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GHSA-4mf2-f3wh-gvf2
No affected components available
Impact
What kind of vulnerability is it? Who is impacted? 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.
Patches
Has the problem been patched? What versions should users upgrade to? This is fixed in version 7.0.0 onwards.
Workarounds
Is there a way for users to fix or remediate the vulnerability without upgrading? Disable the whitelist domain feature and run separate OAuth2 Proxy instances for each subdomain.
Original Issue Posted by @semoac:
Whitelist Domain feature is not working as expected because is not matching a dot to ensure the redirect is a subdomain.
Expected Behavior
If whitelist domain is set to .example.com , then hack.alienexample.com should be rejected as a valid redirect.
Current Behavior
The code is removing the dot from .example.com and only checking if the redirect string end with example.com
Possible Solution
Here https://github.com/oauth2-proxy/oauth2-proxy/blob/c377466411f2aee180a732187edb638f2f7e57fb/oauthproxy.go#L661
Include the dot when checking the string:
strings.HasSuffix(redirectHostname, "." + domainHostname)
Steps to Reproduce (for bugs)
package main
import (
"fmt"
"strings"
)
func validOptionalPort(port string) bool {
if port == "" || port == ":*" {
return true
}
if port[0] != ':' {
return false
}
for _, b := range port[1:] {
if b < '0' || b > '9' {
return false
}
}
return true
}
func splitHostPort(hostport string) (host, port string) {
host = hostport
colon := strings.LastIndexByte(host, ':')
if colon != -1 && validOptionalPort(host[colon:]) {
host, port = host[:colon], host[colon+1:]
}
if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") {
host = host[1 : len(host)-1]
}
return
}
func main() {
domain := ".example.com"
domainHostname, _ := splitHostPort(strings.TrimLeft(domain, "."))
redirectHostname := "https://hack.alienexample.com"
if (strings.HasPrefix(domain, ".") && strings.HasSuffix(redirectHostname, domainHostname)) { fmt.Println("This should not have happen.")}
}
Users of github.com/oauth2-proxy/oauth2-proxy are advised to update to github.com/oauth2-proxy/oauth2-proxy/v7
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 impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.
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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