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Date: Sun, 18 Sep 2016 23:44:04 -0400
From: Jeff Cody <jcody@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v8 10/12] uuid: Tighten uuid parse
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To: Fam Zheng <famz@redhat.com>
Cc: qemu-devel@nongnu.org, kwolf@redhat.com, qemu-block@nongnu.org, sw@weilnetz.de, mdroth@linux.vnet.ibm.com, armbru@redhat.com, pbonzini@redhat.com, mreitz@redhat.com, rth@twiddle.net

On Sun, Sep 18, 2016 at 12:25:30PM +0800, Fam Zheng wrote:
> sscanf is relatively loose (tolerate) on some invalid formats that we
> should fail instead of generating a wrong uuid structure, like with
> whitespaces and short strings.
> 
> Add and use a helper function to first check the format.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  util/uuid.c | 24 +++++++++++++++++++++++-
>  1 file changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/util/uuid.c b/util/uuid.c
> index 4701903..dd6b5fd 100644
> --- a/util/uuid.c
> +++ b/util/uuid.c
> @@ -61,12 +61,34 @@ char *qemu_uuid_unparse_strdup(const QemuUUID *uuid)
>                             uu[13], uu[14], uu[15]);
>  }
>  
> +static bool qemu_uuid_is_valid(const char *str)
> +{
> +    int i;
> +
> +    for (i = 0; i < strlen(str); i++) {
> +        const char c = str[i];
> +        if (i == 8 || i == 13 || i == 18 || i == 23) {
> +            if (str[i] != '-') {
> +                return false;
> +            }
> +        } else {
> +            if ((c >= '0' && c <= '9') ||
> +                (c >= 'A' && c <= 'F') ||
> +                (c >= 'a' && c <= 'f')) {
> +                continue;
> +            }
> +            return false;
> +        }
> +    }
> +    return i == 36;
> +}
> +

Doesn't verify variant / version, but it is a lot better than what was
before.

Reviewed-by: Jeff Cody <jcody@redhat.com>


>  int qemu_uuid_parse(const char *str, QemuUUID *uuid)
>  {
>      unsigned char *uu = &uuid->data[0];
>      int ret;
>  
> -    if (strlen(str) != 36) {
> +    if (!qemu_uuid_is_valid(str)) {
>          return -1;
>      }
>  
> -- 
> 2.7.4
> 
>