Support more forms of EC2 authentication

command/agent/command.go

@@ -19,6 +19,8 @@ import (
 	"github.com/armon/go-metrics/datadog"
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/credentials"
+	"github.com/aws/aws-sdk-go/aws/credentials/ec2rolecreds"
+	"github.com/aws/aws-sdk-go/aws/ec2metadata"
 	"github.com/aws/aws-sdk-go/aws/session"
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/hashicorp/consul/lib"
@@ -196,15 +198,6 @@ func (c *Command) readConfig() *Config {
 		config.SkipLeaveOnInt = Bool(config.Server)
 	}
 
-	// Load AWS creds for discovery from the environment (if present)
-	if os.Getenv("AWS_ACCESS_KEY_ID") != "" {
-		config.EC2Discovery.AccessKeyID = os.Getenv("AWS_ACCESS_KEY_ID")
-	}
-
-	if os.Getenv("AWS_SECRET_ACCESS_KEY") != "" {
-		config.EC2Discovery.SecretAccessKey = os.Getenv("AWS_SECRET_ACCESS_KEY")
-	}
-
 	// Ensure we have a data directory
 	if config.DataDir == "" && !dev {
 		c.Ui.Error("Must specify data directory using -data-dir")
@@ -344,6 +337,7 @@ func (c *Command) readConfig() *Config {
 			c.Ui.Error(fmt.Sprintf("Unable to query EC2 insances: %s", err))
 			return nil
 		}
+		c.Ui.Info(fmt.Sprintf("Discovered %d servers from EC2...", len(ec2servers)))
 		config.StartJoin = append(config.StartJoin, ec2servers...)
 	}
 
@@ -405,7 +399,20 @@ func (c *Config) discoverEc2Hosts() ([]string, error) {
 	config := c.EC2Discovery
 	awsConfig := &aws.Config{
 		Region: aws.String(config.Region),
-		Credentials: credentials.NewStaticCredentials(config.AccessKeyID, config.SecretAccessKey, ""),
+		Credentials: credentials.NewChainCredentials(
+			[]credentials.Provider{
+				&credentials.StaticProvider{
+					Value: credentials.Value{
+						AccessKeyID:     config.AccessKeyID,
+						SecretAccessKey: config.SecretAccessKey,
+					},
+				},
+				&credentials.EnvProvider{},
+				&credentials.SharedCredentialsProvider{},
+				&ec2rolecreds.EC2RoleProvider{
+					Client: ec2metadata.New(session.New()),
+				},
+			}),
 	}
 
 	svc := ec2.New(session.New(), awsConfig)
@@ -428,9 +435,12 @@ func (c *Config) discoverEc2Hosts() ([]string, error) {
 	servers := make([]string, 0)
 	for i := range resp.Reservations {
 		for _, instance := range resp.Reservations[i].Instances {
+			// Terminated instances don't have the PrivateIpAddress field
+			if instance.PrivateIpAddress != nil {
 				servers = append(servers, *instance.PrivateIpAddress)
 			}
 		}
+	}
 
 	return servers, nil
 }

command/agent/command_test.go

@@ -282,8 +282,6 @@ func TestDiscoverEC2Hosts(t *testing.T) {
 	c := &Config{
 		EC2Discovery: EC2Discovery{
 			Region:   os.Getenv("AWS_REGION"),
-			AccessKeyID:     os.Getenv("AWS_ACCESS_KEY_ID"),
-			SecretAccessKey: os.Getenv("AWS_SECRET_ACCESS_KEY"),
 			TagKey:   "ConsulRole",
 			TagValue: "Server",
 		},