From 5e94b9d91816b9b065b43579c5fa9e81b55f992c Mon Sep 17 00:00:00 2001
From: Henrique Dias <hacdias@gmail.com>
Date: Tue, 16 May 2023 12:27:23 +0200
Subject: [PATCH] feat(gateway): redirect ipns b58mh to cid (#236)

---
 gateway/gateway_test.go | 27 +++++++++++++++++++
 gateway/handler.go      | 57 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+)

diff --git a/gateway/gateway_test.go b/gateway/gateway_test.go
index 4bf1c3da4..ef14eeeba 100644
--- a/gateway/gateway_test.go
+++ b/gateway/gateway_test.go
@@ -546,3 +546,30 @@ func TestGoGetSupport(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, http.StatusOK, res.StatusCode)
 }
+
+func TestIpnsBase58MultihashRedirect(t *testing.T) {
+	ts, _, _ := newTestServerAndNode(t, nil)
+	t.Logf("test server url: %s", ts.URL)
+
+	t.Run("ED25519 Base58-encoded key", func(t *testing.T) {
+		t.Parallel()
+
+		req, err := http.NewRequest(http.MethodGet, ts.URL+"/ipns/12D3KooWRBy97UB99e3J6hiPesre1MZeuNQvfan4gBziswrRJsNK?keep=query", nil)
+		assert.Nil(t, err)
+
+		res, err := doWithoutRedirect(req)
+		assert.Nil(t, err)
+		assert.Equal(t, "/ipns/k51qzi5uqu5dlvj2baxnqndepeb86cbk3ng7n3i46uzyxzyqj2xjonzllnv0v8?keep=query", res.Header.Get("Location"))
+	})
+
+	t.Run("RSA Base58-encoded key", func(t *testing.T) {
+		t.Parallel()
+
+		req, err := http.NewRequest(http.MethodGet, ts.URL+"/ipns/QmcJM7PRfkSbcM5cf1QugM5R37TLRKyJGgBEhXjLTB8uA2?keep=query", nil)
+		assert.Nil(t, err)
+
+		res, err := doWithoutRedirect(req)
+		assert.Nil(t, err)
+		assert.Equal(t, "/ipns/k2k4r8ol4m8kkcqz509c1rcjwunebj02gcnm5excpx842u736nja8ger?keep=query", res.Header.Get("Location"))
+	})
+}
diff --git a/gateway/handler.go b/gateway/handler.go
index 4da858c10..8ce4ff7eb 100644
--- a/gateway/handler.go
+++ b/gateway/handler.go
@@ -19,6 +19,8 @@ import (
 	ipath "github.com/ipfs/boxo/coreiface/path"
 	cid "github.com/ipfs/go-cid"
 	logging "github.com/ipfs/go-log"
+	"github.com/libp2p/go-libp2p/core/peer"
+	"github.com/multiformats/go-multibase"
 	prometheus "github.com/prometheus/client_golang/prometheus"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/trace"
@@ -204,6 +206,10 @@ func (i *handler) getOrHeadHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if handleIpnsB58mhToCidRedirection(w, r) {
+		return
+	}
+
 	contentPath := ipath.New(r.URL.Path)
 	ctx := context.WithValue(r.Context(), ContentPathKey, contentPath)
 	r = r.WithContext(ctx)
@@ -728,6 +734,57 @@ func handleServiceWorkerRegistration(r *http.Request) (err *ErrorResponse) {
 	return nil
 }
 
+// handleIpnsB58mhToCidRedirection redirects from /ipns/b58mh to /ipns/cid in
+// the most cost-effective way.
+func handleIpnsB58mhToCidRedirection(w http.ResponseWriter, r *http.Request) bool {
+	if _, dnslink := r.Context().Value(DNSLinkHostnameKey).(string); dnslink {
+		// For DNSLink hostnames, do not perform redirection in order to not break
+		// website. For example, if `example.net` is backed by `/ipns/base58`, we
+		// must NOT redirect to `example.net/ipns/base36-id`.
+		return false
+	}
+
+	if w.Header().Get("Location") != "" {
+		// Ignore this if there is already a redirection in place. This happens
+		// if there is a subdomain redirection. In that case, the path is already
+		// converted to CIDv1.
+		return false
+	}
+
+	pathParts := strings.Split(r.URL.Path, "/")
+	if len(pathParts) < 3 {
+		return false
+	}
+
+	if pathParts[1] != "ipns" {
+		return false
+	}
+
+	id, err := peer.Decode(pathParts[2])
+	if err != nil {
+		return false
+	}
+
+	// Convert the peer ID to a CIDv1.
+	cid := peer.ToCid(id)
+
+	// Encode CID in base36 to match the subdomain URLs.
+	encodedCID, err := cid.StringOfBase(multibase.Base36)
+	if err != nil {
+		return false
+	}
+
+	// If the CID was already encoded, do not redirect.
+	if encodedCID == pathParts[2] {
+		return false
+	}
+
+	pathParts[2] = encodedCID
+	r.URL.Path = strings.Join(pathParts, "/")
+	http.Redirect(w, r, r.URL.String(), http.StatusFound)
+	return true
+}
+
 // Attempt to fix redundant /ipfs/ namespace as long as resulting
 // 'intended' path is valid.  This is in case gremlins were tickled
 // wrong way and user ended up at /ipfs/ipfs/{cid} or /ipfs/ipns/{id}