CVE 2024 34273 (#107)

* tests

* fixes tests

* version bump

* CVE-2024-34273

CHANGELOG.md

@@ -1,5 +1,9 @@
 # nJwt Change Log
 
+### 2.0.1
+
+* [#107](https://github.com/jwtk/njwt/pull/107) Freeze `prototype` of all classes to prevent prototype pollution vuln ([CVE-2024-34273](https://cve.mitre.org/cgi-bin/cvename.cgi?name=2024-34273))
+
 ### 2.0.0
 
 * [#98](https://github.com/jwtk/njwt/pull/98) Bumps jsonwebtoken version, drop Node < 12 from engines

index.d.ts

@@ -61,12 +61,11 @@ export declare class JwtBody {
   toJSON(): JSONMap;
   compact(): string;
 }
-export declare function JwtHeader(header: JwtHeaderOptions): JwtHeader;
+export declare function JwtHeader(header: JwtHeaderOptions, enforceDefaultFields?: boolean): JwtHeader;
 export declare class JwtHeader {
-  constructor(header: JwtHeaderOptions);
+  constructor(header: JwtHeaderOptions, enforceDefaultFields?: boolean);
     typ: string;
     alg: string;
-    reservedKeys: string[];
     compact(): string;
 }
 

index.js

@@ -113,17 +113,21 @@ JwtBody.prototype.compact = function compact(){
   return base64urlEncode(JSON.stringify(this));
 };
 
-function JwtHeader(header){
+var reservedHeaderKeys = ['typ','alg'];
+function JwtHeader(header, enforceDefaultFields){
   if(!(this instanceof JwtHeader)){
     return new JwtHeader(header);
   }
-  var self = this;
-  this.typ = header && header.typ || 'JWT';
-  this.alg = header && header.alg || 'HS256';
+  this.typ = header && header.typ;
+  this.alg = header && header.alg;
+  if (enforceDefaultFields !== false) {
+    this.typ = this.typ || 'JWT';
+    this.alg = this.alg || 'HS256';
+  }
 
   if(header){
     return Object.keys(header).reduce(function(acc,key){
-      if(self.reservedKeys.indexOf(key)===-1 && header.hasOwnProperty(key)){
+      if(reservedHeaderKeys.indexOf(key)===-1 && header.hasOwnProperty(key)){
         acc[key] = header[key];
       }
       return acc;
@@ -132,7 +136,6 @@ function JwtHeader(header){
     return this;
   }
 }
-JwtHeader.prototype.reservedKeys = ['typ','alg'];
 JwtHeader.prototype.compact = function compact(){
   return base64urlEncode(JSON.stringify(this));
 };
@@ -312,7 +315,7 @@ Parser.prototype.parse = function parse(jwtString,cb){
   jwt.setSigningAlgorithm(header.alg);
   jwt.signature = signature;
   jwt.verificationInput = segments[0] +'.' + segments[1];
-  jwt.header = new JwtHeader(header);
+  jwt.header = new JwtHeader(header, false);
   return done(null,jwt);
 };
 
@@ -409,11 +412,12 @@ Verifier.prototype.verify = function verify(jwtString,cb){
 
     var newJwt = new Jwt(body, false);
 
-    newJwt.toString = function () {
-      return jwtString;
-    };
+    // since prototype is now frozen, .toString can no longer be overloaded
+    // newJwt.toString = function () {
+    //   return jwtString;
+    // };
 
-    newJwt.header = new JwtHeader(header);
+    newJwt.header = new JwtHeader(header, false);
 
     if (!verified) {
       return done(new JwtParseError(properties.errors.SIGNATURE_MISMTACH,jwtString,header,body));
@@ -428,6 +432,22 @@ Verifier.prototype.withKeyResolver = function withKeyResolver(keyResolver) {
   return this;
 };
 
+// vuln: https://security.snyk.io/vuln/SNYK-JS-NJWT-6861582
+Object.freeze(Jwt);
+Object.freeze(Jwt.prototype);
+Object.freeze(JwtBody);
+Object.freeze(JwtBody.prototype);
+Object.freeze(JwtHeader);
+Object.freeze(JwtHeader.prototype);
+Object.freeze(Verifier);
+Object.freeze(Verifier.prototype);
+Object.freeze(Parser);
+Object.freeze(Parser.prototype);
+Object.freeze(JwtParseError);
+Object.freeze(JwtParseError.prototype);
+Object.freeze(JwtError);
+Object.freeze(JwtError.prototype);
+
 var jwtLib = {
   Jwt: Jwt,
   JwtBody: JwtBody,

package.json

@@ -1,6 +1,6 @@
 {
   "name": "njwt",
-  "version": "2.0.0",
+  "version": "2.0.1",
   "description": "JWT Library for Node.js",
   "engines": {
     "node": ">=12.0"

test/exports.js

@@ -0,0 +1,39 @@
+var assert = require('chai').assert;
+var nJwt = require('..');
+
+describe('njwt module exports',function () {
+  // https://github.com/chrisandoryan/vuln-advisory/blob/main/nJwt/CVE-2024-34273.md
+  describe('CVE-2024-34273', function () {
+    it('should export classes with frozen prototypes', function(){
+      assert.frozen(nJwt.Jwt);
+      assert.frozen(nJwt.Jwt.prototype);
+      assert.frozen(nJwt.JwtBody);
+      assert.frozen(nJwt.JwtBody.prototype);
+      assert.frozen(nJwt.JwtHeader);
+      assert.frozen(nJwt.JwtHeader.prototype);
+      assert.frozen(nJwt.Verifier);
+      assert.frozen(nJwt.Verifier.prototype);
+    });
+
+    it('should not allow prototype pollution', function () {
+
+      // based on: https://github.com/chrisandoryan/vuln-advisory/blob/main/nJwt/CVE-2024-34273.md#proof-of-concept-poc
+      var token = `ewogICJ0eXAiOiAiSldUIiwKICAiYWxnIjogIm5vbmUiLAogICJfX3Byb3RvX18iOiB7CiAgICAidHlwIjogIkpXVCIsCiAgICAiYWxnIjogIkhTMjU
+      2IiwKICAgICJfX3Byb3RvX18iOiB7CiAgICAgICJjb21wYWN0IjogbnVsbCwKICAgICAgInJlc2VydmVkS2V5cyI6IFsKICAgICAgICAidHlwIiwKICAgICAgICAicmF
+      uZG9tX2dpYmJlcmlzaCIKICAgICAgXQogICAgfQogIH0KfQ.ewogICJzdWIiOiAxLAogICJzY29wZSI6ICJ1c2VyIiwKICAianRpIjogImJhZmIxNmNlLTIwZDYtNGNk
+      Ny05NDgzLTY1YTA5NThhOGU2NCIsCiAgImlhdCI6IDI1Mzc0Nzg1MDYsCiAgImV4cCI6IDI1Mzc0Nzg1MDYsCiAgIl9fcHJvdG9fXyI6IHsKICAgICJjb21wYWN0Ijog
+      bnVsbCwKICAgICJ0b0pTT04iOiBudWxsLAogICAgInBvbGx1dGVkIjogdHJ1ZQogIH0KfQ`.replace(/\s/g, '');
+
+      assert.isOk(nJwt.JwtBody.prototype.hasOwnProperty('toJSON'))
+      assert.isOk(nJwt.JwtBody.prototype.hasOwnProperty('compact'))
+      assert.isOk(nJwt.JwtHeader.prototype.hasOwnProperty('compact'))
+
+      nJwt.verify(token);
+
+      assert.isOk(nJwt.JwtBody.prototype.hasOwnProperty('toJSON'))
+      assert.isOk(nJwt.JwtBody.prototype.hasOwnProperty('compact'))
+      assert.isOk(nJwt.JwtHeader.prototype.hasOwnProperty('compact'))
+    });
+  });
+
+});

test/verifier.js

@@ -36,7 +36,7 @@ describe('Verifier().setSigningAlgorithm() ',function(){
 
 describe('.verify()',function(){
   it('should persist the original token to the toString() invocation',function(){
-    var token = 'eyJhbGciOiJub25lIn0.eyJzdWIiOiIxMjMifQ.p6bizskaJLAheVyRhQEMR-60PkH_jtLVYgMy1qTjCoc';
+    var token = 'eyJhbGciOiJub25lIn0.eyJzdWIiOiIxMjMifQ';
     assert.equal(token,nJwt.verify(token).toString());
   });