From 474f012b4dc15e836c82e2e9ff1371a43ee4f3eb Mon Sep 17 00:00:00 2001
From: Julien Pivotto <roidelapluie@inuits.eu>
Date: Tue, 16 Jun 2020 01:07:17 +0200
Subject: [PATCH] Add support for IDNA

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>
---
 prober/dns.go        |  9 +++++++--
 prober/utils.go      | 18 ++++++++++++++++++
 prober/utils_test.go | 20 ++++++++++++++++++++
 3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/prober/dns.go b/prober/dns.go
index edb5b2820..cf6a36d84 100644
--- a/prober/dns.go
+++ b/prober/dns.go
@@ -209,12 +209,17 @@ func ProbeDNS(ctx context.Context, target string, module config.Module, registry
 		}
 	}
 
+	idnTarget, err := internationalizeDNSTarget(logger, module.DNS.QueryName)
+	if err != nil {
+		level.Error(logger).Log("msg", "IDN conversion failed", "err", err)
+		return false
+	}
+
 	msg := new(dns.Msg)
 	msg.Id = dns.Id()
 	msg.RecursionDesired = true
 	msg.Question = make([]dns.Question, 1)
-	msg.Question[0] = dns.Question{dns.Fqdn(module.DNS.QueryName), qt, qc}
-
+	msg.Question[0] = dns.Question{dns.Fqdn(idnTarget), qt, qc}
 	level.Info(logger).Log("msg", "Making DNS query", "target", target, "dial_protocol", dialProtocol, "query", module.DNS.QueryName, "type", qt, "class", qc)
 	timeoutDeadline, _ := ctx.Deadline()
 	client.Timeout = time.Until(timeoutDeadline)
diff --git a/prober/utils.go b/prober/utils.go
index 98c9152ea..76b62e60d 100644
--- a/prober/utils.go
+++ b/prober/utils.go
@@ -22,6 +22,7 @@ import (
 
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/log/level"
+	"golang.org/x/net/idna"
 
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -55,6 +56,12 @@ func chooseProtocol(ctx context.Context, IPProtocol string, fallbackIPProtocol b
 		fallbackProtocol = "ip6"
 	}
 
+	target, err = internationalizeDNSTarget(logger, target)
+	if err != nil {
+		level.Error(logger).Log("msg", "IDN conversion failed", "err", err)
+		return nil, 0.0, err
+	}
+
 	level.Info(logger).Log("msg", "Resolving target address", "ip_protocol", IPProtocol)
 	resolveStart := time.Now()
 
@@ -119,3 +126,14 @@ func ipHash(ip net.IP) float64 {
 	h.Write(ip)
 	return float64(h.Sum32())
 }
+
+func internationalizeDNSTarget(logger log.Logger, target string) (string, error) {
+	idnaTarget, err := idna.ToASCII(target)
+	if err != nil {
+		return target, fmt.Errorf("error while internationalizing target: %w", err)
+	}
+	if idnaTarget != target {
+		level.Info(logger).Log("msg", "Target address internationalized", "ascii", idnaTarget)
+	}
+	return idnaTarget, nil
+}
diff --git a/prober/utils_test.go b/prober/utils_test.go
index 2ac38eebe..7cc3d734d 100644
--- a/prober/utils_test.go
+++ b/prober/utils_test.go
@@ -171,3 +171,23 @@ func TestChooseProtocol(t *testing.T) {
 		t.Error("without fallback it should not answer")
 	}
 }
+
+func TestChooseProtocolIDNA(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping network dependent test")
+	}
+	var (
+		ctx      = context.Background()
+		registry = prometheus.NewPedanticRegistry()
+		w        = log.NewSyncWriter(os.Stderr)
+		logger   = log.NewLogfmtLogger(w)
+	)
+
+	ip, _, err := chooseProtocol(ctx, "ip4", true, "www.académie-française.fr", registry, logger)
+	if err != nil {
+		t.Error(err)
+	}
+	if ip == nil || ip.IP.To4() == nil {
+		t.Error("it should answer")
+	}
+}