fix(s3): add support for uppercase characters in legacy bucket names (#31813)

### Issue # (if applicable)

Closes #31731

### Reason for this change



As @GavinZZ [commented](#31731 (comment)) in issue #31731, the official AWS S3 documentation stated that uppercase characters were permitted in bucket names prior to March 1, 2018.

### Description of changes


- add support for uppercase characters in legacy bucket names

### Description of how you validated changes



- added new unit test cases and updated the integration test cases with legacy bucket names

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: 5d

packages/@aws-cdk-testing/framework-integ/test/aws-s3/test/integ.bucket-legacy-naming.js.snapshot/aws-cdk-s3-legacy-name-integ.assets.json

@@ -26,7 +26,7 @@
        "Action": "s3:*",
        "Effect": "Allow",
        "Resource": [
-        "arn:aws:s3:::my_legacy_bucket2/*",
+        "arn:aws:s3:::My_legacy_bucket2/*",
         {
          "Fn::Join": [
           "",
@@ -35,7 +35,7 @@
            {
             "Ref": "AWS::Partition"
            },
-           ":s3:::my_legacy_bucket1/*"
+           ":s3:::My_legacy_bucket1/*"
           ]
          ]
         },
@@ -47,7 +47,7 @@
            {
             "Ref": "AWS::Partition"
            },
-           ":s3:::my_legacy_bucket3/*"
+           ":s3:::My_legacy_bucket3/*"
           ]
          ]
         }

packages/@aws-cdk-testing/framework-integ/test/aws-s3/test/integ.bucket-legacy-naming.js.snapshot/aws-cdk-s3-legacy-name-integ.template.json

@@ -7,12 +7,12 @@ import * as iam from 'aws-cdk-lib/aws-iam';
 const app = new cdk.App();
 const stack = new cdk.Stack(app, 'aws-cdk-s3-legacy-name-integ');
 
-const legacyBucketFromName = s3.Bucket.fromBucketName(stack, 'LegacyBucketFromName', 'my_legacy_bucket1');
+const legacyBucketFromName = s3.Bucket.fromBucketName(stack, 'LegacyBucketFromName', 'My_legacy_bucket1');
 
-const legacyBucketFromArn = s3.Bucket.fromBucketArn(stack, 'LegacyBucketFromArn', 'arn:aws:s3:::my_legacy_bucket2');
+const legacyBucketFromArn = s3.Bucket.fromBucketArn(stack, 'LegacyBucketFromArn', 'arn:aws:s3:::My_legacy_bucket2');
 
 const legacyBucketFromAttributes = s3.Bucket.fromBucketAttributes(stack, 'LegacyBucketFromAttributes', {
-  bucketName: 'my_legacy_bucket3',
+  bucketName: 'My_legacy_bucket3',
 });
 
 const role = new iam.Role(stack, 'LegacyBucketRole', {
@@ -37,4 +37,3 @@ new IntegTest(app, 'aws-cdk-s3-integ-test', {
 // In the synthesized template, verify:
 // 1. The bucket names imported using different methods (Bucket.fromBucketName, Bucket.fromBucketArn, Bucket.fromBucketAttributes) are not modified and contain underscores.
 // 2. The policy attached to the role includes the correct bucket ARNs with underscores for all three imported buckets.
-

packages/@aws-cdk-testing/framework-integ/test/aws-s3/test/integ.bucket-legacy-naming.js.snapshot/awscdks3integtestDefaultTestDeployAssert9DECDFBF.assets.json

@@ -1897,24 +1897,37 @@ export class Bucket extends BucketBase {
     if (bucketName.length < 3 || bucketName.length > 63) {
       errors.push('Bucket name must be at least 3 and no more than 63 characters');
     }
-    const charsetRegex = allowLegacyBucketNaming ? /[^a-z0-9._-]/ : /[^a-z0-9.-]/;
-    const charsetMatch = bucketName.match(charsetRegex);
-    if (charsetMatch) {
-      errors.push(`Bucket name must only contain lowercase characters and the symbols, period (.)${allowLegacyBucketNaming ? ', underscore (_), ' : ' '}and dash (-) `
-        + `(offset: ${charsetMatch.index})`);
+
+    const illegalCharsetRegEx = allowLegacyBucketNaming ? /[^A-Za-z0-9._-]/ : /[^a-z0-9.-]/;
+    const allowedEdgeCharsetRegEx = allowLegacyBucketNaming ? /[A-Za-z0-9]/ : /[a-z0-9]/;
+
+    const illegalCharMatch = bucketName.match(illegalCharsetRegEx);
+    if (illegalCharMatch) {
+      errors.push(allowLegacyBucketNaming
+        ? 'Bucket name must only contain uppercase or lowercase characters and the symbols, period (.), underscore (_), and dash (-)'
+        : 'Bucket name must only contain lowercase characters and the symbols, period (.) and dash (-)'
+        + ` (offset: ${illegalCharMatch.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 (!allowedEdgeCharsetRegEx.test(bucketName.charAt(0))) {
+      errors.push(allowLegacyBucketNaming
+        ? 'Bucket name must start with an uppercase, lowercase character or number'
+        : 'Bucket name must start 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})`);
+    if (!allowedEdgeCharsetRegEx.test(bucketName.charAt(bucketName.length - 1))) {
+      errors.push(allowLegacyBucketNaming
+        ? 'Bucket name must end with an uppercase, lowercase character or number'
+        : 'Bucket name must 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})`);
+      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');

packages/@aws-cdk-testing/framework-integ/test/aws-s3/test/integ.bucket-legacy-naming.js.snapshot/cdk.out

@@ -193,8 +193,8 @@ describe('bucket', () => {
       `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 start with a lowercase character or number (offset: 0)',
+      `Bucket name must 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);
 
@@ -215,12 +215,30 @@ describe('bucket', () => {
     }).toThrow(/Bucket name must only contain lowercase characters and the symbols, period \(\.\) and dash \(-\)/);
   });
 
+  test('validateBucketName allows uppercase characters when allowLegacyBucketNaming=true', () => {
+    expect(() => {
+      s3.Bucket.validateBucketName('Test_Bucket_Name', true);
+    }).not.toThrow();
+  });
+
+  test('validateBucketName does not allow uppercase characters when allowLegacyBucketNaming=false', () => {
+    expect(() => {
+      s3.Bucket.validateBucketName('Test_Bucket_Name', false);
+    }).toThrow(/Bucket name must only contain lowercase characters and the symbols, period \(\.\) and dash \(-\)/);
+  });
+
   test('validateBucketName does not allow underscore by default', () => {
     expect(() => {
       s3.Bucket.validateBucketName('test_bucket_name');
     }).toThrow(/Bucket name must only contain lowercase characters and the symbols, period \(\.\) and dash \(-\)/);
   });
 
+  test('validateBucketName does not allow uppercase characters by default', () => {
+    expect(() => {
+      s3.Bucket.validateBucketName('TestBucketName');
+    }).toThrow(/Bucket name must only contain lowercase characters and the symbols, period \(\.\) and dash \(-\)/);
+  });
+
   test('fails if bucket name has less than 3 or more than 63 characters', () => {
     const stack = new cdk.Stack();
 
@@ -3877,4 +3895,3 @@ describe('bucket', () => {
     });
   });
 });
-