o Fixed host discovery probe matching when looking at the returned TCP data in
an ICMP error message. This could lead to incorrectly discarded responses
and the debugging error message: "Bogus trynum or sequence number in ICMP
error message" [Kris]
Fyodor was getting the error message "Got ICMP error with a TCP header that was
too short" while scanning, and looked at the code to see a comment I made about
requiring 12 bytes of TCP data in an ICMP error message instead of the minimum
RFC requirement of 8 bytes.
I made this comment and requirement because tcp_trynum_pingseq_decode() was
being called on the TCP data, and was using the ACK field (which is just past
the 8 byte range). However, upon further inspection, we came to the conclusion
that this code was broken because examining the ACK field should only be done
on a TCP response, not on our own probe (which is what we're looking at in the
ICMP data).
This assumes that -g is used (the only reason that the SEQ/ACK is checked since
the source port number is used otherwise), but the code is also broken without
it because the *_decode() function checks the destination port number rather
than the source port (which should be checked since it's our own probe we're
looking at).
So I've removed the 12-byte requirement and pingseq checking calls, and just
check that the received SEQ number matches the probe SEQ number.
Should we just work with the SEQ/ACK matching when using TCP and leave the
pingseq/trynum port number encoding to UDP? This means behavior won't change
with the use of -g, and it should be guaranteed to be there since we'll only
be looking at whole TCP headers rather than any smaller chunks. Plus, the SEQ
number is already getting encoded with the pingseq/trynum info, we're just not
decoding the ACK responses unless -g is used.
recorded. This applies during a TCP connect scan, where we have a count of
packets sent but not of bytes (which we cannot measure, and will vary from
platform to platform).
-Raw TCP (not SYN to an open port)
-ICMP information queries (echo request, timestamp request, netmask req)
-ARP
-Raw TCP (SYN to an open port)
-UDP, IP protocol, or other ICMP
-TCP connect
-Anything else
The order used to be
-ARP
-Raw TCP (not SYN to an open port)
-UDP, IP protocol, or ICMP
-Raw TCP (SYN to an open port)
-TCP connect
-Anything else
o Nsock now supports binding to a local address and setting IPv4 options
with nsi_set_localaddr() and nsi_set_ipoptions(), respectively. [Kris]
o Nmap's Nsock-utilizing subsystems (DNS, NSE, version detection) have been
updated to support the -S and --ip-options flags. [Kris]
