feat: Refresh and validate credentials after setting env var creds (#71)

* feat: Refresh and validate credentials after setting env var creds

* Positive test case

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

dist/index.js

@@ -265,6 +265,50 @@ async function exportAccountId(maskAccountId, region) {
   return accountId;
 }
 
+function loadCredentials() {
+  // Force the SDK to re-resolve credentials with the default provider chain.
+  //
+  // This action typically sets credentials in the environment via environment variables.
+  // The SDK never refreshes those env-var-based credentials after initial load.
+  // In case there were already env-var creds set in the actions environment when this action
+  // loaded, this action needs to refresh the SDK creds after overwriting those environment variables.
+  //
+  // The credentials object needs to be entirely recreated (instead of simply refreshed),
+  // because the credential object type could change when this action writes env var creds.
+  // For example, the first load could return EC2 instance metadata credentials
+  // in a self-hosted runner, and the second load could return environment credentials
+  // from an assume-role call in this action.
+  aws.config.credentials = null;
+
+  return new Promise((resolve, reject) => {
+    aws.config.getCredentials((err) => {
+      if (err) {
+        reject(err);
+      }
+      resolve(aws.config.credentials);
+    })
+  });
+}
+
+async function validateCredentials(expectedAccessKeyId) {
+  let credentials;
+  try {
+    credentials = await loadCredentials();
+
+    if (!credentials.accessKeyId) {
+      throw new Error('Access key ID empty after loading credentials');
+    }
+  } catch (error) {
+    throw new Error(`Credentials could not be loaded, please check your action inputs: ${error.message}`);
+  }
+
+  const actualAccessKeyId = credentials.accessKeyId;
+
+  if (expectedAccessKeyId && expectedAccessKeyId != actualAccessKeyId) {
+    throw new Error('Unexpected failure: Credentials loaded by the SDK do not match the access key ID configured by the action');
+  }
+}
+
 function getStsClient(region) {
   return new aws.STS({
     region,
@@ -305,6 +349,13 @@ async function run() {
       exportCredentials({accessKeyId, secretAccessKey, sessionToken});
     }
 
+    // Regardless of whether any source credentials were provided as inputs,
+    // validate that the SDK can actually pick up credentials.  This validates
+    // cases where this action is on a self-hosted runner that doesn't have credentials
+    // configured correctly, and cases where the user intended to provide input
+    // credentials but the secrets inputs resolved to empty strings.
+    await validateCredentials(accessKeyId);
+
     const sourceAccountId = await exportAccountId(maskAccountId, region);
 
     // Get role credentials if configured to do so
@@ -318,6 +369,7 @@ async function run() {
         roleSessionName
       });
       exportCredentials(roleCredentials);
+      await validateCredentials(roleCredentials.accessKeyId);
       await exportAccountId(maskAccountId, region);
     }
   }

index.js

@@ -132,6 +132,50 @@ async function exportAccountId(maskAccountId, region) {
   return accountId;
 }
 
+function loadCredentials() {
+  // Force the SDK to re-resolve credentials with the default provider chain.
+  //
+  // This action typically sets credentials in the environment via environment variables.
+  // The SDK never refreshes those env-var-based credentials after initial load.
+  // In case there were already env-var creds set in the actions environment when this action
+  // loaded, this action needs to refresh the SDK creds after overwriting those environment variables.
+  //
+  // The credentials object needs to be entirely recreated (instead of simply refreshed),
+  // because the credential object type could change when this action writes env var creds.
+  // For example, the first load could return EC2 instance metadata credentials
+  // in a self-hosted runner, and the second load could return environment credentials
+  // from an assume-role call in this action.
+  aws.config.credentials = null;
+
+  return new Promise((resolve, reject) => {
+    aws.config.getCredentials((err) => {
+      if (err) {
+        reject(err);
+      }
+      resolve(aws.config.credentials);
+    })
+  });
+}
+
+async function validateCredentials(expectedAccessKeyId) {
+  let credentials;
+  try {
+    credentials = await loadCredentials();
+
+    if (!credentials.accessKeyId) {
+      throw new Error('Access key ID empty after loading credentials');
+    }
+  } catch (error) {
+    throw new Error(`Credentials could not be loaded, please check your action inputs: ${error.message}`);
+  }
+
+  const actualAccessKeyId = credentials.accessKeyId;
+
+  if (expectedAccessKeyId && expectedAccessKeyId != actualAccessKeyId) {
+    throw new Error('Unexpected failure: Credentials loaded by the SDK do not match the access key ID configured by the action');
+  }
+}
+
 function getStsClient(region) {
   return new aws.STS({
     region,
@@ -172,6 +216,13 @@ async function run() {
       exportCredentials({accessKeyId, secretAccessKey, sessionToken});
     }
 
+    // Regardless of whether any source credentials were provided as inputs,
+    // validate that the SDK can actually pick up credentials.  This validates
+    // cases where this action is on a self-hosted runner that doesn't have credentials
+    // configured correctly, and cases where the user intended to provide input
+    // credentials but the secrets inputs resolved to empty strings.
+    await validateCredentials(accessKeyId);
+
     const sourceAccountId = await exportAccountId(maskAccountId, region);
 
     // Get role credentials if configured to do so
@@ -185,6 +236,7 @@ async function run() {
         roleSessionName
       });
       exportCredentials(roleCredentials);
+      await validateCredentials(roleCredentials.accessKeyId);
       await exportAccountId(maskAccountId, region);
     }
   }

index.test.js

@@ -1,6 +1,6 @@
 const core = require('@actions/core');
 const assert = require('assert');
-
+const aws = require('aws-sdk');
 const run = require('.');
 
 jest.mock('@actions/core');
@@ -49,6 +49,9 @@ const mockStsAssumeRole = jest.fn();
 
 jest.mock('aws-sdk', () => {
     return {
+        config: {
+            getCredentials: jest.fn()
+        },
         STS: jest.fn(() => ({
             getCallerIdentity: mockStsCallerIdentity,
             assumeRole: mockStsAssumeRole,
@@ -82,6 +85,27 @@ describe('Configure AWS Credentials', () => {
                 }
             });
 
+        aws.config.getCredentials.mockReset();
+        aws.config.getCredentials
+            .mockImplementationOnce(callback => {
+                if (!aws.config.credentials) {
+                    aws.config.credentials = {
+                        accessKeyId: FAKE_ACCESS_KEY_ID,
+                        secretAccessKey: FAKE_SECRET_ACCESS_KEY
+                    }
+                }
+                callback(null);
+            })
+            .mockImplementationOnce(callback => {
+                if (!aws.config.credentials) {
+                    aws.config.credentials = {
+                        accessKeyId: FAKE_STS_ACCESS_KEY_ID,
+                        secretAccessKey: FAKE_STS_SECRET_ACCESS_KEY
+                    }
+                }
+                callback(null);
+            });
+
         mockStsAssumeRole.mockImplementation(() => {
             return {
                 promise() {
@@ -134,6 +158,59 @@ describe('Configure AWS Credentials', () => {
         expect(core.setSecret).toHaveBeenCalledWith(FAKE_ACCOUNT_ID);
     });
 
+    test('action with no accessible credentials fails', async () => {
+        process.env.SHOW_STACK_TRACE = 'false';
+        const mockInputs = {'aws-region': FAKE_REGION};
+        core.getInput = jest
+            .fn()
+            .mockImplementation(mockGetInput(mockInputs));
+        aws.config.getCredentials.mockReset();
+        aws.config.getCredentials.mockImplementation(callback => {
+            callback(new Error('No credentials to load'));
+        });
+
+        await run();
+
+        expect(core.setFailed).toHaveBeenCalledWith("Credentials could not be loaded, please check your action inputs: No credentials to load");
+    });
+
+    test('action with empty credentials fails', async () => {
+        process.env.SHOW_STACK_TRACE = 'false';
+        const mockInputs = {'aws-region': FAKE_REGION};
+        core.getInput = jest
+            .fn()
+            .mockImplementation(mockGetInput(mockInputs));
+        aws.config.getCredentials.mockReset();
+        aws.config.getCredentials.mockImplementation(callback => {
+            aws.config.credentials = {
+                accessKeyId: ''
+            }
+            callback(null);
+        });
+
+        await run();
+
+        expect(core.setFailed).toHaveBeenCalledWith("Credentials could not be loaded, please check your action inputs: Access key ID empty after loading credentials");
+    });
+
+    test('action fails when credentials are not set in the SDK correctly', async () => {
+        process.env.SHOW_STACK_TRACE = 'false';
+        core.getInput = jest
+            .fn()
+            .mockImplementation(mockGetInput(ASSUME_ROLE_INPUTS));
+        aws.config.getCredentials.mockReset();
+        aws.config.getCredentials.mockImplementation(callback => {
+            aws.config.credentials = {
+                accessKeyId: FAKE_ACCESS_KEY_ID
+            }
+            callback(null);
+        });
+
+        await run();
+
+        expect(core.setFailed).toHaveBeenCalledWith("Unexpected failure: Credentials loaded by the SDK do not match the access key ID configured by the action");
+    });
+
     test('session token is optional', async () => {
         const mockInputs = {...CREDS_INPUTS, 'aws-region': 'eu-west-1'};
         core.getInput = jest
@@ -154,12 +231,19 @@ describe('Configure AWS Credentials', () => {
         expect(core.setSecret).toHaveBeenCalledWith(FAKE_ACCOUNT_ID);
     });
 
-    test('session token is cleared if necessary', async () => {
+    test('existing env var creds are cleared', async () => {
         const mockInputs = {...CREDS_INPUTS, 'aws-region': 'eu-west-1'};
         core.getInput = jest
             .fn()
             .mockImplementation(mockGetInput(mockInputs));
+        process.env.AWS_ACCESS_KEY_ID = 'foo';
+        process.env.AWS_SECRET_ACCESS_KEY = 'bar';
         process.env.AWS_SESSION_TOKEN = 'helloworld';
+        aws.config.credentials = {
+            accessKeyId: 'foo',
+            secretAccessKey: 'bar',
+            sessionToken: 'helloworld'
+        };
 
         await run();
         expect(mockStsAssumeRole).toHaveBeenCalledTimes(0);
@@ -174,6 +258,9 @@ describe('Configure AWS Credentials', () => {
         expect(core.exportVariable).toHaveBeenCalledWith('AWS_REGION', 'eu-west-1');
         expect(core.setOutput).toHaveBeenCalledWith('aws-account-id', FAKE_ACCOUNT_ID);
         expect(core.setSecret).toHaveBeenCalledWith(FAKE_ACCOUNT_ID);
+        expect(aws.config.credentials.accessKeyId).toBe(FAKE_ACCESS_KEY_ID);
+        expect(aws.config.credentials.secretAccessKey).toBe(FAKE_SECRET_ACCESS_KEY);
+        expect(aws.config.credentials.sessionToken).toBeUndefined();
     });
 
     test('validates region name', async () => {