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I recently posted a StackOverflow bounty related to figuring out whether it is Wireshark, Firefox or just the data sample that is wrong, judging by the fact that latest Wireshark cannot dissect it. This is a continuation of the question.

Assuming that the bounty linked above is correct, here is the full SYN_STREAM SPDY packet that Wireshark cannot dissect:

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

According to Wireshark, the compressed header should start at "783f". Unfortunately, I cannot decompress it:

$ python
Python 2.7.8 (default, Nov 10 2014, 08:19:18) 
[GCC 4.9.2 20141101 (Red Hat 4.9.2-1)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import zlib
>>> header = "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".decode('hex')
>>> zlib.decompress(header)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
zlib.error: Error 2 while decompressing data

Is it actually zlib? How can I prove it?

0
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I managed to decompress it in Python by specifying the decompression dictionary:

#!/usr/bin/python3

import zlib
import base64

header = ("783fe3c6a7c2003b01c4fe00000009000000073a6d6574686f"
"6400000003474554000000053a70617468000000012f000000083a76657273696f6e000000084"
"85454502f312e31000000053a686f73740000000d3139322e3136382e302e313734000000073a"
"736368656d650000000568747470730000000a757365722d6167656e74000000414d6f7a696c6"
"c612f352e30202857696e646f7773204e5420352e313b2072763a33302e3029204765636b6f2f"
"32303130303130312046697265666f782f33302e30000000066163636570740000003f7465787"
"42f68746d6c2c6170706c69636174696f6e2f7868746d6c2b786d6c2c6170706c69636174696f"
"6e2f786d6c3b713d302e392c2a2f2a3b713d302e380000000f6163636570742d6c616e6775616"
"7650000000e656e2d55532c656e3b713d302e3500000003646e740000000131000000ffff")

zdict = base64.b16decode("000000076F7074696F6E730000000468656164000000"
"04706F7374000000037075740000000664656C65746500000005747261636500000006"
"6163636570740000000E6163636570742D636861727365740000000F6163636570742D"
"656E636F64696E670000000F6163636570742D6C616E67756167650000000D61636365"
"70742D72616E6765730000000361676500000005616C6C6F770000000D617574686F72"
"697A6174696F6E0000000D63616368652D636F6E74726F6C0000000A636F6E6E656374"
"696F6E0000000C636F6E74656E742D6261736500000010636F6E74656E742D656E636F"
"64696E6700000010636F6E74656E742D6C616E67756167650000000E636F6E74656E74"
"2D6C656E67746800000010636F6E74656E742D6C6F636174696F6E0000000B636F6E74"
"656E742D6D64350000000D636F6E74656E742D72616E67650000000C636F6E74656E74"
"2D74797065000000046461746500000004657461670000000665787065637400000007"
"657870697265730000000466726F6D00000004686F73740000000869662D6D61746368"
"0000001169662D6D6F6469666965642D73696E63650000000D69662D6E6F6E652D6D61"
"7463680000000869662D72616E67650000001369662D756E6D6F6469666965642D7369"
"6E63650000000D6C6173742D6D6F646966696564000000086C6F636174696F6E000000"
"0C6D61782D666F72776172647300000006707261676D610000001270726F78792D6175"
"7468656E7469636174650000001370726F78792D617574686F72697A6174696F6E0000"
"000572616E676500000007726566657265720000000B72657472792D61667465720000"
"000673657276657200000002746500000007747261696C6572000000117472616E7366"
"65722D656E636F64696E6700000007757067726164650000000A757365722D6167656E"
"74000000047661727900000003766961000000077761726E696E67000000107777772D"
"61757468656E746963617465000000066D6574686F6400000003676574000000067374"
"6174757300000006323030204F4B0000000776657273696F6E00000008485454502F31"
"2E310000000375726C000000067075626C69630000000A7365742D636F6F6B69650000"
"000A6B6565702D616C697665000000066F726967696E31303031303132303132303232"
"3035323036333030333032333033333034333035333036333037343032343035343036"
"3430373430383430393431303431313431323431333431343431353431363431373530"
"32353034353035323033204E6F6E2D417574686F726974617469766520496E666F726D"
"6174696F6E323034204E6F20436F6E74656E74333031204D6F766564205065726D616E"
"656E746C7934303020426164205265717565737434303120556E617574686F72697A65"
"6434303320466F7262696464656E343034204E6F7420466F756E6435303020496E7465"
"726E616C20536572766572204572726F72353031204E6F7420496D706C656D656E7465"
"64353033205365727669636520556E617661696C61626C654A616E20466562204D6172"
"20417072204D6179204A756E204A756C204175672053657074204F6374204E6F762044"
"65632030303A30303A3030204D6F6E2C205475652C205765642C205468752C20467269"
"2C205361742C2053756E2C20474D546368756E6B65642C746578742F68746D6C2C696D"
"6167652F706E672C696D6167652F6A70672C696D6167652F6769662C6170706C696361"
"74696F6E2F786D6C2C6170706C69636174696F6E2F7868746D6C2B786D6C2C74657874"
"2F706C61696E2C746578742F6A6176617363726970742C7075626C6963707269766174"
"656D61782D6167653D677A69702C6465666C6174652C73646368636861727365743D75"
"74662D38636861727365743D69736F2D383835392D312C7574662D2C2A2C656E713D30"
"2E")

header = base64.b16decode(header.upper())

z = zlib.decompressobj(zdict=zdict)
print(z.decompress(bytearray(header)))

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