Releases

Copssh server 7.4.0

release date:

2020-10-01

Changelog

Copssh version 7.4.0 installers come with OpenSSH 8.4p(link is external) and LibreSSL 3.1.4(link is external). Cygwin and GNU tools are also upgraded.

Future deprecation notice

=========================

It is now possible to perform chosen-prefix attacks against the
SHA-1 algorithm for less than USD$50K. For this reason, we will be
disabling the "ssh-rsa" public key signature algorithm by default in a
near-future release.

This algorithm is unfortunately still used widely despite the
existence of better alternatives, being the only remaining public key
signature algorithm specified by the original SSH RFCs.

The better alternatives include:

 * The RFC8332 RSA SHA-2 signature algorithms rsa-sha2-256/512. These
   algorithms have the advantage of using the same key type as
   "ssh-rsa" but use the safe SHA-2 hash algorithms. These have been
   supported since OpenSSH 7.2 and are already used by default if the
   client and server support them.

 * The ssh-ed25519 signature algorithm. It has been supported in
   OpenSSH since release 6.5.

 * The RFC5656 ECDSA algorithms: ecdsa-sha2-nistp256/384/521. These
   have been supported by OpenSSH since release 5.7.

To check whether a server is using the weak ssh-rsa public key
algorithm, for host authentication, try to connect to it after
removing the ssh-rsa algorithm from ssh(1)'s allowed list:

    ssh -oHostKeyAlgorithms=-ssh-rsa user@host

If the host key verification fails and no other supported host key
types are available, the server software on that host should be
upgraded.

We intend to enable UpdateHostKeys by default in the next OpenSSH
release. This will assist the client by automatically migrating to
better algorithms. Users may consider enabling this option manually.

 "SHA-1 is a Shambles: First Chosen-Prefix Collision on SHA-1 and
    Application to the PGP Web of Trust" Leurent, G and Peyrin, T
    (2020) https://eprint.iacr.org/2020/014.pdf

Security
========

 * ssh-agent(1): restrict ssh-agent from signing web challenges for
   FIDO/U2F keys.

   When signing messages in ssh-agent using a FIDO key that has an
   application string that does not start with "ssh:", ensure that the
   message being signed is one of the forms expected for the SSH protocol
   (currently public key authentication and sshsig signatures).

   This prevents ssh-agent forwarding on a host that has FIDO keys
   attached granting the ability for the remote side to sign challenges
   for web authentication using those keys too.

   Note that the converse case of web browsers signing SSH challenges is
   already precluded because no web RP can have the "ssh:" prefix in the
   application string that we require.

 * ssh-keygen(1): Enable FIDO 2.1 credProtect extension when generating
   a FIDO resident key.

   The recent FIDO 2.1 Client to Authenticator Protocol introduced a
   "credProtect" feature to better protect resident keys. We use this
   option to require a PIN prior to all operations that may retrieve
   a resident key from a FIDO token.

component name	component version	component license	component source
OpenSSH	8.4p	OpenSSH license
LibreSSL	3.1.4	LibreSSL license
Cygwin	3.1.7	Cygwin license (GPL/LGPL)	Source code for Cygwin
Copssh Control Panel	4.0.1	Itefix EULA
Copssh server	7.4.0	Itefix EULA

2020

Copssh 7.3.0 (security)

release date:

2020-06-08

Changelog

Copssh version 7.3.0 installers come with OpenSSH 8.3p and LibreSSL 3.1.2. (Due to version bump-up from LibreSSL 3.0.2 at our side, you may also be interested in release notes for 3.1.1 and 3.1.0 as well).

Security
========

* scp(1): when receiving files, scp(1) could be become desynchronised
if a utimes(2) system call failed. This could allow file contents
to be interpreted as file metadata and thereby permit an adversary
to craft a file system that, when copied with scp(1) in a
configuration that caused utimes(2) to fail (e.g. under a SELinux
policy or syscall sandbox), transferred different file names and
contents to the actual file system layout.

Exploitation of this is not likely as utimes(2) does not fail under
normal circumstances. Successful exploitation is not silent - the
output of scp(1) would show transfer errors followed by the actual
file(s) that were received.

Finally, filenames returned from the peer are (since openssh-8.0)
matched against the user's requested destination, thereby
disallowing a successful exploit from writing files outside the
user's selected target glob (or directory, in the case of a
recursive transfer). This ensures that this attack can achieve no
more than a hostile peer is already able to achieve within the scp
protocol

2020

Copssh 7.2.0

release date:

2020-02-20

Changelog

Copssh version 7.2.0 installers come with OpenSSH 8.2p, LibreSSL 3.0.2 and most recent versions of Cygwin and GNU tools. We have also updated Copssh Control Panel with some minor fixes.

-- Incompatibility note for Copssh versions 6.x and earlier --

As of version 7.0, Copssh uses Cygwin 3.x libraries, introducing major and backwards-incompatible changes, thus requiring a reinstallation. You can follow our instructions here, to refresh your installation withour losing your existing setup.

Thanks to major changes in Cygwin, Copssh doesn't need a dedicated service account any longer and is run by the local system account.

The logic behind the sftp home directory isolation is now improved by introducing symbolic link folders: Each activated user gets a symbolic link folder /home/___username , pointing to the home directory provided via the User Activation wizard, resulting with a more stable and less error-prone solution. A small patch avoiding messages "bad ownership or modes for chroot directory" (non-relevant for a Copssh installation), is also introduced. NB! As always mentioned, even if the home directory isolation works as expected, you should use NTFS permissions on your file systems to achieve better security.

--- Potentially-incompatible changes in OpenSSH 8.2.0

This release includes a number of changes that may affect existing
configurations:

* ssh(1), sshd(8): the above removal of "ssh-rsa" from the accepted
CASignatureAlgorithms list.

* ssh(1), sshd(8): this release removes diffie-hellman-group14-sha1
from the default key exchange proposal for both the client and
server.

* ssh-keygen(1): the command-line options related to the generation
and screening of safe prime numbers used by the
diffie-hellman-group-exchange-* key exchange algorithms have
changed. Most options have been folded under the -O flag.

* sshd(8): the sshd listener process title visible to ps(1) has
changed to include information about the number of connections that
are currently attempting authentication and the limits configured
by MaxStartups.

* ssh-sk-helper(8): this is a new binary. It is used by the FIDO/U2F
support to provide address-space isolation for token middleware
libraries (including the internal one). It needs to be installed
in the expected path, typically under /usr/libexec or similar.

2020

Copssh 7.1.0

release date:

2019-10-12

Changelog

Copssh version 7.1.0 installers come with OpenSSH 8.1 with some security related updates:

ssh(1), sshd(8), ssh-add(1), ssh-keygen(1): an exploitable integer overflow bug was found in the private key parsing code for the XMSS key type. This key type is still experimental and support for it is not compiled by default. No user-facing autoconf option exists in portable OpenSSH to enable it. This bug was found by Adam Zabrocki and reported via SecuriTeam's SSD program.
ssh(1), sshd(8), ssh-agent(1): add protection for private keys at rest in RAM against speculation and memory side-channel attacks like Spectre, Meltdown and Rambleed. This release encrypts private keys when they are not in use with a symmetric key that is derived from a relatively large "prekey" consisting of random data (currently 16KB).

LibreSSL is also updated to 3.0.1, including a port of Billy Brumley's fix for CVE-2019-1547 in OpenSSL 1.1.1.

-- Incompatibility note for Copssh versions 6.x and earlier --

Thanks to major changes in Cygwin, Copssh doesn't need a dedicated service account any longer and is run by the local system account.

2019

Copssh 7.0.0

release date:

2019-08-27

Changelog

Copssh version 7.0.0 installers come with the latest Cygwin 3.x libraries, introducing major and backwards-incompatible changes, requiring a reinstallation. You can follow our instructions here, to refresh your installation withour losing your existing setup.

Thanks to major changes in Cygwin, Copssh doesn't need a dedicated service account any longer and is run by the local system account.

The logic behind the sftp home directory isolation is now improved by introducing symbolic link folders: Each activated user gets a symbolic link folder /home/___username , pointing to the home directory provided via the User Activation wizard, resulting with a more stable and less error-prone solution. A small patch(link is external) avoiding messages "bad ownership or modes for chroot directory" (non-relevant for a Copssh installation), is also introduced. NB! As always mentioned, even if the home directory isolation works as expected, you should use NTFS permissions on your file systems to achieve better security.

2019

Copssh server 7.4.0

Copssh server 7.4.0

release date:

Copssh 7.3.0 (security)

Copssh 7.3.0 (security)

release date:

Copssh 7.2.0

Copssh 7.2.0

release date:

Copssh 7.1.0

Copssh 7.1.0

release date:

Copssh 7.0.0

Copssh 7.0.0

release date:

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