plugin/route53: Configurable AWS Endpoint (#4963)

Provide the ability to configure the AWS endpoint
Signed-off-by: Matthew Palmer <matthew.palmer@helpsystems.com>

plugin/route53/README.md

@@ -16,6 +16,7 @@ The route53 plugin can be used when coredns is deployed on AWS or elsewhere.
 ~~~ txt
 route53 [ZONE:HOSTED_ZONE_ID...] {
     aws_access_key [AWS_ACCESS_KEY_ID AWS_SECRET_ACCESS_KEY]
+    aws_endpoint ENDPOINT
     credentials PROFILE [FILENAME]
     fallthrough [ZONES...]
     refresh DURATION
@@ -34,6 +35,9 @@ route53 [ZONE:HOSTED_ZONE_ID...] {
     AWS credentials the same way as AWS CLI, e.g., environmental variables, AWS credentials file,
     instance profile credentials, etc.
 
+*   `aws_endpoint` can be used to control the endpoint to use when querying AWS (optional). **ENDPOINT** is the
+    URL of the endpoint to use. If this is not provided the default AWS endpoint resolution will occur.
+
 *   `credentials` is used for reading the credential **FILENAME** and setting the **PROFILE** name for a given
     zone. **PROFILE** is the AWS account profile name. Defaults to `default`. **FILENAME** is the
     AWS credentials filename, defaults to `~/.aws/credentials`.
@@ -75,6 +79,16 @@ example.org {
 }
 ~~~
 
+Enable route53 with an explicit AWS endpoint:
+
+~~~ txt
+example.org {
+    route53 example.org.:Z1Z2Z3Z4DZ5Z6Z7 {
+      aws_endpoint https://test.us-west-2.amazonaws.com
+    }
+}
+~~~
+
 Enable route53 with fallthrough:
 
 ~~~ txt

plugin/route53/setup.go

@@ -26,8 +26,8 @@ var log = clog.NewWithPlugin("route53")
 func init() { plugin.Register("route53", setup) }
 
 // exposed for testing
-var f = func(credential *credentials.Credentials) route53iface.Route53API {
-	return route53.New(session.Must(session.NewSession(&aws.Config{Credentials: credential})))
+var f = func(credential *credentials.Credentials, endpoint *string) route53iface.Route53API {
+	return route53.New(session.Must(session.NewSession(&aws.Config{Credentials: credential, Endpoint: endpoint})))
 }
 
 func setup(c *caddy.Controller) error {
@@ -44,6 +44,7 @@ func setup(c *caddy.Controller) error {
 		sharedProvider := &credentials.SharedCredentialsProvider{}
 		var providers []credentials.Provider
 		var fall fall.F
+		var endpoint string
 
 		refresh := time.Duration(1) * time.Minute // default update frequency to 1 minute
 
@@ -79,6 +80,12 @@ func setup(c *caddy.Controller) error {
 						SecretAccessKey: v[1],
 					},
 				})
+			case "aws_endpoint":
+				if c.NextArg() {
+					endpoint = c.Val()
+				} else {
+					return plugin.Error("route53", c.ArgErr())
+				}
 			case "upstream":
 				c.RemainingArgs() // eats args
 			case "credentials":
@@ -120,7 +127,7 @@ func setup(c *caddy.Controller) error {
 		}
 
 		providers = append(providers, &credentials.EnvProvider{}, sharedProvider, defaults.RemoteCredProvider(*session.Config, session.Handlers))
-		client := f(credentials.NewChainCredentials(providers))
+		client := f(credentials.NewChainCredentials(providers), &endpoint)
 		ctx, cancel := context.WithCancel(context.Background())
 		h, err := New(ctx, client, keys, refresh)
 		if err != nil {

plugin/route53/setup_test.go

@@ -10,7 +10,7 @@ import (
 )
 
 func TestSetupRoute53(t *testing.T) {
-	f = func(credential *credentials.Credentials) route53iface.Route53API {
+	f = func(credential *credentials.Credentials, endpoint *string) route53iface.Route53API {
 		return fakeRoute53{}
 	}
 
@@ -70,6 +70,12 @@ func TestSetupRoute53(t *testing.T) {
 
 		{`route53 example.org {
 	}`, true},
+		{`route53 example.org:12345678 {
+    aws_endpoint
+}`, true},
+		{`route53 example.org:12345678 {
+    aws_endpoint https://localhost
+}`, false},
 	}
 
 	for _, test := range tests {