feat: add EKS pod identity credentials support (#252)

Uses the `AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE` environment variable to provide support for EKS pod identity credentials. Ref: https://docs.aws.amazon.com/eks/latest/userguide/pod-identities.html
---------

Co-authored-by: Javier Evans <[email protected]>

Author: tieum

common/etc/nginx/include/awscredentials.js

@@ -58,6 +58,12 @@ const EC2_IMDS_TOKEN_ENDPOINT = 'http://169.254.169.254/latest/api/token';
  */
 const EC2_IMDS_SECURITY_CREDENTIALS_ENDPOINT = 'http://169.254.169.254/latest/meta-data/iam/security-credentials/';
 
+/**
+ * URL to EKS Pod Identity Agent credentials endpoint
+ * @type {string}
+ */
+const EKS_POD_IDENTITY_AGENT_CREDENTIALS_ENDPOINT = 'http://169.254.170.23/v1/credentials'
+
 /**
  * Offset to the expiration of credentials, when they should be considered expired and refreshed. The maximum
  * time here can be 5 minutes, the IMDS and ECS credentials endpoint will make sure that each returned set of credentials
@@ -293,6 +299,15 @@ async function fetchCredentials(r) {
             r.return(500);
             return;
         }
+    } 
+    else if (utils.areAllEnvVarsSet('AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE')) {
+        try {
+            credentials = await _fetchEKSPodIdentityCredentials(r)
+        } catch (e) {
+            utils.debug_log(r, 'Could not assume role using EKS pod identity: ' + JSON.stringify(e));
+            r.return(500);
+            return;
+        }
     } else {
         try {
             credentials = await _fetchEC2RoleCredentials();
@@ -378,6 +393,29 @@ async function _fetchEC2RoleCredentials() {
     };
 }
 
+/**
+ * Get the credentials needed to generate AWS signatures from the EKS Pod Identity Agent
+ * endpoint.
+ *
+ * @returns {Promise<Credentials>}
+ * @private
+ */
+async function _fetchEKSPodIdentityCredentials() {
+    const token = fs.readFileSync(process.env['AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE']);
+    let resp = await ngx.fetch(EKS_POD_IDENTITY_AGENT_CREDENTIALS_ENDPOINT, {
+        headers: {
+            'Authorization': token,
+        },
+    });
+    const creds = await resp.json();
+
+    return {
+        accessKeyId: creds.AccessKeyId,
+        secretAccessKey: creds.SecretAccessKey,
+        sessionToken: creds.Token,
+        expiration: creds.Expiration,
+    };
+}
 /**
  * Get the credentials by assuming calling AssumeRoleWithWebIdentity with the environment variable
  * values ROLE_ARN, AWS_WEB_IDENTITY_TOKEN_FILE and AWS_ROLE_SESSION_NAME

docs/getting_started.md

@@ -6,6 +6,8 @@
 [Running as a Systemd Service](#running-as-a-systemd-service)  
 [Running in Containers](#running-in-containers)  
 [Running Using AWS Instance Profile Credentials](#running-using-aws-instance-profile-credentials)  
+[Running on EKS with IAM roles for service accounts](#running-on-eks-with-iam-roles-for-service-accounts)  
+[Running on EKS with EKS Pod Identities](#running-on-eks-with-eks-pod-identities)  
 [Troubleshooting](#troubleshooting)  
 
 ## Configuration
@@ -470,6 +472,23 @@ spec:
               path: /health
               port: http
 ```
+## Running on EKS with EKS Pod Identities
+
+An alternative way to use the container image on an EKS cluster is to use a service account which can assume a role using [Pod Identities](https://docs.aws.amazon.com/eks/latest/userguide/pod-identities.html).
+- Installing the [Amazon EKS Pod Identity Agent](https://docs.aws.amazon.com/eks/latest/userguide/pod-id-agent-setup.html) on the cluster
+- Configuring a [Kubernetes service account to assume an IAM role with EKS Pod Identity](https://docs.aws.amazon.com/eks/latest/userguide/pod-id-association.html)
+- [Configure your pods, Deployments, etc to use the Service Account](https://docs.aws.amazon.com/eks/latest/userguide/pod-configuration.html)
+- As soon as the pods/deployments are updated, you will see the couple of Env Variables listed below in the pods.
+  - `AWS_CONTAINER_CREDENTIALS_FULL_URI` - Contains the Uri of the EKS Pod Identity Agent that will provide the credentials 
+  - `AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE`  - Contains the token which will be used to create temporary credentials using the EKS Pod Identity Agent.
+
+The minimal set of resources to deploy is the same than for [Running on EKS with IAM roles for service accounts](#running-on-eks-with-iam-roles-for-service-accounts), except there is no need to annotate the service account:
+```yaml
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: nginx-s3-gateway
+```
 
 ## Troubleshooting
 

test/unit/awscredentials_test.js

@@ -234,7 +234,7 @@ async function testEc2CredentialRetrieval() {
         delete process.env['AWS_ACCESS_KEY_ID'];
     }
     if ('AWS_CONTAINER_CREDENTIALS_RELATIVE_URI' in process.env) {
-        delete process.env['AWS_CONTAINER_CREDENTIALS_RELATIVE_URI'];    
+        delete process.env['AWS_CONTAINER_CREDENTIALS_RELATIVE_URI'];
     }
     globalThis.ngx.fetch = function (url, options) {
         if (url === 'http://169.254.169.254/latest/api/token' && options && options.method === 'PUT') {
@@ -300,13 +300,82 @@ async function testEc2CredentialRetrieval() {
     await awscred.fetchCredentials(r);
 
     if (!globalThis.credentialsIssued) {
-        throw 'Did not reach the point where EC2 credentials were issues.';
+        throw 'Did not reach the point where EC2 credentials were issued.';
+    }
+}
+
+async function testEKSPodIdentityCredentialRetrieval() {
+    printHeader('testEKSPodIdentityCredentialRetrieval');
+    if ('AWS_ACCESS_KEY_ID' in process.env) {
+        delete process.env['AWS_ACCESS_KEY_ID'];
+    }
+    if ('AWS_CONTAINER_CREDENTIALS_RELATIVE_URI' in process.env) {
+        delete process.env['AWS_CONTAINER_CREDENTIALS_RELATIVE_URI'];
+    }
+    if ('AWS_WEB_IDENTITY_TOKEN_FILE' in process.env) {
+        delete process.env['AWS_WEB_IDENTITY_TOKEN_FILE'];
+    }
+    var tempDir = (process.env['TMPDIR'] ? process.env['TMPDIR'] : '/tmp');
+    var uniqId = `${new Date().getTime()}-${Math.floor(Math.random()*101)}`;
+    var tempFile = `${tempDir}/credentials-unit-test-${uniqId}.json`;
+    var testToken = 'A_TOKEN';
+    fs.writeFileSync(tempFile, testToken);
+    process.env['AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE'] = tempFile;
+    globalThis.ngx.fetch = function(url, options) {
+        console.log(' fetching eks pod identity mock credentials');
+        if (url === 'http://169.254.170.23/v1/credentials') {
+            if (options && options.headers && options.headers['Authorization'].toString() === testToken) {
+                return Promise.resolve({
+                    ok: true,
+                    json: function() {
+                        globalThis.credentialsIssued = true;
+                        return Promise.resolve({
+                            AccessKeyId: 'AN_ACCESS_KEY_ID',
+                            Expiration: '2017-05-17T15:09:54Z',
+                            AccountId: 'AN_ACCOUNT_ID',
+                            SecretAccessKey: 'A_SECRET_ACCESS_KEY',
+                            Token: 'A_SECURITY_TOKEN',
+                        });
+                    },
+                });
+            } else {
+                throw 'Invalid token passed: ' + options.headers['Authorization'];
+            }
+        } else {
+            throw 'Invalid request URL: ' + url;
+        }
+    };
+    var r = {
+        "headersOut": {
+            "Accept-Ranges": "bytes",
+            "Content-Length": 42,
+            "Content-Security-Policy": "block-all-mixed-content",
+            "Content-Type": "text/plain",
+            "X-Amz-Bucket-Region": "us-east-1",
+            "X-Amz-Request-Id": "166539E18A46500A",
+            "X-Xss-Protection": "1; mode=block"
+        },
+        log: function(msg) {
+            console.log(msg);
+        },
+        return: function(code) {
+            if (code !== 200) {
+                throw 'Expected 200 status code, got: ' + code;
+            }
+        },
+    };
+
+    await awscred.fetchCredentials(r);
+
+    if (!globalThis.credentialsIssued) {
+        throw 'Did not reach the point where EKS Pod Identity credentials were issued.';
     }
 }
 
 async function test() {
     await testEc2CredentialRetrieval();
     await testEcsCredentialRetrieval();
+    await testEKSPodIdentityCredentialRetrieval();
     testReadCredentialsWithAccessSecretKeyAndSessionTokenSet();
     testReadCredentialsFromFilePath();
     testReadCredentialsFromNonexistentPath();