[Libguestfs] [v2v PATCH 1/2] rhv-upload: Validate UUIDs passed to -oo rhv-disk-uuid (RHBZ#1789279)

[Richard W.M. Jones]

On Thu, Jan 23, 2020 at 11:12:22PM +0100, Martin Kletzander wrote:
> The validation helps us fail early and with a sensible error message.  The NIL
> UUID is not valid for oVirt, but other than that there is no other logic in
> there merely because the UUID types are a matter of the generator and they are
> just forwarded in this partucular case.
> 
> Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
> ---
>  v2v/output_rhv_upload.ml | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/v2v/output_rhv_upload.ml b/v2v/output_rhv_upload.ml
> index 14153db36897..923ef56d4ca5 100644
> --- a/v2v/output_rhv_upload.ml
> +++ b/v2v/output_rhv_upload.ml
> @@ -49,6 +49,14 @@ after their uploads (if you do, you must supply one for each disk):
>    -oo rhv-disk-uuid=UUID          Disk UUID
>  ")
>  
> +let is_nonnil_uuid uuid =
> +  let nil_uuid = "00000000-0000-0000-0000-000000000000" in
> +  let hex = "[a-fA-F0-9]" in
> +  let rex_uuid = "^"^hex^"{8}-"^hex^"{4}-"^hex^"{4}-"^hex^"{4}-"^hex^"{12}$" in

Use sprintf?

> +  let rex_uuid = PCRE.compile rex_uuid in
> +  if uuid = nil_uuid then false
> +  else PCRE.matches rex_uuid uuid

This could compile the regexp only once if you write this function as:

  let is_nonnil_uuid =
    let nil_uuid = "00000000-0000-0000-0000-000000000000" in
    let hex = "[a-fA-F0-9]" in
    let rex_uuid = sprintf "^%s{8}...." etc... in
    let rex_uuid = PCRE.compile rex_uuid in
    function uuid ->
      if uuid = nil_uuid then false
      else PCRE.matches rex_uuid uuid

Or even better if you lazily evaluate the regexp so it is
only compiled once when the function is first called:

  let is_nonnil_uuid =
    let rex_uuid = lazy (
      let nil_uuid = "00000000-0000-0000-0000-000000000000" in
      let hex = "[a-fA-F0-9]" in
      let rex_uuid = sprintf "^%s{8}...." ... in
      PCRE.compile rex_uuid
    ) in
    function uuid ->
      if uuid = nil_uuid then false
      else PCRE.matches (Lazy.force rex_uuid) uuid

But basically the idea is fine so ACK.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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