gateway: fix further resolution of dnslink failures

A while ago, we noticed that if IpnsHostname failed to look up
a dnslink for a hostname in a Host header, it wouldn't respond
with an error, but instead just skip the Host header part and
carry on.

In the issue were this was flagged, the example was:
`_dnslink.tr.wikipedia-on-ipfs.org => /ipns/QmSomeKey`
This key had stopped to resolve, and thus the resolution of
/ipns/tr.wikipedia-on-ipfs.org would fail. Now you'd expect
an error response, but instead it'd happily continue processing
the request, disregarding the Host header, and allowing requests
to e.g. http://tr.wikipedia-on-ipfs.org/ipns/libp2p.io to succeed.

A previous patch (#4977) tried to work around this
issue by limiting the recursion depth of Host: header dnslink
resolutions to 1.

In this patch we start to correctly handle the initial resolution
error and stop processing the request, and we remove the earlier
workaround.

License: MIT
Signed-off-by: Lars Gierth <[email protected]>

Author: Lars Gierth

core/corehttp/gateway_test.go

@@ -169,8 +169,8 @@ func TestGatewayGet(t *testing.T) {
 		{"double.example.com", "/", http.StatusOK, "fnord"},
 		{"triple.example.com", "/", http.StatusOK, "fnord"},
 		{"working.example.com", "/ipfs/" + k, http.StatusNotFound, "ipfs resolve -r /ipns/working.example.com/ipfs/" + k + ": no link named \"ipfs\" under " + k + "\n"},
-		{"broken.example.com", "/", http.StatusNotFound, "ipfs resolve -r /ipns/broken.example.com/: " + namesys.ErrResolveFailed.Error() + "\n"},
-		{"broken.example.com", "/ipfs/" + k, http.StatusNotFound, "ipfs resolve -r /ipns/broken.example.com/ipfs/" + k + ": " + namesys.ErrResolveFailed.Error() + "\n"},
+		{"broken.example.com", "/", http.StatusNotFound, "ipfs resolve -r /ipns/broken.example.com: " + namesys.ErrResolveFailed.Error() + "\n"},
+		{"broken.example.com", "/ipfs/" + k, http.StatusNotFound, "ipfs resolve -r /ipns/broken.example.com: " + namesys.ErrResolveFailed.Error() + "\n"},
 	} {
 		var c http.Client
 		r, err := http.NewRequest("GET", ts.URL+test.path, nil)

core/corehttp/ipns_hostname.go

@@ -2,12 +2,12 @@ package corehttp
 
 import (
 	"context"
+	"fmt"
 	"net"
 	"net/http"
 	"strings"
 
 	core "github.com/ipfs/go-ipfs/core"
-	nsopts "github.com/ipfs/go-ipfs/namesys/opts"
 
 	isd "gx/ipfs/QmZmmuAXgX73UQmX1jRKjTGmjzq24Jinqkq8vzkBtno4uX/go-is-domain"
 )
@@ -25,10 +25,15 @@ func IPNSHostnameOption() ServeOption {
 			host := strings.SplitN(r.Host, ":", 2)[0]
 			if len(host) > 0 && isd.IsDomain(host) {
 				name := "/ipns/" + host
-				if _, err := n.Namesys.Resolve(ctx, name, nsopts.Depth(1)); err == nil {
-					r.Header.Set("X-Ipns-Original-Path", r.URL.Path)
-					r.URL.Path = name + r.URL.Path
+				_, err := n.Namesys.Resolve(ctx, name)
+				if err != nil {
+					w.WriteHeader(404)
+					fmt.Fprintf(w, "ipfs resolve -r %s: %s\n", name, err)
+					return
 				}
+
+				r.Header.Set("X-Ipns-Original-Path", r.URL.Path)
+				r.URL.Path = name + r.URL.Path
 			}
 			childMux.ServeHTTP(w, r)
 		})