Re: [PATCH] Fix heavily broken relative URI resolution

[Alexander Larsson <alexl redhat com>]

On Sun, 2006-03-19 at 17:06 +0100, Christian Neumair wrote:
> Am Sonntag, den 19.03.2006, 13:09 +0100 schrieb Christian Neumair:
> > The attached patch implements the relative URI resolution as suggested
> > by RFC 2396 and RFC 3986. The old algorithm was quite hosed, for
> > instance when the relative reference had too many ".." components, which
> > overwrote the authority component of an URI.
> > "ftp://server/foo";, "../../../" would be resolved to some garbage like
> > "ftp:///";.
> > 
> > After applying this patch, test-uri passes all URI relative resolution
> > tests in RFC 3986.

I'm a bit worried by this patch. It rewrites some pretty core parts of
gnome-vfs, and it mentions RFCs a lot. gnome-vfs uris are not really the
same as web uris, for instance # is used for uri-chaining, not
fragments, so things like:

if (*scheme == NULL) /* only relative references may have fragments! */
	f = strchr (p, '#');

look wrong. For instance ftp://ftp.gnome.org/pub/baa.zip#zip:///README
is a valid gnome-vfs uri.

I worry that there are other gnome-vfs specific details in uri handling
that can accidentally get broken with this change...

Does this fix any important issues in practice, or is it more of a
cleanness fix?

> > I'm not sure why the old code was laid out that way, but somebody
> > probably didn't separate relative URI resolution and symblic link
> > resolution, which are two completely different things. The latter is for
> > instance implemented in my sftp method patch, and could be used by other
> > methods as well. One notable difference is that trailing slashes will be
> > preserved in the RFC's algorithm. I'm not sure how desireable this is
> > for directories, for instance /home/foo where foo is a symlink to "..",
> > this would be resolved to /home/ with the RFC algorithm, and to /home
> > with the symlink algorithm, I'm not sure who should handle the
> > canonicalization, i.e. ensure that get_file_info for /home/ will work
> > if /home is a symlink.
> > 
> > There is quite a similarity between _gnome_vfs_canonicalize_pathname and
> > remove_dot_segments, however I couldn't figure out the details because I
> > don't find _gnome_vfs_canonicalize_pathname particularly traceable.
> > 
> > I don't know WHY many modules and applications use
> > gnome_vfs_uri_resolve_relative, they usually shouldn't have to mess
> > around with this and instead use a symlink resolution helper - maybe
> > because the old docs claim it has something to do with relative path
> > resolution, which is only right to a point where the relative URI only
> > forms a path with segments that exclusively contain unreserved
> > characters.

Yeah, we should be using a specific symlink resolver in some places
instead of resolve_relative.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 Alexander Larsson                                            Red Hat, Inc 
                   alexl redhat com    alla lysator liu se 
He's an all-American dishevelled vagrant from a doomed world. She's a 
manipulative winged schoolgirl married to the Mob. They fight crime!