Allow provider to use the external ID when assuming the role in the p… (

#357)

* Allow provider to use the external ID when assuming the role in the provider configuration set up

* Update the provider documentation

* copy pasta no good

---------

Co-authored-by: mannai2 <haythem.mannai@aircall.io>

docs/index.md

@@ -63,6 +63,7 @@ The following arguments are supported:
 * `username` (Optional) - Username to use to connect to elasticsearch using basic auth. Defaults to `ELASTICSEARCH_USERNAME` from the environment
 * `password` (Optional) - Password to use to connect to elasticsearch using basic auth. Defaults to `ELASTICSEARCH_PASSWORD` from the environment
 * `aws_assume_role_arn` (Optional) - ARN of role to assume when using AWS Elasticsearch Service domains.
+* `aws_assume_role_external_id` (Optional) - External ID configured in the IAM policy of the IAM Role to assume prior to using AWS Elasticsearch Service domains.
 * `aws_assume_role_session_name` - AWS IAM session name to use when assuming a role.
 * `aws_access_key` (Optional) - The access key for use with AWS Elasticsearch Service domains. It can also be sourced from the `AWS_ACCESS_KEY_ID` environment variable.
 * `aws_secret_key` (Optional) - The secret key for use with AWS Elasticsearch Service domains. It can also be sourced from the `AWS_SECRET_ACCESS_KEY` environment variable.
@@ -109,13 +110,15 @@ provider "elasticsearch" {
 #### Assume role configuration
 
 You can instruct the provider to assume a role in AWS before interacting with the cluster by setting the `aws_assume_role_arn` variable.
+Optionnaly, you can configure the [External ID](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_create_for-user_externalid.html) of IAM role trust policy by setting the `aws_assume_role_external_id` variable.
 
 Example usage:
 
 ```tf
 provider "elasticsearch" {
-    url                 = "https://search-foo-bar-pqrhr4w3u4dzervg41frow4mmy.us-east-1.es.amazonaws.com"
-    aws_assume_role_arn = "arn:aws:iam::012345678901:role/rolename"
+    url                         = "https://search-foo-bar-pqrhr4w3u4dzervg41frow4mmy.us-east-1.es.amazonaws.com"
+    aws_assume_role_arn         = "arn:aws:iam::012345678901:role/rolename"
+    aws_assume_role_external_id = "Unique ID"
 }
 ```
 

es/provider.go

@@ -57,6 +57,7 @@ type ProviderConf struct {
 	pingTimeoutSeconds       int
 	awsRegion                string
 	awsAssumeRoleArn         string
+	awsAssumeRoleExternalID  string
 	awsAssumeRoleSessionName string
 	awsAccessKeyId           string
 	awsSecretAccessKey       string
@@ -128,6 +129,12 @@ func Provider() *schema.Provider {
 				Default:     "",
 				Description: "Amazon Resource Name of an IAM Role to assume prior to making AWS API calls.",
 			},
+			"aws_assume_role_external_id": {
+				Type:        schema.TypeString,
+				Optional:    true,
+				Default:     "",
+				Description: "External ID configured in the IAM policy of the IAM Role to assume prior to making AWS API calls.",
+			},
 			"aws_assume_role_session_name": {
 				Type:        schema.TypeString,
 				Optional:    true,
@@ -299,6 +306,7 @@ func providerConfigure(c context.Context, d *schema.ResourceData) (interface{},
 		awsRegion:          d.Get("aws_region").(string),
 
 		awsAssumeRoleArn:         d.Get("aws_assume_role_arn").(string),
+		awsAssumeRoleExternalID:  d.Get("aws_assume_role_external_id").(string),
 		awsAssumeRoleSessionName: d.Get("aws_assume_role_session_name").(string),
 		awsAccessKeyId:           d.Get("aws_access_key").(string),
 		awsSecretAccessKey:       d.Get("aws_secret_key").(string),
@@ -553,7 +561,7 @@ func getKibanaClient(conf *ProviderConf) (interface{}, error) {
 	}
 }
 
-func assumeRoleCredentials(region, roleARN, roleSessionName, profile string) *awscredentials.Credentials {
+func assumeRoleCredentials(region, roleARN, roleExternalID, roleSessionName, profile string) *awscredentials.Credentials {
 	sessOpts := awsSessionOptions(region)
 	sessOpts.Profile = profile
 
@@ -563,6 +571,7 @@ func assumeRoleCredentials(region, roleARN, roleSessionName, profile string) *aw
 		Client:          stsClient,
 		RoleARN:         roleARN,
 		RoleSessionName: roleSessionName,
+		ExternalID:      aws.String(roleExternalID),
 	}
 
 	return awscredentials.NewChainCredentials([]awscredentials.Provider{assumeRoleProvider})
@@ -593,14 +602,18 @@ func awsSession(region string, conf *ProviderConf) *awssession.Session {
 
 	// 1. access keys take priority
 	// 2. next is an assume role configuration
+	// 2.b check if the role external ID is set and use it
 	// 3. followed by a profile (for assume role)
 	// 4. let the default credentials provider figure out the rest (env, ec2, etc..)
 	//
 	// note: if #1 is chosen, then no further providers will be tested, since we've overridden the credentials with just a static provider
 	if conf.awsAccessKeyId != "" {
 		sessOpts.Config.Credentials = awscredentials.NewStaticCredentials(conf.awsAccessKeyId, conf.awsSecretAccessKey, conf.awsSessionToken)
 	} else if conf.awsAssumeRoleArn != "" {
-		sessOpts.Config.Credentials = assumeRoleCredentials(region, conf.awsAssumeRoleArn, conf.awsAssumeRoleSessionName, conf.awsProfile)
+		if conf.awsAssumeRoleExternalID == "" {
+			conf.awsAssumeRoleExternalID = ""
+		}
+		sessOpts.Config.Credentials = assumeRoleCredentials(region, conf.awsAssumeRoleArn, conf.awsAssumeRoleExternalID, conf.awsAssumeRoleSessionName, conf.awsProfile)
 	} else if conf.awsProfile != "" {
 		sessOpts.Profile = conf.awsProfile
 	}

es/provider_test.go

@@ -216,13 +216,15 @@ func TestAWSCredsAssumeRole(t *testing.T) {
 	testRegion := "us-east-1"
 
 	testConfig := map[string]interface{}{
-		"aws_assume_role_arn": "test_arn",
+		"aws_assume_role_arn":         "test_arn",
+		"aws_assume_role_external_id": "secret_id",
 	}
 
 	testConfigData := schema.TestResourceDataRaw(t, Provider().Schema, testConfig)
 
 	conf := &ProviderConf{
-		awsAssumeRoleArn: testConfigData.Get("aws_assume_role_arn").(string),
+		awsAssumeRoleArn:        testConfigData.Get("aws_assume_role_arn").(string),
+		awsAssumeRoleExternalID: testConfigData.Get("aws_assume_role_external_id").(string),
 	}
 	s := awsSession(testRegion, conf)
 	if s == nil {