feat(iam): validate role path at build time (aws#16165)

Role paths can be validated at build time.

According to the [API document](https://docs.aws.amazon.com/IAM/latest/APIReference/API_Role.html), `u007F`, DELETE special char, is valid. However, the creation with a role path `/\u007F/` fails due to validation failure. I don't see any use case for the special char, so I ignored the discrepancy.

closes aws#13747


----

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

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

@@ -355,6 +355,8 @@ export class Role extends Resource implements IRole {
       throw new Error('Role description must be no longer than 1000 characters.');
     }
 
+    validateRolePath(props.path);
+
     const role = new CfnRole(this, 'Resource', {
       assumeRolePolicyDocument: this.assumeRolePolicy as any,
       managedPolicyArns: UniqueStringSet.from(() => this.managedPolicies.map(p => p.managedPolicyArn)),
@@ -468,6 +470,7 @@ export class Role extends Resource implements IRole {
     for (const policy of Object.values(this.inlinePolicies)) {
       errors.push(...policy.validateForIdentityPolicy());
     }
+
     return errors;
   }
 }
@@ -519,6 +522,22 @@ function createAssumeRolePolicy(principal: IPrincipal, externalIds: string[]) {
   return actualDoc;
 }
 
+function validateRolePath(path?: string) {
+  if (path === undefined || Token.isUnresolved(path)) {
+    return;
+  }
+
+  const validRolePath = /^(\/|\/[\u0021-\u007F]+\/)$/;
+
+  if (path.length == 0 || path.length > 512) {
+    throw new Error(`Role path must be between 1 and 512 characters. The provided role path is ${path.length} characters.`);
+  } else if (!validRolePath.test(path)) {
+    throw new Error(
+      'Role path must be either a slash or valid characters (alphanumerics and symbols) surrounded by slashes. '
+      + `Valid characters are unicode characters in [\\u0021-\\u007F]. However, ${path} is provided.`);
+  }
+}
+
 function validateMaxSessionDuration(duration?: number) {
   if (duration === undefined) {
     return;

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

@@ -235,6 +235,72 @@ describe('IAM role', () => {
     });
   });
 
+  test('role path can be used to specify the path', () => {
+    const stack = new Stack();
+
+    new Role(stack, 'MyRole', { path: '/', assumedBy: new ServicePrincipal('sns.amazonaws.com') });
+
+    Template.fromStack(stack).hasResourceProperties('AWS::IAM::Role', {
+      Path: '/',
+    });
+  });
+
+  test('role path can be 1 character', () => {
+    const stack = new Stack();
+
+    const assumedBy = new ServicePrincipal('bla');
+
+    expect(() => new Role(stack, 'MyRole', { assumedBy, path: '/' })).not.toThrowError();
+  });
+
+  test('role path cannot be empty', () => {
+    const stack = new Stack();
+
+    const assumedBy = new ServicePrincipal('bla');
+
+    expect(() => new Role(stack, 'MyRole', { assumedBy, path: '' }))
+      .toThrow('Role path must be between 1 and 512 characters. The provided role path is 0 characters.');
+  });
+
+  test('role path must be less than or equal to 512', () => {
+    const stack = new Stack();
+
+    const assumedBy = new ServicePrincipal('bla');
+
+    expect(() => new Role(stack, 'MyRole', { assumedBy, path: '/' + Array(512).join('a') + '/' }))
+      .toThrow('Role path must be between 1 and 512 characters. The provided role path is 513 characters.');
+  });
+
+  test('role path must start with a forward slash', () => {
+    const stack = new Stack();
+
+    const assumedBy = new ServicePrincipal('bla');
+
+    const expected = (val: any) => 'Role path must be either a slash or valid characters (alphanumerics and symbols) surrounded by slashes. '
+    + `Valid characters are unicode characters in [\\u0021-\\u007F]. However, ${val} is provided.`;
+    expect(() => new Role(stack, 'MyRole', { assumedBy, path: 'aaa' })).toThrow(expected('aaa'));
+  });
+
+  test('role path must end with a forward slash', () => {
+    const stack = new Stack();
+
+    const assumedBy = new ServicePrincipal('bla');
+
+    const expected = (val: any) => 'Role path must be either a slash or valid characters (alphanumerics and symbols) surrounded by slashes. '
+    + `Valid characters are unicode characters in [\\u0021-\\u007F]. However, ${val} is provided.`;
+    expect(() => new Role(stack, 'MyRole', { assumedBy, path: '/a' })).toThrow(expected('/a'));
+  });
+
+  test('role path must contain unicode chars within [\\u0021-\\u007F]', () => {
+    const stack = new Stack();
+
+    const assumedBy = new ServicePrincipal('bla');
+
+    const expected = (val: any) => 'Role path must be either a slash or valid characters (alphanumerics and symbols) surrounded by slashes. '
+    + `Valid characters are unicode characters in [\\u0021-\\u007F]. However, ${val} is provided.`;
+    expect(() => new Role(stack, 'MyRole', { assumedBy, path: '/\u0020\u0080/' })).toThrow(expected('/\u0020\u0080/'));
+  });
+
   describe('maxSessionDuration', () => {
 
     test('is not specified by default', () => {