fix: additional checks for CORS XHR when dnslink is enabled

Dnslink lookup is disabled by default, but if user opted-in to it,
many websites were broken due to invalid gateway redirects.

This change fixes regression introduced by:
#511
and adds tests to guard against the problem in future.

add-on/src/lib/dns-link.js

@@ -39,21 +39,22 @@ module.exports = function createDnsLink (getState) {
       let dnslink = cache.get(fqdn)
       if (typeof dnslink === 'undefined') {
         try {
-          console.info('dnslink cache miss for: ' + fqdn)
+          console.info(`[ipfs-companion] dnslink cache miss for '${fqdn}', running DNS TXT lookup`)
           dnslink = dnsLink.readDnslinkFromTxtRecord(fqdn)
           if (dnslink) {
             cache.set(fqdn, dnslink)
-            console.info(`Resolved dnslink: '${fqdn}' -> '${dnslink}'`)
+            console.info(`[ipfs-companion] found dnslink: '${fqdn}' -> '${dnslink}'`)
           } else {
             cache.set(fqdn, false)
-            console.info(`Resolved NO dnslink for '${fqdn}'`)
+            console.info(`[ipfs-companion] found NO dnslink for '${fqdn}'`)
           }
         } catch (error) {
-          console.error(`Error in dnslinkLookupAndOptionalRedirect for '${fqdn}'`)
+          console.error(`[ipfs-companion] Error in dnslinkLookupAndOptionalRedirect for '${fqdn}'`)
           console.error(error)
         }
       } else {
-        console.info(`Resolved via cached dnslink: '${fqdn}' -> '${dnslink}'`)
+        // Most of the time we will hit cache, which makes below line is too noisy
+        // console.info(`[ipfs-companion] using cached dnslink: '${fqdn}' -> '${dnslink}'`)
       }
       return dnslink
     },
@@ -84,6 +85,17 @@ module.exports = function createDnsLink (getState) {
       }
     },
 
+    validDnslinkRedirect (url) {
+      if (getState().dnslink && !url.pathname.startsWith('/ipfs/') && !url.pathname.startsWith('/ipns/')) {
+        const fqdn = url.hostname
+        const dnslink = dnsLink.cachedDnslinkLookup(fqdn)
+        if (dnslink) {
+          return true
+        }
+      }
+      return false
+    },
+
     redirectToIpnsPath (originalUrl) {
       // TODO: redirect to `ipns://` if hasNativeProtocolHandler === true
       const fqdn = originalUrl.hostname

add-on/src/lib/ipfs-request.js

@@ -43,11 +43,14 @@ function createRequestModifier (getState, dnsLink, ipfsPathValidator, runtime) {
         }
         // Detect valid /ipfs/ and /ipns/ on any site
         if (ipfsPathValidator.publicIpfsOrIpnsResource(request.url) && isSafeToRedirect(request, runtime)) {
-          return redirectToGateway(request.url, state)
+          return redirectToGateway(request.url, state, dnsLink)
         }
         // Look for dnslink in TXT records of visited sites
-        if (state.dnslink && dnsLink.isDnslookupSafeForURL(request.url) && isSafeToRedirect(request, runtime)) {
-          return dnsLink.dnslinkLookupAndOptionalRedirect(request.url)
+        if (state.dnslink && dnsLink.isDnslookupSafeForURL(request.url)) {
+          const dnslinkRedirect = dnsLink.dnslinkLookupAndOptionalRedirect(request.url)
+          if (dnslinkRedirect && isSafeToRedirect(request, runtime)) {
+            return dnslinkRedirect
+          }
         }
       }
     },
@@ -99,7 +102,7 @@ function createRequestModifier (getState, dnsLink, ipfsPathValidator, runtime) {
       if (onHeadersReceivedRedirect.has(request.requestId)) {
         const state = getState()
         onHeadersReceivedRedirect.delete(request.requestId)
-        return redirectToGateway(request.url, state)
+        return redirectToGateway(request.url, state, dnsLink)
       }
     },
 
@@ -151,10 +154,14 @@ function postNormalizationSkip (state, request) {
   return false
 }
 
-function redirectToGateway (requestUrl, state) {
+function redirectToGateway (requestUrl, state, dnsLink) {
   // TODO: redirect to `ipfs://` if hasNativeProtocolHandler === true
-  const gwUrl = state.ipfsNodeType === 'embedded' ? state.pubGwURL : state.gwURL
   const url = new URL(requestUrl)
+  if (state.dnslink && dnsLink.validDnslinkRedirect(url)) {
+    // if no known path prefix, then it is a website with dnslink
+    return dnsLink.redirectToIpnsPath(url)
+  }
+  const gwUrl = state.ipfsNodeType === 'embedded' ? state.pubGwURL : state.gwURL
   url.protocol = gwUrl.protocol
   url.host = gwUrl.host
   url.port = gwUrl.port
@@ -210,7 +217,7 @@ function normalizedRedirectingProtocolRequest (request, pubGwUrl) {
   path = path.replace(/^#dweb:\//i, '/') // dweb:/ipfs/Qm → /ipfs/Qm
   path = path.replace(/^#ipfs:\/\//i, '/ipfs/') // ipfs://Qm → /ipfs/Qm
   path = path.replace(/^#ipns:\/\//i, '/ipns/') // ipns://Qm → /ipns/Qm
-  console.log(`oldPath: '${oldPath}' new: '${path}'`)
+  // console.log(`oldPath: '${oldPath}' new: '${path}'`)
   if (oldPath !== path && IsIpfs.path(path)) {
     return { redirectUrl: urlAtPublicGw(path, pubGwUrl) }
   }

test/functional/lib/ipfs-request.test.js

@@ -432,6 +432,59 @@ describe('modifyRequest.onBeforeRequest', function () {
           expect(modifyRequest.onBeforeRequest(request)).to.equal(undefined)
         })
       })
+
+      describe('request to FQDN with dnslink experiment enabled', function () {
+        let activeGateway
+        beforeEach(function () {
+          // pretend API is online and we can do dns lookups with it
+          state.dnslink = true
+          state.peerCount = 1
+          // embedded node (js-ipfs) defaults to public gw
+          activeGateway = (state.ipfsNodeType === 'external' ? state.gwURLString : state.pubGwURLString)
+        })
+        it('should be redirected to active gateway if dnslink exists', function () {
+          // stub the existence of valid dnslink
+          const fqdn = 'ipfs.git.sexy'
+          dnsLink.readDnslinkFromTxtRecord = sinon.stub().withArgs(fqdn).returns('/ipfs/Qmazvovg6Sic3m9igZMKoAPjkiVZsvbWWc8ZvgjjK1qMss')
+          //
+          const request = url2request('http://ipfs.git.sexy/index.html?argTest#hashTest')
+          expect(modifyRequest.onBeforeRequest(request).redirectUrl).to.equal(activeGateway + '/ipns/ipfs.git.sexy/index.html?argTest#hashTest')
+        })
+        it('should be redirected to active gateway if fetched from the same origin and redirect is enabled in non-Firefox', function () {
+          // stub the existence of valid dnslink
+          const fqdn = 'ipfs.git.sexy'
+          dnsLink.readDnslinkFromTxtRecord = sinon.stub().withArgs(fqdn).returns('/ipfs/Qmazvovg6Sic3m9igZMKoAPjkiVZsvbWWc8ZvgjjK1qMss')
+          //
+          runtime.isFirefox = false
+          const xhrRequest = {url: 'http://ipfs.git.sexy/index.html?argTest#hashTest', type: 'xmlhttprequest', initiator: 'https://www.nasa.gov/foo.html', requestId: fakeRequestId()}
+          expect(modifyRequest.onBeforeRequest(xhrRequest).redirectUrl).to.equal(activeGateway + '/ipns/ipfs.git.sexy/index.html?argTest#hashTest')
+        })
+        it('should be redirected to active gateway via late redirect if dnslink exists and XHR is cross-origin in Firefox', function () {
+          // stub the existence of valid dnslink
+          const fqdn = 'ipfs.git.sexy'
+          dnsLink.readDnslinkFromTxtRecord = sinon.stub().withArgs(fqdn).returns('/ipfs/Qmazvovg6Sic3m9igZMKoAPjkiVZsvbWWc8ZvgjjK1qMss')
+          //
+          // Context for CORS XHR problems in Firefox: https://github.com/ipfs-shipyard/ipfs-companion/issues/436
+          runtime.isFirefox = true
+          const xhrRequest = {url: 'http://ipfs.git.sexy/index.html?argTest#hashTest', type: 'xmlhttprequest', originUrl: 'https://www.nasa.gov/foo.html', requestId: fakeRequestId()}
+          // onBeforeRequest should not change anything, as it will trigger false-positive CORS error
+          expect(modifyRequest.onBeforeRequest(xhrRequest)).to.equal(undefined)
+          // onHeadersReceived is after CORS validation happens, so its ok to cancel and redirect late
+          expect(modifyRequest.onHeadersReceived(xhrRequest).redirectUrl).to.equal(activeGateway + '/ipns/ipfs.git.sexy/index.html?argTest#hashTest')
+        })
+        it('should be left unouched if dnslink does not exist and XHR is cross-origin in Firefox', function () {
+          // stub no dnslink
+          const fqdn = 'youtube.com'
+          dnsLink.readDnslinkFromTxtRecord = sinon.stub().withArgs(fqdn).returns(undefined)
+          // Context for CORS XHR problems in Firefox: https://github.com/ipfs-shipyard/ipfs-companion/issues/436
+          runtime.isFirefox = true
+          const xhrRequest = {url: 'https://youtube.com/index.html?argTest#hashTest', type: 'xmlhttprequest', originUrl: 'https://www.nasa.gov/foo.html', requestId: fakeRequestId()}
+          // onBeforeRequest should not change anything
+          expect(modifyRequest.onBeforeRequest(xhrRequest)).to.equal(undefined)
+          // onHeadersReceived should not change anything
+          expect(modifyRequest.onHeadersReceived(xhrRequest)).to.equal(undefined)
+        })
+      })
     })
   })