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Fix EDNS0 compliance (#2357)

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* Fix EDNS0 compliance

Do SizeAndDo in the server (ScrubWriter) and remove all uses of this
from the plugins. Also *always* do it. This is to get into compliance
for https://dnsflagday.net/.

The pkg/edns0 now exports the EDNS0 options we understand; this is
exported to allow plugins add things there. The *rewrite* plugin used
this to add custom EDNS0 option codes that the server needs to
understand.

This also needs a new release of miekg/dns because it triggered a
race-condition that was basicly there forever.

See:
* https://github.com/miekg/dns/issues/857
* https://github.com/miekg/dns/pull/859

Running a test instance and pointing the https://ednscomp.isc.org/ednscomp
to it shows the tests are now fixed:

~~~
EDNS Compliance Tester
Checking: 'miek.nl' as at 2018-12-01T17:53:15Z

miek.nl. @147.75.204.203 (drone.coredns.io.): dns=ok edns=ok edns1=ok edns@512=ok ednsopt=ok edns1opt=ok do=ok ednsflags=ok docookie=ok edns512tcp=ok optlist=ok
miek.nl. @2604:1380:2002:a000::1 (drone.coredns.io.): dns=ok edns=ok edns1=ok edns@512=ok ednsopt=ok edns1opt=ok do=ok ednsflags=ok docookie=ok edns512tcp=ok optlist=ok

All Ok
Codes
ok - test passed.
~~~

Signed-off-by: Miek Gieben <miek@miek.nl>

Signed-off-by: Miek Gieben <miek@miek.nl>

* typos in comments

Signed-off-by: Miek Gieben <miek@miek.nl>
This commit is contained in:
Miek Gieben
2018-12-06 21:18:11 +00:00
committed by GitHub
parent f51c110511
commit fc667b98e0
16 changed files with 113 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
request/edns0.go Normal file
View File

@@ -0,0 +1,31 @@
package request
import (
"github.com/coredns/coredns/plugin/pkg/edns"
"github.com/miekg/dns"
)
func supportedOptions(o []dns.EDNS0) []dns.EDNS0 {
var supported = make([]dns.EDNS0, 0, 3)
// For as long as possible try avoid looking up in the map, because that need an Rlock.
for _, opt := range o {
switch code := opt.Option(); code {
case dns.EDNS0NSID:
fallthrough
case dns.EDNS0EXPIRE:
fallthrough
case dns.EDNS0COOKIE:
fallthrough
case dns.EDNS0TCPKEEPALIVE:
fallthrough
case dns.EDNS0PADDING:
supported = append(supported, opt)
default:
if edns.SupportedOption(code) {
supported = append(supported, opt)
}
}
}
return supported
}

12
request/request.go
View File

@@ -194,7 +194,7 @@ func (r *Request) Size() int {
// SizeAndDo adds an OPT record that the reflects the intent from request.
// The returned bool indicated if an record was found and normalised.
func (r *Request) SizeAndDo(m *dns.Msg) bool {
o := r.Req.IsEdns0() // TODO(miek): speed this up
o := r.Req.IsEdns0()
if o == nil {
return false
}
@@ -208,6 +208,10 @@ func (r *Request) SizeAndDo(m *dns.Msg) bool {
mo.SetUDPSize(o.UDPSize())
mo.Hdr.Ttl &= 0xff00 // clear flags
if len(o.Option) > 0 {
o.Option = supportedOptions(o.Option)
}
if odo {
mo.SetDo()
}
@@ -219,6 +223,10 @@ func (r *Request) SizeAndDo(m *dns.Msg) bool {
o.SetVersion(0)
o.Hdr.Ttl &= 0xff00 // clear flags
if len(o.Option) > 0 {
o.Option = supportedOptions(o.Option)
}
if odo {
o.SetDo()
}
@@ -305,7 +313,6 @@ func (r *Request) Scrub(reply *dns.Msg) *dns.Msg {
}
if rl <= size {
r.SizeAndDo(reply)
return reply
}
@@ -341,7 +348,6 @@ func (r *Request) Scrub(reply *dns.Msg) *dns.Msg {
// this extra m-1 step does make it fit in the client's buffer however.
}
r.SizeAndDo(reply)
reply.Truncated = true
return reply
}

8
request/request_test.go
View File

@@ -123,10 +123,6 @@ func TestRequestScrubExtraEdns0(t *testing.T) {
if reply.Truncated {
t.Errorf("Want scrub to not set truncated bit")
}
opt := reply.Extra[len(reply.Extra)-1]
if opt.Header().Rrtype != dns.TypeOPT {
t.Errorf("Last RR must be OPT record")
}
}
func TestRequestScrubExtraRegression(t *testing.T) {
@@ -153,10 +149,6 @@ func TestRequestScrubExtraRegression(t *testing.T) {
if reply.Truncated {
t.Errorf("Want scrub to not set truncated bit")
}
opt := reply.Extra[len(reply.Extra)-1]
if opt.Header().Rrtype != dns.TypeOPT {
t.Errorf("Last RR must be OPT record")
}
}
func TestTruncation(t *testing.T) {

2
request/writer.go
View File

@@ -15,6 +15,8 @@ func NewScrubWriter(req *dns.Msg, w dns.ResponseWriter) *ScrubWriter { return &S
// scrub on the message m and will then write it to the client.
func (s *ScrubWriter) WriteMsg(m *dns.Msg) error {
state := Request{Req: s.req, W: s.ResponseWriter}
n := state.Scrub(m)
state.SizeAndDo(n)
return s.ResponseWriter.WriteMsg(n)
}