CVE-2020-15111

In Fiber before version 1.12.6, the filename that is given in c.Attachment() (https://docs.gofiber.io/ctx#attachment) is not escaped, and therefore vulnerable for a CRLF injection attack. I.e. an attacker could upload a custom filename and then give the link to the victim. With this filename, the attacker can change the name of the downloaded file, redirect to another site, change the authorization header, etc. A possible workaround is to serialize the input before passing it to ctx.Attachment().

In Fiber before version 1.12.6, the filename that is given in c.Attachment() (https://docs.gofiber.io/ctx#attachment) is not escaped, and therefore vulnerable for a CRLF injection attack. I.e. an attacker could upload a custom filename and then give the link to the victim. With this filename, the attacker can change the name of the downloaded file, redirect to another site, change the authorization header, etc. A possible workaround is to serialize the input before passing it to ctx.Attachment().

Due to improper input sanitization, a maliciously constructed filename could cause a file download to use an attacker controlled filename, as well as injecting additional headers into an HTTP response.

### Impact The filename that is given in [c.Attachment()](https://docs.gofiber.io/ctx#attachment) is not escaped, and therefore vulnerable for a CRLF injection attack. I.e. an attacker could upload a custom filename and then give the link to the victim. With this filename, the attacker can change the name of the downloaded file, redirect to another site, change the authorization header, etc. ### Steps to reproduce ```go package main import "github.com/gofiber/fiber" const badFileName = "another secret document.pdf\"\r\nLocation: google.com\r\nAuthorization: \"example_of_session_fixation" func splitTheResponse(c *fiber.Ctx) { c.Attachment(badFileName) } func main() { app := fiber.New() app.Get("/attack", splitTheResponse) app.Listen("127.0.0.1:8080") } ``` ``` HTTP/1.1 200 OK Date: Fri, 10 Jul 2020 19:47:04 GMT Content-Type: application/octet-stream Content-Length: 0 Content-Disposition: attachment; filename="another secret document.pdf" Location: google.com Authorization: "example_of_session_fixation" ``` ### Patches This issue has been patched in `v1.12.6` with commit [579](https://github.com/gofiber/fiber/pull/579/commits/f698b5d5066cfe594102ae252cd58a1fe57cf56f) escaping the filename by default. ### Workarounds You could of course serialize the input yourself before passing it to `ctx.Attachment()`, this is actually a good practice by default. But in case you forget, we got you covered 👍 ### References A CRLF injection attack is one of several types of injection attacks. It can be used to escalate to more malicious attacks such as Cross-site Scripting (XSS), page injection, web cache poisoning, cache-based defacement, and more. A CRLF injection vulnerability exists if an attacker can inject the CRLF characters into a web application, for example using a user input form or an HTTP request, [see acunetix](https://www.acunetix.com/websitesecurity/crlf-injection/) ### For more information If you have any questions or comments about this advisory: * Open an issue in [gofiber/fiber](https://github.com/gofiber/fiber) * Join us on [Discord](https://gofiber.io/discord)

En Fiber versiones anteriores a 1.12.6, el nombre de archivo que se proporciona en la función c.Attachment() (https://docs.gofiber.io/ctx#attachment) no es escapado y, por lo tanto, es vulnerable a un ataque de inyección CRLF. Es decir, un atacante podría cargar un nombre de archivo personalizado y luego darle el enlace a la víctima. Con este nombre de archivo, el atacante puede cambiar el nombre del archivo descargado, redireccionar a otro sitio, cambiar el encabezado de autorización, etc. Una posible solución es serializar la entrada antes de pasarla hacia la función ctx.Attachment()