added s3-ec2role provider; fix #431

README.md

@@ -91,7 +91,7 @@ web-path | path to static web files (for development or custom front end) | | WE
 proxy-path | path prefix when service is run behind a proxy | | PROXY_PATH |
 proxy-port | port of the proxy when the service is run behind a proxy | | PROXY_PORT |
 ga-key | google analytics key for the front end | | GA_KEY |
-provider | which storage provider to use | (s3, storj, gdrive or local) |
+provider | which storage provider to use | (s3, s3-ec2role, storj, gdrive or local) |
 uservoice-key | user voice key for the front end  | | USERVOICE_KEY |
 aws-access-key | aws access key | | AWS_ACCESS_KEY |
 aws-secret-key | aws access key | | AWS_SECRET_KEY |
@@ -155,6 +155,17 @@ For the usage with a AWS S3 Bucket, you just need to specify the following optio
 
 If you specify the s3-region, you don't need to set the endpoint URL since the correct endpoint will used automatically.
 
+### S3 Usage with an AWS IAM Role
+
+With the `s3-ec2role` provider you can use S3 without static credentials: aws-access-key and aws-secret-key.
+
+You just need to specify the following options:
+ - provider
+ - bucket
+ - s3-region
+
+How it works, [here](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_use_switch-role-ec2.html).
+
 ### Custom S3 providers
 
 To use a custom non-AWS S3 provider, you need to specify the endpoint as defined from your cloud provider.

cmd/cmd.go

@@ -112,7 +112,7 @@ var globalFlags = []cli.Flag{
 	},
 	cli.StringFlag{
 		Name:   "provider",
-		Usage:  "s3|gdrive|local",
+		Usage:  "s3|s3-ec2role|gdrive|local",
 		Value:  "",
 		EnvVar: "PROVIDER",
 	},
@@ -445,6 +445,14 @@ func New() *Cmd {
 			} else {
 				options = append(options, server.UseStorage(storage))
 			}
+		case "s3-ec2role": // using AWS IAM Role and EC2 Profile
+			if bucket := c.String("bucket"); bucket == "" {
+				panic("bucket not set.")
+			} else if storage, err := server.NewS3Storage("", "", bucket, purgeDays, c.String("s3-region"), c.String("s3-endpoint"), c.Bool("s3-no-multipart"), c.Bool("s3-path-style"), logger); err != nil {
+				panic(err)
+			} else {
+				options = append(options, server.UseStorage(storage))
+			}
 		case "gdrive":
 			chunkSize := c.Int("gdrive-chunk-size")
 

server/utils.go

@@ -41,6 +41,21 @@ import (
 )
 
 func getAwsSession(accessKey, secretKey, region, endpoint string, forcePathStyle bool) *session.Session {
+
+	if accessKey+secretKey == "" {
+		return session.Must(session.NewSessionWithOptions(session.Options{
+			SharedConfigState: session.SharedConfigEnable,
+			Config: aws.Config{
+				// this config will be used only for backward compatibility to work with S3 client and s3manager;
+				// a not for getting session credentials;
+				// will be better to refactor NewS3Storage() function with s3.New(sess, &aws.Config{...})
+				Region:           aws.String(region),
+				Endpoint:         aws.String(endpoint),
+				S3ForcePathStyle: aws.Bool(forcePathStyle),
+			},
+		}))
+	}
+
 	return session.Must(session.NewSession(&aws.Config{
 		Region:           aws.String(region),
 		Endpoint:         aws.String(endpoint),