Date: Thu, 16 Sep 2010 14:49:05 -0500 From: "David DeSimone" <fox@verio.net> To: "Tom Judge" <tom@tomjudge.com> Cc: freebsd-net@freebsd.org, bz@freebsd.org Subject: Re: Strange FreeBSD behavior when trying to forward beetween ipsec crypted gif's. May be a problem with ICMP unreach packets at all Message-ID: <20100916194905.GR4928@verio.net> In-Reply-To: <4C9232F9.70206@tomjudge.com> References: <273436110.20100916180053@gmail.com> <4C9232F9.70206@tomjudge.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Tom Judge <tom@tomjudge.com> wrote: > > > Question: Why FW2 does not send ICMP need-fragment-but-DF-set > > message to HostB ? > > If you take a look at icmp_error() in sys/netinet/ip_icmp.c you will > see that icmp errors are not sent for packets that have been > previously been decrypted by IPSec. I have a feeling that this is > because icmp_reflect() will not use the correct output path but I may > be and most probably am wrong. Bjoern (CC'd) can probably shed more > light on it. It is not done because the resulting ICMP packets may very well end up being sent to an unrelated host or router which has no SA policy defined, meaning that the ICMP would be sent unencrypted. This would expose some packet data in the payload of the ICMP message that had been previously sent as securely encrypted, giving an attacker some known-plaintext data to use in attempting to guess session keys, among other information exposed. -- David DeSimone == Network Admin == fox@verio.net "I don't like spinach, and I'm glad I don't, because if I liked it I'd eat it, and I just hate it." -- Clarence Darrow This email message is intended for the use of the person to whom it has been sent, and may contain information that is confidential or legally protected. If you are not the intended recipient or have received this message in error, you are not authorized to copy, distribute, or otherwise use this message or its attachments. Please notify the sender immediately by return e-mail and permanently delete this message and any attachments. Verio, Inc. makes no warranty that this email is error or virus free. Thank you.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20100916194905.GR4928>