Add route53 plugin (#1390)

* Update vendor

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Add route53 plugin

This fix adds route53 plugin so that it is possible to
query route53 record through CoreDNS.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

plugin/route53/setup.go

@@ -0,0 +1,89 @@
+package route53
+
+import (
+	"strings"
+
+	"github.com/coredns/coredns/core/dnsserver"
+	"github.com/coredns/coredns/plugin"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/credentials"
+	"github.com/aws/aws-sdk-go/aws/session"
+	"github.com/aws/aws-sdk-go/service/route53"
+	"github.com/aws/aws-sdk-go/service/route53/route53iface"
+	"github.com/mholt/caddy"
+)
+
+func init() {
+	caddy.RegisterPlugin("route53", caddy.Plugin{
+		ServerType: "dns",
+		Action: func(c *caddy.Controller) error {
+			f := func(credential *credentials.Credentials) route53iface.Route53API {
+				return route53.New(session.Must(session.NewSession(&aws.Config{
+					Credentials: credential,
+				})))
+			}
+			return setup(c, f)
+		},
+	})
+}
+
+func setup(c *caddy.Controller, f func(*credentials.Credentials) route53iface.Route53API) error {
+	keys := map[string]string{}
+	var credential *credentials.Credentials
+	for c.Next() {
+		args := c.RemainingArgs()
+
+		for i := 0; i < len(args); i++ {
+			parts := strings.SplitN(args[i], ":", 2)
+			if len(parts) != 2 {
+				return c.Errf("invalid zone '%s'", args[i])
+			}
+			if parts[0] == "" || parts[1] == "" {
+				return c.Errf("invalid zone '%s'", args[i])
+			}
+			zone := plugin.Host(parts[0]).Normalize()
+			if v, ok := keys[zone]; ok && v != parts[1] {
+				return c.Errf("conflict zone '%s' ('%s' vs. '%s')", zone, v, parts[1])
+			}
+			keys[zone] = parts[1]
+		}
+
+		for c.NextBlock() {
+			switch c.Val() {
+			case "aws_access_key":
+				v := c.RemainingArgs()
+				if len(v) < 2 {
+					return c.Errf("invalid access key '%v'", v)
+				}
+				credential = credentials.NewStaticCredentials(v[0], v[1], "")
+			default:
+				return c.Errf("unknown property '%s'", c.Val())
+			}
+		}
+	}
+	client := f(credential)
+	zones := []string{}
+	for zone, v := range keys {
+		// Make sure enough credentials is needed
+		if _, err := client.ListResourceRecordSets(&route53.ListResourceRecordSetsInput{
+			HostedZoneId: aws.String(v),
+			MaxItems:     aws.String("1"),
+		}); err != nil {
+			return c.Errf("aws error: '%s'", err)
+		}
+
+		zones = append(zones, zone)
+	}
+
+	dnsserver.GetConfig(c).AddPlugin(func(next plugin.Handler) plugin.Handler {
+		return Route53{
+			Next:   next,
+			keys:   keys,
+			zones:  zones,
+			client: client,
+		}
+	})
+
+	return nil
+}