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Managing Secure Shell Access in Oracle® Solaris 11.4

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Updated: June 2019

Sharing .ssh/config Files Between Multiple Oracle Solaris Releases

If your home directory is on a network, you can share the ~/.ssh/config file among multiple systems, even if those systems are running different Oracle Solaris releases or different Secure Shell implementations. However, Secure Shell implementations might not recognize all the configuration options from different Secure Shell implementations. In some cases, Secure Shell implementations might not recognize configuration options from different versions of the same Secure Shell implementation.

When the Secure Shell configuration options cannot be recognized by the different systems on the network, you can modify the ssh_config files to ignore unrecognized options, thus enabling use of the shared ~/.ssh/config file among multiple systems.

Ignore Keywords in Secure Shell

Two keywords, IgnoreUnknown and IgnoreIfUnknown, can be used to ignore Secure Shell configuration keywords that are unrecognized among multiple systems. The IgnoreUnknown keyword is available in OpenSSH and the IgnoreIfUnknown keyword is available in legacy SunSSH releases.

Both IgnoreUnknown and IgnoreIfUnknown specify a comma-separated list of ssh_config keywords, which, if unknown to the ssh program, are ignored by Secure Shell. However, the OpenSSH IgnoreUnknown keyword applies only to unknown keywords that follow it in the configuration file, while IgnoreIfUnknown applies to the entire configuration file.

The following table identifies the Secure Shell implementations in each Oracle Solaris release and the Ignore keywords that are available in each implementation.

Table 1  Ignore Keywords in Secure Shell
Secure Shell Implementation
Supported Ignore Keyword
Oracle Solaris 11.4
Oracle Solaris 11.3
IgnoreIfUnknown and IgnoreUnknown
Oracle Solaris 11.3
Oracle Solaris 11 releases prior to Oracle Solaris 11.3
Oracle Solaris 10 Update 11

    The following releases do not support the Ignore keywords and cannot be included as part of a shared Secure Shell configuration over a network.

  • Oracle Solaris 9

  • Oracle Solaris 10 prior to Update 11

  • OpenSSH 6.2 and older OpenSSH versions

Ignoring Secure Shell Keywords to Enable Interoperability

If your ~/.ssh/config file is on a network whose systems run different implementations of Secure Shell, you can enable the Secure Shell configuration keywords to work by adding the IgnoreUnknown and IgnoreIfUnknown keywords to the file.

Note -  All systems must be able to use at least one of the Ignore keywords as listed in Figure 1, Table 1, Ignore Keywords in Secure Shell.
Example 2  Sharing a Secure Shell Configuration Across Releases That Support Different Keywords

This example shows how to use the HostBasedKeyTypes keyword that was introduced in OpenSSH 6.8. The users are on a network where some systems are running a release of Secure Shell that does not support this keyword.

Add the following entries to the ssh_config file:

IgnoreUnknown HostBasedKeyTypes,IgnoreIfUnknown
IgnoreIfUnknown HostBasedKeyTypes,IgnoreUnknown

HostBasedKeyTypes ssh-rsa-cert-v01@openssh.com, ssh-rsa

You add both the Ignore keywords to enable all Secure Shell implementations to communicate. For more information, use the man to view the ssh_config (5) man page.