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Date:      Wed, 14 Mar 2001 21:17:16 +0100
From:      Poul-Henning Kamp <phk@critter.freebsd.dk>
To:        Adrian Chadd <adrian@freebsd.org>
Cc:        freebsd-arch@freebsd.org
Subject:   Re: [PATCH] add a SITE MD5 command to ftpd 
Message-ID:  <36424.984601036@critter>
In-Reply-To: Your message of "Wed, 14 Mar 2001 21:07:58 %2B0100." <20010314210758.A2405@roaming.cacheboy.net> 

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>So, you can't trust that the returned filename, size, mtime or md5
>are "real".

Heck, you can't even trust that you are talking to the server you
think you are talking to.

The point here is not to solve all problems in the world, the point
here is to improve a common case enough to make life simpler for
the majority of us.

You will notice that my proposal was
	SITE MD5 filename [offset [length]]

If you are paranoid you issue two MD5 commands:

	SITE MD5 somesoftware.tgz

gets you the entire files MD5, which is easy to fake.  Next you
select a random piece of the file and ask for the MD5 of that
bit:
	SITE MD5 somesoftware.tgz  383273  283744

Now, unless the other end has the actual file, or a very large
database of potential MD5's for that file, they will not be able
to answer your question correctly...

Hows that...


--
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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