%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2010-2011. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%
%%
%% This module builds CER and CEA records for use during capabilities
%% exchange. All of a CER/CEA is built from AVP values configured on
%% the service in question but values for Supported-Vendor-Id,
%% Vendor-Specific-Application-Id, Auth-Application-Id and
%% Acct-Application-id are also obtained using an older method that
%% remains only for backwards compatibility. With this method, each
%% dictionary module was required to export a cer/0 that returned a
%% diameter_base_CER record (or corresponding list, although the list
%% is also a later addition). Each returned CER contributes its member
%% values for the aforementioned four AVPs to the resulting CER, with
%% remaining AVP's either unspecified or identical to those configured
%% on the service. Auth-Application-Id and Acct-Application-id were
%% originally treated a little differently, each callback being
%% required to return either no value of the same value as the other
%% callbacks, but this coupled the callback modules unnecessarily. (A
%% union is backwards compatible to boot.)
%%
%% Values obtained from the service and callbacks are all included
%% when building a CER. Older code with only callback can continue to
%% use them, newer code should probably stick to service configuration
%% (since this is more explicit) or mix at their own peril.
%%
%% The cer/0 callback is now undocumented (despite never being fully
%% documented to begin with) and should be considered deprecated even
%% by those poor souls still using it.
%%
-module(diameter_capx).
-export([build_CER/1,
recv_CER/2,
recv_CEA/2,
make_caps/2]).
-include_lib("diameter/include/diameter.hrl").
-include("diameter_internal.hrl").
-include("diameter_gen_base_rfc3588.hrl").
-define(SUCCESS, 2001). %% DIAMETER_SUCCESS
-define(NOAPP, 5010). %% DIAMETER_NO_COMMON_APPLICATION
-define(NOSECURITY, 5017). %% DIAMETER_NO_COMMON_SECURITY
-define(NO_INBAND_SECURITY, 0).
-define(TLS, 1).
%% ===========================================================================
-type tried(T) :: {ok, T} | {error, {term(), list()}}.
-spec build_CER(#diameter_caps{})
-> tried(#diameter_base_CER{}).
build_CER(Caps) ->
try_it([fun bCER/1, Caps]).
-spec recv_CER(#diameter_base_CER{}, #diameter_service{})
-> tried({[diameter:'Unsigned32'()],
#diameter_caps{},
#diameter_base_CEA{}}).
recv_CER(CER, Svc) ->
try_it([fun rCER/2, CER, Svc]).
-spec recv_CEA(#diameter_base_CEA{}, #diameter_service{})
-> tried({[diameter:'Unsigned32'()],
[diameter:'Unsigned32'()],
#diameter_caps{}}).
recv_CEA(CEA, Svc) ->
try_it([fun rCEA/2, CEA, Svc]).
make_caps(Caps, Opts) ->
try_it([fun mk_caps/2, Caps, Opts]).
%% ===========================================================================
%% ===========================================================================
try_it([Fun | Args]) ->
try apply(Fun, Args) of
T -> {ok, T}
catch
throw: ?FAILURE(Reason) -> {error, Reason}
end.
%% mk_caps/2
mk_caps(Caps0, Opts) ->
{Caps, _} = lists:foldl(fun set_cap/2,
{Caps0, #diameter_caps{_ = false}},
Opts),
Caps.
-define(SC(K,F),
set_cap({K, Val}, {Caps, #diameter_caps{F = false} = C}) ->
{Caps#diameter_caps{F = cap(K, Val)}, C#diameter_caps{F = true}}).
?SC('Origin-Host', origin_host);
?SC('Origin-Realm', origin_realm);
?SC('Host-IP-Address', host_ip_address);
?SC('Vendor-Id', vendor_id);
?SC('Product-Name', product_name);
?SC('Origin-State-Id', origin_state_id);
?SC('Supported-Vendor-Id', supported_vendor_id);
?SC('Auth-Application-Id', auth_application_id);
?SC('Inband-Security-Id', inband_security_id);
?SC('Acct-Application-Id', acct_application_id);
?SC('Vendor-Specific-Application-Id', vendor_specific_application_id);
?SC('Firmware-Revision', firmware_revision);
set_cap({Key, _}, _) ->
?THROW({duplicate, Key}).
cap(K, V)
when K == 'Origin-Host';
K == 'Origin-Realm';
K == 'Vendor-Id';
K == 'Product-Name' ->
V;
cap('Host-IP-Address', Vs)
when is_list(Vs) ->
lists:map(fun ipaddr/1, Vs);
cap('Firmware-Revision', V) ->
[V];
cap(_, Vs)
when is_list(Vs) ->
Vs;
cap(K, V) ->
?THROW({invalid, K, V}).
ipaddr(A) ->
try
diameter_lib:ipaddr(A)
catch
error: {invalid_address, _} = T ->
?THROW(T)
end.
%% bCER/1
%%
%% Build a CER record to send to a remote peer.
%% Use the fact that diameter_caps has the same field names as CER.
bCER(#diameter_caps{} = Rec) ->
#diameter_base_CER{}
= list_to_tuple([diameter_base_CER | tl(tuple_to_list(Rec))]).
%% rCER/2
%%
%% Build a CEA record to send to a remote peer in response to an
%% incoming CER. RFC 3588 gives no guidance on what should be sent
%% here: should we advertise applications that the peer hasn't sent in
%% its CER (aside from the relay application) or not? If we send
%% applications that the peer hasn't advertised then the peer may have
%% to be aware of the possibility. If we don't then we just look like
%% a server that supports a subset (possibly) of what the client
%% advertised, so this feels like the path of least incompatibility.
%% However, the current draft standard (draft-ietf-dime-rfc3588bis-26,
%% expires 24 July 2011) says this in section 5.3, Capabilities
%% Exchange:
%%
%% The receiver of the Capabilities-Exchange-Request (CER) MUST
%% determine common applications by computing the intersection of its
%% own set of supported Application Id against all of the application
%% identifier AVPs (Auth-Application-Id, Acct-Application-Id and Vendor-
%% Specific-Application-Id) present in the CER. The value of the
%% Vendor-Id AVP in the Vendor-Specific-Application-Id MUST NOT be used
%% during computation. The sender of the Capabilities-Exchange-Answer
%% (CEA) SHOULD include all of its supported applications as a hint to
%% the receiver regarding all of its application capabilities.
%%
%% Both RFC and the draft also say this:
%%
%% The receiver only issues commands to its peers that have advertised
%% support for the Diameter application that defines the command. A
%% Diameter node MUST cache the supported applications in order to
%% ensure that unrecognized commands and/or AVPs are not unnecessarily
%% sent to a peer.
%%
%% That is, each side sends all of its capabilities and is responsible for
%% not sending commands that the peer doesn't support.
%% 6.10. Inband-Security-Id AVP
%%
%% NO_INBAND_SECURITY 0
%% This peer does not support TLS. This is the default value, if the
%% AVP is omitted.
%%
%% TLS 1
%% This node supports TLS security, as defined by [TLS].
rCER(CER, #diameter_service{capabilities = LCaps} = Svc) ->
#diameter_base_CEA{}
= CEA
= cea_from_cer(bCER(LCaps)),
RCaps = capx_to_caps(CER),
SApps = common_applications(LCaps, RCaps, Svc),
{SApps,
RCaps,
build_CEA(SApps,
LCaps,
RCaps,
CEA#diameter_base_CEA{'Result-Code' = ?SUCCESS})}.
build_CEA([], _, _, CEA) ->
CEA#diameter_base_CEA{'Result-Code' = ?NOAPP};
build_CEA(_, LCaps, RCaps, CEA) ->
case common_security(LCaps, RCaps) of
[] ->
CEA#diameter_base_CEA{'Result-Code' = ?NOSECURITY};
[_] = IS ->
CEA#diameter_base_CEA{'Inband-Security-Id' = IS}
end.
%% common_security/2
common_security(#diameter_caps{inband_security_id = LS},
#diameter_caps{inband_security_id = RS}) ->
cs(LS, RS).
%% Unspecified is equivalent to NO_INBAND_SECURITY.
cs([], RS) ->
cs([?NO_INBAND_SECURITY], RS);
cs(LS, []) ->
cs(LS, [?NO_INBAND_SECURITY]);
%% Agree on TLS if both parties support it. When sending CEA, this is
%% to ensure the peer is clear that we will be expecting a TLS
%% handshake since there is no ssl:maybe_accept that would allow the
%% peer to choose between TLS or not upon reception of our CEA. When
%% receiving CEA it deals with a server that isn't explicit about its choice.
%% TODO: Make the choice configurable.
cs(LS, RS) ->
Is = ordsets:to_list(ordsets:intersection(ordsets:from_list(LS),
ordsets:from_list(RS))),
case lists:member(?TLS, Is) of
true ->
[?TLS];
false when [] == Is ->
Is;
false ->
[hd(Is)] %% probably NO_INBAND_SECURITY
end.
%% The only two values defined by RFC 3588 are NO_INBAND_SECURITY and
%% TLS but don't enforce this. In theory this allows some other
%% security mechanism we don't have to know about, although in
%% practice something there may be a need for more synchronization
%% than notification by way of an event subscription offers.
%% cea_from_cer/1
%% CER is a subset of CEA, the latter adding Result-Code and a few
%% more AVP's.
cea_from_cer(#diameter_base_CER{} = CER) ->
lists:foldl(fun(F,A) -> to_cea(CER, F, A) end,
#diameter_base_CEA{},
record_info(fields, diameter_base_CER)).
to_cea(CER, Field, CEA) ->
try ?BASE:'#get-'(Field, CER) of
V -> ?BASE:'#set-'({Field, V}, CEA)
catch
error: _ -> CEA
end.
%% rCEA/2
rCEA(CEA, #diameter_service{capabilities = LCaps} = Svc) ->
RCaps = capx_to_caps(CEA),
SApps = common_applications(LCaps, RCaps, Svc),
IS = common_security(LCaps, RCaps),
{SApps, IS, RCaps}.
%% capx_to_caps/1
capx_to_caps(#diameter_base_CEA{'Origin-Host' = OH,
'Origin-Realm' = OR,
'Host-IP-Address' = IP,
'Vendor-Id' = VId,
'Product-Name' = PN,
'Origin-State-Id' = OSI,
'Supported-Vendor-Id' = SV,
'Auth-Application-Id' = Auth,
'Inband-Security-Id' = IS,
'Acct-Application-Id' = Acct,
'Vendor-Specific-Application-Id' = VSA,
'Firmware-Revision' = FR,
'AVP' = X}) ->
#diameter_caps{origin_host = OH,
origin_realm = OR,
vendor_id = VId,
product_name = PN,
origin_state_id = OSI,
host_ip_address = IP,
supported_vendor_id = SV,
auth_application_id = Auth,
inband_security_id = IS,
acct_application_id = Acct,
vendor_specific_application_id = VSA,
firmware_revision = FR,
avp = X};
capx_to_caps(#diameter_base_CER{} = CER) ->
capx_to_caps(cea_from_cer(CER)).
%% ---------------------------------------------------------------------------
%% ---------------------------------------------------------------------------
%% common_applications/3
%%
%% Identify the (local) applications to be supported on the connection
%% in question.
common_applications(LCaps, RCaps, #diameter_service{applications = Apps}) ->
LA = app_union(LCaps),
RA = app_union(RCaps),
lists:foldl(fun(I,A) -> ca(I, Apps, RA, A) end, [], LA).
ca(Id, Apps, RA, Acc) ->
Relay = lists:member(?APP_ID_RELAY, RA),
#diameter_app{alias = Alias} = find_app(Id, Apps),
tcons(Relay %% peer is a relay
orelse ?APP_ID_RELAY == Id %% we're a relay
orelse lists:member(Id, RA), %% app is supported by the peer
Id,
Alias,
Acc).
%% 5.3 of the RFC states that a peer advertising itself as a relay must
%% be interpreted as having common applications.
%% Extract the list of all application identifiers from Auth-Application-Id,
%% Acct-Application-Id and Vendor-Specific-Application-Id.
app_union(#diameter_caps{auth_application_id = U,
acct_application_id = C,
vendor_specific_application_id = V}) ->
set_list(U ++ C ++ lists:flatmap(fun vsa_apps/1, V)).
vsa_apps(#'diameter_base_Vendor-Specific-Application-Id'
{'Auth-Application-Id' = U,
'Acct-Application-Id' = C}) ->
U ++ C;
vsa_apps(L) ->
Rec = ?BASE:'#new-'('diameter_base_Vendor-Specific-Application-Id', L),
vsa_apps(Rec).
%% It's a configuration error for a locally advertised application not
%% to be represented in Apps. Don't just match on lists:keyfind/3 in
%% order to generate a more helpful error.
find_app(Id, Apps) ->
case lists:keyfind(Id, #diameter_app.id, Apps) of
#diameter_app{} = A ->
A;
false ->
?THROW({app_not_configured, Id})
end.
set_list(L) ->
sets:to_list(sets:from_list(L)).
tcons(true, K, V, Acc) ->
[{K,V} | Acc];
tcons(false, _, _, Acc) ->
Acc.
