Re: [PATCH 05/16] hw/uefi: add var-service-core.c

[Gerd Hoffmann]

  Hi,

> - in general, we should filter out surrogate code points, for any use.
> any UCS2 string from the guest that contains a surrogate code point
> should be considered invalid, and the request should be rejected based
> just on that.

Something like this?

edk2 seems to be inconsistent with strings, sometimes they are expected
to include a terminating '\0' char (most of the time), sometimes not
(in variable policies for example).

gboolean uefi_str_is_valid(const uint16_t *str, size_t len,
                           gboolean must_be_null_terminated)
{
    size_t pos = 0;

    for (;;) {
        if (pos == len) {
            if (must_be_null_terminated) {
                return false;
            } else {
                return true;
            }
        }
        switch (str[pos]) {
        case 0:
            /* end of string */
            return true;
            ;;
        case 0xd800 ... 0xdfff:
            /* outlaw surrogates */
            return false;
        default:
            /* char is good, check next */
            break;
        }
        pos++;
    }
}

take care,
  Gerd