WEB安全：XSS漏洞与SQL注入漏洞介绍及解决方案 - 牛奶、不加糖

一、跨站脚本攻击(XSS)

XSS案例分析

如何防御?

import java.net.URLEncoder;

/**
* 过滤非法字符工具类
*
*/
public class EncodeFilter {

//过滤大部分html字符
public static String encode(String input) {
if (input == null) {
return input;
}
StringBuilder sb = new StringBuilder(input.length());
for (int i = 0, c = input.length(); i < c; i++) {
char ch = input.charAt(i);
switch (ch) {
case '&': sb.append("&amp;");
break;
case '<': sb.append("&lt;");
break;
case '>': sb.append("&gt;");
break;
case '"': sb.append("&quot;");
break;
case '\'': sb.append("&#x27;");
break;
case '/': sb.append("&#x2F;");
break;
default: sb.append(ch);
}
}
return sb.toString();
}

//js端过滤
public static String encodeForJS(String input) {
if (input == null) {
return input;
}

StringBuilder sb = new StringBuilder(input.length());

for (int i = 0, c = input.length(); i < c; i++) {
char ch = input.charAt(i);

// do not encode alphanumeric characters and ',' '.' '_'
if (ch >= 'a' && ch <= 'z' || ch >= 'A' && ch <= 'Z' ||
ch >= '0' && ch <= '9' ||
ch == ',' || ch == '.' || ch == '_') {
sb.append(ch);
} else {
String temp = Integer.toHexString(ch);

// encode up to 256 with \\xHH
if (ch < 256) {
sb.append('\\').append('x');
if (temp.length() == 1) {
sb.append('0');
}
sb.append(temp.toLowerCase());

// otherwise encode with \\uHHHH
} else {
sb.append('\\').append('u');
for (int j = 0, d = 4 - temp.length(); j < d; j ++) {
sb.append('0');
}
sb.append(temp.toUpperCase());
}
}
}

return sb.toString();
}

/**
* css非法字符过滤
* http://www.w3.org/TR/CSS21/syndata.html#escaped-characters
*/
public static String encodeForCSS(String input) {
if (input == null) {
return input;
}

StringBuilder sb = new StringBuilder(input.length());

for (int i = 0, c = input.length(); i < c; i++) {
char ch = input.charAt(i);

// check for alphanumeric characters
if (ch >= 'a' && ch <= 'z' || ch >= 'A' && ch <= 'Z' ||
ch >= '0' && ch <= '9') {
sb.append(ch);
} else {
// return the hex and end in whitespace to terminate
sb.append('\\').append(Integer.toHexString(ch)).append(' ');
}
}
return sb.toString();
}

/**
* URL参数编码
* http://en.wikipedia.org/wiki/Percent-encoding
*/
public static String encodeURIComponent(String input) {
return encodeURIComponent(input, "utf-8");
}

public static String encodeURIComponent(String input, String encoding) {
if (input == null) {
return input;
}
String result;
try {
result = URLEncoder.encode(input, encoding);
} catch (Exception e) {
result = "";
}
return result;
}

public static boolean isValidURL(String input) {
if (input == null || input.length() < 8) {
return false;
}
char ch0 = input.charAt(0);
if (ch0 == 'h') {
if (input.charAt(1) == 't' &&
input.charAt(2) == 't' &&
input.charAt(3) == 'p') {
char ch4 = input.charAt(4);
if (ch4 == ':') {
if (input.charAt(5) == '/' &&
input.charAt(6) == '/') {

return isValidURLChar(input, 7);
} else {
return false;
}
} else if (ch4 == 's') {
if (input.charAt(5) == ':' &&
input.charAt(6) == '/' &&
input.charAt(7) == '/') {

return isValidURLChar(input, 8);
} else {
return false;
}
} else {
return false;
}
} else {
return false;
}

} else if (ch0 == 'f') {
if( input.charAt(1) == 't' &&
input.charAt(2) == 'p' &&
input.charAt(3) == ':' &&
input.charAt(4) == '/' &&
input.charAt(5) == '/') {

return isValidURLChar(input, 6);
} else {
return false;
}
}
return false;
}

static boolean isValidURLChar(String url, int start) {
for (int i = start, c = url.length(); i < c; i ++) {
char ch = url.charAt(i);
if (ch == '"' || ch == '\'') {
return false;
}
}
return true;
}

}

SQL注入漏洞

防御方法

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class SqlBuilder {
protected StringBuilder sqlBuf = new StringBuilder();
protected List<Object> values = new ArrayList<Object>();
protected Map<String, Object> paramMap = new HashMap<String, Object>();

public SqlBuilder appendSql(String sql) {
sqlBuf.append(sql);
return this;
}

public SqlBuilder appendValue(Object value) {
sqlBuf.append('?');
values.add(value);
return this;
}

public SqlBuilder appendValues(Object[] values) {
sqlBuf.append('(');
for (int i = 0, c = values.length; i < c; ++i) {
sqlBuf.append('?').append(',');
this.values.add(values[i]);
}
int last = sqlBuf.length() - 1;
if (last > 0 && sqlBuf.charAt(last) == ',') {
sqlBuf.setCharAt(last, ')');
}
return this;
}

public SqlBuilder appendEqParam(String param, Object value) {
sqlBuf.append(param).append(" = :").append(param);
paramMap.put(param, value);
return this;
}

public SqlBuilder appendLtParam(String param, Object value) {
sqlBuf.append(param).append(" < :").append(param);
paramMap.put(param, value);
return this;
}

public SqlBuilder appendGtParam(String param, Object value) {
sqlBuf.append(param).append(" > :").append(param);
paramMap.put(param, value);
return this;
}

public SqlBuilder appendInParam(String param, Object ... values) {
if(values == null) {
return this;
}
sqlBuf.append(param).append(" in (");
int len = values.length;
for(int i = 0; i < len; i++) {
if(i != 0) {
sqlBuf.append(", ");
}
sqlBuf.append(":").append(param).append(i);
paramMap.put(param+i, values[i]);
}
sqlBuf.append(")");
return this;
}

public SqlBuilder appendLikeParam(String param, Object value) {
sqlBuf.append(param).append(" like :").append(param);
paramMap.put(param, "%"+value+"%");
return this;
}

public String getSql() {
return sqlBuf.toString();
}

public Object[] getValues() {
return values.toArray();
}

public Map<String, Object> getParamMap() {
return paramMap;
}
}