Fix broken handling of default values for BIT STRINGs

For DER/PER/UPER, a value equal to the DEFAULT is not supposed to
be encoded.

BIT STRINGs values can be represented as Erlang terms in four
different ways: as an integer, as a list of zeroes and ones,
as a {Unused,Binary} tuple, or as an Erlang bitstring.

When encoding a BIT STRING, only certain representations of
BIT STRINGs values were recognized. All representations must
be recognized.

When decoding a DEFAULT value for a BIT STRING, the actual value
given in the decoding would be either an integer or a list
of zeroes and one (depending on how the literal was written in
the specification). We expect that the default value should be
in the same representation as any other BIT STRING value (i.e.
by default an Erlang bitstring, or a list if the 'legacy_bitstring'
option has been given, or as compact bitstring if 'compact_bitstring'
has been given).

1 files changed, 58 insertions, 33 deletions

diff --git a/lib/asn1/src/asn1rtt_check.erl b/lib/asn1/src/asn1rtt_check.erl
index e78b65a8fb..be4f9c8bff 100644
--- a/lib/asn1/src/asn1rtt_check.erl
+++ b/lib/asn1/src/asn1rtt_check.erl
@@ -20,7 +20,7 @@
 
 -export([check_bool/2,
 	 check_int/3,
-	 check_bitstring/3,
+	 check_bitstring/2,check_named_bitstring/3,
 	 check_octetstring/2,
 	 check_null/2,
 	 check_objectidentifier/2,
@@ -50,31 +50,54 @@ check_int(DefValue, Value, NNL) when is_atom(Value) ->
 check_int(DefaultValue, _Value, _) ->
     throw({error,DefaultValue}).
 
-%% Two equal lists or integers
-check_bitstring(_, asn1_DEFAULT, _) ->
+%% check_bitstring(Default, UserBitstring) -> true|false
+%%  Default = bitstring()
+%%  UserBitstring = integeger() | list(0|1) | {Unused,binary()} | bitstring()
+check_bitstring(_, asn1_DEFAULT) ->
     true;
-check_bitstring(V, V, _) ->
-    true;
-%% Default value as a list of 1 and 0 and user value as an integer
-check_bitstring(L=[H|T], Int, _) when is_integer(Int), is_integer(H) ->
-    case bit_list_to_int(L, length(T)) of
-	Int -> true;
-	_ -> throw({error,L,Int})
+check_bitstring(DefVal, {Unused,Binary}) ->
+    %% User value in compact format.
+    Sz = bit_size(Binary) - Unused,
+    <<Val:Sz/bitstring,_:Unused>> = Binary,
+    check_bitstring(DefVal, Val);
+check_bitstring(DefVal, Val) when is_bitstring(Val) ->
+    case Val =:= DefVal of
+	false -> throw(error);
+	true -> true
     end;
-%% Default value as an integer, val as list
-check_bitstring(Int, Val, NBL) when is_integer(Int), is_list(Val) ->
-    BL = int_to_bit_list(Int, [], length(Val)),
-    check_bitstring(BL, Val, NBL);
+check_bitstring(Def, Val) when is_list(Val) ->
+    check_bitstring_list(Def, Val);
+check_bitstring(Def, Val) when is_integer(Val) ->
+    check_bitstring_integer(Def, Val).
+
+check_bitstring_list(<<H:1,T1/bitstring>>, [H|T2]) ->
+    check_bitstring_list(T1, T2);
+check_bitstring_list(<<>>, []) ->
+    true;
+check_bitstring_list(_, _) ->
+    throw(error).
+
+check_bitstring_integer(<<H:1,T1/bitstring>>, Int) when H =:= Int band 1 ->
+    check_bitstring_integer(T1, Int bsr 1);
+check_bitstring_integer(<<>>, 0) ->
+    true;
+check_bitstring_integer(_, _) ->
+    throw(error).
+
+check_named_bitstring(_, asn1_DEFAULT, _) ->
+    true;
+check_named_bitstring(V, V, _) ->
+    true;
 %% Default value and user value as lists of ones and zeros
-check_bitstring(L1=[H1|_T1], L2=[H2|_T2], NBL=[_H|_T]) when is_integer(H1), is_integer(H2) ->
+check_named_bitstring(L1=[H1|_T1], L2=[H2|_T2], NBL=[_H|_T]) when is_integer(H1), is_integer(H2) ->
     L2new = remove_trailing_zeros(L2),
-    check_bitstring(L1, L2new, NBL);
+    check_named_bitstring(L1, L2new, NBL);
 %% Default value as a list of 1 and 0 and user value as a list of atoms
-check_bitstring(L1=[H1|_T1], L2=[H2|_T2], NBL) when is_integer(H1), is_atom(H2) ->
+check_named_bitstring(L1=[H1|_T1], L2=[H2|_T2], NBL) when is_integer(H1), is_atom(H2) ->
     L3 = bit_list_to_nbl(L1, NBL, 0, []),
-    check_bitstring(L3, L2, NBL);
+    check_named_bitstring(L3, L2, NBL);
 %% Both default value and user value as a list of atoms
-check_bitstring(L1=[H1|T1], L2=[H2|_T2], _)
+check_named_bitstring(L1=[H1|T1], L2=[H2|_T2], _)
   when is_atom(H1), is_atom(H2), length(L1) =:= length(L2) ->
     case lists:member(H1, L2) of
 	true ->
@@ -82,27 +105,29 @@ check_bitstring(L1=[H1|T1], L2=[H2|_T2], _)
 	false -> throw({error,L2})
     end;
 %% Default value as a list of atoms and user value as a list of 1 and 0
-check_bitstring(L1=[H1|_T1], L2=[H2|_T2], NBL) when is_atom(H1), is_integer(H2) ->
+check_named_bitstring(L1=[H1|_T1], L2=[H2|_T2], NBL) when is_atom(H1), is_integer(H2) ->
     L3 = bit_list_to_nbl(L2, NBL, 0, []),
-    check_bitstring(L1, L3, NBL);
+    check_named_bitstring(L1, L3, NBL);
 %% User value in compact format
-check_bitstring(DefVal,CBS={_,_}, NBL) ->
+check_named_bitstring(DefVal,CBS={_,_}, NBL) ->
     NewVal = cbs_to_bit_list(CBS),
-    check_bitstring(DefVal, NewVal, NBL);
-check_bitstring(DV, V, _) ->
+    check_named_bitstring(DefVal, NewVal, NBL);
+%% User value as a binary
+check_named_bitstring(DefVal, CBS, NBL) when is_binary(CBS) ->
+    NewVal = cbs_to_bit_list({0,CBS}),
+    check_named_bitstring(DefVal, NewVal, NBL);
+%% User value as a bitstring
+check_named_bitstring(DefVal, CBS, NBL) when is_bitstring(CBS) ->
+    BitSize = bit_size(CBS),
+    Unused = 8 - (BitSize band 7),
+    NewVal = cbs_to_bit_list({Unused,<<CBS:BitSize/bits,0:Unused>>}),
+    check_named_bitstring(DefVal, NewVal, NBL);
+check_named_bitstring(DV, V, _) ->
     throw({error,DV,V}).
 
-
-bit_list_to_int([0|Bs], ShL)->
-    bit_list_to_int(Bs, ShL-1) + 0;
-bit_list_to_int([1|Bs], ShL) ->
-    bit_list_to_int(Bs, ShL-1) + (1 bsl ShL);
-bit_list_to_int([], _) ->
-    0.
-
 int_to_bit_list(0, Acc, 0) ->
     Acc;
-int_to_bit_list(Int, Acc, Len) ->
+int_to_bit_list(Int, Acc, Len) when Len > 0 ->
     int_to_bit_list(Int bsr 1, [Int band 1|Acc], Len - 1).
 
 bit_list_to_nbl([0|T], NBL, Pos, Acc) ->