[Libguestfs] [PATCH] v2v: -i vmx: Refuse to load a disk image by accident.

[Pino Toscano]

On Wednesday, 11 October 2017 15:25:26 CEST Richard W.M. Jones wrote:
> If you accidentally point -i vmx at a disk image, it will try to load
> the whole thing into memory and crash.  Catch this narrow case and
> print an error.
> 
> However don't fail if ‘file’ is not installed or if we don't know what
> the file is.
> ---
>  v2v/parse_vmx.ml | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/v2v/parse_vmx.ml b/v2v/parse_vmx.ml
> index 65d5a0edd..f6c34e2cf 100644
> --- a/v2v/parse_vmx.ml
> +++ b/v2v/parse_vmx.ml
> @@ -268,6 +268,18 @@ let remove_vmx_escapes str =
>  
>  (* Parsing. *)
>  let rec parse_file vmx_filename =
> +  (* One person pointed -i vmx at the VMDK file, resulting in an out
> +   * of memory error.  Avoid this narrow case.
> +   *)
> +  let () =
> +    let cmd = sprintf "file -b %s ||:" (quote vmx_filename) in
> +    let out = external_command cmd in
> +    match out with
> +    | line :: _ when String.find line "disk image" >= 0 ->
> +       error (f_"-i vmx: %s: this may be a disk image.  You must specify the .vmx file only on the command line.")
> +             vmx_filename
> +    | _ -> () in
> +
>    (* Read the whole file as a list of lines. *)
>    let str = read_whole_file vmx_filename in
>    if verbose () then eprintf "VMX file:\n%s\n" str;

Hm I'm not sure about this, since we don't do this for other parameters
(e.g. the XML for -i libvirtxml).

Anyway, if a check is deemed needed, my suggestion is to use what Cédric
wrote in its virt-builder-repository implementation:

+let get_mime_type filepath =
+  let file_cmd = "file --mime-type --brief " ^ (quote filepath) in
+  match external_command file_cmd with
+  | [] -> None
+  | line :: _ -> Some line

... using Std_utils.which to check for the presence of `file`,
returning None if not available.

-- 
Pino Toscano
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: This is a digitally signed message part.
URL: <http://listman.redhat.com/archives/libguestfs/attachments/20171011/d644dd3f/attachment.sig>