plugins/route53: add AWS credentials file support (#2118)

Automatically submitted.

plugin/route53/README.md

@@ -16,6 +16,7 @@ The route53 plugin can be used when coredns is deployed on AWS or elsewhere.
 route53 [ZONE:HOSTED_ZONE_ID...] {
     [aws_access_key AWS_ACCESS_KEY_ID AWS_SECRET_ACCESS_KEY]
     upstream [ADDRESS...]
+    credentials PROFILE [FILENAME]
     fallthrough [ZONES...]
 }
 ~~~
@@ -30,6 +31,9 @@ route53 [ZONE:HOSTED_ZONE_ID...] {
    to external hosts (eg. used to resolve CNAMEs). If no **ADDRESS** is given, CoreDNS will resolve
    against itself. **ADDRESS** can be an IP, an IP:port or a path to a file structured like
    resolv.conf (**NB**: Currently a bug (#2099) is preventing the use of self-resolver).
+* `credentials` used for reading the credential file and setting the profile name for a given zone.
+* **PROFILE** AWS account profile name. Defaults to `default`.
+* **FILENAME** AWS credentials filename. Defaults to `~/.aws/credentials`
    are used.
 * `fallthrough` If zone matches and no record can be generated, pass request to the next plugin.
   If **[ZONES...]** is omitted, then fallthrough happens for all zones for which the plugin
@@ -39,7 +43,7 @@ route53 [ZONE:HOSTED_ZONE_ID...] {
 
 ## Examples
 
-Enable route53 with implicit aws credentials and an upstream:
+Enable route53 with implicit AWS credentials and an upstream:
 
 ~~~ txt
 . {
@@ -48,7 +52,7 @@ Enable route53 with implicit aws credentials and an upstream:
 }
 ~~~
 
-Enable route53 with explicit aws credentials:
+Enable route53 with explicit AWS credentials:
 
 ~~~ txt
 . {
@@ -67,3 +71,13 @@ Enable route53 with fallthrough:
     }
 }
 ~~~
+
+Enable route53 with AWS credentials file:
+
+~~~ txt
+. {
+    route53 example.org.:Z1Z2Z3Z4DZ5Z6Z7 {
+      credentials_file some-user
+    }
+}
+~~~

plugin/route53/setup.go

@@ -36,7 +36,15 @@ func init() {
 
 func setup(c *caddy.Controller, f func(*credentials.Credentials) route53iface.Route53API) error {
 	keys := map[string]string{}
-	credential := credentials.NewEnvCredentials()
+
+	// Route53 plugin attempts to find AWS credentials by using ChainCredentials.
+	// And the order of that provider chain is as follows:
+	// Static AWS keys -> Environment Variables -> Credentials file -> IAM role
+	// With that said, even though a user doesn't define any credentials in
+	// Corefile, we should still attempt to read the default credentials file,
+	// ~/.aws/credentials with the default profile.
+	sharedProvider := &credentials.SharedCredentialsProvider{}
+	var providers []credentials.Provider
 	var fall fall.F
 
 	up, _ := upstream.New(nil)
@@ -65,7 +73,12 @@ func setup(c *caddy.Controller, f func(*credentials.Credentials) route53iface.Ro
 				if len(v) < 2 {
 					return c.Errf("invalid access key '%v'", v)
 				}
-				credential = credentials.NewStaticCredentials(v[0], v[1], "")
+				providers = append(providers, &credentials.StaticProvider{
+					Value: credentials.Value{
+						AccessKeyID:     v[0],
+						SecretAccessKey: v[1],
+					},
+				})
 			case "upstream":
 				args := c.RemainingArgs()
 				// TODO(dilyevsky): There is a bug that causes coredns to crash
@@ -78,6 +91,15 @@ func setup(c *caddy.Controller, f func(*credentials.Credentials) route53iface.Ro
 				if err != nil {
 					return c.Errf("invalid upstream: %v", err)
 				}
+			case "credentials":
+				if c.NextArg() {
+					sharedProvider.Profile = c.Val()
+				} else {
+					return c.ArgErr()
+				}
+				if c.NextArg() {
+					sharedProvider.Filename = c.Val()
+				}
 			case "fallthrough":
 				fall.SetZonesFromArgs(c.RemainingArgs())
 			default:
@@ -85,7 +107,9 @@ func setup(c *caddy.Controller, f func(*credentials.Credentials) route53iface.Ro
 			}
 		}
 	}
-	client := f(credential)
+	providers = append(providers, &credentials.EnvProvider{}, sharedProvider)
+
+	client := f(credentials.NewChainCredentials(providers))
 	ctx := context.Background()
 	h, err := New(ctx, client, keys, &up)
 	if err != nil {

plugin/route53/setup_test.go

@@ -59,4 +59,36 @@ func TestSetupRoute53(t *testing.T) {
 	if err := setup(c, f); err != nil {
 		t.Fatalf("Unexpected errors: %v", err)
 	}
+
+	c = caddy.NewTestController("dns", `route53 example.org:12345678 {
+		credentials
+ 		upstream 1.2.3.4
+	}`)
+	if err := setup(c, f); err == nil {
+		t.Fatalf("Expected errors, but got: %v", err)
+	}
+
+	c = caddy.NewTestController("dns", `route53 example.org:12345678 {
+		credentials default
+ 		upstream 1.2.3.4
+	}`)
+	if err := setup(c, f); err != nil {
+		t.Fatalf("Unexpected errors: %v", err)
+	}
+
+	c = caddy.NewTestController("dns", `route53 example.org:12345678 {
+		credentials default credentials
+ 		upstream 1.2.3.4
+	}`)
+	if err := setup(c, f); err != nil {
+		t.Fatalf("Unexpected errors: %v", err)
+	}
+
+	c = caddy.NewTestController("dns", `route53 example.org:12345678 {
+		credentials default credentials extra-arg
+ 		upstream 1.2.3.4
+	}`)
+	if err := setup(c, f); err == nil {
+		t.Fatalf("Expected errors, but got: %v", err)
+	}
 }