On Sun, Sep 27, 2020 at 03:54:47PM +0200, Pablo Neira Ayuso wrote: > On Sat, Sep 26, 2020 at 03:10:24PM -0400, sean darcy wrote: > > nftables-0.9.6 > > > > I'm running a VOIP server. There are lots of script kiddies who will bang > > away with 10/sec SIP INVITES or REGISTERS . > > > > In iptables you can match on the string: > > > > -A SIP -i eth0 -p udp -m udp --dport 5060 -m string --string "INVITE" > > --algo bm --from 23 --to 28 -m comment --comment "Catch SIP INVITEs" -j > > SIPINVITE > > > > -A SIP -i eth0 -p udp -m udp --dport 5060 -m string --string "REGISTER" > > --algo bm --from 23 --to 30 -m comment --comment "Catch SIP REGISTERs" -j > > SIPREGISTER > > > > I'm looking at RAW to do the same: > > nft add rule x y udp dport 5060 @th,64,48 0x494e56495445 counter > > @th => transport header > 64 => from bit number 64 (8 bytes after the UDP header) > 48 => extract 48 bits (6 bytes for INVITE) @th,offset,length where offset and length are expressed in bits.
