aws/endpoints: STS regional flag Implementation

CHANGELOG_PENDING.md

@@ -1,5 +1,8 @@
 ### SDK Features
 
 ### SDK Enhancements
+* `aws/endpoints`: Adds support for STS Regional Flags ([#2779](https://github.com/aws/aws-sdk-go/pull/2779))
+  * Adds unit test cases for STS Regional flags to test STS endpoint resolver when flag is set to `legacy` or `regional` or is `unset`.
+  * Adds error handling when loading environment config from sharedConfig or envConfig. 
 
 ### SDK Bugs

aws/client/default_retryer.go

@@ -16,19 +16,19 @@ import (
 type DefaultRetryer struct {
 	// Num max Retries is the number of max retries that will be performed.
 	// By default, this is zero.
-	NumMaxRetries    int
+	NumMaxRetries int
 
 	// MinRetryDelay is the minimum retry delay after which retry will be performed.
 	// If not set, the value is 0ns.
-	MinRetryDelay    time.Duration
+	MinRetryDelay time.Duration
 
 	// MinThrottleRetryDelay is the minimum retry delay when throttled.
 	// If not set, the value is 0ns.
 	MinThrottleDelay time.Duration
 
 	// MaxRetryDelay is the maximum retry delay before which retry must be performed.
 	// If not set, the value is 0ns.
-	MaxRetryDelay    time.Duration
+	MaxRetryDelay time.Duration
 
 	// MaxThrottleDelay is the maximum retry delay when throttled.
 	// If not set, the value is 0ns.

aws/client/default_retryer_test.go

@@ -166,7 +166,7 @@ func TestGetRetryDelay(t *testing.T) {
 }
 
 func TestRetryDelay(t *testing.T) {
-	d := DefaultRetryer{NumMaxRetries:100}
+	d := DefaultRetryer{NumMaxRetries: 100}
 	r := request.Request{}
 	for i := 0; i < 100; i++ {
 		rTemp := r

aws/config.go

@@ -246,6 +246,9 @@ type Config struct {
 	// Disabling this feature is useful when you want to use local endpoints
 	// for testing that do not support the modeled host prefix pattern.
 	DisableEndpointHostPrefix *bool
+
+	// STSRegionalEndpoint will enable regional or legacy endpoint resolving
+	STSRegionalEndpoint endpoints.STSRegionalEndpoint
 }
 
 // NewConfig returns a new Config pointer that can be chained with builder
@@ -420,6 +423,13 @@ func (c *Config) MergeIn(cfgs ...*Config) {
 	}
 }
 
+// WithSTSRegionalEndpoint will set whether or not to use regional endpoint flag
+// when resolving the endpoint for a service
+func (c *Config) WithSTSRegionalEndpoint(sre endpoints.STSRegionalEndpoint) *Config {
+	c.STSRegionalEndpoint = sre
+	return c
+}
+
 func mergeInConfig(dst *Config, other *Config) {
 	if other == nil {
 		return
@@ -520,6 +530,10 @@ func mergeInConfig(dst *Config, other *Config) {
 	if other.DisableEndpointHostPrefix != nil {
 		dst.DisableEndpointHostPrefix = other.DisableEndpointHostPrefix
 	}
+
+	if other.STSRegionalEndpoint != endpoints.UnsetSTSEndpoint {
+		dst.STSRegionalEndpoint = other.STSRegionalEndpoint
+	}
 }
 
 // Copy will return a shallow copy of the Config object. If any additional

aws/endpoints/endpoints.go

@@ -3,6 +3,7 @@ package endpoints
 import (
 	"fmt"
 	"regexp"
+	"strings"
 
 	"github.com/aws/aws-sdk-go/aws/awserr"
 )
@@ -46,6 +47,43 @@ type Options struct {
 	//
 	// This option is ignored if StrictMatching is enabled.
 	ResolveUnknownService bool
+
+	// STS Regional Endpoint flag helps with resolving the STS endpoint
+	STSRegionalEndpoint STSRegionalEndpoint
+}
+
+// STSRegionalEndpoint is an enum type alias for int
+// It is used internally by the core sdk as STS Regional Endpoint flag value
+type STSRegionalEndpoint int
+
+const (
+
+	// UnsetSTSEndpoint represents that STS Regional Endpoint flag is not specified.
+	UnsetSTSEndpoint STSRegionalEndpoint = iota
+
+	// LegacySTSEndpoint represents when STS Regional Endpoint flag is specified
+	// to use legacy endpoints.
+	LegacySTSEndpoint
+
+	// RegionalSTSEndpoint represents when STS Regional Endpoint flag is specified
+	// to use regional endpoints.
+	RegionalSTSEndpoint
+)
+
+// GetSTSRegionalEndpoint function returns the STSRegionalEndpointFlag based
+// on the input string provided in env config or shared config by the user.
+//
+// `legacy`, `regional` are the only case-insensitive valid strings for
+// resolving the STS regional Endpoint flag.
+func GetSTSRegionalEndpoint(s string) (STSRegionalEndpoint, error) {
+	switch {
+	case strings.EqualFold(s, "legacy"):
+		return LegacySTSEndpoint, nil
+	case strings.EqualFold(s, "regional"):
+		return RegionalSTSEndpoint, nil
+	default:
+		return UnsetSTSEndpoint, fmt.Errorf("unable to resolve the value of STSRegionalEndpoint for %v", s)
+	}
 }
 
 // Set combines all of the option functions together.
@@ -79,6 +117,12 @@ func ResolveUnknownServiceOption(o *Options) {
 	o.ResolveUnknownService = true
 }
 
+// STSRegionalEndpointOption enables the STS endpoint resolver behavior to resolve
+// STS endpoint to their regional endpoint, instead of the global endpoint.
+func STSRegionalEndpointOption(o *Options) {
+	o.STSRegionalEndpoint = RegionalSTSEndpoint
+}
+
 // A Resolver provides the interface for functionality to resolve endpoints.
 // The build in Partition and DefaultResolver return value satisfy this interface.
 type Resolver interface {
@@ -194,7 +238,7 @@ func (p Partition) ID() string { return p.id }
 // require the provided service and region to be known by the partition.
 // If the endpoint cannot be strictly resolved an error will be returned. This
 // mode is useful to ensure the endpoint resolved is valid. Without
-// StrictMatching enabled the endpoint returned my look valid but may not work.
+// StrictMatching enabled the endpoint returned may look valid but may not work.
 // StrictMatching requires the SDK to be updated if you want to take advantage
 // of new regions and services expansions.
 //

aws/endpoints/sts_legacy_regions.go

@@ -0,0 +1,20 @@
+package endpoints
+
+var stsLegacyGlobalRegions = map[string]struct{}{
+	"ap-northeast-1": {},
+	"ap-south-1":     {},
+	"ap-southeast-1": {},
+	"ap-southeast-2": {},
+	"aws-global":     {},
+	"ca-central-1":   {},
+	"eu-central-1":   {},
+	"eu-north-1":     {},
+	"eu-west-1":      {},
+	"eu-west-2":      {},
+	"eu-west-3":      {},
+	"sa-east-1":      {},
+	"us-east-1":      {},
+	"us-east-2":      {},
+	"us-west-1":      {},
+	"us-west-2":      {},
+}

aws/endpoints/v3model.go

@@ -79,6 +79,12 @@ func (p partition) EndpointFor(service, region string, opts ...func(*Options)) (
 	var opt Options
 	opt.Set(opts...)
 
+	if service == "sts" && opt.STSRegionalEndpoint != RegionalSTSEndpoint {
+		if _, ok := stsLegacyGlobalRegions[region]; ok {
+			region = "aws-global"
+		}
+	}
+
 	s, hasService := p.Services[service]
 	if !(hasService || opt.ResolveUnknownService) {
 		// Only return error if the resolver will not fallback to creating
@@ -92,6 +98,7 @@ func (p partition) EndpointFor(service, region string, opts ...func(*Options)) (
 	}
 
 	defs := []endpoint{p.Defaults, s.Defaults}
+
 	return e.resolve(service, region, p.DNSSuffix, defs, opt), nil
 }
 

aws/endpoints/v3model_shared_test.go

@@ -0,0 +1,69 @@
+package endpoints
+
+import "regexp"
+
+var testPartitions = partitions{
+	partition{
+		ID:        "part-id",
+		Name:      "partitionName",
+		DNSSuffix: "amazonaws.com",
+		RegionRegex: regionRegex{
+			Regexp: func() *regexp.Regexp {
+				reg, _ := regexp.Compile("^(us|eu|ap|sa|ca)\\-\\w+\\-\\d+$")
+				return reg
+			}(),
+		},
+		Defaults: endpoint{
+			Hostname:          "{service}.{region}.{dnsSuffix}",
+			Protocols:         []string{"https"},
+			SignatureVersions: []string{"v4"},
+		},
+		Regions: regions{
+			"us-east-1": region{
+				Description: "region description",
+			},
+			"us-west-2": region{},
+		},
+		Services: services{
+			"s3": service{},
+			"service1": service{
+				Defaults: endpoint{
+					CredentialScope: credentialScope{
+						Service: "service1",
+					},
+				},
+				Endpoints: endpoints{
+					"us-east-1": {},
+					"us-west-2": {
+						HasDualStack:      boxedTrue,
+						DualStackHostname: "{service}.dualstack.{region}.{dnsSuffix}",
+					},
+				},
+			},
+			"service2": service{
+				Defaults: endpoint{
+					CredentialScope: credentialScope{
+						Service: "service2",
+					},
+				},
+			},
+			"httpService": service{
+				Defaults: endpoint{
+					Protocols: []string{"http"},
+				},
+			},
+			"globalService": service{
+				IsRegionalized:    boxedFalse,
+				PartitionEndpoint: "aws-global",
+				Endpoints: endpoints{
+					"aws-global": endpoint{
+						CredentialScope: credentialScope{
+							Region: "us-east-1",
+						},
+						Hostname: "globalService.amazonaws.com",
+					},
+				},
+			},
+		},
+	},
+}