[libvirt PATCH] remote: Avoid crash in remoteSplitURIScheme()

[Daniel P. Berrangé]

On Fri, Dec 10, 2021 at 05:47:41AM -0800, Andrea Bolognani wrote:
> On Fri, Dec 10, 2021 at 11:31:19AM +0100, Peter Krempa wrote:
> > On Fri, Dec 10, 2021 at 10:59:27 +0100, Andrea Bolognani wrote:
> > > @@ -69,7 +69,15 @@ remoteSplitURIScheme(virURI *uri,
> > >                       char **driver,
> > >                       remoteDriverTransport *transport)
> > >  {
> > > -    char *p = strchr(uri->scheme, '+');
> > > +    char *p = NULL;
> > > +
> > > +    if (!uri->scheme) {
> > > +        virReportError(VIR_ERR_INVALID_ARG, "%s",
> > > +                       _("missing scheme for URI"));
> >
> > The other place which leads to the call of this helper (virConnectOpenInternal)
> > uses the following error to reject the uri if scheme is missing:
> >
> > virReportError(VIR_ERR_NO_CONNECT,
> >                _("URI '%s' does not include a driver name"),
> >                name);
> 
> Yeah, it seems safer to catch the issue inside the helper than
> requiring the callers to perform the check ahead of time. It's okay
> for virConnectOpen() to have a nicer error message, as it's the one
> that people are more likely to see.

Yes, this is something I simply overlooked when refactoring
the code. The check should clearly be in this common helper.

> I entertained the thought of adding the check to virURIParse()
> directly, because I can't think of a scenario where having a NULL
> scheme would be considered valid. But that seemed like a change that
> had the potential to break unrelated stuff, so I cowardly decided to
> go with the safe version instead O:-)

We've supported URIs without a scheme in the past. IIRC, we allowed
a bath path to a UNIX socket for the original Xen driver. That
code is deleted now of course.

Regards,
Daniel
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