Add ec2 roles credentials.

README.ja.md

@@ -1059,8 +1059,35 @@ With this sample command, it will ..
 
 事前にAWS関連の設定を行う
 - S3バケットを作成 [Creating a Bucket](http://docs.aws.amazon.com/AmazonS3/latest/UG/CreatingaBucket.html)
-- アクセスキーを作成し、S3バケットへのREAD/WRITE権限をつけておく [Managing Access Keys for IAM Users](http://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_access-keys.html)
-- security credentialsを設定 [Configuring the AWS Command Line Interface](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html)
+- いずれかの方法でS3リソースへアクセスする設定を行う
+    - 環境変数を設定 [Configuring the AWS Command Line Interface](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html)
+    - Security Credentialsを設定 [Configuring the AWS Command Line Interface](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html)
+    - サービス用のIAMロールを作成し、サービス(EC2, AWS Lambda)にアタッチ [Creating a Role to Delegate Permissions to an AWS Service](http://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_create_for-service.html)
+- 環境変数、Security Credentialsを設定する場合はアクセスキーを作成する [Managing Access Keys for IAM Users](http://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_access-keys.html)
+
+IAMポリシーの例:
+
+```
+{
+    "Version": "2012-10-17",
+    "Statement": [
+        {
+            "Effect": "Allow",
+            "Action": [
+                "s3:ListAllMyBuckets"
+            ],
+            "Resource": "arn:aws:s3:::*"
+        },
+        {
+            "Effect": "Allow",
+            "Action": [
+                "s3:PutObject"
+            ],
+            "Resource": "arn:aws:s3:::vuls/*"
+        }
+    ]
+}
+```
 
 ```
 $ vuls scan \

README.md

@@ -1064,8 +1064,36 @@ With this sample command, it will ..
 ## Example: Put results in S3 bucket
 To put results in S3 bucket, configure following settings in AWS before reporting.
 - Create S3 bucket. see [Creating a Bucket](http://docs.aws.amazon.com/AmazonS3/latest/UG/CreatingaBucket.html)  
-- Create access key. The access key must have read and write access to the AWS S3 bucket. see [Managing Access Keys for IAM Users](http://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_access-keys.html)
-- Configure the security credentials. see [Configuring the AWS Command Line Interface](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html)
+- Configure access to S3 resources. You can do this in several ways:
+  - Configure the environment variables. see [Configuring the AWS Command Line Interface](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html)
+  - Configure the security credentials. see [Configuring the AWS Command Line Interface](http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html)
+  - Create an IAM role for the service and attach it to the service(EC2, AWS Lambda). [Creating a Role to Delegate Permissions to an AWS Service](http://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_create_for-service.html)
+- To configure environment variables, security credentials, create an access key. see [Managing Access Keys for IAM Users](http://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_access-keys.html)
+
+
+Example of IAM policy:
+
+```
+{
+    "Version": "2012-10-17",
+    "Statement": [
+        {
+            "Effect": "Allow",
+            "Action": [
+                "s3:ListAllMyBuckets"
+            ],
+            "Resource": "arn:aws:s3:::*"
+        },
+        {
+            "Effect": "Allow",
+            "Action": [
+                "s3:PutObject"
+            ],
+            "Resource": "arn:aws:s3:::vuls/*"
+        }
+    ]
+}
+```
 
 ```
 $ vuls report \

report/s3.go

@@ -26,6 +26,8 @@ import (
 
 	"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/s3"
 
@@ -37,10 +39,15 @@ import (
 type S3Writer struct{}
 
 func getS3() *s3.S3 {
-	return s3.New(session.New(&aws.Config{
-		Region:      aws.String(c.Conf.AwsRegion),
-		Credentials: credentials.NewSharedCredentials("", c.Conf.AwsProfile),
-	}))
+	Config := &aws.Config{
+		Region: aws.String(c.Conf.AwsRegion),
+		Credentials: credentials.NewChainCredentials([]credentials.Provider{
+			&credentials.EnvProvider{},
+			&credentials.SharedCredentialsProvider{Filename: "", Profile: c.Conf.AwsProfile},
+			&ec2rolecreds.EC2RoleProvider{Client: ec2metadata.New(session.New())},
+		}),
+	}
+	return s3.New(session.New(Config))
 }
 
 // Write results to S3