Fedora 27 defaults to a new Kerberos credential cache type called Kerberos Cache Manager (KCM), implemented in the sssd-kcm service, that is better suited for containerized environments and also provides a better user experience in the general case. Key features of KCM include:
Kerberos credential caches are handled by a userspace deamon with a UNIX socket entry point. That means the UIDs and GIDs of the cache owners are subject to UID namespacing, which is beneficial in containerized environments.
The UNIX socket can be mounted into containers on demand, thus allowing one or more containers to share a single Kerberos credential cache.
The KCM deamon is stateful. While no functionality that benefits from that is implemented in F-27, the deamon will allow automatic refreshes of a user’s Kerberos credentials if needed.
Information about using KCM can be found in
man sssd-kcm and also in
sssd-secrets, because KCM uses sssd-secrets for data storage. Additional
information is contained in the
SSSD Design Page for
krb5-appl-servers packages are considered to
be obsolete and have been removed from Fedora. These packages provided
Kerberos-aware telnet, ftp, rcp, rsh, and rlogin clients and servers. Users
should to move to more modern security tools, such as openssh.
OpenVPN configurations utilizing the newer
file now use a stronger cipher for the VPN tunnel by default. The default is
changed from the Blowfish algorithm using 128-bit keys to the newer AES-GCM
algorithm with 256-bit keys.
To ensure backwards compatibility, this new default also enables clients
still using the not recommended Blowfish algorithm to connect by utilizing
--ncp-ciphers feature being available in OpenVPN 2.4.
To facilitate an easy migration path away from Blowfish for clients not
supporting AES-GCM, these clients can now add or change the
option in the client configuration to either
without needing to do any other server changes.
Fedora defines system-wide crypto policies, which are followed by cryptographic libraries and tools, including OpenSSH clients. This allows administrators to use different system-wide security levels. With this update, OpenSSH Server adheres to these system-wide crypto policies, too.
This modification adds environment variables that specify enabled
algorithms. The information is passed to the
sshd daemon on the command
line. It is, therefore, necessary to restart the
sshd service for changes
to crypto-policy configuration to take effect.
The SSH-1 protocol is obsolete and no longer considered secure. As such, it is not supported by the default OpenSSH client binaries packaged for Fedora. This changes removes support for the SSH-1 protocol altogether by removing the openssh-clients-ssh1 subpackage.
The libcurl library now uses OpenSSL for TLS and crypto (instead of NSS). TLS certificates and keys stored in the NSS database need to be exported to files for libcurl to be able to load them. See http://pki.fedoraproject.org/wiki/NSS_Database for instructions on how to work with the NSS database.