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Simplify obfuscated handshake parsing

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Сергей Прохоров 2018-10-03 22:04:15 +02:00
parent 5fd3987e0a
commit 9b11341ffd
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GPG key ID: 1C570244E4EF3337
1 changed files with 8 additions and 10 deletions
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18
src/mtp_obfuscated.erl
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@ -66,17 +66,15 @@ from_header(Header, Secret) when byte_size(Header) == 64 ->
{DecKey, DecIV} = init_up_decrypt(Header, Secret),
St = new(EncKey, EncIV, DecKey, DecIV),
{<<_:56/binary, Bin1:8/binary, _/binary>>, St1} = decrypt(Header, St),
<<HeaderPart:56/binary, _/binary>> = Header,
NewHeader = <<HeaderPart/binary, Bin1/binary>>,
case NewHeader of
<<_:56/binary, 16#ef, 16#ef, 16#ef, 16#ef, _/binary>> ->
DcId = get_dc(NewHeader),
case Bin1 of
<<16#ef, 16#ef, 16#ef, 16#ef, _/binary>> ->
DcId = get_dc(Bin1),
{ok, DcId, mtp_abridged, St1};
<<_:56/binary, 16#ee, 16#ee, 16#ee, 16#ee, _/binary>> ->
DcId = get_dc(NewHeader),
<<16#ee, 16#ee, 16#ee, 16#ee, _/binary>> ->
DcId = get_dc(Bin1),
{ok, DcId, mtp_intermediate, St1};
<<_:56/binary, 16#dd, 16#dd, 16#dd, 16#dd, _/binary>> ->
DcId = get_dc(NewHeader),
<<16#dd, 16#dd, 16#dd, 16#dd, _/binary>> ->
DcId = get_dc(Bin1),
{ok, DcId, mtp_secure, St1};
_ ->
metric:count_inc([?APP, protocol_error, total], 1, #{labels => [unknown]}),
@ -96,7 +94,7 @@ init_up_decrypt(Bin, Secret) ->
KeyHash = crypto:hash('sha256', <<Key/binary, Secret/binary>>),
{KeyHash, IV}.
get_dc(<<_:60/binary, DcId:16/signed-little-integer, _/binary>>) ->
get_dc(<<_:4/binary, DcId:16/signed-little-integer, _/binary>>) ->
DcId.