SSH

ssh-broker-g3

ssh-broker-g3 — Tectia Connection Broker - Generation 3

Synopsis

ssh-broker-g3 [-a, --broker-address=ADDR] [-f, --config-file=FILE] [-D, --debug=LEVEL] [-l, --debug-log-file=FILE] [--pid-file=FILE] [--exit] [--reconfig] [-h] [-V]

Description

ssh-broker-g3 (ssh-broker-g3.exe on Windows) is a component of Tectia Client and Tectia ConnectSecure. It handles all cryptographic operations and authentication-related tasks for Tectia Client and for the client programs sshg3, scpg3, sftpg3, and ssh-client-g3.exe (on Windows only).

ssh-broker-g3 uses the Secure Shell version 2 protocol to communicate with a Secure Shell server.

You can start the Connection Broker manually by using the ssh-broker-g3 command. This starts ssh-broker-g3 in the background and all following uses of sshg3, sftpg3, or scpg3 will connect via this instance of the Connection Broker instead of starting a new Broker session.

If a command-line client (sshg3, sftpg3, or scpg3) is started when the Connection Broker is not running in the background, the client starts the Broker in run-on-demand mode. In this mode, ssh-broker-g3 will exit after the last client has disconnected.

If there is an ssh-broker-g3 process running in the run-on-demand mode, and the Connection Broker is started from the command line, the new ssh-broker-g3 process sends a message to the old ssh-broker-g3 process to change from the run-on-demand mode to the background mode, keeping the Broker running after the clients disconnect.

The status of the running Connection Broker can be checked using the ssh-broker-ctl and ssh-broker-gui utilities.

Authentication

The Connection Broker operates automatically as an authentication agent, storing user's public keys and forwarding the authentication over Secure Shell connections. Key pairs can be created with ssh-keygen-g3.

The Connection Broker can also serve OpenSSH clients as an authentication agent.

The public key pairs used for user authentication are by default stored in the $HOME/.ssh2 directory (%APPDATA%\SSH\UserKeys on Windows). See the section called “Files” for more information.

The Connection Broker automatically maintains and checks a database containing the public host keys used for authenticating Secure Shell servers. When logging in to a server host for the first time, the host's public key is stored in the user's $HOME/.ssh2/hostkeys directory (%APPDATA%\SSH\HostKeys on Windows). See the section called “Files” for more information.

Options

The most important options of ssh-broker-g3 are the following:

-a, --broker-address=ADDR

Listens to Connection Broker connections on a local address ADDR.

-D, --debug=LEVEL

Sets the debug level string to LEVEL.

-f, --config-file=FILE

Reads the Connection Broker configuration file from FILE instead of the default location.

-l, --debug-log-file=FILE

Dumps debug messages to FILE.

--pid-file=FILE

Stores the process ID of the Connection Broker to FILE.

--exit

Make the currently running Connection Broker exit. This will terminate all connections.

--reconfig

Re-reads the configuration file (ssh-broker-config.xml) and takes it into use.

-V, --version

Displays program version and exits.

-h, --help

Displays a short summary of command-line options and exits.

Environment Variables

The following optional environment variables are required in certain situations:

SSH_SECSH_BROKER=ADDRESS

This variable defines an address to a separate Tectia Connection Broker process to which a connection is made.

This variable becomes necessary to define the location of the Connection Broker process, if you are running it from a non-default location, or using a userID other than that of the ssh-broker-g3 process owner.

Files

ssh-broker-g3 uses the following files:

$HOME/.ssh2/ssh-broker-config.xml

This is the user-specific configuration file used by ssh-broker-g3 (and sshg3, scpg3, and sftpg3). The format of this file is described in ssh-broker-config(5). This file does not usually contain any sensitive information, but the recommended permissions are read/write for the user, and not accessible for others.

On Windows, the user-specific configuration file is located in %APPDATA%\SSH\ssh-broker-config.xml.

$HOME/.ssh2/random_seed

This file is used for seeding the random number generator. It contains sensitive data and its permissions should be read/write for the user and not accessible for others. This file is created the first time the program is run and it is updated automatically. You should never need to read or modify this file.

On Windows, the random seed file is located in %APPDATA%\SSH\random_seed.

$HOME/.ssh2/identification

This file contains information on public keys and certificates used for user authentication when contacting remote hosts.

With Tectia Client G3, using the identification file is not necessary if all user keys are stored in the default directory and you allow all of them to be used for public-key and/or certificate authentication. If the identification file does not exist, the Connection Broker attempts to use each key found in the $HOME/.ssh2 directory. If the identification file exists, the keys listed in it are attempted first.

The identification file contains a list of private key filenames each preceded by the keyword IdKey (or CertKey). An example file is shown below:

IdKey       mykey

This directs the Connection Broker to use $HOME/.ssh2/mykey when attempting login using public-key authentication.

The files are by default assumed to be in the $HOME/.ssh2 directory, but also a path to the key file can be given. The path can be absolute or relative to the $HOME/.ssh2 directory. If there is more than one IdKey, they are tried in the order that they appear in the identification file.

On Windows, the identification file is located in %APPDATA%\SSH\identification. Key paths in the file can be absolute or relative to the %APPDATA%\SSH directory. The default user key directory is %APPDATA%\SSH\UserKeys and the default user certificate directory is %APPDATA%\SSH\UserCertificates.

$HOME/.ssh2/hostkeys

This is the user-specific default directory for storing the public keys of server hosts. You are prompted to accept new or changed keys automatically when you connect to a server, unless you have set strict-host-key-checking to yes in the ssh-broker-config.xml file. You should verify the key fingerprint before accepting new or changed keys.

When the host key is received during the first connection to a remote host (or when the host key has changed) and you choose to save the key, its filename is stored by default in hashed format. The hashed host key format is a security feature to make address harvesting on the hosts difficult.

The storage format can be controlled with the filename-format attribute of the known-hosts element in the ssh-broker-config.xml configuration file. The attribute value must be plain or hash (default).

If you are adding the keys manually, the keys should be named with key_<port>_<host>.pub pattern, where <port> is the port the Secure Shell server is running on and <host> is the hostname you use when connecting to the server (for example, key_22_alpha.example.com.pub).

If both hashed and plain-text format keys exist, the hashed format takes precedence.

Note that the identification is different based on the host and port the client is connecting to. For example, the short hostname alpha is considered different from the fully qualified domain name alpha.example.com. Also a connection with an IP, for example 10.1.54.1, is considered a different host, as is a connection to the same host but different port, for example alpha.example.com#222.

On Windows, the user-specific host key files are located in %APPDATA%\SSH\HostKeys.

For more information on host keys, see Server Authentication with Public Keys.

$HOME/.ssh2/hostkeys/salt

This is the initialization file for hashed host key names.

On Windows, the salt file is located in %APPDATA%\SSH\HostKeys\salt.

/opt/tectia/share/auxdata/ssh-broker-ng/ssh-broker-config-default.xml

This is the configuration file used by ssh-broker-g3 (and sshg3, scpg3, and sftpg3) that contains the factory default settings. It is not recommended to edit the file, but you can use it to view the default settings. The format of this file is described in ssh-broker-config(5).

On Windows, the default configuration file is located in <INSTALLDIR>\SSH Tectia AUX\ssh-broker-ng\ssh-broker-config-default.xml.

/etc/ssh2/ssh-broker-config.xml

This is the global (system-wide) configuration file used by ssh-broker-g3 (and sshg3, scpg3, and sftpg3). The format of this file is described in ssh-broker-config(5).

On Windows, the global configuration file is located in <INSTALLDIR>\SSH Tectia Broker\ssh-broker-config.xml.

/etc/ssh2/hostkeys

If a host key is not found in the user-specific $HOME/.ssh2/hostkeys directory, this is the next location to be checked for all users. Host key files are not automatically put here but they have to be updated manually by the system administrator (root).

If the administrator obtains the host keys by connecting to each host, the keys will be by default in the hashed format. In this case, also the administrator's $HOME/.ssh2/hostkeys/salt file has to be copied to the /etc/ssh2/hostkeys directory.

On Windows, the system-wide host key files are by default located in:

"C:\Documents and Settings\All Users\Application Data\SSH\HostKeys" on pre-Vista Windows.

"C:\ProgramData\SSH\HostKeys" on Windows Vista and later Windows versions.

/etc/ssh2/hostkeys/salt

This is the initialization file for hashed host key names. The file has to be copied here manually by the same administrator that obtains the host keys.

On Windows, the salt file for all users is by default located in:

"C:\Documents and Settings\All Users\Application Data\SSH\HostKeys\salt" on pre-Vista Windows.

"C:\ProgramData\SSH\HostKeys\salt" on Windows Vista and later Windows versions.

/etc/ssh/ssh_known_hosts

This is the default system-wide file used by OpenSSH clients for storing the public key data of known server hosts. It is supported also by Tectia Client.

If a host key is not found in the user-specific $HOME/.ssh/known_hosts file, this is the next location to be checked for all users.

The ssh_known_hosts file is never automatically updated by Tectia Client or ConnectSecure, since they store new host keys always in the Tectia user-specific directory $HOME/.ssh2/hostkeys.

$HOME/.ssh/known_hosts

This is the default user-specific file used by OpenSSH clients for storing the public key data of known server hosts. The known_hosts file is supported also by Tectia Client.

The known_hosts file contains a hashed or plain-text format entry of each known host key and the port used on the server, in case it is non-standard (other than 22). For more information on the format of the known_hosts file, see the OpenSSH sshd(8) man page.

The known_hosts file is never automatically updated by Tectia Client or ConnectSecure, since they store new host keys always in the Tectia directory $HOME/.ssh2/hostkeys.

$HOME/.ssh2/authorized_keys (on the server host)

This directory is the default location used by Tectia Server for the user public keys that are authorized for login.

On Tectia Server on Windows, the default directory for user public keys is %USERPROFILE%\.ssh2\authorized_keys.

$HOME/.ssh2/authorization (on the server host)

This is the default file used by earlier versions of Tectia Server (sshd2) that lists the user public keys that are authorized for login. The file can optionally be used with Tectia Server G3 (ssh-server-g3) as well.

On Tectia Server on Windows, the authorization file is by default located in %USERPROFILE%\.ssh2\authorization.

For information on the format of this file, see the ssh-server-g3(8) man page.

$HOME/.ssh/authorized_keys (on the server host)

This is the default file used by OpenSSH server (sshd) that contains the user public keys that are authorized for login.

For information on the format of this file, see the OpenSSH sshd(8) man page.