Synologic NAS suffers from an IP blocking bypass vulnerability.
8afa1408533488ccb2007ab703fe026dGreetings,
1. Seems to be possible bypass the default enabled "Auto Block of IP address" functionality in Synologic's NAS by using only one single space (\x20) to the HTTP header "X-FORWARDED-FOR"
(If already Auto Blocked, this bypass will _not_ work)
Generates in /var/log/messages: 2017-02-21T20:39:13+02:00 VirtualDSM_8451 login.cgi: login.c:1039 login.c (1039)Bad parameter :''
Bypassing whole function that will Auto Block IP if to many invalid login tries, opens the possibility to brute force without being locked out.
2. (1st Choice) "X-FORWARDED-FOR" and (2nd Choice) "CLIENT-IP" in HTTP header can be used to hide real IP from the Synology logs.
Example #1 (rhost): /var/log/auth.log: 2017-02-21T20:42:02+02:00 VirtualDSM_8451 synocgid: pam_unix(webui:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=0.0.0.0 user=admin
Example #2 (rhost): /var/log/auth.log: 2017-02-21T20:46:26+02:00 VirtualDSM_8451 synocgid: pam_unix(webui:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=Full Disclosure user=admin
Best, bashis