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Diffstat (limited to 'lib/ssh/doc/src/ssh.xml')
| -rw-r--r-- | lib/ssh/doc/src/ssh.xml | 193 |
1 files changed, 141 insertions, 52 deletions
diff --git a/lib/ssh/doc/src/ssh.xml b/lib/ssh/doc/src/ssh.xml index cf5e8f1aff..b3f850fc38 100644 --- a/lib/ssh/doc/src/ssh.xml +++ b/lib/ssh/doc/src/ssh.xml @@ -32,28 +32,33 @@ <modulesummary>Main API of the ssh application</modulesummary> <description> <p>Interface module for the <c>ssh</c> application.</p> + <p>See <seealso marker="ssh:SSH_app#supported">ssh(6)</seealso> for details of supported version, + algorithms and unicode support.</p> </description> - <section> - <title>SSH</title> - <marker id="supported"/> - <list type="bulleted"> - <item>For application dependencies see <seealso marker="SSH_app"> ssh(6)</seealso> </item> - <item>Supported SSH version is 2.0.</item> - <item>Supported public key algorithms: ssh-rsa and ssh-dss.</item> - <item>Supported MAC algorithms: hmac-sha2-256 and hmac-sha1.</item> - <item>Supported encryption algorithms: aes128-ctr, aes128-cb and 3des-cbc.</item> - <item>Supported key exchange algorithms: diffie-hellman-group1-sha1, diffie-hellman-group14-sha1, diffie-hellman-group-exchange-sha1 and diffie-hellman-group-exchange-sha256.</item> - <item>Supported compression algorithms: none, zlib, [email protected],</item> - <item>Supports unicode filenames if the emulator and the underlaying OS support it. - See section DESCRIPTION in the - <seealso marker="kernel:file">file</seealso> manual page in <c>kernel</c> - for information about this subject.</item> - <item>Supports unicode in shell and CLI.</item> - </list> - + <section> + <title>OPTIONS</title> + <p>The exact behaviour of some functions can be adjusted with the use of options which are documented together + with the functions. Generally could each option be used at most one time in each function call. If given two or more + times, the effect is not predictable unless explicitly documented.</p> + <p>The options are of different kinds:</p> + <taglist> + <tag>Limits</tag> + <item><p>which alters limits in the system, for example number of simultaneous login attempts.</p></item> + + <tag>Timeouts</tag> + <item><p>which give some defined behaviour if too long time elapses before a given event or action, + for example time to wait for an answer.</p></item> + + <tag>Callbacks</tag> + <item><p>which gives the caller of the function the possibility to execute own code on some events, + for example calling an own logging function or to perform an own login function</p></item> + + <tag>Behaviour</tag> + <item><p>which changes the systems behaviour.</p></item> + </taglist> </section> - + <section> <title>DATA TYPES</title> <p>Type definitions that are used more than once in @@ -80,6 +85,15 @@ <item><p><c>atom()</c> - Name of the Erlang module implementing the subsystem using the <c>ssh_channel</c> behavior, see <seealso marker="ssh_channel">ssh_channel(3)</seealso></p></item> + <tag><c>key_cb() =</c></tag> + <item> + <p><c>atom() | {atom(), list()}</c></p> + <p><c>atom()</c> - Name of the erlang module implementing the behaviours + <seealso marker="ssh_client_key_api">ssh_client_key_api</seealso> or + <seealso marker="ssh_client_key_api">ssh_client_key_api</seealso> as the + case maybe.</p> + <p><c>list()</c> - List of options that can be passed to the callback module.</p> + </item> <tag><c>channel_init_args() =</c></tag> <item><p><c>list()</c></p></item> @@ -192,26 +206,25 @@ <tag><c><![CDATA[{public_key_alg, 'ssh-rsa' | 'ssh-dss'}]]></c></tag> <item> <note> - <p>This option is kept for compatibility. It is ignored if the <c>preferred_algorithms</c> - option is used. The equivalence of <c>{public_key_alg,'ssh-dss'}</c> is - <c>{preferred_algorithms, [{public_key,['ssh-dss','ssh-rsa']}]}</c>.</p> + <p>This option will be removed in OTP 20, but is kept for compatibility. It is ignored if + the preferred <c>pref_public_key_algs</c> option is used.</p> </note> <p>Sets the preferred public key algorithm to use for user authentication. If the preferred algorithm fails, - the other algorithm is tried. The default is - to try <c><![CDATA['ssh-rsa']]></c> first.</p> + the other algorithm is tried. If <c>{public_key_alg, 'ssh-rsa'}</c> is set, it is translated + to <c>{pref_public_key_algs, ['ssh-rsa','ssh-dss']}</c>. If it is + <c>{public_key_alg, 'ssh-dss'}</c>, it is translated + to <c>{pref_public_key_algs, ['ssh-dss','ssh-rsa']}</c>. + </p> </item> <tag><c><![CDATA[{pref_public_key_algs, list()}]]></c></tag> <item> - <note> - <p>This option is kept for compatibility. It is ignored if the <c>preferred_algorithms</c> - option is used. The equivalence of <c>{pref_public_key_algs,['ssh-dss']}</c> is - <c>{preferred_algorithms, [{public_key,['ssh-dss']}]}</c>.</p> - </note> - <p>List of public key algorithms to try to use. - <c>'ssh-rsa'</c> and <c>'ssh-dss'</c> are available. - Overrides <c><![CDATA[{public_key_alg, 'ssh-rsa' | 'ssh-dss'}]]></c></p> + <p>List of user (client) public key algorithms to try to use.</p> + <p>The default value is + <c><![CDATA[['ssh-rsa','ssh-dss','ecdsa-sha2-nistp256','ecdsa-sha2-nistp384','ecdsa-sha2-nistp521'] ]]></c> + </p> + <p>If there is no public key of a specified type available, the corresponding entry is ignored.</p> </item> <tag><c><![CDATA[{preferred_algorithms, algs_list()}]]></c></tag> @@ -219,6 +232,7 @@ <p>List of algorithms to use in the algorithm negotiation. The default <c>algs_list()</c> can be obtained from <seealso marker="#default_algorithms/0">default_algorithms/0</seealso>. </p> + <p>If an alg_entry() is missing in the algs_list(), the default value is used for that entry.</p> <p>Here is an example of this option:</p> <code> {preferred_algorithms, @@ -229,9 +243,9 @@ {compression,[none,zlib]} } </code> - <p>The example specifies different algorithms in the two directions (client2server and server2client), for cipher but specifies the same -algorithms for mac and compression in both directions. The kex (key exchange) and public key algorithms are set to their default values, -kex is implicit but public_key is set explicitly.</p> + <p>The example specifies different algorithms in the two directions (client2server and server2client), + for cipher but specifies the same algorithms for mac and compression in both directions. + The kex (key exchange) is implicit but public_key is set explicitly.</p> <warning> <p>Changing the values can make a connection less secure. Do not change unless you @@ -243,7 +257,7 @@ kex is implicit but public_key is set explicitly.</p> <tag><c><![CDATA[{dh_gex_limits,{Min=integer(),I=integer(),Max=integer()}}]]></c></tag> <item> <p>Sets the three diffie-hellman-group-exchange parameters that guides the connected server in choosing a group. - See RFC 4419 for the function of thoose. The default value is <c>{512, 1024, 4096}</c>. + See RFC 4419 for the function of thoose. The default value is <c>{1024, 6144, 8192}</c>. </p> </item> @@ -267,11 +281,13 @@ kex is implicit but public_key is set explicitly.</p> password, if the password authentication method is attempted.</p> </item> - <tag><c><![CDATA[{key_cb, atom()}]]></c></tag> + <tag><c><![CDATA[{key_cb, key_cb()}]]></c></tag> <item> - <p>Module implementing the behaviour - <seealso marker="ssh_client_key_api">ssh_client_key_api</seealso>. - Can be used to customize the handling of public keys. + <p>Module implementing the behaviour <seealso + marker="ssh_client_key_api">ssh_client_key_api</seealso>. Can be used to + customize the handling of public keys. If callback options are provided + along with the module name, they are made available to the callback + module via the options passed to it under the key 'key_cb_private'. </p> </item> <tag><c><![CDATA[{quiet_mode, atom() = boolean()}]]></c></tag> @@ -435,6 +451,7 @@ kex is implicit but public_key is set explicitly.</p> <p>List of algorithms to use in the algorithm negotiation. The default <c>algs_list()</c> can be obtained from <seealso marker="#default_algorithms/0">default_algorithms/0</seealso>. </p> + <p>If an alg_entry() is missing in the algs_list(), the default value is used for that entry.</p> <p>Here is an example of this option:</p> <code> {preferred_algorithms, @@ -445,9 +462,9 @@ kex is implicit but public_key is set explicitly.</p> {compression,[none,zlib]} } </code> - <p>The example specifies different algorithms in the two directions (client2server and server2client), for cipher but specifies the same -algorithms for mac and compression in both directions. The kex (key exchange) and public key algorithms are set to their default values, -kex is implicit but public_key is set explicitly.</p> + <p>The example specifies different algorithms in the two directions (client2server and server2client), + for cipher but specifies the same algorithms for mac and compression in both directions. + The kex (key exchange) is implicit but public_key is set explicitly.</p> <warning> <p>Changing the values can make a connection less secure. Do not change unless you @@ -456,21 +473,82 @@ kex is implicit but public_key is set explicitly.</p> </warning> </item> - <tag><c><![CDATA[{dh_gex_groups, [{Size=integer(),G=integer(),P=integer()}] | {file,filename()} }]]></c></tag> + <tag><c><![CDATA[{dh_gex_groups, [{Size=integer(),G=integer(),P=integer()}] | {file,filename()} {ssh_moduli_file,filename()} }]]></c></tag> + <item> + <p>Defines the groups the server may choose among when diffie-hellman-group-exchange is negotiated. + See RFC 4419 for details. The three variants of this option are: + </p> + <taglist> + <tag><c>{Size=integer(),G=integer(),P=integer()}</c></tag> + <item>The groups are given explicitly in this list. There may be several elements with the same <c>Size</c>. + In such a case, the server will choose one randomly in the negotiated Size. + </item> + <tag><c>{file,filename()}</c></tag> + <item>The file must have one or more three-tuples <c>{Size=integer(),G=integer(),P=integer()}</c> + terminated by a dot. The file is read when the daemon starts. + </item> + <tag><c>{ssh_moduli_file,filename()}</c></tag> + <item>The file must be in + <seealso marker="public_key:public_key#dh_gex_group/4">ssh-keygen moduli file format</seealso>. + The file is read when the daemon starts. + </item> + </taglist> + <p>The default list is fetched from the + <seealso marker="public_key:public_key#dh_gex_group/4">public_key</seealso> application. + </p> + </item> + + <tag><c><![CDATA[{dh_gex_limits,{Min=integer(),Max=integer()}}]]></c></tag> <item> - <p>Sets the groups that the server may choose among when diffie-hellman-group-exchange is negotiated. - See RFC 4419 for details. + <p>Limits what a client can ask for in diffie-hellman-group-exchange. + The limits will be + <c>{MaxUsed = min(MaxClient,Max), MinUsed = max(MinClient,Min)}</c> where <c>MaxClient</c> and + <c>MinClient</c> are the values proposed by a connecting client. </p> - <p>If the parameter is <c>{file,filename()}</c>, the file must exist and have one or more three-tuples terminated by a dot. The interpretation is as if the tuples had been given directly in the option. The file is read when the daemon starts. + <p>The default value is <c>{0,infinity}</c>. </p> + <p>If <c>MaxUsed < MinUsed</c> in a key exchange, it will fail with a disconnect. + </p> + <p>See RFC 4419 for the function of the Max and Min values.</p> </item> - <tag><c><![CDATA[{pwdfun, fun(User::string(), password::string()) -> boolean()}]]></c></tag> + <tag><c><![CDATA[{pwdfun, fun(User::string(), Password::string(), PeerAddress::{ip_adress(),port_number()}, State::any()) -> boolean() | disconnect | {boolean(),any()} }]]></c></tag> + <item> + <p>Provides a function for password validation. This could used for calling an external system or if + passwords should be stored as a hash. The fun returns: + <list type="bulleted"> + <item><c>true</c> if the user and password is valid and</item> + <item><c>false</c> otherwise.</item> + </list> + </p> + <p>This fun can also be used to make delays in authentication tries for example by calling + <seealso marker="stdlib:timer#sleep/1">timer:sleep/1</seealso>. To facilitate counting of failed tries + the <c>State</c> variable could be used. This state is per connection only. The first time the pwdfun + is called for a connection, the <c>State</c> variable has the value <c>undefined</c>. + The pwdfun can return - in addition to the values above - a new state + as: + <list type="bulleted"> + <item><c>{true, NewState:any()}</c> if the user and password is valid or</item> + <item><c>{false, NewState:any()}</c> if the user or password is invalid</item> + </list> + </p> + <p>A third usage is to block login attempts from a missbehaving peer. The <c>State</c> described above + can be used for this. In addition to the responses above, the following return value is introduced: + <list type="bulleted"> + <item><c>disconnect</c> if the connection should be closed immediately after sending a SSH_MSG_DISCONNECT + message.</item> + </list> + </p> + </item> + + <tag><c><![CDATA[{pwdfun, fun(User::string(), Password::string()) -> boolean()}]]></c></tag> <item> <p>Provides a function for password validation. This function is called with user and password as strings, and returns <c><![CDATA[true]]></c> if the password is valid and <c><![CDATA[false]]></c> otherwise.</p> + <p>This option (<c>{pwdfun,fun/2}</c>) is the same as a subset of the previous + (<c>{pwdfun,fun/4}</c>). It is kept for compatibility.</p> </item> <tag><c><![CDATA[{negotiation_timeout, integer()}]]></c></tag> @@ -501,6 +579,15 @@ kex is implicit but public_key is set explicitly.</p> </p> </item> + <tag><c><![CDATA[{max_channels, pos_integer()}]]></c></tag> + <item> + <p>The maximum number of channels with active remote subsystem that are accepted for + each connection to this daemon</p> + <p>By default, this option is not set. This means that the number is not limited. + </p> + </item> + + <tag><c><![CDATA[{parallel_login, boolean()}]]></c></tag> <item> <p>If set to false (the default value), only one login is handled at a time. @@ -532,11 +619,13 @@ kex is implicit but public_key is set explicitly.</p> </p> </item> - <tag><c><![CDATA[{key_cb, atom()}]]></c></tag> + <tag><c><![CDATA[{key_cb, key_cb()}]]></c></tag> <item> - <p>Module implementing the behaviour - <seealso marker="ssh_server_key_api">ssh_server_key_api</seealso>. - Can be used to customize the handling of public keys. + <p>Module implementing the behaviour <seealso + marker="ssh_server_key_api">ssh_server_key_api</seealso>. Can be used to + customize the handling of public keys. If callback options are provided + along with the module name, they are made available to the callback + module via the options passed to it under the key 'key_cb_private'. </p> </item> |