snmp_pdus.erl

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chk_msg_max_size(MMS) -> exit({bad_msg_max_size, MMS}).
    
chk_msg_sec_model(MsgSecurityModel) when MsgSecurityModel >= 0,
					 MsgSecurityModel =< 2147483647 -> ok;
chk_msg_sec_model(MsgSecurityModel) -> 
    exit({bad_msg_sec_model, MsgSecurityModel}).
    
%%----------------------------------------------------------------------
%% Code copied from the original ASN.1 compiler written by 
%% [e-mail]
%%----------------------------------------------------------------------

%%----------------------------------------------------------------------
%% Returns: {Len, Tail}
%%----------------------------------------------------------------------
dec_len([128|_Tail]) ->
    %% indefinite form - not allowed in SNMP
    exit({asn1_error, indefinite_length});

dec_len([Hd|Tl]) when Hd >= 0 ->
    %% definite form
    if
	Hd < 128 -> % 8th bit is cleared
	    %% Short form (actually, we can remove this test, since snmp_pdus
	    %% performs this test _before_ calling this function)
	    {Hd,Tl};
	true ->
	    %% Long form
	    No = Hd band 127,  % clear 8th bit
	    {DigList,Rest} = head(No,Tl),
	    Size = dec_integer_len(DigList),
	    {Size,Rest}
    end.

dec_integer_len([D]) ->
    D;
dec_integer_len([A,B]) ->
    (A bsl 8) bor B;
dec_integer_len([A,B,C]) ->
    (A bsl 16) bor (B bsl 8) bor C;
%% More than 3 elements for length => either *very* long packet
%% (which we don't handle), or the length is encoded with more octets
%% than necessary (in which case the first octet must be 0).
dec_integer_len([0 | T]) ->
    dec_integer_len(T).

%%-----------------------------------------------------------------
%% head(N, List) -> {List1, List2}
%%   List == List1 ++ List2
%%   length(List1) == N
%%-----------------------------------------------------------------
head(L,List) ->
    head(L,List,[]).

head(0,L,Res) ->
    {lists:reverse(Res),L};

head(Int,[H|Tail],Res) ->
    head(Int-1,Tail,[H|Res]);
head(Int, [], _Res) ->
    exit({asn1_error, {bad_length, Int}}).

%%%----------------------------------------------------------------------
%%% ENCODING ENCODING ENCODING ENCODING ENCODING ENCODING ENCODING ENCODING 
%%%----------------------------------------------------------------------

enc_message(#message{version = Ver, vsn_hdr = VsnHdr, data = Data}) ->
    VerBytes = enc_version(Ver),
    Bytes = 
	case Ver of
	    'version-3' ->
		V3HeaderBytes = enc_v3_header(VsnHdr),
		DataBytes = enc_scoped_pdu(Data),
		V3HeaderBytes ++ DataBytes;
	    _ ->
		ComBytes = enc_community(VsnHdr),
		DataBytes = enc_pdu(Data),
		ComBytes ++ DataBytes
	end,
    Bytes2 = VerBytes ++ Bytes,
    Len = elength(length(Bytes2)),
    [48 | Len] ++ Bytes2.

enc_message_only(#message{version = Ver, vsn_hdr = VsnHdr, data = DataBytes}) ->
    VerBytes = enc_version(Ver),
    Bytes = 
	case Ver of
	    'version-3' ->
		V3HeaderBytes = enc_v3_header(VsnHdr),
		V3HeaderBytes ++ DataBytes;
	    _ ->
		ComBytes = enc_community(VsnHdr),
		ComBytes ++ DataBytes
	end,
    Bytes2 = VerBytes ++ Bytes,
    Len = elength(length(Bytes2)),
    [48 | Len] ++ Bytes2.

enc_version('version-1') ->
    [2,1,0];
enc_version('version-2') ->
    [2,1,1];
enc_version('version-3') ->
    [2,1,3].

enc_community(Com) ->
    enc_oct_str_tag(Com).

enc_v3_header(#v3_hdr{msgID = MsgID,
		      msgMaxSize = MsgMaxSize,
		      msgFlags = MsgFlags,
		      msgSecurityModel = MsgSecurityModel,
		      msgSecurityParameters = MsgSecurityParameters}) ->
    Bytes = lists:append([enc_integer_tag(MsgID),
			  enc_integer_tag(MsgMaxSize),
			  enc_oct_str_tag(MsgFlags),
			  enc_integer_tag(MsgSecurityModel)]),
    Len = elength(length(Bytes)),
    lists:append([[48 | Len], Bytes, enc_oct_str_tag(MsgSecurityParameters)]).
    
enc_scoped_pdu(#scopedPdu{contextEngineID = ContextEngineID,
			  contextName = ContextName,
			  data = Data}) ->
    Bytes = lists:append([enc_oct_str_tag(ContextEngineID),
			  enc_oct_str_tag(ContextName),
			  enc_pdu(Data)]),
    Len = elength(length(Bytes)),
    [48 | Len] ++ Bytes.


enc_pdu(PDU) when PDU#pdu.type == 'get-request' ->
    enc_pdu(160, PDU);
enc_pdu(PDU) when PDU#pdu.type == 'get-next-request' ->
    enc_pdu(161, PDU);
enc_pdu(PDU) when PDU#pdu.type == 'get-response' ->
    enc_pdu(162, PDU);
enc_pdu(PDU) when PDU#pdu.type == 'set-request' ->
    enc_pdu(163, PDU);
enc_pdu(PDU) when PDU#pdu.type == 'get-bulk-request' ->
    enc_pdu(165, PDU);
enc_pdu(PDU) when PDU#pdu.type == 'inform-request' ->
    enc_pdu(166, PDU);
enc_pdu(PDU) when PDU#pdu.type == 'snmpv2-trap' ->
    enc_pdu(167, PDU);
enc_pdu(PDU) when PDU#pdu.type == report ->
    enc_pdu(168, PDU);
enc_pdu(TrapPDU) when record(TrapPDU, trappdu) ->
    enc_Trap(TrapPDU).


enc_pdu(Tag,PDU) ->
    Bytes2 = enc_pdu2(PDU),
    Len2 = elength(length(Bytes2)),
    lists:append([Tag | Len2], Bytes2).

enc_pdu2(#pdu{type = Type, request_id = ReqId, error_index = ErrIndex,
	      error_status = ErrStat, varbinds = VBs}) ->
    ReqBytes = enc_integer_tag(ReqId),
    Val = err_val(ErrStat,Type),
    ErrStatBytes = enc_integer_tag(Val),
    ErrIndexBytes = enc_integer_tag(ErrIndex),
    VBsBytes = enc_VarBindList(VBs),
    lists:append([ReqBytes, ErrStatBytes, ErrIndexBytes, VBsBytes]).

enc_usm_security_parameters(
  #usmSecurityParameters{msgAuthoritativeEngineID = MsgAuthEngineID,
			 msgAuthoritativeEngineBoots = MsgAuthEngineBoots,
			 msgAuthoritativeEngineTime = MsgAuthEngineTime,
			 msgUserName = MsgUserName,
			 msgAuthenticationParameters = MsgAuthParams,
			 msgPrivacyParameters = MsgPrivParams}) ->
    Bytes1 = enc_oct_str_tag(MsgAuthEngineID),
    Bytes2 = enc_integer_tag(MsgAuthEngineBoots),
    Bytes3 = enc_integer_tag(MsgAuthEngineTime),
    Bytes4 = enc_oct_str_tag(MsgUserName),
    Bytes5 = enc_oct_str_tag(MsgAuthParams),
    Bytes6 = enc_oct_str_tag(MsgPrivParams),
    Bytes7 = lists:append([Bytes1, Bytes2, Bytes3, Bytes4, Bytes5, Bytes6]),
    Len = elength(length(Bytes7)),
    [48 | Len] ++ Bytes7.

err_val(Int,'get-bulk-request') when integer(Int) -> Int;
err_val(ErrStat, _) ->
    {value, {_ErrStat, Val}} = lists:keysearch(ErrStat, 1, errMsgs()),
    Val.

errMsgs() ->
    [{noError,0},{tooBig,1},{noSuchName,2},
     {badValue,3},{readOnly,4},{genErr,5},
     %% v2
     {noAccess,6},{wrongType,7},{wrongLength,8},{wrongEncoding,9},
     {wrongValue,10},{noCreation,11},{inconsistentValue,12},
     {resourceUnavailable,13},{commitFailed,14},{undoFailed,15},
     {authorizationError,16},{notWritable,17},{inconsistentName,18}].

enc_VarBindList(EncodedVBs) when integer(hd(EncodedVBs)) ->
    Len1 = elength(length(EncodedVBs)),
    lists:append([48 | Len1],EncodedVBs);
enc_VarBindList(VBs) ->
    Bytes1 = lists:append(lists:map(fun enc_varbind/1, VBs)),
    Len1 = elength(length(Bytes1)),
    lists:append([48 | Len1],Bytes1).

enc_varbind(Varbind) ->
    Bytes1 = enc_VarBind_attributes(Varbind),
    Len1 = elength(length(Bytes1)),
    lists:append([48 | Len1],Bytes1).


enc_VarBind_attributes(#varbind{oid = Oid, variabletype = Type,value = Val}) ->
    OidBytes = enc_oid_tag(Oid),
    ValueBytes = enc_value(Type, Val),
    lists:append(OidBytes, ValueBytes).

enc_value('INTEGER',Val) ->
    enc_integer_tag(Val);
enc_value('OCTET STRING', Val) ->
    enc_oct_str_tag(Val);
enc_value('BITS', Val) ->
    enc_oct_str_tag(bits_to_str(Val));
enc_value('OBJECT IDENTIFIER', Val) ->
    enc_oid_tag(Val);
enc_value('IpAddress',Val) ->
    Bytes2 = enc_oct_str_notag(Val),
    Len2 = elength(length(Bytes2)),
    lists:append([64 | Len2],Bytes2);
enc_value('Opaque', Val) ->
    Bytes2 = enc_oct_str_notag(Val),
    Len2 = elength(length(Bytes2)),
    lists:append([68 | Len2],Bytes2);
enc_value(_Type, noSuchObject) ->
    [128,0];
enc_value(_Type, noSuchInstance) ->
    [129,0];
enc_value(_Type, endOfMibView) ->
    [130,0];
enc_value('NULL', _Val) ->
    [5,0];
enc_value(Type, Val) ->
    Bytes2 = enc_integer_notag(Val),
    Len2 = elength(length(Bytes2)),
    lists:append([enc_val_tag(Type,Val) | Len2],Bytes2).

enc_val_tag('Counter32',Val) when Val >= 0, Val =< 4294967295 ->
    65;
enc_val_tag('Unsigned32', Val) when Val >= 0, Val =< 4294967295 ->
    66;
enc_val_tag('TimeTicks', Val) when Val >= 0, Val =< 4294967295 ->
    67;
enc_val_tag('Counter64', Val) when Val >= 0, Val =< 18446744073709551615 ->
    70.

%%----------------------------------------------------------------------
%% Impl according to RFC1906, section 8
%% For example: the number 1010 0000 (=160)   0100 0001 (=65) is represented as
%% the octet string: 1000 0010, 0000 0101 (=[130,5])
%%----------------------------------------------------------------------
bits_to_str(0) -> "";
bits_to_str(Int) ->
    [rev_int8(Int band 255) | bits_to_str(Int div 256)].

rev_int8(Val) ->
    rev_int(Val,0,1,128).

rev_int(_Val,Res,256,0) -> Res;
rev_int(Val,Res,OldBit,NewBit) when Val band OldBit =/= 0 ->
    rev_int(Val,Res+NewBit,OldBit*2,NewBit div 2);
rev_int(Val,Res,OldBit,NewBit) ->
    rev_int(Val,Res,OldBit*2,NewBit div 2).

octet_str_to_bits(Str) ->
    octet_str_to_bits(Str,1).

octet_str_to_bits("",_) -> 0;
octet_str_to_bits([Byte|Bytes],Mul) ->
    Mul*rev_int8(Byte)+octet_str_to_bits(Bytes,Mul*256).
    

enc_Trap(TrapPdu) when record(TrapPdu, trappdu) ->
    Bytes1 = enc_trap_data(TrapPdu),
    Len1 = elength(length(Bytes1)),
    lists:append([164 | Len1],Bytes1).


enc_trap_data(#trappdu{enterprise = Enterprise,
		       agent_addr = AgentAddr,
		       generic_trap = GenericTrap,
		       specific_trap = SpecificTrap,
		       time_stamp = TimeStamp,
		       varbinds = VBs}) ->
    L1 = enc_oid_tag(Enterprise),
    L2 = enc_value('IpAddress', AgentAddr),
    L3 = enc_integer_tag(GenericTrap),
    L4 = enc_integer_tag(SpecificTrap),
    L5 = enc_value('TimeTicks', TimeStamp),
    L6 = enc_VarBindList(VBs),
    lists:append([L1,L2,L3,L4,L5,L6]).

enc_oid_tag([E1,E2|RestOid]) when E1 * 40 + E2 =< 255 ->
    Head = 40*E1 + E2,  % weird
    Res = e_object_elements(RestOid, []),
    lists:append([6 | elength(length(Res) + 1)],[Head|Res]).

e_object_elements([Num | T], Res)  ->
    e_object_elements(T, lists:append(e_object_element(Num),Res));

e_object_elements([], Res) -> lists:reverse(Res).

%%----------------------------------------------------------------------
%% The reversed encoding for an oid-element
%%----------------------------------------------------------------------
e_object_element(Num) when Num > 0 ->
    [Last|T] = e_object_element2(Num),
    [Last-128|T];
e_object_element(0) -> [0].

e_object_element2(Num) when Num > 0 ->
    Byte = (Num rem 128),
    [128+Byte | e_object_element2((Num-Byte) div 128)];
e_object_element2(0) -> [].

enc_integer_tag(Val) when Val >= 0 ->  %% stdcase positive ints
    Bytes = eint(Val,[]),
    [2 | elength(length(Bytes))] ++ Bytes;

enc_integer_tag(Val) ->  %% It's a negative number
    Bytes = enint(Val,[]),
    [2 | elength(length(Bytes))] ++ Bytes.

enc_integer_notag(Val) when Val >= 0 ->  %% stdcase positive ints
    eint(Val,[]);
    
enc_integer_notag(Val) -> %% It's a negative number
    enint(Val,[]).

eint(0, [B|Acc]) when B < 128 ->
    [B|Acc];
eint(N, Acc) ->
    eint(N bsr 8, [N band 16#ff| Acc]).

enint(-1, [B1|T]) when B1 > 127 ->
    [B1|T];
enint(N, Acc) ->
    enint(N bsr 8, [N band 16#ff|Acc]).
 
enc_oct_str_tag(OStr) when list(OStr) ->
    lists:append([4|elength(length(OStr))],OStr);
enc_oct_str_tag(OBin) ->
    [4,elength(size(OBin)),OBin].


enc_oct_str_notag(OStr) -> OStr.

%%-----------------------------------------------------------------
%% Always use definite form
%%-----------------------------------------------------------------
%% Short
elength(L) when L < 127 ->
    [L];

%% 3 cases of long form
elength(L) when L =< 16#FF ->
    [2#10000001,L];

elength(L) when L  =< 16#FFFF ->
    [2#10000010,(L bsr 8),(L band 16#FF)];

elength(L) when L =< 16#7FFFFF ->
    [2#10000011,(L bsr 16),((L band 16#FF00) bsr 8), (L band 16#FF)].