diff options
Diffstat (limited to 'lib/ssh/doc/src')
| -rw-r--r-- | lib/ssh/doc/src/Makefile | 3 | ||||
| -rw-r--r-- | lib/ssh/doc/src/ref_man.xml | 1 | ||||
| -rw-r--r-- | lib/ssh/doc/src/specs.xml | 1 | ||||
| -rw-r--r-- | lib/ssh/doc/src/ssh.xml | 72 | ||||
| -rw-r--r-- | lib/ssh/doc/src/ssh_app.xml | 7 | ||||
| -rw-r--r-- | lib/ssh/doc/src/ssh_file.xml | 275 | ||||
| -rw-r--r-- | lib/ssh/doc/src/terminology.xml | 185 | ||||
| -rw-r--r-- | lib/ssh/doc/src/usersguide.xml | 1 | ||||
| -rw-r--r-- | lib/ssh/doc/src/using_ssh.xml | 11 |
9 files changed, 499 insertions, 57 deletions
diff --git a/lib/ssh/doc/src/Makefile b/lib/ssh/doc/src/Makefile index 77fa356092..4e32dd9976 100644 --- a/lib/ssh/doc/src/Makefile +++ b/lib/ssh/doc/src/Makefile @@ -45,6 +45,7 @@ XML_REF3_FILES = \ ssh_connection.xml \ ssh_server_channel.xml \ ssh_server_key_api.xml \ + ssh_file.xml \ ssh_sftp.xml \ ssh_sftpd.xml \ @@ -56,8 +57,8 @@ XML_CHAPTER_FILES = \ notes.xml \ introduction.xml \ using_ssh.xml \ + terminology.xml \ configure_algos.xml -# ssh_protocol.xml \ BOOK_FILES = book.xml diff --git a/lib/ssh/doc/src/ref_man.xml b/lib/ssh/doc/src/ref_man.xml index df37b0244f..60572b985b 100644 --- a/lib/ssh/doc/src/ref_man.xml +++ b/lib/ssh/doc/src/ref_man.xml @@ -40,6 +40,7 @@ <xi:include href="ssh_connection.xml"/> <xi:include href="ssh_client_key_api.xml"/> <xi:include href="ssh_server_key_api.xml"/> + <xi:include href="ssh_file.xml"/> <xi:include href="ssh_sftp.xml"/> <xi:include href="ssh_sftpd.xml"/> </application> diff --git a/lib/ssh/doc/src/specs.xml b/lib/ssh/doc/src/specs.xml index acdbe2ddfd..a6517f3660 100644 --- a/lib/ssh/doc/src/specs.xml +++ b/lib/ssh/doc/src/specs.xml @@ -6,6 +6,7 @@ <xi:include href="../specs/specs_ssh_connection.xml"/> <xi:include href="../specs/specs_ssh_server_channel.xml"/> <xi:include href="../specs/specs_ssh_server_key_api.xml"/> + <xi:include href="../specs/specs_ssh_file.xml"/> <xi:include href="../specs/specs_ssh_sftp.xml"/> <xi:include href="../specs/specs_ssh_sftpd.xml"/> </specs> diff --git a/lib/ssh/doc/src/ssh.xml b/lib/ssh/doc/src/ssh.xml index f238bf2ca8..b75b4a33c2 100644 --- a/lib/ssh/doc/src/ssh.xml +++ b/lib/ssh/doc/src/ssh.xml @@ -99,8 +99,8 @@ </p> <p>The paths could easily be changed by options: - <seealso marker="#type-user_dir_common_option"><c>user_dir</c></seealso> and - <seealso marker="#type-system_dir_daemon_option"><c>system_dir</c></seealso>. + <seealso marker="ssh_file#type-user_dir_common_option"><c>user_dir</c></seealso> and + <seealso marker="ssh_file#type-system_dir_daemon_option"><c>system_dir</c></seealso>. </p> <p>A completly different storage could be interfaced by writing call-back modules using the behaviours @@ -123,12 +123,12 @@ <item><c>ssh_host_ecdsa_key</c> and <c>ssh_host_ecdsa_key.pub</c></item> </list> <p>The host keys directory could be changed with the option - <seealso marker="#type-system_dir_daemon_option"><c>system_dir</c></seealso>.</p> + <seealso marker="ssh_file#type-system_dir_daemon_option"><c>system_dir</c></seealso>.</p> </item> <item>Optional: one or more <i>User's public key</i> in case of <c>publickey</c> authorization. Default is to store them concatenated in the file <c>.ssh/authorized_keys</c> in the user's home directory. <p>The user keys directory could be changed with the option - <seealso marker="#type-user_dir_common_option"><c>user_dir</c></seealso>.</p> + <seealso marker="ssh_file#type-user_dir_common_option"><c>user_dir</c></seealso>.</p> </item> </list> </section> @@ -138,7 +138,7 @@ <p>The keys and some other data are by default stored in files in the directory <c>.ssh</c> in the user's home directory.</p> <p>The directory could be changed with the option - <seealso marker="#type-user_dir_common_option"><c>user_dir</c></seealso>. + <seealso marker="ssh_file#type-user_dir_common_option"><c>user_dir</c></seealso>. </p> <list> <item>Optional: a list of <i>Host public key(s)</i> for previously connected hosts. This list @@ -192,22 +192,13 @@ <p>If there is no public key of a specified type available, the corresponding entry is ignored. Note that the available set is dependent on the underlying cryptolib and current user's public keys. </p> - <p>See also the option <seealso marker="#type-user_dir_common_option"><c>user_dir</c></seealso> + <p>See also the option <seealso marker="ssh_file#type-user_dir_common_option"><c>user_dir</c></seealso> for specifying the path to the user's keys. </p> </desc> </datatype> <datatype> - <name name="pubkey_passphrase_client_options"/> - <desc> - <p>If the user's DSA, RSA or ECDSA key is protected by a passphrase, it can be - supplied with thoose options. - </p> - </desc> - </datatype> - - <datatype> <name name="host_accepting_client_options"/> <name name="accept_hosts"/> <name name="fp_digest_alg"/> @@ -220,7 +211,7 @@ <p>This option guides the <c>connect</c> function on how to act when the connected server presents a Host Key that the client has not seen before. The default is to ask the user with a question on stdio of whether to accept or reject the new Host Key. - See the option <seealso marker="#type-user_dir_common_option"><c>user_dir</c></seealso> + See the option <seealso marker="ssh_file#type-user_dir_common_option"><c>user_dir</c></seealso> for specifying the path to the file <c>known_hosts</c> where previously accepted Host Keys are recorded. See also the option <seealso marker="#type-key_cb_common_option">key_cb</seealso> @@ -276,7 +267,7 @@ accept question the next time the same host is connected. If the option <seealso marker="#type-key_cb_common_option"><c>key_cb</c></seealso> is not present, the key is saved in the file "known_hosts". See option - <seealso marker="#type-user_dir_common_option"><c>user_dir</c></seealso> for + <seealso marker="ssh_file#type-user_dir_common_option"><c>user_dir</c></seealso> for the location of that file. </p> <p>If <c>false</c>, the key is not saved and the key will still be unknown @@ -478,18 +469,6 @@ <name name="pwdfun_4"/> <desc> <taglist> - <tag><marker id="type-system_dir_daemon_option"/><c>system_dir</c></tag> - <item> - <p>Sets the system directory, containing the host key files - that identify the host keys for <c>ssh</c>. Defaults to - <c>/etc/ssh</c>.</p> - <p>For security reasons, this directory is normally accessible only to the root user.</p> - <p>See also the option - <seealso marker="#type-key_cb_common_option">key_cb</seealso> - for the general way to handle keys. - </p> - </item> - <tag><c>auth_method_kb_interactive_data</c></tag> <item> <p>Sets the text strings that the daemon sends to the client for presentation to the user when @@ -502,7 +481,7 @@ </p> </item> - <tag><c>user_passwords</c></tag> + <tag><marker id="option-user_passwords"/><c>user_passwords</c></tag> <item> <p>Provides passwords for password authentication. The passwords are used when someone tries to connect to the server and public key user-authentication fails. The option provides @@ -510,7 +489,7 @@ </p> </item> - <tag><c>password</c></tag> + <tag><marker id="option-password"/><c>password</c></tag> <item> <p>Provides a global password that authenticates any user.</p> <warning> @@ -519,7 +498,9 @@ </warning> </item> - <tag><c>pwdfun</c> with <c>pwdfun_4()</c></tag> + <tag><marker id="option-pwdfun"/><c>pwdfun</c> with + <seealso marker="#type-pwdfun_4"><c>pwdfun_4()</c></seealso> + </tag> <item> <p>Provides a function for password validation. This could used for calling an external system or handeling passwords stored as hash values. @@ -546,7 +527,9 @@ can be used for this. The return value <c>disconnect</c> is useful for this.</p> </item> - <tag><c>pwdfun</c> with <c>pwdfun_2()</c></tag> + <tag><c>pwdfun</c> with + <seealso marker="#type-pwdfun_2"><c>pwdfun_2()</c></seealso> + </tag> <item> <p>Provides a function for password validation. This function is called with user and password as strings, and returns:</p> @@ -725,21 +708,6 @@ </datatype> <datatype> - <name name="user_dir_common_option"/> - <desc> - <p>Sets the user directory. That is, the directory containing <c>ssh</c> configuration - files for the user, such as - <c>known_hosts</c>, <c>id_rsa</c>, <c>id_dsa</c>>, <c>id_ecdsa</c> and <c>authorized_key</c>. - Defaults to the directory normally referred to as <c>~/.ssh</c>. - </p> - <p>See also the option - <seealso marker="#type-key_cb_common_option">key_cb</seealso> - for the general way to handle keys. - </p> - </desc> - </datatype> - - <datatype> <name name="profile_common_option"/> <desc> <p>Used together with <c>ip-address</c> and <c>port</c> to @@ -795,7 +763,8 @@ </p> <p>The <c>Opts</c> defaults to <c>[]</c> when only the <c>Module</c> is specified. </p> - <p>The default value of this option is <c>{ssh_file, []}</c>. + <p>The default value of this option is <c>{ssh_file, []}</c>. See also the manpage of + <seealso marker="ssh:ssh_file">ssh_file</seealso>. </p> <p>A call to the call-back function <c>F</c> will be</p> <code> @@ -804,7 +773,10 @@ <p>where <c>...</c> are arguments to <c>F</c> as in <seealso marker="ssh_client_key_api">ssh_client_key_api</seealso> and/or <seealso marker="ssh_server_key_api">ssh_server_key_api</seealso>. - The <c>UserOptions</c> are the options given to <c>ssh:connect</c>, <c>ssh:shell</c> or <c>ssh:daemon</c>. + The <c>UserOptions</c> are the options given to + <seealso marker="ssh:ssh#connect-3">ssh:connect</seealso>, + <seealso marker="ssh:ssh#shell-1">ssh:shell</seealso> or + <seealso marker="ssh:ssh#daemon-2">ssh:daemon</seealso>. </p> </desc> diff --git a/lib/ssh/doc/src/ssh_app.xml b/lib/ssh/doc/src/ssh_app.xml index e80bb1853d..eb804e67dc 100644 --- a/lib/ssh/doc/src/ssh_app.xml +++ b/lib/ssh/doc/src/ssh_app.xml @@ -74,13 +74,18 @@ <c>id_ecdsa_key</c>, <c>known_hosts</c>, and <c>authorized_keys</c> in ~/.ssh, and for the host key files in <c>/etc/ssh</c>. These locations can be changed - by the options <c>user_dir</c> and <c>system_dir</c>. + by the options + <seealso marker="ssh_file#type-user_dir_common_option"><c>user_dir</c></seealso> and + <seealso marker="ssh_file#type-system_dir_daemon_option"><c>system_dir</c></seealso>. </p> <p>Public key handling can also be customized through a callback module that implements the behaviors <seealso marker="ssh_client_key_api">ssh_client_key_api</seealso> and <seealso marker="ssh_server_key_api">ssh_server_key_api</seealso>. </p> + <p>See also the default callback module documentation in + <seealso marker="ssh_file">ssh_file</seealso>. + </p> </section> <section> diff --git a/lib/ssh/doc/src/ssh_file.xml b/lib/ssh/doc/src/ssh_file.xml new file mode 100644 index 0000000000..ae6ba2e1d9 --- /dev/null +++ b/lib/ssh/doc/src/ssh_file.xml @@ -0,0 +1,275 @@ +<?xml version="1.0" encoding="utf-8" ?> +<!DOCTYPE erlref SYSTEM "erlref.dtd"> + +<erlref> + <header> + <copyright> + <year>2018</year><year>2018</year> + <holder>Ericsson AB. All Rights Reserved.</holder> + </copyright> + <legalnotice> + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + + </legalnotice> + + <title>ssh_file</title> + <prepared></prepared> + <docno></docno> + <date></date> + <rev></rev> + </header> + <module>ssh_file</module> + <modulesummary>Default callback module for the client's and server's database operations in the ssh application</modulesummary> + <description> + <p>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. + </p> + <p>The intention is to be compatible with the + <url href="http://www.openssh.com">OpenSSH</url> + storage in files. Therefore it mimics directories and filenames of + <url href="http://www.openssh.com">OpenSSH</url>. + </p> + + <p>Ssh_file implements the <seealso marker="ssh:ssh_server_key_api">ssh_server_key_api</seealso> and + the <seealso marker="ssh:ssh_client_key_api">ssh_client_key_api</seealso>. + This enables the user to make an own interface using for example a database handler. + </p> + <p>Such another callback module could be used by setting the option + <seealso marker="ssh:ssh#type-key_cb_common_option"><c>key_cb</c></seealso> + when starting a client or a server (with for example + <seealso marker="ssh:ssh#connect-3">ssh:connect</seealso>, + <seealso marker="ssh:ssh#daemon-2">ssh:daemon</seealso> of + <seealso marker="ssh:ssh#shell-1">ssh:shell</seealso> + ). + </p> + + <note> + <p>The functions are <i>Callbacks</i> for the SSH app. They are not intended to be called from the user's code! + </p> + </note> + </description> + + <section> + <title>Files, directories and who uses them</title> + <section> + <title>Daemons</title> + <p>Daemons uses all files stored in the <seealso marker="#SYSDIR">SYSDIR</seealso> directory. + </p> + <p>Optionaly, in case of <c>publickey</c> authorization, one or more of the remote user's public keys + in the <seealso marker="#USERDIR">USERDIR</seealso> directory are used. + See the files + <seealso marker="#USERDIR-authorized_keys"><c>USERDIR/authorized_keys</c></seealso> and + <seealso marker="#USERDIR-authorized_keys2"><c>USERDIR/authorized_keys2</c></seealso>. + </p> + </section> + + <section> + <title>Clients</title> + <p>Clients uses all files stored in the <seealso marker="#USERDIR">USERDIR</seealso> directory. + </p> + </section> + + <section> + <title>Directory contents</title> + <taglist> + <tag><marker id="LOCALUSER"/>LOCALUSER</tag> + <item><p>The user name of the OS process running the Erlang virtual machine (emulator).</p> + </item> + + <tag><marker id="SYSDIR"/>SYSDIR</tag> + <item><p>This is the directory holding the server's files:</p> + <list> + <item><marker id="SYSDIR-ssh_host_dsa_key"/><c>ssh_host_dsa_key</c> - private dss host key (optional)</item> + <item><marker id="SYSDIR-ssh_host_rsa_key"/><c>ssh_host_rsa_key</c> - private rsa host key (optional)</item> + <item><marker id="SYSDIR-ssh_host_ecdsa_key"/><c>ssh_host_ecdsa_key</c> - private ecdsa host key (optional)</item> + </list> + <p>At least one host key must be defined. The default value of SYSDIR is <marker id="#/etc/ssh"/><c>/etc/ssh</c>. + </p> + <p>For security reasons, this directory is normally accessible only to the root user. + </p> + <p>To change the SYSDIR, see the <seealso marker="#type-system_dir_daemon_option">system_dir</seealso> option. + </p> + </item> + + <tag><marker id="USERDIR"/>USERDIR</tag> + <item><p>This is the directory holding the files:</p> + <list> + <item><marker id="USERDIR-authorized_keys"/><c>authorized_keys</c> + and, as second alternative + <marker id="USERDIR-authorized_keys2"/><c>authorized_keys2</c> - + the user's public keys are stored concatenated in one of those files. + </item> + <item><marker id="USERDIR-known_hosts"/><c>known_hosts</c> - host keys from hosts visited + concatenated. The file is created and used by the client.</item> + <item><marker id="USERDIR-id_dsa"/><c>id_dsa</c> - private dss user key (optional)</item> + <item><marker id="USERDIR-id_rsa"/><c>id_rsa</c> - private rsa user key (optional)</item> + <item><marker id="USERDIR-id_ecdsa"/><c>id_ecdsa</c> - private ecdsa user key (optional)</item> + </list> + <p>The default value of USERDIR is <c>/home/</c><seealso marker="#LOCALUSER"><c>LOCALUSER</c></seealso><c>/.ssh</c>. + </p> + <p>To change the USERDIR, see the <seealso marker="#type-user_dir_common_option">user_dir</seealso> option + </p> + </item> + </taglist> + </section> + </section> + + <datatypes> + <datatype_title>Options for the default ssh_file callback module</datatype_title> + <datatype> + <name name="user_dir_common_option"/> + <desc> + <p>Sets the <seealso marker="#USERDIR">user directory</seealso>.</p> + </desc> + </datatype> + + <datatype> + <name name="user_dir_fun_common_option"/> + <name name="user2dir"/> + <desc> + <p>Sets the <seealso marker="#USERDIR">user directory</seealso> dynamically + by evaluating the <c>user2dir</c> function. + </p> + </desc> + </datatype> + + <datatype> + <name name="system_dir_daemon_option"/> + <desc> + <p>Sets the <seealso marker="#SYSDIR">system directory</seealso>.</p> + </desc> + </datatype> + + <datatype> + <name name="pubkey_passphrase_client_options"/> + <desc> + <p>If the user's DSA, RSA or ECDSA key is protected by a passphrase, it can be + supplied with thoose options. + </p> + </desc> + </datatype> + + </datatypes> + + <funcs> + <func> + <name>host_key(Algorithm, DaemonOptions) -> {ok, Key} | {error, Reason}</name> + <fsummary></fsummary> + <desc> + <p><strong>Types and description</strong></p> + <p>See the api description in + <seealso marker="ssh:ssh_server_key_api#Module:host_key-2">ssh_server_key_api, Module:host_key/2</seealso>. + </p> + <p><strong>Options</strong></p> + <list> + <item><seealso marker="#type-system_dir_daemon_option">system_dir</seealso></item> + <!-- item>dsa_pass_phrase</item --> + <!-- item>rsa_pass_phrase</item --> + <!-- item>ecdsa_pass_phrase</item --> + </list> + <p><strong>Files</strong></p> + <list> + <item><seealso marker="#SYSDIR-ssh_host_rsa_key"><c>SYSDIR/ssh_host_rsa_key</c></seealso></item> + <item><seealso marker="#SYSDIR-ssh_host_dsa_key"><c>SYSDIR/ssh_host_dsa_key</c></seealso></item> + <item><seealso marker="#SYSDIR-ssh_host_ecdsa_key"><c>SYSDIR/ssh_host_ecdsa_key</c></seealso></item> + </list> + </desc> + </func> + + <func> + <name>is_auth_key(PublicUserKey, User, DaemonOptions) -> Result</name> + <fsummary></fsummary> + <desc> + <p><strong>Types and description</strong></p> + <p>See the api description in + <seealso marker="ssh:ssh_server_key_api#Module:is_auth_key-3">ssh_server_key_api: Module:is_auth_key/3</seealso>. + </p> + <p><strong>Options</strong></p> + <list> + <item><seealso marker="#type-user_dir_fun_common_option">user_dir_fun</seealso></item> + <item><seealso marker="#type-user_dir_common_option">user_dir</seealso></item> + </list> + <p><strong>Files</strong></p> + <list> + <item><seealso marker="#USERDIR-authorized_keys"><c>USERDIR/authorized_keys</c></seealso></item> + <item><seealso marker="#USERDIR-authorized_keys2"><c>USERDIR/authorized_keys2</c></seealso></item> + </list> + </desc> + </func> + + <func> + <name>add_host_key(HostNames, PublicHostKey, ConnectOptions) -> ok | {error, Reason}</name> + <fsummary></fsummary> + <desc> + <p><strong>Types and description</strong></p> + <p>See the api description in + <seealso marker="ssh:ssh_client_key_api#Module:add_host_key-3">ssh_client_key_api, Module:add_host_key/3</seealso>. + </p> + <p><strong>Option</strong></p> + <list> + <item><seealso marker="#type-user_dir_common_option">user_dir</seealso></item> + </list> + <p><strong>File</strong></p> + <list> + <item><seealso marker="#USERDIR-known_hosts"><c>USERDIR/known_hosts</c></seealso></item> + </list> + </desc> + </func> + + <func> + <name>is_host_key(Key, Host, Algorithm, ConnectOptions) -> Result</name> + <fsummary></fsummary> + <desc> + <p><strong>Types and description</strong></p> + <p>See the api description in + <seealso marker="ssh:ssh_client_key_api#Module:is_host_key-4">ssh_client_key_api, Module:is_host_key/4</seealso>. + </p> + <p><strong>Option</strong></p> + <list> + <item><seealso marker="#type-user_dir_common_option">user_dir</seealso></item> + </list> + <p><strong>File</strong></p> + <list> + <item><seealso marker="#USERDIR-known_hosts"><c>USERDIR/known_hosts</c></seealso></item> + </list> + </desc> + </func> + + <func> + <name>user_key(Algorithm, ConnectOptions) -> {ok, PrivateKey} | {error, Reason}</name> + <fsummary></fsummary> + <desc> + <p><strong>Types and description</strong></p> + <p>See the api description in + <seealso marker="ssh:ssh_client_key_api#Module:user_key-2">ssh_client_key_api, Module:user_key/2</seealso>. + </p> + <p><strong>Options</strong></p> + <list> + <item><seealso marker="#type-user_dir_common_option">user_dir</seealso></item> + <item><seealso marker="#type-pubkey_passphrase_client_options">dsa_pass_phrase</seealso></item> + <item><seealso marker="#type-pubkey_passphrase_client_options">rsa_pass_phrase</seealso></item> + <item><seealso marker="#type-pubkey_passphrase_client_options">ecdsa_pass_phrase</seealso></item> + </list> + <p><strong>Files</strong></p> + <list> + <item><seealso marker="#USERDIR-id_dsa"><c>USERDIR/id_dsa</c></seealso></item> + <item><seealso marker="#USERDIR-id_rsa"><c>USERDIR/id_rsa</c></seealso></item> + <item><seealso marker="#USERDIR-id_ecdsa"><c>USERDIR/id_ecdsa</c></seealso></item> + </list> + </desc> + </func> + + </funcs> + +</erlref> diff --git a/lib/ssh/doc/src/terminology.xml b/lib/ssh/doc/src/terminology.xml new file mode 100644 index 0000000000..db1e08970d --- /dev/null +++ b/lib/ssh/doc/src/terminology.xml @@ -0,0 +1,185 @@ +<?xml version="1.0" encoding="utf-8" ?> +<!DOCTYPE chapter SYSTEM "chapter.dtd"> + +<chapter> + <header> + <copyright> + <year>2018</year> + <year>2018</year> + <holder>Ericsson AB. All Rights Reserved.</holder> + </copyright> + <legalnotice> + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + + </legalnotice> + + <title>Terminology</title> + <prepared></prepared> + <docno></docno> + <approved></approved> + <date></date> + <rev></rev> + <file>terminology.xml</file> + </header> + + <section> + <title>General Information</title> + <p>In the following terms that may cause confusion are explained. + </p> + </section> + + <section> + <title>The term "user"</title> + <p>A "user" is a term that everyone understands intuitively. However, the understandings may differ which can + cause confusion. + </p> + <p>The term is used differently in <url href="http://www.openssh.com">OpenSSH</url> and SSH in Erlang/OTP. + The reason is the different environments and use cases that are not immediatly obvious. + </p> + <p>This chapter aims at explaining the differences and giving a rationale for why Erlang/OTP handles "user" as + it does. + </p> + + <section> + <title>In OpenSSH</title> + <p>Many have been in contact with the command 'ssh' on a Linux machine (or similar) to remotly log in on + another machine. One types + </p> + <code>ssh host</code> + <p>to log in on the machine named <c>host</c>. The command prompts for your password on the remote <c>host</c> and + then you can read, write and execute as your <i>user name</i> has rights on the remote <c>host</c>. There are + stronger variants with pre-distributed keys or certificates, but that are for now just details in the + authentication process. + </p> + <p>You could log in as the user <c>anotheruser</c> with + </p> + <code>ssh anotheruser@host</code> + <p>and you will then be enabled to act as <c>anotheruser</c> on the <c>host</c> if authorized correctly. + </p> + <p>So what does <i>"your user name has rights"</i> mean? In a UNIX/Linux/etc context it is exactly as that context: + The <i>user</i> could read, write and execute programs according to the OS rules. + In addition, the user has a home directory (<c>$HOME</c>) and there is a <c>$HOME/.ssh/</c> directory + with ssh-specific files. + </p> + <section> + <title>SSH password authentication</title> + <p>When SSH tries to log in to a host, the ssh protocol communicates the user name (as a string) and a password. + The remote ssh server checks that there is such a user defined and that the provided password is acceptable. + </p> + <p>If so, the user is authorized. + </p> + </section> + <section> + <title>SSH public key authentication</title> + <p>This is a stronger method where the ssh protocol brings the user name, the user's public key and some + cryptographic information which we could ignore here. + </p> + <p>The ssh server on the remote host checks: + </p> + <list> + <item>That the <i>user</i> has a home directory,</item> + <item>that home directory contains a .ssh/ directory and</item> + <item>the .ssh/ directory contains the public key just received in the <c>authorized_keys</c> file</item> + </list> + <p>if so, the user is authorized. + </p> + </section> + <section> + <title>The SSH server on UNIX/Linux/etc after a succesful authentication</title> + <p>After a succesful incoming authentication, a new process runs as the just authenticated user.</p> + <p>Next step is to start a service according to the ssh request. In case of a request of a shell, + a new one is started which handles the OS-commands that arrives from the client (that's "you"). + </p> + <p>In case of a sftp request, an sftp server is started in with the user's rights. So it could read, write or delete + files if allowed for that user. + </p> + </section> + </section> + + <section> + <title>In Erlang/OTP SSH</title> + <p>For the Erlang/OTP SSH server the situation is different. The server executes in an Erlang process + in the Erlang emulator which in turn executes in an OS process. The emulator does not try to change its + user when authenticated over the SSH protocol. + So the remote user name is only for authentication purposes in the Erlang/OTP SSH application. + </p> + <section> + <title>Password authentication in Erlang SSH</title> + <p>The Erlang/OTP SSH server checks the user name and password in the following order: + </p> + <list type="ordered"> + <item>If a + <seealso marker="ssh:ssh#option-pwdfun"><c>pwdfun</c></seealso> + is defined, that one is called and the returned boolean is the authentication result. + </item> + <item>Else, if the + <seealso marker="ssh:ssh#option-user_passwords"><c>user_passwords</c></seealso> + option is defined and the username and the password matches, the authentication is a success. + </item> + <item>Else, if the option + <seealso marker="ssh:ssh#option-password"><c>password</c></seealso> + is defined and matches the password the authentication is a success. + Note that the use of this option is not recommended in non-test code. + </item> + </list> + </section> + <section> + <title>Public key authentication in Erlang SSH</title> + <p>The user name, public key and cryptographic data (a signature) that is sent by the client, are used as follows + (some steps left out for clearity): + </p> + <list type="ordered"> + <item>A callback module is selected using the options + <seealso marker="ssh:ssh#type-key_cb_common_option"><c>key_cb</c></seealso>. + </item> + <item>The callback module is used to check that the provided public key is one of the user's pre-stored. + In case of the default callback module, the files <c>authorized_keys</c> and <c>authorized_keys2</c> + are searched in a directory found in the following order: + <list> + <item>If the option + <seealso marker="ssh:ssh_file#type-user_dir_fun_common_option"><c>user_dir_fun</c></seealso> + is defined, that fun is called and the returned directory is used, + </item> + <item>Else, If the option + <seealso marker="ssh:ssh_file#type-user_dir_common_option"><c>user_dir</c></seealso> + is defined, that directory is used, + </item> + <item>Else the subdirectory <c>.ssh</c> in the home directory of the user executing + the OS process of the Erlang emulator is used. + </item> + </list> + If the provided public key is not found, the authentication fails. + </item> + <item>Finally, if the provided public key is found, the signature provided by the client is checked with + the public key. + </item> + </list> + </section> + <section> + <title>The Erlang/OTP SSH server after a succesful authentication</title> + <p>After a successful authentication an <i>Erlang process</i> is handling the service request from the remote + ssh client. The rights of that process are those of the user of the OS process running the Erlang emulator. + </p> + <p>If a shell service request arrives to the server, an <i>Erlang shell</i> is opened in the server's emulator. + The rights in that shell is independent of the just authenticated user. + </p> + <p>In case of an sftp request, an sftp server is started with the rights of the user of the Erlang emulator's OS + process. So with sftp the authenticated user does not influence the rights. + </p> + <p>So after an authentication, the user name is not used anymore and has no influence. + </p> + </section> + </section> + </section> +</chapter> + diff --git a/lib/ssh/doc/src/usersguide.xml b/lib/ssh/doc/src/usersguide.xml index 38ffa48cde..8a4df208d8 100644 --- a/lib/ssh/doc/src/usersguide.xml +++ b/lib/ssh/doc/src/usersguide.xml @@ -36,5 +36,6 @@ </description> <xi:include href="introduction.xml"/> <xi:include href="using_ssh.xml"/> + <xi:include href="terminology.xml"/> <xi:include href="configure_algos.xml"/> </part> diff --git a/lib/ssh/doc/src/using_ssh.xml b/lib/ssh/doc/src/using_ssh.xml index 80662e9a70..4455d5ecc5 100644 --- a/lib/ssh/doc/src/using_ssh.xml +++ b/lib/ssh/doc/src/using_ssh.xml @@ -74,16 +74,17 @@ <marker id="Running an Erlang ssh Daemon"></marker> <title>Running an Erlang ssh Daemon</title> - <p>The <c>system_dir</c> option must be a directory containing a host - key file and it defaults to <c>/etc/ssh</c>. For details, see Section - Configuration Files in <seealso - marker="SSH_app">ssh(6)</seealso>. + <p>The + <seealso marker="ssh_file#type-system_dir_daemon_option"><c>system_dir</c></seealso> + option must be a directory containing a host key file and it defaults to <c>/etc/ssh</c>. + For details, see Section Configuration Files in <seealso marker="SSH_app">ssh(6)</seealso>. </p> <note><p>Normally, the <c>/etc/ssh</c> directory is only readable by root.</p> </note> - <p>The option <c>user_dir</c> defaults to directory <c>users ~/.ssh</c>.</p> + <p>The option <seealso marker="ssh_file#type-user_dir_common_option"><c>user_dir</c></seealso> + defaults to directory <c>users ~/.ssh</c>.</p> <p><em>Step 1.</em> To run the example without root privileges, generate new keys and host keys:</p> |