Add redirect support (limit: 6)

Resolves issue #25.

README.md

@@ -39,6 +39,9 @@ datDns.resolveName('foo.com', {noDnsOverHttps: true})
 // dont use .well-known/dat
 datDns.resolveName('foo.com', {noWellknownDat: true})
 
+// specify amount of redirects (default: 7)
+datDns.resolveName('foo.com', { followRedirects: 2 })
+
 // list all entries in the cache
 datDns.listCache()
 

index.js

@@ -15,6 +15,7 @@ const VERSION_REGEX = /(\+[^\/]+)$/
 const DEFAULT_DAT_DNS_TTL = 3600 // 1hr
 const MAX_DAT_DNS_TTL = 3600 * 24 * 7 // 1 week
 const DEFAULT_DNS_PROVIDERS = [['cloudflare-dns.com', 443, '/dns-query'], ['dns.google', 443, '/resolve']]
+const DEFAULT_FOLLOW_REDIRECTS = 6
 
 module.exports = createDatDNS
 
@@ -69,6 +70,7 @@ function createDatDNS (datDnsOpts) {
     var ignoreCachedMiss = opts && opts.ignoreCachedMiss
     var noDnsOverHttps = opts && opts.noDnsOverHttps
     var noWellknownDat = opts && opts.noWellknownDat
+    var followRedirects = (opts && opts.followRedirects) || DEFAULT_FOLLOW_REDIRECTS
     return maybe(cb, _asyncToGenerator(function * () {
       // parse the name as needed
       var nameParsed = url.parse(name)
@@ -117,7 +119,10 @@ function createDatDNS (datDnsOpts) {
 
         if (!res && !noWellknownDat) {
           // do a .well-known/`${recordName}` lookup
-          res = yield fetchWellKnownRecord(name, recordName)
+          const wellknownPath = !recordName.startsWith('/')
+            ? '/.well-known/' + recordName
+            : recordName
+          res = yield fetchWellKnownRecordWithRedirects(recordName, name, wellknownPath, followRedirects)
           if (res.statusCode === 0 || res.statusCode === 404) {
             debug('.well-known/' + recordName + ' lookup failed for name:', name, res.statusCode, res.err)
             datDns.emit('failed', {
@@ -280,16 +285,39 @@ function parseDnsOverHttpsRecord (datDns, name, body, dnsTxtRegex) {
   return res
 }
 
-function fetchWellKnownRecord (name, recordName) {
-  return new Promise((resolve, reject) => {
-    debug('.well-known/dat lookup for name:', name)
-    https.get({
-      host: name,
-      path: '/.well-known/' + recordName,
-      timeout: 2000
-    }, function (res) {
+function fetchWellKnownRecordWithRedirects (recordName, host, path, followRedirects) {
+  return _asyncToGenerator(function * () {
+    let redirectCount = 0
+    while (redirectCount < followRedirects) {
+      const res = yield fetchWellKnownRecord(recordName, host, path)
+      if ([301, 302, 307, 308].includes(res.statusCode)) {
+        if (!'location' in res.headers) {
+          debug('.well-known/' + recordName + ' lookup redirect did not contain destination Location header.')
+          throw new Error('Well record redirected to nowhere')
+        }
+        // resolve relative paths with original URL as base URL
+        const uri = new URL(res.headers['location'], 'https://' + host)
+        if (uri.protocol !== 'https:') {
+          throw new Error('DNS record redirected to non https: protocol: ' + uri.href)
+        }
+        host = uri.host
+        path = uri.pathname + uri.search
+        redirectCount++
+        debug('.well-known/' + recordName + ' lookup redirected to https://' + host + path, '(' + res.statusCode + ') [' + redirectCount + '/' + followRedirects + ']')
+      } else {
+        return res
+      }
+    }
+    throw new Error('Well known record lookup exceeded redirection limit: ' + followRedirects)
+  })()
+}
+
+function fetchWellKnownRecord (recordName, host, path) {
+  return new Promise(resolve => {
+    debug('.well-known/' + recordName + ' lookup at https://' + host + path)
+    https.get({ host, path, timeout: 2000 }, function (res) {
       res.setEncoding('utf-8')
-      res.pipe(concat(body => resolve({ statusCode: res.statusCode, body })))
+      res.pipe(concat(body => resolve({ statusCode: res.statusCode, body, headers: res.headers })))
     }).on('error', function (err) {
       resolve({ statusCode: 0, err, body: '' })
     })

test.js

@@ -8,8 +8,6 @@ var cabalDns = createDatDNS({
     txtRegex: /^"?cabalkey=([0-9a-f]{64})"?$/i
 })
 
-var FAKE_DAT = 'f'.repeat(64)
-
 tape('Successful test against cblgh.org', function (t) {
   cabalDns.resolveName('cblgh.org', function (err, name) {
     t.error(err)
@@ -197,6 +195,40 @@ tape('Successful test against dns-test-setup.dat-ecosystem.org (no well-known/da
   })
 })
 
+tape('Successful test against dns-test-setup-2.dat-ecosystem.org (well-known, multiple, , redirects)', function (t) {
+  const datDnsHop3 = require('./index')({ recordName: 'dat-hop-3' })
+  datDnsHop3.resolveName('dns-test-setup-2.dat-ecosystem.org', {noDnsOverHttps: true, ignoreCache: true })
+    .then(name => {
+      t.equals(name, '222231b5589a5099aa3610a8ee550dcd454c3e33f4cac93b7d41b6b850cde222')
+      return datDnsHop3.resolveName('dns-test-setup-2.dat-ecosystem.org')
+        .then(name2 => {
+          t.equal(name, name2)
+          t.end()
+        })
+    })
+    .catch(err => {
+      t.error(err)
+      t.end()
+    })
+})
+
+tape('Fail test against dns-test-setup-2.dat-ecosystem.org (well-known, multiple, exceeding redirects)', function (t) {
+  const datDnsHop3 = require('./index')({ recordName: 'dat-hop-3' })
+  datDnsHop3.resolveName('dns-test-setup-2.dat-ecosystem.org', {noDnsOverHttps: true, ignoreCache: true, followRedirects: 2})
+    .then(name => {
+      t.equals(name, '222231b5589a5099aa3610a8ee550dcd454c3e33f4cac93b7d41b6b850cde222')
+      return datDnsHop3.resolveName('dns-test-setup-2.dat-ecosystem.org')
+        .then(() => {
+          t.fail('Dont expect to succeed')
+          t.end()
+        })
+    })
+    .catch(err => {
+      t.equals(err.message, 'Well known record lookup exceeded redirection limit: 2')
+      t.end()
+    })
+})
+
 tape('List cache', function (t) {
   t.is(Object.keys(datDns.listCache()).length, 6)
   t.end()