42 lines
1.2 KiB
Plaintext
42 lines
1.2 KiB
Plaintext
****************************************
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IMPORTANT NOTICE
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****************************************
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1)
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If you're using this software and have a rule which ends like this:
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flags S
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(for TCP), then to make it totally effective, you need to change it to appear
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as follows:
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flags S/SA
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The problem is that the old code would compare all the TCP flags against the
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rule (which just has "S") to see if that matched exactly. It is very possible
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for this to not be the case and in these cases, the rule would fail to match
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a 'valid' TCP SYN packet.
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Why does it need to be "S/SA" and not "S/S" ?
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"S/S" will match the SYN-ACK as well the SYN.
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By defalt, "flags S" will now be converted to "flags S/AUPRFS".
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If you have any queries regarding this, see the examples and ipf(4).
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If you still have a query or suggestion, please email me.
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2)
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If a filter rule used, in combination port comparisons and the flags
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keywords, a "short" TCP packet, if not explicitly blocked high up in
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the list of packets, would actually get matched even though it would
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otherwise not have been (due to the ports not). This behaviour has
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subsequently been fixed.
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Darren
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darrenr@cyber.com.au
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****************************************
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