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From "William A. Rowe, Jr." <>
Subject Re: general/7865: %2F in PATH_INFO
Date Thu, 14 Jun 2001 15:27:55 GMT
From: "Bill Stoddard" <>
Sent: Thursday, June 14, 2001 9:41 AM

> I have had reports of this being a problem as well (last week in fact :-)  here is Ken
> Coar's analysis:
> <ken>
> The analysis:
> If possible, it would be nice if this check were deferred until
> the determination of the path, path-info, and query-string was
> made, and then applied only to the path.  However, I think that
> may be a significant undertaking, and may not even be possible
> in Apache 1.3.  I will look into it next week, however.
> </ken>
> My first take is that this is a reasonable request. We'll probably look at doing a custom
> build for Apache 1.3 for our internal customer if it does not significantly risk breaking
> other parts of the server.  We'll post whatever we come up with.

For 1.3?  I had rewritten [hope I haven't pitched it] the directory_walk 1.3 logic.  I threw
it at the security list as an example, but the number of apr-like functions required really
discouraged me from submitting the change to the list.  [Of course, we found the quick-fix
for the security hole instead.]  For 2.0, it might actually be a little harder, since the
patch I'm preparing parses from the start, not the tail [so we skip all the not-found stats.]

There is actually a 'set' of these reserved characters that are disallowed in encoding, not
simply %2f, that should be examined.

The simple way is to search for %2[Ff] in the get_path_info call, and backspace over the 
segment (as if it were not found.)  One risk, if /test/foo%2fbar is given, and /test/ is a
directory, we need to fail.  And it is possible this opens security holes, not in Apache's
own core, but in CGIs or some modules.

But there is a bigger problem.  %2f is neither a path seperator, nor the characters %, 2,
It's a unique beast.  You can't later process it, since %252f is also %, 2, f.  Almost needs
it's own unique character value :-)  %252f might even be a legitimate workaround for Robin.


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