| From 6eef04130afc8b0ccb63c9a0d8650209cf54892f Mon Sep 17 00:00:00 2001 |
| From: Jakub Witczak <kuba@erlang.org> |
| Date: Mon, 14 Apr 2025 16:33:21 +0200 |
| Subject: [PATCH] ssh: early RCE fix |
|
|
| - disconnect when connection protocol message arrives |
| - when user is not authenticated for connection |
| - see RFC4252 sec.6 |
| |
| lib/ssh/src/ssh_connection.erl | 28 ++++++++-- |
| lib/ssh/test/ssh_protocol_SUITE.erl | 86 +++++++++++++++-------------- |
| 2 files changed, 67 insertions(+), 47 deletions(-) |
|
|
| |
| |
| |
| |
| @@ -53,6 +53,8 @@ these messages are handled by |
| {type,<<"Signals">>}, |
| {type,<<"Exit Status">>}]}). |
| |
| +-include_lib("kernel/include/logger.hrl"). |
| + |
| -include("ssh.hrl"). |
| -include("ssh_connect.hrl"). |
| -include("ssh_transport.hrl"). |
| @@ -756,6 +758,25 @@ channel_data(ChannelId, DataType, Data0, |
| %%% |
| |
| -doc false. |
| +handle_msg(#ssh_msg_disconnect{code = Code, description = Description}, Connection, _, _SSH) -> |
| + {disconnect, {Code, Description}, handle_stop(Connection)}; |
| + |
| +handle_msg(Msg, Connection, server, Ssh = #ssh{authenticated = false}) -> |
| + %% See RFC4252 6. |
| + %% Message numbers of 80 and higher are reserved for protocols running |
| + %% after this authentication protocol, so receiving one of them before |
| + %% authentication is complete is an error, to which the server MUST |
| + %% respond by disconnecting, preferably with a proper disconnect message |
| + %% sent to ease troubleshooting. |
| + MsgFun = fun(M) -> |
| + MaxLogItemLen = ?GET_OPT(max_log_item_len, Ssh#ssh.opts), |
| + io_lib:format("Connection terminated. Unexpected message for unauthenticated user." |
| + " Message: ~w", [M], |
| + [{chars_limit, MaxLogItemLen}]) |
| + end, |
| + ?LOG_DEBUG(MsgFun, [Msg]), |
| + {disconnect, {?SSH_DISCONNECT_PROTOCOL_ERROR, "Connection refused"}, handle_stop(Connection)}; |
| + |
| handle_msg(#ssh_msg_channel_open_confirmation{recipient_channel = ChannelId, |
| sender_channel = RemoteId, |
| initial_window_size = WindowSz, |
| @@ -1260,12 +1281,7 @@ handle_msg(#ssh_msg_request_success{data = Data}, |
| #connection{requests = [{_, From, Fun} | Rest]} = Connection0, _, _SSH) -> |
| Connection = Fun({success,Data}, Connection0), |
| {[{channel_request_reply, From, {success, Data}}], |
| - Connection#connection{requests = Rest}}; |
| - |
| -handle_msg(#ssh_msg_disconnect{code = Code, |
| - description = Description}, |
| - Connection, _, _SSH) -> |
| - {disconnect, {Code, Description}, handle_stop(Connection)}. |
| + Connection#connection{requests = Rest}}. |
| |
| |
| %%%---------------------------------------------------------------- |
| |
| |
| |
| |
| @@ -75,6 +75,7 @@ |
| no_common_alg_client_disconnects/1, |
| no_common_alg_server_disconnects/1, |
| custom_kexinit/1, |
| + early_rce/1, |
| no_ext_info_s1/1, |
| no_ext_info_s2/1, |
| packet_length_too_large/1, |
| @@ -113,6 +114,7 @@ suite() -> |
| all() -> |
| [{group,tool_tests}, |
| client_info_line, |
| + early_rce, |
| {group,kex}, |
| {group,service_requests}, |
| {group,authentication}, |
| @@ -131,10 +133,8 @@ groups() -> |
| ]}, |
| {packet_size_error, [], [packet_length_too_large, |
| packet_length_too_short]}, |
| - |
| {field_size_error, [], [service_name_length_too_large, |
| service_name_length_too_short]}, |
| - |
| {kex, [], [custom_kexinit, |
| no_common_alg_server_disconnects, |
| no_common_alg_client_disconnects, |
| @@ -178,7 +178,8 @@ init_per_suite(Config) -> |
| end_per_suite(Config) -> |
| stop_apps(Config). |
| |
| -init_per_testcase(Tc, Config) when Tc == no_common_alg_server_disconnects; Tc == custom_kexinit -> |
| +init_per_testcase(Tc, Config) when Tc == no_common_alg_server_disconnects; |
| + Tc == custom_kexinit -> |
| start_std_daemon(Config, [{preferred_algorithms,[{public_key,['ssh-rsa']}, |
| {cipher,?DEFAULT_CIPHERS} |
| ]}]); |
| @@ -224,7 +225,8 @@ init_per_testcase(TC, Config) when TC == gex_client_init_option_groups ; |
| init_per_testcase(_TestCase, Config) -> |
| check_std_daemon_works(Config, ?LINE). |
| |
| -end_per_testcase(Tc, Config) when Tc == no_common_alg_server_disconnects; Tc == custom_kexinit -> |
| +end_per_testcase(Tc, Config) when Tc == no_common_alg_server_disconnects; |
| + Tc == custom_kexinit -> |
| stop_std_daemon(Config); |
| end_per_testcase(kex_strict_negotiated, Config) -> |
| Config; |
| @@ -385,6 +387,44 @@ no_common_alg_server_disconnects(Config) -> |
| ] |
| ). |
| |
| +early_rce(Config) -> |
| + {ok,InitialState} = |
| + ssh_trpt_test_lib:exec([{set_options, [print_ops, print_seqnums, print_messages]}]), |
| + TypeOpen = "session", |
| + ChannelId = 0, |
| + WinSz = 425984, |
| + PktSz = 65536, |
| + DataOpen = <<>>, |
| + SshMsgChannelOpen = ssh_connection:channel_open_msg(TypeOpen, ChannelId, WinSz, PktSz, DataOpen), |
| + |
| + Id = 0, |
| + TypeReq = "exec", |
| + WantReply = true, |
| + DataReq = <<?STRING(<<"lists:seq(1,10).">>)>>, |
| + SshMsgChannelRequest = |
| + ssh_connection:channel_request_msg(Id, TypeReq, WantReply, DataReq), |
| + {ok,AfterKexState} = |
| + ssh_trpt_test_lib:exec( |
| + [{connect, |
| + server_host(Config),server_port(Config), |
| + [{preferred_algorithms,[{kex,[?DEFAULT_KEX]}, |
| + {cipher,?DEFAULT_CIPHERS} |
| + ]}, |
| + {silently_accept_hosts, true}, |
| + {recv_ext_info, false}, |
| + {user_dir, user_dir(Config)}, |
| + {user_interaction, false} |
| + | proplists:get_value(extra_options,Config,[])]}, |
| + receive_hello, |
| + {send, hello}, |
| + {send, ssh_msg_kexinit}, |
| + {match, #ssh_msg_kexinit{_='_'}, receive_msg}, |
| + {send, SshMsgChannelOpen}, |
| + {send, SshMsgChannelRequest}, |
| + {match, disconnect(), receive_msg} |
| + ], InitialState), |
| + ok. |
| + |
| custom_kexinit(Config) -> |
| %% 16#C0 value causes unicode:characters_to_list to return a big error value |
| Trash = lists:duplicate(260_000, 16#C0), |
| @@ -411,11 +451,6 @@ custom_kexinit(Config) -> |
| first_kex_packet_follows = false, |
| reserved = 0 |
| }, |
| - PacketFun = |
| - fun(Msg, Ssh) -> |
| - BinMsg = custom_encode(Msg), |
| - ssh_transport:pack(BinMsg, Ssh, 0) |
| - end, |
| {ok,_} = |
| ssh_trpt_test_lib:exec( |
| [{set_options, [print_ops, {print_messages,detail}]}, |
| @@ -431,42 +466,11 @@ custom_kexinit(Config) -> |
| receive_hello, |
| {send, hello}, |
| {match, #ssh_msg_kexinit{_='_'}, receive_msg}, |
| - {send, {special, KexInit, PacketFun}}, % with server unsupported 'ssh-dss' ! |
| + {send, KexInit}, % with server unsupported 'ssh-dss' ! |
| {match, disconnect(), receive_msg} |
| ] |
| ). |
| |
| -custom_encode(#ssh_msg_kexinit{ |
| - cookie = Cookie, |
| - kex_algorithms = KeyAlgs, |
| - server_host_key_algorithms = HostKeyAlgs, |
| - encryption_algorithms_client_to_server = EncAlgC2S, |
| - encryption_algorithms_server_to_client = EncAlgS2C, |
| - mac_algorithms_client_to_server = MacAlgC2S, |
| - mac_algorithms_server_to_client = MacAlgS2C, |
| - compression_algorithms_client_to_server = CompAlgS2C, |
| - compression_algorithms_server_to_client = CompAlgC2S, |
| - languages_client_to_server = LangC2S, |
| - languages_server_to_client = LangS2C, |
| - first_kex_packet_follows = Bool, |
| - reserved = Reserved |
| - }) -> |
| - KeyAlgsBin0 = <<?Ename_list(KeyAlgs)>>, |
| - <<?UINT32(Len0), Data:Len0/binary>> = KeyAlgsBin0, |
| - KeyAlgsBin = <<?UINT32(Len0), Data/binary>>, |
| - <<?Ebyte(?SSH_MSG_KEXINIT), Cookie/binary, |
| - KeyAlgsBin/binary, |
| - ?Ename_list(HostKeyAlgs), |
| - ?Ename_list(EncAlgC2S), |
| - ?Ename_list(EncAlgS2C), |
| - ?Ename_list(MacAlgC2S), |
| - ?Ename_list(MacAlgS2C), |
| - ?Ename_list(CompAlgS2C), |
| - ?Ename_list(CompAlgC2S), |
| - ?Ename_list(LangC2S), |
| - ?Ename_list(LangS2C), |
| - ?Eboolean(Bool), ?Euint32(Reserved)>>. |
| - |
| %%-------------------------------------------------------------------- |
| %%% Algo negotiation fail. This should result in a ssh_msg_disconnect |
| %%% being sent from the client. |
|
|
