Denial of service in Fastify via Content-Type header

@@ -29,9 +29,10 @@ const {
 
 function ContentTypeParser (bodyLimit, onProtoPoisoning, onConstructorPoisoning) {
   this[kDefaultJsonParse] = getDefaultJsonParser(onProtoPoisoning, onConstructorPoisoning)
-  this.customParsers = {}
-  this.customParsers['application/json'] = new Parser(true, false, bodyLimit, this[kDefaultJsonParse])
-  this.customParsers['text/plain'] = new Parser(true, false, bodyLimit, defaultPlainTextParser)
+  // using a map instead of a plain object to avoid prototype hijack attacks
+  this.customParsers = new Map()
+  this.customParsers.set('application/json', new Parser(true, false, bodyLimit, this[kDefaultJsonParse]))
+  this.customParsers.set('text/plain', new Parser(true, false, bodyLimit, defaultPlainTextParser))
   this.parserList = ['application/json', 'text/plain']
   this.parserRegExpList = []
   this.cache = lru(100)
@@ -62,35 +63,35 @@ ContentTypeParser.prototype.add = function (contentType, opts, parserFn) {
   )
 
   if (contentTypeIsString && contentType === '*') {
-    this.customParsers[''] = parser
+    this.customParsers.set('', parser)
   } else {
     if (contentTypeIsString) {
       this.parserList.unshift(contentType)
     } else {
       this.parserRegExpList.unshift(contentType)
     }
-    this.customParsers[contentType] = parser
+    this.customParsers.set(contentType.toString(), parser)
   }
 }
 
 ContentTypeParser.prototype.hasParser = function (contentType) {
-  return contentType in this.customParsers
+  return this.customParsers.has(typeof contentType === 'string' ? contentType : contentType.toString())
 }
 
 ContentTypeParser.prototype.existingParser = function (contentType) {
-  if (contentType === 'application/json') {
-    return this.customParsers['application/json'] && this.customParsers['application/json'].fn !== this[kDefaultJsonParse]
+  if (contentType === 'application/json' && this.customParsers.has(contentType)) {
+    return this.customParsers.get(contentType).fn !== this[kDefaultJsonParse]
   }
-  if (contentType === 'text/plain') {
-    return this.customParsers['text/plain'] && this.customParsers['text/plain'].fn !== defaultPlainTextParser
+  if (contentType === 'text/plain' && this.customParsers.has(contentType)) {
+    return this.customParsers.get(contentType).fn !== defaultPlainTextParser
   }
 
-  return contentType in this.customParsers
+  return this.hasParser(contentType)
 }
 
 ContentTypeParser.prototype.getParser = function (contentType) {
-  if (contentType in this.customParsers) {
-    return this.customParsers[contentType]
+  if (this.hasParser(contentType)) {
+    return this.customParsers.get(contentType)
   }
 
   if (this.cache.has(contentType)) {
@@ -101,7 +102,7 @@ ContentTypeParser.prototype.getParser = function (contentType) {
   for (var i = 0; i !== this.parserList.length; ++i) {
     const parserName = this.parserList[i]
     if (contentType.indexOf(parserName) !== -1) {
-      const parser = this.customParsers[parserName]
+      const parser = this.customParsers.get(parserName)
       this.cache.set(contentType, parser)
       return parser
     }
@@ -111,17 +112,17 @@ ContentTypeParser.prototype.getParser = function (contentType) {
   for (var j = 0; j !== this.parserRegExpList.length; ++j) {
     const parserRegExp = this.parserRegExpList[j]
     if (parserRegExp.test(contentType)) {
-      const parser = this.customParsers[parserRegExp]
+      const parser = this.customParsers.get(parserRegExp.toString())
       this.cache.set(contentType, parser)
       return parser
     }
   }
 
-  return this.customParsers['']
+  return this.customParsers.get('')
 }
 
 ContentTypeParser.prototype.removeAll = function () {
-  this.customParsers = {}
+  this.customParsers = new Map()
   this.parserRegExpList = []
   this.parserList = []
   this.cache = lru(100)
@@ -130,7 +131,7 @@ ContentTypeParser.prototype.removeAll = function () {
 ContentTypeParser.prototype.remove = function (contentType) {
   if (!(typeof contentType === 'string' || contentType instanceof RegExp)) throw new FST_ERR_CTP_INVALID_TYPE()
 
-  delete this.customParsers[contentType]
+  this.customParsers.delete(contentType.toString())
 
   const parsers = typeof contentType === 'string' ? this.parserList : this.parserRegExpList
 
@@ -289,7 +290,7 @@ function Parser (asString, asBuffer, bodyLimit, fn) {
 function buildContentTypeParser (c) {
   const contentTypeParser = new ContentTypeParser()
   contentTypeParser[kDefaultJsonParse] = c[kDefaultJsonParse]
-  Object.assign(contentTypeParser.customParsers, c.customParsers)
+  contentTypeParser.customParsers = new Map(c.customParsers.entries())
   contentTypeParser.parserList = c.parserList.slice()
   return contentTypeParser
 }

@@ -196,7 +196,7 @@ test('add', t => {
     const contentTypeParser = fastify[keys.kContentTypeParser]
 
     contentTypeParser.add('*', {}, first)
-    t.equal(contentTypeParser.customParsers[''].fn, first)
+    t.equal(contentTypeParser.customParsers.get('').fn, first)
   })
 
   t.end()
@@ -306,7 +306,7 @@ test('remove', t => {
 
     contentTypeParser.remove('image/png')
 
-    t.same(Object.keys(contentTypeParser.customParsers).length, 2)
+    t.same(contentTypeParser.customParsers.size, 2)
   })
 
   t.end()
@@ -329,3 +329,69 @@ test('remove all should remove all existing parsers and reset cache', t => {
   t.same(contentTypeParser.parserRegExpList.length, 0)
   t.same(Object.keys(contentTypeParser.customParsers).length, 0)
 })
+
+test('Safeguard against malicious content-type / 1', async t => {
+  const badNames = Object.getOwnPropertyNames({}.__proto__) // eslint-disable-line
+  t.plan(badNames.length)
+
+  const fastify = Fastify()
+
+  fastify.post('/', async () => {
+    return 'ok'
+  })
+
+  for (const prop of badNames) {
+    const response = await fastify.inject({
+      method: 'POST',
+      path: '/',
+      headers: {
+        'content-type': prop
+      },
+      body: ''
+    })
+
+    t.same(response.statusCode, 415)
+  }
+})
+
+test('Safeguard against malicious content-type / 2', async t => {
+  t.plan(1)
+
+  const fastify = Fastify()
+
+  fastify.post('/', async () => {
+    return 'ok'
+  })
+
+  const response = await fastify.inject({
+    method: 'POST',
+    path: '/',
+    headers: {
+      'content-type': '\\u0063\\u006fnstructor'
+    },
+    body: ''
+  })
+
+  t.same(response.statusCode, 415)
+})
+
+test('Safeguard against malicious content-type / 3', async t => {
+  t.plan(1)
+
+  const fastify = Fastify()
+
+  fastify.post('/', async () => {
+    return 'ok'
+  })
+
+  const response = await fastify.inject({
+    method: 'POST',
+    path: '/',
+    headers: {
+      'content-type': 'constructor; charset=utf-8'
+    },
+    body: ''
+  })
+
+  t.same(response.statusCode, 415)
+})