Jakub Jelen fc1a8bb455 CVE-2023-1667:kex: Correctly handle last fields of KEXINIT also in the client side
Previously, the last two fields of KEXINIT were considered as always zero for
the key exchange. This was true for the sending side, but might have not been
true for the received KEXINIT from the peer.

This moves the construction of these two fields closer to their reading or
writing, instead of hardcoding them on the last possible moment before they go
as input to the hashing function.

This also allows accepting the first_kex_packet_follows on the client side, even
though there is no kex algorithm now that would allow this.

It also avoid memory leaks in case the server_set_kex() or ssh_set_client_kex()
gets called multiple times, ensuring the algorithms will not change under our
hands.

It also makes use of a new flag to track if we sent KEXINIT.

Previously, this was tracked only implicitly by the content of the
session->next_crypto->{server,client}_kex (local kex). If it was not set, we
considered it was not send. But given that we need to check the local kex even
before sending it when we receive first_kex_packet_follows flag in the KEXINIT,
this can no longer be used.

Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Norbert Pocs <npocs@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
2023-05-04 11:52:18 +02:00
2017-08-21 09:12:36 +02:00
2022-05-23 10:14:18 +02:00
2014-01-07 16:08:23 +01:00
2018-11-17 20:11:51 +01:00

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 The SSH library

Why?

Why not ? :) I've began to work on my own implementation of the ssh protocol because i didn't like the currently public ones. Not any allowed you to import and use the functions as a powerful library, and so i worked on a library-based SSH implementation which was non-existing in the free and open source software world.

How/Who?

If you downloaded this file, you must know what it is : a library for accessing ssh client services through C libraries calls in a simple manner. Everybody can use this software under the terms of the LGPL - see the COPYING file

If you ask yourself how to compile libssh, please read INSTALL before anything.

Where ?

https://www.libssh.org

Contributing

Please read the file 'CONTRIBUTING.md' next to this README file. It explains our copyright policy and how you should send patches for upstream inclusion.

Have fun and happy libssh hacking!

The libssh Team

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