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-rw-r--r--lib/ssh/doc/src/ssh.xml21
-rw-r--r--lib/ssh/src/ssh.erl4
-rw-r--r--lib/ssh/src/ssh_acceptor.erl47
-rw-r--r--lib/ssh/test/ssh_basic_SUITE.erl56
4 files changed, 111 insertions, 17 deletions
diff --git a/lib/ssh/doc/src/ssh.xml b/lib/ssh/doc/src/ssh.xml
index 7fbd70c87e..57aab09cc6 100644
--- a/lib/ssh/doc/src/ssh.xml
+++ b/lib/ssh/doc/src/ssh.xml
@@ -307,18 +307,31 @@
<tag><c><![CDATA[{negotiation_timeout, integer()}]]></c></tag>
<item>
- <p>Max time in milliseconds for the authentication negotiation. The default value is 2 minutes.
+ <p>Max time in milliseconds for the authentication negotiation. The default value is 2 minutes. If the client fails to login within this time, the connection is closed.
+ </p>
+ </item>
+
+ <tag><c><![CDATA[{max_sessions, pos_integer()}]]></c></tag>
+ <item>
+ <p>The maximum number of simultaneous sessions that are accepted at any time for this daemon. This includes sessions that are being authorized. So if set to <c>N</c>, and <c>N</c> clients have connected but not started the login process, the <c>N+1</c> connection attempt will be aborted. If <c>N</c> connections are authenticated and still logged in, no more loggins will be accepted until one of the existing ones log out.
+ </p>
+ <p>The counter is per listening port, so if two daemons are started, one with <c>{max_sessions,N}</c> and the other with <c>{max_sessions,M}</c> there will be in total <c>N+M</c> connections accepted for the whole ssh server.
+ </p>
+ <p>Note that if <c>parallel_login</c> is <c>false</c>, only one client at a time may be in the authentication phase.
+ </p>
+ <p>As default, the 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 a time. If set to true, an unlimited logins will be allowed simultanously. Note that this affects only the connections with authentication in progress, not the already authenticated connections.
+ <p>If set to false (the default value), only one login is handled a time. If set to true, an unlimited number of login attempts will be allowed simultanously.
+ </p>
+ <p>If the <c>max_sessions</c> option is set to <c>N</c> and <c>parallel_login</c> is set to <c>true</c>, the max number of simultaneous login attempts at any time is limited to <c>N-K</c> where <c>K</c> is the number of authenticated connections present at this daemon.
</p>
<warning>
- <p>Do not enable parallel_logins without protecting the server by other means like a firewall. If set to true, there is no protection against dos attacs.</p>
+ <p>Do not enable <c>parallel_logins</c> without protecting the server by other means, for example the <c>max_sessions</c> option or a firewall configuration. If set to <c>true</c>, there is no protection against DOS attacks.</p>
</warning>
-
</item>
<tag><c><![CDATA[{key_cb, atom()}]]></c></tag>
diff --git a/lib/ssh/src/ssh.erl b/lib/ssh/src/ssh.erl
index de6e8cc421..75081b7a61 100644
--- a/lib/ssh/src/ssh.erl
+++ b/lib/ssh/src/ssh.erl
@@ -332,6 +332,8 @@ handle_option([{idle_time, _} = Opt | Rest], SocketOptions, SshOptions) ->
handle_option(Rest, SocketOptions, [handle_ssh_option(Opt) | SshOptions]);
handle_option([{rekey_limit, _} = Opt|Rest], SocketOptions, SshOptions) ->
handle_option(Rest, SocketOptions, [handle_ssh_option(Opt) | SshOptions]);
+handle_option([{max_sessions, _} = Opt|Rest], SocketOptions, SshOptions) ->
+ handle_option(Rest, SocketOptions, [handle_ssh_option(Opt) | SshOptions]);
handle_option([{negotiation_timeout, _} = Opt|Rest], SocketOptions, SshOptions) ->
handle_option(Rest, SocketOptions, [handle_ssh_option(Opt) | SshOptions]);
handle_option([{parallel_login, _} = Opt|Rest], SocketOptions, SshOptions) ->
@@ -366,6 +368,8 @@ handle_ssh_option({pref_public_key_algs, Value} = Opt) when is_list(Value), leng
end;
handle_ssh_option({connect_timeout, Value} = Opt) when is_integer(Value); Value == infinity ->
Opt;
+handle_ssh_option({max_sessions, Value} = Opt) when is_integer(Value), Value>0 ->
+ Opt;
handle_ssh_option({negotiation_timeout, Value} = Opt) when is_integer(Value); Value == infinity ->
Opt;
handle_ssh_option({parallel_login, Value} = Opt) when Value==true ; Value==false ->
diff --git a/lib/ssh/src/ssh_acceptor.erl b/lib/ssh/src/ssh_acceptor.erl
index e57b07cee8..7302196674 100644
--- a/lib/ssh/src/ssh_acceptor.erl
+++ b/lib/ssh/src/ssh_acceptor.erl
@@ -80,18 +80,36 @@ acceptor_loop(Callback, Port, Address, Opts, ListenSocket, AcceptTimeout) ->
ListenSocket, AcceptTimeout)
end.
-handle_connection(_Callback, Address, Port, Options, Socket) ->
+handle_connection(Callback, Address, Port, Options, Socket) ->
SystemSup = ssh_system_sup:system_supervisor(Address, Port),
- {ok, SubSysSup} = ssh_system_sup:start_subsystem(SystemSup, Options),
- ConnectionSup = ssh_subsystem_sup:connection_supervisor(SubSysSup),
- Timeout = proplists:get_value(negotiation_timeout,
- proplists:get_value(ssh_opts, Options, []),
- 2*60*1000),
- ssh_connection_handler:start_connection(server, Socket,
- [{supervisors, [{system_sup, SystemSup},
- {subsystem_sup, SubSysSup},
- {connection_sup, ConnectionSup}]}
- | Options], Timeout).
+ SSHopts = proplists:get_value(ssh_opts, Options, []),
+ MaxSessions = proplists:get_value(max_sessions,SSHopts,infinity),
+ case number_of_connections(SystemSup) < MaxSessions of
+ true ->
+ {ok, SubSysSup} = ssh_system_sup:start_subsystem(SystemSup, Options),
+ ConnectionSup = ssh_subsystem_sup:connection_supervisor(SubSysSup),
+ Timeout = proplists:get_value(negotiation_timeout, SSHopts, 2*60*1000),
+ ssh_connection_handler:start_connection(server, Socket,
+ [{supervisors, [{system_sup, SystemSup},
+ {subsystem_sup, SubSysSup},
+ {connection_sup, ConnectionSup}]}
+ | Options], Timeout);
+ false ->
+ Callback:close(Socket),
+ IPstr = if is_tuple(Address) -> inet:ntoa(Address);
+ true -> Address
+ end,
+ Str = try io_lib:format('~s:~p',[IPstr,Port])
+ catch _:_ -> "port "++integer_to_list(Port)
+ end,
+ error_logger:info_report("Ssh login attempt to "++Str++" denied due to option "
+ "max_sessions limits to "++ io_lib:write(MaxSessions) ++
+ " sessions."
+ ),
+ {error,max_sessions}
+ end.
+
+
handle_error(timeout) ->
ok;
@@ -117,3 +135,10 @@ handle_error(Reason) ->
String = lists:flatten(io_lib:format("Accept error: ~p", [Reason])),
error_logger:error_report(String),
exit({accept_failed, String}).
+
+
+number_of_connections(SystemSup) ->
+ length([X ||
+ {R,X,supervisor,[ssh_subsystem_sup]} <- supervisor:which_children(SystemSup),
+ is_reference(R)
+ ]).
diff --git a/lib/ssh/test/ssh_basic_SUITE.erl b/lib/ssh/test/ssh_basic_SUITE.erl
index d2e52379fa..a8b64b1425 100644
--- a/lib/ssh/test/ssh_basic_SUITE.erl
+++ b/lib/ssh/test/ssh_basic_SUITE.erl
@@ -47,21 +47,26 @@ all() ->
daemon_already_started,
server_password_option,
server_userpassword_option,
- double_close].
+ double_close,
+ {group, hardening_tests}
+ ].
groups() ->
[{dsa_key, [], basic_tests()},
{rsa_key, [], basic_tests()},
{dsa_pass_key, [], [pass_phrase]},
{rsa_pass_key, [], [pass_phrase]},
- {internal_error, [], [internal_error]}
+ {internal_error, [], [internal_error]},
+ {hardening_tests, [], [max_sessions]}
].
+
basic_tests() ->
[send, close, peername_sockname,
exec, exec_compressed, shell, cli, known_hosts,
idle_time, rekey, openssh_zlib_basic_test].
+
%%--------------------------------------------------------------------
init_per_suite(Config) ->
case catch crypto:start() of
@@ -74,6 +79,8 @@ end_per_suite(_Config) ->
ssh:stop(),
crypto:stop().
%%--------------------------------------------------------------------
+init_per_group(hardening_tests, Config) ->
+ init_per_group(dsa_key, Config);
init_per_group(dsa_key, Config) ->
DataDir = ?config(data_dir, Config),
PrivDir = ?config(priv_dir, Config),
@@ -103,6 +110,8 @@ init_per_group(internal_error, Config) ->
init_per_group(_, Config) ->
Config.
+end_per_group(hardening_tests, Config) ->
+ end_per_group(dsa_key, Config);
end_per_group(dsa_key, Config) ->
PrivDir = ?config(priv_dir, Config),
ssh_test_lib:clean_dsa(PrivDir),
@@ -639,6 +648,49 @@ openssh_zlib_basic_test(Config) ->
ssh:stop_daemon(Pid).
%%--------------------------------------------------------------------
+
+max_sessions(Config) ->
+ SystemDir = filename:join(?config(priv_dir, Config), system),
+ UserDir = ?config(priv_dir, Config),
+ MaxSessions = 2,
+ {Pid, Host, Port} = ssh_test_lib:daemon([{system_dir, SystemDir},
+ {user_dir, UserDir},
+ {user_passwords, [{"carni", "meat"}]},
+ {parallel_login, true},
+ {max_sessions, MaxSessions}
+ ]),
+
+ Connect = fun() ->
+ R=ssh_test_lib:connect(Host, Port, [{silently_accept_hosts, true},
+ {user_dir, UserDir},
+ {user_interaction, false},
+ {user, "carni"},
+ {password, "meat"}
+ ]),
+ ct:log("Connection ~p up",[R])
+ end,
+
+ try [Connect() || _ <- lists:seq(1,MaxSessions)]
+ of
+ _ ->
+ ct:pal("Expect Info Report:",[]),
+ try Connect()
+ of
+ _ConnectionRef ->
+ ssh:stop_daemon(Pid),
+ {fail,"Too many connections accepted"}
+ catch
+ error:{badmatch,{error,"Connection closed"}} ->
+ ssh:stop_daemon(Pid),
+ ok
+ end
+ catch
+ error:{badmatch,{error,"Connection closed"}} ->
+ ssh:stop_daemon(Pid),
+ {fail,"Too few connections accepted"}
+ end.
+
+%%--------------------------------------------------------------------
%% Internal functions ------------------------------------------------
%%--------------------------------------------------------------------
generated by cgit v1.2.3 (git 2.25.1) at 2024-12-01 21:16:53 +0000