Handle multiple CNAME resolve and debug log http redirect (#675)

* Handle multiple CNAME resolve and debug log http redirect

* Add root resolver test

---------

Co-authored-by: Edward J <[email protected]>

Author: edwardrf

src/pkg/cli/cert.go

@@ -49,6 +49,10 @@ var (
 			TLSHandshakeTimeout:   10 * time.Second,
 			ExpectContinueTimeout: 1 * time.Second,
 		},
+		CheckRedirect: func(req *http.Request, via []*http.Request) error {
+			term.Debugf("Redirecting from %v to %v", via[len(via)-1].URL, req.URL)
+			return nil
+		},
 	}
 )
 

src/pkg/dns/resolver.go

@@ -2,6 +2,7 @@ package dns
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"math/rand"
 	"net"
@@ -37,15 +38,19 @@ var rootServers = []*net.NS{
 }
 
 func (r RootResolver) LookupIPAddr(ctx context.Context, domain string) ([]net.IPAddr, error) {
-	ips, err := r.getResolver(ctx, domain).LookupIPAddr(ctx, domain)
-	if err != nil {
-		if err, ok := err.(ErrCNAMEFound); ok {
-			return r.getResolver(ctx, err.CNAME()).LookupIPAddr(ctx, err.CNAME())
-		} else {
-			return nil, err
+	for i := 0; i < 10; i++ {
+		ips, err := r.getResolver(ctx, domain).LookupIPAddr(ctx, domain)
+		if err != nil {
+			if cnameErr, ok := err.(ErrCNAMEFound); ok {
+				domain = cnameErr.CNAME()
+				continue
+			} else {
+				return nil, err
+			}
 		}
+		return ips, nil
 	}
-	return ips, nil
+	return nil, errors.New("too many CNAME lookups")
 }
 
 func (r RootResolver) LookupCNAME(ctx context.Context, domain string) (string, error) {

src/pkg/dns/resolver_integration_test.go

@@ -43,4 +43,15 @@ func TestRootResolver(t *testing.T) {
 			t.Errorf("Expected same IP addresses, got %v <> %v", ips, nIPs)
 		}
 	})
+
+	t.Run("LookupIPAddr follows multiple CNAME redirects", func(t *testing.T) {
+		r := RootResolver{}
+		ips, err := r.LookupIPAddr(context.Background(), "cname-a.gnafed.click")
+		if err != nil {
+			t.Errorf("Expected no error, got %v", err)
+		}
+		if !SameIPs(IpAddrsToIPs(ips), []net.IP{net.ParseIP("1.2.3.4")}) {
+			t.Errorf("Expected IP address 1.2.3.4 got %v", ips)
+		}
+	})
 }