JavaWeb实现XSS过滤器

自定一个请求处理类继承HttpServletRequestWrapper类，重写各个请求参数的获取方法，在方法里面使用正则匹配过滤掉特殊的符号:

1public class XSSHttpServletRequestWrapper extends HttpServletRequestWrapper {
2    /**
3     * Constructs a request object wrapping the given request.
4     *
5     * @param request The request to wrap
6     * @throws IllegalArgumentException if the request is null
7     */
8    public XSSHttpServletRequestWrapper(HttpServletRequest request) {
9        super(request);
10    }
11
12    /**
13     * 对数组参数进行特殊字符过滤
14     */
15    @Override
16    public String[] getParameterValues(String name) {
17        String[] values = super.getParameterValues(name);
18        if (values == null) {
19            return null;
20        }
21        int count = values.length;
22        String[] encodedValues = new String[count];
23        for (int i = 0; i < count; i++) {
24            encodedValues[i] = cleanXSS(values[i]);
25        }
26        return encodedValues;
27    }
28
29    /**
30     * 对参数中特殊字符进行过滤
31     */
32    @Override
33    public String getParameter(String name) {
34        String value = super.getParameter(name);
35        if (value == null) {
36            return null;
37        }
38        return cleanXSS(value);
39    }
40
41    /**
42     * 获取attribute,特殊字符过滤
43     */
44    @Override
45    public Object getAttribute(String name) {
46        Object value = super.getAttribute(name);
47        if (value != null && value instanceof String) {
48            cleanXSS((String) value);
49        }
50        return value;
51    }
52
53    /**
54     * 对请求头部进行特殊字符过滤
55     */
56    @Override
57    public String getHeader(String name) {
58        String value = super.getHeader(name);
59        if (value == null) {
60            return null;
61        }
62        return cleanXSS(value);
63    }
64
65    private String cleanXSS(String value) {
66        if (value != null) {
67            //推荐使用ESAPI库来避免脚本攻击,value = ESAPI.encoder().canonicalize(value);
68            // 避免空字符串
69            value = value.replaceAll(" ", "");
70            // 避免script 标签
71            Pattern scriptPattern = Pattern.compile("<script>(.*?)</script>", Pattern.CASE_INSENSITIVE);
72            value = scriptPattern.matcher(value).replaceAll("");
73            // 避免src形式的表达式
74            scriptPattern = Pattern.compile("src[\r\n]*=[\r\n]*\\\'(.*?)\\\'",
75                    Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
76            value = scriptPattern.matcher(value).replaceAll("");
77            scriptPattern = Pattern.compile("src[\r\n]*=[\r\n]*\\\"(.*?)\\\"",
78                    Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
79            value = scriptPattern.matcher(value).replaceAll("");
80            // 删除单个的 </script> 标签
81            scriptPattern = Pattern.compile("</script>", Pattern.CASE_INSENSITIVE);
82            value = scriptPattern.matcher(value).replaceAll("");
83            // 删除单个的<script ...> 标签
84            scriptPattern = Pattern.compile("<script(.*?)>",
85                    Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
86            value = scriptPattern.matcher(value).replaceAll("");
87            // 避免 eval(...) 形式表达式
88            scriptPattern = Pattern.compile("eval\\((.*?)\\)",
89                    Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
90            value = scriptPattern.matcher(value).replaceAll("");
91            // 避免 e­xpression(...) 表达式
92            scriptPattern = Pattern.compile("e­xpression\\((.*?)\\)",
93                    Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
94            value = scriptPattern.matcher(value).replaceAll("");
95            // 避免 javascript: 表达式
96            scriptPattern = Pattern.compile("javascript:", Pattern.CASE_INSENSITIVE);
97            value = scriptPattern.matcher(value).replaceAll("");
98            // 避免 vbscript:表达式
99            scriptPattern = Pattern.compile("vbscript:", Pattern.CASE_INSENSITIVE);
100            value = scriptPattern.matcher(value).replaceAll("");
101            // 避免 οnlοad= 表达式
102            scriptPattern = Pattern.compile("onload(.*?)=",
103                    Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
104            value = scriptPattern.matcher(value).replaceAll("");
105        }
106        return value;
107    }
108}

定义过滤器：

1public class XSSHttpServletRequestFilter implements Filter {
2    private final Logger logger = LoggerFactory.getLogger(getClass());
3
4    @Override
5    public void init(FilterConfig filterConfig) throws ServletException {
6        logger.info("##init XSSFilter");
7    }
8
9    @Override
10    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
11        try {
12            //将请求转换为 自定义的请求包装类
13            chain.doFilter(new XSSHttpServletRequestWrapper((HttpServletRequest) request), response);
14        } catch (Exception e) {
15            throw e;
16        }
17    }
18
19    @Override
20    public void destroy() {
21        logger.info("##destroy XSSFilter");
22    }
23}

将过滤器注册到spring的bean容器中:

1@Bean
2public FilterRegistrationBean xSSHttpServletRequestFilterRegistrationBean() {
3    FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
4    filterRegistrationBean.setFilter(new XSSHttpServletRequestFilter());
5    filterRegistrationBean.setName("xSSHttpServletRequestFilter");
6    filterRegistrationBean.setUrlPatterns(Arrays.asList("/xxx"));
7    filterRegistrationBean.setOrder(1);
8    return filterRegistrationBean;
9}

这里使用的springboot，如果是spring，相当于在web.xml中加入一下配置：

1<filter>
2   <filter-name>xSSHttpServletRequestFilter</filter-name>
3   <filter-class>com.xxx.xxx.xxxx.XSSHttpServletRequestFilter</filter-class>
4</filter>
5<filter-mapping>
6   <filter-name>xSSHttpServletRequestFilter</filter-name>
7   <url-pattern>/xxx</url-pattern>
8</filter-mapping>