Re: CVE-2023-48795: Prefix Truncation Attacks in SSH Specification (Terrapin Attack)

[Alan Coopersmith <alan.coopersmith () oracle com>]

On 12/18/23 08:08, Fabian Bäumer wrote:
> ### Mitigations
>
> To mitigate this protocol vulnerability, OpenSSH suggested a so-called "strict 
> kex" which alters the SSH handshake to ensure a Man-in-the-Middle attacker 
> cannot introduce unauthenticated messages as well as convey sequence number 
> manipulation across handshakes. Support for strict key exchange has been added 
> to a variety of SSH implementations, including OpenSSH itself, PuTTY, libssh, 
> and more.
>
> **Warning: To take effect, both the client and server must support this 
> countermeasure.**

Open source projects I see have implemented this already are:

- AsyncSSH 2.14.2:
  https://asyncssh.readthedocs.io/en/latest/changes.html#release-2-14-2-18-dec-2023

- Dropbear git:
  https://github.com/mkj/dropbear/commit/6e43be5c7b99dbee49dc72b6f989f29fdd7e9356

- Erlang ssh 5.1.1:
  https://www.erlang.org/doc/apps/ssh/notes

- golang.org/x/crypto 0.17.0:
  https://groups.google.com/g/golang-announce/c/qA3XtxvMUyg

- libssh 0.10.6 and 0.9.8:
  https://www.libssh.org/2023/12/18/libssh-0-10-6-and-libssh-0-9-8-security-releases/

- libssh2 git:
  https://github.com/libssh2/libssh2/issues/1290
  https://github.com/libssh2/libssh2/pull/1291

- OpenSSH 9.6:
  https://www.openssh.com/txt/release-9.6

- Paramiko 3.4.0:
  https://www.paramiko.org/changelog.html#3.4.0

- PuTTY 0.80:
  https://lists.tartarus.org/pipermail/putty-announce/2023/000037.html

- russh 0.40.2:
  https://github.com/warp-tech/russh/releases/tag/v0.40.2

- SFTPGo 2.5.6:
  https://github.com/drakkan/sftpgo/releases/tag/v2.5.6

- ssh2 [node.js/npm] 1.15.0:
  https://github.com/mscdex/ssh2/commits/v1.15.0

- Tera Term 5.1:
  https://github.com/TeraTermProject/teraterm/releases/tag/v5.1

- Thrussh 0.35.1:
  https://pijul.org/posts/2023-12-18-thrussh-cve/

There's also some open bugs against these open source projects that are not yet handled:

- Apache Mina:
  https://github.com/apache/mina-sshd/issues/445

- ProFTPD (mod_sftp):
  https://github.com/proftpd/proftpd/issues/1760

- SSHJ:
  https://github.com/hierynomus/sshj/issues/916

--
        -Alan Coopersmith-                 alan.coopersmith () oracle com
         Oracle Solaris Engineering - https://blogs.oracle.com/solaris