fix(s3): Add validations for S3 bucket names (#2256)

Bucket names are verified to conform with rules published by S3 -
https://docs.aws.amazon.com/AmazonS3/latest/dev/BucketRestrictions.html

Fixes #1308

Author: nija-at

packages/@aws-cdk/aws-s3/lib/bucket.ts

@@ -3,6 +3,7 @@ import iam = require('@aws-cdk/aws-iam');
 import kms = require('@aws-cdk/aws-kms');
 import { IBucketNotificationDestination } from '@aws-cdk/aws-s3-notifications';
 import cdk = require('@aws-cdk/cdk');
+import { EOL } from 'os';
 import { BucketPolicy } from './bucket-policy';
 import { BucketNotifications } from './notifications-resource';
 import perms = require('./perms');
@@ -669,6 +670,9 @@ export class Bucket extends BucketBase {
     super(scope, id);
 
     const { bucketEncryption, encryptionKey } = this.parseEncryption(props);
+    if (props.bucketName && !cdk.Token.unresolved(props.bucketName)) {
+      this.validateBucketName(props.bucketName);
+    }
 
     const resource = new CfnBucket(this, 'Resource', {
       bucketName: props && props.bucketName,
@@ -776,6 +780,40 @@ export class Bucket extends BucketBase {
     return this.onEvent(EventType.ObjectRemoved, dest, ...filters);
   }
 
+  private validateBucketName(bucketName: string) {
+    const errors: string[] = [];
+
+    // Rules codified from https://docs.aws.amazon.com/AmazonS3/latest/dev/BucketRestrictions.html
+    if (bucketName.length < 3 || bucketName.length > 63) {
+      errors.push('Bucket name must be at least 3 and no more than 63 characters');
+    }
+    const charsetMatch = bucketName.match(/[^a-z0-9.-]/);
+    if (charsetMatch) {
+      errors.push('Bucket name must only contain lowercase characters and the symbols, period (.) and dash (-) '
+        + `(offset: ${charsetMatch.index})`);
+    }
+    if (!/[a-z0-9]/.test(bucketName.charAt(0))) {
+      errors.push('Bucket name must start and end with a lowercase character or number '
+        + '(offset: 0)');
+    }
+    if (!/[a-z0-9]/.test(bucketName.charAt(bucketName.length - 1))) {
+      errors.push('Bucket name must start and end with a lowercase character or number '
+        + `(offset: ${bucketName.length - 1})`);
+    }
+    const consecSymbolMatch = bucketName.match(/\.-|-\.|\.\./);
+    if (consecSymbolMatch) {
+      errors.push('Bucket name must not have dash next to period, or period next to dash, or consecutive periods '
+        + `(offset: ${consecSymbolMatch.index})`);
+    }
+    if (/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/.test(bucketName)) {
+      errors.push('Bucket name must not resemble an IP address');
+    }
+
+    if (errors.length > 0) {
+      throw new Error(`Invalid S3 bucket name (value: ${bucketName})${EOL}${errors.join(EOL)}`);
+    }
+  }
+
   /**
    * Set up key properties and return the Bucket encryption property from the
    * user's configuration.

packages/@aws-cdk/aws-s3/test/test.bucket.ts

@@ -3,6 +3,7 @@ import iam = require('@aws-cdk/aws-iam');
 import kms = require('@aws-cdk/aws-kms');
 import cdk = require('@aws-cdk/cdk');
 import { Test } from 'nodeunit';
+import { EOL } from 'os';
 import s3 = require('../lib');
 
 // to make it easy to copy & paste from output:
@@ -72,6 +73,142 @@ export = {
     test.done();
   },
 
+  'valid bucket names'(test: Test) {
+    const stack = new cdk.Stack();
+
+    test.doesNotThrow(() => new s3.Bucket(stack, 'MyBucket1', {
+      bucketName: 'abc.xyz-34ab'
+    }));
+
+    test.doesNotThrow(() => new s3.Bucket(stack, 'MyBucket2', {
+      bucketName: '124.pp--33'
+    }));
+
+    test.done();
+  },
+
+  'bucket validation skips tokenized values'(test: Test) {
+    const stack = new cdk.Stack();
+
+    test.doesNotThrow(() => new s3.Bucket(stack, 'MyBucket', {
+      bucketName: new cdk.Token(() => '_BUCKET').toString()
+    }));
+
+    test.done();
+  },
+
+  'fails with message on invalid bucket names'(test: Test) {
+    const stack = new cdk.Stack();
+    const bucket = `-buckEt.-${new Array(65).join('$')}`;
+    const expectedErrors = [
+      `Invalid S3 bucket name (value: ${bucket})`,
+      'Bucket name must be at least 3 and no more than 63 characters',
+      'Bucket name must only contain lowercase characters and the symbols, period (.) and dash (-) (offset: 5)',
+      'Bucket name must start and end with a lowercase character or number (offset: 0)',
+      `Bucket name must start and end with a lowercase character or number (offset: ${bucket.length - 1})`,
+      'Bucket name must not have dash next to period, or period next to dash, or consecutive periods (offset: 7)',
+    ].join(EOL);
+
+    test.throws(() => new s3.Bucket(stack, 'MyBucket', {
+      bucketName: bucket
+    // tslint:disable-next-line:only-arrow-functions
+    }), function(err: Error) {
+      return expectedErrors === err.message;
+    });
+
+    test.done();
+  },
+
+  'fails if bucket name has less than 3 or more than 63 characters'(test: Test) {
+    const stack = new cdk.Stack();
+
+    test.throws(() => new s3.Bucket(stack, 'MyBucket1', {
+      bucketName: 'a'
+    }), /at least 3/);
+
+    test.throws(() => new s3.Bucket(stack, 'MyBucket2', {
+      bucketName: new Array(65).join('x')
+    }), /no more than 63/);
+
+    test.done();
+  },
+
+  'fails if bucket name has invalid characters'(test: Test) {
+    const stack = new cdk.Stack();
+
+    test.throws(() => new s3.Bucket(stack, 'MyBucket1', {
+      bucketName: 'b@cket'
+    }), /offset: 1/);
+
+    test.throws(() => new s3.Bucket(stack, 'MyBucket2', {
+      bucketName: 'bucKet'
+    }), /offset: 3/);
+
+    test.throws(() => new s3.Bucket(stack, 'MyBucket3', {
+      bucketName: 'bučket'
+    }), /offset: 2/);
+
+    test.done();
+  },
+
+  'fails if bucket name does not start or end with lowercase character or number'(test: Test) {
+    const stack = new cdk.Stack();
+
+    test.throws(() => new s3.Bucket(stack, 'MyBucket1', {
+      bucketName: '-ucket'
+    }), /offset: 0/);
+
+    test.throws(() => new s3.Bucket(stack, 'MyBucket2', {
+      bucketName: 'bucke.'
+    }), /offset: 5/);
+
+    test.done();
+  },
+
+  'fails only if bucket name has the consecutive symbols (..), (.-), (-.)'(test: Test) {
+    const stack = new cdk.Stack();
+
+    test.throws(() => new s3.Bucket(stack, 'MyBucket1', {
+      bucketName: 'buc..ket'
+    }), /offset: 3/);
+
+    test.throws(() => new s3.Bucket(stack, 'MyBucket2', {
+      bucketName: 'buck.-et'
+    }), /offset: 4/);
+
+    test.throws(() => new s3.Bucket(stack, 'MyBucket3', {
+      bucketName: 'b-.ucket'
+    }), /offset: 1/);
+
+    test.doesNotThrow(() => new s3.Bucket(stack, 'MyBucket4', {
+      bucketName: 'bu--cket'
+    }));
+
+    test.done();
+  },
+
+  'fails only if bucket name resembles IP address'(test: Test) {
+    const stack = new cdk.Stack();
+
+    test.throws(() => new s3.Bucket(stack, 'MyBucket1', {
+      bucketName: '1.2.3.4'
+    }), /must not resemble an IP address/);
+
+    test.doesNotThrow(() => new s3.Bucket(stack, 'MyBucket2', {
+      bucketName: '1.2.3'
+    }));
+
+    test.doesNotThrow(() => new s3.Bucket(stack, 'MyBucket3', {
+      bucketName: '1.2.3.a'
+    }));
+
+    test.doesNotThrow(() => new s3.Bucket(stack, 'MyBucket4', {
+      bucketName: '1000.2.3.4'
+    }));
+
+    test.done();
+  },
+
   'fails if encryption key is used with managed encryption'(test: Test) {
     const stack = new cdk.Stack();
     const myKey = new kms.EncryptionKey(stack, 'MyKey');