%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2008-2016. All Rights Reserved.
%%
%% 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.
%%
%% %CopyrightEnd%
%%
%%
-module(ssh_auth).
-include_lib("public_key/include/public_key.hrl").
-include("ssh.hrl").
-include("ssh_auth.hrl").
-include("ssh_transport.hrl").
-export([publickey_msg/1, password_msg/1, keyboard_interactive_msg/1,
service_request_msg/1, init_userauth_request_msg/1,
userauth_request_msg/1, handle_userauth_request/3,
handle_userauth_info_request/2, handle_userauth_info_response/2
]).
%%--------------------------------------------------------------------
%%% Internal application API
%%--------------------------------------------------------------------
%%%----------------------------------------------------------------
userauth_request_msg(#ssh{userauth_methods = ServerMethods,
userauth_supported_methods = UserPrefMethods, % Note: this is not documented as supported for clients
userauth_preference = ClientMethods0
} = Ssh0) ->
case sort_select_mthds(ClientMethods0, UserPrefMethods, ServerMethods) of
[] ->
Msg = #ssh_msg_disconnect{code = ?SSH_DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE,
description = "Unable to connect using the available authentication methods",
language = "en"},
{disconnect, Msg, ssh_transport:ssh_packet(Msg, Ssh0)};
[{Pref,Module,Function,Args} | Prefs] ->
Ssh = case Pref of
"keyboard-interactive" -> Ssh0;
_ -> Ssh0#ssh{userauth_preference = Prefs}
end,
case Module:Function(Args ++ [Ssh]) of
{not_ok, Ssh1} ->
userauth_request_msg(Ssh1#ssh{userauth_preference = Prefs});
Result ->
{Pref,Result}
end
end.
sort_select_mthds(Clients, undefined, Servers) ->
%% User has not expressed an opinion via option "auth_methods", use the server's prefs
sort_select_mthds1(Clients, Servers, string:tokens(?SUPPORTED_AUTH_METHODS,","));
sort_select_mthds(Clients, Users0, Servers0) ->
%% The User has an opinion, use the intersection of that and the Servers whishes but
%% in the Users order
sort_select_mthds1(Clients, string:tokens(Users0,","), Servers0).
sort_select_mthds1(Clients, Users0, Servers0) ->
Servers = unique(Servers0),
Users = unique(Users0),
[C || Key <- Users,
lists:member(Key, Servers),
C <- Clients,
element(1,C) == Key].
unique(L) ->
lists:reverse(
lists:foldl(fun(E,Acc) ->
case lists:member(E,Acc) of
true -> Acc;
false -> [E|Acc]
end
end, [], L)).
%%%---- userauth_request_msg "callbacks"
password_msg([#ssh{opts = Opts, io_cb = IoCb,
user = User, service = Service} = Ssh0]) ->
{Password,Ssh} =
case proplists:get_value(password, Opts) of
undefined when IoCb == ssh_no_io ->
{not_ok, Ssh0};
undefined ->
{IoCb:read_password("ssh password: ",Ssh0), Ssh0};
PW ->
%% If "password" option is given it should not be tried again
{PW, Ssh0#ssh{opts = lists:keyreplace(password,1,Opts,{password,not_ok})}}
end,
case Password of
not_ok ->
{not_ok, Ssh};
_ ->
ssh_transport:ssh_packet(
#ssh_msg_userauth_request{user = User,
service = Service,
method = "password",
data =
<<?BOOLEAN(?FALSE),
?STRING(unicode:characters_to_binary(Password))>>},
Ssh)
end.
%% See RFC 4256 for info on keyboard-interactive
keyboard_interactive_msg([#ssh{user = User,
opts = Opts,
service = Service} = Ssh]) ->
case proplists:get_value(password, Opts) of
not_ok ->
{not_ok,Ssh}; % No need to use a failed pwd once more
_ ->
ssh_transport:ssh_packet(
#ssh_msg_userauth_request{user = User,
service = Service,
method = "keyboard-interactive",
data = << ?STRING(<<"">>),
?STRING(<<>>) >> },
Ssh)
end.
publickey_msg([Alg, #ssh{user = User,
session_id = SessionId,
service = Service,
opts = Opts} = Ssh]) ->
Hash = sha, %% Maybe option?!
KeyCb = proplists:get_value(key_cb, Opts, ssh_file),
case KeyCb:user_key(Alg, Opts) of
{ok, PrivKey} ->
StrAlgo = atom_to_list(Alg),
case encode_public_key(StrAlgo, ssh_transport:extract_public_key(PrivKey)) of
not_ok ->
{not_ok, Ssh};
PubKeyBlob ->
SigData = build_sig_data(SessionId,
User, Service, PubKeyBlob, StrAlgo),
Sig = ssh_transport:sign(SigData, Hash, PrivKey),
SigBlob = list_to_binary([?string(StrAlgo), ?binary(Sig)]),
ssh_transport:ssh_packet(
#ssh_msg_userauth_request{user = User,
service = Service,
method = "publickey",
data = [?TRUE,
?string(StrAlgo),
?binary(PubKeyBlob),
?binary(SigBlob)]},
Ssh)
end;
_Error ->
{not_ok, Ssh}
end.
%%%----------------------------------------------------------------
service_request_msg(Ssh) ->
ssh_transport:ssh_packet(#ssh_msg_service_request{name = "ssh-userauth"},
Ssh#ssh{service = "ssh-userauth"}).
%%%----------------------------------------------------------------
init_userauth_request_msg(#ssh{opts = Opts} = Ssh) ->
case user_name(Opts) of
{ok, User} ->
Msg = #ssh_msg_userauth_request{user = User,
service = "ssh-connection",
method = "none",
data = <<>>},
Algs0 = proplists:get_value(pref_public_key_algs, Opts, ?SUPPORTED_USER_KEYS),
%% The following line is not strictly correct. The call returns the
%% supported HOST key types while we are interested in USER keys. However,
%% they "happens" to be the same (for now). This could change....
%% There is no danger as long as the set of user keys is a subset of the set
%% of host keys.
CryptoSupported = ssh_transport:supported_algorithms(public_key),
Algs = [A || A <- Algs0,
lists:member(A, CryptoSupported)],
Prefs = method_preference(Algs),
ssh_transport:ssh_packet(Msg, Ssh#ssh{user = User,
userauth_preference = Prefs,
userauth_methods = none,
service = "ssh-connection"});
{error, no_user} ->
ErrStr = "Could not determine the users name",
ssh_connection_handler:disconnect(
#ssh_msg_disconnect{code = ?SSH_DISCONNECT_ILLEGAL_USER_NAME,
description = ErrStr})
end.
%%%----------------------------------------------------------------
%%% called by server
handle_userauth_request(#ssh_msg_service_request{name = Name = "ssh-userauth"},
_, Ssh) ->
{ok, ssh_transport:ssh_packet(#ssh_msg_service_accept{name = Name},
Ssh#ssh{service = "ssh-connection"})};
handle_userauth_request(#ssh_msg_userauth_request{user = User,
service = "ssh-connection",
method = "password",
data = <<?FALSE, ?UINT32(Sz), BinPwd:Sz/binary>>}, _,
#ssh{opts = Opts,
userauth_supported_methods = Methods} = Ssh) ->
Password = unicode:characters_to_list(BinPwd),
case check_password(User, Password, Opts, Ssh) of
{true,Ssh1} ->
{authorized, User,
ssh_transport:ssh_packet(#ssh_msg_userauth_success{}, Ssh1)};
{false,Ssh1} ->
{not_authorized, {User, {error,"Bad user or password"}},
ssh_transport:ssh_packet(#ssh_msg_userauth_failure{
authentications = Methods,
partial_success = false}, Ssh1)}
end;
handle_userauth_request(#ssh_msg_userauth_request{user = User,
service = "ssh-connection",
method = "password",
data = <<?TRUE,
_/binary
%% ?UINT32(Sz1), OldBinPwd:Sz1/binary,
%% ?UINT32(Sz2), NewBinPwd:Sz2/binary
>>
}, _,
#ssh{userauth_supported_methods = Methods} = Ssh) ->
%% Password change without us having sent SSH_MSG_USERAUTH_PASSWD_CHANGEREQ (because we never do)
%% RFC 4252 says:
%% SSH_MSG_USERAUTH_FAILURE without partial success - The password
%% has not been changed. Either password changing was not supported,
%% or the old password was bad.
{not_authorized, {User, {error,"Password change not supported"}},
ssh_transport:ssh_packet(#ssh_msg_userauth_failure{
authentications = Methods,
partial_success = false}, Ssh)};
handle_userauth_request(#ssh_msg_userauth_request{user = User,
service = "ssh-connection",
method = "none"}, _,
#ssh{userauth_supported_methods = Methods} = Ssh) ->
{not_authorized, {User, undefined},
ssh_transport:ssh_packet(
#ssh_msg_userauth_failure{authentications = Methods,
partial_success = false}, Ssh)};
handle_userauth_request(#ssh_msg_userauth_request{user = User,
service = "ssh-connection",
method = "publickey",
data = Data},
SessionId,
#ssh{opts = Opts,
userauth_supported_methods = Methods} = Ssh) ->
<<?BYTE(HaveSig),
?UINT32(ALen), BAlg:ALen/binary,
Rest/binary>> = Data,
{KeyBlob, SigWLen} =
case Rest of
<<?UINT32(KLen0), KeyBlob0:KLen0/binary, SigWLen0/binary>> ->
{KeyBlob0, SigWLen0};
<<>> ->
{<<>>, <<>>}
end,
case HaveSig of
?TRUE ->
case verify_sig(SessionId, User, "ssh-connection",
binary_to_list(BAlg),
KeyBlob, SigWLen, Opts) of
true ->
{authorized, User,
ssh_transport:ssh_packet(
#ssh_msg_userauth_success{}, Ssh)};
false ->
{not_authorized, {User, undefined},
ssh_transport:ssh_packet(#ssh_msg_userauth_failure{
authentications = Methods,
partial_success = false}, Ssh)}
end;
?FALSE ->
{not_authorized, {User, undefined},
ssh_transport:ssh_packet(
#ssh_msg_userauth_pk_ok{algorithm_name = binary_to_list(BAlg),
key_blob = KeyBlob}, Ssh)}
end;
handle_userauth_request(#ssh_msg_userauth_request{user = User,
service = "ssh-connection",
method = "keyboard-interactive",
data = _},
_, #ssh{opts = Opts,
kb_tries_left = KbTriesLeft,
userauth_supported_methods = Methods} = Ssh) ->
case KbTriesLeft of
N when N<1 ->
{not_authorized, {User, {authmethod, "keyboard-interactive"}},
ssh_transport:ssh_packet(
#ssh_msg_userauth_failure{authentications = Methods,
partial_success = false}, Ssh)};
_ ->
%% RFC4256
%% The data field contains:
%% - language tag (deprecated). If =/=[] SHOULD use it however. We skip
%% it for simplicity.
%% - submethods. "... the user can give a hint of which actual methods
%% he wants to use. ...". It's a "MAY use" so we skip
%% it. It also needs an understanding between the client
%% and the server.
%%
%% "The server MUST reply with an SSH_MSG_USERAUTH_SUCCESS,
%% SSH_MSG_USERAUTH_FAILURE, or SSH_MSG_USERAUTH_INFO_REQUEST message."
Default = {"SSH server",
"Enter password for \""++User++"\"",
"password: ",
false},
{Name, Instruction, Prompt, Echo} =
case proplists:get_value(auth_method_kb_interactive_data, Opts) of
undefined ->
Default;
{_,_,_,_}=V ->
V;
F when is_function(F) ->
{_,PeerName} = Ssh#ssh.peer,
F(PeerName, User, "ssh-connection")
end,
EchoEnc = case Echo of
true -> <<?TRUE>>;
false -> <<?FALSE>>
end,
Msg = #ssh_msg_userauth_info_request{name = unicode:characters_to_list(Name),
instruction = unicode:characters_to_list(Instruction),
language_tag = "",
num_prompts = 1,
data = <<?STRING(unicode:characters_to_binary(Prompt)),
EchoEnc/binary
>>
},
{not_authorized, {User, undefined},
ssh_transport:ssh_packet(Msg, Ssh#ssh{user = User
})}
end;
handle_userauth_request(#ssh_msg_userauth_request{user = User,
service = "ssh-connection",
method = Other}, _,
#ssh{userauth_supported_methods = Methods} = Ssh) ->
{not_authorized, {User, {authmethod, Other}},
ssh_transport:ssh_packet(
#ssh_msg_userauth_failure{authentications = Methods,
partial_success = false}, Ssh)}.
%%%----------------------------------------------------------------
%%% keyboard-interactive client
handle_userauth_info_request(#ssh_msg_userauth_info_request{name = Name,
instruction = Instr,
num_prompts = NumPrompts,
data = Data},
#ssh{opts = Opts,
io_cb = IoCb
} = Ssh) ->
PromptInfos = decode_keyboard_interactive_prompts(NumPrompts,Data),
case keyboard_interact_get_responses(IoCb, Opts, Name, Instr, PromptInfos) of
not_ok ->
not_ok;
Responses ->
{ok,
ssh_transport:ssh_packet(
#ssh_msg_userauth_info_response{num_responses = NumPrompts,
data = Responses}, Ssh)}
end.
%%%----------------------------------------------------------------
%%% keyboard-interactive server
handle_userauth_info_response(#ssh_msg_userauth_info_response{num_responses = 1,
data = <<?UINT32(Sz), Password:Sz/binary>>},
#ssh{opts = Opts,
kb_tries_left = KbTriesLeft,
user = User,
userauth_supported_methods = Methods} = Ssh) ->
case check_password(User, unicode:characters_to_list(Password), Opts, Ssh) of
{true,Ssh1} ->
{authorized, User,
ssh_transport:ssh_packet(#ssh_msg_userauth_success{}, Ssh1)};
{false,Ssh1} ->
{not_authorized, {User, {error,"Bad user or password"}},
ssh_transport:ssh_packet(#ssh_msg_userauth_failure{
authentications = Methods,
partial_success = false},
Ssh1#ssh{kb_tries_left = max(KbTriesLeft-1, 0)}
)}
end;
handle_userauth_info_response(#ssh_msg_userauth_info_response{},
_Auth) ->
ssh_connection_handler:disconnect(
#ssh_msg_disconnect{code = ?SSH_DISCONNECT_SERVICE_NOT_AVAILABLE,
description = "Server does not support keyboard-interactive"
}).
%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------
method_preference(Algs) ->
lists:foldr(fun(A, Acc) ->
[{"publickey", ?MODULE, publickey_msg, [A]} | Acc]
end,
[{"password", ?MODULE, password_msg, []},
{"keyboard-interactive", ?MODULE, keyboard_interactive_msg, []}
],
Algs).
user_name(Opts) ->
Env = case os:type() of
{win32, _} ->
"USERNAME";
{unix, _} ->
"LOGNAME"
end,
case proplists:get_value(user, Opts, os:getenv(Env)) of
false ->
case os:getenv("USER") of
false ->
{error, no_user};
User ->
{ok, User}
end;
User ->
{ok, User}
end.
check_password(User, Password, Opts, Ssh) ->
case proplists:get_value(pwdfun, Opts) of
undefined ->
Static = get_password_option(Opts, User),
{Password == Static, Ssh};
Checker when is_function(Checker,2) ->
{Checker(User, Password), Ssh};
Checker when is_function(Checker,4) ->
#ssh{pwdfun_user_state = PrivateState,
peer = {_,PeerAddr={_,_}}
} = Ssh,
case Checker(User, Password, PeerAddr, PrivateState) of
true ->
{true,Ssh};
false ->
{false,Ssh};
{true,NewState} ->
{true, Ssh#ssh{pwdfun_user_state=NewState}};
{false,NewState} ->
{false, Ssh#ssh{pwdfun_user_state=NewState}};
disconnect ->
ssh_connection_handler:disconnect(
#ssh_msg_disconnect{code = ?SSH_DISCONNECT_SERVICE_NOT_AVAILABLE,
description = "Unable to connect using the available authentication methods"
})
end
end.
get_password_option(Opts, User) ->
Passwords = proplists:get_value(user_passwords, Opts, []),
case lists:keysearch(User, 1, Passwords) of
{value, {User, Pw}} -> Pw;
false -> proplists:get_value(password, Opts, false)
end.
verify_sig(SessionId, User, Service, Alg, KeyBlob, SigWLen, Opts) ->
{ok, Key} = decode_public_key_v2(KeyBlob, Alg),
KeyCb = proplists:get_value(key_cb, Opts, ssh_file),
case KeyCb:is_auth_key(Key, User, Opts) of
true ->
PlainText = build_sig_data(SessionId, User,
Service, KeyBlob, Alg),
<<?UINT32(AlgSigLen), AlgSig:AlgSigLen/binary>> = SigWLen,
<<?UINT32(AlgLen), _Alg:AlgLen/binary,
?UINT32(SigLen), Sig:SigLen/binary>> = AlgSig,
ssh_transport:verify(PlainText, sha, Sig, Key);
false ->
false
end.
build_sig_data(SessionId, User, Service, KeyBlob, Alg) ->
Sig = [?binary(SessionId),
?SSH_MSG_USERAUTH_REQUEST,
?string_utf8(User),
?string(Service),
?binary(<<"publickey">>),
?TRUE,
?string(Alg),
?binary(KeyBlob)],
list_to_binary(Sig).
decode_keyboard_interactive_prompts(_NumPrompts, Data) ->
ssh_message:decode_keyboard_interactive_prompts(Data, []).
keyboard_interact_get_responses(IoCb, Opts, Name, Instr, PromptInfos) ->
NumPrompts = length(PromptInfos),
keyboard_interact_get_responses(proplists:get_value(user_interaction, Opts, true),
proplists:get_value(keyboard_interact_fun, Opts),
proplists:get_value(password, Opts, undefined), IoCb, Name,
Instr, PromptInfos, Opts, NumPrompts).
keyboard_interact_get_responses(_, _, not_ok, _, _, _, _, _, _) ->
not_ok;
keyboard_interact_get_responses(_, undefined, Password, _, _, _, _, _,
1) when Password =/= undefined ->
[Password]; %% Password auth implemented with keyboard-interaction and passwd is known
keyboard_interact_get_responses(_, _, _, _, _, _, _, _, 0) ->
[];
keyboard_interact_get_responses(false, undefined, undefined, _, _, _, [Prompt|_], Opts, _) ->
ssh_no_io:read_line(Prompt, Opts); %% Throws error as keyboard interaction is not allowed
keyboard_interact_get_responses(true, undefined, _,IoCb, Name, Instr, PromptInfos, Opts, _) ->
keyboard_interact(IoCb, Name, Instr, PromptInfos, Opts);
keyboard_interact_get_responses(true, Fun, _Pwd, _IoCb, Name, Instr, PromptInfos, _Opts, NumPrompts) ->
keyboard_interact_fun(Fun, Name, Instr, PromptInfos, NumPrompts).
keyboard_interact(IoCb, Name, Instr, Prompts, Opts) ->
write_if_nonempty(IoCb, Name),
write_if_nonempty(IoCb, Instr),
lists:map(fun({Prompt, true}) -> IoCb:read_line(Prompt, Opts);
({Prompt, false}) -> IoCb:read_password(Prompt, Opts)
end,
Prompts).
write_if_nonempty(_, "") -> ok;
write_if_nonempty(_, <<>>) -> ok;
write_if_nonempty(IoCb, Text) -> IoCb:format("~s~n",[Text]).
keyboard_interact_fun(KbdInteractFun, Name, Instr, PromptInfos, NumPrompts) ->
Prompts = lists:map(fun({Prompt, _Echo}) -> Prompt end,
PromptInfos),
case KbdInteractFun(Name, Instr, Prompts) of
Rs when length(Rs) == NumPrompts ->
Rs;
Rs ->
throw({mismatching_number_of_responses,
{got,Rs},
{expected, NumPrompts},
#ssh_msg_disconnect{code = ?SSH_DISCONNECT_SERVICE_NOT_AVAILABLE,
description = "User interaction failed",
language = "en"}})
end.
decode_public_key_v2(Bin, _Type) ->
try
public_key:ssh_decode(Bin, ssh2_pubkey)
of
Key -> {ok, Key}
catch
_:_ -> {error, bad_format}
end.
encode_public_key(_Alg, Key) ->
try
public_key:ssh_encode(Key, ssh2_pubkey)
catch
_:_ -> not_ok
end.
