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The patched FortiClient versions should be installed immediately as the VPN credentials could be decrypted by an attacker.
Vulnerability Overview/ Description
FortiClient stores the VPN authentication credentials in a configuration file (on Linux or Mac OSX) or in registry (on Windows). The credentials are encrypted but can still be recovered since the decryption key is hardcoded in the program and the same on all installations. Above all, the aforementioned storage is world readable, which actually lays the foundation for the credential recovery.
Proof Of Concept
1) Hardcoded key
The hardcoded key can be disclosed on the Linux version by issuing the following command:
$ strings forticlientsslvpn |grep "fc_1A"
The same decryption key can be found in the Windows and Mac OSX binary.
2) Overly permissive access control
The read access of the configuration file is set for “others” too, making the file world-readable. On Mac OSX, the file can be found under
while the same dataset is stored in the registry key
on Windows, which is world-readable for all users as well.
$ ls -l /home/user/.fctsslvpnhistory
-rw-rw-rw- 1 root root 1227 Aug 23 12:26 .fctsslvpnhistory
$ cat /home/user/.fctsslvpnhistory
Combining the two issues, an attacker can steal the password of any user who has a FortiClient profile on the system. In an enterprise environment, where employees usually log onto VPN server with their domain credentials, a vicious employee can extensively harvest the credentials of colleagues by logging onto the workstation where the credentials have been stored. Hence an attacker might steal credentials of any user in the domain and gain access to their user account (e.g. emails, other private data).
SEC Consult developed a proof of concept tool which takes as input the encrypted string, and prints the decrypted hexdecimal bytes followed by the recovered password. For now, this tool will not be released to give users more time to patch.
$ kr 420d2ee65abded897a69c50f49956909f61e3e549873cdfecf12bafdfa7b78f789a17ba1a5a6c9eb1803
0x50 0x61 0x73 0x73 0x77 0x6f 0x72 0x64
0x52 0x65 0x63 0x6f 0x76 0x65 0x72 0x65
The key generation module is based on a modified SHA-1 hash function, where the hardcoded key and IV flow in and the 24 bytes AES key comes out, what is followed by the AES-192 key expansion routine: