Vendor AWS ARN parser (#5048)

This adds the AWS ARN parser into the vendor as suggested by
https://github.com/hashicorp/vault/pull/4360#discussion_r186744987

vendor/github.com/aws/aws-sdk-go/aws/arn/arn.go

@@ -0,0 +1,86 @@
+// Package arn provides a parser for interacting with Amazon Resource Names.
+package arn
+
+import (
+	"errors"
+	"strings"
+)
+
+const (
+	arnDelimiter = ":"
+	arnSections  = 6
+	arnPrefix    = "arn:"
+
+	// zero-indexed
+	sectionPartition = 1
+	sectionService   = 2
+	sectionRegion    = 3
+	sectionAccountID = 4
+	sectionResource  = 5
+
+	// errors
+	invalidPrefix   = "arn: invalid prefix"
+	invalidSections = "arn: not enough sections"
+)
+
+// ARN captures the individual fields of an Amazon Resource Name.
+// See http://docs.aws.amazon.com/general/latest/gr/aws-arns-and-namespaces.html for more information.
+type ARN struct {
+	// The partition that the resource is in. For standard AWS regions, the partition is "aws". If you have resources in
+	// other partitions, the partition is "aws-partitionname". For example, the partition for resources in the China
+	// (Beijing) region is "aws-cn".
+	Partition string
+
+	// The service namespace that identifies the AWS product (for example, Amazon S3, IAM, or Amazon RDS). For a list of
+	// namespaces, see
+	// http://docs.aws.amazon.com/general/latest/gr/aws-arns-and-namespaces.html#genref-aws-service-namespaces.
+	Service string
+
+	// The region the resource resides in. Note that the ARNs for some resources do not require a region, so this
+	// component might be omitted.
+	Region string
+
+	// The ID of the AWS account that owns the resource, without the hyphens. For example, 123456789012. Note that the
+	// ARNs for some resources don't require an account number, so this component might be omitted.
+	AccountID string
+
+	// The content of this part of the ARN varies by service. It often includes an indicator of the type of resource —
+	// for example, an IAM user or Amazon RDS database - followed by a slash (/) or a colon (:), followed by the
+	// resource name itself. Some services allows paths for resource names, as described in
+	// http://docs.aws.amazon.com/general/latest/gr/aws-arns-and-namespaces.html#arns-paths.
+	Resource string
+}
+
+// Parse parses an ARN into its constituent parts.
+//
+// Some example ARNs:
+// arn:aws:elasticbeanstalk:us-east-1:123456789012:environment/My App/MyEnvironment
+// arn:aws:iam::123456789012:user/David
+// arn:aws:rds:eu-west-1:123456789012:db:mysql-db
+// arn:aws:s3:::my_corporate_bucket/exampleobject.png
+func Parse(arn string) (ARN, error) {
+	if !strings.HasPrefix(arn, arnPrefix) {
+		return ARN{}, errors.New(invalidPrefix)
+	}
+	sections := strings.SplitN(arn, arnDelimiter, arnSections)
+	if len(sections) != arnSections {
+		return ARN{}, errors.New(invalidSections)
+	}
+	return ARN{
+		Partition: sections[sectionPartition],
+		Service:   sections[sectionService],
+		Region:    sections[sectionRegion],
+		AccountID: sections[sectionAccountID],
+		Resource:  sections[sectionResource],
+	}, nil
+}
+
+// String returns the canonical representation of the ARN
+func (arn ARN) String() string {
+	return arnPrefix +
+		arn.Partition + arnDelimiter +
+		arn.Service + arnDelimiter +
+		arn.Region + arnDelimiter +
+		arn.AccountID + arnDelimiter +
+		arn.Resource
+}

vendor/vendor.json

@@ -300,6 +300,12 @@
 			"revision": "c01ebd0d48a4772fd28a0b684db0f36882dc995c",
 			"revisionTime": "2018-07-11T05:22:29Z"
 		},
+		{
+			"checksumSHA1": "DtuTqKH29YnLjrIJkRYX0HQtXY0=",
+			"path": "github.com/aws/aws-sdk-go/aws/arn",
+			"revision": "c01ebd0d48a4772fd28a0b684db0f36882dc995c",
+			"revisionTime": "2018-07-11T05:22:29Z"
+		},
 		{
 			"checksumSHA1": "Y9W+4GimK4Fuxq+vyIskVYFRnX4=",
 			"path": "github.com/aws/aws-sdk-go/aws/awserr",