ssh

Interface module for the SSH application.

• ssh requires the crypto and public_key applications.
• Supported SSH-version is 2.0
• Currently supports only a minimum of mac and encryption algorithms i.e. hmac-sha1, and aes128-cb and 3des-cbc.

Type definitions that are used more than once in this module:

boolean() = true | false

string() = list of ASCII characters

ssh_daemon_ref() - opaque to the user returned by ssh:daemon/[1,2,3]

ssh_connection_ref() - opaque to the user returned by ssh:connect/3

ip_address() - {N1,N2,N3,N4} % IPv4 | {K1,K2,K3,K4,K5,K6,K7,K8} % IPv6

subsystem_spec() = {subsystem_name(), {channel_callback(), channel_init_args()}}

subsystem_name() = string()

channel_callback() = atom() - Name of the erlang module implementing the subsystem using the ssh_channel behavior see ssh_channel(3)

channel_init_args() = list()

Types:

Closes a ssh connection.

Types:

Connects to an SSH server. No channel is started this is done by calling ssh_connect:session_channel/2.

Options are:

{user_dir, string()}

Sets the user directory e.i. the directory containing ssh configuration files for the user such as known_hosts, id_rsa, id_dsa and authorized_key. Defaults to the directory normally referred to as ~/.ssh

{dsa_pass_phrase, string()}

If the user dsa key is protected by a pass phrase it can be supplied with this option.

{rsa_pass_phrase, string()}

If the user rsa key is protected by a pass phrase it can be supplied with this option.

{silently_accept_hosts, boolean()}

When true hosts are added to the file known_hosts without asking the user. Defaults to false.

{user_interaction, boolean()}

If false disables the client to connect to the server if any user interaction is needed such as accepting that the server will be added to the known_hosts file or supplying a password. Defaults to true. Even if user interaction is allowed it can be suppressed by other options such as silently_accept_hosts and password. Do note that it may not always be desirable to use those options from a security point of view.

{public_key_alg, ssh_rsa | ssh_dsa}

Sets the preferred public key algorithm to use for user authentication. If the the preferred algorithm fails of some reason, the other algorithm is tried. The default is to try ssh_rsa first.

{connect_timeout, timeout()}

Sets a timeout on the transport layer connection. Defaults to infinity.

{user, String}

Provide a user name. If this option is not given, ssh reads from the environment (LOGNAME or USER on unix, USERNAME on Windows).

{password, string()}

Provide a password for password authentication. If this option is not given, the user will be asked for a password if the password authentication method is attempted.

{user_auth, Fun/3}

Provide a fun for password authentication. The fun will be called as fun(User, Password, Opts) and should return true or false.

{key_cb, atom() = KeyCallbackModule}

Provide a special call-back module for key handling. The call-back module should be modeled after the ssh_file module. The functions that must be exported are: private_host_rsa_key/2, private_host_dsa_key/2, lookup_host_key/3 and add_host_key/3. This is considered somewhat experimental and will be better documented later on.

{fd, file_descriptor()}

Allow an existing file-descriptor to be used (simply passed on to the transport protocol).

{ip_v6_disabled, boolean()}

Determines if SSH shall use IPv6 or not.

Types:

Retrieves information about a connection.

Types:

Starts a server listening for SSH connections on the given port.

Options are:

{subsystems, [subsystem_spec()]

Provides specifications for handling of subsystems. The "sftp" subsystem-spec can be retrieved by calling ssh_sftpd:subsystem_spec/1. If the subsystems option in not present the value of [ssh_sftpd:subsystem_spec([])] will be used. It is of course possible to set the option to the empty list if you do not want the daemon to run any subsystems at all.

{shell, {Module, Function, Args} | fun(string() = User) - > pid() | fun(string() = User, ip_address() = PeerAddr) -> pid()}

Defines the read-eval-print loop used when a shell is requested by the client. Example use the erlang shell: {shell, start, []} which is the default behavior.

{ssh_cli,{channel_callback(), channel_init_args()}}

Provide your own cli implementation, e.i. a channel callback module that implements a shell and command execution. Note that you may customize the shell read-eval-print loop using the option shell which is much less work than implementing your own cli channel.

{user_dir, String}

Sets the user directory e.i. the directory containing ssh configuration files for the user such as known_hosts, id_rsa, id_dsa and authorized_key. Defaults to the directory normally referred to as ~/.ssh

{system_dir, string()}

Sets the system directory, containing the host files that identifies the host for ssh. The default is /etc/ssh, note that SSH normally requires the host files there to be readable only by root.

{user_passwords, [{string() = User, string() = Password}]}

Provide passwords for password authentication.They will be used when someone tries to connect to the server and public key user authentication fails. The option provides a list of valid user names and the corresponding password.

{password, string()}

Provide a global password that will authenticate any user. From a security perspective this option makes the server very vulnerable.

{pwdfun, fun/2}

Provide a function for password validation. This is called with user and password as strings, and should return true if the password is valid and false otherwise.

{fd, file_descriptor()}

Allow an existing file-descriptor to be used (simply passed on to the transport protocol).

{ip_v6_disabled, boolean()}

Determines if SSH shall use IPv6 or not (only used when HostAddress is set to any).

Types:

Starts an interactive shell to an SSH server on the given Host. The function waits for user input, and will not return until the remote shell is ended (e.g. on exit from the shell).

Types:

Starts the Ssh application. Default type is temporary. See also application(3) Requires that the crypto application has been started.

Stops the Ssh application. See also application(3)

Types:

Stops the listener and all connections started by the listener.

Types:

Stops the listener, but leaves existing connections started by the listener up and running.