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GHSA-j7px-6hwj-hpjg
No affected components available
Impact
As users can provide a redirect address for the proxy to send the authenticated user to at the end of the authentication flow. This is expected to be the original URL that the user was trying to access. This redirect URL is checked within the proxy and validated before redirecting the user to prevent malicious actors providing redirects to potentially harmful sites.
However, by crafting a redirect URL with HTML encoded whitespace characters (eg. %0a, %0b,%09,%0d) the validation could be bypassed and allow a redirect to any URL provided.
Patches
@rootxharsh and @iamnoooob provided this patch as potential solution:
From 4b941f56eda310b5c4dc8080b7635a6bfabccad4 Mon Sep 17 00:00:00 2001
From: Harsh Jaiswal <harsh@pop-os.localdomain>
Date: Fri, 1 May 2020 20:38:31 +0530
Subject: [PATCH] Fixes redirect issue
---
oauthproxy.go | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/oauthproxy.go b/oauthproxy.go
index 1e9bb7c..f8beb4d 100644
--- a/oauthproxy.go
+++ b/oauthproxy.go
@@ -577,8 +577,9 @@ func validOptionalPort(port string) bool {
// IsValidRedirect checks whether the redirect URL is whitelisted
func (p *OAuthProxy) IsValidRedirect(redirect string) bool {
+ matched, _ := regexp.MatchString(`^/\s+/|\\`, redirect)
switch {
- case strings.HasPrefix(redirect, "/") && !strings.HasPrefix(redirect, "//") && !strings.HasPrefix(redirect, "/\\"):
+ case strings.HasPrefix(redirect, "/") && !strings.HasPrefix(redirect, "//") && !matched:
return true
case strings.HasPrefix(redirect, "http://") || strings.HasPrefix(redirect, "https://"):
redirectURL, err := url.Parse(redirect)
--
2.17.1
This issue was also reported to us separately by @mik317 several hours later
The fix was implemented in #xxx and released as version 5.1.1
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data. There is a low impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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