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