OAuth2-Proxy is an open source reverse proxy that provides authentication with Google, Github or other providers. The --gitlab-group flag for group-based authorization in the GitLab provider stopped working in the v7.0.0 release. Regardless of the flag settings, authorization wasn't restricted. Additionally, any authenticated users had whichever groups were set in --gitlab-group added to the new X-Forwarded-Groups header to the upstream application. While adding GitLab project based authorization support in #630, a bug was introduced where the user session's groups field was populated with the --gitlab-group config entries instead of pulling the individual user's group membership from the GitLab Userinfo endpoint. When the session groups where compared against the allowed groups for authorization, they matched improperly (since both lists were populated with the same data) so authorization was allowed. This impacts GitLab Provider users who relies on group membership for authorization restrictions. Any authenticated users in your GitLab environment can access your applications regardless of --gitlab-group membership restrictions. This is patched in v7.1.0. There is no workaround for the Group membership bug. But --gitlab-project can be set to use Project membership as the authorization checks instead of groups; it is not broken.

CSRF in Bitly oauth2proxy 2.1 during authentication flow

The Bitly oauth2proxy in version 2.1 and earlier was affected by an open redirect vulnerability during the start and termination of the 2-legged OAuth flow. This issue was caused by improper input validation and a violation of RFC-6819

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

In OAuth2 Proxy from version 5.1.1 and less than version 6.0.0, 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. This has been fixed in version 6.0.0.

OAuth2 Proxy is an open-source reverse proxy and static file server that provides authentication using Providers (Google, GitHub, and others) to validate accounts by email, domain or group. In OAuth2 Proxy before version 7.0.0, for users that use the whitelist domain feature, a domain that ended in a similar way to the intended domain could have been allowed as a redirect. For example, if a whitelist domain was configured for ".example.com", the intention is that subdomains of example.com are allowed. Instead, "example.com" and "badexample.com" could also match. This is fixed in version 7.0.0 onwards. As a workaround, one can disable the whitelist domain feature and run separate OAuth2 Proxy instances for each subdomain.