[Snort-sigs] Snort 2.8.6 and gzip decoding functionality not working for me

L0rd Ch0de1m0rt l0rdch0de1m0rt at ...2420...
Tue May 4 15:40:03 EDT 2010

Hello.  I am experimenting with snort v2.8.6 and hope to benefit from
its gzip decoding capabilities.  However, I have been unsuccessful so
far in getting it to work.  I am fetching a javascript file from
google and clearly it is encoding it using gzip.  This rule alerts me:

alert tcp any any -> any any (msg:"gzip encoding detected from
server"; flow:established,from_server; content:"|0d
0a|Content-Encoding: gzip|0d 0a|"; nocase; classtype:attempted-user;
sid:3141591; rev:1;)

BUT this rule does not alert when it is clearly in the gzip decoded data:

alert tcp any any -> any any (msg:"detected on gzip decoded data from
Google"; flow:established,from_server; content:"google.isOpera=false";
nocase; classtype:attempted-user; sid:3141592; rev:1;)

I am using the defaults for the gzip portion of the http_inspect
preprocessor and the content trying to be matched
(google.isOpera=false) is in the first few hundred bytes of the data.
Here is my snort.conf http_inspect details:

preprocessor http_inspect: global iis_unicode_map unicode.map 1252
preprocessor http_inspect_server: server default \
   apache_whitespace no \
   ascii no \
        bare_byte no \
        chunk_length 500000 \
   server_flow_depth 0 \
   client_flow_depth 0 \
   post_depth 65495 \
        directory no \
        double_decode no \
        iis_backslash no \
        iis_delimiter no \
        iis_unicode no \
        multi_slash no \
        non_strict \
        oversize_dir_length 500 \
        ports { 80 1220 2301 3128 7777 7779 8000 8008 8028 8080 8180
8888 9999 } \
        u_encode yes \
        non_rfc_char { 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 } \
        webroot no \
        extended_response_inspection \

I configured snort with --enable-zlib before I compiled and I get this
on snort startup:

Using ZLIB version:

What am I doing wrong here?  Thanks for any help.


-L0rd Ch0de1m0rt

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