path: root/src/ejabberd_auth.erl

%%%----------------------------------------------------------------------
%%% File    : ejabberd_auth.erl
%%% Author  : Alexey Shchepin <alexey@process-one.net>
%%% Purpose : Authentification
%%% Created : 23 Nov 2002 by Alexey Shchepin <alexey@process-one.net>
%%%
%%%
%%% ejabberd, Copyright (C) 2002-2017   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.,
%%% 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
%%%
%%%----------------------------------------------------------------------
-module(ejabberd_auth).

-behaviour(gen_server).
-behaviour(ejabberd_config).

-author('alexey@process-one.net').

%% External exports
-export([start_link/0, host_up/1, host_down/1, config_reloaded/0,
	 set_password/3, check_password/4,
	 check_password/6, check_password_with_authmodule/4,
	 check_password_with_authmodule/6, try_register/3,
	 get_users/0, get_users/1, password_to_scram/1,
	 get_users/2, export/1, import_info/0,
	 count_users/1, import/5, import_start/2,
	 count_users/2, get_password/2,
	 get_password_s/2, get_password_with_authmodule/2,
	 user_exists/2, user_exists_in_other_modules/3,
	 remove_user/2, remove_user/3, plain_password_required/1,
	 store_type/1, entropy/1, backend_type/1, password_format/1]).
%% gen_server callbacks
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
	 terminate/2, code_change/3]).

-export([auth_modules/1, opt_type/1]).

-include("ejabberd.hrl").
-include("logger.hrl").

-define(AUTH_CACHE, auth_cache).
-define(SALT_LENGTH, 16).

-record(state, {host_modules = #{} :: map()}).

-type password() :: binary() | #scram{}.
-type digest_fun() :: fun((binary()) -> binary()).
-export_type([password/0]).

%%%----------------------------------------------------------------------
%%% API
%%%----------------------------------------------------------------------
-type opts() :: [{prefix, binary()} | {from, integer()} |
                 {to, integer()} | {limit, integer()} |
                 {offset, integer()}].

-callback start(binary()) -> any().
-callback stop(binary()) -> any().
-callback plain_password_required(binary()) -> boolean().
-callback store_type(binary()) -> plain | external | scram.
-callback set_password(binary(), binary(), binary()) -> ok | {error, atom()}.
-callback remove_user(binary(), binary()) -> ok | {error, any()}.
-callback user_exists(binary(), binary()) -> boolean() | {error, atom()}.
-callback check_password(binary(), binary(), binary(), binary()) -> boolean().
-callback try_register(binary(), binary(), password()) -> ok | {error, atom()}.
-callback get_users(binary(), opts()) -> [{binary(), binary()}].
-callback count_users(binary(), opts()) -> number().
-callback get_password(binary(), binary()) -> {ok, password()} | error.
-callback use_cache(binary()) -> boolean().
-callback cache_nodes(binary()) -> boolean().

-optional_callbacks([set_password/3,
		     remove_user/2,
		     user_exists/2,
		     check_password/4,
		     try_register/3,
		     get_users/2,
		     count_users/2,
		     get_password/2,
		     use_cache/1,
		     cache_nodes/1]).

-spec start_link() -> {ok, pid()} | {error, any()}.
start_link() ->
    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).

init([]) ->
    ejabberd_hooks:add(host_up, ?MODULE, host_up, 30),
    ejabberd_hooks:add(host_down, ?MODULE, host_down, 80),
    ejabberd_hooks:add(config_reloaded, ?MODULE, config_reloaded, 40),
    HostModules = lists:foldl(
		    fun(Host, Acc) ->
			    Modules = auth_modules(Host),
			    maps:put(Host, Modules, Acc)
		    end, #{}, ?MYHOSTS),
    lists:foreach(
      fun({Host, Modules}) ->
	      start(Host, Modules)
      end, maps:to_list(HostModules)),
    init_cache(HostModules),
    {ok, #state{host_modules = HostModules}}.

handle_call(_Request, _From, State) ->
    Reply = ok,
    {reply, Reply, State}.

handle_cast({host_up, Host}, #state{host_modules = HostModules} = State) ->
    Modules = auth_modules(Host),
    start(Host, Modules),
    NewHostModules = maps:put(Host, Modules, HostModules),
    init_cache(NewHostModules),
    {noreply, State#state{host_modules = NewHostModules}};
handle_cast({host_down, Host}, #state{host_modules = HostModules} = State) ->
    Modules = maps:get(Host, HostModules, []),
    stop(Host, Modules),
    NewHostModules = maps:remove(Host, HostModules),
    init_cache(NewHostModules),
    {noreply, State#state{host_modules = NewHostModules}};
handle_cast(config_reloaded, #state{host_modules = HostModules} = State) ->
    NewHostModules = lists:foldl(
		       fun(Host, Acc) ->
			       OldModules = maps:get(Host, HostModules, []),
			       NewModules = auth_modules(Host),
			       start(Host, NewModules -- OldModules),
			       stop(Host, OldModules -- NewModules),
			       maps:put(Host, NewModules, Acc)
		       end, HostModules, ?MYHOSTS),
    init_cache(NewHostModules),
    {noreply, State#state{host_modules = NewHostModules}};
handle_cast(Msg, State) ->
    ?WARNING_MSG("unexpected cast: ~p", [Msg]),
    {noreply, State}.

handle_info(_Info, State) ->
    {noreply, State}.

terminate(_Reason, State) ->
    ejabberd_hooks:delete(host_up, ?MODULE, start, 30),
    ejabberd_hooks:delete(host_down, ?MODULE, stop, 80),
    ejabberd_hooks:delete(config_reloaded, ?MODULE, config_reloaded, 40),
    lists:foreach(
      fun({Host, Modules}) ->
	      stop(Host, Modules)
      end, maps:to_list(State#state.host_modules)).

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

start(Host, Modules) ->
    lists:foreach(fun(M) -> M:start(Host) end, Modules).

stop(Host, Modules) ->
    lists:foreach(fun(M) -> M:stop(Host) end, Modules).

host_up(Host) ->
    gen_server:cast(?MODULE, {host_up, Host}).

host_down(Host) ->
    gen_server:cast(?MODULE, {host_down, Host}).

config_reloaded() ->
    gen_server:cast(?MODULE, config_reloaded).

-spec plain_password_required(binary()) -> boolean().
plain_password_required(Server) ->
    lists:any(fun (M) -> M:plain_password_required(Server) end,
	      auth_modules(Server)).

-spec store_type(binary()) -> plain | scram | external.
store_type(Server) ->
    lists:foldl(
      fun(_, external) -> external;
	 (M, scram) ->
	      case M:store_type(Server) of
		  external -> external;
		  _ -> scram
	      end;
	 (M, plain) ->
	      M:store_type(Server)
      end, plain, auth_modules(Server)).

-spec check_password(binary(), binary(), binary(), binary()) -> boolean().
check_password(User, AuthzId, Server, Password) ->
    check_password(User, AuthzId, Server, Password, <<"">>, undefined).

-spec check_password(binary(), binary(), binary(), binary(), binary(),
                     digest_fun() | undefined) -> boolean().
check_password(User, AuthzId, Server, Password, Digest, DigestGen) ->
    case check_password_with_authmodule(
	   User, AuthzId, Server, Password, Digest, DigestGen) of
	{true, _AuthModule} -> true;
	false -> false
    end.

-spec check_password_with_authmodule(binary(), binary(),
				     binary(), binary()) -> false | {true, atom()}.
check_password_with_authmodule(User, AuthzId, Server, Password) ->
    check_password_with_authmodule(
      User, AuthzId, Server, Password, <<"">>, undefined).

-spec check_password_with_authmodule(
	binary(), binary(), binary(), binary(), binary(),
	digest_fun() | undefined) -> false | {true, atom()}.
check_password_with_authmodule(User, AuthzId, Server, Password, Digest, DigestGen) ->
    case validate_credentials(User, Server) of
	{ok, LUser, LServer} ->
	    lists:foldl(
	      fun(Mod, false) ->
		      case db_check_password(
			     LUser, AuthzId, LServer, Password,
			     Digest, DigestGen, Mod) of
			  true -> {true, Mod};
			  false -> false
		      end;
		 (_, Acc) ->
		      Acc
	      end, false, auth_modules(LServer));
	_ ->
	    false
    end.

-spec set_password(binary(), binary(), password()) -> ok | {error, atom()}.
set_password(User, Server, Password) ->
    case validate_credentials(User, Server, Password) of
	{ok, LUser, LServer} ->
	    lists:foldl(
	      fun(M, {error, _}) ->
		      db_set_password(LUser, LServer, Password, M);
		 (_, ok) ->
		      ok
	      end, {error, not_allowed}, auth_modules(LServer));
	Err ->
	    Err
    end.

-spec try_register(binary(), binary(), password()) -> ok | {error, atom()}.
try_register(User, Server, Password) ->
    case validate_credentials(User, Server, Password) of
	{ok, LUser, LServer} ->
	    case user_exists(LUser, LServer) of
		true ->
		    {error, exists};
		false ->
		    case ejabberd_router:is_my_host(LServer) of
			true ->
			    case lists:foldl(
				   fun(_, ok) ->
					   ok;
				      (Mod, _) ->
					   db_try_register(
					     LUser, LServer, Password, Mod)
				   end, {error, not_allowed},
				   auth_modules(LServer)) of
				ok ->
				    ejabberd_hooks:run(
				      register_user, LServer, [LUser, LServer]);
				{error, _} = Err ->
				    Err
			    end;
			false ->
			    {error, not_allowed}
		    end
	    end;
	Err ->
	    Err
    end.

-spec get_users() -> [{binary(), binary()}].
get_users() ->
    lists:flatmap(
      fun({Host, Mod}) ->
	      db_get_users(Host, [], Mod)
      end, auth_modules()).

-spec get_users(binary()) -> [{binary(), binary()}].
get_users(Server) ->
    get_users(Server, []).

-spec get_users(binary(), opts()) -> [{binary(), binary()}].
get_users(Server, Opts) ->
    case jid:nameprep(Server) of
	error -> [];
	LServer ->
	    lists:flatmap(
	      fun(M) -> db_get_users(LServer, Opts, M) end,
	      auth_modules(LServer))
    end.

-spec count_users(binary()) -> non_neg_integer().
count_users(Server) ->
    count_users(Server, []).

-spec count_users(binary(), opts()) -> non_neg_integer().
count_users(Server, Opts) ->
    case jid:nameprep(Server) of
	error -> 0;
	LServer ->
	    lists:sum(
	      lists:map(
		fun(M) -> db_count_users(LServer, Opts, M) end,
		auth_modules(LServer)))
    end.

-spec get_password(binary(), binary()) -> false | password().
get_password(User, Server) ->
    case validate_credentials(User, Server) of
	{ok, LUser, LServer} ->
	    case lists:foldl(
		   fun(M, error) -> db_get_password(LUser, LServer, M);
		      (_M, Acc) -> Acc
		   end, error, auth_modules(LServer)) of
		{ok, Password} ->
		    Password;
		error ->
		    false
	    end;
	_ ->
	    false
    end.

-spec get_password_s(binary(), binary()) -> password().
get_password_s(User, Server) ->
    case get_password(User, Server) of
      false -> <<"">>;
      Password -> Password
    end.

-spec get_password_with_authmodule(binary(), binary()) -> {false | password(), module()}.
get_password_with_authmodule(User, Server) ->
    case validate_credentials(User, Server) of
	{ok, LUser, LServer} ->
	    case lists:foldl(
		   fun(M, {error, _}) ->
			   {db_get_password(LUser, LServer, M), M};
		      (_M, Acc) ->
			   Acc
		   end, {error, undefined}, auth_modules(LServer)) of
		{{ok, Password}, Module} ->
		    {Password, Module};
		{error, Module} ->
		    {false, Module}
	    end;
	_ ->
	    {false, undefined}
    end.

-spec user_exists(binary(), binary()) -> boolean().
user_exists(_User, <<"">>) ->
    false;
user_exists(User, Server) ->
    case validate_credentials(User, Server) of
	{ok, LUser, LServer} ->
	    lists:any(
	      fun(M) ->
		      case db_user_exists(LUser, LServer, M) of
			  {error, _} ->
			      false;
			  Else ->
			      Else
		      end
	      end, auth_modules(LServer));
	_ ->
	    false
    end.

-spec user_exists_in_other_modules(atom(), binary(), binary()) -> boolean() | maybe.
user_exists_in_other_modules(Module, User, Server) ->
    user_exists_in_other_modules_loop(
      auth_modules(Server) -- [Module], User, Server).

user_exists_in_other_modules_loop([], _User, _Server) ->
    false;
user_exists_in_other_modules_loop([AuthModule | AuthModules], User, Server) ->
    case db_user_exists(User, Server, AuthModule) of
	true ->
	    true;
	false ->
	    user_exists_in_other_modules_loop(AuthModules, User, Server);
	{error, _} ->
	    maybe
    end.

-spec remove_user(binary(), binary()) -> ok.
remove_user(User, Server) ->
    case validate_credentials(User, Server) of
	{ok, LUser, LServer} ->
	    lists:foreach(
	      fun(Mod) -> db_remove_user(LUser, LServer, Mod) end,
	      auth_modules(LServer)),
	    ejabberd_hooks:run(remove_user, LServer, [LUser, LServer]);
	_Err ->
	    ok
    end.

-spec remove_user(binary(), binary(), password()) -> ok | {error, atom()}.
remove_user(User, Server, Password) ->
    case validate_credentials(User, Server, Password) of
	{ok, LUser, LServer} ->
	    case lists:foldl(
		   fun (_, ok) ->
			   ok;
		       (Mod, _) ->
			   case db_check_password(
				  LUser, <<"">>, LServer, Password,
				  <<"">>, undefined, Mod) of
			       true ->
				   db_remove_user(LUser, LServer, Mod);
			       false ->
				   {error, not_allowed}
			   end
		   end, {error, not_allowed}, auth_modules(Server)) of
		ok ->
		    ejabberd_hooks:run(
		      remove_user, LServer, [LUser, LServer]);
		Err ->
		    Err
	    end;
	Err ->
	    Err
    end.

%% @doc Calculate informational entropy.
-spec entropy(iodata()) -> float().
entropy(B) ->
    case binary_to_list(B) of
      "" -> 0.0;
      S ->
	  Set = lists:foldl(fun (C,
				 [Digit, Printable, LowLetter, HiLetter,
				  Other]) ->
				    if C >= $a, C =< $z ->
					   [Digit, Printable, 26, HiLetter,
					    Other];
				       C >= $0, C =< $9 ->
					   [9, Printable, LowLetter, HiLetter,
					    Other];
				       C >= $A, C =< $Z ->
					   [Digit, Printable, LowLetter, 26,
					    Other];
				       C >= 33, C =< 126 ->
					   [Digit, 33, LowLetter, HiLetter,
					    Other];
				       true ->
					   [Digit, Printable, LowLetter,
					    HiLetter, 128]
				    end
			    end,
			    [0, 0, 0, 0, 0], S),
	  length(S) * math:log(lists:sum(Set)) / math:log(2)
    end.

-spec backend_type(atom()) -> atom().
backend_type(Mod) ->
    case atom_to_list(Mod) of
	"ejabberd_auth_" ++ T -> list_to_atom(T);
	_ -> Mod
    end.

-spec password_format(binary() | global) -> plain | scram.
password_format(LServer) ->
    ejabberd_config:get_option({auth_password_format, LServer}, plain).

%%%----------------------------------------------------------------------
%%% Backend calls
%%%----------------------------------------------------------------------
db_try_register(User, Server, Password, Mod) ->
    case erlang:function_exported(Mod, try_register, 3) of
	true ->
	    Password1 = case Mod:store_type(Server) of
			    scram -> password_to_scram(Password);
			    _ -> Password
			end,
	    case use_cache(Mod, Server) of
		true ->
		    case ets_cache:update(
			   ?AUTH_CACHE, {User, Server}, {ok, Password},
			   fun() -> Mod:try_register(User, Server, Password1) end,
			   cache_nodes(Mod, Server)) of
			{ok, _} -> ok;
			{error, _} = Err -> Err
		    end;
		false ->
		    Mod:try_register(User, Server, Password1)
	    end;
	false ->
	    {error, not_allowed}
    end.

db_set_password(User, Server, Password, Mod) ->
    case erlang:function_exported(Mod, set_password, 3) of
	true ->
	    Password1 = case Mod:store_type(Server) of
			    scram -> password_to_scram(Password);
			    _ -> Password
			end,
	    case use_cache(Mod, Server) of
		true ->
		    case ets_cache:update(
			   ?AUTH_CACHE, {User, Server}, {ok, Password},
			   fun() -> Mod:set_password(User, Server, Password1) end,
			   cache_nodes(Mod, Server)) of
			{ok, _} -> ok;
			{error, _} = Err -> Err
		    end;
		false ->
		    Mod:set_password(User, Server, Password1)
	    end;
	false ->
	    {error, not_allowed}
    end.

db_get_password(User, Server, Mod) ->
    UseCache = use_cache(Mod, Server),
    case erlang:function_exported(Mod, get_password, 2) of
	false when UseCache ->
	    ets_cache:lookup(?AUTH_CACHE, {User, Server});
	false ->
	    error;
	true when UseCache ->
	    ets_cache:lookup(
	      ?AUTH_CACHE, {User, Server},
	      fun() -> Mod:get_password(User, Server) end);
	true ->
	    Mod:get_password(User, Server)
    end.

db_user_exists(User, Server, Mod) ->
    case db_get_password(User, Server, Mod) of
	{ok, _} ->
	    true;
	error ->
	    case Mod:store_type(Server) of
		external ->
		    Mod:user_exists(User, Server);
		_ ->
		    false
	    end
    end.

db_check_password(User, AuthzId, Server, ProvidedPassword,
		  Digest, DigestFun, Mod) ->
    case db_get_password(User, Server, Mod) of
	{ok, ValidPassword} ->
	    match_passwords(ProvidedPassword, ValidPassword, Digest, DigestFun);
	error ->
	    case {Mod:store_type(Server), use_cache(Mod, Server)} of
		{external, true} ->
		    case ets_cache:update(
			   ?AUTH_CACHE, {User, Server}, {ok, ProvidedPassword},
			   fun() ->
				   case Mod:check_password(
					  User, AuthzId, Server, ProvidedPassword) of
				       true ->
					   {ok, ProvidedPassword};
				       false ->
					   error
				   end
			   end, cache_nodes(Mod, Server)) of
			{ok, _} ->
			    true;
			error ->
			    false
		    end;
		{external, false} ->
		    Mod:check_password(User, AuthzId, Server, ProvidedPassword);
		_ ->
		    false
	    end
    end.

db_remove_user(User, Server, Mod) ->
    case erlang:function_exported(Mod, remove_user, 2) of
	true ->
	    case Mod:remove_user(User, Server) of
		ok ->
		    case use_cache(Mod, Server) of
			true ->
			    ets_cache:delete(?AUTH_CACHE, {User, Server},
					     cache_nodes(Mod, Server));
			false ->
			    ok
		    end;
		{error, _} = Err ->
		    Err
	    end;
	false ->
	    {error, not_allowed}
    end.

db_get_users(Server, Opts, Mod) ->
    case erlang:function_exported(Mod, get_users, 2) of
	true ->
	    Mod:get_users(Server, Opts);
	false ->
	    case use_cache(Mod, Server) of
		true ->
		    ets_cache:fold(
		      fun({User, S}, {ok, _}, Users) when S == Server ->
			      [{User, Server}|Users];
			 (_, _, Users) ->
			      Users
		      end, [], ?AUTH_CACHE);
		false ->
		    []
	    end
    end.

db_count_users(Server, Opts, Mod) ->
    case erlang:function_exported(Mod, count_users, 2) of
	true ->
	    Mod:count_users(Server, Opts);
	false ->
	    case use_cache(Mod, Server) of
		true ->
		    ets_cache:fold(
		      fun({_, S}, {ok, _}, Num) when S == Server ->
			      Num + 1;
			 (_, _, Num) ->
			      Num
		      end, 0, ?AUTH_CACHE);
		false ->
		    0
	    end
    end.

%%%----------------------------------------------------------------------
%%% SCRAM stuff
%%%----------------------------------------------------------------------
is_password_scram_valid(Password, Scram) ->
    case jid:resourceprep(Password) of
	error ->
	    false;
	_ ->
	    IterationCount = Scram#scram.iterationcount,
	    Salt = base64:decode(Scram#scram.salt),
	    SaltedPassword = scram:salted_password(Password, Salt, IterationCount),
	    StoredKey =	scram:stored_key(scram:client_key(SaltedPassword)),
	    base64:decode(Scram#scram.storedkey) == StoredKey
    end.

password_to_scram(Password) ->
    password_to_scram(Password, ?SCRAM_DEFAULT_ITERATION_COUNT).

password_to_scram(#scram{} = Password, _IterationCount) ->
    Password;
password_to_scram(Password, IterationCount) ->
    Salt = randoms:bytes(?SALT_LENGTH),
    SaltedPassword = scram:salted_password(Password, Salt, IterationCount),
    StoredKey = scram:stored_key(scram:client_key(SaltedPassword)),
    ServerKey = scram:server_key(SaltedPassword),
    #scram{storedkey = base64:encode(StoredKey),
	   serverkey = base64:encode(ServerKey),
	   salt = base64:encode(Salt),
	   iterationcount = IterationCount}.

%%%----------------------------------------------------------------------
%%% Cache stuff
%%%----------------------------------------------------------------------
-spec init_cache(map()) -> ok.
init_cache(HostModules) ->
    case use_cache(HostModules) of
	true ->
	    ets_cache:new(?AUTH_CACHE, cache_opts());
	false ->
	    ets_cache:delete(?AUTH_CACHE)
    end.

-spec cache_opts() -> [proplists:property()].
cache_opts() ->
    MaxSize = ejabberd_config:get_option(
		auth_cache_size,
		ejabberd_config:cache_size(global)),
    CacheMissed = ejabberd_config:get_option(
		    auth_cache_missed,
		    ejabberd_config:cache_missed(global)),
    LifeTime = case ejabberd_config:get_option(
		      auth_cache_life_time,
		      ejabberd_config:cache_life_time(global)) of
		   infinity -> infinity;
		   I -> timer:seconds(I)
	       end,
    [{max_size, MaxSize}, {cache_missed, CacheMissed}, {life_time, LifeTime}].

-spec use_cache(map()) -> boolean().
use_cache(HostModules) ->
    lists:any(
      fun({Host, Modules}) ->
	      lists:any(fun(Module) ->
				use_cache(Module, Host)
			end, Modules)
      end, maps:to_list(HostModules)).

-spec use_cache(module(), binary()) -> boolean().
use_cache(Mod, LServer) ->
    case erlang:function_exported(Mod, use_cache, 1) of
	true -> Mod:use_cache(LServer);
	false ->
	    ejabberd_config:get_option(
	      {auth_use_cache, LServer},
	      ejabberd_config:use_cache(LServer))
    end.

-spec cache_nodes(module(), binary()) -> [node()].
cache_nodes(Mod, LServer) ->
    case erlang:function_exported(Mod, cache_nodes, 1) of
	true -> Mod:cache_nodes(LServer);
	false -> ejabberd_cluster:get_nodes()
    end.

%%%----------------------------------------------------------------------
%%% Internal functions
%%%----------------------------------------------------------------------
-spec auth_modules() -> [{binary(), module()}].
auth_modules() ->
    lists:flatmap(
      fun(Host) ->
	      [{Host, Mod} || Mod <- auth_modules(Host)]
      end, ?MYHOSTS).

-spec auth_modules(binary()) -> [module()].
auth_modules(Server) ->
    LServer = jid:nameprep(Server),
    Default = ejabberd_config:default_db(LServer, ?MODULE),
    Methods = ejabberd_config:get_option({auth_method, LServer}, [Default]),
    [misc:binary_to_atom(<<"ejabberd_auth_",
			   (misc:atom_to_binary(M))/binary>>)
     || M <- Methods].

-spec match_passwords(password(), password(),
		      binary(), digest_fun() | undefined) -> boolean().
match_passwords(Password, #scram{} = Scram, <<"">>, undefined) ->
    is_password_scram_valid(Password, Scram);
match_passwords(Password, #scram{} = Scram, Digest, DigestFun) ->
    StoredKey = base64:decode(Scram#scram.storedkey),
    DigRes = if Digest /= <<"">> ->
		     Digest == DigestFun(StoredKey);
		true -> false
	     end,
    if DigRes ->
	    true;
       true ->
	    StoredKey == Password andalso Password /= <<"">>
    end;
match_passwords(ProvidedPassword, ValidPassword, <<"">>, undefined) ->
    ProvidedPassword == ValidPassword andalso ProvidedPassword /= <<"">>;
match_passwords(ProvidedPassword, ValidPassword, Digest, DigestFun) ->
    DigRes = if Digest /= <<"">> ->
		     Digest == DigestFun(ValidPassword);
		true -> false
	     end,
    if DigRes ->
	    true;
       true ->
	    ValidPassword == ProvidedPassword andalso ProvidedPassword /= <<"">>
    end.

-spec validate_credentials(binary(), binary()) ->
      {ok, binary(), binary()} | {error, invalid_jid}.
validate_credentials(User, Server) ->
    validate_credentials(User, Server, #scram{}).

-spec validate_credentials(binary(), binary(), password()) ->
      {ok, binary(), binary()} | {error, invalid_jid | invalid_password}.
validate_credentials(_User, _Server, <<"">>) ->
    {error, invalid_password};
validate_credentials(User, Server, Password) ->
    case jid:nodeprep(User) of
	error ->
	    {error, invalid_jid};
	LUser ->
	    case jid:nameprep(Server) of
		error ->
		    {error, invalid_jid};
		LServer ->
		    if is_record(Password, scram) ->
			    {ok, LUser, LServer};
		       true ->
			    case jid:resourceprep(Password) of
				error ->
				    {error, invalid_password};
				_ ->
				    {ok, LUser, LServer}
			    end
		    end
	    end
    end.

export(Server) ->
    ejabberd_auth_mnesia:export(Server).

import_info() ->
    [{<<"users">>, 3}].

import_start(_LServer, mnesia) ->
    ejabberd_auth_mnesia:init_db();
import_start(_LServer, _) ->
    ok.

import(Server, {sql, _}, mnesia, <<"users">>, Fields) ->
    ejabberd_auth_mnesia:import(Server, Fields);
import(Server, {sql, _}, riak, <<"users">>, Fields) ->
    ejabberd_auth_riak:import(Server, Fields);
import(_LServer, {sql, _}, sql, <<"users">>, _) ->
    ok.

-spec opt_type(auth_method) -> fun((atom() | [atom()]) -> [atom()]);
	      (auth_password_format) -> fun((plain | scram) -> plain | scram);
	      (auth_use_cache) -> fun((boolean()) -> boolean());
	      (auth_cache_missed) -> fun((boolean()) -> boolean());
	      (auth_cache_life_time) -> fun((timeout()) -> timeout());
	      (auth_cache_size) -> fun((timeout()) -> timeout());
	      (atom()) -> [atom()].
opt_type(auth_method) ->
    fun (V) when is_list(V) ->
	    lists:map(fun(M) -> ejabberd_config:v_db(?MODULE, M) end, V);
	(V) -> [ejabberd_config:v_db(?MODULE, V)]
    end;
opt_type(auth_password_format) ->
    fun (plain) -> plain;
	(scram) -> scram
    end;
opt_type(auth_use_cache) ->
    fun(B) when is_boolean(B) -> B end;
opt_type(auth_cache_missed) ->
    fun(B) when is_boolean(B) -> B end;
opt_type(auth_cache_life_time) ->
    fun(I) when is_integer(I), I>0 -> I;
       (unlimited) -> infinity;
       (infinity) -> infinity
    end;
opt_type(auth_cache_size) ->
    fun(I) when is_integer(I), I>0 -> I;
       (unlimited) -> infinity;
       (infinity) -> infinity
    end;
opt_type(_) ->
    [auth_method, auth_password_format, auth_use_cache,
     auth_cache_missed, auth_cache_life_time, auth_cache_size].