OctoPrint has an Authentication Bypass via X-Forwarded-For Header when autologinLocal is enabled
### Impact
OctoPrint versions up until and including 1.10.0 contain a vulnerability that allows an unauthenticated attacker to completely bypass the authentication **if the `autologinLocal` option is enabled** within `config.yaml`, even if they come from networks that are not configured as `localNetworks`, by spoofing their IP via the `X-Forwarded-For` header.
If autologin is not enabled, this vulnerability does not have any impact.
### Patches
The vulnerability has been patched in version 1.10.1.
### Workaround
Until the patch has been applied, OctoPrint administrators who have autologin enabled on their instances should disable it and/or to make the instance inaccessible from potentially hostile networks like the internet.
### PoC
1. Enable the `autologinAs` configuration within the `accessControl` section in the OctoPrint yaml configuration file
https://docs.octoprint.org/en/master/configuration/config_yaml.html#access-control
2. Set your browser to add the `X-Forwarded-For: 127.0.0.1` header to HTTP requests. For example, this can be done using proxy software like Burp Suite. Alternatively, there are browser extensions such as
https://github.com/MisterPhilip/x-forwarded-for, but I haven't tried them.
3. Navigate to OctoPrint and note that it logs you in automatically.
### Credits
This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.