Dear All,
I noticed that OpenVas does not manage to login via SSH if the remote server has the following secure cipher suites enabled:
Ciphers aes256-ctr,aes192-ctr,aes128-ctr
KexAlgorithms diffie-hellman-group-exchange-sha256
MACs hmac-sha2-512,hmac-sha2-256,hmac-ripemd160
The SSH server / client combination I tested this on is the following:
SSH Server: OpenSSH_5.9p1 Debian-5ubuntu1.9
SSH Client: OpenSSH_6.6.1p1 (CentOS 7, also tested with most recent Kali 2.0 OpenSSH version, same negative result)
I tried public key (RSA & DSA tested) & password logins – neither works for OpenVas with the secure cipher suites posted above. Logging in manually however works perfectly fine via public key & password.
The SSH Authorization Check plugin fails among others and obviously no authenticated scans are conducted.
Disabling the three secure cipher suite lines above (and changing nothing else) allows OpenVas to login via SSH again (pubkey).
The openvassd.log file does not show any issues / errors at all.
The SSH auth.log on the scanned machine does not show any failed authentication attempts by the OpenVas scanner.
Is this a known issue?
I did not find any documentation on issues with certain cipher suites and spent a good amount of time researching this – maybe you want to add this issue somewhere so the next person researching can come to a conclusion more quickly.
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