[libvirt] [PATCH v2] conf: virDomainDefValidateInternal prohibit some characters in shmem name

[skobyda at redhat.com]

On Fri, 2018-07-27 at 13:19 -0400, John Ferlan wrote:
> You shouldn't drop libvir-list when you reply...
Sorry, I dropped it by mistake.
> 
> On 07/27/2018 06:35 AM, skobyda at redhat.com wrote:
> > On Mon, 2018-07-23 at 17:32 -0400, John Ferlan wrote:
> > > 
> > > On 07/12/2018 09:10 AM, Simon Kobyda wrote:
> > > > XML shmem name will not include character '/', and will not be
> > > > equal to strings
> > > > "." or "..", as shmem name is used in a path.
> > > 
> > > Validate that the provided XML shmem name is not directory
> > > specific
> > > "."
> > > or ".." names as well as ensuring that there is no path separator
> > > '/'
> > > in
> > > the name.
> > > > https://bugzilla.redhat.com/show_bug.cgi?id=1192400
> > > > ---
> > > > 
> > > > Changes in V2 
> > > > 	- Added error reports
> > > > 	- Error situation will happen only if shmem name is
> > > > equal to
> > > > 	  "." or "..", however their occurence in a name
> > > > compromised of
> > > > more
> > > >           characters is allowed.
> > > > 
> > > >  src/conf/domain_conf.c | 22 ++++++++++++++++++++++
> > > >  1 file changed, 22 insertions(+)
> > > > 
> > > 
> > > I believe this actually belongs in
> > > virDomainDeviceDefValidateInternal
> > > for case VIR_DOMAIN_DEVICE_SHMEM.
> > > Also, should the docs/schemas/domaincommon.rng be modified?
> > > Currently
> > > it
> > > has:
> > > 
> > >   <define name="shmem">
> > >     <element name="shmem">
> > >       <attribute name="name">
> > >         <data type="string">
> > >           <param name="pattern">[^/]*</param>
> > >         </data>
> > > 
> > 
> > Is it a good idea? To create such regular expression, I believe it
> > would make it unreadable for another person, ergo useless. I don't
> > want
> > it to end up as IPv6. I've benn told that actual parser can be, and
> > sometimes is stricter than scheme.
> > 
> 
> Well this is what I was hoping others would be able to chime in on.
> Hence why you ask on list. I don't disagree that being stricter in
> Parse
> is fine.  Doing regexes is like reading a foreign language to me at
> times. Some just don't make sense.

Yeah, that's why I don't want to try to insert complicated regex in
docs/schemas/domaincommon.rng.
> 
> I think that regex is indicating - any character except '/', but I'm
> not
> sure. If it is, it's ironic that we have to check for '/'
> specifically
> since it shouldn't be passing the xml validation test - OK at least
> if
> one was editing via virsh.
> 
> John
> 
You are right about what that regex does. But from what I heard, that
functionality is rather new to libvirt, so users have option to bypass
that verification. So I would like to also leave it in code in case
users try to bypass that regex verification.

Simon.

> > > Consider how other names are limited in their scope. The
> > > basictypes.rng
> > > has a number of examples.
> > > 
> > > Naturally, the problem with changing it is that someone somewhere
> > > will
> > > complain, but libvirt used to accept this other format. Right now
> > > I
> > > would think the scope a bit too broad.
> > 
> > But then we cannot fix most of the bugs, since there could always
> > be
> > some user which relies on bug behavior.
> > > 
> > > If we are to limit the name we should also document in
> > > docs/formatdomain.html.in that the shmem name is "limited" in
> > > name to
> > > avoid the '/' character, ".", and "..".
> > > 
> > > BTW: My regex isn't that good, but it would seem '/' is an
> > > invalid
> > > character by XML standards even though the code never checked for
> > > it.
> > > Using virt-xml-validate <file> <schema> would "validate" whether
> > > someone
> > > provides valid XML.
> > > 
> > > 
> > > John
> > > 
> > > > diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> > > > index 7ab2953d83..6b34c17de4 100644
> > > > --- a/src/conf/domain_conf.c
> > > > +++ b/src/conf/domain_conf.c
> > > > @@ -6107,6 +6107,8 @@ virDomainDefLifecycleActionValidate(const
> > > > virDomainDef *def)
> > > >  static int
> > > >  virDomainDefValidateInternal(const virDomainDef *def)
> > > >  {
> > > > +    size_t i;
> > > > +
> > > >      if (virDomainDefCheckDuplicateDiskInfo(def) < 0)
> > > >          return -1;
> > > >  
> > > > @@ -6136,6 +6138,26 @@ virDomainDefValidateInternal(const
> > > > virDomainDef *def)
> > > >          return -1;
> > > >      }
> > > >  
> > > > +    for (i = 0; i < def->nshmems; i++) {
> > > > +        if (strchr(def->shmems[i]->name, '/')) {
> > > > +            virReportError(VIR_ERR_XML_ERROR, "%s",
> > > > +                           _("shmem name cannot include '/'
> > > > character"));
> > > > +            return -1;
> > > > +        }
> > > > +
> > > > +        if (STREQ(def->shmems[i]->name, ".")) {
> > > > +            virReportError(VIR_ERR_XML_ERROR, "%s",
> > > > +                           _("shmem name cannot be equal to
> > > > '.'"));
> > > > +            return -1;
> > > > +        }
> > > > +
> > > > +        if (STREQ(def->shmems[i]->name, "..")) {
> > > > +            virReportError(VIR_ERR_XML_ERROR, "%s",
> > > > +                           _("shmem name cannot be equal to
> > > > '..'"));
> > > > +            return -1;
> > > > +        }
> > > > +    }
> > > > +
> > > >      if (virDomainDefLifecycleActionValidate(def) < 0)
> > > >          return -1;
> > > >  
> > > >