fix: limit SW registration to content root

Introduces hardening proposed in:
ipfs#4025 (comment)

License: MIT
Signed-off-by: Marcin Rataj <lidel@lidel.org>

core/corehttp/gateway_handler.go

@@ -9,6 +9,7 @@ import (
 	"net/url"
 	"os"
 	gopath "path"
+	"regexp"
 	"runtime/debug"
 	"strings"
 	"time"
@@ -155,6 +156,18 @@ func (i *gatewayHandler) getOrHeadHandler(w http.ResponseWriter, r *http.Request
 		ipnsHostname = true
 	}
 
+	// Service Worker registration request
+	if r.Header.Get("Service-Worker") == "script" {
+		// Disallow Service Worker registration on namespace roots
+		// https://github.com/ipfs/go-ipfs/issues/4025
+		matched, _ := regexp.MatchString(`^/ip[fn]s/[^/]+$`, r.URL.Path)
+		if matched {
+			err := fmt.Errorf("registration is not allowed for this scope")
+			webError(w, "navigator.serviceWorker", err, http.StatusBadRequest)
+			return
+		}
+	}
+
 	parsedPath := ipath.New(urlPath)
 	if err := parsedPath.IsValid(); err != nil {
 		webError(w, "invalid ipfs path", err, http.StatusBadRequest)

test/sharness/t0110-gateway.sh

@@ -36,6 +36,13 @@ test_expect_success "GET IPFS path with explicit filename succeeds with proper h
   grep -F \"Content-Disposition: inline; filename*=UTF-8''test%D1%82%D0%B5%D1%81%D1%82\" actual_headers
 "
 
+# https://github.com/ipfs/go-ipfs/issues/4025#issuecomment-342250616
+test_expect_success "GET for Service Worker registration outside of an IPFS content root errors" "
+  curl -H 'Service-Worker: script'  -svX GET 'http://127.0.0.1:$port/ipfs/$HASH?filename=sw.js' > curl_sw_out 2>&1 &&
+  grep 'HTTP/1.1 400 Bad Request' curl_sw_out &&
+  grep 'navigator.serviceWorker: registration is not allowed for this scope' curl_sw_out
+"
+
 test_expect_success "GET IPFS path output looks good" '
   test_cmp expected actual &&
   rm actual