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Date: Thu, 19 Oct 2017 20:32:55 +0000
From: Robert Watson <>
Subject: Re: CVE-2017-8805: Unsafe symlinks not filtered in
 Debian mirror script ftpsync

Scripts depend on the underlying functionality of the various utilities
like rsync that they call. I'm having trouble understanding how a script
could ever be deserving of a CVE. Maybe I'm wrong. I wish to be educated.

We are overwhelmed with more vulnerabilities than can be fixed quickly

Are "just to be safer" type things really a wise use of our resources?

Does a proliferation of a large number of low-caliber problems make
monitoring these lists more trouble than it's worth? Does it cause
high-impact problems to be lost amongst low-impact ones?

On Thu, Oct 19, 2017, 15:46 Seth Arnold <> wrote:

> On Wed, Oct 18, 2017 at 04:55:07PM -0400, Robert Watson wrote:
> > Removing the ability for rsync to copy symlinks pointing to targets
> outside
> > the mirror tree would greatly cripple it. I need to understand how the
> > danger is worth the loss of this functionality.
> Note that the fix isn't modifying rsync, the fix is modifying the ftpsync
> script that calls rsync:
> +    RSYNC_OPTIONS=${RSYNC_OPTIONS:-"-prltvHSB8192 --safe-links --timeout
> 3600 --stats --no-human-readable"}
> Of course for people who run this mirroring tool as a specific user
> account and set file permissions appropriately this is more or less a
> no-op. But this is a useful hardening for people who run the ftpsync
> command as a user with too many privileges. (I wouldn't have bothered
> filing for a CVE for this change; I see it as a simple hardening change.)
> This option shouldn't cripple ftpsync as a well-run repository is highly
> unlikely to have symlinks pointing out of the tree. A repository with
> symlinks pointing out of the tree is already not a suitable rsync source.
> Thanks

Robert "DocSalvager" Watson
... trust in truth keeps hope alive

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