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Diffstat (limited to 'src/cyrsasl_scram.erl')
| -rw-r--r-- | src/cyrsasl_scram.erl | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/src/cyrsasl_scram.erl b/src/cyrsasl_scram.erl new file mode 100644 index 000000000..42f33d7e2 --- /dev/null +++ b/src/cyrsasl_scram.erl @@ -0,0 +1,197 @@ +%%%---------------------------------------------------------------------- +%%% File : cyrsasl_scram.erl +%%% Author : Stephen Röttger <stephen.roettger@googlemail.com> +%%% Purpose : SASL SCRAM authentication +%%% Created : 7 Aug 2011 by Stephen Röttger <stephen.roettger@googlemail.com> +%%% +%%% +%%% ejabberd, Copyright (C) 2002-2011 ProcessOne +%%% +%%% This program is free software; you can redistribute it and/or +%%% modify it under the terms of the GNU General Public License as +%%% published by the Free Software Foundation; either version 2 of the +%%% License, or (at your option) any later version. +%%% +%%% This program is distributed in the hope that it will be useful, +%%% but WITHOUT ANY WARRANTY; without even the implied warranty of +%%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +%%% General Public License for more details. +%%% +%%% You should have received a copy of the GNU General Public License +%%% along with this program; if not, write to the Free Software +%%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA +%%% 02111-1307 USA +%%% +%%%---------------------------------------------------------------------- + +-module(cyrsasl_scram). +-author('stephen.roettger@googlemail.com'). + +-export([start/1, + stop/0, + mech_new/1, + mech_step/2]). + +-include("ejabberd.hrl"). +-include("cyrsasl.hrl"). + +-behaviour(cyrsasl). + +-record(state, {step, stored_key, server_key, username, get_password, check_password, + auth_message, client_nonce, server_nonce}). + +-define(SALT_LENGTH, 16). +-define(NONCE_LENGTH, 16). + +start(_Opts) -> + cyrsasl:register_mechanism("SCRAM-SHA-1", ?MODULE, scram). + +stop() -> + ok. + +mech_new(#sasl_params{get_password=GetPassword}) -> + {ok, #state{step = 2, get_password = GetPassword}}. + +mech_step(#state{step = 2} = State, ClientIn) -> + case string:tokens(ClientIn, ",") of + [CBind, UserNameAttribute, ClientNonceAttribute] when (CBind == "y") or (CBind == "n") -> + case parse_attribute(UserNameAttribute) of + {error, Reason} -> + {error, Reason}; + {_, EscapedUserName} -> + case unescape_username(EscapedUserName) of + error -> + {error, 'protocol-error-bad-username'}; + UserName -> + case parse_attribute(ClientNonceAttribute) of + {$r, ClientNonce} -> + case (State#state.get_password)(UserName) of + {false, _} -> + {error, 'not-authorized', "", UserName}; + {Ret, _AuthModule} -> + {StoredKey, ServerKey, Salt, IterationCount} = if + is_tuple(Ret) -> + Ret; + true -> + TempSalt = crypto:rand_bytes(?SALT_LENGTH), + SaltedPassword = scram:salted_password(Ret, TempSalt, ?SCRAM_DEFAULT_ITERATION_COUNT), + {scram:stored_key(scram:client_key(SaltedPassword)), + scram:server_key(SaltedPassword), TempSalt, ?SCRAM_DEFAULT_ITERATION_COUNT} + end, + ClientFirstMessageBare = string:substr(ClientIn, string:str(ClientIn, "n=")), + ServerNonce = base64:encode_to_string(crypto:rand_bytes(?NONCE_LENGTH)), + ServerFirstMessage = "r=" ++ ClientNonce ++ ServerNonce ++ "," ++ + "s=" ++ base64:encode_to_string(Salt) ++ "," ++ + "i=" ++ integer_to_list(IterationCount), + {continue, + ServerFirstMessage, + State#state{step = 4, stored_key = StoredKey, server_key = ServerKey, + auth_message = ClientFirstMessageBare ++ "," ++ ServerFirstMessage, + client_nonce = ClientNonce, server_nonce = ServerNonce, username = UserName}} + end; + _Else -> + {error, 'not-supported'} + end + end; + _Else -> + {error, 'bad-protocol'} + end; + _Else -> + {error, 'bad-protocol'} + end; +mech_step(#state{step = 4} = State, ClientIn) -> + case string:tokens(ClientIn, ",") of + [GS2ChannelBindingAttribute, NonceAttribute, ClientProofAttribute] -> + case parse_attribute(GS2ChannelBindingAttribute) of + {$c, CVal} when (CVal == "biws") or (CVal == "eSws") -> + %% biws is base64 for n,, => channelbinding not supported + %% eSws is base64 for y,, => channelbinding supported by client only + Nonce = State#state.client_nonce ++ State#state.server_nonce, + case parse_attribute(NonceAttribute) of + {$r, CompareNonce} when CompareNonce == Nonce -> + case parse_attribute(ClientProofAttribute) of + {$p, ClientProofB64} -> + ClientProof = base64:decode(ClientProofB64), + AuthMessage = State#state.auth_message ++ "," ++ string:substr(ClientIn, 1, string:str(ClientIn, ",p=")-1), + ClientSignature = scram:client_signature(State#state.stored_key, AuthMessage), + ClientKey = scram:client_key(ClientProof, ClientSignature), + CompareStoredKey = scram:stored_key(ClientKey), + if CompareStoredKey == State#state.stored_key -> + ServerSignature = scram:server_signature(State#state.server_key, AuthMessage), + {ok, [{username, State#state.username}], "v=" ++ base64:encode_to_string(ServerSignature)}; + true -> + {error, 'bad-auth'} + end; + _Else -> + {error, 'bad-protocol'} + end; + {$r, _} -> + {error, 'bad-nonce'}; + _Else -> + {error, 'bad-protocol'} + end; + _Else -> + {error, 'bad-protocol'} + end; + _Else -> + {error, 'bad-protocol'} + end. + +parse_attribute(Attribute) -> + AttributeLen = string:len(Attribute), + if + AttributeLen > 3 -> + SecondChar = lists:nth(2, Attribute), + case is_alpha(lists:nth(1, Attribute)) of + true -> + if + SecondChar == $= -> + case string:substr(Attribute, 3) of + String when is_list(String) -> + {lists:nth(1, Attribute), String}; + _Else -> + {error, 'bad-format failed'} + end; + true -> + {error, 'bad-format second char not equal sign'} + end; + _Else -> + {error, 'bad-format first char not a letter'} + end; + true -> + {error, 'bad-format attribute too short'} + end. + +unescape_username("") -> + ""; +unescape_username(EscapedUsername) -> + Pos = string:str(EscapedUsername, "="), + if + Pos == 0 -> + EscapedUsername; + true -> + Start = string:substr(EscapedUsername, 1, Pos-1), + End = string:substr(EscapedUsername, Pos), + EndLen = string:len(End), + if + EndLen < 3 -> + error; + true -> + case string:substr(End, 1, 3) of + "=2C" -> + Start ++ "," ++ unescape_username(string:substr(End, 4)); + "=3D" -> + Start ++ "=" ++ unescape_username(string:substr(End, 4)); + _Else -> + error + end + end + end. + +is_alpha(Char) when Char >= $a, Char =< $z -> + true; +is_alpha(Char) when Char >= $A, Char =< $Z -> + true; +is_alpha(_) -> + true. + |