Security improvements:
- Increase the size of each syncookie secret from 32 to 128 bits
in order to make brute force attacks on the secrets much more
difficult.
- Always return the lowest order dword from the MD5 hash; this
allows us to expose 2 more bits of the cookie and makes ACK
floods which seek to guess the cookie value more difficult.
Performance improvements:
- Increase the lifetime of each syncookie from 4 seconds to 16
seconds. This increases the usefulness of syncookies during
an attack.
- From Yahoo!: Reduce the number of calls to MD5Update; this
results in a ~17% increase in cookie generation time here.
Reviewed by: hsu, jayanth, jlemon, nectar
MFC After: 15 seconds
initialized until after a syncookie was generated. As a result,
all connections resulting from a returned cookie would end up using
a MSS of ~512 bytes. Now larger packets will be used where possible.
MFC after: 5 days
associated with the syncache entry: in case tcp_close() has been
called on the corresponding listening socket, the lock has been
destroyed as a side effect of in_pcbdetach(), causing a panic when
we attempt to lock on it.
Reviewed by: hsu
configuration stuff as well as conditional code in the IPv4 and IPv6
areas. Everything is conditional on FAST_IPSEC which is mutually
exclusive with IPSEC (KAME IPsec implmentation).
As noted previously, don't use FAST_IPSEC with INET6 at the moment.
Reviewed by: KAME, rwatson
Approved by: silence
Supported by: Vernier Networks
o instead of a list of mbufs use a list of m_tag structures a la openbsd
o for netgraph et. al. extend the stock openbsd m_tag to include a 32-bit
ABI/module number cookie
o for openbsd compatibility define a well-known cookie MTAG_ABI_COMPAT and
use this in defining openbsd-compatible m_tag_find and m_tag_get routines
o rewrite KAME use of aux mbufs in terms of packet tags
o eliminate the most heavily used aux mbufs by adding an additional struct
inpcb parameter to ip_output and ip6_output to allow the IPsec code to
locate the security policy to apply to outbound packets
o bump __FreeBSD_version so code can be conditionalized
o fixup ipfilter's call to ip_output based on __FreeBSD_version
Reviewed by: julian, luigi (silent), -arch, -net, darren
Approved by: julian, silence from everyone else
Obtained from: openbsd (mostly)
MFC after: 1 month
kernel access control.
Instrument the TCP socket code for packet generation and delivery:
label outgoing mbufs with the label of the socket, and check socket and
mbuf labels before permitting delivery to a socket. Assign labels
to newly accepted connections when the syncache/cookie code has done
its business. Also set peer labels as convenient. Currently,
MAC policies cannot influence the PCB matching algorithm, so cannot
implement polyinstantiation. Note that there is at least one case
where a PCB is not available due to the TCP packet not being associated
with any socket, so we don't label in that case, but need to handle
it in a special manner.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
syncache_respond(A), ip_output(), ip_input(), tcp_input(), syncache_badack(B)
Which winds up deleting a different entry from the syncache. Handle
this by not utilizing the next entry in the timer chain until after
syncache_respond() completes. The case of A == B should not be possible.
Problem found by: Don Bowman <don@sandvine.com>
Ensure that the syn cache's syn-ack packets contain the same
ip_tos, ip_ttl, and DF bits as all other tcp packets.
PR: 39141
MFC after: 2 weeks
This time, make sure that ipv4 specific code (aka all of the above)
is only run in the ipv4 case.
results in the syncache entry being turned into a socket. While it's
not used in the main tree, this is required in the MAC tree so that
labels can be propagated from the mbuf to the socket. This is also
useful if you're doing things like transparent IP connection hijacking
and you want to use the syncache/cookie mechanism, but we won't go
there.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
this is a low-functionality change that changes the kernel to access the main
thread of a process via the linked list of threads rather than
assuming that it is embedded in the process. It IS still embeded there
but remove all teh code that assumes that in preparation for the next commit
which will actually move it out.
Reviewed by: peter@freebsd.org, gallatin@cs.duke.edu, benno rice,
All TCP ISNs that are sent out are valid cookies, which allows entries
in the syncache to be dropped and still have the ACK accepted later.
As all entries pass through the syncache, there is no sudden switchover
from cache -> cookies when the cache is full; instead, syncache entries
simply have a reduced lifetime. More details may be found in the
"Resisting DoS attacks with a SYN cache" paper in the Usenix BSDCon 2002
conference proceedings.
Sponsored by: DARPA, NAI Labs
receiver was not sending an immediate ack with delayed acks turned on
when the input buffer is drained, preventing the transmitter from
restarting immediately.
Propogate the TCP_NODELAY option to accept()ed sockets. (Helps tbench and
is a good idea anyway).
Some cleanup. Identify additonal issues in comments.
MFC after: 1 day
to be followed by nfsnodehashtbl, so bzeroing callouts beyond the end of
tcp_syncache soon caused a null pointer panic when nfsnodehashtbl was
accessed.
