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Tomcat

版本下载： http://archive.apache.org/dist/tomcat/

官方漏洞声明： https://tomcat.apache.org/security-7.html

历史漏洞

漏洞编号 漏洞类型 影响版本
CVE-2017-12615 写文件 7.0.0 to 7.0.79
CVE-2020-1938 文件读取/文件包含 < 9.0.31, 8.5.51 or 7.0.100
CVE-2019-0232 RCE 9.0.0.M1 to 9.0.17, 8.5.0 to 8.5.39 and 7.0.0 to 7.0.93
无 后台弱密码+GetShell 7+

windows远程调试

设置IDEA Remote JVM Debug: -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5555

修改Tomcat目录/bin/catalina.bat，找到set JAVA_OPTS=代码行，设置如下

set JAVA_OPTS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5555"

Windows下命令行运行catalina.bat start，即可开启调试

CVE-2017-12615

漏洞描述，发现和readonly配置有关，并且可以通过PUT方法上传jsp文件

When running Apache Tomcat 7.0.0 to 7.0.79 on Windows with HTTP PUTs enabled (e.g. via setting the readonly initialisation parameter of the Default to false) it was possible to upload a JSP file to the server via a specially crafted request

更改/conf/web.xml文件中的配置，原配置如下

<!--   readonly   Is this context "read only", so HTTP      -->
<!--              commands like PUT and DELETE are      -->
<!--              rejected?  [true]      -->
<servlet>
    <servlet-name>default</servlet-name>
    <servlet-class>org.apache.catalina.servlets.DefaultServlet</servlet-class>
    <init-param>
        <param-name>debug</param-name>
        <param-value>0</param-value>
    </init-param>
    <init-param>
        <param-name>listings</param-name>
        <param-value>false</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

增加一行readonly属性，并赋值为false

    <init-param>
        <param-name>readonly</param-name>
        <param-value>false</param-value>
    </init-param>

一些payload

PUT /test.jsp::$DATA
PUT /test2.jsp%20
PUT /test1.jsp/

对于第一个payload，可以参考Windows NTFS流： https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-fscc/c54dec26-1551-4d3a-a0ea-4fa40f848eb3?redirectedfrom=MSDN

对于第二个payload，Windows不允许空字符作为文件名结尾，所以会去掉空字符

对于第三个payload，是java.io.File的特性，在new File时，会去掉末尾的/

根据/conf/web.xml中的配置，jsp文件的解析是由JspServlet来执行的，而其他的默认由DefaultServlet来解析。DefaultServlet的doPut方法是漏洞触发的入口。上述在jsp后缀后面加特殊字符都是为了绕过JSPServlet，让DefaultServlet来解析

    <servlet>
        <servlet-name>jsp</servlet-name>
        <servlet-class>org.apache.jasper.servlet.JspServlet</servlet-class>
    </servlet>
    
    <servlet>
        <servlet-name>default</servlet-name>
        <servlet-class>org.apache.catalina.servlets.DefaultServlet</servlet-class>
    </servlet>
    
    <!-- The mapping for the default servlet -->
    <servlet-mapping>
        <servlet-name>default</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

    <!-- The mappings for the JSP servlet -->
    <servlet-mapping>
        <servlet-name>jsp</servlet-name>
        <url-pattern>*.jsp</url-pattern>
        <url-pattern>*.jspx</url-pattern>
    </servlet-mapping>

DefaultServlet的doPut方法

protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    if (this.readOnly) { // readOnly为true，就403禁止
        resp.sendError(403);
    } else {
        String path = this.getRelativePath(req);
        boolean exists = true;

        try {
            this.resources.lookup(path); // 从资源中查找路径下的文件是否存在
        } catch (NamingException var11) {
            exists = false;
        }

        boolean result = true;
        File contentFile = null;
        DefaultServlet.Range range = this.parseContentRange(req, resp); // 判断请求头是否包含"Content-Range"
        InputStream resourceInputStream = null;
        if (range != null) {
            contentFile = this.executePartialPut(req, range, path);
            resourceInputStream = new FileInputStream(contentFile);
        } else {
            resourceInputStream = req.getInputStream();
        }

        try {
            Resource newResource = new Resource((InputStream)resourceInputStream);
            if (exists) {
                this.resources.rebind(path, newResource);
            } else {
                this.resources.bind(path, newResource); // 
            }
        } catch (NamingException var10) {
            result = false;
        }

        if (result) {
            if (exists) {
                resp.setStatus(204);
            } else {
                resp.setStatus(201);
            }
        } else {
            resp.sendError(409);
        }

    }
}

当资源不存在时，会调用FileDirContext类

public void bind(String name, Object obj, Attributes attrs) throws NamingException {
    File file = new File(this.base, name);
    if (file.exists()) {
        throw new NameAlreadyBoundException(sm.getString("resources.alreadyBound", new Object[]{name}));
    } else {
        this.rebind(name, obj, attrs); // 如果该文件不存在，调用rebind
    }
}

rebind方法是明显的写文件函数

public void rebind(String name, Object obj, Attributes attrs) throws NamingException {
    File file = new File(this.base, name); // new File的时候会调用java.io.WinNTFileSystem .resolve() 会去掉末尾的/
    InputStream is = null;
    if (obj instanceof Resource) {
        is = ((Resource)obj).streamContent();
    } ...
    else {
        FileOutputStream os = null;
        byte[] buffer = new byte[2048];
        boolean var8 = true;

        try {
            os = new FileOutputStream(file);

            while(true) {
                int len = is.read(buffer);
                if (len == -1) {
                    return;
                }

                os.write(buffer, 0, len);
            }
        } ...
    }
}

CVE-2020-1938

Tomcat对于协议的解析包括：HTTP/1.1、AJP、HTTP/2。这个漏洞的是Tomcat AJP协议中的缺陷，攻击者可以读取或包含Tomcat的webapp目录中的任何文件

漏洞利用脚本： https://github.com/YDHCUI/CNVD-2020-10487-Tomcat-Ajp-lfi/blob/master/CNVD-2020-10487-Tomcat-Ajp-lfi.py

漏洞调试时需要添加如下pom.xml

<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat-coyote</artifactId>
    <version>7.0.79</version>
</dependency>

这个漏洞的触发点也是DefaultServlet，CVE-2017-12615执行的doPut而这个漏洞则执行的doGet

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
    this.serveResource(request, response, true);
}

serveResource的具体实现如下

protected void serveResource(HttpServletRequest request, HttpServletResponse response, boolean content) throws IOException, ServletException {
    boolean serveContent = content;
    String path = this.getRelativePath(request, true); // 获取文件路径

    if (path.length() == 0) { this.doDirectoryRedirect(request, response);} 
    else {
        CacheEntry cacheEntry = this.resources.lookupCache(path); // path和resource根目录拼接，得到资源实体
        boolean isError = DispatcherType.ERROR == request.getDispatcherType();
        String contentType;
        if (!cacheEntry.exists) {...
        } else if (cacheEntry.context == null && (path.endsWith("/") || path.endsWith("\\"))) { ...
        } else {
            contentType = cacheEntry.attributes.getMimeType();
            ...
            ServletOutputStream ostream = null;
            PrintWriter writer = null;
            if (serveContent) {
                try {
                    ostream = response.getOutputStream(); // 获取输出流
                } ...
            }
            ServletResponse r = response;
            long contentWritten;
            for(contentWritten = 0L; r instanceof ServletResponseWrapper; r = ((ServletResponseWrapper)r).getResponse()) {}
            if (r instanceof ResponseFacade) {
                contentWritten = ((ResponseFacade)r).getContentWritten();
            }

            if (cacheEntry.context == null && !isError && (ranges != null && !ranges.isEmpty() || request.getHeader("Range") != null) && ranges != FULL) { ...} 
            else {
                if (contentType != null) {
                    response.setContentType(contentType);
                }

                if (cacheEntry.resource != null && contentLength >= 0L && (!serveContent || ostream != null)) {
                    if (contentWritten == 0L) {
                        if (contentLength < 2147483647L) {
                            response.setContentLength((int)contentLength);
                        }...
                    }
                }

                InputStream renderResult = null;
                if (serveContent) {
                    ...
                    if (ostream != null) {
                        if (!this.checkSendfile(request, response, cacheEntry, contentLength, (DefaultServlet.Range)null)) {
                            this.copy(cacheEntry, renderResult, ostream); // 将文件实体的内容写入到输出流
                        }
                    } else {
                        this.copy(cacheEntry, renderResult, writer);
                    }
     ...
}

getRelativePath会得到路径servletPath+pathInfo。如果request.getAttribute("javax.servlet.include.request_uri") 值不为空，路径的值都是从属性javax.servlet.include.path_info和javax.servlet.include.servlet_path中获取的。

getRelativePath 

protected String getRelativePath(HttpServletRequest request, boolean allowEmptyPath) {
    String servletPath;
    String pathInfo;
    if (request.getAttribute("javax.servlet.include.request_uri") != null) {
        pathInfo = (String)request.getAttribute("javax.servlet.include.path_info");
        servletPath = (String)request.getAttribute("javax.servlet.include.servlet_path");
    } else {
        pathInfo = request.getPathInfo();
        servletPath = request.getServletPath();
    }
    StringBuilder result = new StringBuilder();
    if (servletPath.length() > 0) {
        result.append(servletPath);
    }
    if (pathInfo != null) {
        result.append(pathInfo);
    }
    if (result.length() == 0 && !allowEmptyPath) {
        result.append('/');
    }
    return result.toString();
}

弱密码

查看用户权限配置文件conf/tomcat-users.xml，示例如下，可以根据官网进行配置： https://tomcat.apache.org/tomcat-8.5-doc/manager-howto.html

<?xml version="1.0" encoding="UTF-8"?>
<tomcat-users xmlns="http://tomcat.apache.org/xml"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:schemaLocation="http://tomcat.apache.org/xml tomcat-users.xsd"
              version="1.0">

    <role rolename="manager-gui"/>
    <role rolename="manager-script"/>
    <role rolename="manager-jmx"/>
    <role rolename="manager-status"/>
    <role rolename="admin-gui"/>
    <role rolename="admin-script"/>
    <user username="tomcat" password="tomcat" roles="manager-gui,manager-script,manager-jmx,manager-status,admin-gui,admin-script" />

</tomcat-users>

访问http://ip:8080/manager/html输入弱密码，进入后台，上传war包