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Re: squid hardening - weird behaviour

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devzero@xxxxxx wrote:
weird, i don`t see any listeing socket with squidclient - i would have expected 3128 and 34810 here !?
So did I. Mine shows them. Should have 0.0.0.0.0 (last .0 is port). Maybe it is slightly different in 2.x than 3.0 in this regard.

yes, seems so.
i updated to latest release and now i see

Active file descriptors:
File Type   Tout Nread  * Nwrite * Remote Address        Description
---- ------ ---- -------- -------- --------------------- ------------------------------
   0 Log       0       0        0                        stdin
   1 Log       0       0        0                        stdout
   2 Log       0       0        0                        stderr
   3 Log       0       0        0                        /usr/local/squid/var/logs/cache.log
   6 Socket    0     603      353  .0                    DNS Socket
   7 File      0       0     8828                        /usr/local/squid/var/logs/access.log
   8 Pipe      0       0        0                        unlinkd -> squid
   9 File      0       0     2607                        /usr/local/squid/var/logs/store.log
  10 File      0       0      104                        /usr/local/squid/var/cache/swap.state
  11 Pipe      0       0        0                        squid -> unlinkd
  12 Socket 1440      70        0* 10.0.0.60.38093       Reading next request
  13 Socket    0       0        0  .0                    HTTP Socket
  17 Socket    0    2667*   44096  10.0.0.10.2531        Waiting for next request

vmhost:/usr/local/squid/bin # netstat -anp |grep squid
tcp        0      0 10.0.0.60:3128          0.0.0.0:*               LISTEN      8552/squid
udp        0      0 0.0.0.0:34838           0.0.0.0:*                           8552/squid
unix  2      [ ]         DGRAM                    393925789 8552/squid


Anyway, despite the missing port numbers:
  cache_object://... is squidclient getting the list itself
  that leaves only DNS and HTTP listener TCP/UDP Sockets
  and the two unlinkd pipes (listed as unix by netstat).

So it does appear to be DNS.

Squid will drop any packets received from NS not listed either in dns_nameservers in squid.conf, or in resolv.conf as your local ones.

so, let me repeat:
squid is opening an extra upd socket for ICP,HTCP, syslog and DNS.
udp_incoming_address and udp_outgoing_address are relevant config params for this.

we can`t get rid of this port because we would break DNS for squid.


I got the bit about syslog being involved wrong. But the rest is correct.

#udp_incoming_address    is used for the ICP socket receiving packets
#                               from other caches.

So this is just half of the truth because it is relevant not only for ICP, but for DNS, too , correct ?
should "we" fix this in the docs ? (unfortunately, i cannot give much input)


Thats OK. I've kicked the process off already in squid-dev. Its just a meter of whether its a doc-only or deep code fix.

btw - any reason why squid doesn`t use host resolver routines for DNS lookup ?
(i.e. something like gethostbyname() etc, so this would also get cached by nscd ....)

Squid can't do that internally as it blocks the whole app on each lookup.
You can compile with --disable-internal-dns. That builds a fast external helper that calls gethostbyname() for squid and passes the results back without blocking other requests.


Amos

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