aws: Discover supported EC2 platforms (#7568)

This will make it possible/easier to make decisions based on supported EC2 platforms (VPC and/or EC2 Classic)
in the context of any AWS resource which needs make such decisions.

builtin/providers/aws/config.go

@@ -136,6 +136,7 @@ type AWSClient struct {
 	r53conn               *route53.Route53
 	partition             string
 	accountid             string
+	supportedplatforms    []string
 	region                string
 	rdsconn               *rds.RDS
 	iamconn               *iam.IAM
@@ -272,6 +273,17 @@ func (c *Config) Client() (interface{}, error) {
 		return nil, authErr
 	}
 
+	client.ec2conn = ec2.New(awsEc2Sess)
+
+	supportedPlatforms, err := GetSupportedEC2Platforms(client.ec2conn)
+	if err != nil {
+		// We intentionally fail *silently* because there's a chance
+		// user just doesn't have ec2:DescribeAccountAttributes permissions
+		log.Printf("[WARN] Unable to get supported EC2 platforms: %s", err)
+	} else {
+		client.supportedplatforms = supportedPlatforms
+	}
+
 	client.acmconn = acm.New(sess)
 	client.apigateway = apigateway.New(sess)
 	client.appautoscalingconn = applicationautoscaling.New(sess)
@@ -290,7 +302,6 @@ func (c *Config) Client() (interface{}, error) {
 	client.codepipelineconn = codepipeline.New(sess)
 	client.dsconn = directoryservice.New(sess)
 	client.dynamodbconn = dynamodb.New(dynamoSess)
-	client.ec2conn = ec2.New(awsEc2Sess)
 	client.ecrconn = ecr.New(sess)
 	client.ecsconn = ecs.New(sess)
 	client.efsconn = efs.New(sess)
@@ -389,6 +400,34 @@ func (c *Config) ValidateAccountId(accountId string) error {
 	return nil
 }
 
+func GetSupportedEC2Platforms(conn *ec2.EC2) ([]string, error) {
+	attrName := "supported-platforms"
+
+	input := ec2.DescribeAccountAttributesInput{
+		AttributeNames: []*string{aws.String(attrName)},
+	}
+	attributes, err := conn.DescribeAccountAttributes(&input)
+	if err != nil {
+		return nil, err
+	}
+
+	var platforms []string
+	for _, attr := range attributes.AccountAttributes {
+		if *attr.AttributeName == attrName {
+			for _, v := range attr.AttributeValues {
+				platforms = append(platforms, *v.AttributeValue)
+			}
+			break
+		}
+	}
+
+	if len(platforms) == 0 {
+		return nil, fmt.Errorf("No EC2 platforms detected")
+	}
+
+	return platforms, nil
+}
+
 // addTerraformVersionToUserAgent is a named handler that will add Terraform's
 // version information to requests made by the AWS SDK.
 var addTerraformVersionToUserAgent = request.NamedHandler{

builtin/providers/aws/config_test.go

@@ -6,13 +6,41 @@ import (
 	"log"
 	"net/http"
 	"net/http/httptest"
+	"reflect"
+	"testing"
 	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
 	awsCredentials "github.com/aws/aws-sdk-go/aws/credentials"
 	"github.com/aws/aws-sdk-go/aws/session"
+	"github.com/aws/aws-sdk-go/service/ec2"
 )
 
+func TestGetSupportedEC2Platforms(t *testing.T) {
+	ec2Endpoints := []*awsMockEndpoint{
+		&awsMockEndpoint{
+			Request: &awsMockRequest{"POST", "/", "Action=DescribeAccountAttributes&" +
+				"AttributeName.1=supported-platforms&Version=2016-11-15"},
+			Response: &awsMockResponse{200, test_ec2_describeAccountAttributes_response, "text/xml"},
+		},
+	}
+	closeFunc, sess, err := getMockedAwsApiSession("EC2", ec2Endpoints)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer closeFunc()
+	conn := ec2.New(sess)
+
+	platforms, err := GetSupportedEC2Platforms(conn)
+	if err != nil {
+		t.Fatalf("Expected no error, received: %s", err)
+	}
+	expectedPlatforms := []string{"VPC", "EC2"}
+	if !reflect.DeepEqual(platforms, expectedPlatforms) {
+		t.Fatalf("Received platforms: %q\nExpected: %q\n", platforms, expectedPlatforms)
+	}
+}
+
 // getMockedAwsApiSession establishes a httptest server to simulate behaviour
 // of a real AWS API server
 func getMockedAwsApiSession(svcName string, endpoints []*awsMockEndpoint) (func(), *session.Session, error) {
@@ -71,3 +99,20 @@ type awsMockResponse struct {
 	Body        string
 	ContentType string
 }
+
+var test_ec2_describeAccountAttributes_response = `<DescribeAccountAttributesResponse xmlns="http://ec2.amazonaws.com/doc/2016-11-15/">
+  <requestId>7a62c49f-347e-4fc4-9331-6e8eEXAMPLE</requestId>
+  <accountAttributeSet>
+    <item>
+      <attributeName>supported-platforms</attributeName>
+      <attributeValueSet>
+        <item>
+          <attributeValue>VPC</attributeValue>
+        </item>
+        <item>
+          <attributeValue>EC2</attributeValue>
+        </item>
+      </attributeValueSet>
+    </item>
+  </accountAttributeSet>
+</DescribeAccountAttributesResponse>`