Implementation of robust data validation for HTML code
package main
import (
"github.com/gin-gonic/gin"
)
func main() {
r := gin.Default()
r.GET("/data", func(c *gin.Context) {
data := c.Query("data")
c.JSON(200, gin.H{
"message": data,
})
})
r.Run()
}
In the above code snippet, we have a simple server set up using the Gin framework in Go. This server has a single endpoint
/data
that accepts a GET request with a query parameter
data
.
The vulnerability lies in the function handling GET requests to this endpoint. The handler function directly takes the
data
query parameter from the request and sends it back in the response as a JSON object without any form of validation or sanitization. This means that if a client sends a request with HTML code as the
data
query parameter, this HTML code will be included in the JSON response.
This lack of data validation poses a serious security risk. An attacker could inject malicious HTML code as the
data
query parameter, which would then be returned in the server's response. If this response is interpreted by a website and the HTML code is rendered, it could lead to various types of attacks such as Cross-Site Scripting (XSS).
For example, an attacker could send a request like
/data?data=
. The server would then return this script in the JSON response, and if this response is used in a context where the HTML code is rendered, the malicious script could be executed.
package main
import (
"github.com/gin-gonic/gin"
"net/http"
"html"
)
func main() {
r := gin.Default()
r.GET("/data", func(c *gin.Context) {
data := c.Query("data")
// Sanitize the data input
safeData := html.EscapeString(data)
c.JSON(http.StatusOK, gin.H{
"message": safeData,
})
})
r.Run()
}
The original code was vulnerable to HTML injection because it did not sanitize the 'data' parameter received in the request. This could allow an attacker to inject malicious HTML code, which could then be interpreted and executed by the browser.
The fixed code mitigates this vulnerability by using the
html.EscapeString
function from Go's built-in
html
package to sanitize the 'data' parameter. This function replaces special HTML characters like
<
,
>
,
&
,
'
, and
"
with their respective HTML entities, effectively preventing any injected HTML code from being interpreted as actual HTML.
In addition to this, it's also recommended to implement a Content Security Policy (CSP) to further restrict the execution of any injected scripts or styles. Regularly updating and patching the dependencies used in the application can also help prevent known vulnerabilities.