-
Improvement
-
Resolution: Fixed
-
Minor
We need to present the banner used in SSH since it can show legal information and or
password is about to expire.
This is an example using OpenSSH 9.8
2024-10-24 09:49:35,080 (Logger.java:46) TRACE : Received SSH_MSG_KEXDH_REPLY/SSH_MSG_KEX_DH_GEX_GROUP 212 bytes payload 2024-10-24 09:49:35,104 (Logger.java:46) TRACE : Client: 'SSH-2.0-TrileadSSH2Java_213' 2024-10-24 09:49:35,105 (Logger.java:46) TRACE : Server: 'SSH-2.0-OpenSSH_9.8' 2024-10-24 09:49:35,109 (Logger.java:46) TRACE : Sent SSH_MSG_NEWKEYS 1 bytes payload 2024-10-24 09:49:35,114 (Logger.java:46) TRACE : Received SSH_MSG_NEWKEYS 1 bytes payload 2024-10-24 09:49:35,115 (ImplSsh.java:571) DEBUG : Done creating a ssh connection: 214.21.133.206:830_ID6240977 2024-10-24 09:49:35,117 (Logger.java:46) TRACE : Sent SSH_MSG_SERVICE_REQUEST 17 bytes payload 2024-10-24 09:49:35,117 (Logger.java:46) TRACE : Sent SSH_MSG_USERAUTH_REQUEST 37 bytes payload 2024-10-24 09:49:35,162 (Logger.java:46) TRACE : Received SSH_MSG_SERVICE_ACCEPT 17 bytes payload 2024-10-24 09:49:35,209 (Logger.java:46) TRACE : Received SSH_MSG_USERAUTH_BANNER 1031 bytes payload 2024-10-24 09:49:35,210 (Logger.java:46) TRACE : Received SSH_MSG_USERAUTH_FAILURE 45 bytes payload 2024-10-24 09:49:35,212 (ImplSsh.java:462) DEBUG : Available authentication methods: [publickey, password, keyboard-interactive] 2024-10-24 09:49:35,212 (ImplSsh.java:464) DEBUG : Ignoring authentication methods: [publickey, password, gssapi-with-mic] 2024-10-24 09:49:35,212 (ImplSsh.java:474) DEBUG : Trying to authenticate with method: keyboard-interactive 2024-10-24 09:49:35,213 (Logger.java:46) TRACE : Sent SSH_MSG_USERAUTH_REQUEST 61 bytes payload 2024-10-24 09:49:35,220 (Logger.java:46) TRACE : Received SSH_MSG_USERAUTH_INFO_REQUEST 32 bytes payload 2024-10-24 09:49:35,223 (Logger.java:46) TRACE : Sent SSH_MSG_USERAUTH_INFO_RESPONSE 16 bytes payload 2024-10-24 09:49:35,441 (Logger.java:46) TRACE : Received SSH_MSG_USERAUTH_INFO_REQUEST 17 bytes payload 2024-10-24 09:49:35,442 (Logger.java:46) TRACE : Sent SSH_MSG_USERAUTH_INFO_RESPONSE 5 bytes payload 2024-10-24 09:49:35,448 (Logger.java:46) TRACE : Received SSH_MSG_USERAUTH_BANNER 41 bytes payload 2024-10-24 09:49:35,493 (Logger.java:46) TRACE : Received SSH_MSG_USERAUTH_SUCCESS 1 bytes payload 2024-10-24 09:49:35,494 (ImplSsh.java:488) DEBUG : keyboard-interactive authentication successful? true 2024-10-24 09:49:35,494 (ImplSsh.java:500) DEBUG : Authentication Complete: 214.21.133.206:830_ID6240977 Value of the banner: Password will expire in 75 days
Here we can see two banner messages;
1. Legal information
2. Password is about to expire.
Current implementation:
Banner data is stored in
https://github.com/mpet/trilead-ssh2/blob/master/src/com/trilead/ssh2/packets/PacketUserauthBanner.java and
AuthenticationManager holds a String for the message but it is internal to the class.
Suggestion is to add a public method, List<String> getBanners() , in Connection.
If no banner exist or banner has not been sent then we should return an empty list.
According to SSH https://www.ietf.org/rfc/rfc4252.txt
5.4. Banner Message
In some jurisdictions, sending a warning message before
authentication may be relevant for getting legal protection. Many
UNIX machines, for example, normally display text from /etc/issue,
use TCP wrappers, or similar software to display a banner before
issuing a login prompt.
The SSH server may send an SSH_MSG_USERAUTH_BANNER message at any
time after this authentication protocol starts and before
authentication is successful. This message contains text to be
displayed to the client user before authentication is attempted. The
format is as follows:
byte SSH_MSG_USERAUTH_BANNER
string message in ISO-10646 UTF-8 encoding [RFC3629]
string language tag [RFC3066]
By default, the client SHOULD display the 'message' on the screen.
However, since the 'message' is likely to be sent for every login
attempt, and since some client software will need to open a separate
window for this warning, the client software may allow the user to
explicitly disable the display of banners from the server. The
'message' may consist of multiple lines, with line breaks indicated
by CRLF pairs.
Ylonen & Lonvick Standards Track [Page 7]
RFC 4252 SSH Authentication Protocol January 2006
If the 'message' string is displayed, control character filtering,
discussed in [SSH-ARCH], SHOULD be used to avoid attacks by sending
terminal control characters.
it seems to be no restriction on number of SSH_MSG_USERAUTH_BANNER messages and this is confirmed by OpenSSH impl.
Will add a PR for this.
//mikael
