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Re: [Issue 2486] New - Svnserve 1.3 authz: writing on subfolder requires read access on repository root

From: David Anderson <david.anderson_at_calixo.net>
Date: 2006-01-24 09:54:39 CET

Ben Collins-Sussman wrote:
>>A check in the code, and a short discussion with David Anderson on irc learned that:
>>- svnserve requires read access to the repository root for commits.
>>- this behaviour is by design.
>>- mod_authz_svn doesn't have this behaviour, making both implementations of the
>>same authz model incompatible
> Before jumping into a patch, I'd like to understand *why* there are
> these two different behaviors in our servers.
> David Anderson: why is the new behavior intentional?

It is intentional because, lacking any execution cap in authz, it made sense to
me to require read access for traversing the repository prior to writing to it.
 How can someone write to a path which he couldn't actually read? Now of
course, in the light of this bug, I realize that this point of view is flawed.

I had asked at the time of modifying the commit editor about this ("Should the
commit editor require read access to the root?"), and was told that yes, the
commit editor should enforce this. I won't play pass the buck, as this problem
is likely ascribable to my relatively short experience with both authz and svn
editors when I wrote that change in.

I think that the difference here is that I took 'r' to mean 'rx', whereas
mod_authz_svn takes 'x' for granted and means 'r' litterally. In the former
case, svnserve's behaviour is valid; in the latter case, mod_authz_svn's
behaviour is valid.

So, my take on all this is that svnserve's implementation is indeed faulty, as
it was supposed to copy mod_authz_svn's implementation. The solution is to
either correct svnserve (I believe the fix is a two-liner - remove read access
check on opening directories in the commit editor), or introduce an 'x' bit that
explicitely identifies the right to traverse directories.

- Dave.

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Received on Tue Jan 24 09:56:42 2006

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