🐛 [Bug]: Middleware proxy.Do overwrote the wrong scheme

[bofeng]

Bug Description

I am making a simple proxy that you can append the proxied url after /, for example, you can request http://localhost:3333/http://ip-api.com/json/1.1.1.1 , which will proxy request to http://ip-api.com/json/1.1.1.1.

Here is my code:

package main

import (
	"strings"

	"github.com/gofiber/fiber/v2"
	"github.com/gofiber/fiber/v2/middleware/proxy"
)

func main() {
	app := fiber.New()
	app.Get("/*", func(c *fiber.Ctx) error {
		path := c.OriginalURL()
		url := strings.TrimPrefix(path, "/")
		if err := proxy.Do(c, url); err != nil {
			return err
		}
		c.Response().Header.Del(fiber.HeaderServer)
		return nil
	})
	app.Listen(":3333")
}

When I request the url like: http://localhost:3333/http://ip-api.com/json/1.1.1.1 , it will show this error:

unsupported protocol "ttp". http and https are supported

By debugging and following the code, the scheme has been overwritten to "ttp" at this line: https://github.com/gofiber/fiber/blob/master/middleware/proxy/proxy.go#L131 , since at some point the addr variable has changed to "ttp://xxxxx" (without the leading "h"), the parsed scheme changed to "ttp". It seems related to the memory allocation, the problem will be gone, if in my code I either:

• change the fiber config to use Immutable: true, or
• change path := c.OriginalURL() to path := utils.CopyString(c.OriginalURL()) .

But since the code above doesn't violate fiber's rule:

As a rule of thumb, you must only use context values within the handler, and you must not keep any references.

Even if I don't use Immutable: true or utils.CopyString, the problem shouldn't be there.

Also, this bug doesn't exist when I was using version v2.10.0, which doesn't have these 3 lines: https://github.com/gofiber/fiber/blob/master/middleware/proxy/proxy.go#L130

How to Reproduce

Copy the above code and run it with fiber v2.36.0, then visit: http://localhost:3333/http://ip-api.com/json/1.1.1.1 .
You should be able to see the error:

unsupported protocol "ttp". http and https are supported

I can reproduce this in my 3 laptops: Macbook m1, Mackbook m2 and Macbook Intel.

Expected Behavior

The error shouldn't be there (the scheme shouldn't be incorrectly overwritten) even without "Immutable: true" config or CopyString

Fiber Version

v2.36.0

Code Snippet (optional)

See above

Checklist:

• I agree to follow Fiber's Code of Conduct.
• I have checked for existing issues that describe my problem prior to opening this one.
• I understand that improperly formatted bug reports may be closed without explanation.

[ReneWerner87]

thanks we will look at the problem, unfortunately everyone is pretty busy right now with version 3 and other old content