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NAME

       ssh_file  -  Default  callback module for the client's and server's database operations in
       the ssh application

DESCRIPTION

       This module is the default callback handler for the client's and  the  server's  user  and
       host  "database"  operations. All data, for instance key pairs, are stored in files in the
       normal file system. This page documents the files, where they are stored and configuration
       options for this callback module.

       The  intention  is to be compatible with the OpenSSH storage in files. Therefore it mimics
       directories and filenames of OpenSSH.

       Ssh_file implements the ssh_server_key_api and the ssh_client_key_api.  This  enables  the
       user to make an own interface using for example a database handler.

       Such  another  callback  module could be used by setting the option key_cb when starting a
       client or a server (with for example ssh:connect, ssh:daemon of ssh:shell ).

   Note:
       The functions are Callbacks  for the SSH app. They are not intended to be called from  the
       user's code!

FILES, DIRECTORIES AND WHO USES THEM

   Daemons
       Daemons uses all files stored in the SYSDIR directory.

       Optionaly,  in  case  of  publickey authorization, one or more of the remote user's public
       keys in the  USERDIR  directory  are  used.  See  the  files  USERDIR/authorized_keys  and
       USERDIR/authorized_keys2.

   Clients
       Clients uses all files stored in the USERDIR directory.

   Directory contents
         LOCALUSER:
           The user name of the OS process running the Erlang virtual machine (emulator).

         SYSDIR:
           This is the directory holding the server's files:

           * ssh_host_dsa_key - private dss host key (optional)

           * ssh_host_rsa_key - private rsa host key (optional)

           * ssh_host_ecdsa_key - private ecdsa host key (optional)

           * ssh_host_ed25519_key - private eddsa host key for curve 25519 (optional)

           * ssh_host_ed448_key - private eddsa host key for curve 448 (optional)

           At least one host key must be defined. The default value of SYSDIR is /etc/ssh.

           For security reasons, this directory is normally accessible only to the root user.

           To change the SYSDIR, see the system_dir option.

         USERDIR:
           This is the directory holding the files:

           * authorized_keys and, as second alternative authorized_keys2 - the user's public keys
             are stored concatenated in one of those files.

           * known_hosts - host keys from hosts visited concatenated. The  file  is  created  and
             used by the client.

           * id_dsa - private dss user key (optional)

           * id_rsa - private rsa user key (optional)

           * id_ecdsa - private ecdsa user key (optional)

           * id_ed25519 - private eddsa user key for curve 25519 (optional)

           * id_ed448 - private eddsa user key for curve 448 (optional)

           The default value of USERDIR is /home/LOCALUSER/.ssh.

           To change the USERDIR, see the user_dir option

DATA TYPES

   Options for the default ssh_file callback module
       user_dir_common_option() = {user_dir, string()}

              Sets the user directory.

       user_dir_fun_common_option() = {user_dir_fun, user2dir()}

       user2dir() =
           fun((RemoteUserName :: string()) -> UserDir :: string())

              Sets the user directory dynamically by evaluating the user2dir function.

       system_dir_daemon_option() = {system_dir, string()}

              Sets the system directory.

       pubkey_passphrase_client_options() =
           {dsa_pass_phrase, string()} |
           {rsa_pass_phrase, string()} |
           {ecdsa_pass_phrase, string()}

              If  the  user's  DSA,  RSA  or  ECDSA  key  is protected by a passphrase, it can be
              supplied with thoose options.

              Note that EdDSA passhrases (Curves 25519 and 448) are not implemented.

EXPORTS

       host_key(Algorithm, DaemonOptions) -> {ok, Key} | {error, Reason}

              Types and description

              See the api description in ssh_server_key_api, Module:host_key/2.

              Options

                * system_dir

              Files

                * SYSDIR/ssh_host_rsa_key

                * SYSDIR/ssh_host_dsa_key

                * SYSDIR/ssh_host_ecdsa_key

                * SYSDIR/ssh_host_ed25519_key

                * SYSDIR/ssh_host_ed448_keyc>

       is_auth_key(PublicUserKey, User, DaemonOptions) -> Result

              Types and description

              See the api description in ssh_server_key_api: Module:is_auth_key/3.

              Options

                * user_dir_fun

                * user_dir

              Files

                * USERDIR/authorized_keys

                * USERDIR/authorized_keys2

       add_host_key(HostNames, PublicHostKey, ConnectOptions) -> ok | {error, Reason}

              Types and description

              See the api description in ssh_client_key_api, Module:add_host_key/3.

              Option

                * user_dir

              File

                * USERDIR/known_hosts

       is_host_key(Key, Host, Algorithm, ConnectOptions) -> Result

              Types and description

              See the api description in ssh_client_key_api, Module:is_host_key/4.

              Option

                * user_dir

              File

                * USERDIR/known_hosts

       user_key(Algorithm, ConnectOptions) -> {ok, PrivateKey} | {error, Reason}

              Types and description

              See the api description in ssh_client_key_api, Module:user_key/2.

              Options

                * user_dir

                * dsa_pass_phrase

                * rsa_pass_phrase

                * ecdsa_pass_phrase

              Note that EdDSA passhrases (Curves 25519 and 448) are not implemented.

              Files

                * USERDIR/id_dsa

                * USERDIR/id_rsa

                * USERDIR/id_ecdsa

                * USERDIR/id_ed25519

                * USERDIR/id_ed448