From 14f6f90621145b9823ef041741c4ea5c66a33fcc Mon Sep 17 00:00:00 2001
From: John Engelman <john.r.engelman@gmail.com>
Date: Fri, 6 May 2016 11:52:18 -0500
Subject: [PATCH] Support standard AWS config in the S3 remote backend. (#5270)

---
 state/remote/s3.go                          | 38 +++++++++------------
 website/source/docs/state/remote/s3.html.md |  3 ++
 2 files changed, 19 insertions(+), 22 deletions(-)

diff --git a/state/remote/s3.go b/state/remote/s3.go
index af322cb6f..230df5fce 100644
--- a/state/remote/s3.go
+++ b/state/remote/s3.go
@@ -10,12 +10,11 @@ import (
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/awserr"
-	"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"
 	"github.com/hashicorp/go-cleanhttp"
+	"github.com/hashicorp/go-multierror"
+	terraformAws "github.com/hashicorp/terraform/builtin/providers/aws"
 )
 
 func s3Factory(conf map[string]string) (Client, error) {
@@ -60,29 +59,24 @@ func s3Factory(conf map[string]string) (Client, error) {
 	}
 	kmsKeyID := conf["kms_key_id"]
 
-	accessKeyId := conf["access_key"]
-	secretAccessKey := conf["secret_key"]
-
-	credentialsProvider := credentials.NewChainCredentials([]credentials.Provider{
-		&credentials.StaticProvider{Value: credentials.Value{
-			AccessKeyID:     accessKeyId,
-			SecretAccessKey: secretAccessKey,
-			SessionToken:    "",
-		}},
-		&credentials.EnvProvider{},
-		&credentials.SharedCredentialsProvider{Filename: "", Profile: ""},
-		&ec2rolecreds.EC2RoleProvider{Client: ec2metadata.New(session.New())},
-	})
-
-	// Make sure we got some sort of working credentials.
-	_, err := credentialsProvider.Get()
+	var errs []error
+	creds := terraformAws.GetCredentials(conf["access_key"], conf["secret_key"], conf["token"], conf["profile"], conf["shared_credentials_file"])
+	// Call Get to check for credential provider. If nothing found, we'll get an
+	// error, and we can present it nicely to the user
+	_, err := creds.Get()
 	if err != nil {
-		return nil, fmt.Errorf("Unable to determine AWS credentials. Set the AWS_ACCESS_KEY_ID and "+
-			"AWS_SECRET_ACCESS_KEY environment variables.\n(error was: %s)", err)
+		if awsErr, ok := err.(awserr.Error); ok && awsErr.Code() == "NoCredentialProviders" {
+			errs = append(errs, fmt.Errorf(`No valid credential sources found for AWS S3 remote.
+Please see https://www.terraform.io/docs/state/remote/s3.html for more information on
+providing credentials for the AWS S3 remote`))
+		} else {
+			errs = append(errs, fmt.Errorf("Error loading credentials for AWS S3 remote: %s", err))
+		}
+		return nil, &multierror.Error{Errors: errs}
 	}
 
 	awsConfig := &aws.Config{
-		Credentials: credentialsProvider,
+		Credentials: creds,
 		Endpoint:    aws.String(endpoint),
 		Region:      aws.String(regionName),
 		HTTPClient:  cleanhttp.DefaultClient(),
diff --git a/website/source/docs/state/remote/s3.html.md b/website/source/docs/state/remote/s3.html.md
index 84ca21323..40be5088f 100644
--- a/website/source/docs/state/remote/s3.html.md
+++ b/website/source/docs/state/remote/s3.html.md
@@ -56,3 +56,6 @@ The following configuration options / environment variables are supported:
  * `access_key` / `AWS_ACCESS_KEY_ID` - (Optional) AWS access key
  * `secret_key` / `AWS_SECRET_ACCESS_KEY` - (Optional) AWS secret key
  * `kms_key_id` - (Optional) The ARN of a KMS Key to use for encrypting the state.
+ * `profile` - (Optional) This is the AWS profile name as set in the shared credentials file.
+ * `shared_credentials_file`  - (Optional) This is the path to the shared credentials file. If this is not set and a profile is specified, ~/.aws/credentials will be used.
+ * `token` - (Optional) Use this to set an MFA token. It can also be sourced from the `AWS_SECURITY_TOKEN` environment variable.