add automatic hostname redirection

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

Author: Stebalien

core/corehttp/gateway_handler.go

@@ -36,14 +36,20 @@ type GatewaySpec struct {
 	// the gateway logic.
 	PathPrefixes []string
 
-	// SupportsSubdomains indicates whether or not this gateway supports
-	// requests of the form http://CID.ipfs.GATEWAY/...
-	SupportsSubdomains bool
+	// UseSubdomains indicates whether or not this gateway uses subdomains
+	// for IPFS resources instead of paths. That is: http://CID.ipfs.GATEWAY/...
+	//
+	// If this flag is set, any /ipns/$id and/or /ipfs/$id paths in PathPrefixes
+	// will be permanently redirected to http://$id.[ipns|ipfs].$gateway/.
+	//
+	// We do not support using both paths and subdomains for a single domain
+	// for security reasons.
+	UseSubdomains bool
 }
 
 var DefaultGatewaySpec = GatewaySpec{
-	PathPrefixes:       []string{ipfsPathPrefix, ipnsPathPrefix, "/api/"},
-	SupportsSubdomains: true,
+	PathPrefixes:  []string{ipfsPathPrefix, ipnsPathPrefix, "/api/"},
+	UseSubdomains: false,
 }
 
 // TODO(steb): Configurable

core/corehttp/hostname.go

@@ -2,6 +2,7 @@ package corehttp
 
 import (
 	"context"
+	"fmt"
 	"net"
 	"net/http"
 	"strings"
@@ -21,51 +22,118 @@ func HostnameOption() ServeOption {
 			ctx, cancel := context.WithCancel(n.Context())
 			defer cancel()
 
+			// Unfortunately, many (well, ipfs.io) gateways use
+			// DNSLink so if we blindly rewrite with DNSLink, we'll
+			// break /ipfs links.
+			//
+			// We fix this by maintaining a list of known gateways
+			// and the paths that they serve "gateway" content on.
+			// That way, we can use DNSLink for everything else.
+			//
+			// TODO: We wouldn't need _any_ of this if we
+			// supported transparent symlink resolution on
+			// the gateway. If we had that, such gateways could add
+			// symlinks to `/ipns`, `/ipfs`, `/api`, etc. to their
+			// home directories. That way, `/ipfs/QmA/ipfs/QmB`
+			// would "just work". Should we try this?
+
 			// Is this one of our "known gateways"?
 			if gw, ok := KnownGateways[r.Host]; ok {
+				// This is a known gateway but we're not using
+				// the subdomain feature.
+
+				// Does this gateway _handle_ this path?
 				if hasPrefix(r.URL.Path, gw.PathPrefixes...) {
+					// It does.
+
+					// Does this gateway use subdomains?
+					if gw.UseSubdomains {
+						// Yes, redirect if applicable (pretty much everything except `/api`).
+						if newURL, ok := toSubdomainURL(r.Host, r.URL.Path); ok {
+							http.Redirect(
+								w, r, newURL, http.StatusMovedPermanently,
+							)
+							return
+						}
+					}
 					childMux.ServeHTTP(w, r)
 					return
 				}
 			} else if host, pathPrefix, ok := parseSubdomains(r.Host); ok {
-				if gw, ok := KnownGateways[host]; ok && gw.SupportsSubdomains {
-					// Always handle this with the gateway.
-					// We don't care if it's one of the
-					// valid path-prefixes.
+				// Looks like we're using subdomains.
+
+				// Again, is this a known gateway that supports subdomains?
+				if gw, ok := KnownGateways[host]; ok && gw.UseSubdomains {
 
+					// Yes, serve the request (and rewrite the path to not use subdomains).
 					r.URL.Path = pathPrefix + r.URL.Path
 					childMux.ServeHTTP(w, r)
 					return
 				}
 			}
 
+			// We don't have a known gateway. Fallback on dnslink.
 			host := strings.SplitN(r.Host, ":", 2)[0]
-			if len(host) == 0 || !isd.IsDomain(host) {
-				childMux.ServeHTTP(w, r)
-				return
-			}
+			if len(host) > 0 && isd.IsDomain(host) {
+				name := "/ipns/" + host
+				_, err := n.Namesys.Resolve(ctx, name, nsopts.Depth(1))
+				if err == nil || err == namesys.ErrResolveRecursion {
+					// The domain supports dnslink, rewrite.
+					r.URL.Path = name + r.URL.Path
+				}
+			} // else, just treat it as a gateway, I guess.
 
-			name := "/ipns/" + host
-			_, err := n.Namesys.Resolve(ctx, name, nsopts.Depth(1))
-			if err == nil || err == namesys.ErrResolveRecursion {
-				r.URL.Path = name + r.URL.Path
-			}
 			childMux.ServeHTTP(w, r)
 		})
 		return childMux, nil
 	}
 }
 
+func isSubdomainNamespace(ns string) bool {
+	switch ns {
+	case "ipfs", "ipns", "p2p", "ipld":
+		return true
+	default:
+		return false
+	}
+}
+
+// Parses a subdomain-based URL and returns it's components
 func parseSubdomains(host string) (newHost, pathPrefix string, ok bool) {
 	parts := strings.SplitN(host, ".", 3)
-	if len(parts) < 3 {
+	if len(parts) < 3 || !isSubdomainNamespace(parts[1]) {
 		return "", "", false
 	}
-	switch parts[1] {
-	case "ipfs", "ipns", "p2p":
-		return parts[2], "/" + parts[1] + "/" + parts[0], true
+	return parts[2], "/" + parts[1] + "/" + parts[0], true
+}
+
+// Converts a host/path to a subdomain-based URL, if applicable.
+func toSubdomainURL(host, path string) (url string, ok bool) {
+	parts := strings.SplitN(path, "/", 4)
+
+	var ns, object, rest string
+	switch len(parts) {
+	case 4:
+		rest = parts[3]
+		fallthrough
+	case 3:
+		ns = parts[1]
+		object = parts[2]
+	default:
+		return "", false
+	}
+
+	if !isSubdomainNamespace(ns) {
+		return "", false
 	}
-	return "", "", false
+
+	return fmt.Sprintf(
+		"http://%s.%s.%s/%s",
+		object,
+		ns,
+		host,
+		rest,
+	), true
 }
 
 func hasPrefix(s string, prefixes ...string) bool {