fix: better handle authentication issues (#42)

- Show a warning message if the account/region is unknown
- Throw an error if the account is for the wrong

Fixes #35

.projenrc.ts

@@ -68,6 +68,7 @@ const project = new GitHubActionTypeScriptProject({
     '@actions/tool-cache@^2.0.0',
     'fs-extra',
     '@aws-sdk/client-cloudformation',
+    '@aws-sdk/client-sts',
     '@smithy/types',
     'chalk@^4',
     '@aws-sdk/credential-providers',

src/assembly.ts

@@ -34,6 +34,13 @@ export interface StackInfo {
    */
   region?: string;
 
+  /**
+   * The account the stack is deployed to
+   *
+   * @default - unknown-account
+   */
+  account?: string;
+
   /**
    * The lookup role to use
    *
@@ -104,13 +111,23 @@ export class AssemblyManifestReader {
       const props = artifact.properties as AwsCloudFormationStackProperties;
       const template = fs.readJSONSync(path.resolve(this.directory, props.templateFile));
       const env = artifact.environment?.split(/\/\/?/);
-      let region = env && env.length === 3 ? env[2] : undefined;
+      const validEnv = env && env.length === 3;
+      let region: string | undefined;
+      let account: string | undefined;
+      if (validEnv) {
+        region = env[2];
+        account = env[1];
+      }
       if (region === 'unknown-region') {
         region = undefined;
       }
+      if (account === 'unknown-account') {
+        account = undefined;
+      }
       stacks.push({
         content: template,
         region,
+        account,
         lookupRole: props.lookupRole,
         name: props.stackName ?? artifactId,
       });

src/diff.ts

@@ -1,5 +1,6 @@
 import { ResourceDifference, ResourceImpact, TemplateDiff, diffTemplate } from '@aws-cdk/cloudformation-diff';
 import { CloudFormationClient, GetTemplateCommand, StackNotFoundException } from '@aws-sdk/client-cloudformation';
+import { STSClient, GetCallerIdentityCommand } from '@aws-sdk/client-sts';
 import { fromTemporaryCredentials } from '@aws-sdk/credential-providers';
 import { AwsCredentialIdentityProvider } from '@smithy/types';
 import { StackInfo } from './assembly';
@@ -27,6 +28,15 @@ export interface ChangeDetails {
    * Information on any destructive changes
    */
   destructiveChanges: DestructiveChange[];
+
+  /**
+   * Whether this stack has an unknown env. If that is the case
+   * then this returns the environment credentials that are being used
+   * in the format aws://<account>/<region>
+   *
+   * @default - account is known
+   */
+  unknownEnvironment?: string;
 }
 
 /**
@@ -75,11 +85,55 @@ export class StackDiff {
     });
   }
 
+  /**
+   * Validates the environment of the stack and whether it matches
+   * the credentials being used by the GitHub action
+   *
+   * There are two cases that we care about:
+   * 1. The stack has an account and region defined _and_ the credentials
+   *   being used by the GitHub action are for a different account and region.
+   *   In this case we throw an error because the stack diff would not be correct
+   * 2. The stack has an account and region that are _not_ defined. In this case
+   *    We will return true to indicate that the environment is unknown. This will be used
+   *    later to print a warning in the stack diff.
+   *
+   * @returns whether or not the environment is unknown
+   */
+  private async validateEnvironment(): Promise<string | undefined> {
+    let unknownAccount = false;
+    let unknownRegion = false;
+    const stsClient = new STSClient({});
+    const callerIdentity = new GetCallerIdentityCommand({ });
+    const identity = await stsClient.send(callerIdentity);
+    const configRegion = await this.client.config.region();
+    if (!this.stack.region) {
+      unknownRegion = true;
+    }
+    if (!this.stack.account) {
+      unknownAccount = true;
+    }
+    if (this.stack.account && identity.Account !== this.stack.account) {
+      throw new Error(`Credentials are for account ${identity.Account} but stack is in account ${this.stack.account}`);
+    }
+
+    if (this.stack.region && configRegion !== this.stack.region) {
+      throw new Error(`Credentials are for region ${configRegion} but stack is in region ${this.stack.region}`);
+    }
+
+    if (unknownAccount || unknownRegion) {
+      return `aws://${identity.Account}/${configRegion}`;
+    }
+
+    return;
+  }
+
   /** Performs the diff on the CloudFormation stack
    * This reads the existing stack from CFN and then uses the cloudformation-diff
    * package to perform the diff and collect additional information on the type of changes
    */
   public async diffStack(): Promise<{ diff: TemplateDiff; changes: ChangeDetails }> {
+    const unknownEnv = await this.validateEnvironment();
+
     const cmd = new GetTemplateCommand({
       StackName: this.stack.name,
     });
@@ -95,6 +149,7 @@ export class StackDiff {
     try {
       const diff = diffTemplate(existingTemplate, this.stack.content);
       const changes = this.evaluateDiff(this.stack.name, diff);
+      changes.unknownEnvironment = unknownEnv;
       return {
         diff,
         changes,

src/stage-processor.ts

@@ -54,6 +54,7 @@ export class StageProcessor {
             prev.stacks.push({
               name: curr.name,
               lookupRole: curr.lookupRole,
+              account: curr.account,
               region: curr.region,
             });
             return prev;
@@ -184,6 +185,12 @@ export class StageProcessor {
       '<details><summary>Details</summary>',
       '',
     ]);
+    if (changes.unknownEnvironment) {
+      output.push('> [!INFO]\n> ***Unknown Environment*** :information_source:');
+      output.push('> This stack has an unknown environment which may mean the diff is performed against the wrong environment');
+      output.push(`> Environmment used ${changes.unknownEnvironment}`);
+      output.push('');
+    }
     if (changes.destructiveChanges.length) {
       output.push('');
       output.push('> [!WARNING]\n> ***Destructive Changes*** :bangbang:'),

test/assembly.test.ts

@@ -96,6 +96,7 @@ describe('cloud assembly manifest reader', () => {
         name: 'test-stack',
         content: { data: 'data' },
         region: 'us-east-1',
+        account: '1234567891012',
         lookupRole: expect.objectContaining({
           arn: lookupRoleArn,
         }),
@@ -109,6 +110,7 @@ describe('cloud assembly manifest reader', () => {
       {
         name: 'SomeStage',
         region: undefined,
+        account: undefined,
         stacks: [{
           name: 'test-stack2',
           content: { data: 'data' },