Be prepared for broken UTF-8

Author: RaimoNiskanen

lib/kernel/src/inet_dns.erl

@@ -787,7 +787,11 @@ decode_characters(Data, Encoding) ->
     ?MATCH_ELSE_DECODE_ERROR(
        Data,
        <<Len,Bin:Len/binary,Rest/binary>>,
-       {Rest,unicode:characters_to_list(Bin, Encoding)}).
+       ?MATCH_ELSE_DECODE_ERROR(
+          unicode:characters_to_list(Bin, Encoding),
+          String,
+          is_list(String),
+          {Rest,String})).
 
 %% One domain name only, there must be nothing after
 %%
@@ -974,11 +978,15 @@ encode_data(Comp, Pos, ?S_NAPTR, Data) ->
     B0 = <<Order:16,Preference:16>>,
     B1 = encode_string(B0, iolist_to_binary(Flags)),
     B2 = encode_string(B1, iolist_to_binary(Services)),
-    B3 = encode_string(B2, unicode:characters_to_binary(Regexp,
-							unicode, utf8)),
-    %% Bypass name compression (RFC 2915: section 2)
-    {B,_} = encode_name(B3, gb_trees:empty(), Pos+byte_size(B3), Replacement),
-    {B,Comp};
+    case unicode:characters_to_binary(Regexp, unicode, utf8) of
+        EncRegexp when is_binary(EncRegexp) ->
+            B3 = encode_string(B2, EncRegexp),
+            %% Bypass name compression (RFC 2915: section 2)
+            {B,_} =
+                encode_name(
+                  B3, gb_trees:empty(), Pos+byte_size(B3), Replacement),
+            {B,Comp}
+    end;
 encode_data(Comp, _, ?S_TXT, Data) -> {encode_txt(Data),Comp};
 encode_data(Comp, _, ?S_SPF, Data) -> {encode_txt(Data),Comp};
 encode_data(Comp, _, ?S_URI, Data) ->

lib/kernel/test/inet_res_SUITE.erl

@@ -2004,6 +2004,34 @@ bad_decode_2(Config) when is_list(Config) ->
                   id = ID, qr = QR, opcode = 'query', rd = 1 },
            qdlist = [#dns_query{ domain = "", type = 'a', class = 'in'}] },
     {error, formerr} = inet_dns:decode_reply(Buffer, Q, false),
+
+    %% NAPTR with broken UTF-8
+
+    %% Encode should fail
+    Replacement = "Replacement",
+    ReplBin = list_to_binary(Replacement),
+    RR1_NAPTR =
+        #dns_rr{
+           type = 'naptr',
+           data = {100,10,"Flags","Services",<<"Regex",255>>,Replacement}},
+    try inet_dns:encode(Q#dns_rec{ anlist = [RR1_NAPTR] }) of
+        Result -> error({should_not_encode, Result})
+    catch error : _ -> ok
+    end,
+
+    %% Decode should return proper error
+    RR_NAPTR =
+        #dns_rr{
+           type = 'naptr',
+           data = {100,10,"Flags","Services","Regexp",Replacement}},
+    Buffer_NAPTR = inet_dns:encode(Q#dns_rec{ anlist = [RR_NAPTR] }),
+    Tail_NAPTR = << (byte_size(ReplBin)), ReplBin/binary, 0 >>,
+    << Start_NAPTR:(byte_size(Buffer_NAPTR)-byte_size(Tail_NAPTR)-1)/binary,
+       _,
+       Tail_NAPTR/binary >> = Buffer_NAPTR,
+    {error,formerr} =
+        inet_dns:decode(<< Start_NAPTR/binary, 255, Tail_NAPTR/binary >>),
+
     ok.
 
 %% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%