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Re: [libvirt] [PATCH] Generate RFC4122 compliant UUIDs




----- Original Message -----
> On Mon, Apr 08, 2013 at 12:35:40PM -0400, Milos Vyletel wrote:
> > Even though http://libvirt.org/formatdomain.html#elementsMetadata
> > states that it requires RFC4122 compliance UUIDs that are generated
> > by virUUIDGenerate() are not. Neither does virUUIDIsValid() check
> > for RFC4122 compliance. Following patch modifies virUUIDGenerate()
> > to generate valid UUIDs and adds check to virUUIDIsValid() to validate
> > UUIDs.
> > 
> > Signed-off-by: Milos Vyletel <milos vyletel sde cz>
> > ---
> >  src/util/viruuid.c |   31 +++++++++++++++++++++++++++++++
> >  1 files changed, 31 insertions(+), 0 deletions(-)
> > 
> > diff --git a/src/util/viruuid.c b/src/util/viruuid.c
> > index 7250543..2dc9a56 100644
> > --- a/src/util/viruuid.c
> > +++ b/src/util/viruuid.c
> > @@ -114,6 +114,25 @@ virUUIDGenerate(unsigned char *uuid)
> >          err = virUUIDGeneratePseudoRandomBytes(uuid, VIR_UUID_BUFLEN);
> >      }
> >  
> > +    /*
> > +     * Make UUID RFC 4122 compliant. Following form will be used:
> > +     *
> > +     * xxxxxxxx-xxxx-Axxx-Bxxx-xxxxxxxxxxxx
> > +     *
> > +     * where
> > +     * A is version defined in 4.1.3 of RFC
> > +     *  Msb0  Msb1  Msb2  Msb3   Version  Description
> > +     *   0     1     0     0        4     The randomly or pseudo-
> > +     *                                    randomly generated version
> > +     *                                    specified in this document.
> > +     *
> > +     * B is variant defined in 4.1.1 of RFC
> > +     *  Msb0  Msb1  Msb2  Description
> > +     *   1     0     x    The variant specified in this document.
> > +     */
> > +    uuid[6] = (uuid[6] & 0x0F) | (4 << 4);
> > +    uuid[8] = (uuid[8] & 0x3F) | (2 << 6);
> > +
> >      return err;
> >  }
> 
> ACK to this bit of the patch

Thanks.

> 
> >  
> > @@ -209,6 +228,7 @@ virUUIDFormat(const unsigned char *uuid, char *uuidstr)
> >   * Do some basic tests to check whether the given UUID is
> >   * valid as a host UUID.
> >   * Basic tests:
> > + *  - Validate RFC4122 compliance
> >   *  - Not all of the digits may be equal
> >   */
> >  int
> > @@ -216,10 +236,21 @@ virUUIDIsValid(unsigned char *uuid)
> >  {
> >      unsigned int i, ctr = 1;
> >      unsigned char c;
> > +    unsigned char version;
> > +    unsigned char variant;
> >  
> >      if (!uuid)
> >          return 0;
> >  
> > +    /*
> > +     * RFC4122 defines version 1 to 5 (section 4.1.3)
> > +     * RFC4122 defined variant is desribed in section 4.1.1
> > +     */
> > +    version = (uuid[6] >> 4);
> > +    variant = (uuid[8] >> 6);
> > +    if (!(version > 0 && version <= 5) || variant != 2)
> > +        return 0;
> > +
> >      c = uuid[0];
> >  
> >      for (i = 1; i < VIR_UUID_BUFLEN; i++)
> 
> but NACk to this part
> 
> What you're checking here is just one possible valid scheme for UUIDs.
> We shouldn't reject UUIDs just because they use a different scheme than
> the one we do.
> 

Fair enough. I've noticed shortly after I've sent the mail that it's only
used to verify hosts UUID and does not validate user defined UUIDs for
guests. Let me remove these changed and resend patch with only first part.

Thanks,
Milos


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