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+%%
+%% %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_types.hrl").
+-include("diameter_gen_base_rfc3588.hrl").
+
+-define(SUCCESS, ?'DIAMETER_BASE_RESULT-CODE_DIAMETER_SUCCESS').
+-define(NOAPP, ?'DIAMETER_BASE_RESULT-CODE_DIAMETER_NO_COMMON_APPLICATION').
+-define(NOSECURITY, ?'DIAMETER_BASE_RESULT-CODE_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({['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({['Unsigned32'()], ['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, Args}}
+ 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})}.
+
+%% TODO: 5.3 of RFC 3588 says we MUST return DIAMETER_NO_COMMON_APPLICATION
+%% in the CEA and SHOULD disconnect the transport. However, we have
+%% no way to guarantee the send before disconnecting.
+
+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(#diameter_base_CEA{'Result-Code' = RC}
+ = CEA,
+ #diameter_service{capabilities = LCaps}
+ = Svc) ->
+ RC == ?SUCCESS orelse ?THROW({'Result-Code', RC}),
+
+ RCaps = capx_to_caps(CEA),
+ SApps = common_applications(LCaps, RCaps, Svc),
+
+ [] == SApps andalso ?THROW(no_common_applications),
+
+ IS = common_security(LCaps, RCaps),
+
+ [] == IS andalso ?THROW(no_common_security),
+
+ {SApps, IS, RCaps};
+
+rCEA(CEA, _Svc) ->
+ ?THROW({invalid, CEA}).
+
+%% 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.
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