5 files changed, 297 insertions, 0 deletions
diff --git a/plugin/chaos/README.md b/plugin/chaos/README.md
new file mode 100644
index 000000000..4c43590e5
--- /dev/null
+++ b/plugin/chaos/README.md
@@ -0,0 +1,46 @@
+# chaos
+
+The *chaos* plugin allows CoreDNS to respond to TXT queries in the CH class.
+
+This is useful for retrieving version or author information from the server.
+
+## Syntax
+
+~~~
+chaos [VERSION] [AUTHORS...]
+~~~
+
+* **VERSION** is the version to return. Defaults to `CoreDNS-<version>`, if not set.
+* **AUTHORS** is what authors to return. No default.
+
+Note that you have to make sure that this plugin will get actual queries for the
+following zones: `version.bind`, `version.server`, `authors.bind`, `hostname.bind` and
+`id.server`.
+
+## Examples
+
+Specify all the zones in full.
+
+~~~ corefile
+version.bind version.server authors.bind hostname.bind id.server {
+    chaos CoreDNS-001 info@coredns.io
+}
+~~~
+
+Or just default to `.`:
+
+~~~ corefile
+.  {
+    chaos CoreDNS-001 info@coredns.io
+}
+~~~
+
+And test with `dig`:
+
+~~~ txt
+% dig @localhost CH TXT version.bind
+...
+;; ANSWER SECTION:
+version.bind.		0	CH	TXT	"CoreDNS-001"
+...
+~~~
diff --git a/plugin/chaos/chaos.go b/plugin/chaos/chaos.go
new file mode 100644
index 000000000..c9811fbd0
--- /dev/null
+++ b/plugin/chaos/chaos.go
@@ -0,0 +1,62 @@
+// Package chaos implements a plugin that answer to 'CH version.bind TXT' type queries.
+package chaos
+
+import (
+	"os"
+
+	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/request"
+
+	"github.com/miekg/dns"
+	"golang.org/x/net/context"
+)
+
+// Chaos allows CoreDNS to reply to CH TXT queries and return author or
+// version information.
+type Chaos struct {
+	Next    plugin.Handler
+	Version string
+	Authors map[string]bool
+}
+
+// ServeDNS implements the plugin.Handler interface.
+func (c Chaos) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	state := request.Request{W: w, Req: r}
+	if state.QClass() != dns.ClassCHAOS || state.QType() != dns.TypeTXT {
+		return plugin.NextOrFailure(c.Name(), c.Next, ctx, w, r)
+	}
+
+	m := new(dns.Msg)
+	m.SetReply(r)
+
+	hdr := dns.RR_Header{Name: state.QName(), Rrtype: dns.TypeTXT, Class: dns.ClassCHAOS, Ttl: 0}
+	switch state.Name() {
+	default:
+		return c.Next.ServeDNS(ctx, w, r)
+	case "authors.bind.":
+		for a := range c.Authors {
+			m.Answer = append(m.Answer, &dns.TXT{Hdr: hdr, Txt: []string{trim(a)}})
+		}
+	case "version.bind.", "version.server.":
+		m.Answer = []dns.RR{&dns.TXT{Hdr: hdr, Txt: []string{trim(c.Version)}}}
+	case "hostname.bind.", "id.server.":
+		hostname, err := os.Hostname()
+		if err != nil {
+			hostname = "localhost"
+		}
+		m.Answer = []dns.RR{&dns.TXT{Hdr: hdr, Txt: []string{trim(hostname)}}}
+	}
+	state.SizeAndDo(m)
+	w.WriteMsg(m)
+	return 0, nil
+}
+
+// Name implements the Handler interface.
+func (c Chaos) Name() string { return "chaos" }
+
+func trim(s string) string {
+	if len(s) < 256 {
+		return s
+	}
+	return s[:255]
+}
diff --git a/plugin/chaos/chaos_test.go b/plugin/chaos/chaos_test.go
new file mode 100644
index 000000000..332d90381
--- /dev/null
+++ b/plugin/chaos/chaos_test.go
@@ -0,0 +1,80 @@
+package chaos
+
+import (
+	"testing"
+
+	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/plugin/pkg/dnsrecorder"
+	"github.com/coredns/coredns/plugin/test"
+
+	"github.com/miekg/dns"
+	"golang.org/x/net/context"
+)
+
+func TestChaos(t *testing.T) {
+	em := Chaos{
+		Version: version,
+		Authors: map[string]bool{"Miek Gieben": true},
+	}
+
+	tests := []struct {
+		next          plugin.Handler
+		qname         string
+		qtype         uint16
+		expectedCode  int
+		expectedReply string
+		expectedErr   error
+	}{
+		{
+			next:          test.NextHandler(dns.RcodeSuccess, nil),
+			qname:         "version.bind",
+			expectedCode:  dns.RcodeSuccess,
+			expectedReply: version,
+			expectedErr:   nil,
+		},
+		{
+			next:          test.NextHandler(dns.RcodeSuccess, nil),
+			qname:         "authors.bind",
+			expectedCode:  dns.RcodeSuccess,
+			expectedReply: "Miek Gieben",
+			expectedErr:   nil,
+		},
+		{
+			next:         test.NextHandler(dns.RcodeSuccess, nil),
+			qname:        "authors.bind",
+			qtype:        dns.TypeSRV,
+			expectedCode: dns.RcodeSuccess,
+			expectedErr:  nil,
+		},
+	}
+
+	ctx := context.TODO()
+
+	for i, tc := range tests {
+		req := new(dns.Msg)
+		if tc.qtype == 0 {
+			tc.qtype = dns.TypeTXT
+		}
+		req.SetQuestion(dns.Fqdn(tc.qname), tc.qtype)
+		req.Question[0].Qclass = dns.ClassCHAOS
+		em.Next = tc.next
+
+		rec := dnsrecorder.New(&test.ResponseWriter{})
+		code, err := em.ServeDNS(ctx, rec, req)
+
+		if err != tc.expectedErr {
+			t.Errorf("Test %d: Expected error %v, but got %v", i, tc.expectedErr, err)
+		}
+		if code != int(tc.expectedCode) {
+			t.Errorf("Test %d: Expected status code %d, but got %d", i, tc.expectedCode, code)
+		}
+		if tc.expectedReply != "" {
+			answer := rec.Msg.Answer[0].(*dns.TXT).Txt[0]
+			if answer != tc.expectedReply {
+				t.Errorf("Test %d: Expected answer %s, but got %s", i, tc.expectedReply, answer)
+			}
+		}
+	}
+}
+
+const version = "CoreDNS-001"
diff --git a/plugin/chaos/setup.go b/plugin/chaos/setup.go
new file mode 100644
index 000000000..2064f4eae
--- /dev/null
+++ b/plugin/chaos/setup.go
@@ -0,0 +1,55 @@
+package chaos
+
+import (
+	"github.com/coredns/coredns/core/dnsserver"
+	"github.com/coredns/coredns/plugin"
+
+	"github.com/mholt/caddy"
+)
+
+func init() {
+	caddy.RegisterPlugin("chaos", caddy.Plugin{
+		ServerType: "dns",
+		Action:     setup,
+	})
+
+}
+
+func setup(c *caddy.Controller) error {
+	version, authors, err := chaosParse(c)
+	if err != nil {
+		return plugin.Error("chaos", err)
+	}
+
+	dnsserver.GetConfig(c).AddPlugin(func(next plugin.Handler) plugin.Handler {
+		return Chaos{Next: next, Version: version, Authors: authors}
+	})
+
+	return nil
+}
+
+func chaosParse(c *caddy.Controller) (string, map[string]bool, error) {
+	// Set here so we pick up AppName and AppVersion that get set in coremain's init().
+	chaosVersion = caddy.AppName + "-" + caddy.AppVersion
+
+	version := ""
+	authors := make(map[string]bool)
+
+	for c.Next() {
+		args := c.RemainingArgs()
+		if len(args) == 0 {
+			return chaosVersion, nil, nil
+		}
+		if len(args) == 1 {
+			return args[0], nil, nil
+		}
+		version = args[0]
+		for _, a := range args[1:] {
+			authors[a] = true
+		}
+		return version, authors, nil
+	}
+	return version, authors, nil
+}
+
+var chaosVersion string
diff --git a/plugin/chaos/setup_test.go b/plugin/chaos/setup_test.go
new file mode 100644
index 000000000..6f3c13fb3
--- /dev/null
+++ b/plugin/chaos/setup_test.go
@@ -0,0 +1,54 @@
+package chaos
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/mholt/caddy"
+)
+
+func TestSetupChaos(t *testing.T) {
+	tests := []struct {
+		input              string
+		shouldErr          bool
+		expectedVersion    string // expected version.
+		expectedAuthor     string // expected author (string, although we get a map).
+		expectedErrContent string // substring from the expected error. Empty for positive cases.
+	}{
+		// positive
+		{
+			`chaos v2`, false, "v2", "", "",
+		},
+		{
+			`chaos v3 "Miek Gieben"`, false, "v3", "Miek Gieben", "",
+		},
+	}
+
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", test.input)
+		version, authors, err := chaosParse(c)
+
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %d: Expected error but found %s for input %s", i, err, test.input)
+		}
+
+		if err != nil {
+			if !test.shouldErr {
+				t.Errorf("Test %d: Expected no error but found one for input %s. Error was: %v", i, test.input, err)
+			}
+
+			if !strings.Contains(err.Error(), test.expectedErrContent) {
+				t.Errorf("Test %d: Expected error to contain: %v, found error: %v, input: %s", i, test.expectedErrContent, err, test.input)
+			}
+		}
+
+		if !test.shouldErr && version != test.expectedVersion {
+			t.Errorf("Chaos not correctly set for input %s. Expected: %s, actual: %s", test.input, test.expectedVersion, version)
+		}
+		if !test.shouldErr && authors != nil {
+			if _, ok := authors[test.expectedAuthor]; !ok {
+				t.Errorf("Chaos not correctly set for input %s. Expected: '%s', actual: '%s'", test.input, test.expectedAuthor, "Miek Gieben")
+			}
+		}
+	}
+}