css anti-modification

With the popularity of the Internet and the development of technology, website security has also received more and more attention. Among them, CSS anti-modification technology is one of the important means to protect website security. This article will introduce the relevant knowledge of CSS anti-modification technology and how to implement CSS anti-modification.

Knowledge related to CSS anti-modification technology

1. What is CSS?

CSS (Cascading Style Sheets) is the abbreviation of Cascading Style Sheets, which is a style language used to describe the appearance and style of documents such as HTML or XML. CSS can separate styles from the content of the web page, making the web page easier to maintain and modify.

2. The role of CSS

Using CSS technology can make web pages more beautiful and can also easily change the style of web pages. Compared with HTML, CSS has the following advantages:

(1) The layout is more flexible

(2) The code is more concise

(3) It is easy to modify and maintain

(4) It can greatly improve the webpage loading speed

3. The principle of CSS anti-modification

The basic principle of CSS anti-modification technology is to prevent others from modifying it through some techniques The style of the web page to ensure the security of the website. Specifically, CSS anti-modification technology can be implemented in the following ways:

(1) Using CSS Sprite: CSS Sprite is a technology that merges multiple small icons into one large icon. Using CSS Sprite technology, multiple small icons in a web page can be compressed into one large icon, making it difficult to modify any of the small icons, thus ensuring the security of the website.

(2) Use Base64 encoding: Base64 encoding is an encoding method that converts binary data into ASCII code. Base64 encoding technology can be used to convert image files in CSS files into a long string of text, thus protecting the security of image files.

(3) Prohibit right-click: Prohibiting right-click operations on web pages can prevent users from copying, pasting, saving images, etc., thereby protecting the content of the web page.

(4) Use JS encryption: Use JavaScript to encrypt the CSS code, making it difficult to modify the CSS code.

How to prevent CSS modification?

1. Use CSS Sprite

(1) Merge multiple small icons into one large icon.

(2) Use CSS styles to place large icons at appropriate locations on the web page.

(3) Set parameters such as offset and size through CSS styles, so that where small icons are needed, only the corresponding part of the large icon will be displayed.

2. Use Base64 encoding

(1) Convert the image file that needs to be protected to Base64 encoding format.

(2) Use the background-image property of CSS to insert image files into HTML.

(3) Set the size, coverage or scaling of the image through the background-size attribute.

3. Right-click prohibited

Add the following code to the web page to prohibit users from right-clicking:

<script language="JavaScript">
function stop(){
return false;
}
document.oncontextmenu=stop;
</script>

4. Use JS encryption

(1) Add the following code to the header of the web page and use JavaScript to encrypt the CSS code:

<script type="text/javascript">
function StrEnc(str, pwd){
if(str==""||pwd=="")return"";
str=escape(str);
pwd=escape(pwd);
if(pwd.length<4){pwd=pwd+"0000".substr(0,4-pwd.length);}
var prand=new Array();
for(var i=0;i<pwd.length;i++){
prand[i]=pwd.charCodeAt(i);
}
var sPos=0;
var str2="";
for(var i=0;i<str.length;i++){
sPos=(sPos==pwd.length)?0:sPos;
var tmp=parseInt(str.charCodeAt(i)^prand[sPos++]);
str2+=String.fromCharCode(tmp);
}
return str2;
}
//加密后的CSS代码
var css=document.getElementsByTagName("link");
for(var i=1;i<css.length;i++){
if(css[i].getAttribute("rel").indexOf("style")!=-1&&css[i].getAttribute("title").indexOf("notEncrypt")==-1){
var objXMLHttpRequest=new XMLHttpRequest();
objXMLHttpRequest.onreadystatechange=function(){
if (objXMLHttpRequest.readyState==4&&objXMLHttpRequest.status==200){
css[i].outerHTML="<style>"+StrEnc(objXMLHttpRequest.responseText.trim(),"key")+"</style>";
}
};
objXMLHttpRequest.open("GET",css[i].getAttribute("href"),false);
objXMLHttpRequest.send(null);
}
}
</script>

(2) Add the following code to the header of the CSS file that needs to be encrypted:

<meta charset="UTF-8">
<title>notEncrypt</title>

Summary

CSS anti-modification technology is one of the important means to protect website security. By using CSS Sprite, Base64 encoding, disabling right-clicking, and using JS encryption technology, you can effectively protect the website's style, images and other content from malicious modifications. However, when using these technologies, you also need to consider their impact on factors such as website loading speed and compatibility to achieve the best protection effect.

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