return {
+      vpcId: props.vpc.vpcId,
+      subnets: props.vpc.selectSubnets(props.subnetSelection).subnetIds,
+      securityGroupIds: this._securityGroups.map(s => s.securityGroupId)
+    };
+  }
+
+  private addVpcRequiredPermissions(props: ProjectProps): void {
+    if (!props.vpc) {
+      return;
+    }
+
+    this.addToRolePolicy(new iam.PolicyStatement()
+      .addResource(`arn:aws:ec2:${Aws.region}:${Aws.accountId}:network-interface/*`)
+      .addAction('ec2:CreateNetworkInterfacePermission')
+      .addCondition('StringEquals', {
+        'ec2:Subnet': props.vpc
+          .selectSubnets(props.subnetSelection).subnetIds
+          .map(si => `arn:aws:ec2:${Aws.region}:${Aws.accountId}:subnet/${si}`),
+        'ec2:AuthorizedService': "codebuild.amazonaws.com",
+      }));
+    this.addInlineEc2Policy(new iam.PolicyStatement()
       .addAllResources()
       .addActions(
         'ec2:CreateNetworkInterface',
@@ -891,22 +901,31 @@ export class Project extends ProjectBase {
         'ec2:DescribeSubnets',
         'ec2:DescribeSecurityGroups',
         'ec2:DescribeDhcpOptions',
-        'ec2:DescribeVpcs'
+        'ec2:DescribeVpcs',
       ));
-    this.addToRolePolicy(new iam.PolicyStatement()
-      .addResource(`arn:aws:ec2:${Aws.region}:${Aws.accountId}:network-interface/*`)
-      .addCondition('StringEquals', {
-        "ec2:Subnet": props.vpc
-          .selectSubnets(props.subnetSelection).subnetIds
-          .map(si => `arn:aws:ec2:${Aws.region}:${Aws.accountId}:subnet/${si}`),
-        "ec2:AuthorizedService": "codebuild.amazonaws.com"
-      })
-      .addAction('ec2:CreateNetworkInterfacePermission'));
-    return {
-      vpcId: props.vpc.vpcId,
-      subnets: props.vpc.selectSubnets(props.subnetSelection).subnetIds,
-      securityGroupIds: this._securityGroups.map(s => s.securityGroupId)
-    };
+  }
+
+  private addInlineEc2Policy(statement: iam.PolicyStatement) {
+    if (this.role) {
+      // If the Role is imported, the Policy will be left dangling,
+      // not attached to any IAM entity, which is invalid in CFN.
+      // Because of that, check for that case before creating the Policy
+      const cfnRole = this.role.node.tryFindChild('Resource') as CfnResource;
+      if (cfnRole) {
+        const policy = new iam.Policy(this, 'PolicyDocument', {
+          policyName: 'CodeBuildEC2Policy',
+          statements: [statement]
+        });
+        this.role.attachInlinePolicy(policy);
+
+        // add an explicit dependency between the EC2 Policy and this Project -
+        // otherwise, creating the Project fails,
+        // as it requires these permissions to be already attached to the Project's Role
+        const cfnPolicy = policy.node.findChild('Resource') as CfnResource;
+        const cfnProject = this.node.findChild('Resource') as CfnResource;
+        cfnProject.addDependsOn(cfnPolicy);
+      }
+    }
   }
 
   private parseArtifacts(props: ProjectProps) {

packages/@aws-cdk/aws-codebuild/test/integ.project-vpc.expected.json

@@ -524,7 +524,10 @@
             "Ref": "MyVPCAFB07A31"
           }
         }
-      }
+      },
+      "DependsOn": [
+        "MyProjectPolicyDocument646EE0F2"
+      ]
     }
   },
   "Parameters": {
@@ -541,4 +544,4 @@
       "Description": "Artifact hash for asset \"aws-cdk-codebuild-project-vpc/Bundle\""
     }
   }
-}
+}

packages/@aws-cdk/aws-codebuild/test/test.project.ts

@@ -1,5 +1,7 @@
 import { expect, haveResource, haveResourceLike, not } from '@aws-cdk/assert';
 import assets = require('@aws-cdk/assets');
+import ec2 = require('@aws-cdk/aws-ec2');
+import iam = require('@aws-cdk/aws-iam');
 import { Bucket } from '@aws-cdk/aws-s3';
 import cdk = require('@aws-cdk/cdk');
 import { Test } from 'nodeunit';
@@ -239,4 +241,26 @@ export = {
 
     test.done();
   },
+
+  'can use an imported Role for a Project within a VPC'(test: Test) {
+    const stack = new cdk.Stack();
+
+    const importedRole = iam.Role.fromRoleArn(stack, 'Role', 'arn:aws:iam::1234567890:role/service-role/codebuild-bruiser-service-role');
+    const vpc = new ec2.Vpc(stack, 'Vpc');
+
+    new codebuild.Project(stack, 'Project', {
+      source: new codebuild.GitHubEnterpriseSource({
+        httpsCloneUrl: 'https://mygithub-enterprise.com/myuser/myrepo',
+      }),
+      artifacts: new codebuild.NoBuildArtifacts(),
+      role: importedRole,
+      vpc,
+    });
+
+    expect(stack).to(haveResourceLike('AWS::CodeBuild::Project', {
+      // no need to do any assertions
+    }));
+
+    test.done();
+  },
 };