From 0919216d3ca513d6ae18ffb0ed35b6a89fd393c6 Mon Sep 17 00:00:00 2001
From: Miek Gieben <miek@miek.nl>
Date: Wed, 9 Nov 2016 21:26:49 +0000
Subject: [PATCH] middleware/{file, auto}: resolve external CNAMEs

Do the same thing as in etcd and give the option of externally resolving
CNAME. This is needed when CoreDNS is a proxy as well is serving zones.
---
 middleware/auto/README.md     |  6 ++++
 middleware/auto/auto.go       |  2 ++
 middleware/auto/setup.go      | 15 +++++++++
 middleware/etcd/README.md     |  4 +--
 middleware/etcd/setup_test.go |  2 +-
 middleware/file/README.md     |  3 ++
 middleware/file/cname_test.go | 63 ++++++++++++++++++++++++++++++++++-
 middleware/file/lookup.go     | 19 +++++++++--
 middleware/file/setup.go      | 16 +++++++++
 middleware/file/zone.go       |  2 ++
 10 files changed, 125 insertions(+), 7 deletions(-)

diff --git a/middleware/auto/README.md b/middleware/auto/README.md
index 94a606708..64807b821 100644
--- a/middleware/auto/README.md
+++ b/middleware/auto/README.md
@@ -13,6 +13,8 @@ zonefile. New zones or changed zone are automatically picked up from disk.
 ~~~
 auto [ZONES...] {
     directory DIR [REGEXP ORIGIN_TEMPLATE [TIMEOUT]]
+    no_reload
+    upstream ADDRESS...
 }
 ~~~
 
@@ -26,6 +28,10 @@ are used.
   name `db.example.com`, the extracted origin will be `example.com`. **TIMEOUT** specifies how often
   CoreDNS should scan the directory, the default is every 60 seconds. This value is in seconds.
   The minimum value is 1 second.
+* `no_reload` by default CoreDNS will reload a zone from disk whenever it detects a change to the
+  file. This option disables that behavior.
+* `upstream` defines upstream resolvers to be used resolve external names found (think CNAMEs)
+  pointing to external names.
 
 All directives from the *file* middleware are supported. Note that *auto* will load all zones found,
 even though the directive might only receive queries for a specific zone. I.e:
diff --git a/middleware/auto/auto.go b/middleware/auto/auto.go
index eaff7fd18..ec04a8766 100644
--- a/middleware/auto/auto.go
+++ b/middleware/auto/auto.go
@@ -9,6 +9,7 @@ import (
 	"github.com/miekg/coredns/middleware"
 	"github.com/miekg/coredns/middleware/file"
 	"github.com/miekg/coredns/middleware/metrics"
+	"github.com/miekg/coredns/middleware/proxy"
 	"github.com/miekg/coredns/request"
 
 	"github.com/miekg/dns"
@@ -33,6 +34,7 @@ type (
 		// In the future this should be something like ZoneMeta that contains all this stuff.
 		transferTo []string
 		noReload   bool
+		Proxy      proxy.Proxy // Proxy for looking up names during the resolution process
 
 		duration time.Duration
 	}
diff --git a/middleware/auto/setup.go b/middleware/auto/setup.go
index 7681ea957..2d397a079 100644
--- a/middleware/auto/setup.go
+++ b/middleware/auto/setup.go
@@ -2,6 +2,7 @@ package auto
 
 import (
 	"log"
+	"net"
 	"os"
 	"path"
 	"regexp"
@@ -12,6 +13,7 @@ import (
 	"github.com/miekg/coredns/middleware"
 	"github.com/miekg/coredns/middleware/file"
 	"github.com/miekg/coredns/middleware/metrics"
+	"github.com/miekg/coredns/middleware/proxy"
 
 	"github.com/mholt/caddy"
 )
@@ -142,6 +144,19 @@ func autoParse(c *caddy.Controller) (Auto, error) {
 				case "no_reload":
 					a.loader.noReload = true
 
+				case "upstream":
+					args := c.RemainingArgs()
+					if len(args) == 0 {
+						return a, false, c.ArgErr()
+					}
+					for i := 0; i < len(args); i++ {
+						h, p, e := net.SplitHostPort(args[i])
+						if e != nil && p == "" {
+							args[i] = h + ":53"
+						}
+					}
+					a.loader.Proxy = proxy.New(args)
+
 				default:
 					t, _, e := file.TransferParse(c, false)
 					if e != nil {
diff --git a/middleware/etcd/README.md b/middleware/etcd/README.md
index edb47e54f..0ec8f3271 100644
--- a/middleware/etcd/README.md
+++ b/middleware/etcd/README.md
@@ -35,8 +35,8 @@ etcd [ZONES...] {
     under the *first* zone specified.
 * **PATH** the path inside etcd. Defaults to "/skydns".
 * **ENDPOINT** the etcd endpoints. Defaults to "http://localhost:2397".
-* `upstream` upstream resolvers to be used resolve external names found in etcd (think CNAMEs)
-  pointing to external names. If you want CoreDNS to act as a proxy for clients, you'll need to add
+* `upstream` defines upstream resolvers to be used resolve external names found (think CNAMEs)
+  pointing to external names. If you want CoreDNS also to act as a proxy for clients, you'll need to add
   the proxy middleware.
 * `tls` followed the cert, key and the CA's cert filenames.
 * `debug` allows for debug queries. Prefix the name with `o-o.debug.` to retrieve extra information in the
diff --git a/middleware/etcd/setup_test.go b/middleware/etcd/setup_test.go
index 6e1eabdcd..c1e33109c 100644
--- a/middleware/etcd/setup_test.go
+++ b/middleware/etcd/setup_test.go
@@ -9,7 +9,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/mholt/caddy"
 	"github.com/miekg/coredns/middleware/etcd/msg"
 	"github.com/miekg/coredns/middleware/pkg/dnsrecorder"
 	"github.com/miekg/coredns/middleware/pkg/singleflight"
@@ -17,6 +16,7 @@ import (
 	"github.com/miekg/coredns/middleware/test"
 
 	etcdc "github.com/coreos/etcd/client"
+	"github.com/mholt/caddy"
 	"github.com/miekg/dns"
 	"golang.org/x/net/context"
 )
diff --git a/middleware/file/README.md b/middleware/file/README.md
index 4cc27e2de..283986945 100644
--- a/middleware/file/README.md
+++ b/middleware/file/README.md
@@ -27,6 +27,7 @@ TSIG key information, something like `transfer out [ADDRESS...] key [NAME[:ALG]]
 file DBFILE [ZONES... ] {
     transfer to ADDRESS...
     no_reload
+    upstream ADDRESS...
 }
 ~~~
 
@@ -36,6 +37,8 @@ file DBFILE [ZONES... ] {
   When an address is specified a notify message will be send whenever the zone is reloaded.
 * `no_reload` by default CoreDNS will reload a zone from disk whenever it detects a change to the
   file. This option disables that behavior.
+* `upstream` defines upstream resolvers to be used resolve external names found (think CNAMEs)
+  pointing to external names.
 
 ## Examples
 
diff --git a/middleware/file/cname_test.go b/middleware/file/cname_test.go
index 800020068..2388aef33 100644
--- a/middleware/file/cname_test.go
+++ b/middleware/file/cname_test.go
@@ -6,6 +6,7 @@ import (
 	"testing"
 
 	"github.com/miekg/coredns/middleware/pkg/dnsrecorder"
+	"github.com/miekg/coredns/middleware/proxy"
 	"github.com/miekg/coredns/middleware/test"
 
 	"github.com/miekg/dns"
@@ -68,6 +69,12 @@ var cnameTestCases = []test.Case{
 			test.CNAME("www3.example.org. 1800	IN	CNAME www2.example.org."),
 		},
 	},
+	{
+		Qname: "dangling.example.org.", Qtype: dns.TypeA,
+		Answer: []dns.RR{
+			test.CNAME("dangling.example.org. 1800	IN	CNAME foo.example.org."),
+		},
+	},
 	{
 		Qname: "www3.example.org.", Qtype: dns.TypeA,
 		Answer: []dns.RR{
@@ -80,6 +87,59 @@ var cnameTestCases = []test.Case{
 	},
 }
 
+func TestLookupCNAMEExternal(t *testing.T) {
+	name := "example.org."
+	zone, err := Parse(strings.NewReader(dbExampleCNAME), name, "stdin")
+	if err != nil {
+		t.Fatalf("Expected no error when reading zone, got %q", err)
+	}
+	zone.Proxy = proxy.New([]string{"8.8.8.8:53"}) // TODO(point to local instance)
+
+	fm := File{Next: test.ErrorHandler(), Zones: Zones{Z: map[string]*Zone{name: zone}, Names: []string{name}}}
+	ctx := context.TODO()
+
+	for _, tc := range exernalTestCases {
+		m := tc.Msg()
+
+		rec := dnsrecorder.New(&test.ResponseWriter{})
+		_, err := fm.ServeDNS(ctx, rec, m)
+		if err != nil {
+			t.Errorf("Expected no error, got %v\n", err)
+			return
+		}
+
+		resp := rec.Msg
+		sort.Sort(test.RRSet(resp.Answer))
+		sort.Sort(test.RRSet(resp.Ns))
+		sort.Sort(test.RRSet(resp.Extra))
+
+		if !test.Header(t, tc, resp) {
+			t.Logf("%v\n", resp)
+			continue
+		}
+
+		if !test.Section(t, tc, test.Answer, resp.Answer) {
+			t.Logf("%v\n", resp)
+		}
+		if !test.Section(t, tc, test.Ns, resp.Ns) {
+			t.Logf("%v\n", resp)
+
+		}
+		if !test.Section(t, tc, test.Extra, resp.Extra) {
+			t.Logf("%v\n", resp)
+		}
+	}
+}
+
+var exernalTestCases = []test.Case{
+	{
+		Qname: "external.example.org.", Qtype: dns.TypeA,
+		Answer: []dns.RR{
+			test.CNAME("external.example.org. 1800	CNAME	www.example.net."),
+		},
+	},
+}
+
 const dbExampleCNAME = `
 $TTL    30M
 $ORIGIN example.org.
@@ -95,4 +155,5 @@ www3            IN      CNAME   www2
 www2            IN      CNAME   www1
 www1            IN      CNAME   www
 www             IN      CNAME   a
-dangling        IN      CNAME   foo`
+dangling        IN      CNAME   foo
+external        IN      CNAME   www.example.net.`
diff --git a/middleware/file/lookup.go b/middleware/file/lookup.go
index c47f1f5fa..50c99afb0 100644
--- a/middleware/file/lookup.go
+++ b/middleware/file/lookup.go
@@ -2,6 +2,7 @@ package file
 
 import (
 	"github.com/miekg/coredns/middleware/file/tree"
+	"github.com/miekg/coredns/request"
 
 	"github.com/miekg/dns"
 )
@@ -118,7 +119,7 @@ func (z *Zone) Lookup(qname string, qtype uint16, do bool) ([]dns.RR, []dns.RR,
 	// Found entire name.
 	if found && shot {
 
-		// DNAME...
+		// DNAME...?
 		if rrs := elem.Types(dns.TypeCNAME); len(rrs) > 0 && qtype != dns.TypeCNAME {
 			return z.searchCNAME(elem, rrs, qtype, do)
 		}
@@ -260,8 +261,16 @@ func (z *Zone) searchCNAME(elem *tree.Elem, rrs []dns.RR, qtype uint16, do bool)
 		}
 	}
 
-	elem, _ = z.Tree.Search(rrs[0].(*dns.CNAME).Target)
+	targetName := rrs[0].(*dns.CNAME).Target
+	elem, _ = z.Tree.Search(targetName)
+	println(targetName)
 	if elem == nil {
+		if !dns.IsSubDomain(z.origin, targetName) {
+			println(targetName, "is not a child of", z.origin)
+		}
+		st := request.Request{}
+		z.Proxy.Lookup(st, targetName, qtype)
+
 		return rrs, nil, nil, Success
 	}
 
@@ -279,8 +288,12 @@ Redo:
 				rrs = append(rrs, sigs...)
 			}
 		}
-		elem, _ = z.Tree.Search(cname[0].(*dns.CNAME).Target)
+		targetName := cname[0].(*dns.CNAME).Target
+		elem, _ = z.Tree.Search(targetName)
 		if elem == nil {
+			if !dns.IsSubDomain(z.origin, targetName) {
+				println(targetName, "is not a child of", z.origin)
+			}
 			return rrs, nil, nil, Success
 		}
 
diff --git a/middleware/file/setup.go b/middleware/file/setup.go
index b0946ed4b..d1349399f 100644
--- a/middleware/file/setup.go
+++ b/middleware/file/setup.go
@@ -8,6 +8,7 @@ import (
 
 	"github.com/miekg/coredns/core/dnsserver"
 	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/coredns/middleware/proxy"
 
 	"github.com/mholt/caddy"
 )
@@ -90,6 +91,7 @@ func fileParse(c *caddy.Controller) (Zones, error) {
 			}
 
 			noReload := false
+			prxy := proxy.Proxy{}
 			for c.NextBlock() {
 				t, _, e := TransferParse(c, false)
 				if e != nil {
@@ -98,6 +100,19 @@ func fileParse(c *caddy.Controller) (Zones, error) {
 				switch c.Val() {
 				case "no_reload":
 					noReload = true
+
+				case "upstream":
+					args := c.RemainingArgs()
+					if len(args) == 0 {
+						return Zones{}, c.ArgErr()
+					}
+					for i := 0; i < len(args); i++ {
+						h, p, e := net.SplitHostPort(args[i])
+						if e != nil && p == "" {
+							args[i] = h + ":53"
+						}
+					}
+					prxy = proxy.New(args)
 				}
 
 				for _, origin := range origins {
@@ -105,6 +120,7 @@ func fileParse(c *caddy.Controller) (Zones, error) {
 						z[origin].TransferTo = append(z[origin].TransferTo, t...)
 					}
 					z[origin].NoReload = noReload
+					z[origin].Proxy = prxy
 				}
 			}
 		}
diff --git a/middleware/file/zone.go b/middleware/file/zone.go
index 21571287d..0c0df1a1f 100644
--- a/middleware/file/zone.go
+++ b/middleware/file/zone.go
@@ -9,6 +9,7 @@ import (
 	"sync"
 
 	"github.com/miekg/coredns/middleware/file/tree"
+	"github.com/miekg/coredns/middleware/proxy"
 	"github.com/miekg/coredns/request"
 
 	"github.com/fsnotify/fsnotify"
@@ -31,6 +32,7 @@ type Zone struct {
 	NoReload       bool
 	reloadMu       sync.RWMutex
 	ReloadShutdown chan bool
+	Proxy          proxy.Proxy // Proxy for looking up names during the resolution process
 }
 
 // Apex contains the apex records of a zone: SOA, NS and their potential signatures.